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Elevated concentrations of antimony (Sb) in the ecological environment have received considerable attention due to the harmful consequence involved. This study synthesized sulphidated ferrihydrite with different S:Fe molar ratios to efficiently remove Sb(V) from water. As the S:Fe molar ratio ranged from 0.00 to 1.48, the removal efficiency of Sb(V) by sulphidated ferrihydrite first decreased before increasing considerably. Sulphidated ferrihydrite with an S:Fe molar ratio of 0.74 exhibited a strong affinity towards Sb(V) with an optimal removal capacity of 963.74 mg Sb/g, which was 3.2−fold higher than that of ferrihydrite. In the kinetic experiments, the removal behavior of Sb(V) was well described by the pseudo−second−order model, suggesting that the removal process was controlled via chemisorption. Moreover, Sb(V) was efficiently removed over a wide pH range of 3.00–11.00, and coexisting anions (NO 3 −, Cl−, SO 4 2−, SiO 3 2−, CO 3 2− and PO 4 3−) exhibited marginal impact on the Sb(V) removal by sulphidated ferrihydrite (S:Fe ≥ 0.44). The characterization results of XRD, SEM, TEM mapping and etched XPS revealed goethite to be the dominant phase of sulphidated ferrihydrite with an S:Fe molar ratio of 0.15, while a mixed constitution of mixed−valent iron (hydro)oxides and iron sulphide was formed when the S:Fe molar ratio exceeded 0.44. Moreover, sulphidated ferrihydrite acted as a donor for Fe and S for the effective retention of Sb(V) by two main pathways: precipitation (tripuhyite, FeSbO 4) and complexation (≡S–H and ≡Fe–OH). Therefore, sulphidated ferrihydrite is a promising material for eliminating Sb(V) contamination from water. • Sulphidated ferrihydrite was fabricated and applied to remove Sb(Ⅴ) from water. • The S:Fe molar ratio had significant effect on the removal efficiency of Sb(Ⅴ). • Partial dissolution of sulphidated ferrihydrite accelerated the formation of FeSbO 4. • Sulphidation enhanced Sb(Ⅴ) removal mainly through precipitation and complexation. [ABSTRACT FROM AUTHOR]

Phosphorus-modified biochar has been proven to enhance the precipitation and complexation of heavy metal ions from wastewater. However, the current modification methods require large amounts of exogenous P and have high energy consumption. Hence, this study proposes and analyzes a strategy integrating biochar production, phosphorus wastewater treatment, dephosphorization waste recovery, and heavy metal removal. "BC-Ca-P" was derived from Ca-modified biochar after phosphorus wastewater treatment. The adsorption of Pb(II) by BC-Ca-P followed the Langmuir isotherm and pseudo–second–order kinetic models. The maximum adsorption capability of 361.20 mg·g−1 at pH 5.0 for 2 h was markedly greater than that of external phosphorous-modified biochar. The adsorption mechanisms were dominated by chemical precipitation and complexation. Furthermore, density functional theory calculations indicated that oxygen-containing functional groups (P-O and C-O) contributed the most to the efficient adsorption of Pb(II) onto BC-Ca-P. To explore its practical feasibility, the adsorption performance of BC-Ca-P recovered from an actual environment was evaluated. The continuous-flow adsorption behavior was investigated and well-fitted utilizing the Thomas and Yoon–Nelson models. There was a negligible P leakage risk of BC-Ca-P during heavy metal treatment. This study describes a novel and sustainable method to utilize dephosphorization waste for heavy metal removal. Article Highlights: Dephosphorization biochar waste was used to sustainably remove heavy metals from wastewater. Field-recovered dephosphorization biochar waste displayed high Pb adsorption capacity. Dephosphorization biochar for heavy metal removal is an eco–friendly waste–reduction and resource–utilization method. [ABSTRACT FROM AUTHOR]

Abstract\nSTATEMENT OF NOVELTYSoil heavy metal contamination and sludge disposal have become globally environmental issues problems of great concern. Utilizing sludge pyrolysis to produce biochar for remediating heavy metal-contaminated soil is an effective strategy to solve these two environmental problems. In this study, municipal sewage sludge and papermaking sludge were used as feedstock to prepare co-pyrolyzed biochar, which was then applied to reduce the toxicity of Cd in soil. The results indicated that the application of co-pyrolyzed biochar significantly increased soil pH, CEC, and enzyme activity, while decreasing the content of available Cd in the soil. Following the application of 3% co-pyrolyzed biochar, the proportion of acid-soluble Cd in the soil decreased to below 46%, as the biochar facilitated the conversion of leachable acid-soluble Cd to stable oxidizable and residual forms through precipitation and complexation. The DFT computational results indicate that the aromatics in co-pyrolyzed biochar can adsorb Cd ions through cation-π interactions, while carboxyl, hydroxyl, aldehyde, and amide groups can provide more electrons for the adsorption of Cd ions, resulting in stronger adsorption capacities. The study findings provide a feasible solution for the resourceful treatment of sludge and the remediation of heavy metal-contaminated soil.This study is the first to investigate the remediation potential of municipal sludge and papermaking sludge co-pyrolyzed biochar for Cd-contaminated soil. Additionally, density functional theory (DFT) calculations were employed to elucidate the microscopic adsorption mechanisms of Cd ions by the co-pyrolysis biochar. These findings provide a theoretical foundation for the resource utilization of sludge and the development of cost-effective soil remediation agents. [ABSTRACT FROM AUTHOR]

• Rice straw-derived dissolved organic matter (DOM) included four main components. • The presence of goethite significantly promotes the straw decomposition process. • OM's adsorption capacity for Cd increased with the straw decomposition time. • The presence of minerals promoted the OM's adsorption capacity and affinity of Cd. • Surface precipitation and complexation dominant Cd adsorption by OM. Organic matter (OM) derived from the decomposition of crop residues plays a key role as a sorbent for cadmium (Cd) immobilization. Few studies have explored the straw decomposition processes with the presence of minerals, and the effect of newly generated organo-mineral complexes on heavy metal adsorption. In this study, we investigated the variations in structure and composition during the rice straw decomposition with or without minerals (goethite and kaolinite), as well as the adsorption behavior and mechanisms by which straw decomposition affects Cd immobilization. The degree of humification of extracted straw organic matter was assessed using excitation-emission matrix (EEM) fluorescence and Ultraviolet-visible spectroscopy (UV-vis), while employing FTIR spectroscopy and XPS to characterize the adsorption mechanisms. The spectra analysis revealed the enrichment of highly aromatic and hydrophobic components, indicating that the degree of straw decomposition and humification were further intensified during incubation. Additionally, the existence of goethite (SG) accelerated the humification of OM. Sorption experiments revealed that the straw humification increased Cd adsorption capacity. Notably, SG exhibited significantly higher adsorption performance compared to the organic matter without minerals (RS) and the existence of kaolinite (SK). Further analysis using FT-IR spectroscopy and XPS verified that the primary mechanisms involved in Cd immobilization were complexion with —OH and —COOH, as well as the formation of Cd-π binds with aromatic C=C on the surface of solid OMs. These findings will facilitate understanding the interactions of the rice straw decomposing with soil minerals and its remediation effect on Cd-contaminated farmland. [Display omitted] [ABSTRACT FROM AUTHOR]

In view of the treatment of heavy metal wastewater of[ Cd (II) ], [ Cr (VI) ] and[ Pb (II) ], this study modified nano-zero-valent iron (nZVI) by bioehar (BC) and bentonite (BE) to obtain BC-BE-NZVI composite material, and explored the adsorption characteristics of the material for heavy metals through ad-sorption experiments. Adsorption kinetics equation, isothermal adsorption equation fitting, XRD and XPS analysis were used to reveal the adsorption mechanism of BC-BE-nZVI on single and compound heavy metal systems. The results show that BC-BE-nZVI has the strongest effect on the removal of heavy metals, and the removal rate of Cd (II), Cr (VI) and Pb (II) can reach 96. 43%, 97.70% and 95. 69% /respectively, and can adapt to heavy metal wastewater with a wide pH range. The pseudo-second-order kinetic equation and Langmuir isothermal adsorption equation are more suitable for describing the adsorption process of BC-BE-nZVI. In the compound heavy metal system, the adsorption process of BC-BE-nZVI is more suitable for Freundlich isothermal adsorption equation, and the competitive adsorption capacity Cd (II) is higher than Cr (VI). In a single heavy metal system, the removal mechanism of Cd (II) mainly includes adsorption precipitation, Cr (VI) is mainly reduction and adsorption, and Pb (II) is mainly adsorption precipitation. The adsorption mechanism of the compound heavy metal system is mainly precipitation and complexation. [ABSTRACT FROM AUTHOR]

Biochar-based sulfidized nano-sized zero-valent iron (SNZVI/BC) can effectively immobilize cadmium (Cd) in contaminated paddy soils. However, the synergistic effects between biochar and SNZVI on Cd immobilization, as well as the underlying mechanisms remain unclear. Herein, a soil microcosm incubation experiment was performed to investigate the immobilization performance of SNZVI/BC towards Cd in the contaminated paddy soil. Results indicated that the addition of SNZVI/BC at a dosage of 3% significantly lessened the concentration of available Cd in the contaminated soil from 14.9 (without addition) to 9.9 mg kg−1 with an immobilization efficiency of 33.3%, indicating a synergistic effect. The sequential extraction results indicated that the proportion of the residual Cd in the contaminated soil increased from 8.1 to 10.3%, manifesting the transformation of the unstable Cd fractions to the steadier specie after application of SNZVI/BC. Also, the addition of SNZVI/BC increased soil pH, organic matter, and dissolved organic carbon, which significantly altered the bacterial community in the soil, enriching the relative abundances of functional microbes (e.g., Bacillus, Clostridium, and Desulfosporosinus). These functional microorganisms further facilitated the generation of ammonium, nitrate, and ferrous iron in the contaminated paddy soil, enhancing nutrients' availability. The direct interaction between SNZVI/BC and Cd2+, the altered soil physicochemical properties, and the responded bacterial community played important roles in Cd immobilization in the contaminated soil. Overall, the biochar-based SNZVI is a promising candidate for the effective immobilization of Cd and the improvement of nutrients' availability in the contaminated paddy soil. Highlights: Biochar-based sulfidized nano-sized zero-valent iron (SNZVI/BC) synergistically immobilized Cd in the contaminated soil. SNZVI/BC effectively enhanced nutrients' availability in the contaminated soil. Nitrate-, Iron-, and sulfate-reducing bacteria were enriched in the SNZVI/BC-treated soil. Precipitation and complexation played an important role in the immobilization of Cd. [ABSTRACT FROM AUTHOR]

