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[Display omitted] • The removal efficiencies of ofloxacin and Cu2+ were 91.23% and 72.09%. • Bridging, precipitation, and complexation effects were the main co-adsorption mechanisms. • O 2 - and h+ were the main free radicals for ofloxacin removal. • The intermediate product of ofloxacin did not produce oxidative stress response to zebrafish. The combined contamination of antibiotics and heavy metals usually occurs in aquaculture wastewater and has high ecological toxicity. Currently, most research only focuses on the removal of a single heavy metal or antibiotics, and there is little research on the simultaneous removal of both. Therefore, to effectively treat them, this study prepared TiO 2 -loaded phosphogypsum-modified biochar (TYBC450) for adsorption and photocatalytic removal of ofloxacin (OFL) and copper (Cu2+). The removal performance and mechanisms of OFL and Cu2+ were explored, and their ecological toxicity was assessed through zebrafish acute toxicity experiments. The results suggested a synergistic effect between OFL and Cu2+. The adsorption efficiencies of TYBC450 for OFL and Cu2+ were 88.16% and 90.87% (the adsorption capacities were 1.75 and 3.65 mg/g, respectively). Bridging, precipitation, and complexation effects were the main co-adsorption mechanisms. The photocatalytic efficiencies of OFL and Cu2+ were 91.23% and 72.09% (the rate constants were 0.0101 and 0.0045 min-1, respectively). OFL acted as a hole-trapping agent, while Cu2+ acted as an electron acceptor, hindering the combination of e- and h+. There were 12 intermediates in the OFL degradation process, which had lower toxicity than the mother organism. Both the cyclic regeneration and actual aquaculture wastewater application tests indicated that TYBC450 had potential application prospects. [ABSTRACT FROM AUTHOR]

Industrialization has contributed significantly to the advancement and sustenance of human civilization. However, it has also posed serious challenges to environmental sustainability, notably through heavy metal pollution, which has severely impacted ecological systems. Recent studies have explored the use of biochar for the removal of heavy metals from aqueous solutions. This review underscores the diverse physicochemical and structural characteristics of biochar, derived from various biomass sources through different pyrolysis processes, and their varying adsorption efficiencies. The review aims to investigate current biochar production technologies, their unique properties, and their maximum removal efficiency and adsorption capacity for heavy metals. The primary adsorption mechanisms, adsorption isotherms, and kinetic models have been identified. Furthermore, the study confirms that optimal conditions—such as the choice of precursors, pyrolysis temperature, and an understanding of the advantages and limitations—are crucial for designing biochar with superior structural and physicochemical properties. This review provides an updated overview of biochar-based heavy metal treatment in aquatic systems, highlighting existing research gaps and suggesting future research directions. [Display omitted] • Efficiency of different biochars for water management was systematically reviewed. • Advantages and limitation of biochars production was discussed. • The engineered biochars has excellent structural and physiochemical properties. • The kinetics of the biochars-based system is well described by Pseudo second order. • More attention should be paid to biochar production and application at large scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • The porous PBC PB was successfully synthesized by one-step KHCO 3 -activated pyrolysis. • The PBC PB has excellent passivation performance with a high S BET of 1342.07 m2/g. • PBC PB could significantly reduce the bioavailability and bioaccumulation of Pb/Cd. • Precipitation, complexation and cation-π interaction convert Pb/Cd to stable species. The porous biochar (PBC PB) was prepared by one-step KHCO 3 -activated pyrolysis of corn stalks, which showed excellent passivation properties for Pb/Cd in soil (48.99 % or 46.74 %). Characterization results revealed that the PBC PB possessed a dense and network-like pore structure with a huge specific surface area of 1342.07 m2/g, which was conducive to the passivation of Pb/Cd. Batch experiments showed that PBC PB had excellent adsorption properties with the maximum absorption capacity of 117.61/48.24 mg/g. After 30 d of remediation, the bioavailable-Pb/Cd contents in 5.0 % of PBC PB treatment were reduced by 47.06 % and 58.42 %, respectively. The speciation transformation results uncovered that the contents of unstable Pb/Cd components gradually decreased with the increase of PBC PB dosages, ultimately transforming into stable residual components. In addition, the PBC PB could effectively increase the contents of soil available nutrients and enhance functional enzyme activities, which contributed to promoting the growth of cucumber seedlings. Meanwhile, PBC PB strongly alleviated the oxidative damage of Pb/Cd to cucumber seedlings by significantly reducing the Pb/Cd accumulation and antioxidant oxidase activity of cucumber seedlings. Furthermore, precipitation, complexation, as well as cation-π interaction were the primary passivation mechanisms of PBC PB for Pb/Cd. Overall, the study provided a reasonable design of porous carbon-based materials for the remediation of Pb/Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

Microalgae can be collected in large quantities and hold significant potential for environmental remediation, offering a cost-effective solution. This study explores the use of Spirulina platensis (SP) as feedstock for biochar production. SP contains abundant nitrogen-rich components, such as proteins, which can serve as nitrogen sources. We prepared SP-derived biochar through pyrolysis for the adsorption of Pb and Zn from aqueous solutions and used it as an amending agent to remediate heavy metal-contaminated agricultural soil. Pyrolysis of proteins in SP introduces nitrogen-functional groups, resulting in nitrogen-doped biochar. We investigated the surface chemical behavior of thermally treated SP using X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Surface analysis revealed the presence of pyridine-N and pyrrole-N from protein pyrolysis products. The study also demonstrated that these functional groups affect interactions with heavy metals. Batch experiments examined the effects of pH and initial concentration on the adsorption of Pb and Zn using SP400 and SP600. Both types of biochar showed satisfactory performance in adsorbing Pb and Zn. The effect of SP400 and SP600 on the removal of Pb and Zn through the physicochemical properties and surface functional groups was investigated. Analysis of SP400 and SP600 highlighted that electrostatic interactions, cation exchange, complexation, and mineral precipitation contributed to Pb and Zn adsorption. The study concludes that SP-derived biochar, particularly SP600, is effective for immobilizing Pb and Zn in contaminated agricultural soil, with SP600 showing superior performance. [Display omitted] • Spirulina platensis (SP) can be effectively converted into biochar, which has proven successful for removing Pb and Zn. • SP-derived biochar exhibits strong alkaline properties and diverse functional groups, leading to a high adsorption capacity for Pb and Zn. • SP derived biochar effectiveness was studied for treating heavy metal-contaminated soil. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low lignin content in algae makes thermochemical conversion to chars cost-effective. • Slow pyrolysis and HTC are preferred methods for algal char production. • Higher porosity and more diverse functional groups boost algal sorbent properties. • Enriched ash content in algal chars leads to higher cation exchange properties. • Modification of algal char enhances biosorbent properties. Biochar and hydrochar are carbon-rich solid products of algal and terrestrial biomass obtained through various thermochemical processes, mainly hydrothermal liquefaction, pyrolysis, and hydrothermal carbonization. Both are regarded as economical, potent, and environmentally friendly adsorbents for wastewater remediation. The versatile applicability of biochar and hydrochar, which is due to their enhanced surface physicochemical properties, includes efficient metal biosorption, soil fertility enhancement, and carbon sequestration. Consequently, there has been an increase in research for producing and exploiting biochar and hydrochar from algae. Both micro- and macro-algal biomass have strong potential due to their sustainability footprint and distinct properties. This review focuses on a comprehensive account of the synthesis of algal biochar and hydrochar and use in wastewater treatment to develop innovative solutions for efficient mitigation of several aqueous pollutants and heavy metal ions. The review discusses the various thermochemical production routes, biophysical characterization techniques, and modes of mechanism for wastewater bioremediation. Algal-based biochar and hydrochar are reported to have higher porosity and more diverse functional groups such as amines, hydroxyl, and carboxyl compared to their cellulosic and waste-derived counterparts, demonstrating an increased wastewater remediation efficiency. In addition, presence of inorganic metal including sodium, potassium, magnesium, and phosphorus in algal chars facilitates the formation of mesopores and graphite structures, improving their cation exchange capacity. Moreover, algal chars may exhibit pH buffering capacity, which could help stabilize the pH during wastewater treatment processes. Notably, the low O/C content of algal hydrochars enhances the binding and removal of organic pollutants including toxic dyes and antibiotics. The review highlights the development of modified algal chars to enhance the porosity, surface area, structural integrity, and adsorption capacity enabling a higher bioremediation potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • CWs filled with combined organic media were developed for effective AMD treatment. • Abiotic and biotic treatment performances declined with decreasing pH. • High acidity (pH 2.0) caused failure of multiple pathways for AMD treatment. • Growth of functional microbes for AMD bioremediation was inhibited at low pH. • SRB and organic degrading bacteria were keystone taxa for AMD treatment. The impact of influent pH value (2.0–5.0) on remediation performance of constructed wetlands (CWs) packed with composite organic solids consisting of walnut shells, biochar and plastic filters for acid mine drainage (AMD) was evaluated in this study. Reed straw broth was supplemented to drive the microbial remediation process. Influent pH had a notable impact on both abiotic and biotic remediation performance, with very low efficacy at pH 2.0 and the best performance achieved at pH 5.0. The adsorption capacity of CW substrates for heavy metals and the growth of functional microbes for AMD treatment were restrained at high acidity. Moreover, the removal of conventional pollutants, plant growth and metal deposition in the CWs were negatively impacted by the dosing of AMD with low pH. A low pH of 2.0 resulted in a distinctive microbial community in the CWs with almost no sulfate-reducing bacteria (SRB). In other CW systems, SRB (Desulfosporosinus and Desulfobulbus) and organic degrading bacteria (Cellulomonas and Geobacter) were identified as keystone taxa to carry out AMD bioremediation synergistically in phase Ⅱ. CWs filled with composite organic substrates are promising systems for AMD treatment, but the pH of AMD should be preneutralized to ≥ 3. [ABSTRACT FROM AUTHOR]

Biochar application emerges as a promising and sustainable solution for the remediation of soils contaminated with potentially toxic metal (loid)s (PTMs), yet its potential to reduce PTM accumulation in crops remains to be fully elucidated. In our study, a hierarchical meta-analysis based on 276 research articles was conducted to quantify the effects of biochar application on crop growth and PTM accumulation. Meanwhile, a machine learning approach was developed to identify the major contributing features. Our findings revealed that biochar application significantly enhanced crop growth, and reduced PTM concentrations in crop tissues, showing a decrease trend of grains (36.1%, 33.6–38.6%) > shoots (31.1%, 29.3–32.8%) > roots (27.5%, 25.7–29.2%). Furthermore, biochar modifications were found to amplify its remediation potential in PTM-contaminated soils. Biochar application was observed to provide favorable conditions for reducing PTM uptake by crops, primarily through decreasing available PTM concentrations and improving overall soil quality. Employing machine learning techniques, we identified biochar properties, such as surface area and C content as a key factor in decreasing PTM bioavailability in soil-crop systems. Furthermore, our study indicated that biochar application could reduce probabilistic health risks associated with of the presence of PTMs in crop grains, thereby contributing to human health protection. These findings highlighted the essential role of biochar in remediating PTM-contaminated lands and offered guidelines for enhancing safe crop production. [Display omitted] • Our study reveals the significant potential of biochar in promoting safe crop production. • Modifications intensify the capacity of biochar to reduce PTM accumulation in crops. • Biochar decreased soil available PTM concentration, and improved overall soil quality. • Our work identifies the contributing features for enhanced the remediation efficiency. [ABSTRACT FROM AUTHOR]

