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[Display omitted] • A novel dual-layer membrane combining a PSF bottom layer and a PH surface layer incorporated with ZIF-71 nanoparticles was developed. • The dual-layer ZIF-71/PH-PSF membrane possessed high permeate flux. • The dual-layer ZIF-71/PH-PSF membrane exhibited high efficiency for dyeingwastewater treatment. • The mechanism underlying the enhanced MD performance of the ZIF-71/PH-PSF membrane was elucidated. Membrane distillation (MD) is a promising technology for the treatment of hypersaline dyeing wastewater. However, commercial membranes still have limitations such as low permeate flux, membrane fouling, and membrane wetting issue in MD process. Herein, a dual-layer MD membrane was fabricated with a polysulfone (PSF) bottom layer and a poly(vinylidene fluoride-co-hexafluoropropylene) (PH) hydrophobic surface layer incorporated with ZIF-71 nanoparticles. The addition of ZIF-71 was optimized based on the results of surface morphology, contact angle, and MD performance. The incorporation of ZIF-71 nanoparticles into PH nanofiber membranes, along with their dual-layer structure, has led to notable improvements in both permeate flux and rejection performance. The fouling resistance of membrane was further evaluated with model dyeing wastewater as feed solution, which contained four types of dyes and heavy metal antimony. The MD performance of the optimized membranes was also measured with real dyeing wastewater as feed solution. The dual-layer membrane decorated with ZIF-71 nanoparticles significantly outperformed the pristine membrane in treating real dyeing wastewater, exhibiting potential for practical applications. Finally, the underlying mechanism on the improved permeate flux and rejection was elucidated systematically. [ABSTRACT FROM AUTHOR]

• Progress in developing/applying various nanostructured adsorbents has been reviewed. • LDHs, graphene, CNTs, MXenes, MOFs, and ZIFs are very promising HMs adsorbents. • Latest advancements in adsorptive removal of HMs from wastewater have been analyzed. • Adsorption isotherm, kinetics, thermodynamics, mechanism, etc., have been discussed. • Challenges/limitations are highlighted; future research directions are identified. Heavy metals (HMs) are among the most hazardous water pollutants due to their toxic (when ionized in water) and non-biodegradable nature. Although there are several methods that can be used to remove HMs from contaminated water samples, adsorption is one of the most attractive techniques for water decontamination due to its several attractive attributes. However, the efficacy of the adsorptive removal of HMs from wastewater greatly depends on the characteristics of the utilized adsorbents. Recently, nanostructured adsorbents such as layered double/triple hydroxides (LDHs/LTHs), carbon nanotubes (CNTs), graphene-based materials, MXenes, metal organic frameworks (MOFs), and zeolitic imidazolate frameworks (ZIFs) have emerged as attractive tools for the removal of HMs from wastewater. Although there are a few review articles on each of these nanomaterials, comprehensive reviews documenting the applications of all these nanomaterials in one place are still greatly lacking. Additionally, adsorptive removal of HMs is a rapidly evolving field, requiring up-to-date comprehensive reviews in order to analyse, assess, and summarize the scattered information in recently published research articles, making it convenient for researchers and professionals to easily follow the progress in the field. Therefore, the main objective of this article is to comprehensively review recent studies on the adsorptive removal of HMs from contaminated water samples using nanostructured adsorbents (i.e., LDHs/LTHs, CNTs, graphene, MXenes, MOFs, ZIFs, and nanocomposites containing any of these nanomaterials). Besides their synthesis approaches, the adsorption performance of these nanomaterials towards HMs are extensively reviewed. Adsorption kinetics, isotherm, the effects of several adsorption parameters, adsorption thermodynamics, and reusability/recyclability of these nanostructured adsorbents are thoroughly and critically reviewed. Obstacles, challenges, limitations, and remaining knowledge gaps are identified, and future works to address them have been highlighted. Hence, the present article offers a state-of-the-art and comprehensive review of the various aspects of HMs removal from wastewater samples using nanostructured adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • The removal of harmful inorganics and organics by MXenes-based adsorbents were reviewed. • The preparation of MXenes with target surface and structural properties was reviewed. • The adsorption properties are highly dependent on the surface chemistry of MXenes. • Variation of surface terminations and surface modification have profound influence. • Future research should prioritize enhancing the stability of MXenes. Multiple harmful pollutants in liquid are vented into ecosystems due to the rapid expansion of industry, which can be typically divided into two broad categories: inorganic and organic. Adsorption is one of the most prevalent water purification methods, and many different adsorbents have been developed to remove these contaminants. MXenes, a rapidly expanding and diverse family of 2D materials with various applications, have garnered much attention in recent years. MXenes are particularly promising as adsorbents for removing pollutants from aqueous systems due to their unique chemical, physical, and mechanical capabilities, high specific surface area, diverse surface chemistries, and hydrophilic character. Given the rapid advancement of MXenes-based adsorbents, an updated literature review on these materials is urgently needed to provide researchers with a comprehensive understanding of the latest research advancements and developments. The application of MXenes and their derivates in environmental remediation have been reviewed in this work. The adsorption of heavy metals, radionuclides, dyes, pesticides, and pharmaceuticals by MXenes and their derivates was summarized, meanwhile, the effects of surface terminations and the adsorption mechanisms were also analyzed and emphasized. Finally, the challenges and prospects of the MXenes-based adsorbents are discussed. This review summarizes the status of investigations on MXenes-based adsorbents and offers perspectives on their potential development. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elevated temperatures contribute to increased porosity and larger surface area. • Activators exhibit a pronounced effect, creating additional pores and crater. • The highest specific surface area (1282.82 m2/g) is achieved at 750 °C. • As the temperature rises, pores become smaller, resulting in altered morphology. • Langmuir model estimates q max for Lead is 159.071 mg/g. In this research, a highly porous sodium bicarbonate modified biochar was produced by the fast pyrolysis of Chlorella pyrenoidosa biomass. The biochar without modification showed non-porous material characteristics based on the results of N 2 isotherm adsorption–desorption. The modification with sodium bicarbonate successfully enhanced the BET specific surface area of biochar up to 1282 m2/g at a temperature of 750 °C, with microporous surface area of 871 m2/g and external surface area of 411 m2/g. XRD characterization showed broad peak around 24° which indicates amorphous carbon structure that is favorable for adsorption purposes. FTIR characterization after pyrolysis showed an important functional group that should enhance the adsorption process. Following that, a batch adsorption technique of lead synthetic wastewater is used to conduct more tests on its performance. The maximum adsorption capacity of lead (Pb) based on Langmuir model of modified biochar (q max ) is 159.071 ± 23.4008 mg/g. The heterogeneity factor (hf) based on Freundlich model is 0.4671 ± 0.06394, which mainly indicates the physical adsorption. The separation factor (R L) is nearly zero, indicating irreversible nature. The pseudo second order kinetic model showed that the rate of adsorption (k 2) for modified biochar is 0.00931 ± 0.00222 g.mg−1 min−1. Overall, the results demonstrated that in terms of technological feasibility, modified biochar from Chlorella pyrenoidosa met the standards of commercial activated carbon, either based on characterization data or performance results. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-value utilization of SAPs in used disposable diapers. • Synthesis of the proposed adsorbent is green, facile, and cost-effective. • The proposed adsorbent is the first modified-SAP-based one reported to date. • The proposed adsorbent shows superior adsorption capacity towards Cr(VI) The consumption of disposable diaper has increased drastically over the past decades in virtue of its cost effectiveness, user-friendly nature, and excellent skin compatibility. Nevertheless, used disposable diapers are typically fed to landfills with no treatment. This is a huge threat to the environment as superabsorbent polymer (SAP) in disposable diapers are essentially non-degradable under natural conditions. Unfortunately, recycling of SAP remains extremely challenging owing to its crosslinked network structure and ultra-high water absorption capacity. In this study, we propose a novel route for high-value utilization of SAP in used disposable diapers in a 'waste treatment by waste' manner. Specifically, the SAP was modified by polyethyleneimine (PEI) in a facile way (grafting and crosslinking under mild conditions) to develop the SAP-PEI, which is, to the best of our knowledge, the first modified-SAP-based adsorbent reported to date. The results demonstrated that the as-prepared SAP-PEI was superior to most low-cost adsorbents in terms of maximum adsorption capacity towards Cr(Ⅵ) (527.52 mg/g). Meanwhile, adsorption isotherms and kinetics revealed that Cr(Ⅵ) adsorption by the SAP-PEI can be effectively described by the pseudo-second-order model and the Langmuir model. Meanwhile, electrostatic attraction plays a key role in Cr(VI) adsorption by the SAP-PEI, and Cr(VI) are partially reduced to Cr(Ⅲ) in this process. Additionally, the SAP-PEI exhibited excellent reusability as its Cr(VI) removal efficiency decreased by less than 5 % after seven cycles. Overall, the SAP-PEI is a high-performance adsorbent and its application in removal of heavy metals such as Cr(VI) serves as a green and cost-effective approach for high-value utilization of SAP in used disposable diapers. [ABSTRACT FROM AUTHOR]