Shown up is the structure of sulfide-modified nanoscale zerovalent iron (S-nZVI), which was synthesized to enhance Pb(II) removal in aqueous solution, the S-nZVI particles exhibited a core–shell structure, with Fe0 comprising the core and iron oxides in the shell, the generated iron sulfides (FeS x) were distributed over the iron oxides shell. The formation of FeS x caused the material to have irregular surfaces with complex morphology, increasing the specific surface area of S-nZVI, additionally, FeS x could enhance the electron transfer efficiency from Fe0 core to contaminants. Based on SEM, TEM, XRD and XPS analyses, The S-nZVI has been found to enhance the adsorption of Pb(II) through the synergistic effects of electrostatic attraction, chemical precipitation, surface complexation and reduction. [Display omitted] • The sulfide-modified nZVI showed better Pb(II) removal performance than bare nZVI. • S-nZVI had a core–shell structure with Fe0 core and iron oxides in the shell, FeS x was distributed over iron oxides. • FeS x improved the electron transfer efficiency from Fe0 core to contaminants. • The possible mechanisms of Pb(II) removal onto S-nZVI were investigated. Nanoscale zerovalent iron (nZVI) was prone to aggregation and passivation, which limited its application. Here, sulfide-modified nZVI (S-nZVI) was synthesized to enhance Pb(II) removal, the transmission electron microscope and scanning electron microscope showed S-nZVI particles exhibited a core–shell structure, with Fe0 comprising the core and iron oxides in the shell, the generated iron sulfides (FeS x) were distributed over the iron oxides shell. The water contact angle results suggested S-nZVI was more hydrophobic than nZVI, which could prevent the oxidation of the inner Fe0 core with aqueous solution, furthermore, the electrochemical experiments demonstrated the FeS x improved the electron transfer efficiency from Fe0 core to contaminants, enhancing the reactivity of S-nZVI. Mechanism analysis confirmed that the electrostatic attraction, chemical precipitation, surface complexation and reduction occurred during the adsorption. S-nZVI with S/Fe molar ratio of 0.3 offered the best Pb(II) adsorption capacity, and higher pH value was favourable, the presence of co-existing cations (K+, Na+, Ca2+, Mg2+) all interfered the Pb(II) removal, followed as Ca2+ >Mg2+ > K+ > Na+. The pseudo-second-order kinetics and Langmuir model could well described the adsorption process, indicating that monolayer adsorption dominated the process. Thermodynamic results showed the adsorption was a spontaneous endothermic process, even after 4 cycles of recycling, the removal rate remained at 76.4 %, demonstrating S-nZVI had good reusability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cr, Cu, Zn and Cd could be removed simultaneously by nZVI@SBC. • NO 3 – and HA promote the removal of Cr, Cu, Zn and Cd. • Cr and Cu were reduced by nZVI and then removed through co-precipitation. • The removal of Cd and Zn were driven by alkali precipitation and complexation. Cr, Cu, Zn, and Cd commonly coexisted in the electroplating wastewater with high salinity and organics, while their removal was often investigated individually. In this study, the simultaneous removal of Cr, Cu, Zn, and Cd was investigated by nano zero-valent iron modified sludge biochar (nZVI@SBC). The results showed that nZVI@SBC could significantly improve the removal efficiency of the four heavy metals (HMs) in high salinity wastewater. NO 3 – (N-NO 3 –) and humic acid (HA) could promote the removal of Cr, Cu, Zn, and Cd, and PO 4 3- (P-PO 4 3-) could enhance the removal of Cd. EPR analysis demonstrated the generation of 1O 2 in different water matrices. The 1O 2 intensity increased in the presence of NO 3 – and HA, which indicated the acceleration of the nZVI corrosion and the promoted electron transfer in the system. To further understand the reaction mechanism, the variation of nZVI@SBC structures and compositions during the treatment process were characterized by SEM-EDS, XRD, BET, and XPS. Cr and Cu were removed through adsorption and co-precipitation after reduction by nZVI, while Cd and Zn were removed by alkali precipitation and complexation. This work improves the understanding of simultaneous removal of HMs by nZVI@SBC and provides a cost-effective approach for the electroplating wastewater treatment. [ABSTRACT FROM AUTHOR]

Synthesis of metal-doped biochar have gained prominence due to their adsorption capability for heavy metal(loid)s. In this study, iron-doped biochar (Fe-BC) was fabricated through pyrolysis of waste mushroom substrate (WMS) with red mud (RM). The synthesised Fe-BC was employed as an adsorbent for Pb removal. During pyrolysis of WMS, introducing RM contributed to the enhanced syngas formation, this observation was attributed to the catalytic function of Fe species in RM. The Fe–BCs were made at three different temperatures (500, 600, and 700 °C), and their adsorption capabilities for Pb were evaluated. Among the prepared Fe–BCs, Fe-BC fabricated at 700 °C (Fe-BC-700) demonstrated the highest Pb adsorption performance (243.07 mg g−1). This performance primarily stemmed from the presence of zero-valent Fe and surface functional groups (–OH) in Fe-BC-700. Pb removal by Fe-BC-700 was dominated by surface precipitation and complexation mechanisms. Therefore, this study highlights a promising approach for producing an effective adsorbent for Pb removal from industrial wastewater by utilizing wastes such as RM and WMS. [Display omitted] • Iron-biochar composite (Fe-BC) was fabricated from biomass pyrolysis with red mud. • The presence of red mud enhanced the syngas formation during fabrication of Fe-BC • Zero-valent Fe (Fe0) was developed only in Fe-BC fabricated at 700 °C (Fe-BC-700). • Fe-BC-700 adsorbed Pb through surface precipitation and complexation. [ABSTRACT FROM AUTHOR]

[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]

In this study we investigated the efficacy of a novel material parthenium weed (Parthenium hysterophorus L.) biochar (PBC), iron doped zinc oxide nanoparticles (nFe-ZnO), and biochar modified with nFe-ZnO (Fe-ZnO@BC) to adsorb heavy metals (HMs) and reduce their uptake by wheat (Triticum aestivum L.) in a highly chromite mining contaminated soil. The co-application of the applied soil conditioners exhibited a positive effect on the immobilization and restricted the HMs uptake below their threshold levels in shoot content of wheat. The maximum adsorption capacity was because of large surface area, cation exchange capacity, surface precipitation, and complexation of the soil conditioners. The scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed porous smooth structure of parthenium weed derived biochar that helped in HMs adsorption, increase the efficiency of soil fertilizers and nutrients retention which help in the enhancement soil condition. Under different application rates the highest translocation factor (TFHMs) was obtained at 2 g nFe-ZnO rate followed the descending order: Mn > Cr > Cu > Ni > Pb. The overall TFHMs was found <1.0 indicating that low content of HMs accumulation in roots from soil slight transferred to shoot, thus satisfying the remediation requirements. Wheat is considered as an important staple food which is grown in a chromite mining contaminated soil containing toxic HMs releasing from weathering of mafic and ultramafic rocks in the study area. The present research work is significantly beneficial in identifying the efficiency of treatment technologies to immobilize toxic HMs in soil. Parthenium weed derived biochar and biochar modified with nFe-ZnO (Fe-ZnO@BC) reduce the HMs uptake by wheat plant. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-capacity, selective, and recyclable magnetic phosphate composites were prepared. • CaFeP-1 can effectively reduce uranium concentration and also neutralize the acidity of the acidic mining wastewater. • Efficient uranium removal by CaFeP-1 is attributed to dissolution-precipitation, surface complexation, and ion exchange. Uranium mining operations produce large volumes of acidic uranium mining wastewater, necessitating the development of environmentally friendly and recyclable materials for efficient uranium removal and recovery. The current study successfully produced hydroxyapatite (HAP-L) and magnetic phosphate composites (CaFeP-1, CaFeP-2, and FePO 4) through a combination of mixing, ultrasonication, hydrothermal precipitation, and calcination methods. The research explores the influence of various parameters such as pH, solid–liquid ratio, contact time, initial uranium concentration, co-existing ions, and recyclability on the uranium removal efficiency of these materials. The findings indicate exceptional uranium adsorption capacities, with CaFeP-1 exhibiting the highest capacity among the materials, especially in acidic environments. Moreover, CaFeP-1 displays strong resistance to interference from other ions and can be recycled multiple times while maintaining high removal rates. Treatment of acidic uranium mining wastewater by CaFeP-1 results in pH adjustment and the reduction of uranium and other ion concentrations, making it a promising solution for comprehensive remediation of acidic uranium mining wastewater. The U(VI) removal mechanism by CaFeP-1 was validated through XRD, FT-IR, and XPS results. The U(VI) removal was attributed to processes such as dissolution-precipitation, surface complexation, and ion exchange. The formation of sodium uranyl phosphate hydrate was identified as a new product following U(VI) abatement by CaFeP-1. In summary, CaFeP-1 shows great potential for the effective treatment of acidic uranium mining wastewater. [ABSTRACT FROM AUTHOR]

The present investigation applies the stabilization/solidification technique for lead (Pb)-contaminated soil remediation utilizing an organic binder to negate the environmental consequences caused by inorganic binders such as cement. This research synthesized novel biochar by slow pyrolysis of moringa seed cake or de-oiled cake (waste generated after oil recovery) and tested its physicochemical characteristics, which revealed that it possesses a high pH and abundant surface functional groups that can act as potential adsorption sites for lead. Furthermore, the effects of biochar content (0% to 10% w/w) and curing time on the stabilization of soil contaminated with Pb at a concentration of 5,000 mg/kg were evaluated. The toxicity characteristic leaching test showed that treatment with 10% w/w biochar and 28 days of curing reduced Pb leachability to regulatory limits with over 89% immobilization efficiency. Moreover, the soil strength and the pH increased steadily with the biochar content and curing time while maintaining stability after 56 to 90 days of curing. Microstructural characterization revealed the underlying mechanisms in effectively stabilizing lead in soil, including precipitation, surface complexation with functional groups (C═O, O═C─ O), and lead encapsulation in calcium silicate hydrates (C─ S─ H). [ABSTRACT FROM AUTHOR]