The simultaneous removal of anionic and cationic heavy metals presents a challenge for adsorbents. In this study, acetate (Ac-) was utilized as the intercalating anion for layered double hydroxide (LDH) to prepare a novel biochar composite adsorbent (Ac-LB) designed for the adsorption of Pb(II), Cu(II), and As(V). By utilizing Ac- as the intercalating anion, the interlayer space of the LDH was enlarged from 0.803 nm to 0.869 nm, exposing more adsorption sites for the LDH and enhancing the affinity for heavy metals. The results of the adsorption experiments showed that the adsorption effect of Ac-LB on heavy metals was significantly improved compared to the original FeMg-LDH modified biochar composites (LB), and the maximum adsorption capacity of Pb(II), Cu(II), and As(V) were 402.70, 68.50, and 21.68 mg/g, respectively. Wastewater simulation tests further confirmed the promising application of Ac-LB for heavy metal adsorption. The analysis of the adsorption mechanism revealed that surface complexation, electrostatic adsorption, and chemical deposition were the main mechanisms of action between heavy metals (Pb(II) and Cu(II)) and Ac-LB. Additionally, Cu(II) ions underwent a homogeneous substitution reaction with Ac-LB. The adsorption process of As(V) by Ac-LB mainly relied on complexation and ion-exchange reactions. Lastly, the modification of the LDH structure by Ac− as an intercalating anion, thereby increasing the affinity for heavy metals, was further illustrated using density-functional theory (DFT) calculations. [Display omitted] • Preparation of a composite with acetate as LDH intercalation ion. • Acetate as intercalating ion improved the adsorption capacity of the FeMg-LDH. • The mechanism of heavy metal adsorption was discussed. • The experimental results were verified by DFT calculation. [ABSTRACT FROM AUTHOR]

• Biochar derived from low-lignin biomass is highly susceptible to oxidation. • Aged low-lignin biochar releases significant DOM, decreasing soil As stability. • Oxygen-functional groups on aged biochar enhance Pb, Zn, and Cu stability. • Cu stability with biochar aging requires further research. Understanding biochar aging is a critical factor in predicting its long-term effects when added to soil. This study explores the complex links between lignin content in biochar feedstock and biochar stability during accelerated aging, including its influence on heavy metal mobility in soil. In this study, nine types of biochar based on fir (F), pine (P), and oak (O) sawdust were produced at 400 °C, and lignin was extracted from them using ammonia after 0, 3, and 7 days (named as 0FB, 3FB, 7FB, 0PB, 3PB, 7PB, 0OB, 3OB, and 7OB). Subsequently, each biochar was subjected to 25 cycles of wet-dry (WD) and freeze–thaw (FT) aging. The aged low-lignin biochars (7FB, 7 PB, and 7OB) released more dissolved organic matter (DOM) and contained more oxygen-containing surface groups on their surfaces than the high-lignin biochars (0FB, 0PB, and 0OB). The low-lignin biochars with high DOM leaching released 37–85 % more anionic arsenic (As) from biochar-amended soil after 25 cycles of aging than the high-lignin biochars. The stabilities of lead (Pb), zinc (Zn), and copper (Cu) were increased due to strong binding to surface functional groups on the low-lignin biochar. The acid-soluble fractions of Pb, Zn, and Cu were converted to organic-bound fractions as biochar aging progressed, with the degree of transformation being inversely proportional to the lignin content of biochar. This research highlights the crucial role of lignin in shaping biochar stability, and reveals how biochar stability impacts soil heavy metals speciation, opening new avenues for effective biochar-based environmental solutions and the promotion of soil health. [ABSTRACT FROM AUTHOR]

The aim of the present study was to find environmentally friendly solutions for the disposal of problematic and toxic textile sludge (TS) by producing textile sludge biochar (TSB) by pyrolysis and evaluating its chemical properties, polycyclic aromatic hydrocarbon (PAH) content, heavy metals (HMs) speciation, environmental risks, and effects on seed germination. Pyrolysis of TS at temperatures ranging from 300 to 700 °C significantly reduced (85–95%) or eliminated certain PAHs in the biochar, enriched heavy metal content within land use limits, and increased bioavailability of HMs in biochar produced at 300 °C and decreased leaching capacity of HMs in biochar produced at 700 °C. The speciation of HMs and their bioavailability during pyrolysis processes was strongly temperature dependent, with lower temperatures increasing the toxic and bioavailable forms of Zn and Ni, while higher temperatures converted the bioavailable Ni to a more stable form, while Cu, Cr, and Pb were transformed from stable to toxic and bioavailable forms. The ecological risk index (RI) values of TSB-300 and TSB-700 are below the threshold value of 150, indicating a low-risk level, and the risk level decreases at temperatures above 500 °C. Further, the extracts of TSB-300 and TSB-700 had the highest percentage of germinating seeds, while the extracts of TS and TSB-500 inhibited seed germination by 20–30% compared to the control. These results indicate that pyrolysis effectively reduces PAHs and binds leachable HMs in biochar, however, the specific pyrolysis temperature influences metal speciation, bioavailability, seed germination, and environmental risk. [Display omitted] • Disposal of TS containing HMs poses a high environmental risk. • PAHs are reduced significantly by pyrolysis of TS into biochar. • Higher temperatures produce biochar with a stable form of Ni. • Environmental risk index of 700 °C biochar was the lowest. • Extracts of biochar produced at 700 °C promote plant growth. [ABSTRACT FROM AUTHOR]

Heavy metal contamination poses a significant threat to soil quality, plant growth, and food safety, and directly affects multiple UN SDGs. Addressing this issue and offering a remediation solution are vital for human health. One effective approach for immobilizing heavy metals involves impregnating cypress chips with calcium hydroxide (Ca(OH) 2) to enhance the chemical adsorption capacity of the resulting woody charcoal. In the present study, un-treated cypress biochar (UCBC) and calcium-treated cypress biochar (TCBC), were introduced into pristine and contaminated soil, at rates of 3, 6, and 9% (w/w). Both BCs were alkaline (UCBC pH: 8.9, TCBC pH: 9.7) with high specific surface area, which improved the soil properties (pH, EC, and OM). Radish (Raphanus sativus) cultivated in pots revealed that both UCBC and TCBC demonstrated significant improvements in growth attributes and heavy metal immobilization compared to the control, with TCBC exhibiting superior effects. The TCBC surface showed highly active nanosized precipitated calcium carbonate particles that were active in immobilizing heavy metals. The application of TCBC at a rate of 9% resulted in a substantial reduction in Zn and Cu uptake by radish roots and shoots. In contaminated soil, Zn uptake by radish roots decreased by 55% (68.3–31.0 mg kg−1), and shoots by 37% (49.3–31.0 mg kg−1); Cu uptake decreased by 40% (38.6–23.2 mg kg−1) in roots and 39% (58.2–35.2 mg kg−1) in shoots. Uptake of Pb was undetectable after TCBC application. Principal component analysis (PCA) highlighted the potential of TCBC over UCBC in reducing heavy metal concentrations and promoting radish growth. Future research should consider the long-term effects and microbial interactions of TCBC application. [Display omitted] • To immobilize Zn, Cu, and Pb in soil, a novel biochar (TCBC) was prepared. • TCBC improved soil properties and radish growth attributes. • TCBC resulted in a substantial reduction in Zn, Cu, and Pb in radish roots and shoots. • Highly active nano-sized CaCO 3 particles in TCBC-immobilized heavy metals. • TCBC consistently outperformed UCBC in terms of immobilization properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Column studies achieved 24.9 and 24.6 mg/g of adsorption capacities for Pb(II) and Cd(II) • The fixed bed mode attained 24 and 24.3 mg/g of adsorption capacity for Red198 and Blue29. • The Thomas model exhibited a strong correlation with the experimental data. • The Adams-Bohart model effectively described the initial phase of the C e /C 0 < 0.1. • After the 1st regeneration, 97% recovery of target pollutants was attained. • An increasing bed depth extended the operational lifespan of the column study. The adsorption behavior of Cd(II) and Pb(II) ions in a coexisting environment, alongside with both dyes (Reactive Red198 and Blue29) was systematically investigated by using a continuous fixed-bed column completely packed with Rosa damascena waste biosorbent (RDWB). Artificial neural network (ANN) model was also utilized to predict the performance of RDWB for various inputs. Their column performance was assessed by optimizing parameters such as bed depth, influent flow rate, and biosorbents' concentration. It was found that an increasing bed depth considerably extended the operational lifespan and decrease in flow rate delays the column adsorption. Its adsorption capacities were 24.9, 24.6, 24.0 and 24.3 mg/g for Pb(II), Cd(II), Red198, and Blue29, respectively. The RDWB also had a higher adsorption capacity, as compared to previously used biosorbents such as chitosan and biochars due to its good thermal stability and high surface area of 421.46 m2/g. The adsorption of target pollutants took place through ion exchange and electrostatic interactions with negatively charged functional groups on the adsorbent's surface. The experimental data were fitted by various column adsorption models such as the Thomas, Yoon-Nelson, and Adams-Bohart. The findings showed that the Thomas model exhibited a strong correlation with the experimental data. In contrast, the Adams-Bohart model was applicable to the initial phase of the breakthrough curve (C e / C 0 ≤ 0.1). For industrial applications, a scale up model was also presented with the cost analysis of the biosorbent. The comparison of predicted values with experimental percentage (%) removal values of target pollutants by the RDWB indicated the excellent performance of the ANN model for this work. [ABSTRACT FROM AUTHOR]

While traditional biochar demonstrates promising performance in diverse settings, its efficacy may be constrained under specific conditions of high acidity and heavy metal concentrations. In this study, researchers developed a new polysilicon-aluminum alkali mineral-enhanced biochar composite material, GBMSs (green biochar-metakaolin-sodium silicate), by pyrolyzing fibers from dragon fruit peels and blending them with metakaolin and sodium silicate. Using a response surface methodology, this environmentally friendly composite material was optimized for removing copper and zinc contaminants across a range of initial pH levels from 2 to 6. Experimental findings indicated that the adsorption capacity of GBMSs for copper and zinc was significantly enhanced, ranging from 1.5 to 4 times greater compared to pure biochar or biochar mixed solely with a silicon-aluminum mineral. Various analytical techniques including scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were utilized to examine the influence of poly-silica-aluminum alkali minerals (GBMSs) on biochar composites. The findings revealed an upsurge in surface binding locations and oxygen-related functional groups because of integrating GBMSs. This augmentation of electronegative features on the biochar surface was credited to the development of stabilizing silica-aluminum connections, ultimately boosting its adsorption effectiveness in acidic surroundings. By applying Langmuir and Freundlich models, it was deduced that the adsorption of GBMSs adheres to a multilayer uniform adsorption mechanism, with surface ion interchange and complexation restricting the adsorption capability. This research highlights the potential of clay mineral-altered biochar in efficiently dealing with intricate environmental contamination. [ABSTRACT FROM AUTHOR]

