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[Display omitted] • Present in BC HM and PAHs are crucial considering biochar toxicity. • Predicting the bioavailability of PAHs using the total content is misleading. • Toxicity was influenced by BC's bioavailable PAHs > ash > total PAHs content. • Oxygen-containing functional groups were crucial in revealing the toxicity. • Indicating a safe material for soil and environmental applications is difficult. Agricultural or environmental application of biochar (BC) is connected with the introduction of biochar-derived components among which polycyclic aromatic hydrocarbons (PAHs) and heavy metals are the most toxic. Their presence and bioavailability are crucial considering biochar toxicity. The effect of feedstock and pyrolysis temperature on the physicochemical properties of produced biochar and contaminant content was established and combined with toxicity to a broad range of living organisms. The obtained data revealed that predicting the bioavailability of PAHs using the total content is misleading. The toxicity was influenced by factors in the following way: the bioavailable PAHs > ash > total PAHs content in BC stressing the role of BC physicochemical characteristics. Among tested BC properties, surface functionalization, e.g. presence of oxygen-containing functional groups was crucial in revealing the toxicity. The data clearly indicate that additional research is required to determine BC's impact on various organisms and performing one ecotoxicity test is not sufficient. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tolerance of Cu(II) for microalgae was slightly greater in comparison to Co(II). • Cu(II) & Co(II) absorbed algal biomass had 1.2 & 1.1 time higher lipid respectively. • Co-accumulated activated algal biochar (ABC Co) acted as excellent cathode catalyst. • Removed highest 94% and 88% of Cu(II) and Co(II), respectively through PMFCs. • PMFC operated with ABC Co cathode catalyst exhibited 64.2 mW/m2 of power density. Cytotoxic, malignant, and mutagenic pollutants like heavy metals have emerged as a serious global threat to the ecosystem. Additionally, the quantity of noxious metals in water bodies has increased due to expanding industrial activities and the application of incompetent wastewater treatment techniques. Owing to the benefits of eco-friendly phytoremediation, the utilization of algae in photosynthetic microbial fuel cell (PMFC) for removal of heavy metals has attracted increasing attention among researchers. Therefore, a successful fabrication and operation of a modular PMFC for simultaneous algal biomass production was exhibited, thus resulting in significant removal efficiency of Cu(II) (94 %) and Co(II) (88 %). Moreover, Co(II)-accumulated algal biochar after thermal activation was utilized as a cathode catalyst for the first time and attained 64.2 mW/m2 of power density through PMFC. Hence, this easily synthesised green cathode catalyst proved its ability to enhance the overall performance of PMFC by attaining higher power output while treating wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • The LA yield of FW fermentation reached 0.91 g LA/g total sugar with 1 % ITs addition. • The mechanism analysis of ITs promoting LA fermentation of FW was demonstrated. • Pyruvate to LA conversion was facilitated by 1 % ITs with a high NADH/NAD+ ratio. • Lactococcus and Lactobacillus were more abundant with ITs addition. • LAB of FW fermentation system can partially remove heavy metals from ITs. In this study, the feasibility of promoting the lactic acid (LA) fermentation of food waste (FW) with iron tailings (ITs) addition was explored. The best LA yield was 0.91 g LA/g total sugar when 1 % ITs were added into the system. The mechanisms for promoting LA production were acidification alleviation effects and reduction equivalent supply of ITs. Furthermore, the addition of ITs promoted carbohydrate hydrolysis, and the carbohydrates digestibility reached 88.85 % in the 1 % ITs group. The ITs also affected the microbial communities, Lactococcus gradually replaced Streptococcus as the dominant genus, and results suggested that Lactococcus had a positive correlation with LA production and carbohydrate digestibility. Finally, the complex LAB in FW had significant effects on heavy metal removal from ITs, and the removal efficiency Cr, As, Pb, Cd, and Hg can reach 50.84 %, 26.72 %, 59.65 %, 49.75 % and 78.87 % in the 1 % ITs group, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparison of contamination levels and BMP of bio-waste from different sources. • Cu and Zn were the main trace metals found in bio-waste, regardless of its source. • Plastics were the most recurrent physical inorganic impurity. • Depackaged food waste from processing plants presented low contamination levels. This study evaluated the anaerobic digestion suitability of bio-waste from different sources by comparing their biochemical methane potential (BMP), biodegradability (BI), and content of contaminants (heavy metals and physical impurities) − an often-overlooked factor but one of particular concern in bio-waste. Predominant heavy metals included Cu and Zn, while recurring physical impurities comprised plastics and organic non-biodegradable matter. Food waste from food processing plants were most suitable, exhibiting low contamination and high biogas conversion (BMP > 549 NmLCH 4 /gVS and BI > 86 %). Conversely, organic fractions from mechanical biological treatment were highly contaminated, while green waste displayed low biogas conversion (BMP < 368 NmLCH 4 /gVS and BI < 72 %). Food waste from households and medium/large-sized producers also demonstrated high biogas conversion, but variable contamination levels could compromise their suitability. Assessing contaminants alongside BMP and BI provides a comprehensive approach for selecting suitable bio-waste feedstocks that can be introduced in biogas plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hyperthermophilic composting products (HP) more effectively adsorb heavy metals. • High content of hydroxyl and carboxyl groups in HP is responsible for adsorption. • HP decreases heavy metals leaching concentration and the risk level in the soil. • HP promotes heavy metal transformation from unstable to stable chemical forms. Due to high humification, hyperthermophilic composting products (HP) show potential for remediating heavy metal pollution. However, the interaction between HP and heavy metals remains unclear. This study investigated the adsorption mechanism and soil remediation effect of HP on heavy metals. The results showed that the maximum adsorption capacity of HP increased by an average of 30.74 % compared to conventional composting products. HP transformed 34.87 % of copper, 42.55 % of zinc, and 35.63 % of lead from exchangeable and reducible forms into residual and oxidizable forms, thus reducing the soil risk level. In conclusion, HP significantly enhanced the adsorption of heavy metals and their transformation from unstable to stable forms, primarily due to the higher content of hydroxyl and carboxyl groups. This study aims to demonstrate the effectiveness of HP for remediating heavy metal pollution and to enhance the understanding of the underlying mechanism, which lays a foundation for waste utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chinese herb residue was used as a low-cost feedstock for CMBC production. • CMBC showed superior adsorption performance for Cr(VI), As(III), and Pb(II) removal. • Multi-heavy metals were effectively separated from a variety of water bodies by CMBC. • DFT revealed that –COOH contributes more to heavy metals removal than –OH and –NH 2. In this study, the sorption properties of Cr(VI), As(III), and Pb(II) on chitosan-modified magnetic biochar (CMBC) derived from residues of Ligusticum chuanxiong Hort. were investigated. CMBC was found to be a valuable material for removing three heavy metals from water simultaneously. Kinetic analysis suggested Cr(VI), As(III), and Pb(II) were chemisorbed onto CMBC, while isotherm data conformed well to Langmuir model, the maximum adsorption capacity of CMBC was found to be 65.74 mg/g for Cr(VI), 49.32 mg/g for As(III), and 69.45 mg/g for Pb(II). Experiments, characterization, and density functional theory (DFT) calculations were employed to explore the mechanisms. Furthermore, CMBC demonstrated excellent removal rates of over 95% for Cr(VI), 99% for As(III) and Pb(II) from contaminated water bodies. This work shows that CMBC holds significant potential for wastewater treatment of heavy metals and provides an effective solution for the utilization of Chinese herb residues in environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Implementation of P recovery strategies strongly depends on sludge/ash characteristics. • P release from EBPR sludge up to 51–60 % after 48–56 h with acidogenic fermentation. • Acid and alkaline extraction from EBPR/chemical mixed sludge was unsatisfactory. • Acid extraction from ashes from EBPR sludge ensured low Fe and Al contamination. Three different technological solutions, namely acidogenic fermentation and chemical extraction (alkaline or acidic), followed by precipitation with 1% Ca(OH) 2 , were investigated in the view of integrating phosphorus recovery into existing wastewater treatment plants. Experiments were conducted at the lab-scale using (i) sludge taken from biologically and chemically promoted phosphorus removal activated sludge processes and (ii) ashes obtained from sludge muffle incineration. Results highlighted the benefits of enhanced biological phosphorus removal (EBPR) systems rather than chemically promoted phosphorus removal in not only phosphorus extraction (up to 40% with EBPR) and recovery directly from secondary sludge (P precipitation between 66 and 92%), but after sludge incineration as well (P extraction up to 96% and precipitation above 96%). Acidogenic fermentation ensured the highest phosphorus release from EBPR sludge (equal to a concentration in solution of 122 mg/L P-PO 4 3−), while the derived ashes had a lower level of metal contamination (particularly Fe and Al content < 2%). The phosphorus-rich product obtained by means of the recovery process showed relevant metal contamination (Cu, Zn, and Ni) under some operating conditions, suggesting the need for further treatments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ionic liquid-catalyzed sludge hydrothermal achieves 6–15 % energy recovery. • More than 75% of Fe, Mn, Zn, Co, and Cd is removed by ionic liquid. • Ionic liquid promotes production of fixed carbon and small molecule polymers. • Ionic liquid leads to mesopore collapse and graphitization of hydrochar. An ionic liquid (IL, [DMAPA]HSO 4) was prepared to facilitate the removal of heavy metals by hydrothermal carbonization (HTC) in sewage sludge (SS) and to obtain a positive energy recovery (ER, (Energy output /Energy input − 1) > 0). The results found that the removal efficiencies of the Fe, Mn, Zn, Co, and Cd from SS exceeded 75 % with positive ER (6 %) at 20 wt% IL dosage (IL:SS). IL promoted the HTC reactions of proteins and polysaccharides to produce fixed carbon and small molecule polymers. The process mainly relies on IL to catalyze the dehydration and graphitization of SS and to destroy the heavy metal binding sites such as carboxyl and hydroxyl groups. Additionally, IL aids in constructing the macropore structures in hydrochar, thereby facilitating the release of heavy metals and water during the HTC process. This discovery holds promise for removing heavy metals from SS by one-pot HTC processes with positive energy recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SAAs was inhibited by 15–20 % at Pb(II) concentrations of 0.1 to 0.5 mg L−1. • The SAAs increased at salinity below 10 g/L but declined with higher salinity. • Combined high salinity and Pb(II) reduced nitrogen removal performance and SAAs. • Combined salinity and Pb(II) enhanced EPS secretion with decreased PN/PS ratio. • Decreased Candidatus Kuenenia and enhanced denitrification under combined stresses. The study assessed the effect of salinity and lead (Pb(II)) on the anammox sludge for nitrogen removal from saline wastewater. Results showed decreased nitrogen removal and specific anammox activity (SAA) with elevated salinity and Pb(II). SAA reduced from 541.3 ± 4.3 mg N g−1 VSS d−1 at 0.5 mg/L Pb(II) to 436.0 ± 0.2 mg N g−1 VSS d−1 at 30 g/L NaCl, further to 303.6 ± 7.1 mg N g−1 VSS d−1 under 30 g/L NaCl + 0.5 mg/L Pb(II). Notably, the combined inhibition at salinity (15–20 g/L NaCl) and Pb(II) (0.3–0.4 mg/L) exhibited synergistic effect, while higher salinity and Pb(II) aligned with independent inhibition models. Combined inhibition decreased protein/polysaccharides ratio, indicating more severe negative effect on anammox aggregation capacity. Metagenomics confirmed decreased Candidatus Kuenenia, and enhanced denitrification under elevated salinity and Pb(II) conditions. This study offers insights into anammox operation for treating saline wastewater with heavy metals. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pyrolysis activation energy of WAS decreased by using the Coats-Redfern method. • Hydrothermal carbonization reduces the pyrolysis reaction activity of hydrochar. • Hydrothermal carbonization promoted the release of P and N at 200 °C. • Hydrothermal carbonization can improve the stability of heavy metals in WAS. In this study, the effect of hydrothermal carbonation (HTC) on the pyrolysis behavior and the distribution of nutrients and metal species of waste-activated sludge (WAS) was investigated. Results showed that the pyrolysis activation energy range of WAS decreased from 11 to 57 kJ/mol to 10–36 kJ/mol when the hydrothermal carbonization was at 160 °C. As indicated by thermodynamic parameters, the hydrothermal carbonization process reduces the pyrolysis reaction activity of the hydrochar. The results of the chemical analysis indicate that hydrothermal carbonization significantly enhances the release of phosphorus and nitrogen, with maximum recovery at a temperature of 200 °C. The standard measurement and testing protocol revealed that hydrothermal carbonization increased the content of non-apatite inorganic P fraction in hydrochar and enhanced the availability of P. Heavy metal analysis shows that hydrothermal carbonization can strengthen the stability of heavy metals in WAS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heavy metal removal by SRB was predicted by machine learning. • The CatBoost model had the best predictive performance for the four metals. • pH, temperature, C/S ratio, and SO 4 2− were critical for HM removal. • The important features of different HM models were compared. A robust modeling approach for predicting heavy metal removal by sulfate-reducing bacteria (SRB) is currently missing. In this study, four machine learning models were constructed and compared to predict the removal of Cd, Cu, Pb, and Zn as individual ions by SRB. The CatBoost model exhibited the best predictive performance across the four subsets, achieving R2 values of 0.83, 0.91, 0.92, and 0.83 for the Cd, Cu, Pb, and Zn models, respectively. Feature analysis revealed that temperature, pH, sulfate concentration, and C/S (the mass ratio of chemical oxygen demand to sulfate) had significant impacts on the outcomes. These features exhibited the most effective metal removal at 35 °C and sulfate concentrations of 1000–1200 mg/L, with variations observed in pH and C/S ratios. This study introduced a new modeling approach for predicting the treatment of metal-containing wastewater by SRB, offering guidance for optimizing operational parameters in the biological sulfidogenic process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrochar-based composting enhanced reduction of heavy metals bioavailability. • Hydrochar addition increased temperature and extended the thermophilic phase. • Hydrochar addition promoted the humic acid (HA) formation during composting. • Bacterial community structure was significantly changed by hydrochar addition. • Bacterial bioremediation and HA complexation promoted heavy metals passivation. This study presented the effects of hydrochar on humification, heavy metals (HMs) bioavailability and bacterial community succession during composting. Results indicated that hydrochar addition led to elevated composting temperature, 7.3% increase in humic acid (HA), and 52.9% increase in ratio of humic acid to fulvic acid. The diethylene triamine pentacetic acid extractable Zn, Cu, Pb, and Ni were reduced by 19.2%, 36.3%, 37.8%, and 27.1%, respectively, in hydrochar-involved composting system. Furthermore, main mechanisms driving the reduced HMs bioavailability by hydrochar addition were revealed. The addition of hydrochar significantly modified the microbial community structure. Correlation analysis and microbial analysis demonstrated that relative abundance of bacterial groups connected with humification and HMs passivation were increased. Consequently, the HA formation was promoted and the HMs bioavailability were reduced through bacterial bioremediation and HA complexation. This study demonstrates the addition of hydrochar as a promising strategy to mitigate the HMs bioavailability during composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorella sp. biochar modified with KOH is superior candidate for Ni(II) removal. • Zero-charge point of 6.87 was obtained for the biochar pyrolyzed under 600 °C. • Microalgae species diversity for biochar preparation to adsorb Ni(II) was revealed. • Ni(II) adsorption was comprehensively optimized via response surface methodology. • 100 % Ni(II) removal was achieved with small biochar dose of 0.5 g/L. Microalgae biochar is potential adsorbents to remove heavy metals from wastewater due to abundant functional groups, high porosity and wide sources, but performance is not fully developed since it depends on microalgae species attributing to distinct morphology and biomass compositions. Here, two microalgae species Chlorella Pyrenoidosa and Scenedesmus Obliquus were used for biochar preparation via KOH-modification, biochar properties and their influences on Ni(II) adsorption were investigated. Ni(II) adsorption performances responding to biochar properties and operating conditions were upgraded via progressive optimization and response surface methodology. Together, adsorption isotherms and kinetics were analyzed to obtain significant factors for Ni(II) removal. As results, 100 % of Ni(II) removal was achieved under 100 mg/L initial Ni(II) concentration as pH was higher than the biochar zero-charge point of 6.87 with low biochar dosage (0.5 g/L), which provides an efficient approach for heavy metal removal from wastewater with microalgae biochar. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pinecone biochar was modified with a novel layered double hydroxide. • LDH-biochar has higher adsorption rates and capacities than pristine biochar. • LDH layer facilitates adsorption of metal ions and phosphate through various mechanisms. This study modified pinecone biochar with a novel layered double hydroxide (LDH) to enhance its capacity to adsorb heavy metal and phosphate ions from water. The unmodified pinecone biochar demonstrated moderate adsorption capacities for Cu2+ (25.0 mg/g), Co2+ (24 mg/g), Pb2+ (22.9 mg/g), and phosphate (36.0 mg/g). However, after LDH modification, the LDH-biochar showed significantly improved adsorption capacities for Pb2+ (135.9 mg/g) and phosphate (160.8 mg/g) and a slight increase for Cu2+ (30.6 mg/g) and Co2+ (28.0 mg/g). The LDH layer enhances the adsorption of Pb2+ through ion exchange, phosphate through surface precipitation, and Cu2+ and Co2+ through surface complexation. The integration of LDH creates a multifaceted layer that utilizes various mechanisms to boost the biochar's adsorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ascophyllum biochar modified with Fe 3 O 4 -NPs enhanced the Cu(II) removal efficiency. • The maximum absorbance efficiency of modified biochar was 53.19 mg g−1. • pH 5 was the best range for effective copper removal from the aqueous solution. • Chemisorption was dominant for Cu(II) binding on the modified biochar surface. • The reusability of modified biochar was enhanced by magnetization. Despite the remarkable Cu(II) sorption biochar potential, it is challenging to desorb them for repeated biochar usage. The present study aims to develop engineered biochar by polarizing Ascophyllum nodosum (seaweed) biomass and magnetizing it with Fe 3 O 4 nanoparticles coating. SEM, EDX, XRD, BET, and FT-IR helped to characterize engineered biochar. Unlike conventional, magnetite biochar exhibited a significant Cu(II) removal potential from an aqueous solution at pH 5. The native and magnetic biochar removal efficiency was 75.2 % (36.99 mgg−1) and 90.27% (45.13 mgg−1), respectively. No significant change in temperature effect was observed. Adsorption study showed that magnetic biochar followed the Langmuir isotherm model with Q max 53.19 mgg−1. Adsorption kinetics study indicates that magnetic biochar chemisorption dominates over physisorption. Thus, this study shows that seaweed-derived modified biochar could be the best alternative bioresource for removing heavy metals from wastewater. It can be reused to reduce the overall treatment cost of the process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Traditional and advanced techniques for biochar production were introduced. • Torrefied biochar had higher calorific value and carbon content with lower energy demand. • The adsorbent and energy carrier were the two main utilizations of torrefied biochar. • Dye, oil, metals, and emerging pollutants in wastewater could be removed by biochar. Biochar, a carbon-rich and por ous material derived from waste biomass resources, has demonstrated tremendous potential in wastewater treatment. Torrefaction technology offers a favorable low-temperature biochar production method, and torrefied biochar can be used not only as a solid biofuel but also as a pollutant adsorbent. This review compares torrefaction technology with other thermochemical processes and discusses recent advancements in torrefaction techniques. Additionally, the applications of torrefied biochar in wastewater treatment (dyes, oil spills, heavy metals, and emerging pollutants) are comprehensively explored. Many studies have shown that high productivity, high survival of oxygen-containing functional groups, low temperature, and low energy consumption of dried biochar production make it attractive as an adsorbent for wastewater treatment. Moreover, used biochar's treatment, reuse, and safe disposal are introduced, providing valuable insights and contributions to developing sustainable environmental remediation strategies by biochar. [ABSTRACT FROM AUTHOR]