[Display omitted] • O-FMO exhibited high adsorption capacity and stability under acidic conditions. • As(III) enhanced the adsorption of diverse heavy metals by O-FMO. • Acid-soluble As-Cu and As-Cd complexes on O-FMO were replaced by Pb-As complex. • Metal electronegativity affected trait and formation sequence of As-metal complex. • Pb(II), As(III), and Cu(II) were sequentially recovered from AMD using O-FMO. As(III), a common pollutant in acid mine drainage (AMD), can provide potential active sites for the adsorption of heavy metals on adsorbents. In this study, Pb(II), As(III), and Cu(II) were sequentially recovered from AMD using hydroxyl-enriched Fe-Mn binary oxide (O-FMO) via the in-situ utilization strategy of As(III). The results showed that the prepared O-FMO demonstrated better adsorption performance under acidic conditions than FMO. O-FMO exhibited an outstanding selectivity (＞99.6%) for the removal of Pb(II) and As(III) via the generation of insoluble As-Pb complex in AMD and the immobilized Pb and As could be subsequently separated using respective acid and alkaline solutions. Furthermore, the recovered O-FMO containing residual As could promote the selective removal of Cu(II) (Selectivity ＞98.4 %) from the treated AMD. Mechanism analysis revealed that the oxidized As(V) on the O-FMO played a dominant role in promoting metals adsorption via electrostatic interaction and complexation. Pb(II) can directly form a generally stable complex with H 3 AsO 4 (As(V)) under acidic conditions, thereby replacing the Cu(II) and Cd(II) which only form acid-soluble complexes with H 2 AsO 4 -1 (As(V)). Besides, metal electronegativity affects the traits and the formation sequence of As-metal complexes. Hence, the recovery of metal(loid)s (purity > 98.4 %) from AMD following the order: Pb(II), As(III), and Cu(II) could be achieved by reutilizing O-FMO. This work offers a unique approach for AMD remediation by utilizing pollutants to treat pollution. [ABSTRACT FROM AUTHOR]

• SLMI was used as a green surfactant in ion flotation. • The heavy metals removal efficiency of SLMI was determined. • The three-dimensional fluorescence spectra were analyzed. • SLMI was a more environmentally friendly alternative to SDS. The green surfactant Sodium Lauroyl Methyl Isethionate (SLMI) was employed for the first time in an ion flotation process to effectively remove heavy metal ions (HMs) from simulated wastewater. The HMs removal performance of SLMI was compared with the conventional surfactant, Sodium Dodecyl Sulfate (SDS). The operational parameters, such as surfactant concentration, flotation time, initial pH, and ionic strength, were investigated in the ion flotation process. Results showed that a surfactant concentration of 200 mg/L was particularly effective for Pb removal. A significant enhancement in HMs removal, especially for Ni and Cu, was observed with a flotation time of 30 min, achieving SLMI removal efficiencies up to 97.9 % and 97.8 % for Ni and Cu, respectively. The study also revealed that initial pH was crucial in HMs speciation and removal, with efficiencies exceeding 98 % at pH levels above 8. Additionally, at lower ionic strengths (0 to 0.5 g/L NaCl), HMs removal efficiency remained stable but declined at higher NaCl concentrations. Significant three-dimensional fluorescence spectra variations were observed due to the interactions between SLMI and HMs in ion flotation. Findings from this study suggest that SLMI could be a potential environmentally friendly alternative for conventional surfactant (e.g., SDS) in the ion flotation process for HMs removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning assisted screening method succeed to identify suitable MOFs for Pb2+ removal in aqueous solution. • Ten top-performing MOFs were identified considering solvent environmental effects. • PLD and WEPA were key descriptors for Pb2+ loading by univariate analysis and machine learning. • Two strategies were proposed to design high-performing MOFs for Pb2+ loading in aqueous solution. Developing heavy metal adsorbents with high efficiency is imperative for advanced wastewater treatment. So far, the design of adsorbents has primarily relied on the experimental and molecular simulation methods, which is inefficient and time-consuming due to the vast number of potential materials. This study introduces a machine learning-assisted high-throughput screening strategy to identify optimal metal-organic frameworks (MOFs) for Pb2+ removal in aqueous solution, aiming to guide the design of high-performance MOFs. First, we extracted the structural and chemical properties of MOFs from a database containing 146,205 MOFs and developed a machine learning-guided evaluation method for MOFs. This process led to the selection of 50 high performance MOFs. Considering the effects of water, we further refined our selection to 26 water-stable MOFs by literature data and computational results. Subsequently, top-10 high-performance MOFs were identified, which exhibited high Pb2+ adsorption capacity in aqueous phase. Experimental results using screened MOFs indicated the sequence of Pb2+ adsorption as follows: HKUST-1 (top1) > ZIF-8 (ranked 156) > MOF-808 (ranked 379) > MIL-101(Fe) (ranked 582) > UiO-66 (ranked 862), further validating the effectiveness of our screening strategy. Finally, based on the shared features of the top 10 MOFs, we found that regulation of topology and the coordination of free-standing carboxyl groups in MOFs can strengthen the adsorption for Pb2+. These data-driven findings can offer more rational guidance than experimental approach for the design of novel adsorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • As a hydrothermal medium, acid (HCl, H 2 SO 4 , and H 3 PO 4) helps Cd and Zn in biomass migrate to the liquid phase. • The type and level of acid affects the physicochemical properties of hydrochars. • The safest and most economical hydrochar was prepared at 0.05 mol/L acid dosage. • Hydrochar derived from wood containing HMs can be a safe adsorbent and biofuel. The safe disposal of biomass waste containing heavy metals is a major challenge for the large-scale phytoremediation. In this study, different hydrothermal media (H 2 O, HCl, H 2 SO 4 , and H 3 PO 4) were used to conduct hydrothermal carbonization (HTC) of willow biomass containing Cd and Zn. The cadmium and zinc distribution and behavior, the characteristics and potential applications of hydrochars were investigated. The results showed that Cd and Zn are beneficial to migrate to the liquid phase with the addition of acid. Reaction medium and acid concentration have great influence on the yield, ash content, element content, functional groups, crystalline minerals and thermal stability of hydrochars. In the safe application, the hydrochar produced at 0.05 mol/L H 3 PO 4 has the maximum adsorption capacity for Cd2+(4.497 mg/g) and Cu2+ (49.708 mg/g), respectively. Besides, adding acid improves the energy density of hydrochars with higher calorific values (23.83 – 28.27 MJ/kg), making it a promising biofuel choice. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rice husk biochar was modified with deep eutectic solvent and mixed metal oxides. • Magnetic feature of biochar nanocomposite facilitates separation and recyclability. • Simultaneous adsorption of three main types of pollutants was achieved. • The adsorbent shows an excellent efficiency for Cr(VI), Pb(II) and diclofenac. In this study, ternary recyclable rice husk biochar doped with deep eutectic solvent and Fe 3 O 4 /ZnO nanoparticles (Fe 3 O 4 -ZnO/RBC-DES) was successfully synthesized and used for the removal of Cr(VI), Pb(II), and diclofenac sodium from aqueous solution. The characterization results of several techniques, naming XRD, FTIR, SEM-EDS, TGA, TEM, and surface area analysis, confirmed that the modified nanosorbent surface offered more active adsorption sites, facilitating the Cr(VI), Pb(II), and diclofenac sodium adsorption. Introducing metal oxide nanocomposite (Fe 3 O 4 -ZnO) effectively leads to superior kinetic removal efficiency. At equilibrium conditions, mesoporous FZRBC-DES15 shows maximum adsorption capacity (Q max) of 66.23, 384.62, and 24.33 mg/g for Cr(VI), Pb(II), and DCF, respectively. The adsorption kinetics fit the pseudo-second-order model. The adsorption behavior coincided with homogeneous adsorption materials as reflected by well-fitting the Langmuir model for Cr(VI) and Pb(II) and the heterogenous mechanism for DCF as fit with the Freundlich model. The synthesized adsorbent is an excellent adsorbent that removes selected heavy metal ions and diclofenac sodium from aqueous solutions. It is used in waste resource utilization as it is easily recycled. [ABSTRACT FROM AUTHOR]