Steel mill wastewater sludge, as an iron-enriched solid waste, was expected to be converted into iron-enriched biochar with acceptable environmental risk by pyrolysis. The purpose of our study was to evaluate the chemical speciation transformation of heavy metals in biochar under various pyrolysis temperatures and its reutilization for tetracycline (TC) removal. The experimental data indicated that pyrolysis temperature was a key factor affecting the heavy metals speciation and bioavailability in biochar, and biochar with pyrolysis temperature at 450 °C was the most feasible for reutilization without potential risk. The endogenous iron-enriched biochar (FSB450) showed highly efficient adsorption towards TC, and its maximum adsorption capacity could reach 240.38 mg g−1, which should be attributed to its excellent mesoporous structure, abundant functional groups and endogenous iron cycling. The endogenous iron was converted to a stable iron oxide crystalline phase (Fe 3 O 4 and MgFe 2 O 4) by pyrolysis, which underwent a valence transition to form a coordination complex with TC by electron shuttling in the FSB450 matrix. The study provides a win-win approach for resource utilization of steel wastewater sludge and treatment of antibiotic contamination in wastewater. [Display omitted] • Steel mill wastewater sludge could be converted into endogenous iron-enriched biochar. • 450 °C is the optimum temperature for heavy metals stabilization without potential risk. • The endogenous iron effectively enhanced the removal efficiency of tetracycline. • The maximum adsorption capacity for tetracycline could reach 240.38 mg g−1. • The complexation, π-π interaction and hydrogen bonding are involved in the sorption. [ABSTRACT FROM AUTHOR]

The safe disposal of sewage sludge (SS) and food waste digestate residues (DR) is a tough issue considering the difficulty of dewatering and the environmental risks from heavy metals and pathogens. This study combined hydrothermal pretreatment (HP), anaerobic digestion (AD), and pyrolysis to synergistically dispose of SS and DR to enhance dewaterability, recover energy, and prepare biochar with heavy metal immobilization. The results showed that the solid contents of centrifuged cakes increased after HP at 180 °C of SS with the addition of 25% and 50% mass fractions of DR. The centrate from co-HP had a high chemical oxygen demand (COD) and was further treated by AD at 37 °C, producing 193.75 and 210.39 mL/g COD input (25 °C and 1 atm) of cumulative CH 4 under the addition of 50% and 75% mass fractions of DR, respectively. The methanogenic types in AD converted from hydrogen utilization to acetic acid utilization with increasing DR ratio. Zn, Cu, Ni, and Pb were primarily left in the biochar after 50% mass fraction of DR was mixed in the HP combined with pyrolysis at 700 °C; the chemical fractionation of Zn, Cu, Cr, and Pb in the biochar increased to over 85% of the residual fractions, resulting in the lowest potential ecological risk index (15.22, low risk). The CH 4 produced from the AD of the co-HP centrate (50: 50, w / w) can supply heat for the HP process, reducing the energy input by 89%. This co-disposal strategy can effectively recover carbon resources from solid wastes to reduce carbon emissions. • HP, AD coupled with pyrolysis were used for synergistic treatment of SS and DR. • The dewaterability of SS improved after HP with the addition of DR. • The generated CH 4 can supply heat for the HP, reducing the energy input by 89%. • The biochar had a low heavy metal risk after HP combined with pyrolysis. [ABSTRACT FROM AUTHOR]

In this comprehensive study, highlights emerging environmentally friendly methods to eliminating hazardous heavy metals from contaminated water, with an emphasis on bioremediation and biosorption. Breakthroughs, such as the combination of biological remediation and nanotechnology to improve the elimination of metals effectiveness and the use of genetically modified microbes for targeted pollutant breakdown. Developing biosorption materials made from agricultural waste and biochar, this indicates interesting areas for future research and emphasizes the necessity of sustainable practices in tackling heavy metal contamination in water systems. There seems to be a surge in enthusiasm for the utilization of biological remediation and biosorption methods as sustainable and viable options for eliminating heavy metals from contaminated water in the past couple of decades. The present review intends to offer an in-depth review of the latest understanding and advances in the discipline of biological remediation methods like bioaccumulation, biofiltration, bio-slurping, and bio-venting. Biosorption is specifically explained and includes waste biomass as biosorbent with the removal mechanisms and the hindrances caused in the process are detailed. Advances in biosorption like microbes as biosorbents and the mechanism involved in it. Additionally, novel enhancement techniques like immobilization, genetic modification, and ultrasound-assisted treatment in microbial sorbent are clarified. However, the review extended with analyzing the future advances in the overall biological methods and consequences of heavy metal pollution. [Display omitted] • Biological techniques for the effective removal of heavy metal ions were discussed. • Various biosorbents sources, mechanism and influencing parameters were summarized. • Microbes surface qualities are modified using genetic modifications are reviewed. • Future and advanced views on biological adsorption techniques were elucidated. [ABSTRACT FROM AUTHOR]

Carbon-based biowaste incorporated with inorganic oxides as a composite is an enticing option to mitigate heavy metal pollution in water resources due to its more economical and efficient performance. With this in mind, we constructed manganese-doped iron oxide microflowers resembling the dandelion-like structure on the surface of cold plasma-treated carbonized rice husk (MnFe 2 O 3 /PCRH). The prepared composite exhibited 45% and 19% higher removal rates for Cu2+ and Cd2+, respectively than the pristine CRH. The MnFe 2 O 3 /PCRH composite was characterized using XRD, FTIR, FESEM, EDX, HR-TEM, XPS, BET, TGA, and zeta potential, while the adsorption capacities were investigated as a function of pH, time, and initial concentration in batch trials. As for the kinetics, the pseudo-second-order was the rate-limiting over the pseudo-first-order and Elovich model, demonstrating that the chemisorption process governed the adsorption of Cu2+ and Cd2+. Additionally, the maximum adsorption capacities of the MnFe 2 O 3 /PCRH were found to be 122.8 and 102.5 mg/g for Cu2+ and Cd2+, respectively. Based on thorough examinations by FESEM-EDS, FTIR, and XPS, the possible mechanisms for the adsorption can be ascribed to surface complexation by oxygen-containing groups, a dissolution-precipitation of the ions with –OH groups, electrostatic attraction between metal ions and the adsorbent's partially charged surface, coordination of Cu2+ and Cd2+ with π electrons by aromatic/graphitic carbon in the MnFe 2 O 3 /PCRH, and pore filling and diffusion. Lastly, the adsorption efficiencies were maintained at about 70% of its initial adsorption even after five adsorption-desorption cycles, displaying its remarkable stability and reusability. [Display omitted] • Mn-doped Fe 2 O 3 microflowers were decorated on plasma-treated biochar (MnFe 2 O 3 /PCRH). • The MnFe 2 O 3 /PCRH was thoroughly analyzed before and after Cu2+ and Cd2+ adsorption. • Kinetics, isotherms, and thermodynamic studies showed its excellent adsorption capability. • Mechanisms underlying ions adsorption by MnFe 2 O 3 /PCRH were further clarified. • The reusability of the MnFe2O3/PCRH proved its economic sustainability. [ABSTRACT FROM AUTHOR]

Toxicity induced by heavy metals deteriorates soil fertility status. It also adversely affects the growth and yield of crops. These heavy metals become part of the food chain when crops are cultivated in areas where heavy metals are beyond threshold limits. Cadmium (Cd) and nickel (Ni) are considered the most notorious ones among different heavy metals. The high water solubility of Cd made it a potential toxin for plants and their consumers. Accumulation of Ni in plants, leaves, and fruits also deteriorates their quality and causes cancer in humans when such a Ni-contaminated diet is used regularly. Both Cd and Ni also compete with essential nutrients of plants, making the fertility status of soil poor. To overcome this problem, the use of activated carbon biochar can play a milestone role. In the recent past application of activated carbon biochar is gaining more and more attention. Biochar sorb the Cd and Ni and releases essential micronutrients that are part of its structure. Many micropores and high cation exchange capacity make it the most acceptable organic amendment to improve soil fertility and immobilize Cd and Ni. In addition to improving water and nutrients, soil better microbial proliferation enhances the soil rhizosphere ecosystem and nutrient cycling. This review has covered Cd and Ni harmful effects on crop yield and their immobilization by activated carbon biochar. The focus was made to elaborate on the positive effects of biochar on crop yield and soil health. [ABSTRACT FROM AUTHOR]

[Display omitted] Biochar utilization for adsorption seems to be the most cost-effective, easy/fast approach for pollutants removal from water and wastewater. Due to the high adsorption properties, magnetic biochar proved to be efficient in the sorption of heavy metals and nutrients. Although there are several studies on development of magnetic biochars, there is a lack of research on development of high-performance magnetic biochar from food waste for removal applications. This study aimed at preparing new classes of magnetic biochar derived from tea waste (TBC) for removal of heavy metals (Ni2+, Co2+), and nutrients (NH 4 + and PO 4 3−) from water and effective fertilizer (source of NH 4 + and PO 4 3−). Standard carbonization process and ultrafast microwave have been used for fabrication of TBCs. The removal of nickel, cobalt as the representatives of heavy metals, and over-enriched nutrients (NH 4 + and PO 4 3−) from water were tested and the removal kinetics, mechanism, and the effect of pH, dissolved organic matter and ionic strength were studied. Simultaneously, possible fertilizing effect of TBC for controlled release of nutrients (NH 4 + and PO 4 3−) in soil was investigated. Up to 147.84 mg g−1 of Ni2+ and 160.00 mg g−1 of Co2+ were adsorbed onto tested biochars. The process of co-adsorption was also efficient (at least 131.68 mg g−1 of Co2+ and 160.00 mg g−1 of Ni2+). The highest adsorbed amount of NH 4 + was 49.43 mg g−1, and the highest amount of PO 4 3− was 112.61 mg g−1. The increase of the solution ionic strength and the presence of natural organic matter affected both the amount of adsorbed Ni2++Co2+ and the reaction mechanism. The results revealed that magnetic nanoparticle impregnated onto tea biochar, can be a very promising alternative for wastewater treatment especially considering removal of heavy metals and nutrients and slow-release fertilizer to improve the composition of soil elements. [ABSTRACT FROM AUTHOR]