[Display omitted] • SP promoted the passivation of Cu, Zn and Mn during composting. • SP increased the proportion of HA and the main abiotic factor of passivation was HA. • Responses of HRMB and HMRGs to Zn, Cu, Mn passivation were explored in composting. • SP improved the adaptability of Actinobacteria to Zn, Cu and Mn stresses. Regulating heavy metal resistance genes (HMRGs) was an effective method for heavy metal resistant bacteria (HMRB) to cope with heavy metal stress during dairy manure composting. This research aimed to investigate heavy metal detoxification mediated by shell powder (SP) in composting and the response of HMRB and HMRGs to changes in heavy metal bioavailability during composting. Research showed that SP additive reduced the bioavailability of Zu, Cu, and Mn by 10.64%, 13.90% and 14.14%, respectively. SP increased the composition percentage of humic acid (HA) in humus (HS) by 8%. SP enhanced the resistance of Actinobacteria to heavy metals and improved the regulation of HMRGs. Correlation analysis demonstrated that the bioavailability of heavy metals was positively correlated with most HMRGs. HA was significantly negatively correlated with the bioavailability of Zn, Cu and Mn. Therefore, SP additive could be a novel strategy for heavy metals detoxification during composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg-modified biocar with functional groups was synthetized by one-pot coprecipitation. • Cys@MgBC has robust reusability and performance due to the complexation effect of -SH. • Functional groups improve the immobilization effect for Cd(II) for a long time. • Multi-mechanisms, especially complexation and precipitation, lead to high adsorption. In this study, a series of biochar products with different active functional groups were developed by one-pot coprecipitation method, including magnesium-modified biochar (MgBC) and functional group-grafted MgBC (Cys@MgBC, Try@MgBC, and Glu@MgBC), for effective adsorption of cadmium (Cd(II)) from wastewaters. These biochars exhibited excellent removal performance for Cd(II), particularly Cys@MgBC, whose maximum Cd(II) adsorption capacity reached 223.7 mg g−1. The highly active and weakly crystalline Mg could adsorb Cd(II) through precipitation and ion exchange, which was further promoted by the introduced functional groups through complexation and precipitation. After 120 d of natural process, the immobilization efficiency of Cd(II) by Cys@MgBC, Try@MgBC, and Glu@MgBC was still maintained at 98.7%, 95.2%, and 82.7% respectively. This study proposes and clarifies the complexation mechanism of functional group-grafted Mg-modified biochar for heavy metals, providing new insights into the practical application of these biochars. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wheat straw hydrochar modified with 0.2 M KMnO 4 obtained optimal results. • KMnO 4 modification loaded MnOx microparticles on hydrochar surface. • Oxygen-containing surface functional groups increased after modification. • KMnO 4 modification enhanced adsorption of Pb(II), Cd(II), Cu(II) by > 10 times. Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO 4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO 4 resulted in the most promising adsorbent (WSHyC-0.2KMnO 4). Characterization of WSHyC and WSHyC-0.2KMnO 4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO 4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO 4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn promoted the removal of Zn by Chlorella , while Zn inhibited the removal of Mn. • The combined effect of Zn and Mn increased the antioxidant activity of algal cells. • Mn upregulates DEGs of catalytic activity and metabolic processes in mixed system. • The HMs content in biomass is a key factor affecting its dosage as feed additives. The remediation effects of living Chlorella sp. HL on zinc and manganese in swine wastewater was investigated, and the responses of algal cells and the mechanism were explored. In the wastewater with Zn(II) concentration of 1.85 mg/L and Mn(II) of 1 or 6 mg/L, the highest removal of Zn(II) by Chlorella reached 86.72% and 97.16%, respectively, and the Mn(II) removal were 42.74% and 30.33%, respectively. The antioxidant system of cells was activated by a significant increase in superoxide dismutase and catalase enzyme activities and a significant decrease in malondialdehyde in the mixed system compared to the single system. The presence of Mn(II) could positively regulate the differentially expressed genes related to catalytic activity and metabolic processes between the single Zn system and the mixed systems, reducing the stress of Zn(II) on Chlorella and more favorable to chlorophyll synthesis. The heavy metal-containing microalgal biomass obtained has the potential as feed additives. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydrochar-wrapped nanofibers derived from Ti 3 AlC 2 were successfully prepared. • Hydrochar-wrapped nanofibers could efficiently adsorb Cd(II) and Cu(II). • Glucose, cellulose or pinewood sawdust was hydrochar precursors. • Fibrous adsorbents were easily recyclable. Abstract To ensure a sustainable future, it is imperative to efficiently utilize abundant biomass to produce such as platform chemicals, transport fuels, and other raw materials; hydrochar is one of the promising candidates derived by hydrothermal carbonization of biomass in pressurized hot water. The synthesis of "hydrochar-wrapped Ti 3 AlC 2 -derived nanofibers" was successfully achieved by a facile one-pot hydrothermal reaction using glucose as the hydrochar precursor. Meanwhile, cellulose and pinewood sawdust as raw materials were also investigated. Products were characterized by XRD, N 2 adsorption-desorption isotherms, SEM, TEM and FT-IR to investigate their crystal structures, textural properties, morphologies, and surface species. In the adsorption test to remove Cd(II) and Cu(II) in aqueous solution, hydrochar-wrapped nanofibers outperformed pure nanofibers derived from Ti 3 AlC 2 , hydrothermal carbon derived from glucose and commercial activated carbon. Finally, the regeneration, sorption kinetics, and possible adsorption mechanism were also explored. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cassia fistula seeds based activated carbon has been synthesized and applied for Ni(II) ion removal from wastewater. • Activation through pyrolysis and chemical treatment has been evaluated. • Langmuir maximum biosorption capacity of SMCF was measured as 182.2 mg/g. • Freundlich and pseudo-first order models satisfy the studied system. • Studied system was found to be feasible and exothermic nature. Abstract The present work demonstrates the preparation of Cassia fistula seeds for producing activated carbon through physical and chemical treatment for the extrusion of Ni(II) ion contaminated aqueous solution. The readily prepared sorbents were characterized using SEM-EDX and FTIR. The surface morphology of sorbents possesses 1 μm mean particle size with uniform size distribution. Furthermore, optimization of operating parameters such as the pH, initial Ni(II) ion concentration, adsorbent dose, time and temperature were investigated. In isotherm and kinetic aspect, Langmuir maximum adsorption capacity of sulphuric acid modified Cassia fistula seeds was 182.2 (mg/g); obeyed Pseudo first order kinetic model. The Ni(II) ion adsorption system undergoes chemisorption, exothermic, feasible and spontaneous. The excellent properties of the Cassia fistula seeds can be alternate for commercial activated carbon. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pyrolysis of heavy metal(loid) contaminated A. marina biomass was conducted. • Cd was highly volatile while Fe and Cu were non-volatile elements. • Biochars from contaminated biomass showed low environmental risk. • Pyrolysing contaminated biomass at 400–500 °C posed minimal environmental impact. Abstract Slow pyrolysis of heavy-metal(loid)-contaminated Avicennia marina biomass obtained from phytoremediation was conducted to investigate the deportment of 12 heavy metal(loid)s in pyrolysis products (biochar, bio-oil, gas) at temperatures from 300 to 800 °C. The results indicated that different heavy metal(loid)s showed diverse volatilities, while all elements tended to transform into volatile products with the increase of pyrolysis temperature. Cd was found highly volatile, while Fe and Cu were non-volatile elements. The leaching analysis of biochars showed that pyrolysis was effective in reducing the mobility and bioavailability of the heavy metal(loid)s in biochars. Moreover, the risk assessment of biochars showed that the biochars derived from polluted biomass can be used as a potential soil amendment. Considering the energy consumption and risk of contaminant emission, pyrolysis temperatures of 400 to 500 °C were considered to be the optimum option for pyrolysis of this biomass. [ABSTRACT FROM AUTHOR]