Fly ash (FA) is promising for environmental remediation, but how to modify the FA with high remediation efficiency through an environmentally friendly and low-cost modification method is scare. A modified FA (MFA) was prepared through a one-step hydrothermal modification with Ca(OH)2 and KH2PO4. Results indicated that irregular agglomerates occurred on the surface of the MFA and that the specific surface area increased by 1.94 times compared to that of FA. Compared to FA, glassy compositions in MFA were destroyed and amorphous Si/Al and alkaline aluminosilicate gels were formed. The soil application of 0.2–0.6% MFA significantly increased soil pH by 0.23–0.86 units compared to FA and decreased available lead (Pb) and copper (Cu) by 25–97.1% and 13.5–75%, respectively. MFA significantly decreased exchangeable Pb and Cu by 12.5–32% and 11.4–35.2%, respectively, compared to FA. This may be due to the high pH and specific surface area of MFA, which promoted to the formation of amorphous Si/Al, metal–phosphate precipitation, and complexation with functional groups. In addition, MFA slightly increased the biomass of shoots and roots and decreased the uptake of Pb and Cu by ryegrass. This study provides a new modification method for the utilization of FA in the heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

To improve the phosphorus (P) recovery efficiency from livestock wastewater, a novel MgO doped mildewed corn biochar with thermal pre-puffing treatment (Mg-PBC) and without pre-puffing (Mg-BC) was synthesized and tested. The thermal-puffing pretreatment improved the effectiveness of metal soaking and MgO dispersion. P recovery time with Mg-PBC (7 h) was significantly shorter than that with Mg-BC (12 h). Moreover, Mg-PBC showed significantly higher P recovery capacity (241 mg g−1) than Mg-BC (96.6 mg g−1). P recovery capacity of the Mg-PBC fitted to the Thomas model was 90.7 mg g−1, which was 4 times higher than that of Mg-BC (22.9 mg g−1) under column test conditions. The mechanisms involved in P recovery included precipitation, surface complexation, and electrostatic interaction. After adsorption, both Mg-BC and Mg-PBC showed relatively low regeneration abilities. The P loaded Mg-BC (Mg-BC-P) and Mg-PBC (Mg-PBC-P), the later particularly, obviously increased the available P content and promoted plant growth. The release of P increased with time in the Mg-PBC-P treated soil, while it decreased with time in the P fertilizer treated soil. A cost–benefit analysis revealed that thermal-puffing pretreatment greatly increased the profit of MgO doped biochar from −0.66 to 5.90 US$ kg−1. These findings highlight that biomass pre-puffing is a feasible treatment to produce MgO modified biochar and to recover P from livestock wastewater, and that the Mg-PBC-P can be used as a slow-release P fertilizer. Highlights: • MgO doped biochar with (Mg-PBC) and without (Mg-BC) pre-puffing used for P recovery • Thermal puffing improved the efficiencies of metal soaking and MgO dispersion • Mg-PBC showed higher P recovery capacity (241 mg g-1) than Mg-BC (96.6 mg g-1) • Precipitation, complexation, and electrostatic attraction controlled P recovery • Biomass pre-puffing improve P recovery by MgO doped biochar [ABSTRACT FROM AUTHOR]

• Adsorption capacities of Fe/S-BC are improved after Fe/S co-doping. • Fe/S-BC has a high adsorption capacity for As(III) and Pb(II). • The presence of Pb(II) decreased the adsorption capacity of As(III). • The synergistic effects on Pb adsorption were observed in combined pollutants. Simultaneous elimination of As(III) and Pb(II) from wastewater is still a great challenge. In this work, an iron-sulfur codoped biochar (Fe/S-BC) was successfully fabricated in a simplified way and was applied to the remediate the co-pollution of As(III) and Pb(II). The positive enthalpy indicated that the adsorption in As-Pb co-pollution was an endothermic reaction. The mechanism of As(III) removal could be illustrated by surface complexation, oxidation and precipitation. In addition to precipitation and complexation, the elimination mechanism of Pb(II) also contained ion exchange and electrostatic interactions. Competitive and synergistic effects existed simultaneously in the co-contamination system. The suppression of As(III) was ascribed to competitive complexation of the two metals on Fe/S-BC, while the synergy of Pb(II) was attributed to the formation of the PbFe 2 (AsO 4) 2 (OH) 2. Batch experiments revealed that Fe/S-BC had outstanding ability to remove As(III) and Pb(II), regardless of pH dependency and interference by various coexisting ions. The maximum adsorption capacities of the Fe/S-BC for As(III) and Pb(II) were 91.2 mg/g and 631.7 mg/g, respectively. Fe/S-BC could be treated as a novel candidate for the elimination of As(III)-Pb(II) combined pollution. [Display omitted] [ABSTRACT FROM AUTHOR]

To address the issues of ZVI's susceptibility to oxidation and aggregation, ball milling and Na 2 S·9H 2 O modification were employed on ZVI to enhance its efficiency in removing Cr(VI) from effluent. The characterization results expressed that S-mZVI bm had mesoporous and macroporous structures, enabling successful capture of Cr(VI). Moreover, S-mZVI bm had the highest adsorption capacity for Cr(VI) (350.04 mg/g) at pH = 2.00 and reached kinetic equilibrium within 420 min. Furthermore, the adsorption of Cr(VI) by S-mZVI bm conformed to the Avrami-fractional-order model, demonstrated that the adsorption process indicated a complex multi-adsorption process. Meanwhile, the adsorption also fit to Langmuir and Sips models, suggesting monolayer-level adsorption with heterogeneous sites located on S-mZVI bm. The S-mZVI bm could enhance Cr(VI) adsorption through various synergistic mechanisms, such as electrostatic interaction, chemical precipitation, surface complexation, and reduction. Overall, this research presented an innovative perspective for the modification of ZVI, and S-mZVI bm could be widely applied in the practical remediation of wastewater containing Cr(VI). [Display omitted] • A new and high efficiency micron zero-valent iron is synthesized by ball milling. • The maximum adsorption amount of Cr(VI) by S-mZVI bm is 350.04 mg/g. • The main removal mechanisms are precipitation, complexation and reduction. • S-mZVI bm is highly magnetic, which facilitates material recycling. • S-mZVI bm as a promising adsorbent can remove heavy metals from polluted water. [ABSTRACT FROM AUTHOR]

[Display omitted] • nHAP was formed on Ca-BC-P and played crucial role in the U(VI) removal process. • Adsorption capacity of U(VI) by Ca-BC-P is enhanced nearly by 300 % compared to Ca-BC. • Ca-BC-P displayed outstanding potential for treating acidic uranium mine wastewater. • Precipitation and complexation were the main U(VI) removal mechanisms by Ca-BC-P. In this study, waste shrimp shell and phosphorous-containing wastewater were used to synthesize calcium-decorated biochar modified with phosphorus (Ca-BC-P) and utilized to remove uranium from aqueous solutions. The results from static adsorption experiment demonstrated that Ca-BC-P exhibited good U(VI) adsorption performance in acidic environments, with a maximum theoretical adsorption capacity of 1074.29 mg g−1. The adsorption behavior perfectly fit Langmuir isotherm and the pseudo-second-order kinetic models, which revealed the nature of monolayer chemical adsorption by Ca-BC-P. Thermodynamic analysis showed that this process was spontaneous and endothermic. Ca-BC-P also displayed excellent selectivity and could be reused for several times while keeping a high U(VI) removal efficiency. When treating simulated acidic uranium mine wastewater, the removal efficiency of uranium reached 99.9 % with Ca-BC-P. The U(VI) removal mechanism was attributed to the precipitation of Ca(UO 2) 2 (PO 4) 2 ·6H 2 O and surface complexation, nHAP on the surface of Ca-BC-P played a pivotal role during the adsorption process. Therefore, Ca-BC-P could be prepared economically and showed great potential for efficiently remove uranium from mining wastewater. [ABSTRACT FROM AUTHOR]

The environmental impact of arsenic (As) pollution has been a focal point within environmental science. In arsenic-polluted saline-alkali environment, the addition of exogenous biochar can affect the morphological transformation of As both through direct and indirect mechanisms, with calcium ions (Ca(II)) playing a crucial role. This study investigates the immobilization mechanisms of undissolved biochar (UOB) and dissolved biochar (DOB) on As(V) in the absence and presence of Ca(II) under alkaline conditions and aerobic atmosphere. While UOB and DOB alone are insufficient for As(V) immobilization, their combined action in the presence of Ca(II) achieves remarkable immobilization rates of 91.9% and 98.1%, respectively. Precipitation of calcium arsenate is identified as the primary immobilization pathway in both the UOB-Ca(II)-As(V) and DOB-Ca(II)-As(V) systems. Furthermore, Ca(II) acts as a mediator for As(V) immobilization through the formation of ternary UOB/DOB-Ca-As complexes, which are corroborated by Density Functional Theory (DFT) analysis from a microscopic perspective. Notably, the synergistic immobilization of As by DOB and newly generated CaCO 3 in DOB-Ca(II)-As(V) system is highlighted. Additionally, the increase in Ca(II) concentration (0–100 mM) and solution pH (9.0–12.0) both significantly enhance the immobilization of As(V). An increase in the dosage of UOB (0.4–4 g/L) reduces the immobilization of As(V), while effect of the DOB concentration is insignificant. This study provides new insights into how the release of two biochar fractions into a typical Ca(II)-rich saline-alkali environment may alter the fate and transport of As species. [Display omitted] • Ca promotes the immobilization of As(Ⅴ) by BC in Ca-rich alkaline environments. • Ca influences distinct arsenic immobilization by DOB and UOB. • DOB and UOB immobilize As(Ⅴ) by precipitation and complexation in Ca-rich alkaline conditions. • DFT reveals BC-Ca-As complex binding primarily via electrostatic interactions. • Elevating pH and Ca(II) levels enhances As(Ⅴ) immobilization. [ABSTRACT FROM AUTHOR]