This study focused on preparation and characterization of two activated SiO 2 @C nanocomposites from rice-husk waste material through a controlled method. Both of them contain different percentages of silica and carbon. After chemical and thermal activations of the prepared composites, high energy ball milling was utilized to prepare nano powders. The percent of silica in the prepared nanocomposites was determined by HF method. Moreover, their chemical compositions were determined by XRF technique. The prepared materials were also examined by x-ray diffraction technique, FT-Infrared, scanning electron microscope, high resolution transmission electron microscope, Zeta Sizer, and Surface-Area-Analyzer. The prepared SiO 2 @C nanocomposite that contains higher silica percent was selected as adsorbent for removing of Cu, Zn and Pb from aqueous solutions. The effects of pH and contact time on the adsorption process were also studied. The results showed that SiO 2 @C nanocomposites with different percentages of silica and carbon were prepared successfully by the proposed method. The sample that contains higher silica, exhibited smaller particle size (20–50 nm), higher specific surface area (262.39 m2g-1) and higher negative zeta potential (−71 mV). On the other hand, the sample that contains lower silica exhibited higher particle size (20–70 nm), lower specific surface area (42.95 m2g-1), and lower zeta potential (-6 mV). The adsorption efficiencies of prepared SiO 2 @C nanocomposites at pH 6 for removing of Cu, Zn, and Pb from aqueous solutions were 96.5, 97, 9 and 88.66%, respectively. The kinetic study revealed that the adsorption process proceeded by pseudo-second order reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Protein-like substances contributed a lot to heavy metals removal in CWs. • Pyrite oxidation facilitated TP removal via the complexation of ferric hydroxide. • Biochar and pyrite promoted heterotrophic and autotrophic denitrification in CWs. • Functional bacteria related to autotrophic denitrification were enriched by pyrite. Wastewater polluted by heavy metals with low C/N ratio posed a big challenge to constructed wetlands (CWs) for sustainable advanced wastewater purification. In this study, biochar coupled with pyrite was successfully applied in CWs to simultaneously remove organics, total nitrogen (TN), total phosphorus (TP) and heavy metals, with the highest removal efficiency of 95.78%, 98.78%, 96.22% and 99.91%, respectively. Batch tests proved that the complexation of ferric hydroxide from pyrite oxidation played an important role in TP and heavy metals removal. Meanwhile, fluorescence excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) further manifested that protein-like substances contributed a lot to heavy metals stabilization. Moreover, the multiplication of Proteobacteria , Chloroflexi at phylum level and Dechloromonas at genus level, which were capable of heterotrophic or autotrophic nitrate reducing process indicated that the denitrification capacity of CWs was significantly enhanced by biochar and pyrite. This study provided a feasible insight into the application of CWs with biochar and pyrite addition to enhance the treatment of low C/N wastewater. [ABSTRACT FROM AUTHOR]

The presence of heavy metals in water pose a serious threat to both public and environmental health. However, the advances in the application of low cost biochar based adsorbent synthesize from various feedstocks plays an effective role in the of removal heavy metals from water. This study implies the introduction of novel method of converting food waste (FW) to biochar through pyrolysis, examine its physiochemical characteristics, and investigate its adsorption potential for the removal of heavy metals from water. The results revealed that biochar yield decreased from 18.4 % to 14.31 % with increase in pyrolysis temperature from 350 to 550 °C. Likewise, increase in the pyrolysis temperature also resulted in the increase in the ash content from 39.87 % to 42.05 % thus transforming the biochar into alkaline nature (pH 10.17). The structural and chemical compositions of biochar produced at various temperatures (350, 450, and 550 °C) showed a wide range of mineralogical composition, and changes in the concentration of surface functional groups. Similarly, the adsorption potential showed that all the produced biochar effectively removed the selected heavy metals from wastewater. However a slightly high removal capacity was observed for biochar produced at 550 °C that was credited to the alkaline nature, negatively charged biochar active sites due to O-containing functional groups and swelling behavior. The results also showed that the maximum adsorption was recorded at pH 8 at adsorbent dose of 2.5 g L−1 with the contact time of 120 min. To express the adsorption equilibrium, the results were subjected to Langmuir and Freundlich isotherms and correlation coefficient implies that the adsorption process follows the Freundlich adsorption isotherm. The findings of this study suggest the suitability of the novel FW derived biochar as an effective and low cost adsorbent for the removal of heavy metals form wastewater. [Display omitted] • Biochar was successfully produced from food waste at various pyrolysis temperatures. • Temperatures significantly affect the physiochemical characteristics of biochar. • Biochar showed effective adsorption capacity towards the removal of heavy metals. • pH 8, 2.5 g L−1 adsorbent dose and 120 min contact time showed high adsorption. • Adsorption equilibrium fitted best with Freundlich adsorption isotherm model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stability of biochar to Cd, Zn and Pb in soil enhanced after KMnO 4 modification. • Biotoxicity of metals was reduced by 28%-95% at 10% KMnO 4 -modified biochar dose. • Biochar was oxidized and C-O stretching change was prior during freeze–thaw cycles. • Ion exchange and precipitation were mechanisms for MBC to stabilize Cd, Zn and Pb. • KMnO 4 -modified biochar resisted the adverse effects of freeze–thaw cycles in soil. Biochar has been widely used in soil remediation because of its porosity and impressive efficiency. Many studies have demonstrated the good affinity of biochar for heavy metals (HMs), but efficient modification methods to increase the stability of multiple HMs are lacking. Moreover, few studies focus on biochar's potential ability to ageing resistance and changes in its physicochemical properties during freeze–thaw (F/T) cycles. Here, KMnO 4 -modification biochar (MBC) was prepared and the immobilization and anti-freeze performance of MBC on Cd, Zn and Pb in soil were investigated. The addition of 10 % MBC decreased concentrations of toxicity characteristic leaching procedure (TCLP) by 66.80 %, 25.39 % and 99.68 % for Cd, Zn and Pb, respectively, after 28 days, accompanied by a significant decrease in the phytoavailability and bioaccessibility of HMs in soil. Soil fertility was also improved by MBC application. Furthermore, frequent F/T cycles obviously induced the fragmentation of soil particles and enhanced the activity of HMs. Conversely, MBC particles became finer, accompanied by further oxidation and higher alkalinity but degraded pore structures during F/T cycles. The oxidation of lignocellulose and changes in C-O stretching were greatest among all functional groups in biochar. Therefore, MBC could suppress the migration of HMs through precipitation, cohesion of soil particles, and stronger complexation by oxygen-containing functional groups. Moreover, fractions of HMs were also transferred from exchangeable to potentially labile or nonlabile species. Overall, MBC displayed advantages in the stabilization of HMs and showed higher resistance to F/T cycles and promise for long-term remediation of HM-contaminated soils in cold regions. [ABSTRACT FROM AUTHOR]

This study evaluates pyrolysis products obtained from biomasses (silver grass, pine, and acacia) harvested from heavy-metal-contaminated soil. To do so, we utilized two methods: a batch one-stage pyrolysis, and a continuous two-stage pyrolysis. The study results show that the yields and characteristics of bio-oils and biochars varied depending on the pyrolysis process and the type of biomass. The two-stage pyrolysis having two reactors (auger and fluidized bed reactors) appeared to be very suitable for specific chemicals production such as acetic acid, acetol, catechol, and levoglucosan. The biochar obtained from the fluidized-bed reactor of two-stage pyrolysis had high thermal stability, high crystallinity, high inorganic content, and a small number of functional groups. In contrast, the biochar obtained from the one-stage pyrolysis had low thermal stability, low crystallinity, a high carbon content, and a large number of functional groups. The biochar obtained from the two-stage pyrolysis appeared to be suitable as a material for catalyst support and as an adsorbent. The biochar obtained from one-stage pyrolysis appeared to be a suitable as a soil amendment, as an adsorbent, and as a precursor of activated carbon. All biochars showed a negative carbon footprint. In the end, this study, which was conducted using two different processes, was able to obtain the fact that products of pyrolysis biomass contaminated with heavy metals have different characteristics depending on the process characteristics and that their utilization plans are different accordingly. If the optimal utilization method proposed through this study is found, pyrolysis will be able to gain importance as an effective treatment method for biomass contaminated with heavy metals. [Display omitted] • Results of one-stage and two-stage pyrolysis of contaminated biomass were compared. • Two-stage pyrolysis turned out to be suitable for specific chemicals production. • Biochar from fluidized-bed reactor has potential as catalyst support and absorbent. • Biochar from fixed-bed reactor has potential as soil amendment and absorbent. • All biochars seemed to be applicable in construction field as sustainable materials. [ABSTRACT FROM AUTHOR]

The safety and feasibility of directly treating hyperaccumulators with heat is constrained by the substantial presence of volatile heavy metals (HMs) within these plants. The combination of acid pretreatment and heat treatment holds potential for both energy recovery from hyperaccumulators and the transfer of their HMs to specific phases. This study aimed to reveal not only the pyrolysis and gasification kinetics and products of arsenic-hyperaccumulator (Pteris vittate L.) (PV) pretreated with HCl or H 3 PO 4 but also the migration, distribution, and leaching of HMs in products and interaction between HMs and minerals. The HCl-pretreated PV exhibited similar decomposition behaviors and mechanisms to the control PV, with a gradual decrease in overall activation energy (E m). In contrast, H 3 PO 4 changed the behaviors and increased E m. The relative yield of syngas and biochar rose with increased acid concentration. Given the pyrolysis and gasification-induced volatile products released at 550, 750, and 950 °C, HCl increased the relative yield of aromatic compounds and reduced the formation of ring-opening products compared with PV. Compared with HCl, H 3 PO 4 increased the emissions of aromatic compounds and ketone. HCl promoted the loss of HMs, including accelerating their volatilization from the solid phase and increasing their leaching concentration from the biochar. HMs were mostly retained in the H 3 PO 4 -pretreated PV biochar with a low leachable rate, gradually decreasing with the rising temperature. The maximum energetic performance and HM immobilizations were optimized using artificial neural networks. This study revealed plausible reaction pathways and immobilization mechanisms, involving the interactions between minerals and HMs due to Cl or P introduced by the acid pretreatment. Overall, our findings provide new insights into the pyrolysis and gasification behavior of acid-pretreated hyperaccumulator. In particular, the H 3 PO 4 pretreatment not only produced high-yield, high-quality bio-oil products with low HM content but also retained the HMs in the biochar. [Display omitted] • Composition, relative yields, and temperature dependency of volatiles were revealed. • HCl-pretreated PV promoted the HMs volatilization and leaching from solid phase. • H 3 PO 4 -pretreated PV retained most HMs in the biochar with a low leachable rate. • Interactions among HMs, minerals, and acid pretreatment were revealed. • Energetic performance and HM immobilizations were optimized via neural networks. [ABSTRACT FROM AUTHOR]