Highlights • Acid-tolerant microalgae (AM) tolerated heavy metals (HMs) at pH 3.5. • Specific growth rate in AM increased in cultures grown on Mn and Zn. • Cellular analysis revealed the predominant intracellular accumulation of HMs. • Biodiesel production increased in HMs-grown AM at acidic pH. • First report on HMs removal and biodiesel production by AM at pH 3.5. Abstract Metals in traces are vital for microalgae but their occurrence at high concentrations in habitats is a serious ecological concern. We investigated the potential of two acid-tolerant microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, isolated from neutral environments, for simultaneous removal of heavy metals such as copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), and production of biodiesel when grown at pH 3.5. Excepting Cu, the selected metals at concentrations of 10–20 mg L−1 supported good growth of both the strains. Cellular analysis for metal removal revealed the predominance of intracellular mechanism in both the strains resulting in 40–80 and 40–60% removal of Fe and Mn, respectively. In-situ transesterification of biomass indicated enhanced biodiesel yield with increasing concentrations of metals suggesting that both these acid-tolerant microalgae may be the suitable candidates for simultaneous remediation, and sustainable biomass and biodiesel production in environments like metal-rich acid mine drainages. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SRT significantly influenced the ARGs fate in different configurations. • The role of SRT on the ARGs fate varied from ARG types and reactor configurations. • Shorter SRT availed the ARGs reduction for CK and two-stage digestion. • One-stage digestion of pretreated sludge need longer SRT for the ARGs reduction. • Co-selection from heavy metals contributed the most to ARGs fate response to SRT. Abstract In this study, three anaerobic digestion experiments were established to investigate the effects of solids retention times (SRT) on the fate of antibiotic resistance genes (ARGs) including anaerobic digestion of sewage sludge (CK), one-stage anaerobic digestion of microwave pretreatment sludge (MW) and two-stage anaerobic digestion of microwave pretreatment sludge (Acid stage and CH 4 stage). The response of ARGs to the SRT varied significantly from ARG types and reactor configurations. Shorter SRT could avail the ARGs reduction for CK and two-stage digestion, while MW need longer SRT for the ARGs reduction. Concerning the variance of microbial community caused by reactor configurations, the role of SRT was limited. The partial redundancy analysis and structural equation models analysis indicated that the role of SRT on the ARGs fate could be attributed the most to the co-selection from heavy metals. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydrothermal treatment (HT) is effective to remove lincomycin resistance genes. • Mobile genetic elements (MGEs) were also reduced efficiently during HT. • The fate of target genes was described using biphasic first-order kinetic model. • Heavy metals transformed from weakly bounded to stable state after HT. • Environmental risk of heavy metals was declined after HT. Abstract In this study, fate of antibiotic resistance genes (ARGs – lmr A, lmr B, erm B, lnu A, lnu B and vga C) and species distribution of heavy metals during lincomycin mycelial residues hydrothermal treatment (HT) process were investigated. The results showed that HT could reduce both ARGs and mobile genetic elements effectively by 1.02 to 4.14 logs. Total bacterial biomass reflecting by 16S rRNA decreased from 1.27 × 109 to 4.47 × 105 copies g−1 dry weight. Moreover, half-lives of these targets varied from 2.4 min (erm B) to 8.9 min (lmr B) in the first 30 min of treatment based on a biphasic first-order kinetic model. After the first 30 min, however, half-lives ranged between 15.4 min (lmr A) and 247.6 min (ISCR 1). Complexation and precipitation resulted in the transformation of heavy metals from weakly bounded to relatively stable fraction in HT process. Simultaneously, their environmental risk level decreased by at least one grade. [ABSTRACT FROM AUTHOR]