In this study, a combination method of freeze-thaw cycle, dry-wet cycle, and chemical agings was used to investigate the aging effect of MgO-modified palygorskite/biochar composite (MPBC) in soil, and its immobilization capacity on Cd under aging. The immobilization mechanisms of MPBC for Cd were explored through several characterizations and DFT calculations. The results showed that MPBC effectively reduced the activate state of Cd by 56.63% at 8 mg/kg Cd concentration. Additionally, MPBC treatment improved physicochemical properties of soil, notably increasing soil pH by 0.26–0.64 units, thereby facilitating Cd immobilization. The predominant mechanism underlying Cd immobilization by MPBC involved the Cd-π complexation, ions exchange, precipitation, and complexation of surface functional groups, including C-O and C=O, with Cd. The citric acid emerged as a milder oxidizing agent combined with freeze-thaw and dry-wet aging conducive to studying the aging effect of MPBC. The dynamic calculation showed that MgO played an important role in the Cd adsorption, with a maximum probability function of 18.35 for Cd. Moreover, within the temperature range of 20 °C–30 °C, the distance between MPBC and Cd was the closest. This study provides a new idea for artificial aging of biochar and a practical method for the remediation of Cd pollution in soil. [Display omitted] • The chemical, freeze-thaw, and dry-wet aging was used to simulate natural aging. • MPBC effective reduced the activate state of Cd in soil. • The MPBC improved the physical and chemical properties of polluted soil. • DFT predicted 20–30 °C might be the best application temperature range of MPBC. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) pollution has aroused wide public attention due its high mobility, bioaccumulation and carcinogenic properties, and biochar has been proven as an efficient adsorbent for removal of Cd due to its environmentally friendly and economic approach. In this study, three variables (grinding time, rotational speed, and mass ratio of ball–to–powder) were established through response surface methodology and Box–Behnken design, and the preparation process of ball–milled biochar (BMBC) was successfully optimized. The results indicated that the impact factors on Cd removal by BMBC were in the order of milling speed > grinding time > ball to powder mass ratio, and the optimum parameters for Cd removal were found to be: milling time = 16 h, speed = 448 rpm, and ball to powder mass ratio = 1.5:100. BMBC (300 nm) has a dramatically larger specific surface area and pore volume by 22 and 15 times, respectively, and was companied with richer oxygen–containing functional groups. The adsorption of Cd2+ on BMBC conformed to the pseudo–second–order kinetic model and the Langmuir model. The maximum adsorption capacity of Cd2+ was 3 times that of BC. Precipitation and complexation were the main mechanisms for the adsorption of Cd. Therefore, BMBC was a promising and effective adsorbent for the removal of Cd, which has potential application value. [Display omitted] • RSM and Box-Behnken design was to determine the optimal ball milling process parameters. • Ball milling enhances the specific surface area, pore volume, negative zeta potential of biochar. • Nano-biochar has more O-containing functional groups and higher polarity. • Nano biochar has high removal rate of Cd2+ from aqueous solution. [ABSTRACT FROM AUTHOR]

This work elucidated the performance and mechanisms of Pb2+ adsorption by kaolinite, montmorillonite, goethite and ferrihydrite using batch experiments. The contributions of various adsorption mechanisms were quantified using a stepwise extraction method. Several characterizations (scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, point of zero charge analysis and X-ray fluorescence) were utilized to analyse the physicochemical properties and the potential adsorption mechanisms. The results indicated that the adsorption processes of montmorillonite and goethite approached equilibrium within 20 min, while 60 min were required for the adsorption processes of kaolinite and ferrihydrite. The adsorption processes of Pb2+ by the four minerals best fit the pseudo-second order model. The adsorption capacities of the four minerals for Pb2+ followed the order: montmorillonite > goethite > ferrihydrite > kaolinite, and the maximum adsorption capacities were 69.20, 46.95, 34.32 and 18.62 mg g–1, respectively. The stepwise extraction test showed that the adsorption mechanism of Pb2+ was dominated by ion exchange for montmorillonite, precipitation and complexation for goethite and complexation for kaolinite and ferrihydrite. [ABSTRACT FROM AUTHOR]

Nowadays, biochar is being studied to a great degree because of its potential for carbon sequestration, soil improvement, climate change mitigation, catalysis, wastewater treatment, energy storage, and waste management. The present review emphasizes on the utilization of biochar and biochar-based nanocomposites to play a key role in decontaminating dyes from wastewater. Numerous trials are underway to synthesize functionalized, surface engineered biochar-based nanocomposites that can sufficiently remove dye-contaminated wastewater. The removal of dyes from wastewater via natural and modified biochar follows numerous mechanisms such as precipitation, surface complexation, ion exchange, cation–π interactions, and electrostatic attraction. Further, biochar production and modification promote good adsorption capacity for dye removal owing to the properties tailored from the production stage and linked with specific adsorption mechanisms such as hydrophobic and electrostatic interactions. Meanwhile, a framework for artificial neural networking and machine learning to model the dye removal efficiency of biochar from wastewater is proposed even though such studies are still in their infancy stage. The present review article recommends that smart technologies for modelling and forecasting the potential of such modification of biochar should be included for their proper applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various synthesis methods of livestock manure biochar are introduced in detail. • Co-precipitation, surface complexation, π-π interactions and hydrogen bonding are mainly adsorption mechanisms of pollutants. • Carbon content and surface area are more important for heavy metals and organic contaminants adsorption, respectively. • C=O group plays a key role on the nonradical contribution in activating persulfate process. The conversion of livestock manure into harmless biochar for pollutants removal from wastewater is in accordance with the principle of sustainable development. However, a comprehensive understanding of the reaction mechanisms involved in the mechanism of adsorption/degradation removal of aqueous pollutants is still lacking, which limits the current application of pristine livestock manure derived biochar (MDBC) and its composites (MDBCs) in wastewater treatment. To enhance understanding in this aspect, this review summarized the latest research on the utilization of MDBCs as adsorbents and as catalysts in persulfate (PS), photocatalysis, self-catalytic system and Fenton-like advanced oxidation processes (AOPs) for pollutants removal from water environment. Additionally, a comprehensive summary of adsorption mechanisms of MDBCs were provided. For heavy metals, the main adsorption mechanisms involved co-precipitation and surface complexation, while for organic contaminants, the main adsorption mechanisms were π-π interactions and hydrogen bonding. According to random forest method, the carbon content and surface area are identified as key characteristics of MDBCs that influence the adsorption of heavy metals and organic contaminants, respectively. An emphatic summarizes of activation mechanisms of MDBCs in AOPs systems were presented, including radical oxidation and non-radical oxidation pathways. Especially, the connections between different physicochemical characteristics of MDBCs and nonradical contribution based on persulfate were investigated. This analysis will offer valuable insights for the rational design of MDBCs to enhance nonradical pathways selectively. Finally, the challenges and future perspectives related to MDBCs are proposed to facilitate research into this sustainable livestock manure derived biochar. [ABSTRACT FROM AUTHOR]

Sediments contaminated with hazardous metals pose risks to humans and wildlife, yet viable management options are scarce. In a series of laboratory experiments, we characterized Polonite® – an activated calcium-silicate – as a novel sorbent for thin-layer capping of metal-contaminated sediments. We tested a fine-grained by-product from the Polonite production as a cheap and sustainable sorbent. First, Polonite was reacted with solutions of Cu, Pb, and Zn, and the surface chemistry of the Polonite was examined using, e.g., scanning electron microscopy to investigate metal sorption mechanisms. Batch experiments were conducted by adding Polonite to industrially contaminated harbor sediment to determine sorption kinetics and isotherms. Importantly, we measured if the Polonite could reduce metal bioavailability to sediment fauna by performing digestive fluid extraction (DFE). Finally, a cap placement technique was studied by applying a Polonite slurry in sedimentation columns. The results showed rapid metal sorption to Polonite via several mechanisms, including hydroxide and carbonate precipitation, and complexation with metal oxides on the Polonite surface. Isotherm data revealed that the sediment uptake capacity (K f) for Cu, Pb, and Zn increased by a factor of 25, 21, and 14, respectively, after addition of 5% Polonite. The bioavailability of Cu, Pb, and Zn was reduced by 70%, 65%, and 54%, respectively, after a 25% Polonite addition. In conclusion, we propose that sediment treatment with low doses of the Polonite by-product can be a cheap, sustainable, and effective remediation method compared to other more intrusive methods such as dredging or conventional isolation capping. [Display omitted] • A new calcium-silicate was tested for amendment of metal polluted sediment. • A 5% dose increased sediment uptake capacity of metals by a factor of 14–25. • A 25% dose decreased bioavailability (solubilization in gut fluid) by 54–70%. • Adsorption occurred through several types of complexation and precipitation. • The amendment is an effective, cheap, and sustainable remediation option. [ABSTRACT FROM AUTHOR]

Many studies have studied biochar immobilizing chromium (Cr) in soil. However, few studies were conducted to reduce the environmental risks due to biochar aging in soil. In this study, we adopt FeCl 3 , MgCl 2 , and AlCl 3 to activate sewage sludge to form modified biochar and produce biochar tubules. Then, the column experiments were carried out to study the effect of fluctuating groundwater table on Cr leaching behavior, total Cr, and fractions distribution with the insertion of biochar tubule. Results showed that the Cr immobilization performance was improved by metal-modification biochar, the biochar tubules can significantly decrease the Cr leaching amounts, retard the Cr downward migration in the soil, and there was a better effect with slightly Cr-contaminated soil. In addition, the immobilization effect is also impacted by the biochar's application mode and the hydrodynamic conditions. Detailedly, the Cr leaching amounts maximally decreased by 33.39%, the residual amounts maximally increased by 10.05% in the soil column, and the exchangeable (EX) and carbonates-bound (CB) fractions were maximally increased by 85.18%, 151.78% at the equal depth of soil column, respectively. BET, SEM-EDS, XRD, and FTIR analyses revealed that biochars' immobilization mechanisms on Cr involved reduction(predominately), physisorption, precipitation, and complexation. Risk assessment demonstrated that the sewage sludge biochar has very low environmental risk. This study indicates that the biochar tubule applied to immobilize Cr in soil has potential and provides new insights into reducing environmental risks due to biochar aging. [Display omitted] • Different sewage sludge biochars were produced by loading metal. • Novel biochar tubule was used to immobilize Cr-contaminated soil to avoid Cr return due to biochar aging. • GTF promotes the release of Cr in soil. • Mg-SSB shows higher immobilization ability for Cr by improving the porous structures of biochar. • Immobilization mechanisms include adsorption, precipitation, reduction, and complexation. [ABSTRACT FROM AUTHOR]