Upcycling the solid biomass waste into bio-oil and biochar are promising solutions to mitigate environmental pollution caused by solid waste and offer value-added products with tremendous applications, simultaneously. The bio-oil and biochar could be considered as excellent alternatives to the petroleum-based asphalt, however, the application potential of bio-oil and biochar could be compromised, due to the high oxygen content of the bio-oil and presence of heavy metals in the biochar. In this study, biochar modified asphalt (BMA) and biochar modified bio-asphalt (BMBA) were successfully developed using wood waste as feedstock. 16 polycyclic aromatic hydrocarbons (PAHs) and 6 heavy metals were mainly assessed by adsorption characteristics using prepared samples. The major results demonstrates that the concentrations of Cd2+, Cr3+, Cu2+, and Ni2+ elements leached from bio-asphalt was within the acceptable levels (2 mg/L) regarding environmental pollution. And adsorption ability of bio-asphalt was selective and that the ability of BMBA in reducing heavy metals concentration was better than BMA. Major parameters including rainfall time and solar irradiation time could slightly affect the toxicity of PAHs leached from bio-asphalt in the road runoff. Biochar and bio-oil were promising additives for petroleum-based asphalt given its environmental benefits and sustainable properties. [Display omitted] • 16 PAHs and 6 heavy metals leaching toxicity of bio-asphalt are investigated. • The heavy metal adsorption ability of bio-asphalt is selective. • Rainfall time and irradiation time increase PAHs leaching toxicity of bio-asphalt. • Biochar protects asphalt from heavy metal and PAHs pollution. • There are synergistic effects of rainfall and irradiation on heavy metals and PAHs in bio-asphalt leachate. [ABSTRACT FROM AUTHOR]

Biochar has exceeded expectations for immobilizing heavy metals (HMs), but the potential ecological risks of its long-term burial in soil limit its practical application on a large scale. To address this challenge, a novel separable water-hardened magnetic composite biochar sphere (WMBCS) was prepared and applied to remediate agricultural soils contaminated with Cd, Pb, and As. The first application of WMBCS is simultaneously effective in removing Cd (3.2–12.7%), Pb (3.3–13.1%), and As (5.0–25.6%) from soil, and the removal rates are enhanced with increasing soil moisture, application dose and incubation time. WMBCS is more efficient for removing Cd and Pb in mildly contaminated alkaline soils than in heavily contaminated acidic soils. Compared with other regeneration methods, shaking and ultrasound-assisted EDTA-2Na efficiently elutes HMs with a dissolution efficiency of over 75% within 4 h, accompanied by the lowest rate of mass loss (7.6%) and Fe leaching (475.1 mg kg−1). After 5 rounds of successive cyclic remediation, WMBCS exhibits high adsorption efficiency (26.5–30.6% for Cd, 25.4–30.2% for Pb, and 30.2–41.0% for As), magnetic separation efficiency (98.8–99.8%) and regeneration efficiency (92.3–95.4%). The main mechanisms involved in the adsorption and regeneration of WMBCS include ion exchange and chelation. WMBCS is an economical and eco-friendly material with vast unexplored potential for use in agriculture. [Display omitted] • Green adsorbents effectively remove Cd, Pb and As from contaminated soil. • EDTA-2Na is effective for heavy metal desorption and WMBCS regeneration. • Ultrasound assistance could accelerate the WMBCS regeneration. • Regenerated WMBCS exhibits excellent adsorption and magnetic separation capabilities. • WMBCS removes heavy metals and regenerates through physical and chemical effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biochar and agri-waste fight pollution effectively, being eco-friendly. • Study evaluates factors impacting wastewater treatment insights. • Agri-waste is key in pyrolysis, removing pollutants efficiently and cheaply. • NM shows 0-95% efficiency, tackling varied wastewater issues. There is a growing emphasis on harnessing the potential of agricultural waste, biochar, and nanomaterial (NM). This review explores their utilization, highlighting their role in mitigating environmental contamination. Methodology encompasses a comprehensive comparative analysis focusing on patterns discerned within key parameters such as pollutant types, temperature, specific surface, contact times, and pH levels in the study of wastewater treatment. This analysis employs advanced visualization tools like radar, contour, and Q-Q plots to unravel insights into heavy metals and other elements' removal efficiency. This study reveals the effectiveness of agricultural waste, particularly in pyrolysis processes, for removing various pollutants like sulfamethoxazole, phenol, and acid orange 7 along with microstructural analysis. The pH range of 5–8 demonstrates its significance in these removal processes. Furthermore, nanomaterials (NM) exhibit a wide spectrum of removal efficiencies of heavy metal ions and other pollutants, ranging from 0 % to 95 %, over extended treatment durations of up to 2500 min, underlining their potential in diverse wastewater treatment scenarios. The utilization of agricultural waste, biochar, and nanomaterials for environmental remediation strongly corresponds with key UN Sustainable Development Goals, spanning clean water, responsible consumption, climate action, biodiversity preservation, and innovation, showcasing a holistic strategy for sustainable development. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is classified as a heavy metal (HM) and is found into the environment through both natural processes and intensified anthropogenic activities such as industrial operations, mining, disposal of metal-laden waste like batteries, as well as sludge disposal, excessive fertilizer application, and Cd-related product usage. This rising Cd disposal into the environment carries substantial risks to the food chain and human well-being. Inadequate regulatory measures have led to Cd bio-accumulation in plants, which is increasing in an alarming rate and further jeopardizing higher trophic organisms, including humans. In response, an effective Cd decontamination strategy such as phytoremediation emerges as a potent solution, with innovations in nanotechnology like biochar (BC) and nanoparticles (NPs) further augmenting its effectiveness for Cd phytoremediation. BC, derived from biomass pyrolysis, and a variety of NPs, both natural and less toxic, actively engage in Cd removal during phytoremediation, mitigating plant toxicity and associated hazards. This review scrutinizes the application of BC and NPs in Cd phytoremediation, assessing their synergistic mechanism in influencing plant growth, genetic regulations, structural transformations, and phytohormone dynamics. Additionally, the review also underscores the adoption of this sustainable and environmentally friendly strategies for future research in employing BC-NP microaggregates to ameliorate Cd phytoremediation from soil, thereby curbing ecological damage due to Cd toxicity. [Display omitted] • Cd toxicity varies with factors such as metal form, pH, and exposure duration. • Address protocols, impacts, economics, and toxicity in Cd phytoremediation. • Phytoremediation economically mitigates HM pollution, preserving ecosystems. • BC enhances nutrient availability, microbial communities, and Cd adsorption. • BC and NPs synergistically reduce Cd toxicity, improving soil and plant health. [ABSTRACT FROM AUTHOR]

Rapid industrialization and urbanization have resulted in the widespread contamination of soil by potentially toxic metal(loid)s (PTMs). Among these, arsenic (As), cadmium (Cd), chromium (Cr) lead (Pb) and nickel (Ni) are particularly concerning, affecting millions of hectares of arable land globally and posing significant threats to food security and human health. Biochar (BC) has emerged as a promising soil amendment due to its ability to mitigate soil pollution by immobilizing contaminants. But how biochar-linked free radicals affect this process in plants and soil remains murky. Additionally, the mechanism of the geochemical transformation of PTMs in soil-plant systems influenced by biochar-based free radicals is unclear. Here, the influence of free radicals on immobilization, and transformation of PTMs in the soil-plant system under various BC and Comp treatment was investigated. Six treatment groups (1% and 2% biochar, compost, combined application, and control) were randomly assigned to pots in a randomized complete block design (RCBD) to test their effects on maize growth. Results revealed that there was a noticeable rise in the concentration of free radicals in both the BC and Comp treatments compared to the control and the combined application of BC and Comp treatments. The biochar treatment showed a slight reduction in these functional groups, suggesting possible adsorption or sequestration onto the BC surface while the Comp treatment led to an increase in functional groups associated with carbohydrates, proteins, and lipids, indicating enhanced organic matter content. The combined treatment exhibited intermediate effects, suggesting a synergistic interaction between Comp and biochar. X-ray diffraction analysis indicated that the BC did not demonstrate significant alterations in soil mineralogy, suggesting minimal direct effects on mineral dissolution or transformation. Conclusively, biochar-generated free radicals, especially hydroxyl radicals (•OH), play a crucial role in PTMs (i.e., Cd, Cr, Ni, As and Pb) immobilization in soil-plant systems. This study provides novel insights into biochar's mechanisms for mitigating PTMs pollution, paving the way for optimized soil amendment strategies. • BC and Comp influence free radicals generation in the soil-plant system. • BC & Comp treatments affect maize growth influence PTMs availability. • BC-based free radicals play a pivotal role in the geochemical transformation of PTMs. • Reveals distinct effects of BC and Comp amendments on soil functional groups. • BC and Comp demonstrate synergistic effects on FR generation and PTM transformation. [ABSTRACT FROM AUTHOR]

Contamination by potentially toxic metals and metalloids (PTMs) has become a significant health and environmental issue worldwide. Sorption has emerged as one of the most prominent strategies for remediating both soil and water contamination. New sorbents are being developed to provide economically viable and environmentally sound alternatives, in alignment with the principles of the Sustainable Development Goals. This research aimed to assess the potential effects on human health and environmental toxicity following the sorption of cadmium (Cd), lead (Pb), and zinc (Zn) using peat, compost, and biochar as sorbents. The peat was collected in Brazil, a country with a tropical climate, while the compost and biochar were produced from the organic fraction of municipal solid waste (OFMSW). In terms of bioaccessibility, the results showed the following order: compost < biochar < peat for Pb, and compost < peat < biochar for Cd and Zn. There was a significant growth inhibition for Eruca sativa and Zea mays exposed to increasing concentrations of PTMs treated with peat and compost. The presence of contaminants played a decisive role on immobilization of neonates of Ceriodaphnia silvestrii after treatments with compost and, especially, peat. However, the biochar addition rate caused a significant influence on the outcomes of ecotoxicity across all tested species. Although the samples treated with biochar exhibited lower residual concentrations of PTMs than those treated with compost and peat, the inherent toxicity of biochar might be attributed to the material itself. The exposure to residual PTM concentrations post-desorption caused ecotoxic effects on tested species, emphasizing the need to assess PTM desorption potential. Peat, compost, and biochar are promising alternatives for the sorption of PTMs, but the addition rates must be properly adjusted to avoid the occurrence of undesirable ecotoxicological effects. This research offers valuable insights for sustainable environmental management and protection by thoroughly investigating the impacts of different sorbents and contaminants on aquatic and terrestrial ecosystems. [Display omitted] • Pb had lowest bioaccessibility among tested metals when pre-sorbed onto the compost. • The sensitivity order was established as: root length > shoot length > germination. • Eruca sativa displayed higher phytotoxicity compared to Zea mays. • Biochar revealed inherent aquatic ecotoxicity in Ceriodaphnia silvestrii. • The toxicity of peat and compost samples originated from the presence of PTMs. [ABSTRACT FROM AUTHOR]