• A mild one-step fabrication method of cross-linked GO membrane was proposed. • DA/PEI modification improved the structures and performances of GO membranes. • Flux and rejection simultaneously enhanced for removing heavy metal ions. • GO@DA/PEI 40 membrane exhibited superior anti-fouling performance and stability. Heavy metal ion contamination poses a significant threat to both our environment and human health. Consequently, there is a need for proficient and environmentally friendly remediation techniques to tackle this issue. Among various strategies, membrane-based separation using graphene oxide (GO) laminate membranes has emerged as a promising solution. However, traditional GO membranes have low water permeance, poor selectivity, structural instability, and inconsistent layer spacing. In this study, we cross-linked GO with polydopamine/polyethyleneimine (DA/PEI) using a mild one-step strategy to prepare a GO@DA/PEI membrane for heavy metal ion removal and evaluated the effect of cross-linking duration on the interlayer structure, membrane properties, and heavy metal ion removal performance. The successful formation of a cross-linked network between DA/PEI and GO was proven by various characterization methods. Compared with previously reported GO-based membranes, the prepared GO@DA/PEI 40 membrane exhibited excellent performance, including a peak pure water flux of 326.7 L/m2h and ion rejection of 99.6 % for Cu2+, 93.5 % for Pb2+, and 96.6 % for Zn2+, thereby overcoming the conventional trade-off" effect. The mechanism for the high flux was discussed. The cross-linking reaction between the oxygen-containing functional groups at the edges and basal planes of the GO flakes and DA/PEI were crucial to the high flux. In addition, the GO@DA/PEI 40 membrane had excellent anti-fouling performance in the presence of humic acid and long-term stability under different conditions. Overall, the GO@DA/PEI membrane has good potential for heavy metal ion removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation method selection of BIMCs primarily relies on its iron mineral component. • The use of biochar helps prevent the aggregation or agglomeration of iron minerals. • The presence of iron minerals boosts biochar's ability to adsorb anionic pollutants. • Effective combination of biochar and iron minerals is essential for the synergistic effects. The application of biochar and iron mineral composites (BIMCs) in environmental remediation has demonstrated significant potential and value in recent years. These composites effectively integrate biochar and iron minerals through various processes, achieving synergistic effects between the two components and substantially enhancing the performance in environmental remediation. This review aims to give a comprehensive overview of the synthesis methods, applications, synergetic mechanisms, and research progress of BIMCs in treating toxic metal(loid)s and refractory organics. The effective combination of biochar and iron minerals (rather than simple physical mixing) is a prerequisite for harnessing their synergistic effects. The primary methods employed in the production of BIMCs include mixing-pyrolysis, precipitation, ball-milling, and biological reduction, and the selection of preparation method mainly depends on the iron mineral component and the research purpose. The utilization of BIMCs in environmental remediation is extensively discussed, encompassing their applications as adsorbents, soil amendments, Fenton oxidation catalysts, and persulfate oxidation catalysts. In addition, the prospects of BIMCs in practical engineering applications are discussed, and the challenges of current research are analyzed. The future research can be further in-depth in the aspects of efficient preparation methods, practical engineering applications, performance regulation rules, and synergistic mechanism of BIMCs. The BIMCs have broad application prospects in the field of environmental remediation, and are expected to provide more efficient, economical, and environmentally friendly solutions to treating toxic metal(loid)s and refractory organics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various techniques used for heavy metals elimination in water are systematically reviewed. • Versatile applications of various materials in different treating process are explored. • Insights on design strategies and selection principles of high-efficient materials for different techniques are given. • Interaction mechanisms are discussed from different characterization techniques. • Challenges and prospects of various techniques toward water pollution remediation are presented. Due to the potential perniciousness of heavy metals, wastewater contaminated by them has become the most severe environmental problems. Water pollution poses very negative implications for the survival of living beings. This review summarizes the recent progress of the widely adopted techniques for eliminating heavy metals from aqueous solutions and expatiates their principles, characteristics, and applications. The chemical precipitation, ion-exchange, adsorption, and membrane separation are commonly easy operations, cost-effective, and broadly applicable. Bioremediation, photocatalysis, and electrochemical techniques are environmentally friendly with less secondary pollution and highly adaptable. Herein, the current state and prospects of these techniques for environmental remediation are comprehensively reviewed. The removal efficiency, interaction mechanism, and applicable scene for each strategy are well presented from macroscopic results, advanced spectroscopy characterization, and theoretical calculation. In the end, the challenges of different techniques for heavy metal ions elimination in the future were described. [ABSTRACT FROM AUTHOR]

• A. terreus 2021, WLL-ISO, was isolated from Cu2+-containing wastewater. • The fungus achieves complete Cu2+ removal from 10-50 mg/L solutions. • Self-spheroidization of fungal pellets occurs during heavy metal removal. • The fungus exhibits high adsorption capacity for Cu2+, Zn2+, Fe2+, and Pb2+. • EPS secretion plays a crucial role in fungal pellet formation under Cu2+ stress. This study investigates the potential of Aspergillus terreus strain 2021, WLL-ISO, isolated from Cu2+-rich wastewater, for heavy metal removal and spheroidization. Phylogenetic analysis, supported by biochemical characterization, reveals its close affiliation with A. terreus. The fungus exhibits robust growth and diverse substrate utilization. Notably, it achieves complete removal of Cu2+ from solutions (initial concentrations: 10–50 mg/L) alongside self-spheroidization. The resulting pellets display enhanced settleability and a porous structure conducive to heavy metal adsorption. Langmuir and Freundlich models confirm the fungus's high affinity and capacity for heavy metal adsorption, particularly Cu2+, Zn2+, Pb2+, and Fe2+. EPS analysis reveals significant compositional alterations under heavy metal stress, impacting pellet formation. Three-dimensional excitation-emission matrix spectrum analysis detects activation of humic acid-like organics in response to Cu2+ stress. Moreover, the fungus exhibits promising Cu2+ removal from real wastewater, highlighting its practical potential in heavy metal remediation. The self-aggregating nature of the fungus presents opportunities for the recycling of adsorbents post-heavy metal adsorption, enhancing the sustainability of the remediation process. [ABSTRACT FROM AUTHOR]

• Modulation of crystal surface growth. • Enhancing the active phase of MoS 2 and the ratio of S vacancy. • Alkaline earth metal-doped MoS 2 -based materials as selective adsorbents. • Sr-MoS 2 with a high partition coefficient K d of Pb2+ (31.34 L g - 1 ). It was a challenge to prepare an adsorbent with excellent selectivity for target heavy metals, especially when treating real wastewater contaminated with various heavy metals. In the present study, MoS 2 with a specific binding capacity for Pb, was selected as the substrate material. And alkaline earth metal doped SM(Sr-MoS 2) adsorbent was synthesized via a simple one-step hydrothermal method. The morphology and structure of SM were characterized and the results confirmed that Sr was successfully anchored to MoS 2. In addition, it indicated that Sr played a role in expanding the MoS 2 spacing, increasing the ratio of 1 T phrases, and modifying the crystal growth (such as the growth direction and growth rate). Therefore, it suggested that SM had a high selectivity factor (171.26) and partition coefficient K d (31.34 L g - 1 ). More importantly, SM maintained good adsorption performance (∼90 % removal) after six adsorption–desorption cycles, using NaOH or Na 2 -EDTA as desorbent. Therefore, this work provided a new idea for the preparation of selective adsorbents based on MoS 2 , which was expected to be used for the remediation of Pb2+-contaminated wastewater. [ABSTRACT FROM AUTHOR]

• The significance of wastewater in the degradation of the environment. • Is examined in this review study, with an emphasis on the occurrence. • And effects of heavy metals as contaminants. • Heavy metals harm the environment and people's health. • Because they are poisonous and persistent. Severe environmental impacts of wastewater contamination include ecosystem deterioration and health concerns to people. The significance of wastewater in the degradation of the environment is examined in this review study, with an emphasis on the occurrence and effects of heavy metals as contaminants. Heavy metals harm the environment and people's health because they are poisonous and persistent. It similarly discovers the toxicity and carcinogenicity of heavy metals, placing particular emphasis on the negative consequences these substances can have on ecosystems and living things. The negative consequences on water bodies, soil, and air quality are highlighted as part of an investigation into the effects of Heavy Metal Ions (HMIs) as contaminants on human health and the environment. The analysis also examines the health effects linked to the basis of hazardous heavy metals, which include industrial emissions, runoff from farms, and urban wastewater. The need to eliminate environmentally sourced heavy metals is emphasised given the possible threats to both the ecosystem and human health. This article discusses different techniques and technologies, such as adsorption, membrane filtration, biological methods, and precipitation that can be used to remove heavy metals from wastewater. In the end, combating environmental contamination requires a comprehensive strategy to protect human and environmental well-being. This means putting in place sustainable practices, like appropriate wastewater treatment systems, promoting moral behaviour at work, and encouraging environmental stewardship, to create a sustainable future that puts the health of people and the environment first by making sure that heavy metals are removed and reducing wastewater pollution. [ABSTRACT FROM AUTHOR]

• Vacuum carbothermal reduction activates the smelting slag containing rare earths. • Vacuum carbothermal reduction enriched the residual precious metal. • The melting slag is fully utilized. Spent automotive catalyst is a valuable source of platinum group metals (PGMs), making them crucial secondary resources. Currently, the main process for recovering PGMs from these catalysts is metal capture method. The smelting process would produce a significant amount of residual slags containing various components like SiO 2 , Al 2 O 3 , CaO, Fe 2 O 3 , Na 2 O, as well as high levels of heavy metals including Cr, Pb, and Ni. These slags are considered either solid waste or hazardous waste and usually disposed of in landfills, which can have detrimental effects on the environment. Furthermore, the smelting slags also contain approximately 2–5 % rare earth elements and trace amounts of precious metal elements. In this study, vacuum carbothermal reduction is employed to pretreat the smelting slags. This method not only successfully removes the heavy metal element lead, but also efficiently achieves the recovery of rare earths, and the enrichment of platinum group metals by mineral phase transformation of cerium-zirconium solid solution and in-situ iron capture. The lead removal rate exceeded 99 %, and the grade of precious metals in the enrichment process was approximately 12 times higher than the original material, with a recovery rate more than 90 %. The leaching rate of rare earths also increased from less than 50 % to more than 95 % after vacuum carbothermal reduction. The effect of vacuum carbothermal reduction pretreatment on the smelting slag phase was systematically studied, and the mechanism behind the increasing rare earth leaching rate due to this pretreatment was further analyzed. [ABSTRACT FROM AUTHOR]