Biochar (BC) has emerged as a potential solution to phosphate removal from wastewater primarily resulting from global overuse of fertilizers. Further modification by embedment of iron (Fe)-manganese (Mn) oxides on BC can enhance phosphate removal; however, the modification method serves as a vital factor underlying distinctive removal performances and mechanisms, which have yet been systematically examined. Herein, two Fe–Mn modified BC, Fe/MnBC (comprised of Fe 3 O 4 and MnO 2) and Fe–MnBC (comprised of MnFe 2 O 4), were comprehensively investigated for gaining insights into the unsolved perspectives. The results indicated that Fe–MnBC exhibited a markedly greater maximum phosphate adsorption capacity of 135.88 mg g−1 than that of Fe/MnBC with 17.93 mg g−1. The comparative results based on microstructure and spectroscopic analyses suggested that different Fe and Mn oxides were successfully loaded, which played a distinctive role in phosphate removal. Further characterizations unveiled that the key mechanisms for phosphate removal by Fe/MnBC are inner-sphere complexation and precipitation, while electrostatic interaction and outer-sphere complexation are the dominant mechanisms underlying the notable performance of Fe–MnBC. The delicately designed Fe–MnBC with special structure and property also enabled a superior regeneration capacity, which presented a promisingly high phosphate removal efficacy of over 81.34% after five cycles. These results enhance comprehension regarding the impact of biochar modification techniques on phosphate removal, offering positive indications for the remediation of excessive phosphate and other pollutant-containing water through feasible design and green chemicals. [Display omitted] • Biochar modified by Fe–Mn oxides remarkably enhanced phosphate removal. • Fe/MnBC consists of Fe 3 O 4 and MnO 2 , while Fe–MnBC consists of MnFe 2 O 4. • The dominant removal mechanisms of Fe/MnBC are precipitation and complexation. • Electrostatic attraction and complexation are key mechanisms for Fe–MnBC. • Fe–MnBC has a better regeneration capacity than Fe/MnBC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 3 O 4 @LH was synthesized successfully via a one-pot synthetic strategy. • Application of Fe 3 O 4 @LH reduced soil total Pb by 16.7 %∼25.4 %. • Fe 3 O 4 @LH exhibited a maximum Pb adsorption capacity of 174.2 mg/g. • Adsorption process involved electrostatic adsorption, ion exchange, precipitation, and complexation. • Fe 3 O 4 @LH recovery exceeded 88.3% after a 90-day application period. Lead (Pb) contamination in agricultural soils poses a significant threat to both ecosystems and human health. While nano-Fe 3 O 4 exhibits promising potential for Pb remediation, its practical application in the soil is hindered by its' biotoxicity, easy aggregation, and the risk of secondary pollution. Thus, this study presents a novel approach wherein Fe 3 O 4 was incorporated into hydrogel via a one-pot synthetic strategy (Fe 3 O 4 @LH). This incorporation enhanced the mechanical properties and environmental stability of the hydrogel composites. Based on the mechanical properties, environmental stability, and single-point adsorption results for Pb, we selected Fe 3 O 4 @LH-4 for further research. The removal mechanism and the feasibility of employing Fe 3 O 4 @LH-4 for Pb removal from paddy soil were investigated through batch adsorption experiments and soil culture studies. Results showed that the adsorption process was primarily governed by swelling adsorption, electrostatic adsorption, ion exchange, precipitation, nanometer effect, and complexation mechanisms. The application of Fe 3 O 4 @LH-4 significantly led to the reduction of 16.7 %–25.4 % in soil Pb content, with removal rates escalating alongside increased dosage and application periods of Fe 3 O 4 @LH-4. Fitting results of the prediction model indicated that the Pb content in mildly Pb-contaminated soil (186.55 mg/kg) would decrease to be below the risk control standard for soil contamination of agricultural land in China (140 mg/kg) after 112 days of continuous application. Concurrently, cadmium and arsenic contents in the soil decreased by 5.2 %–10.8 % and 7.1 %–16.7 %, respectively. Moreover, the application of Fe 3 O 4 @LH-4 positively influenced soil nutrient levels, with total nitrogen and soil organic matter content significant increments of 13.6 %–41.0 % and 4.6 %–16.1 %, respectively. Furthermore, Fe 3 O 4 @LH-4 recovery exceeded 88.3 % after a 90-day application period. These findings underscore the potential of Fe 3 O 4 incorporated hydrogel as a promising agent for the sustained removal of heavy metal Pb from paddy soil. [ABSTRACT FROM AUTHOR]

Nitrogen-doped biochar (NBC) is a green material for remediating heavy metal pollution, but it undergoes aging under natural conditions, affecting its interaction with heavy metals. The preparation conditions of NBC were optimized using response surface methodology (RSM), and NBC was subjected to five different aging treatments to analyze the removal efficiency of Cd(II) and soil remediation capability before and after aging. The results indicated that NBC achieved optimal performance with a mass ratio of 5:2.43, an immersion time of 10.66 h, and a pyrolysis temperature of 900 °C. Aging diminished NBC's adsorption capacity for Cd(II) but did not change the main removal mechanism of monolayer chemical adsorption. Freeze-thaw cycles (FT), UV aging (L), and composite aging (U) treatments increased the proportion of bioavailable-Cd, and all aging treatments facilitated the conversion of potentially bioavailable-Cd to non-bioavailable-Cd. The application of NBC and five aged NBCs reduced the proportion of bioavailable-Cd in the soil through precipitation and complexation, increasing the proportion of non-bioavailable-Cd. Aging modifies the physicochemical properties of NBC, thus influencing soil characteristics and ultimately diminishing NBC's ability to passivate Cd in the soil. This study provides reference for the long-term application of biochar in heavy metal-contaminated environments. [Display omitted] • RMS can be used to optimize the preparation of efficient Cd NBC for adsorption. • Pyrrolic-N is more important than other structural N in the removal of Cd. • Aging treatment significantly weakened the ability of NBC to remove Cd. • Aging of NBC delayed the conversion of bioavailable-Cd to non-bioavailable-Cd. [ABSTRACT FROM AUTHOR]

A high-performance ceramsite for phosphorus adsorption was successfully prepared using regolith granite sand washing sludge and phosphate tailings as raw materials. The characterization and formation mechanism of the ceramsite have been investigated. [Display omitted] • An efficient ceramsite for phosphorus removal was made completely from two wastes. • The ceramsite is highly selective to phosphorus with 20.4 mg/g adsorption capacity. • The ceramsite is environmentally safe with high reusability. • Sorption mechanisms include precipitation, complexation, and electrostatic pull. This study successfully prepared a high-performance ceramsite for phosphorus adsorption using the sintering method, incorporating regolith granite sand-washing sludge (RGSWS) and phosphate tailings as raw materials. The optimal conditions for ceramsite preparation were determined as a ratio of RGSWS to phosphate tailings at 6:4, and sintering at 900 °C for 30 min. The impacts of various factors, such as the prepared ceramsite dosage, different initial phosphorus concentrations, temperature, pH, and co-existing ions were explored, and the reusability and safety of the ceramsite were also investigated. The results show that the ceramsite has a high adsorption capacity for phosphorus (20.40 mg/g) at pH 7 with broad applicability in the pH range of 3–11 and good selective adsorption in the presence of coexisting ions. Additionally, the application of ceramsite does not cause secondary pollution, and the ceramsite still maintains a high removal rate after being reused five times. XRD, FT-IR, XPS, and SEM-EDS analysis showed that chemical precipitation, surface complexation, and electrostatic attraction were involved in the adsorption process. It can be well described by the pseudo-second-order kinetic model and the Langmuir model, and the phosphorus adsorption by ceramsite was a spontaneous endothermic reaction process with increasing chaos. This research presents an effective solution for phosphorus removal from water bodies and offers a sustainable approach toward solid waste utilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ceramsite showed high and stable adsorption efficiency (>85 %) for lead under pH conditions in the acidic range. • The adsorption mechanisms included ion exchange, electrostatic attraction, precipitation and complexation. • It is feasible for the ceramsite to be used as filler in permeable reactive barriers. The reuse and recycling of bulk solid waste, such as tailings, presents a challenge to achieving sustainability in contemporary urban development. In this study, adopting the "waste for waste" approach, a novel form of ceramsite was devised utilizing iron tailings and coal gangue to adsorb Pb(II) from the groundwater environment. The optimized ceramsite, sintered at 850 ℃ with the addition of 30 % coal gangue, exhibited good adsorption potential and environmental friendliness. The optimized ceramsite was a viable material for efficiently removing Pb(II) within the acidic pH range (Q e = 12.28 mg/g). The outcomes from batch experiments and various characterizations of the materials revealed that the adsorption mechanisms of ceramsite involved both physical and chemical adsorption, with chemisorption being the most significant. Column studies showed that ceramsite as fillers could be effective in treating lead discharges from groundwater during mining utilization. The dynamic reaction process of the ceramsite exhibited the most accurate fit with the Thomas and Yan models. The primary adsorption mechanisms included the ceramsite's abundant pores facilitating cation exchange, attraction of Pb(II) to the anionic groups on the ceramsite resulting in its deposition and coverage on the particle surface, and the formation of stable Pb-O and Si-O-Pb bonds. These findings indicate that ceramsite prepared from iron tailings and coal gangue shows promise as an adsorbent for treating lead-containing wastewater. [ABSTRACT FROM AUTHOR]