Due to the rapid development of human beings, heavy metals are occurred in the Yunnan-Guizhou Plateau and Panxi Plateau, the special dry and hot climate areas. Pb and Cu can be quickly transferred through water-plant-animal, further harm to human health by food chain. Therefore, the study of heavy metal treatment is imminent. In this study, Biochar-montmorillonite composites were prepared by co-pyrolysis and characterized, and their ability to remove lead and copper from water-soil process were tracked. And their effectiveness in remediating soil contaminated by lead and copper was documented. The composite material has the rich pore structure, large specific surface area (81.5 m2/g) and a variety of surface functional groups such as C–C, C O, ester-metal and metal-oxygen bonds. Pb and Cu can be effectively adsorbed and fixed to the level of no harm to human health. The adsorption reaction of lead and copper on the Biochar-montmorillonite composites is more suitable to be described by Langmuir adsorption and pseudo-second-order kinetics models. The saturation adsorption capacity of the composite for Pb was measured as 212.5 mg/g. For Cu, it was 136.5 mg/g. The data were fitted by a two-compartment first-order kinetic model. f fast for Pb and Cu is estimated to be 0.81 and 0.78, respective. Fast adsorption is dominant and belongs to typical chemical adsorption, which is consistent with the second-order kinetic results. With 5 % of the composite, approximately 80 % of exchangeable heavy metals in those soils collected from the Yunnan-Guizhou Plateau and Panxi Plateau were reduced. The biochar-montmorillonite composites made Pb and Cu change to stable residual state, up to 35 %. Besides, it effectively restored the activity of urease and sucrase in soils. Results indicated that biochar-montmorillonite composites can be effectively used as an environment-friendly adsorbent or passivator to purify heavy metals in soils. [Display omitted] • Combining agroforestry wastes with natural clay minerals to prepare composites. • The material has rich pore structure and large specific BET surface area. • The novel-materials have shown excellent sorption capacity for Pb and Cu, and can reach the equilibrium quickly. • The composite material can effectively reduce exchangeable heavy metals and is suitable for different soil properties. [ABSTRACT FROM AUTHOR]

Developing advanced carbon materials by utilizing biomass waste has attracted much attention. Herein, a novel carbon adsorbent derived from Spinach waste was prepared by using pyrolysis procedure with KMnO 4 as the activator. The preparation condition such as activator mass ratio (0–0.16) and activation temperature (200–800 °C) were comprehensively studied. The optimal sample (SBC-0.08–500) showed a 7.38-fold increase in specific surface area compared to the original biochar (SBC-500). Adsorption experiments revealed that SBC-0.08–500 had efficient removal capabilities for Cd(II), Pb(II), Cu(II), and Zn(II) ions. The maximum adsorption capacities for Cd(II), Pb(II), Cu(II), and Zn(II) ions at 298.15 K were 1.66, 2.88, 1.31, and 2.09 mmol∙g−1, respectively. Thermodynamic results indicated that the adsorption of Cd(II), Pb(II), and Zn(II) ions on SBC-0.08–500 was a spontaneous endothermic process. Additionally, SBC-0.08–500 had a high affinity for Pb(II) ions, making it a potential selective adsorbent for the removal of mixed heavy metal ions. The mechanism underlying the adsorption process was attributed to multiple interactions, including ion exchange, electrostatic interaction, and surface complexation. The as-prepared biochar by oxidative activation pyrolysis effectively solves the issues of subsequent chemical recycling and secondary pollution, thus providing greater potential for large-scale use. [Display omitted] • A novel spinach waste-derived biochar was prepared using KMnO 4 as an activator. • Such biochar was proven to have abundant hydroxyl, carboxyl, and manganese oxide groups. • Such biochar delivered superior adsorption performance towards Cd(II), Pb(II), Cu(II), and Zn(II) ions. • Adsorption mechanism was ascribed to ion exchange, electrostatic attraction, and surface complexation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic biochar and ryegrass can remediate heavy metal co-contaminated soils. • Magnetic biochar and ryegrass maintain the stability of soil organic carbon pool. • Magnetic biochar spheres can adsorb more Cr and Ni. • Biochar sustains ryegrass to fix heavy metals continuously. Biochar is a very promising material for soil remediation. However, most studies mainly focus on the adsorption ability of biochar on one heavy metal, which is difficult to evaluate the actual remediation effect since soils were contaminated with multiple heavy metals. In order to improve the soil remediation efficiency, we used the joint remediation method of magnetically modified biochar and ryegrass to remediate the soil polluted by compound heavy metals (chromium, nickel, copper, zinc, arsenic and cadmium), and evaluate the effect on the process of organic carbon mineralization in polluted soils. It was found that magnetic biochar and ryegrass together decreased the concentrations of Cr, Ni, Cu, Zn, As, and Cd in soils by 24.12 %, 23.30 %, 22.01 %, 9.98 %, 14.83 %, and 15.08 %, respectively, and reduced the available fractions. Ryegrass roots were the main accumulation part of heavy metals, and the order of enrichment effect was ranked as Zn > As > Cr > Cu > Ni > Cd. In addition, magnetic biochar can maintained the stability of the organic carbon pool, and inhibited the emission of volatile organic compounds from ryegrass. Overall, this study indicates that magnetic biochar spheres combined with ryegrass is an effective method for heavy metals co-contaminated soils, and has the excellent remediation ability for actual co-contaminated soils. [ABSTRACT FROM AUTHOR]

Biochar (BC) has been substantiated to effectively reduce the available content of heavy metals (HMs) in soil-plant system; however, the risk of biochar (BC)derived dissolved organic matter (DOM) induced metal vertical migration has not been well documented, especially in the long-term field conditions. Therefore, this study investigated HM vertical migration ecological risks and the long-term effectiveness of the amendment of biochar in the three successive years of field trials during the rotation system. The results revealed that biochar application could increase soil pH and DOM with a decrease in soil CaCl 2 extractable pool for Pb, Cu, and Cd. Furthermore, the results indicated a significant decrease in acid phosphatase activities and an increase in urease and catalase activities in the soil. Cucumber was shown to be safe during a three-year rotation system in the field. These results suggest that BC has the potential to enhance soil environment and crop yields. BC derived DOM-specific substances were identified using parallel factor analysis of excitation-emission matrix in deep soil (0–60 cm). The study incorporated HM concentration fluctuations in deep soils, providing an additional interpretation of DOM and co-migration of HMs.The environmental risk associated with the increase in DOM hydrophobicity should not be ignored by employing BC for soil HM remediation applications. The study enhances understanding of biochar-derived DOM's migration and stabilization mechanisms on heavy metals, providing guidelines for its use as a soil amendment. [Display omitted] • Biochar application mitigates heavy metal toxicity and reducing crops risks. • EEM-PARAFAC describes distribution of biochar derived DOM in different deeply soil. • DOM enhances the migration behavior of Cd and Pb in soils of crops rotation system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid modification reduced HMs and extractable PAHs content the most effectively. • H 2 O 2 reduced extractable and bioavailable PAHs but was less effective than acid. • Base treatment significantly increased the extractable PAHs in most BCs. • Porosity and DOC determined contaminant changes in BC after H 2 O 2 or base treatment. The effect of biochars (BCs) chemical modifications on the content of various contaminants is poorly studied and understood, despite the fact that such results would be important in terms of estimating the safety of BCs application. The aim of this study was to evaluate the content of different types of contaminants - heavy metals (HMs), polycyclic aromatic hydrocarbons (solvent extractable - C tot and freely dissolved - C free PAHs) and environmentally persistent free radicals (EPFRs) in post-pyrolytic chemically modified (HNO 3 , KOH and H 2 O 2) BCs produced under diverse conditions (temperature and carrier gas) and from various feedstocks (willow, rice husk, sewage sludge, oil seed rape straw, wheat straw). The physio-chemical properties of BCs were determined (such as morphology, elemental composition and chemical state, and crystalline structure) and correlated with contaminants content. Regardless of the BCs type, acid modification reduced HMs and C tot PAHs the most effectively but simultaneously increased C free PAHs and EPFRs content (compared to pristine BCs). Changes in contaminant content after H 2 O 2 and alkali treatment were more varied and strictly related to the physio-chemical properties of BCs (such as porosity, DOC, and polarity). H 2 O 2 treatment reduced C tot and C free PAHs content but was less effective than acid modification. In contrast, KOH treatment significantly increased the C tot in most BCs, which depends mainly on porosity and DOC changes. Also, the reduction in HMs content and increase in EPFR after alkali and H 2 O 2 treatment were less substantial and more differentiated by BC origin than after acid modification. [ABSTRACT FROM AUTHOR]

Heavy metal (HM) pollution has extensively spread in agricultural soils, posing potential threats to food safety and human health. Biochar and lime are two amendments used to remediate the soils contaminated with HMs. However, colloids have been shown to increase the mobility of HMs in paddy soils. Nevertheless, limited investigations have been made into the impact of biochar and lime on the formation of colloid-associated (colloidal) HMs in paddy soils. In this study, column and microcosm incubation experiments were conducted to examine how biochar and lime affected the availability of HMs (arsenic, cadmium, copper, iron, manganese, lead, and zinc) in different layers of paddy soils. The results revealed that biochar significantly inhibited the formation of colloidal HMs in the soil flooding phase, whereas the lime increased the colloidal HMs. These colloids containing HMs were identified as poorly dissolved metal sulfides. When the soil was drained, colloidal HMs transformed into dissolved forms, thereby improving the availability of HMs. Biochar decreased HM availability by reducing colloidal- but dissolved- HMs, whereas lime had the opposite effect. Hence, biochar demonstrated a stable and reliable remediation ability to decrease HM availability in paddy soil during flooding and drainage processes. In conclusion, this study highlighted that biochar efficiently reduced HM availability by mitigating the formation of colloidal HMs during flooding and their transformation into dissolved HMs during drainage in paddy soils. [Display omitted] • Influence of colloids on the availability of heavy metals (HMs) were investigated. • Decrease in colloids dominantly improved the release rate of HMs during drainage. • Biochar decreased 11–73% and 3–100% of colloid-associated Cu and Cd, respectively. • Lime increased colloid-associated Cu, Cd, Zn, Mn, and Pb by 0.04–2.3 times. • Biochar suppressed the availability of HMs by reducing colloid-associated HMs. [ABSTRACT FROM AUTHOR]

Common isotherm and kinetic models cannot describe the pH-dependent sorption of heavy metal cations by biochar. In this paper, we evaluated a pH-dependent, equilibrium/kinetic model for describing the sorption of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) by poultry litter-derived biochar (PLB). We performed sorption experiments across a range of solution pH, initial metal concentration, and reaction time. The sorption of all five metals increased with increasing pH. For Cd, Cu, and Pb, kinetics experiments demonstrated that sorption rates were greater at pH 6.5 than at pH 4.5. For each metal, all sorption data were described using single set of four adjustable parameters. Sorption edge and isotherm data were well described with R2 > 0.93 in all cases. Time-dependent sorption was well described (R2 ≥ 0.90) for all metals except Pb (R2 = 0.77). We then used the best-fit model parameters to calculate linear distribution coefficients (K D) and equilibration times as a function of pH and initial solution concentration. These calculations provide a more robust way of characterizing biochar affinity for metal cations than Freundlich distribution coefficients or Langmuir sorption capacity. Because this model can characterize metal cation sorption by biochar across a wider range of reaction conditions than traditional isotherm or kinetic models, it is better suited for estimating metal cation/biochar interactions in engineered or natural systems. [Display omitted] • The sorption of metals by poultry litter biochar increased with increasing pH. • Sorption kinetics were slower at low pH for cadmium, copper, and lead. • A pH-dependent model described equilibrium and time-dependent sorption. • The model is more appropriate for screening biochars than sorption capacity. [ABSTRACT FROM AUTHOR]