Highlights • Oiltea shell was used to adsorb Cu2+, Pb2+, and Cd2+. • Isotherm, kinetic, and thermodynamic were fitted. • Column adsorption was performed with single and tertiary solution. • Maximum adsorption capacity was obtained in batch and column study. • Adsorption of dye and metal ions was performed in their mixtures. Abstract Agro-processing waste oiltea shell (OTS) has been previously proven effective in removing dye from water by adsorption. This study further evaluated its capability to adsorb heavy metals in aqueous solution. Adsorbent dosage, pH, ion concentration, temperature, and contact time were investigated in batch experiments. Pseudo-second order kinetic better described the adsorption process for the three ions. Langmuir equation was more suitable for Cu2+ and Cd2+, while Freundlich for Pb2+. The maximum adsorption capacity was 22.4 (Pb2+), 12.1 (Cu2+), and 14.2 mg/g (Cd2+), respectively. The adsorption was spontaneous and endothermic. Adsorption was then performed in column and Thomas model was fitted, based on which the maximum adsorption capacity was 7.42 (Cu2+), 4.17 (Pb2+), and 18.02 mg/g (Cd2+), respectively. High removal rate of metal ions and dye methylene blue was also achieved from their mixture solution. OTS is therefore a promising biosorbent in treating wastewater with organic and inorganic pollutants. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A high yield of biochar being rich of ash and C–O groups was derived from SMD. • HCl, NH 3 ·H 2 O and KMnO 4 modification increased the S BET and total pore volume of BC. • HCl-BC, NH 3 -BC and Mn-BC were all negative charged while the original BC was positive. • The ash of BC demonstrated great efforts to adsorb Cu and As. • Mn-BC had the best potentiality in the removals of Cu, Zn, As, SDM, ROX and TYL. Abstract Swine manure digestate (SMD) is rich of functional groups. In this work, raw biochar (BC) was prepared from SMD by oxygen-limiting pyrolysis, and HCl-BC, NH 3 -BC and Mn-BC were obtained by modifying BC with HCl, NH 3 ·H 2 O and KMnO 4. The modified biochar was negatively charged and showed a larger specific surface area and total pore volume, and higher contents of Si–O–Si and O–H bonds and aromatic rings with C O bond. Among them, Mn-BC, was given a new Mn–O group. The adsorption capacities of biochar were determined using a model aqueous solution containing some metals and antibiotics. The adsorption experiment results showed that Mn-BC had a quite good capacity for Cu and Zn removal. And the removal efficiency of As (III), sulfadimidine and tylosin of 83.98%, 83.76%, and 77.34% respectively, was also observed by using Mn-BC. Mn-BC was considered to be a promising material for the adsorption of heavy metals and antibiotics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Adaptability of anammox granules to Zn(II) shock was promoted by NaAc treatment. • SAA recovery efficiency was enhanced by NaAc treatment at 200 mg COD/L for 2 d. • EPS increased and heterotrophic bacteria proliferated in NaAc-treated granules. • EPS and heterotrophic bacteria had barrier roles in protecting anammox bacteria. • Insufficient/excessive NaAc treatment did not lead to desirable protection effects. Abstract Heavy metals, which are commonly present in high ammonia-containing wastewater, can cause inhibitory effects to anammox reaction. This study proposes a novel approach to enhance the adaptability of anammox granules to heavy metal [Zn(II)] shock by organic carbon (sodium acetate, NaAc) treatment, paying special attention to optimization of the treatment dosage and duration. For granules treated with 200 mg chemical oxygen demand (COD)/L NaAc for 2 d, the activity recovery (six cycles) efficiency after Zn(II) (40 mg/L) shock reached 127.4%. The extracellular polymeric substance (EPS) production increased by 168% and heterotrophic bacteria mildly proliferated (increased by 14%) in such granules compared with the control. The dramatic recovery capacity was likely due to the entrapment and barrier function of EPS and the outer-layer proliferated heterotrophic bacteria. This finding offers a useful process to enable maximum adaptability of anammox granules from heavy metals shocks, allowing anammox technology to be more widely applied. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Co-hydropyrolysis (co-HyPy) of biomass and coal is reported for the first time. • Synergies are found to be present during co-HyPy of rise husk and bituminous coal. • Co-HyPy produces more light aromatics and less acids. • Heavy tar formed from co-HyPy has higher aromaticity and more alkyl side-chains. Abstract The hydropyrolysis/co-hydropyrolysis of rice husk (RH) and thermoplastic bituminous coal (BC) was carried out using a fixed-bed reactor to investigate the effects of atmosphere and hydrogen pressure on product distributions. RH produced more carbon oxides, phenolics and acids. BC yielded more methane and BTX (benzene, toluene and xylene) during hydropyrolysis. Compared with hydropyrolysis of RH, the co-hydropyrolysis promoted the higher heating value of gaseous product and the yield of BTX by 19% and 57% respectively, while it reduced the yield of corrosive acids by 89% under 5 MPa H 2. The yields of methane, BTX and phenolics during co-hydropyrolysis were 1.5, 6.4 and 4.0 times as much as those obtained during co-pyrolysis under 5 MPa. The co-hydropyrolysis reformed the structure of heavy oil/tar, benefiting the development of aromaticity. High hydrogen pressure synergistically reduced yields of char and acids, and enhanced yields of tar and light aromatics via the secondary reactions. [ABSTRACT FROM AUTHOR]