Arsenic (As) and cadmium (Cd) accumulation in rice grains is a global food safety issue, and various methods and materials have been used to remove or reduce As and Cd in agricultural soils and rice grains. Despite the availability of synthesized materials capable of simultaneous As and Cd reduction from soil and rice grains, the contributions, efficiency, and main ingredients of the materials for As and Cd immobilization remain unclear. The present study first summarized the biogeochemistry of As and Cd in paddy soils and their transfer in the soil-food-human continuum. We also reviewed a series of reported inorganic and organic materials for simultaneous immobilization of As and Cd in paddy soils, and their reduction efficiency of As and Cd bioavailability were listed and compared. Based on the abovementioned materials, the study conducted a meta-analysis of 38 articles with 2565 observations to quantify the impacts of materials on simultaneous As and Cd reduction from soil and rice grains. Meta-analysis results showed that combining organic and inorganic amendments corresponded to effect sizes of −62.3% and −67.8% on As and Cd accumulation in rice grains, while the effect sizes on As and Cd reduction in paddy soils were −44.2% and −46.2%, respectively. Application of Fe based materials significantly (P < 0.05) reduced As (−54.2%) and Cd (−74.9%), accounting for the highest immobilization efficiency of As and Cd in rice grain among all the reviewed materials, outweighing S, Mn, P, Si, and Ca based materials. Moreover, precipitation, surface complexation, ion exchange, and electrostatic attraction mechanisms were involved in the co-immobilization tactics. The present study underlines the application of combined organic and inorganic amendments in simultaneous As and Cd immobilization. It also highlighted that employing Fe-incorporated biochar material may be a potential strategy for co-mitigating As and Cd pollution in paddy soils and accumulation in rice grains. • Amendment materials for simultaneous As and Cd reduction in paddy soil were reviewed and compared. • Co-application of organic and inorganic materials reduced As and Cd in grains by 84.3% and 23.4%. • Combination of inorganic/organic materials was beneficial in reducing As/Cd bioavailability. • Fe-based materials showed the best performance in simultaneously mitigating As and Cd pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid treatment removed intrinsic minerals of biochar optimized the pore structure. • New –OH produced has lower potential energy to reduce Cr(VI) and combine with Cr(III). • The promotion of Cr(VI) adsorption by the four elements is Fe3+> Mg2+＞ Ca2+> K+. • The adsorption of AAEMs and transition metals to Cr(VI) are ion exchange, precipitation and complexation. Cr(VI) is extremely harmful to the ecological environment. The secondary purification method of treating low concentrations is not satisfactory currently. In this paper, wheat straw were pyrolyzed at 800 °C to obtain biochar, which were used to explore the effect of minerals on adsorption effect as a precursor at different pH and 25 °C. The biochar was gradually eluted with HCl and HF to remove the ash, soon loaded with K+, Ca2+, Mg2+ and Fe3+, respectively. The results show that under the action of H+, the C O bonds left after mineral removal have lower potential energy than the original surface functional groups in terms of conversion to –OH and binding to Cr. The order of promotion of Cr(VI) adsorption by the four elements is Fe3+> Mg2+＞ Ca2+> K+. As the radius of metal ions decreases, so does the electronegativity of biochar and the surfactive site increases. The adsorption mechanisms of alkali metals, alkaline earth metals and transition metals to Cr(VI) are mainly based on ion exchange, precipitation and complexation, respectively. The adsorption of Cr(VI) by wheat straw biochar was consistent with the quasi-secondary kinetic model. Combined with the results of intraparticle diffusion model fitting, it shows that this process is a multi-stage adsorption process with the combined effect of physical and chemical adsorption. [ABSTRACT FROM AUTHOR]

Arsenic and cadmium contamination, along with their associated environmental risks, is a global concern, and the synergistic stabilization of cations and oxyanions in contaminated environments is challenging. In this study, goethite-modified biochar (BC-Gt) was synthesized and investigated for its remediation potential in co-contamination of cadmium (Cd) and arsenic (As), compared to pristine reed-straw biochar (BC) and goethite (Gt). BC-Gt exhibited the highest maximum adsorption capacities in the binary As and Cd solution (As: 126.02 mg·g−1, Cd: 125.12 mg·g−1). BET-SSA, SEM-EDS, XRD, FTIR and XPS analyses revealed various mechanisms of co-adsorption of As and Cd on BC-Gt, including ion exchange, electrostatic interaction, surface precipitation and complexation. Moreover, the specific adsorption of Cd(II) involved cation-π interaction, while limited oxidation-reduction of As(V) occurred during adsorption. BC-Gt also displayed profound stabilization effects in As, Cd and lead (Pb) co-contaminated soils, with maximum removal efficiencies of 63.98 %, 83.67 % and 83.92 %, respectively. BC-Gt outperformed BC and Gt in transforming the exchangeable fraction (Exc) into reducible (Red), oxidizable (Oxi) and residual (Res) fractions of As, Cd and Pb. This study provides evidence in the potential of BC-Gt for remediating co-contamination of As and Cd in water, as well as As, Cd and Pb in soil. [Display omitted] • Goethite-modified biochar (BC-Gt) adsorbing mixed As(V) and Cd(II) solution was tested. • Ion exchange, electrostatic interaction, and precipitation were the common mechanisms. • Cd(II) involved in cation-π interaction while As(V) had reduction. • BC-Gt effectively immobilized As, Cd and Pb from the co-contaminated soils. • BC-Gt transformed exchangeable into other relatively immobile fractions of As, Cd and Pb. [ABSTRACT FROM AUTHOR]

To study the pollutants immobilization and economy of biologically amended coastal soil, Alternanthera philoxeroides biomass (Bm), biochar (Bc), and dodecyldimethyl betaine (BS) modified Bc (BS-Bc) were used to amend coastal soil from Jialing, Fu, and Qu River. A runoff experiment was used to simulate the longitudinal migration and morphological changes of Pb(II) and chlortetracycline (CTC) in each amended coastal soil, and the economy of pollutants immobilization by different amended coastal soil were compared. The equilibrium time of Pb(II) and CTC in each amended coastal soil ranked in the order of BS-Bc-amended > Bc-amended > Bm-amended > unamended coastal soil. The average Pb(II) and CTC flow rate in different amended coastal soils presented an opposite trend with the equilibrium time. Pb(II) and CTC content all reduced with the increasing runoff length. Under the same soils, the content changes presented Bm and Bc amended > unamended > BS-Bc amended. CEC and clay content of coastal soils were the key factors affecting Pb(II) and CTC immobilization. The immobilization mechanisms were electrostatic attraction, ion exchange, surface precipitation, and complexation to Pb(II) and ion exchange and complexation to CTC. The economy of Pb(II) and CTC immobilization ranged from 0.5 to 9.0 and from 1.0 to 5.4 mg/¥, and coastal soil amended by BS-Bc had practical application value and high economy. • Equilibrium time of Pb(II) and CTC were BS-Bc > Bc > Bm > un- amended coastal soil. • The average pollutants flow rate showed an opposite trend with the equilibrium time. • Pb(II) and CTC content all reduced with the increasing runoff length. • Cation exchange capacity and clay content highly affected pollutants immobilization. • Coastal soil amended by BS-Bc had practical application value and high economy. [ABSTRACT FROM AUTHOR]

Bentonite-based composites have been widely utilized in the removal of various pollutants due to low cost, environmentally friendly, ease-to-operate, whereas the recent advances concerning the application of bentonite-based composites in environmental remediation were not available. Herein, the modification (i.e., acid/alkaline washing, thermal treatment and hybrids) of bentonite was firstly reviewed; Then the recent advances of adsorption of environmental concomitants (e.g., organic (dyes, microplastics, phenolic and other organics) and inorganic pollutants (heavy metals, radionuclides and other inorganic pollutants)) on various bentonite-based composites were summarized in details. Meanwhile, the effect of environmental factors and interaction mechanism between bentonite-based composites and contaminants were also investigated. Finally, the conclusions and prospective of bentonite-based composites in the environmental remediation were proposed. It is demonstrated that various bentonite-based composites exhibited the high adsorption/degradation capacity towards environmental pollutants under the specific conditions. The interaction mechanism involved the mineralization, physical/chemical adsorption, co-precipitation and complexation. This review highlights the effect of different functionalization of bentonite-based composites on their adsorption capacity and interaction mechanism, which is expected to be helpful to environmental scientists for applying bentonite-based composites into practical environmental remediation. • The modification of bentonite was firstly reviewed. • Recent advances of adsorption of organics, heavy metals and radionuclides on bentonite were summarized. • Interaction mechanism of bentonite and contaminants were investigated. • The conclusions and prospective of bentonite-based composites were proposed. • This review is expected to be helpful into practical environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Prepared stable 1:1 inclusion complexes of hydrophobic anticancer drug MNC with β-cyclodextrin. • Comprehensive characterization confirmed successful complexation via co-precipitation method. • Complexation significantly enhanced poor aqueous solubility of MNC. • Molecular modeling provided insights into host–guest interactions stabilizing the complex. • MNC: β-CD complex exhibited superior anticancer activity over free MNC and standard drug. 3-Nitro-2 H -chromene derivatives exhibit promising anticancer activities, but their clinical translation is hindered by poor aqueous solubility. Herein, we report a cyclodextrin complexation strategy to improve the solubility and therapeutic efficacy of 8-methoxy-2-(4-methoxy phenyl)-3-nitro-2 H -chromene (MNC), a potent anticancer agent. Solid inclusion complexes of MNC: β -cyclodextrin (β -CD) were synthesized by co-precipitation and kneading methods, and comprehensively characterized using UV–vis, Fluorescence, Fourier Transform Infrared (FT-IR), Differential scanning calorimetry (DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM), 1H NMR, and mass spectrometric techniques. A 1:1 host–guest stoichiometry was verified by phase solubility and UV–Vis spectroscopic studies. β -CD complexation remarkably enhanced the aqueous solubility of hydrophobic MNC. Cytotoxicity evaluation against different human cancer cell lines such as breast cancer (MCF-7, MDA-MB-231), lung cancer (A549), and liver cancer (HepG2) demonstrated superior anticancer activity of the co-precipitated MNC: β -CD complex compared to free MNC and the chemotherapeutic 5-fluorouracil. Although the host–guest interaction energy obtained from molecular docking was modest (−5.1 kcal/mol), it facilitated effective MNC encapsulation and delivery by β -CD. Density functional theory (DFT) calculations provided further insights into the inclusion phenomenon. This cyclodextrin complexation approach paves the way for developing an effective MNC formulation with improved bioavailability and anticancer therapeutic efficacy. [ABSTRACT FROM AUTHOR]