Bone biochar (BC) has a high capacity for the immobilization of potentially toxic elements (PTEs); however, its effect on dendroremediation efficiency remains unclear. Therefore, this study aimed to determine the effects of various concentrations (0, 0.5, 1, and 2 wt%) of BC, ball-milled BC (MBC), and Fe–Mn oxide-modified BC (FMBC) on soil properties, plant growth, and metal accumulation in Salix jiangsuensis "172" (SJ-172) grown in cadmium (Cd)- and zinc (Zn)-contaminated soil. BC and MBC promoted the photosynthetic rate, mineral element absorption, and plant growth of SJ-172, whereas FMBC inhibited the growth of SJ-172. Different biochars greatly influenced the concentrations of Cd and Zn in tissues of SJ-172. BC and MBC elevated the Cd levels, whereas FMBC decreased the Cd content in the leaves, stems, and cuttings of SJ-172. Unlikely, BC, MBC and FMBC show no evident change to the Zn concentration in the aboveground tissues of SJ-172, while decreased root Cd and Zn content compared with the control. MBC, at a 2.0% application rate, significantly increased the translocation factors of Cd (55.0%) and Zn (40.87%), whereas BC and FMBC demonstrated no significant effects compared with the control (P > 0.05). Moreover, 2.0% BC and MBC increased Cd and Zn accumulation in SJ-172 by 28.40 and 41.14, and 25.89 and 36.16%, respectively, whereas 2.0% FMBC reduced Cd and Zn accumulation by 53.20% and 13.18 %, respectively, compared with the control. The phytoremediation potential of SJ-172 for Cd- and Zn-contaminated soils was enhanced by MBC and BC, whereas it was lowered by FMBC compared to the control. These results provide novel insights for the application of fast-growing trees assisted by biochar amendments in the dendroremediation of severely PTEs-contaminated soil. [Display omitted] • Ball-milled bone biochar shows greater capacity to reduce the bioavailability of soil Cd/Zn. • Ball milling can accelerate the release of available phosphate from bone biochar. • 2.0 wt% ball-milled bone biochar elevated Cd/Zn concentration and accumulation in aerial portion of Salix jiangsuensis "172". • Excessive FeO x and MnO x in Fe–Mn oxide-modified biochar seriously impeded the growth and Cd/Zn accumulation of willow. • Ball-milled bone biochar-phytoremediation synergy can effectively remediate the heavily PTEs-contaminated soil. [ABSTRACT FROM AUTHOR]

Biosensors play a very important role in pollutant monitoring, but there are still some problems such as stability, repeatability and low detection limits. Therefore, it is necessary to explore ways to increase the performance of biosensors. In this study, biochar-MFC sensors were constructed for heavy metals monitoring in constructed wetlands (CWs), and the correlation, repeatability and anti-interference were studied. At 1.0 M/L concentrations of heavy metals (Ni, Cu, Zn and Cr), CW with biochar as filler (B-CW) had an output voltage of 0.69 V, extending the detection limit of the sensor. B-CW had advantages in anti-interference and reproducibility. The results showed that B-CW had higher abundance of electrogenic bacteria than CW. Shewanella and Proteobacteria , main electricity-producing bacteria, increased 3-fold. The electrochemically active microorganism Shewanellaceae made up 6.2% of the B-CW microbial population, but was not detected in CW. The abundance of key genes AarC increased by 1295.8% in B-CW. More importantly, the abundance of extracellular electron transport chain related genes (MtrA , OmcA) increased significantly (p < 0.01). Biochar can promote oxidative phosphorylation, thus increasing the sensor's output voltage and detection range. This study is expected to provide support for the engineering application of MFC sensor in CWs. [Display omitted] • MFC-sensors can effectively detect heavy metals in constructed wetlands. • Extracellular electron transfer significantly increased in biochar system. • Biochar increased genes associated with oxidative phosphorylation by about 27%. • Biochar significantly enhanced the repeatability and anti-interference of the sensor. [ABSTRACT FROM AUTHOR]

The lack of power resources leads to the rapid development of biomass power generation. Biomass power generation technology can not only rationally utilize biomass resources, but also alleviate energy crisis. But if this biomass ash is not handled properly, indiscriminate dumping can cause serious environmental problems such as dust, air and water pollution. The purpose of this study was to use the basic physical and chemical properties of biomass waste ash and biochar to evaluate the effects of mixed uses on soil pH、heavy metal remediation and plant growth. Plant growth was undertaken using ryegrass to examine the potential value of an ash-biochar mixture to ameliorate soil acidity and heavy metal pollution. The special fertilizer for rice was prepared by adding ammonium dihydrogen phosphate, potassium chloride, and urea to the ash and biochar. The results showed that the mixed use of ash and biochar could ameliorate soil acidification, reduce the absorption of cadmium and lead by the plants (43 % and 35 %, respectively), and promote plant growth. Determining of its total nutrients, soluble phosphorus, nitrate nitrogen, and particle size supported that it fell within the high concentration fertilizer range of the national standard for compound fertilizers. The special fertilizer can be used as high quality fertilizer to promote crop growth. In-depth research on the treatment and recycling of biomass power generation waste ash has an essential effect on reducing secondary environmental pollution and waste recycling.It can reduce random dumping, thereby reducing dust, air and water pollution. This was conducted to provide a reference for the preparation of soil amendments and to develop a better amendment and high-quality special fertilizer for rice with biomass waste ash and biochar. [Display omitted] • Ash and biochar addition increased soil pH and promoted plant growth. • Ash and biochar can inhibited cadmium uptake and lead by ryegrass. • Special fertilizers based on ash and biochar reach the quality fertilizer standards. • The special fertilizer improved soil fertility and rice growth. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (HP) was used to pretreat wheat straw (WS) for microwave biochar production at 100–600 W, the physicochemical properties of pretreated WS and biochar products as well as heavy metals adsorption performance were investigated. Results showed that HP enhanced specific surface area (SSA) and pore volume (PV) of WS, and the largest SSA (190.35 m2 g−1) and PV (0.1493 cm3 g−1) of biochar were obtained at microwave powers of 600 W (HPWS600) and 500 W (HPWS500), respectively. HPWS500 showed maximum adsorption capacities, which were 57.56, 190.21, and 65.16 mg g−1 for Cd2+, Pb2+, and Cu2+, respectively. Solution pH values and cation concentrations exhibited significant effects on adsorption capacities of biochar. The pseudo-second-order kinetic and Langmuir isotherm models fitted better for metal adsorption process. The FTIR results suggested that chemisorption mechanisms including precipitation with carbonate and complexation with oxygen-containing functional groups might be predominant adsorption mechanisms. These results suggest that HP pretreatment has excellent potential for biochar production. [Display omitted] • Hydrogen peroxide pretreatment enhanced porosity of wheat straw. • Biochar showed enhanced physico-chemical properties and adsorption capacities. • The maximum SSA and PV of biochar were 190.35 m2 g−1 and 0.1493 cm3 g−1. • Maximum adsorption capacities for Pb2+, Cd2+ and Cu2+ were 190.21, 57.56, and 65.16 mg g−1. • Adsorption mechanisms included surface complexation and precipitation. [ABSTRACT FROM AUTHOR]

In acidic mine wastewater, Mn and Fe are among the prime heavy metals and pose a great threat to the ecological environment and human health. Combining biological and physical methods to treat heavy metal contaminated water bodies is a promising remediation technique. In this study, grapefruit peel biochar immobilized Acinetobacter sp. AL-6 (co-system) was applied to treat the contaminated water with co-existing Mn2+, Fe2+ and NH 4 +-N. The results showed that almost 100% of Mn2+, Fe2+, Zn2+ and Cu2+ were removed in bioreactor, and was transferred to Mn2+, Fe3+, Zn2+ and Cu2+ precipitates on the surface of co-system without N 2 O accumulation. Especially, Mn2+ and Fe2+ were adsorbed in extracellular polymers (EPS) of strain AL-6. The present study mainly confirmed that the combined system of biochar and bacteria had great potential in the complex water removal of multiple heavy metals and NH 4 +-N, and also revealed the regulation of heavy metals by the EPS of strain. [Display omitted] • Biochar-immobilized Acinetobacter can be applied for Fe and Mn bioremediation. • EPS production was promoted by higher Fe for resisting unscrupulous stress. • Fe and Mn can be adsorbed by the surface of EPS. • CO 2 could suppressed by the increasing Fe concentration. [ABSTRACT FROM AUTHOR]

In recent ages, industrial revolution and natural weathering processes have been increasing lead (Pb) contamination in agricultural soils, therefore, green remediation technologies are becoming attractive and cost-effective. In the current pot study, 1% and 2% (w/w) application rates of sulfur (S) alone and novel chemo-mechanically S-modified baby corn biochars (CSB and MSB) were applied in a Pb-contaminated (500 mg/kg) soil to evaluate tomato (Lycopersicon esculentum L.) growth, Pb uptake and its soil availability. The results from SEM-EDS and XRD patterns confirmed the S enrichment on the surface of baby-corn biochar. Further, Pb treatment alone imposed a significant reduction in biomass accumulation, photosynthetic pigments, antioxidative mechanism, root traits, and Pb-tolerance index because of increased soil Pb availability and its uptake, translocation and biological accumulation in various tissues of tomato. However, incorporation of lower rate of elemental S (1%) and higher rates of biochars, especially chemically S-modified biochar, CSB (2%) significantly improved dry biomass production, Pb-tolerance index, physiological attributes and antioxidative defense system of tomato plants. These results might be due to a prominent decrease in soil Pb availability by 37.5%, Pb concentration in shoot by 66.7% and root by 58.3%, soil to root transfer by 33.8%, and root to shoot transfer by 20.2% in tomato plants under 2% application rate of CSB, as compared with the Pb treatment without any amendment. Moreover, sulfur treatment induced a significant impact in reduction of soil pH (from 8.97-7.47) as compared to the biochar treatments under Pb-toxicity. The current findings provided an insight that 2% chemically S-modified biochar (CSB) has significant potential to improve the tomato growth by reducing Pb bioavailability in the Pb-contaminated soil, compared to the S alone and MSB amendments. [Display omitted] • Chemically modified BC (CSB) was more effective in S loading than other BC. • CSB significantly reduced soil available Pb than MSB and S alone treatments. • CSB improved growth, physiological traits of Pb-stressed plants than other amendment. • S alone was more effective in reducing soil pH to neutrality than modified biochars. [ABSTRACT FROM AUTHOR]