• A polarization exfoliation (PE) method is developed to accelerate the exfoliation of the Ti 3 AlC 2. • Double layer forces enhance the exfoliation efficiency with the etchants under the electric polarization. • The core@shell polyvinyltetrazole@MXene/Fe 3 O 4 (PVT@ MXFe) is synthesized as adsorbents. • The PVT@MXFe exhibits an excellent performance of adsorption of toxic metal ions. • The reuse of PVT@MXFe with hyperthermia by coil-wrapped tube can reduce the secondary pollution. The conventional etching method for exfoliating MXene using hydrofluoric acid solution is time-consuming and inefficient in productivity. A double layer force is generated through polarization among the heterogeneous layers of MXene due to their different dielectric properties. The exfoliated MXene by the polarization method in an acidic solution was employed to synthesize magnetic MXene (MXFe) with Fe 3 O 4 nanoparticles. MXFe was coated on polyacrylonitrile microspheres (PANs) as precursors (PAN@MXFe) by Pickering emulsion polymerization. The core@shell polyvinyltetrazole@MXFe (PVT@MXFe) was obtained as the adsorbent after subsequent cyano-tetrazole conversion of PAN@MFs for the removal of toxic metal ions. The maximum adsorption capacities of Hg(II) on the MXFe and PVT@MXFe coating 2 wt% of MXFe were 579 and 324 mg/g, respectively, indicating the high use efficiency of MXFe. At 8.5 kHz of high frequency, hyperthermia occurs on the PVT@MXFe, facilitating the desorption of the toxic metal ions from the adsorbents. Compared with reuse using an acidic solution, the PVT@MXFe can be reused repeatedly 10 times without obvious damage under the AMF. Our proposed polarization exfoliation method not only provides a novel methodology to exfoliate MXene but also develops an ideal adsorbent for universal adsorption, simple separation, stable regeneration, and low secondary pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study pioneers a perfect method for producing silver nanoparticles (Ag-NPs) using peel waste. • The bioactive compounds from Murcott Mandarin peel as natural reducing and stabilizing agents. • Synthesized (Ag-NPs) showed remarkable efficiency in removing Pb from industrial wastewater. • The study highlights the potential of Murcott Mandarin solid residue in water treatment processes. • By integrating agricultural waste recycling with effective nanomaterials for pollutant removal. This study introduces a sustainable and environmentally friendly method for synthesizing silver nanoparticles (Ag-NPs) using waste from Murcott Mandarin peel (Citrus reticulata Blanco × C. sinensis (L.) Obs.). By repurposing agricultural waste as a precursor for nanoparticle synthesis, the research not only reduces waste but also aligns with green chemistry principles. The synthesis process involved extracting bioactive compounds from Murcott Mandarin peel, which acted as both reducing and stabilizing agents during nanoparticle formation. Characterization techniques, including UV–Vis spectroscopy and X-ray diffraction (XRD), confirmed the successful formation of silver nanoparticles. These nanoparticles demonstrated exceptional efficiency in removing heavy metals from metal industrial wastewater, particularly lead ions. Batch experiments revealed significant adsorption capabilities, with lead ions being uptake by silver nanoparticles at a rate of 42.7 mg/g under optimal conditions of pH 5.5 and 60 min of stirring. Additionally, Murcott Mandarin Solid Residue (MM-SR) obtained from the filtration process during Ag-NP synthesis exhibited promising lead ion uptake, reaching 6.6 mg/g under the same optimal conditions. The eco-friendly synthesis route and the efficient heavy metal removal capabilities of silver nanoparticles underscore the potential of utilizing agricultural waste in nanomaterial synthesis for wastewater treatment. This approach not only tackles waste disposal challenges but also generates value-added materials with practical applications in environmental management. Overall, the study emphasizes the importance of exploring innovative and sustainable pathways for nanoparticle synthesis, highlighting the promising role of silver nanoparticles synthesized from Murcott Mandarin peel waste in cost-effective and environmentally benign strategies for heavy metal removal in metal industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

• Montmorillonite /halloysite or metakaolin were used as fillers for UF membranes. • Membranes were used for the removal of nickel and lead from rainwater. • Lead was better removed than nickel. • Adsorption was the main retention mechanism of metals. • Membrane filled with montmorillonite has the lowest fouling affinity. Montmorillonite/halloysite or metakaolin were used as nanofillers for the preparation of ultrafiltration clay-based nanocomposite membranes (CN-membranes). The addition of montmorillonite and metakaolin increased membrane porosity, while halloysite decreased it. Elements of Al, Si in EDS spectra confirmed that clays were effectively embedded in membrane structure. CN-membranes were used for the removal of Pb2+ and Ni2+ from real rainwater in ultrafiltration at 2.5 bar and 5 bar. Higher removal of lead (85–100 %) compared to nickel (56–90 %) can be explained by higher adsorption of lead on membrane structure than nickel during ultrafiltration. Adsorption was a main retention mechanism of both metals. 100 % retention of lead was obtained for all CN-membranes, while PES + MK and PES + Hal were the most effective (90 %) in removal of nickel. Higher TMP resulted in a decrease in the removal of nickel. In case of lead, the effect of TMP was negligible. Flux decline showed that nanocomposite membranes exhibited the lowest fouling than pristine PES. From nanocomposite membranes, PES + MM had the lowest fouling affinity. Moreover, surface properties such as zeta potential, isoelectric point and contact angle of nanocomposite membranes remain almost identical for clean and fouled membranes. PES + MK membrane was prone to regeneration with 2 % HCl. After fifth cycle of UF-regeneration, removal of lead and nickel was 76.3 % and 45.6 %, respectively. [ABSTRACT FROM AUTHOR]

• Potential migration mechanism of HMs revealed during co-pyrolysis of modified kaolin with DS. • Pyrolysis and "dilution effect" synergistically influence the immobilization of HMs. • The addition of modified kaolin increases the proportion of stable HMs, thus reducing the environmental risk. • Phase transitions, pore structure, functional groups, and interactions between inorganic minerals and HMs may play a critical role. The existence of heavy metal in texting and dyeing sludge is one of the potential ecological pollutions. In this study, a series of modified kaolin was applied to co-pyrolysis with DS. The biochar characterization and heavy metal analysis reveal the effects of modified additives on the heavy metal behavior and potential mechanisms. Compared to raw texting and dyeing sludge, the total content of Cu, Zn, Cr, Mn, and Ni increased to a maximum value of 170.63, 451.85, 147.86, 731.69, and 57.91 mg/kg in biochar. The proportion of Cu, Zn, Mn, and Ni in stable fractions increased to 99.23 %, 88.71 %, 53.89 %, and 94.04 %, and the potential ecological risk index of biochar experienced a substantial reduction from 154.45 in DS to 11.18 in DAK. Co-pyrolysis and dilution effects synergistically reduced the leaching of heavy metals and promoted their enrichment in biochar. The Al/Si structural phase transition, pore structure, functional groups, and interactions between inorganic mineral components and heavy metals also were affected by acid-base modification. This resulted in the enhancement of heavy metal stabilization fractions and the reduction of environmental risks. This study aims to present an eco-friendly and efficient strategy to further mitigate the environmental risks associated with HMs in hazardous wastes. In addition, it also provides ideas for the application of modified mineral additives in the field of pollutant control. [ABSTRACT FROM AUTHOR]