Heavy metal pollution, particularly the excessive release of copper (Cu), is an urgent environmental concern. In this study, sodium lignosulfonate/carboxymethyl sa-son seed gum (SL-Cg-g-PAA) designed for remediation of Cu-contaminated water and soil was successfully synthesized through a free radical polymerization method using lignin as a raw material. This hydrogel exhibits remarkable Cu adsorption capability when applied to water, with a maximum adsorption capacity reaching 172.41 mg/g. Important adsorption mechanisms include surface complexation and electrostatic attraction between Cu(Ⅱ) and oxygen-containing functional groups (–OH, –COOH), as well as cation exchange involving –COONa and –SO 3 Na. Furthermore, SL/Cg-g-PAA effectively mitigated the bioavailability of heavy metals within soil matrices, as evidenced by a notable 14.1% reduction in DTPA extracted state Cu (DTPA-Cu) content in the S4 treatment (0.7% SL/Cg-g-PAA) compared to the control group. Concurrently, the Cu content in both the leaves and roots of pakchoi exhibited substantial decreases of 55.19% and 36.49%, respectively. These effects can be attributed to the precipitation and complexation reactions facilitated by the hydrogel. In summary, this composite hydrogel is highly promising for effective remediation of heavy metal pollution in water and soil, with a particular capability for the immobilization of Cu(Ⅱ) and reduction of its adverse effects on ecosystems. [Display omitted] • A new lignin-based hydrogel (SL-Cg-g-PAA) was successfully synthesized by radical polymerization. • SL-Cg-g-PAA exhibits excellent adsorption capacity for Cu (II) in water. • SL-Cg-g-PAA reduced the content of DTPA extractable Cu in soil. • The content of Cu in various parts of pakchoi is reduced. [ABSTRACT FROM AUTHOR]

The problem of cadmium pollution and its control is becoming increasingly severe issue in the world. Banana straw is an abundant bio raw material, but its burning or discarding in field not only causes pollution but also spreads fusarium wilt. The objective of this paper is to utilize biochar derived from the wilt-infected banana straw for remediation of Cd(II) pollution while to eliminate the pathogen. The activity of wilt pathogen in biochar was determined by PDA petri dish test. The Cd(II) adsorption of the biochar was determined by batch adsorption experiments. The effects of KOH concentration (0.25, 0.5 and 0.75 M) on the physicochemical characteristics of the biochar were also observed by BET, SEM, FTIR, XRD and XPS. Results showed that pristine banana straw biochar (PBBC) did not harbor any pathogen. The specific surface area (SSA) and Cd(II) adsorption capacity of 0.75 M KOH modified banana straw biochar (MBBC0.75M) were increased by 247.2% and 46.1% compared to that of PBBC, respectively. Cd(II) adsorption by MBBC0.75M was suitable to be described by the pseudo-second-order kinetic model and Freundlich isotherm. After Cd(II) adsorption, the CdCO3 were confirmed by XRD and observed through SEM. The weakness and shift of oxygen-containing functional groups in MBBC0.75M after Cd(II) adsorption implied that those groups were complexed with Cd(II). The results showed that pyrolysis could not only eliminate banana fusarium wilt, but also prepare porous biochar with the wilt-infected banana straw. The porous biochar possessed the potential to adsorb Cd(II) pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic lignin-based hydrochar was synthesized from pulping black liquor. • MLHC 140 demonstrated satisfied Tl(III) removal over a wide pH range (2–9). • Capacity reached 278.9 mg/g and over 90 % of Tl(III) was captured within 15 min. • The mechanisms are mainly surface precipitation and complexation. • Adsorbed MLHC 140 could be recovered easily via a facile external magnet. Waste lignin, such as black liquor (BL) from paper and pulping industries, is an agro-industrial biowaste while its reuse raised global concerns. In this work, a hydrothermal carbonization procedure was employed to convert BL into magnetic lignin-based hydrochar (MLHC) for thallium elimination from wastewater. The results exhibited water purification potential due to a wider working pH window (2–9) with the magnetization intensity of 11.12 emu/g. The maximum adsorption capacity for Tl(III) was 278.9 mg/g, while the contribution of various mechanisms was elucidated with the order: surface precipitation (31.3 %), complexation (20.6 %), physical adsorption (18.2 %), chemical reduction (15.0 %), and ion exchange (14.9 %). This study revealed that hydrothermal treatment could be a potential and promising method to convert waste lignin into magnetic bio-adsorbent to recycle pulping black liquor and apply it for thallium pollution control. [ABSTRACT FROM AUTHOR]

Due to the multiplicity of biogeochemical processes taking place in anaerobic digestion (AD) systems and limitations of the available analytical techniques, assessing the bioavailability of trace elements (TEs) is challenging. Determination of TE speciation can be facilitated by developing a mathematical model able to consider the physicochemical processes affecting TEs dynamics. A modeling framework based on anaerobic digestion model no 1 (ADM1) has been proposed to predict the biogeochemical fate TEs in AD environments. In particular, the model considers the TE adsorption–desorption reactions with biomass, inerts and mineral precipitates, as well as TE precipitation/dissolution, complexation reactions and biodegradation processes. The developed model was integrated numerically, and numerical simulations have been run to investigate the model behavior. The simulation scenarios predicted the effect of (i) organic matter concentration, (ii) initial TEs concentrations, (iii) initial Ca–Mg concentrations, (iv) initial EDTA concentration, and (v) change in TE binding site density, on cumulative methane production and TE speciation. Finally, experimental data from a real case continuous AD system have been compared to the model predictions. The results prove that this modelling framework can be applied to various AD operations and may also serve as a basis to develop a model-predictive TE dosing strategy. [ABSTRACT FROM AUTHOR]

High concentrations of heavy metals lead (Pb) and cadmium (Cd) in soil have triggered a serious threat to plant growth, animal health, and ecological environment for human survival. Non-biodegradable Pb and Cd contamination in soil can be easily transferred to agricultural crops through the soil-plant-food chain, easy to endanger human body health. Alternatively, in situ stabilization is an effective technology to reduce the toxicity of such heavy metals. However, it is particularly important to choose the cost-effective materials with significant stability effects in soil. This study aims to seek in situ stabilized remediation materials with a high adsorption efficiency of heavy metal. A vermicomposting experiment of cow dung mixed with high calcium and magnesium minerals or sepiolite was conducted to analyze the variation of substrate residues properties and the adsorption characteristics of Pb2+ and Cd2+. Firstly, the growth indexes of earthworms were selected for the feasibility of vermicomposting cow dung mixed with minerals. Then, the substrate residues were characterized, including pH value, cation exchange capacity, morphology under a Scanning Electron Microscopy (SEM), mineral components under X-Ray Diffraction (XRD), and surface functional groups under a Fourier Transform Infrared Spectroscopy (FTIR). Finally, batch adsorption experiments were carried out to evaluate the adsorption efficiency of Pb2+ and Cd2+ from aqueous solution. The results demonstrated that the earthworms survived well with high calcium and magnesium minerals or sepiolite addition. The earthworm treatment reduced pH value, C/N, and organic content, while, increased the cation exchange capacity, and the specific surface area of substrate residues. High calcium and magnesium minerals or sepiolite addition both increased the pH value, cation exchange capacity, and specific surface area of substrate residues. FTIR analysis showed that the earthworm treatment had more alcohol or carboxylic acids and aromatic substance, while, less lipid material and polysaccharide substance in substrate residues, compared with the untreatment. The addition of high calcium and magnesium mineral also produced more Me-O groups in substrate residues. XRD analysis showed that more silicate and soluble salts were found in the earthworm treatment, compared with the untreatment. The addition of high calcium and magnesium mineral produced silicate, CaO and MgO components, whereas, the sepiolite addition produced silicate and MgO components in substrate residues. The batch adsorption experiment showed that the earthworm treatment had better adsorption capacity of Pb2+and Cd2+ in aqueous solution. The adsorption efficiency of Pb2+and Cd2+ was the best for the substrate residues rom the vermicomposting process of cow dung mixed with high calcium and magnesium minerals. The adsorption rates of Pb2+ and Cd2+ were 77.8% and 59.7%, respectively, whereas, the desorption rate of adsorption states Pb2+ and Cd2+ were 0.02% and 6.66%, respectively. It infers that the adsorption mechanism of VG for Pb2+ and Cd2+ involved in the physical adsorption, ion exchange, electrostatic adsorption, precipitation, and complexation. A high adsorption efficiency of Pb2+and Cd2+ from aqueous solution was achieved under the higher pH value, cation exchange capacity and specific surface area, abundant functional groups and mineral components in VG. Therefore, it is feasible to produce substrate residues with high Pb2+and Cd2+ adsorption capacity via adding high calcium and magnesium mineral into cow dung for vermicomposting. The findings can provide an insightful theoretical basis to effectively optimize key parameters for the vermicomposting of cow dung mixed with minerals, and thereby to promote the recycling efficiency of organic solid wastes and the safe utilization of heavy-metal contaminated soil. [ABSTRACT FROM AUTHOR]

Due to their ability to provide efficient mixing at small scales, confined impinging jet mixers (CIJMs) are employed widely in nanoparticle assembly processes such as flash nanoprecipitation and flash nanocomplexation, which require rapid mixing. In this mixing device, two jets from opposite directions impinge directly on each other forming a thin shear layer that breaks down rapidly into small flow structures. This enables effective mixing of the species transported by each jet by drastically reducing the diffusion distance. In the present study, the mixing performance of a commonly used cylindrical CIJM is examined by direct numerical simulations. Analysis of the simulation results indicates that the interaction of the shear layer with the inner walls of the CIJM is critical in inducing a range of instabilities in the impinging jet flow. By examining flow structures, statistical quantities, and metrics, we have characterized and quantified the mixing quality of a binary mixture in the CIJM. Product uniformity in processes such as precipitation and complexation is expected to depend on the residence time of the constituents, and this quantity is also calculated and compared for the cases with different jet Reynolds numbers. The jet Reynolds numbers of Re = 200, 600, and 1000 are considered, and the simulation results show that the CIJM achieves very good mixing for the Re = 600 and Re = 1000 cases. It is also found that the Re = 600 case performs slightly better than the other cases in terms of uniformity of the residence time. These quantitative analyses offer useful insights into the mechanism of nanoparticle size control and uniformity afforded by the unique flow physics and mixing characteristics in the CIJMs. [ABSTRACT FROM AUTHOR]