Highlights • The short-term effects of Ni and Zn on anammox biomass were determined. • Several inhibition models were tested to evaluate inhibition. • The degree of inhibition was evaluated based on bioavailable fractions. • Candidatus Kuenenia was the dominant anammox-related organism in the samples. Abstract This study provides insight into the short-term effects of nickel and zinc on anammox. The impacts of these heavy metals are evaluated based on their potentially bioavailable fractions, including the intracellular, surface-bound, soluble, free-ion, and weak (labile) complexes of heavy metals, in the presence of certain inorganic/organic species. Results showed that the IC50 values for soluble, intracellular, cell-associated, surface-bound, and free-ion Ni concentrations are 5.99, 0.250, 0.930, 0.680, and 1.36 mg/L, respectively. The inhibitory effect of Zn is found to be lower with respect to Ni, with IC50 values of 6.76, 11.9, 15.1, and 2.71 mg/L for the soluble, intracellular, cell-associated, and free-ion Zn concentrations, respectively. This is the first detailed evaluation of anammox inhibition based on the fractionation of heavy metals. Metagenomic analysis reveals that Candidatus Kuenenia constitute approximately 89% of the entire Planctomycetes population, whereas Candidatus Brocadia are detected in relatively low fractions (3%). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydrolyzing olive cake reduced amounts of water soluble compounds. • The material showed the greatest affinity for lead and the lowest for manganese. • A two-step process is a proper system for mining wastewater depuration. • Combining precipitation and biosorption showed to be a good alternative. • The use of flocculants is highly recommended in the precipitation step. Abstract The present study aims to solve two major challenges of the current society. On the one hand, it investigated the heavy metal removal from mining wastewater. On the other hand, it proposed an alternative use for olive cake. Firstly, a physic-chemical characterization of real wastewater and hydrolyzed olive cake was carried out. Secondly, a study of the affinity of the material for the different metals (chromium, manganese, copper, zinc, nickel and lead) was performed. The hydrolyzed olive cake showed a low content in ash (3.08%) and in water-soluble compounds (2.80%). The material presented the highest retention capacity for the lead (41.54 mg/g) and the lowest for the manganese (3.57 mg/g). After that, biosorption experiments in fixed-bed column were carried out using mining real water. In order to improve the biosorption capacity, the water pH was raised up to 6. The results were quite satisfactory with respect to others similar studies. [ABSTRACT FROM AUTHOR]