Antibiotics and heavy metals are frequently detected simultaneously in water environment. Effective elimination methods for antibiotics and heavy metals pollution should deserve our attention. This study investigates the adsorption performance of biochar modified with nano-hydroxyapatite (nHAP) on tylosin (TYL) and Cu from water simultaneously. Composite adsorbents of nHAP and biomass, derived from three waste residues, which were wood-processing residues (WR), wheat straw (WS) and Chinese medicine residues (CMR), were prepared. According to the results of orthogonal experiment, the degree of influence of the three factors on TYL and Cu were the pyrolysis temperature > the proportion of nHAP and biomass > the sources of biomass, and pyrolysis temperature> the sources of biomass> the proportion of nHAP and biomass, respectively. The optimum conditions for nHAP@biochar were screened. At pH < 7.0, the adsorption quality of TYL increased with pH increased, while at pH > 7.0, the adsorption quality of TYL changed slightly. At low pH, Cu and TYL could compete for the same adsorption sites on nHAP@biochars. The adsorption amount of TYL and Cu were both increased with increasing of the temperature. Compared with Langmuir model, Freundlich model could better fit the TYL adsorption on nHAP@biochars, with K f values of TYL 62.35 (mmol/kg) (L/mmol)n (WR1) and 4.84 (mmol/kg) (L/mmol)n (CMR1), respectively. • A composite adsorbent of nano-hydroxyapatite and biomass were prepared. • Tylosin and Cu could be removed simultaneously by nHAP@biochars. • Pyrolysis temperature influenced mostly the removal efficiency. • PH and temperature could influence the adsorption. [ABSTRACT FROM AUTHOR]

Sustainable management of contaminated biomass derived from phytoremediation of metal(loid) polluted soil and water is of great importance to avoid environmental risks from secondary pollution of the contaminants. In this regard, pyrolysis technology may reduce the environmental risk of the contaminants and produce different bio-products from contaminated biomass. In this work, slow pyrolysis of Avicennia marina biomass was conducted to compare the pyrolysis properties of heavy-metal-contaminated and uncontaminated biomass and its potential to generate pyrolytic products, such as biochar, bio-oil and pyrolytic gas at a varying temperature range from 300 to 800 °C. The results indicated that the properties of biomass and derivatives were affected significantly by both pyrolysis temperature and the presence of heavy metal(loid)s. The heavy metal(loid)s in biomass contributed to higher biochar and pyrolytic gas yields at the expense of bio-oil. Increasing pyrolysis temperature induced the volatilisation of heavy metal(loid)s in biochar samples. At the same pyrolysis temperature, the contaminants significantly increased the ash content whilst decreased the fixed carbon content in biochars (p < 0.05). Furthermore, it was noticed that the quality of bio-oils was improved by the presence of metal(loid)s, as the pyrolysis of contaminated biomass produced 8–11% hydrocarbons in the bio-oil samples with less oxygenated compounds as compared to uncontaminated biomass that produced only 4–5.8% hydrocarbons in the bio-oil. Moreover, biomass abound with trace metal(loid)s produced more H 2 and CO 2 during pyrolysis compared to uncontaminated biomass. Overall, this study demonstrated that pyrolysis is an efficient way for converting heavy metal contaminated biomass obtained from phytoremediation into valuable products, contributing to the sustainability of phytoremediation. Image 1062189 • Contaminated and uncontaminated biomass and pyrolytic products were studied. • Temperature and contaminants affected biomass and pyrolysis products properties. • The biochar yield was significantly increased with presence of heavy metal(loid)s. • Heavy metal(loid)s were enriched in biochars by pyrolysis at lower temperatures. • Hydrocarbons in bio-oils increased greatly with presence of heavy metal(loid)s. [ABSTRACT FROM AUTHOR]

Soil contamination in mining areas is an important environmental concern. In these areas, phytoremediation is often impeded because of the low fertility and pH. Assisted phytoremediation is increasingly being used in polluted areas. Biochar could assist plant growth via enhanced soil fertility. An experiment was performed in a mining soil (RIII) from the mining area of Riotinto (Spain) contaminated with Cu, Pb, Zn and As in order to study: (i) The effects of biochar on soil fertility; (ii) Biochar temperature of preparation effect and (iii) Effect of biochar on phytoremediation potential. A mesocosm experiment was designed using Brassica napus as test specie. Soil (RIII) was treated with rabbit manure biochars prepared at 450 °C (BM450) and 600 °C (BM600) at a rate of 10% in mass and incubated for 60 days with or without Brassica napus. Results showed that the combination of BM450 or BM600 with Brassica napus growth decreased the amount of As, Cu, Co, Cr, Se and Pb in the soil. Values of bioaccumulation factor (BAF) for Cd were particularly elevated (>10) in the unamended soil and reached values higher than 1 for other elements, indicating the potential of Brassica napus to accumulate several heavy metals. Translocation Factor (TF) was reduced for Co, Cr, Cd, Cu, Ni, Zn, Pb and As after biochar addition indicating root accumulation of these metals. In all cases, biochar addition increased biomass production. Finally, the addition of BM450 increased GMea index indicating also an improvement on soil quality. Image 1 • Biochar increased biomass production in heavy metal contaminated soil. • Combining biochar and Brassica napus reduce As, Cu, Pb, Se in soil. • Manure biochar promotes heavy metal extraction by Brassica napus. • Manure biochar increased microbial activity in heavy metal contaminated soil. [ABSTRACT FROM AUTHOR]

Proper management of waste crop residues has been an environmental concern for years. Yellow mealworms (larvae of Tenebrio molitor Linnaeus, 1758) are major insect protein source. In comparison with normal feed wheat bran (WB), we tested five common lignocellulose-rich crop residues as feedstock to rear mealworms, including wheat straw (WS), rice straw (RS), rice bran (RB), rice husk (RH), and corn straw (CS). We then used egested frass for the production of biochar in order to achieve clean production. Except for WS and RH, the crop residues supported mealworms' life activity and growth with consumption of the residues by 90% or higher and degraded lignin, hemicellulose and cellulose over 32 day period. The sequence of degradability of the feedstocks is RS > RB > CS > WS > RH. Egested frass was converted to biochar which was tested for metal removal including Pb(II), Cd(II), Cu(II), Zn(II), and Cr(VI). Biochar via pyrolysis at 600 °C from RS fed frass (FRSBC) showed the best adsorption performance. The adsorption isotherm fits the Langmuir model, and kinetic analysis fits the Pseudo-Second Order Reaction. The heavy metal adsorption process was well-described using the Intra-Particle Diffusion model. Complexation, cation exchange, precipitation, reduction, deposition, and chelation dominated the adsorption of the metals onto FRSBC. The results indicated that crop residues (WS, RS, RB, and CS) can be utilized as supplementary feedstock along with biochar generated from egested frass to rear mealworms and achieve clean production while generating high-quality bioadsorbent for environment remediation and soil conditioning. Image 1 • Clean production study with 5 crop residues as feedstock of mealworms for insect biomass production. • The sequence of selection of feedstock was rice straw > corn straw > wheat straw based on consumption rates. • Mealworms ate more than 93% of rice straw and digested 49.78% lignin. • Biochars generated from mealworm frass adsorbed heavy metal ions effectively. • Biochar from rice straw frass showed best adsorption capacity and mechanisms were investigated. This research describes a novel clean production approach that agricultural waste residues (wheat straw, rice straw, rice bran, rice husk and corn straw) were used as feedstock to grow mealworms for insect biomass production; biochar was generated using mealworm frass; rice straw was the best feedstock tested based on digestibility and the frass derived showed optimal adsorption performance for heavy metal removal; and adsorption mechanisms were characterized. [ABSTRACT FROM AUTHOR]

Graphic abstract Highlights • Governing adsorption mechanisms of heavy metals onto carbon adsorbents are summarized. • Various methods for introduction of oxygen, nitrogen, and sulfur functional groups onto carbon surfaces are categorized. • Effects of various functional groups on heavy metal adsorption onto different carbon materials are discussed. • Perspectives of future work on functionalized carbon adsorbents for heavy metal removal is also presented. Abstract Carbon-based adsorbents such as graphene and its derivatives, carbon nanotubes, activated carbon, and biochar are often used to remove heavy metals from aqueous solutions. One of the important aspects of effective carbon adsorbents for heavy metals is their tunable surface functional groups. To promote the applications of functionalized carbon adsorbents in heavy metal removal, a systematic documentation of their syntheses and interactions with metals in aqueous solution is crucial. This work provides a comprehensive review of recent research on various carbon adsorbents in terms of their surface functional groups and the associated removal behaviors and performances to heavy metals in aqueous solutions. The governing removal mechanisms of carbon adsorbents to aqueous heavy metals are first outlined with a special focus on the roles of surface functional groups. It then summarizes and categorizes various synthesis methods that are commonly used to introduce heteroatoms, primarily oxygen, nitrogen, and sulfur, onto carbon surfaces for enhanced surface functionalities and sorptive properties to heavy metals in aqueous solutions. After that, the effects of various functional groups on adsorption behaviors of heavy metals onto the functionalized carbon adsorbents are elucidated. A perspective of future work on functional carbon adsorbents for heavy metal removal as well as other potential applications is also presented at the end. [ABSTRACT FROM AUTHOR]

This study was performed to investigate the effect of biochar manufactured from agriculture residues for the stabilization of lead, cadmium and chromium (Pb, Cd and Cr) in artificially contaminated soil. A surface loamy sand soil was spiked with Pb, Cd and Cr at 200, 400 and 600 mg kg−1. Thereafter, the spiked soil was treated with biochar at different rates of 0.0, 1.0, 2.5, 5.0 and 10% (weight basis) and incubated for 30 days. The treated soil was cultivated with maize plant (Zea mays) lasting 30 days. Addition of biochar significantly increased the soil reaction (pH), organic matter (OM) and nutrient content of nitrogen, phosphorus and potassium (N, P and K). Moreover, the addition of biochar considerably decreased the solubility of Pb and Cd in terms of water soluble, exchangeable (extracted by ammonium nitrate), physiological based extraction test (PBET) and toxicity characteristics leaching procedure (TCLP) extracts. The highest reduction of expendable Pb and Cd were 28.68% and 85.14%, respectively. On the other hand, addition of biochar might facilitated Cr solubility through the transformation of Cr(III) into Cr(VI) due to increasing soil pH, and increased its uptake by maize plant. The phytotoxicity test revealed that biochar significantly increased maize biomass (shoots and roots), especially with applications of 5% and 10% treatments. Our findings provide evidence that biochar application decreased Pb and Cd toxicity by immobilizing them into more stable forms and improved soil quality. However, attention should be paid when treating the soil that is co-contaminated by Cr with biochar. [ABSTRACT FROM AUTHOR]