• MgAl-Cys-LDH had plentiful groups beneficial for the adsorption of metal ions. • Mechanisms included precipitation, surface complexation and isomorphic substitution. • MgAl-Cys-LDH presented higher removal efficiencies in real water environment. To understand the interaction mechanisms between heavy metals and functional groups modified nanomaterials, the l -cysteine (Cys) intercalated MgAl-layered double hydroxide (MgAl-Cys-LDH) was designed by a facile co-precipitation method and used to remove Cu(II), Pb(II) and Cd(II) in water solutions. The XRD, FTIR, SEM, TEM, EDS and XPS characterization analyses proved the carboxyl, thio and amido groups were successfully introduced into MgAl-LDH. The possible mechanisms were analyzed by the XPS and XRD spectra and involved the precipitation of metal hydroxides or sulfides, surface complexation with abundant surface groups, and the isomorphic substitution of Mg(II). The adsorption kinetics and isotherms data of Cu(II), Pb(II) and Cd(II) on MgAl-Cys-LDH were well described by the pseudo-second-order kinetic equation and the Langmuir model. The influence factors such as initial solution pH of heavy metals, dosage of MgAl-Cys-LDH, adsorption time and various types of water were investigated, and the results suggested that MgAl-Cys-LDH had potential applications in real wastewater treatment containing heavy metals. [ABSTRACT FROM AUTHOR]

The remediation of Cd-polluted sediment in coastal rivers is essential because of its potential hazards to river and marine ecosystems. Herein, a co-pyrolysis product of contaminated dredged sediment (S@BC) was innovatively applied to cap and immobilize Cd-contaminated sediment in coastal rivers in situ, and their remediation efficiencies, mechanisms, and microbial responses were explored based on a 360 d incubation experiment. The results showed that although S@BC immobilization and capping restrained sediment Cd release to the overlying water, S@BC capping presented a high inhibitory efficiency (66.0% vs. 95.3% at 360 d). Fraction analysis indicated that labile Cd was partially transformed to stable fraction after remediation, with decreases of 0.5%− 32.7% in the acid-soluble fraction and increases of 5.0%− 182.8% in the residual fraction. S@BC immobilization and capping had minor influences on the sediment bacterial community structure compared to the control. S@BC could directly adsorb sediment mobile Cd (precipitation and complexation) to inhibit Cd release and change sediment properties (e.g., pH and cation exchange capacity) to indirectly reduce Cd release. Particularly, S@BC capping also promoted Cd stabilization by enhancing the sediment sulfate reduction process. Comparatively, S@BC capping was a priority approach for Cd-polluted sediment remediation. This study provides new insights into the remediation of Cd-contaminated sediments in coastal rivers. [Display omitted] • Co-pyrolysis product of dredged sediment (S@BC) reduced sedimental Cd release. • S@BC capping could more effectively inhibit Cd release from sediments. • S@BC immobilization and capping posed no adverse effect on sediment bacterial community. • S@BC restrained Cd release by direct adsorption and indirectly altering sediment properties. • S@BC capping was a more promising method for Cd polluted sediment remediation. [ABSTRACT FROM AUTHOR]

The adsorption characteristics and mechanism of Cd2+ on microbial inoculant (MI) mainly composed of Bacillus subtilis , Bacillus thuringiensis and Bacillus amyloliquefaciens , and its potential for remediation Cd polluted soils through batch adsorption and soil incubation experiments. It was found that the Freundlich isotherm model and the pseudo–second–order kinetics were more in line with the adsorption processes of Cd2+. The maximum adsorption capacity predicted by Langmuir isotherm model suggested that of MI was 57.38 mg g−1. Scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS) images exhibited the surface structure of MI was damaged to varying degrees after adsorption, and Cd element was distributed on the surface of MI through ion exchange. X–ray diffraction (XRD) results showed that CdCO 3 was formed on the surface of MI. Moreover, the functional groups (–OH, C–H, and –NH) involved in the adsorption of Cd2+ through fourier transform infrared spectroscopy (FTIR). After applying MI to Cd–contaminated soil, it was found that soil pH, conductivity (EC) and soil organic matter (SOM) increased by 0.84 %–2.43 %, 31.6 %–241.48 %, and 8.11 %–24.1 %, respectively, when compared with the control treatments. The content of DTPA–Cd in the soils was significantly (P < 0.05) reduced by 15.48 %–29.68 % in contrast with CK, and the Cd speciation was transformed into a more stable residual fraction. The activities of urease, phosphatase and sucrose were increased by 3.5 %–45.18 %, 57.00 %–134.18 % and 52.51 %–70.52 %, respectively, compared with CK. Therefore, MI could be used as an ecofriendly and sustainable material for bioremediation of Cd–contaminated soils. [Display omitted] • MI exhibited effectively remediate Cd-contaminated water and soil. • MI can immobilize Cd through ion exchange, precipitation and complexation. • MI reduced the availability of soil Cd and improved soil chemical properties. [ABSTRACT FROM AUTHOR]

Using a co-impregnation technique, Sr-doped hydroxyapatite (HAP-Sr) loaded in magnetic mesoporous carbon (MMC) was successfully prepared. Extensive characterization was performed on MMC, HAP-Sr, and the composite (MMC/HAP-Sr) to determine their properties. In addition, their U(VI) adsorption capacities were thoroughly investigated. The key factors influencing U(VI) adsorption were investigated. In accordance with the results, the equilibrium of MMC/HAP-Sr on U(VI) was reached within 10 min. In addition, the substance's theoretical saturation capacity was 1229.9 mg·g−1. XRD and XPS tests showed the sorption of U(VI) by MMC/HAP-Sr is mainly via precipitation and complexation with hydroxyl (-OH) on the surface. Thus, MMC/HAP-Sr is an excellent adsorbent for the treatment of radioactive wastewater containing U(VI). [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Converting limestone sludge waste into hydroxyapatite rod-shaped particles by hydrothermal method. • The obtained materials were found to be effective adsorbents for Pb2+. • Preparing a novel sorbent with high adsorption capacity of 476.19 mg/g. • This provides a new avenue to address wastewater treatment and limestone sludge. This paper reports on the recycling of the Ca2+ ion-rich filtrate of limestone sludge for use as a raw material in the hydrothermal synthesis of hydroxyapatite (HAp) applicable to the removal of Pb2+ ions from aqueous solutions. Samples of HAp (eco-HAp) were prepared using a range of Ca/P molar ratios (Ca/P MRs) (1, 1.67, 2.33 and 3) and hydrothermal temperatures (393–453 K). Fourier transform infrared spectroscopy revealed the presence of O–H groups and PO 4 3–(ν1) groups (indicative of HAp). Transmission electron microscopy revealed the presence of elliptical surface microstructures. Solid-state nuclear magnetic resonance (NMR) spectroscopy revealed single crystal sites of inorganic phosphorus (31P) and hydroxyls (1H). The adsorption capacity of eco-HAp samples reached 476.19 mg/g within 20 min. The results of adsorption kinetics were characteristic of pseudo-second-order kinetics. Langmuir adsorption isotherms revealed that the Pb2+ adsorption capacity of ecoHAp was 277.77 mg/g, which can be attributed to a synergistic mechanism involving ion exchange, chemical precipitation, surface complexation, and dissolution/precipitation. Taken together, these results demonstrate the potential of eco-HAp as an adsorbent material with broad industrial applicability for the removal of heavy metals from aqueous solutions. [ABSTRACT FROM AUTHOR]

In order to solve the problem of heavy metal-contaminated wastewater and to find a novel application for reeds, reed-derived bio char（RBC）was synthesized at different pyrolysis temperatures under limited oxygen conditions. Elemental analysis, adsorption kinetics, and isothermal models were used to explore the adsorption mechanism. The effects of different pyrolysis temperatures on the adsorption of Cd2+ onto RBC were investigated by SEM-EDS, FTIR, and XRD. The results showed that the adsorption of Cd2+ fitted a pseudo-second-or der model, but could be better described by Langmuir models. RBC synthesized at 500 °C had a high yield and the largest theoretical Cd2+ adsorption capacity, which was as high as 39.05 mg·g-1. SEM images showed a granular structure on the surface of RBC after adsorption and, according to the XRD spectra, peaks of CdCO3 and CdSiO3 crystalline forms appeared. It was, therefore, inferred that Cd2+ could precipitate with CO3-2 and SiO3-2 respectively. In this study, the adsorption mechanism of Cd2+ onto reed biochar was systematically described as the common result of cation exchange, precipitation adsorption, complexation, and Cd-π metal bonding interaction. [ABSTRACT FROM AUTHOR]

A substantial amount of ash is produced after the incineration of sewage sludge which is difficult to manage. Its potential use as a cost-effective adsorbent for heavy metals is beneficial to both waste management and wastewater treatment. In this study, the adsorption kinetics, isotherms as well as the factors influencing the adsorption performance were assessed through batch sorption experiments. The results show that incinerated sewage sludge ash (ISSA) was effective in adsorbing Pb(II) from aqueous solution in a wide pH range (3.00–6.00) due to the combined contributions of ion exchange, precipitation and complexation, which was confirmed by systematic investigation through XRD, SEM-EDX, FTIR, XPS and a sequential extraction procedure (SEP) for Pb(II). Nonetheless, the adsorption of Pb(II) by ISSA would be adversely affected by high ionic strength. The sorption process was fast, and the equilibrium data could be well described by the Langmuir model, the maximum uptake capacity for Pb(II) increased with temperature and the calculated adsorption capacities at 298, 308 and 318 K for Pb(II) were 58.28, 60.06 and 62.42 mg/g, respectively. These findings indicate the ISSA can be recognized as a high-performance adsorbent for Pb(II) removal in wastewater treatment applications. Image 1 • The first utilization of ISSA as a high-performance adsorbent for Pb(II) removal was investigated. • ISSA can remove lead effectively at a wide initial pH range from 3.00 to 6.00. • An adsorption capacity of 62.42 mg/g was achieved at 318 K. • The adsorption mechanisms were elucidated. • The environmental risk of the ISSA after adsorption was evaluated. [ABSTRACT FROM AUTHOR]