Co-hydrothermal carbonization (HTC) of lignocellulosic biomass and swine manure (SM) was conducted, and the hydrochar properties and transformation behavior of heavy metals (HMs) were investigated in this study. The results showed that co-HTC with lignocellulosic biomass promoted the dehydration of SM and enhanced the aromatization of the hydrochar. Compared to the hydrochar from SM, the carbon content, higher heating value and energy yield of the hydrochar from co-HTC were significantly increased, reaching the maximum of 57.05%, 24.20 kJ/kg and 80.17%, respectively. Significant synergy occurred between lignocellulosic biomass and SM during co-HTC and different lignocellulosic biomass exhibited similar influence on the synergy. Additionally, the concentration and bioavailability of HMs in the hydrochar from co-HTC were decreased in comparison to SM. These findings suggested that co-HTC with lignocellulosic biomass offered an effective approach to convert SM into clean solid fuel with remarkably improved fuel properties. [ABSTRACT FROM AUTHOR]

The discrepant fate of antibiotic resistance genes (ARGs) in sludge and water phases was investigated in a municipal wastewater treatment plant, and a lab-scale A 2 O-MBR was operated to provide background value of ARGs. The influencing factors of ARGs including microbial community, co-selection from heavy metals, biomass and horizontal gene transfer were concerned. Results showed that iA 2 O (inversed A 2 O) showed better ARGs reduction, and longer SRT (sludge retention time) increased ARGs relative abundance while reduced the gene copies of ARGs in the effluent, but significantly increased the ARGs in sludge phase. Compared to background value, the most enriched ARG was tetX in water phase, while it was intI1 in sludge phase. There existed higher abundance of multi-resistant bacteria in sludge phase, and microbial community determined the fate of ARGs in both water and sludge phase, while the direct effects from horizontal gene transfer should not be overlooked especially in water phase. [ABSTRACT FROM AUTHOR]

The effect of static magnetic field (SMF) on Spirulina platensis growth and its influence on cadmium ions (Cd 2+ ) removal efficiency were studied. Application of 6 h day −1 SMF resulted in the highest significant biomass productivity of 0.198 g L −1  day −1 . However, 10 and 15 mg L −1 of Cd 2+ resulted in significant reduction in biomass productivity by 8.8 and 12.5%, respectively, below the control. Combined SMF showed 30.1% significant increase in biomass productivity over the control. On the other hand, increase of initial Cd 2+ concentration resulted in significant reduction of Cd 2+ removal efficiency, representing 79.7% and 61.5% at 10 and 15 mg L −1 , respectively, after 16 days. Interestingly, application of SMF for 6 h day −1 enhanced Cd 2+ removal efficiency counted by 91.4% and 82.3% after 20 days for cultures with initial Cd 2+ concentration of 10 and 15 mg L −1 , representing increase by 6.3 and 25.3%, respectively, over the SMF-untreated cultures. [ABSTRACT FROM AUTHOR]