[Display omitted] • La-PzDC was designed for heavy metals removal and antibacterial applications. • La-PzDC showed high adsorption: 697.72 mg g−1 for Pb(II) and 398.26 mg g−1 for Cd(II). • La-PzDC fully adsorbed Pb(II) in just 10 min, and its antibacterial efficiency was close to 99%. • La-PzDC exhibited excellent selectivity for Pb(II) and Cd(II). • The coordination mechanism of Pb(II) and Cd(II) was revealed by DFT calculation. Removing heavy metal ions and microorganisms from wastewater remains a persistent challenge in wastewater treatment. The development of a novel metal–organic framework (MOF), synthesized from 2,5-pyrazine-dicarboxylic acid and lanthanide (La(III), Ce(III), Pr(III)), targeting the concurrent remediation of heavy metal and bacterial pollutants in wastewater. La-PzDC demonstrated remarkable efficacy in removing Pb(II) and Cd(II), achieving maximum adsorption capacities of 697.72 mg g−1 and 398.26 mg g−1, respectively. La-PzDC achieved rapid adsorption equilibria—within 10 min for Pb(II) and 20 min for Cd(II), and conformed to the pseudo-second-order kinetics and Langmuir isotherm models. La-PzDC captured Pb(II) and Cd(II) from actual wastewater, and its residual levels met the relevant wastewater discharge standards. La-PzDC also exhibited excellent reusability and selectivity for Pb(II) and Cd(II). The adsorption mechanism through spectroscopic analysis and density functional theory (DFT) calculations, pinpointing coordination with oxygen and nitrogen-containing groups as a key factor. Significantly, La-PzDC achieves nearly 99 % bacterial elimination against E. coli and S. aureus. The above results indicated that La-PzDC has high selectivity, rapid removal capacity and excellent antibacterial activity, offering a new strategy for the dual challenge of heavy metal and bacterial contamination in wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bimetallic MOF i.e. Ag/Cu-MOF was synthesized using a solvothermal method. • The PES membrane performance was successfully improved by the Ag/Cu-MOF. • 1.0 % Ag/Cu-MOF/PES membrane showed 100 L/m2h.bar permeability and high dye rejection. • Ag/Cu-MOF induced antibacterial properties to PES membrane causing fouling reduction. • 92.6%, Pb(II), 99.5% BSA, 96.4% reactive black 5 and 98.4% reactive red 120 rejections. In this study, a novel bimetallic metal organic framework (MOF) i.e. Ag/Cu-MOF was synthesized using a solvothermal method and later incorporated at different concentrations (0.1–2 wt%) using a phase inversion method for modification and antifouling property improvement of polyethersulfone (PES) membranes. The resulting Ag/Cu-MOF characteristics were investigated using different techniques, such as FTIR, XRD, FE-SEM and EDX. The membranes were characterized by FE-SEM, contact angle, porosity, mean pore size, surface roughness and zeta potential. Furthermore, membrane performance was examined using pure water flux, BSA, Pb(II), dye removal and fouling properties. In particular, the results showed that the addition of 1.0 wt% of the Ag/Cu-MOF decreased the water contact angle from 68.5° to 59.6° while enhancing overall porosity from 45.1 % to 56.0 %. The maximum water permeability was obtained with 1.0 wt% Ag/Cu-MOF (ca. 100 L/m2.h.bar) representing 1.9 times higher flux than that of the bare PES membrane due to the hydrophilic nature of the bimetallic MOF. As for the rejection performance, high Pb(II), BSA, reactive black 5 and reactive red 120 rejections values were observed as 92.6 %, 99.5 %, 96.4 % and 98.4 %, respectively. The Ag/Cu-MOF embedded membrane showed antibacterial behavior against Escherichia coli and antifouling properties, causing a considerable decrease in fouling resistance parameters and significant improvement in the antifouling properties of the PES membrane. The results of this study demonstrated that the Ag/Cu-MOF could be a promising material for boosting the polymeric membrane properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel polymer modified biochar composite material with dendritic structure, abundant functional groups and easy recovery was synthesized. • Adsorption capacities for Cr(VI), LY and MG could reach 421.79, 1169.14 and 1231.53 mg/g, respectively. • The material not only quickly adsorbed Cr(VI), but also enabled the concentration of Cr(VI) after adsorption to meet the WHO standard for drinking water. A novel polymer modified biochar composite material (MNBC@p(HGMA- co -PSS- b -AA)) with dendritic structure, abundant functional groups and easy recovery was synthesized, which exhibited excellent removal capacity for Cr(VI), Lemon-Yellow (LY) and Malachite Green (MG). The prepared MNBC@p(HGMA- co -PSS- b -AA) was characterized via thermogravimetric analysis (TGA), scanning electron microscope (SEM) and Fourier transmission infrared spectra (FT-IR), proving to be with abundant functional groups and pore structure. The adsorption capacities for Cr(VI), LY and MG were 421.79, 1169.14 and 1231.53 mg/g, respectively, surpassing the capacities of most previously reported materials in recent years. Additionally, the effects of many factors on adsorption performance were explored. Experimental results indicated that the adsorption of Cr(VI), LY and MG on MNBC@p(HGMA- co -PSS- b -AA) followed pseudo-second-order and Langmuir models. Furthermore, MNBC@p(HGMA- co -PSS- b -AA) still displayed excellent removal capacity for Cr(VI), LY and MG after five reuse cycles. Moreover, different real water samples such as lake water, tap water were used to measure removal efficiency of Cr(VI), LY and MG. The results indicated that removal rates of Cr(VI), LY, and MG were not less than 86.26 %, 98.25 %, and 97.98 %. Meanwhile, MNBC@p(HGMA- co -PSS- b -AA) could maintain removal rate of 85.35 % even after continuously filtering a large number of pollutants solution in adsorption column, revealing its promising applicability for efficient removal of dyes and heavy metal ions. Surprisingly, MNBC@p(HGMA- co -PSS- b -AA) not only quickly adsorbed Cr(VI), but also enabled the concentration of Cr(VI) after adsorption to meet the World Health Organization standard for drinking water. Additionally, FT-IR and X-ray photoelectron spectroscopy (XPS) analysis suggested that adsorption mechanisms for Cr(VI) were hole filling, redox reaction and electrostatic interaction and adsorption mechanisms for LY and MG were hole filling, π–π interaction, π–π electron donor–acceptor (π–π EDA) interaction, electrostatic interaction and hydrogen bond. [ABSTRACT FROM AUTHOR]

Ultrathin MOF nanosheets with multiple binding sites on the surface were rationally designed and assembled, which showed great detection and removal ability of Fe3+. [Display omitted] • A novel MOF nanosheet with multiple binding sites on the surface was rationally designed and assembled, which showed great detection and adsorption ability for Fe3+. • The study represents the first example of MOF nanosheets for simultaneously sensing and removing heavy metal ions. • Possible mechanisms of Fe3+ detection and removal were investigated in detail. • This work provides a guideline for the design and synthesis of MOF nanosheet materials with both detection and removal functions. Heavy metal contamination has become an urgent global concern, posing a significant threat to our environment and health. Hence, it is critical to exploit functional materials for heavy metal ions sensing and elimination. However, the development of multifunctional materials that can simultaneously accomplish the selective detection and removal of the metal ions remains a significant challenge. In this work, a two-dimensional (2D) layered metal–organic framework (LMOF) functionalized with diverse binding sites has been utilized to concurrently detect and remove Fe3+ ions. The LMOF [Zn(hsb-2) (5-aipa)](HSB-W15) was rationally designed and constructed from the mixed ligands of hsb-2 (1,2-bis(4′-pyridylmethylamino)-ethane) and 5-aipa (5-aminoisophthate) under mild condition. In addition, the corresponding ultrathin nanosheets HSB-W15-NS were also obtained by adapting the instant in situ exfoliation (IISEM) method. Owing to the ultrathin nanosheet morphology and an abundance of active sites on the surface, HSB-W15-NS nanosheets can function as an effective fluorescent sensor to detect Fe3+ and Cr3+ ions. Exceptionally, HSB-W15-NS can also be used to selectively capture Fe3+ ions from water, with up to 93 % removal efficiency, and the adsorption equilibrium attained in 5 min. The sensing and adsorption processes were investigated based on kinetic model analysis, Fourier transform infrared spectroscopy, Raman spectrum analysis, density functional theory calculations, and control experiments. This work inspired the development of ultrathin 2D MOF nanosheets for applications in environmental protection. [ABSTRACT FROM AUTHOR]

• Employing ionic liquids (ILs) in conjunction with β-CD-based MNPs for the synergic binding sites. • Achieving rapid and selective removal of anionic PFASs and Cr(VI) from electroplating plant wastewater. • Unveiling the involvement of electrostatic and hydrophobic interactions in the adsorption of PFASs, facilitated through β-CD cavities and ILs cationic group. • Excellent regeneration performance of Fe 3 O 4 -NH-β-CD-BP ILs, under mild cleaning conditions. Herein, we develop a versatile strategy for developing a Fe 3 O 4 -NH-β-CD-BP ILs based sorbent by installing synergistic bonding sites for simultaneous removal of per- and polyfluoroalkyl substances (PFASs) and heavy metals from contaminated water. This sorbent with its quaternary ammonium cation achieved remarkable removal efficiency (∼99 %)for both short and long chain anionic PFASs in pure water as compared to previous β-CD based materials. Moreover, when subjected to a challenging metal salt matrix, the adsorbents revealed that long-chain PFASs primarily relied on electrostatic and hydrophobic interactions, while short-chain PFASs depended solely on electrostatic attractions. The results indicate that the sorbent exhibits outstanding adsorption capacities for PFCAs, PFSAs and Cr (VI) coupled with fast adsorption kinetics featuring equilibrium times 5, 4 and 2 h, respectively. The simultaneous removal of PFOA, PFOS and Cr (VI) in multi-component systems (electroplating plant wastewater) was also determined due to their dual sites rendered by cationic and β-CD groups. The adsorption of PFCAs and Cr (VI) was significantly influenced by the initial pH compared to the sorption of PFSAs. Additionally, the viologen based sorbent also showed better photocatalytic hydrogen evolution activity. In summary, these results revealed the outstanding adsorption capacity and convenient regeneration process make the adsorbent as a promising candidate for efficient and rapid removal of PFASs from other pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • E-Mg/Al-LDH BC was prepared by EDTA and LDH for HMs sorption. • E-Mg/Al-LDH BC exhibited excellent ability to adsorb HMs compare with BC. • Competitive adsorption capacity of Cd(II) far exceeded that of Pb(II) This study has successfully synthesized layered double hydroxide (LDH) biochar (E-Mg/Al-LDH BC) with ethylenediaminetetraacetic acid (EDTA) and examined its adsorption capabilities towards Pb(II) and Cd(II). The results demonstrate that the kinetics of heavy metal removal can be well described by the pseudo-second-order model. The intraparticle diffusion model indicates that the controlling steps for Pb(II) and Cd(II) are not uniform. The adsorption isotherm for Cd(II) conforms to the Langmuir model, while for Pb(II), it adheres to the Freundlich model. The distribution coefficient (K d) shows that Pb has a significantly higher competitive adsorption capacity than Cd(II). Therefore, in comparison to single adsorption, the maximum adsorption capacity of Cd(II) in competitive adsorption decreased by 58.86%, while Pb(II) only decreased by 13.54%. Surface complexation, cation exchange, chemical precipitation, electrostatic interaction, and cation-π bonding are the inherent mechanisms by which E-Mg/Al-LDH BC removes heavy metal ions. E-Mg/Al-LDH BC has the potential to remediate heavy metal-contaminated water, and it also provides insights for the application of modified biochar in the treatment of multi-metal water pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Imine groups in polyaniline chain are the adsorption sites for heavy metal ions. • Localized lone pair electrons of imine group contribute to its chemical affinity. • Polyaniline adsorption is ligand exchange reactions between imine groups and H 2 O. • The strong chemical affinity between H+ and imine group results in H+ competition. In the researches of polyaniline (PANI) or PANI-based adsorbents, views on which nitrogen group has the highest chemical affinity to heavy metal ions and dominates the adsorption process remain in debate. To address this problem, the interaction between different nitrogen groups and heavy metal ions was deciphered exactly via density functional theory (DFT) calculations and experiments. Theoretical calculations reveal that N group, rather than other nitrogen groups within PANI, serves as the primary adsorption site. And the key step of PANI adsorption process is a ligand exchange reaction. In addition, H+ ions with a higher affinity to N group can inhibit the adsorption of metal ions through the consumption of adsorption sites and ion exchange reaction. X-ray photoelectron spectra (XPS) spectra demonstrate that maintaining a reasonably high pH value (pH > 4) proven to be an effective strategy for mitigating H+ competition. This work provides a molecular-level understanding of PANI's adsorption sites, underlying mechanism, and H+ competition for metal ion adsorption by PANI, which is beneficial for advancing the development of PANI-based adsorbents. [ABSTRACT FROM AUTHOR]