[Display omitted] • CP promoted Cu and Ni immobilization via the complexation with humic acid. • Zn 5 (CO 3) 2 (OH) 6 and CaZn 2 (PO 4) 2 formation was the key reason for Zn passivation. • 10 % CP was the most effective dosage in removal of ARGs and MGEs. • The reduction of MGEs was the key factor for the decrease of ARGs with CP addition. • CP addition could simultaneously reduce the spread risk of HMs and ARGs. This research evaluated the effects of calcium peroxide (CP) at 0% (CK, w/w), 5% (T1, w/w), and 10% (T2, w/w), on heavy metals (HMs) mobility and prevalence of antibiotic resistance genes (ARGs) during sludge composting. T1 and T2 significantly reduced (p < 0.05) the mobility of Cu (29.34%, and 32.94%, respectively), Ni (24.07%, and 31.48%, respectively) and Zn (33.28%, and 54.11%, respectively) compared to CK after the composting. CP addition resulted in a decrease in mobile genetic elements (MGEs) and ARGs during composting. Together with structural equation model and random forest analysis depicted MGEs had a primary association with total ARGs variations during composting. Microbial analysis indicated CP downregulated the expression of the genes associated with two-component and type IV secretion system, thus reducing the prevalence of ARGs. This study demonstrates that application of CP is a feasible strategy to mitigate both ARGs and HMs hazards during composting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four machine learning models are used to predict the adsorption of hydrochar. • Gradient boosting decision tree predicts the best performance with R2 of 0.93–0.98. • The process of heavy metal adsorption by hydrochar is mainly chemisorption. • The range of the C/H/O/N content of the optimal hydrochar is specified. Hydrochar has become a popular product for immobilizing heavy metals in water bodies. However, the relationships between the preparation conditions, hydrochar properties, adsorption conditions, heavy metal types, and the maximum adsorption capacity (Q m) of hydrochar are not adequately explored. Four artificial intelligence models were used in this study to predict the Q m of hydrochar and identify the key influencing factors. The gradient boosting decision tree (GBDT) showed excellent predictive capability for this study (R2 = 0.93, RMSE = 25.65). Hydrochar properties (37%) controlled heavy metal adsorption. Meanwhile, the optimal hydrochar properties were revealed, including the C, H, N, and O contents of 57.28–78.31%, 3.56–5.61%, 2.01–6.42%, and 20.78–25.37%. Higher hydrothermal temperatures (>220 °C) and longer hydrothermal time (>10 h) lead to the optimal type and density of surface functional groups for heavy metal adsorption, which increased the Q m values. This study has great potential for instructing industrial applications of hydrochar in treating heavy metal pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr6+ caused a greater reduction in NRR than other five heavy metals. • The inhibitory effect of heavy metals was verified by Spearman and RDA analysis. • Compared with SVR model, XGBoost model has the best performance with R2 of 0.999. • The effects of multiple heavy metal coexistence on NRR were analyzed by SHAP method. In this study, machine learning algorithms and big data analysis were used to decipher the nitrogen removal rate (NRR) and response mechanisms of anammox process under heavy metal stresses. Spearman algorithm and Statistical analysis revealed that Cr6+ had the strongest inhibitory effect on NRR compared to other heavy metals. The established machine learning model (extreme gradient boost) accurately predicted NRR with an accuracy>99%, and the prediction error for new data points was mostly less than 20%. Additionally, the findings of feature analysis demonstrated that Cu2+ and Fe3+ had the strongest effect on the anammox process, respectively. According to the new insights from this study, Cr6+ and Cu2+ should be removed preferentially in anammox processes under heavy metal stress. This study revealed the feasible application of machine learning and big data analysis for NRR prediction of anammox process under heavy metal stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biochar/montmorillonite acted on heavy metal enrichment by the means of island. • Biochar owned excellent ability of Cu (41.8 mg/kg) and Zn (167.8 mg/kg) enrichment. • Adsorptive passivation of Cu and Zn by bacteria was non-specific and ubiquitous. • DOC, pH and bacteria were critical factors in heavy metal adsorptive inactivation. • Pretreatment of passivators and heavy metal resistant inoculant were necessary. The aim of this study was to assess the effectiveness of biochar and montmorillonite islands on heavy metal adsorptive immobilization and identify crucial driving factors and pathways during chicken manure composting. Compared to montmorillonite (6.74 and 89.25 mg/kg), biochar exhibited an obviously higher ability of Cu and Zn enrichment (41.79 and 167.77 mg/kg), might be attributed to its abundant active functional groups. Network analysis showed that compared to Cu, core bacteria positively and negatively related to Zn was obviously more and less in passivator islands, respectively, which might explain significantly higher Zn concentration. Structural Equation Model displayed that dissolved organic carbon (DOC), pH and bacteria were critical driving factors. Pretreatment of passivator packages, such as soaking in the solution being rich in DOC and inoculating specific microbial agents accumulating heavy metals via extracellular adsorption /intracellular interception would significantly improve the effectiveness of adsorptive passivation on heavy metals. [ABSTRACT FROM AUTHOR]

Schematic for synthesis and application of MBCs. [Display omitted] • The porous MBCs were prepared by one-step KOH-activated pyrolysis. • The effects of impregnation ratio on magnetic biochar activated by KOH were investigated. • Three common agricultural wastes were prepared as MBCs for contaminant removal. • WS-0.3 showed an adsorption capacity of up to 405.01 mg g−1 for tetracycline. • RH-0.6 and CS-0.6 were superior in removing heavy metal ions. The effect of iron impregnation ratio on magnetic biochars (MBCs) prepared by biomass pyrolysis accompanied by KOH activation has been less reported. In this study, MBCs were produced by one-step pyrolysis/KOH-activation of walnut shell, rice husk and cornstalk with different impregnation ratios (0.3–0.6). The properties, adsorption capacity and cycling performance for Pb(II), Cd(II) and tetracycline of MBCs were determined. MBCs prepared with low impregnation ratio (0.3) showed stronger adsorption capacity on tetracycline. The adsorption capacity of WS-0.3 toward tetracycline was up to 405.01 mg g−1, while that of WS-0.6 was only 213.81 mg g−1. It is noteworthy that rice husk and cornstalk biochar with an impregnation ratio of 0.6 were more effective in removing Pb(II) and Cd(II), and the content of Fe0 crystals on surface strengthened the ion exchange and chemical precipitation. This work highlights that the impregnation ratio should be changed according to the actual application scenarios of MBC. [ABSTRACT FROM AUTHOR]

Two eco-friendly nanosorbents have been designed and synthesized via surface crosslinking of nanosilica (N-Si) with glycine (Gly) and reduced glutathione (GSH) to produce (N-Si-Gly) and (N-Si-Glu) using crosslinking reagent and sonochemical reactions, respectively. An investigation was performed to search selectivity of nanosorbents via microwave-assisted removal of Ni(II)/Cu(II)/Cd(II)/Pb(II) to affirm green and fast technique. The microwave-assisted removal values of Ni(II), Cu(II), Cd(II) and Pb(II) were observed at 850, 2100, 3500 and 2150 μmol g −1 , respectively utilizing 10 mg of (N-Si-Glu) and 25.0 s heating, while those corresponded to 750, 1800, 2500 and 1850 μmol g −1 , respectively by using (N-Si-Gly). The microwave-assisted removal processes were more fitted to Freundlich compared to Langmuir isotherm except in case of Pb(II). The high percent removal of Cd(II) and Pb(II) ions exceed 95% from the second run in real wastewater samples indicating the efficiency of N-Si-Glu in the uptake of these metals utilizing microwave-assisted sorption technique. [ABSTRACT FROM AUTHOR]

Vanadium (V) is a common heavy metal and often co-occurs with nitrate in effluents from mining and metal finishing industry. In the present study, the toxic effects of V(V) were examined in a sulfur and hydrogen based autotrophic denitrification system. This combined system achieved simultaneously microbial denitrification and V(V) reduction. High concentration of V(V) (60 and 100 mg/L) inhibited the denitrification activities, while 30 mg/L V(V) had a very slight effect. V(V) induced increases of lactate dehydrogenase release and reactive oxygen species production, which may inhibit nitrate and nitrite reductases activities and abundances of denitrifying functional genes. Moreover, the extracellular polymeric substance production was also suppressed under V(V) stress, thereby decreasing the amount of biofilm biomass. Microbial community analyses suggesting the genus Bacillus may have higher tolerance to V(V). These findings can provide scientific basis for the optimized design of treatment system to remove nitrate and V(V) simultaneously. [ABSTRACT FROM AUTHOR]

This work represents a comparative uptake study of the toxic elements arsenic, boron, copper, manganese and zinc in monometallic and multimetallic solutions by four green microalgae species ( Chlamydomonas reinhardtii , Chlorella vulgaris , Scenedesmus almeriensis and an indigenous Chlorophyceae spp.), evaluating the effect of pH and contact time. Maximum removal efficiencies for each toxic element were 99.4% for Mn ( C. vulgaris , pH 7.0, 3 h), 91.9% for Zn ( Chlorophyceae spp., pH 5.5, 3 h), 88% for Cu ( Chlorophyceae spp., pH 7.0, 10 min), 40.7% for As ( S. almeriensis , pH 9.5, 3 h) and 38.6% for B ( S. almeriensis , pH 5.5, 10 min). B removal efficiencies decreased remarkably in multimetallic solutions (down to 0.2% in C. reinhardtii ), except for Chlorophyceae spp., the only species isolated from a polluted environment. FTIR spectra shown the highest interactions for As (1150–1300 cm −1 ) and Cu (3300, 1741, 1535, 1350–1400 cm −1 ). Results confirm microalgae biomass as a potential biosorbent for toxic elements. [ABSTRACT FROM AUTHOR]

This study reports the facile synthesis of cubic spinel-type manganese ferrite (MnFe 2 O 4 )/biochar (MF/BC) composites via a one-pot hydrothermal technique. Multiple characterizations demonstrated that the MnFe 2 O 4 spinel nanoparticles were successfully grown on the biochar, which provides magnetic separability with superparamagnetic behavior and effective adsorption performance for heavy metals (Pb(II), Cu(II), and Cd(II)). The adsorption kinetics and isotherms can be well described with a pseudo-second-order and Sips isotherm models, respectively. Comparative adsorption in multi-heavy metal systems (binary and ternary) indicated that the adsorption affinity of MF/BC composites toward heavy metals followed the sequence of Pb(II) > Cu(II) > Cd(II), which followed the order of their covalent indexes. Thermodynamic analysis revealed that the adsorption process was endothermic and primarily governed by physisorption. This study provides a feasible and simple approach for the preparation of high-performance materials for the remediation of heavy metal-contaminated wastewater in a cost-effective manner. [ABSTRACT FROM AUTHOR]

This research aims to provide a better knowledge of the thermal decomposition of the olive cake as well as this lignocellulosic material loaded, in a previous stage of biosorption, with heavy metals for its use in processes of energy recovery. Firstly, isolation of constituents of the olive cake was carried out. Then, experiments were performed by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) under inert and oxidative atmosphere at a heating rate of 15 K/min for each isolated fraction. Next, adequate reactions schemes were proposed to find kinetic parameters. Validation of these schemes were verified by the goodness of fitting between experimental and simulated data. Also, some important combustion characteristics such as ignition and burnout temperatures were determined. With regard to the effect of metals, cadmium, copper, chromium, nickel and lead present in metal-loaded olive cake did not modify values of kinetic parameters which described the thermal decomposition processes. [ABSTRACT FROM AUTHOR]

Chitosan modified magnetic kelp biochar (Chi-KB m ) was successfully synthesized for efficient removal of heavy metals (Cu 2+ ) from wastewater. Interestingly, the characterization results indicated that Chi-KB m showed 6 times higher surface area (6.17 m 2 /g) than the pristine magnetic kelp biochar KB m (0.97 m 2 /g). In addition, new functional groups, such as NH and C N group, have been created on the surface of biochar as a result of chitosan modification process, which in turns led to improve the Cu 2+ adsorption capacity. The effect of pH and chitosan loading on heavy metal adsorption, and competition reaction of different metal ions adsorption were also investigated. Chi-KB m exhibited a separation efficiency of more than 99.8%, which allows to recovery and reusability of the adsorbent material and heavy metals simultaneously. Overall, this study highlighted the Chi-KB m is a promise adsorbent for heavy metal removal without sacrificing of the separation ability using magnetism. [ABSTRACT FROM AUTHOR]

In order to improve the adsorption capacities of corncob-based biochars for heavy metal, the different pyrolysis temperature (350 °C, 450 °C and 550 °C) of corncob-based biochars were modified with the acrylonitrile, and adsorption capacities of Cadmium from solution by biochars were studied. The results showed that only at 350 °C the biochar can be successfully modified. The Cd adsorption capacity (85.65 mg/g) by the biosorbent was higher than other methods of modifying biochars previously reported. SEM-EDS and FTIR confirmed that the C N group was grafted on the biochar at low pyrolysis temperature. Batch adsorption experiment including pH-dependence, adsorption kinetics, and isotherms and XPS results showed that the removal mechanism of Cd(II) by the modified biochar was ion exchange and adsorption-complexation. This research not only obtained a novel method to modify biochar but also furthered research into the lignin of biochar composition, and provided an efficient sorbent for heavy metal. [ABSTRACT FROM AUTHOR]

Co-liquefaction of municipal sewage sludge (MSS) and heavy metal (HM) contaminated lignocellulosic biomass (rice straw or wood sawdust) was conducted at 300 °C with ethanol as the solvent to study the transformation behavior of HMs (e.g., Cu, Cd, Pb, Cr, Zn, and Ni). The results indicate that HMs in rice straw or wood sawdust transferred heavily to bio-oils (up to 10–25% of the total Cu, Cd, and Zn) when they were liquefied individually, compared with MSS with only ∼5% distributed to bio-oil. The bio-available fraction of HMs in bio-chars and bio-oils produced from liquefaction of individual biomass were assessed to show medium to high risk to the environment. Co-liquefaction promoted the distribution of HMs to solid bio-char. Moreover, co-liquefaction benefited the immobilization of HMs in bio-chars and bio-oils. Synergistic effects were found for HMs immobilization during co-liquefaction. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of pyrolysis on the stabilization of heavy metals in plant residues obtained after phytoremediation. Ramie residues, being collected after phytoremediation of metal contaminated sediments, were pyrolyzed at different temperatures (300–700 °C). Results indicated that pyrolysis was effective in the stabilization of Cd, Cr, Zn, Cu, and Pb in ramie residues by converting the acid-soluble fraction of metals into residual form and decreasing the TCLP-leachable metal contents. Meanwhile, the reutilization potential of using the pyrolysis products generated from ramie residues obtained after phytoremediation as sorbents was investigated. Adsorption experiments results revealed that the pyrolysis products presented excellent ability to adsorb methylene blue (MB) with a maximum adsorption capacity of 259.27 mg/g. This study demonstrated that pyrolysis could be used as an efficient alternative method for stabilizing heavy metals in plant residues obtained after phytoremediation, and their pyrolysis products could be reutilized for dye adsorption. [ABSTRACT FROM AUTHOR]

Continuous copper biosorption in fixed-bed column by olive stone and pinion shell was studied. The effect of three operational parameters was analyzed: feed flow rate (2–6 ml/min), inlet copper concentration (40–100 mg/L) and bed-height (4.4–13.4 cm). Artificial Neural-Fuzzy Inference System (ANFIS) was used in order to optimize the percentage of copper removal and the retention capacity in the column. The highest percentage of copper retained was achieved at 2 ml/min, 40 mg/L and 4.4 cm. However, the optimum biosorption capacity was obtained at 6 ml/min, 100 mg/L and 13.4 cm. Finally, breakthrough curves were simulated with mathematical traditional models and ANFIS model. The calculated results obtained with each model were compared with experimental data. The best results were given by ANFIS modelling that predicted copper biosorption with high accuracy. Breakthrough curves surfaces, which enable the visualization of the behavior of the system in different process conditions, were represented. [ABSTRACT FROM AUTHOR]