• Neutron activation analysis of FA class F was done and its nano-form was elaborated. • Nanoparticles of γ-Fe 2 O 3 were obtained with saturation magnetization of 40.81 emu/g. • A geopolymer nanocomposite was synthesized and upgraded to novel magnetic form. • Batch kinetic sorption tests of heavy metals from aqueous solutions were designed. • Sorption mechanisms onto both synthesized sorbents were predicted. The presented work was constructed to study the merging influence between the as-received fly ash (FA) hollow spheres (FA; 632 nm) and either nano-sized FA (18 nm) alone or combined with magnetic (40.81 emu/g) γ-Fe 2 O 3 nanoparticles (20 nm) into the microstructural features of their resulted geopolymeric nanocomposites (nano-FA-GP and nano-MFA-GP, respectively). The neutron activation analysis proofed that the FA has a Si/Al ratio of 3.37 with a hypothesized sialate-multisiloxo structure of both nanocomposites. Batch kinetic systems were implemented to compare the capabilities of both sorbents to decontaminate simulated wastewaters containing some heavy metal (HM) ions. The percentage uptake, distribution coefficient, and decontamination factor were used as performance measures. Incorporation of the magnetic nano-γ-Fe 2 O 3 into the nanocomposite (nano-MFA-GP) enhanced these measures especially at high temperature, with one order of magnitude where Pb2+ > Cu2+ > Cd2+ > Zn2+ >Ni2+. The transient behaviors of all systems were assessed and analyzed non-linearly revealing that all reactions were chemisorption controlled. Additionally, the intra-particle diffusion model was applied and the sorption reaction of Cu2+ and Ni2+ was exclusively onto the external surface layer of the nano-MFA-GP, at high temperature, while the other systems might be controlled by an additional diffusion mechanism into the interior pore structures. [ABSTRACT FROM AUTHOR]

A multifunctional coating decorated microfiltration membrane achieves simultaneously separation and absorption complex emulsified oily wastewater containing dyes and heavy metal ion. [Display omitted] • A combination strategy for preparing multifunctional superhydrophilic materials. • This substrate-independent coating has outstanding underwater superoleophobicity and superior anti-oil-fouling property. • Upon to water, the oil-fouled materials can keep the surface free of various kinds of oils. • Effectively separation and absorption complex emulsified oily wastewater containing dyes and heavy metal ion. Adsorption and separation are the most important chemical engineering processes for wastewater treatment. Exerting microfiltration membranes as the central separation technology and decorating them with absorption property, forming absorptive membranes, result in the separation and purification of diverse wastewaters in an energy-efficient manner. Herein, a versatile polyanionic coating with superhydrophilicity/underwater superoleophobicity, superior anti-oil-fouling, and efficient charges is acquired through mussel-inspired co-deposition, followed by b-PEI functionalization, N-alkylation, and anionization. Thanks to the superhydrophilicity/underwater superoleophobicity, the as-prepared microfiltration membrane achieves selective separation of oil/water emulsions. Meanwhile, the functional membranes exhibited excellent selective and efficient adsorption capacity for organic dyes and heavy metal ions due to the abundant surface charges. Interestingly, benefiting from superhydrophilicity and considerable surface charges, the as-designed microfiltration membrane can realize selective and efficient simultaneous adsorption and separation of wastewaters with complicated components, including oil/water emulsions, organic dyes, and heavy metal ions by the concept of "achieving three things at one stroke". Such a versatile and feasible strategy could pave a new path for constructing multifunctional membranes for complex wastewater treatment and purification. [ABSTRACT FROM AUTHOR]

A highly luminescent Zn-MOF (PUC7) has been synthesized and successfully characterized by using various techniques. PUC7 displayed selective and sensitive detection and removal of W6+ and V5+ in aqueous media. [Display omitted] • Luminescent Zn-based MOF (PUC7) synthesis via solvothermal method. • Comprehensive characterization using various techniques. • Selective detection of W6+ and V5+ ions with low detection limits. • High quenching constants values indicates sensitivity. • Efficient removal of W6+ and V5+ ions from water. • Adsorption fits Langmuir model, kinetics follows second-order. • Reusability of PUC7 for up to five cycles. • PUC7's potential for decontaminating water from W6+ and V5+. In this study, we present the synthesis and comprehensive characterisation of a novel, luminescent Metal-Organic Framework (MOF) denoted as PUC7, derived from Zn(NO 3) 2 ·6H 2 O, 1,2-di(4-pyridyl)ethylene, and 2-amino-terephthalic acid through solvothermal method. The PUC7 was successfully characterised using many techniques, including single crystal X-ray diffraction, powder X-ray diffraction, FTIR spectroscopy, BET surface area analysis, FESEM imaging, XPS, UV–visible spectroscopy, and zeta potential measurements. Remarkably, PUC7 exhibited high luminescence properties and water stability. The luminescence properties were utilised for the detection of heavy metal ions. Consequently, PUC7 displayed exceptional selectivity and sensitivity towards W6+ and V5+, with impressively low detection limits of 0.17 μM and 0.22 μM, along with high quenching constant values of 2.5 × 105 M−1 and 1.1 × 105 M−1, respectively. Additionally, we explored PUC7′s proficiency in removing W6+ and V5+ ions from aqueous solution, revealing maximum adsorption efficiencies of 476.2 mg/g and 460.8 mg/g, respectively, fitting well with the Langmuir adsorption model and exhibiting second-order kinetics. Encouragingly, PUC7 demonstrated reusability for up to five cycles in removing W6+ and V5+ ions. Altogether, this research underscores the potential of PUC7 as a versatile and promising tool for efficiently detecting and removing W6+ and V5+ ions from water, with implications for environmental remediation and water purification applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignocellulose-based hydrogel-Pd nanoparticles reactor system was synthesized. • Porous LCG/Pd NPs reactor provided a simultaneous adsorption-catalysis strategy. • Catalytic k value of LCG/Pd NPs reactor is 38 times higher than that of Pd NPs. • LCG/Pd NPs reactor exhibited good mechanical strength in separation of catalysts. The separation and reusability of nano-catalysts are paramount for their high-efficiency and low-cost use. Herein, lignocellulose hydrogels (LCG), were fabricated and served as the host matrix for in-situ generated palladium nanoparticles (Pd NPs), creating hydrogel-based Pd NPs reactor systems. The lignocellulose hydrogel-based Pd NPs (LCG/Pd NPs) reactor system possesses the following unique features: (1) lignin present in LCG acts as a "green" reducing agent so that Pd NPs are formed in situ; (2) the in-situ generated Pd NPs are well dispersed in the LCG structure via complexation; (3) the simultaneous adsorption-catalysis process concept is very effective for pollutant remedy: the adsorption of pollutants on the porous LCG effectively increases the pollutant concentration on the reaction sites, where the Pd NPs are co-located, enhancing the catalytic reactions; as a result, a much higher catalytic reaction rate is observed; (4) the LCG/Pd NPs reactor systems are readily reused/recycled after each use. As proof of this concept, the catalytic performance of the LCG/Pd NPs reactor system was demonstrated by the catalytic reduction of toxic heavy metal ions (Cr6+) and organic dye (methyl orange). Results showed that the novel LCG/Pd NPs reactor system exhibited much increased catalytic reduction rates: the pseudo-first-order rate constant (k) is 118 times higher (from 0.018 to 2.129 min−1 at 25 °C) for MO, and 38 times higher (from 0.008 to 0.304 min−1 at 25 °C) for Cr6+, in comparison with the control, under otherwise the same conditions. [ABSTRACT FROM AUTHOR]

• PPy-modified natural eggplant composite aerogel was first developed. • PPy@eggplant possessed impressive shape recovery capacity after absorbing water. • Simultaneous evaporation and adsorption performance was reasonably evaluated. • PPy@eggplant aerogel showed a high and stable evaporation rate of 2.05 kg·m−2·h−1. • A mechanism of simultaneous evaporation and adsorption was proposed. Solar water evaporation has proven to be one of the most effective approaches to generate clean water. However, simultaneous clean water generation and heavy metal ion removal is challenging and urgent for the treatment of wastewater containing heavy metal ions. Herein, polypyrrole (PPy)-modified natural eggplant (PPy@eggplant) aerogel was developed to effectively address the aforementioned problems. The resultant PPy@eggplant aerogel possessed impressive shape recovery capacity after absorbing water regardless of multiple squeezing and twisting, which contributed to usage stability in long-term applications. Moreover, the PPy@eggplant aerogel achieved solar light absorption of 98.48 % due to PPy uniform distribution and multiple light diffraction/scattering in the porous structure (porosity of 92.16 %), excellent water replenishment capacity (water droplet fully spread within 118 ms), and extremely low thermal conductivity (0.039 W·m−1·K−1). Thus, the PPy@eggplant aerogel demonstrated a high evaporation rate of 2.05 kg·m−2·h−1 and a simultaneous Cr6+ adsorption capacity of 27.83 mg·g−1 for treating dye water with Cr6+ ions. Additionally, the PPy@eggplant aerogel preserved the evaporation rate after a 10-h test, indicating long-term stability in practical applications. In conclusion, the impressive shape recovery capacity, high evaporation performance, and satisfactory Cr6+ adsorption ability make the PPy@eggplant aerogel a good alternative for treating wastewater, especially wastewater with heavy metal ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbothermal reduction was proposed as a new method of MSWI fly ash purification. • Excessive carbon was adversed to heavy metal separation for NaCl/KCl condensation. • Zn & Pb in condensate had recovery value for their concentration up to 20% & 7%. • Finally, two paths for ash utilization were proposed for industrial applications. Thermal separation of heavy metals from municipal solid waste incineration fly ash (MSWI FA) is a promising approach for both fly ash purification and heavy metal recovery. However, its commercial viability is hindered by excessive energy consumption. In this study, we introduce carbothermal reduction for MSWI FA treatment as an innovative strategy to enhance heavy metal volatilization and reduce the required heating temperature. By incorporating carbon (FA/Carbon = 1:0.2), the volatilization fractions of Pb, Cd and Zn reached 96.5 %, 100 %, and 63.9 %, respectively, when subjected to 900 °C for 2 h. Remarkably, these volatilization amount surpassed the volatilization fractions attained when raw fly ash (RFA) was independently calcined at 1000 °C for 2 h: Pb (90.2 %), Cd (92.9 %) and Zn (30.2 %). Conversely, Cu volatilization was impeded by carbon inclusion. Comparable trends were shown in washing fly ash (WFA). Notably, concentrated carbothermal reduction led to substantial concentrations of Pb (2.5–7.1 %) and Zn (4.9–20.7 %), rendering them amenable for recycling through metallurgical routes. Intriguingly, higher carbon content (FA/Carbon = 1:0.3) hindered rather than enhanced heavy metal volatilization from RFA. We found that condensation of NaCl and KCl occurred in carbon pores, causing the formation of molten eutectic which trapped the heavy metals at high temperatures. Therefore, more carbon showed more enhancement of heavy metal volatilization from WFA which was free of NaCl and KCl. Ultimately, two comprehensive pathways for the resourceful utilization of fly ash based on carbon thermal reduction were proposed and compared. This study demonstrates carbothermal reduction as an effective approach for simultaneous purification and metal recovery of MSWI FA, exhibiting promising potential for industrial application. [ABSTRACT FROM AUTHOR]

• A MOF-based porous liquid (PLs) was prepared via ion exchange. • MOF-PLs-based Janus membranes exhibited excellent switchable wettability. • MOF-PLs-based Janus membranes delivered ultrahigh fluxes and separation efficiency. • MOF-PLs-based Janus membranes maintained good reusability during cyclic tests. As an emerging material, porous liquids (PLs) have attracted wide attention and are applied in oily wastewater for the effective elimination of heavy metal ions due to their permanent pore structure, mobility, and superhydrophilicity. However, it remains a challenge to further enhance the separation performance of PLs. Here, a novel metal–organic framework (MOF) porous liquid was synthesized and mixed with a polyacrylonitrile (PAN) solution to produce an asymmetrical Janus fibrous membrane by electrostatic spinning technique. Benefiting from the synergistic effect of the electric field and self-migrating properties of MOF PLs, the Janus membranes exhibited ultrahigh flux of 25310.26 L m-2h−1 bar−1, outstanding separation efficiency (reaching up to 99.99 %) in various oil–water emulsions and high antimicrobial activity (>99.9 %). More impressively, the obtained Janus membranes maintained long-term stability, with separation efficiencies consistently as high as 99.5 %. Meanwhile, the porous structure of MOF PLs with abundant active sites and affinity of polyethylene glycol (PEG) flexible chain for metal ions facilitates the adsorption of metal ions with a maximum equilibrium adsorption capacity of 205 mg/g, which is superior to other literature reported. These results demonstrated that the versatile MOF PLs-based Janus fibrous membranes had a promising application prospect in addressing the challenges associated with such wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pb(II) removal capacity of the BC-TJ6 composite was higher than biochar and strain. • BC-TJ6 sequestrated Pb(II) through ion exchange and complexation. • Hydroxyl and carboxyl groups contribute most to Pb(II) adsorption on BC-TJ6. • Pb-OOC and Pb-O bond structures were responsible for Pb binding with BC-TJ6. Microbial immobilization is a new strategy for bio-remediation of heavy metals. However, information regarding immobilization of wild resistant bacteria onto biochar for heavy metal separation is limited. This study proposed the use of wild-resistant bacteria TJ6 in combination with biochar produced from agricultural waste (BC-TJ6) for Pb removal and investigated the associated mechanisms using Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Compared with the theoretical adsorption capacity according to the linear combination calculating by the mass ratio and adsorption capacity of individual component in the composite material, the actual adsorption capacity of BC-TJ6 for Pb(II) was increased by 73.54%. Specifically, the bridge between the bacteria and biochar of Pb(II) may explain the higher observed adsorption capacity of BC-TJ6 compared to theoretical values. EDS analysis based on electron micrograph showed that Pb(II) adsorbed onto TJ6 strain was 0.48%, while that onto biochar component was 0.14%. It indicated that the resistant bacteria contributed more to the adsorption of Pb(II) in BC-TJ6 composites. The FT-IR analysis suggested that the amide, carboxyl, and hydroxyl groups on the surface of the composite were involved in the adsorption of Pb(II). Further, XPS analysis demonstrated that Pb-O (42.12%) and Pb-OOC (27.6%) were the main Pb-molecular structures bound to the surface of the composite. This study is significant for improving the understanding of biochar-wild resistant bacterial combinations for heavy metal adsorption, and can provide guidance for the use of biochar-microbial remediation of heavy metal pollution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The MoS 2 @Ti electrode was successfully prepared using a one-step solvothermal method. • Above 94.5 % Hg2+ was successfully and efficiently reduced by using MoS 2 @Ti cathode system. • The removal efficiency of Hg2+ was studied and predicted by neural network. Although mercury is one of the heavy metal pollutants that endanger human health and the environment, it is also an essential raw material needed for industrial development. We try to use electrochemical reduction method to realize the resource utilization of mercury. MoS 2 @Ti electrodes were prepared using a one-step solvothermal method, and XRD, XPS, SEM and EDS were used to analyze the MoS 2 powder. The prepared highly reactive MoS 2 @Ti electrode was used as a cathode to electrochemically reduce the mercury-containing solution. After a series of single-factor experiments, under the conditions of stirring rate of 400 r/min, electrode spacing of 20 mm, constant potential of 2 V and electrolytic time of 2 h, the removal efficiency of Hg2+ in 10 ∼ 50 mg/L HgSO 4 -10 % H 2 SO 4 solution reached 94.5 % or above. The reaction mechanism of MoS 2 @Ti was investigated mainly by using the indirect reaction of superoxide radicals and hydrogen radicals to achieve the reduction of Hg2+. And the MoS 2 @Ti electrode can still reach 80.0 % removal efficiency after five times of repeated use. A neural network model was used to predict the efficiency of Hg2+ reduction in this system with a high accuracy of RMSE 1.3049 and R2 0.9511. The above study contributes to the realization of the resource utilization of mercury. [ABSTRACT FROM AUTHOR]

• Cl- promotes the Ni-EDTA degradation in-situ in oxidant-free in the Cl-/BDD process. • Both •OH and Cl• contribute to the degradation of Ni-EDTA. • The Cl-/BDD system exhibits excellent removal efficiencies of Ni and Ni-EDTA in the wide pH range. • The Nickel removal and recovery can be achieved simultaneously. Conventional advanced oxidation processes were used to treat heavy metal complexes. However, a considerable amount of oxidants was required to enable effective oxidative degradation, which led to a significant increase of the treatment costs and subsequent difficulties in the sludge disposal. Based on the abundance of anions in heavy metal wastewater, the effects of anions on the in-situ degradation of Ni-EDTA in an oxidant-free electrochemical system with boron-doped diamond (BDD) as the anode were investigated. The presence of Cl- was found to exert a significant effect on improving the degradation process. Moreover, pH had little effect on the removal of nickel (Ni) and Ni-EDTA within a specific pH range (1 < pH < 9). The removal efficiencies of Ni and TOC reached 100 % and 77.45 %, respectively, at pH 2.16 with 0.4 M NaCl electrolyte, 2 mM Ni-EDTA concentration, and a current density of 50 mA/cm2. •OH and Cl• played crucial roles in the removal of Ni-EDTA by disrupting the chelation sites of Ni and EDTA molecules. The released Ni2+ ions could active the H 2 O 2 in-situ generated at the cathode to produce •OH. The formation of the precipitation products such as NiOOH, Ni(OH) 2 , and NiCO 3 in the Cl-/BDD system were conform based on the XRD and XPS analyses, which suggested the possible pathways for the removal of Ni2+ and Ni3+. Finally, the possible degradation pathways of Ni-EDTA were proposed based on the identification of intermediate products using UPLC-MS. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nFe 3 O 4 /persulfate coupled microbial system was developed for Cu complexes removal. • The satisfactory performance was validated in batch and continuous-flow operation. • Microorganisms enhance the Fe(II)/Fe(III) cycle in the coupled system. • Decomplexation, biosorption, and precipitation, are the dominant processes for Cu complex removal. The enhancement of decomplexation efficiency whilst minimizing subsequent microbial process impact is essential in the treatment of refractory heavy metal complexes. Herein, we developed the nano-Fe 3 O 4 (nFe 3 O 4)/peroxydisulfate (PDS) coupled microbial system for the removal of Cu(II)-citrate. Other Cu(II) complexes, such as tartrate, oxalate, and EDTA, were also selected to validate the effectiveness of the coupled system. In batch experiments, the coupled system facilitated the Cu(II)-citrate removal from 21.9 %, 18.9 % to 96.8 % within 120 min as compared to individual nFe 3 O 4 + PDS or biosorption, respectively. Meanwhile, the coupled column was able to remove 86.9 % of copper after fifteen days under continuous flow operation. Impressively, microorganisms could promote the Fe(II)/Fe(III) cycling, thus reducing the usage of PDS. High-throughput sequencing analyses suggest that the coupled system has a higher microbial abundance, which played key roles in eliminating complexed Cu(II). The removal of Cu(II)-citrate in the coupled system involves de-complexation and biosorption, followed by precipitation of all remaining free metal ions. This work provides a feasible strategy potentially applied in efficient treatment of heavy metal complex wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • An innovative manner was used in the co-pyrolysis for more CO 2 consumption. • CP CO2 evaluation was innovatively constructed and realized in the CO 2 -looping system. • More CO 2 entered into pyrolysis products by Ca-based additives for improving CP CO2. • CaO not only improved CP CO2 by 21.2% but also reduced the total HMs at 500 ℃. • Mechanism for CO 2 assisted Ca-based on CP CO2 with temperature was proposed. In this study, the CO 2 -looping system was firstly attempted to build for exploring the effect of calcium-based (Ca-based) additives on pyrolytic characteristics and products in co-pyrolysis of sewage sludge (SS) and biomass. Then, an innovation method for the consumption of CO 2 (CP CO2) evaluation was proposed and carried out in the CO 2 -looping system, in which it was evaluated based on the syngas volume and CO 2 proportion. The results revealed that the addition of CaO and Ca(OH) 2 could significantly improve CP CO2 by 21.2% in the co-pyrolysis of 500 ℃, while the CaCO 3 addition decreased the CP CO2 by 1.0%. Besides, the co-pyrolysis temperature more than 700 ℃ would play more significant role on the CP CO2 than the addition of Ca-based additives. Then the effect of Ca-based types on biochar characteristics was also identified accompanied by the bio-oil composition. Results showed that the CaO and Ca(OH) 2 additives not only increased biochar mass and pH, but also enhanced the dissolved organic carbon content and the variety of dissolved organic matter, and reduced the total HMs content. Meanwhile, it was 15 types of components that was identified in bio-oil by NIST mass spectral library, found that the intensity of heptadecanenitrile and estra-1,3,5(10)-trien-17 beta-ol was influenced by Ca-based additives. Moreover, the CaO and Ca(OH) 2 played important roles for improving the CP CO2 in the CO 2 -looping system, which was further verified by Fact Sage. Finally, the mechanism for the Ca-based additives on CP CO2 was proposed at different co-pyrolysis temperatures. These findings can widen paths for biochar application and development of CO 2 capture materials. [ABSTRACT FROM AUTHOR]

• Toxicity effects of lead salt species on Mn-Ce/Cu-X catalyst were investigated. • Pb species might primarily occupy the active site of Mn and Cu species. • PbCl 2 and PbNO 3 species predominantly affected the Brønsted acid sites. • PbSO 4 and PbCO 3 species mainly impacted the adsorption of NO + O 2. For the sintering flue gas in steel industry, selective catalytic reduction (SCR) of NO x using NH 3 at low temperature in the presence of heavy metals is still a challenge. In this study, the toxicity effects of lead salt species (PbCl 2 , Pb(NO 3) 2 , PbSO 4 , PbCO 3) on Cu-exchanged zeolite X doped with Mn-Ce catalysts (MCCX) were investigated. All catalysts exhibited poor low-temperature SCR performance within 75–225 °C after Pb poisoning, and the poisoning effects of PbCl 2 , Pb(NO 3) 2 , PbSO 4 and PbCO 3 on MCCX catalyst varied. The PbSO 4 had the most serious poisoning on MCCX catalyst, while PbCO 3 had poisoning effect on catalysts even at 300 °C. Lead species poisoning had bad impact on the structure of zeolite X on MCCX catalyst, and caused some agglutination of Cu species. Likewise, the Pb species might primarily occupy the active site of Mn and Cu species and influence the redox property of catalysts, thereby obstructing the redox and oxidation cycles on catalysts surface. In addition, the PbCl 2 and PbNO 3 species predominantly affected the Brønsted acid sites and occupied the Cu or Mn active sites, inhabiting the absorption and conversion of nitrites and nitrates on the catalyst surface. Moreover, PbSO 4 and PbCO 3 species mainly impacted the adsorption of NO + O 2 and the conversion of nitrites and nitrates on the catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • CsgA–Fe 3 O 4 can remove heavy metals from water at low concentrations. • CsgA–Fe 3 O 4 removed 98.73 %, 98.43 %, and 93.00 % of 1 mg/L Cu2+, Cd2+, and Pb2+. • The adsorption rate remained above 80% after six repeated adsorptions. • The high removal rate (>90 %) of heavy metals in the simulated wastewater. Removal of heavy metals from water has been a hot topic. However, few studies have been conducted for the tricky low concentration range. Experimental designs often have heavy metal concentrations much higher than the actual environmental loading, which leads to poor practical results of adsorbent materials. This study showed that amyloid fiber CsgA-Fe 3 O 4 composites are ideal for the removal of heavy metals from water, especially at low concentrations. We constructed CsgA-Fe 3 O 4 composites by fusing short functional peptides that specifically bind to Fe 3 O 4 magnetic nanoparticles. The CsgA-Fe 3 O 4 composites achieved 98.73 %, 98.43 %, and 93.00 % removal of 1 mg/L Cu2+, Cd2+, and Pb2+, respectively. Moreover, the adsorption rate remained above 80 % after six repeated adsorptions, indicating that CsgA-Fe 3 O 4 was highly reusable. Meanwhile, the high removal rate (>90 %) of heavy metals in the simulated wastewater demonstrated the excellent environmental stability of CsgA-Fe 3 O 4. Finally, by FT-IR and XPS characterization, we found that the adsorption mechanism of CsgA-Fe 3 O 4 is mainly the complexation of surface oxygen-containing functional groups and heavy metal ions. In general, the CsgA-Fe 3 O 4 composite is an efficient, inexpensive, and sustainable adsorption material for mitigating low concentrations of difficult-to-treat heavy metal pollution in water bodies. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 nanoparticles-modified hierarchically porous carbon (Fe 3 O 4 NPs/HPC) was synthesized. • Fe 3 O 4 NPs/HPC delivered high performance in capacitive deionization and heavy metal removal. • Cd(II) uptake includes electrosorption and electrodeposition but only electrosorption for Pb(II). • Fe 3 O 4 NPs/HPC exhibited a high selectivity for the removal of Pb(II) from NaCl solution. Capacitive deionization is an efficient technology for water purification and treatment. The electrode material is crucial to improving the performance of capacitive deionization. Herein, Fe 3 O 4 nanoparticles-modified hierarchically porous carbon (Fe 3 O 4 NPs/HPC) was successfully synthesized by the pyrolysis of waste Camellia oleifera shell coupling with the post-modification. Owing to its unique structure and composition, the as-prepared Fe 3 O 4 NPs/HPC delivered great potential in capacitive deionization and heavy metal removal. Under the current density of 0.5 A g-1, the Fe 3 O 4 NPs/HPC electrode showed a high specific capacitance of 134.5 F g−1 in 1 M NaCl solution, much more than the bare HPC electrode of 99.9 F g−1. In addition, the Fe 3 O 4 NPs/HPC electrode exhibited excellent cycle stability with negligible loss of capacitance after 1000 cycles at 2 A g-1. At an operating voltage of 1.2 V, the Fe 3 O 4 NPs/HPC electrode released high uptake capacity of 34.22 and 39.52 mg g−1 for Cd(II) and Pb(II) ions, respectively. XPS spectra and competitive adsorption demonstrated that Cd(II) was mainly removed by the oxygen-containing groups of HPC through an electrosorption coupling with an electrodeposition multilayer process, but Pb(II) was uniformly adsorbed on the active sites including the oxygen-containing groups of HPC and the modified Fe 3 O 4 NPs by a monolayer electrosorption process. The impressive results indicate that the as-prepared Fe 3 O 4 NPs/HPC composites possess potential for the selective removal of heavy metal ions from saline wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • The process of separation and purification of uranium under complex anion and cation coexistence conditions was established. • CO 3 2− could capture UO 2 2+ in UO 2 SO 4 and UO 2 HPO 4. • The presence of CO 3 2− could convert insoluble uranium species to soluble ones to improve the retention of uranium. • The removal factors of Co, Ni, and Cd could reach 1.6 × 103, 2.1 × 103 and 5.1 × 103. The selective separation of uranium from uranium tailing wastewater is of great importance for environmental protection and nuclear energy development. The complexation of Cl−, SO 4 2−, NO 3 –, and PO 4 3− with UO 2 2+ seriously hindered the achievement of this goal. Herein, a process for achieving it with the coexistence of anions and cations by shielding the influence of anions was designed. Thermodynamic calculations indicated that CO 3 2– could enhance the retention of uranium in the solution by complexing with UO 2 2+ and capturing UO 2 2+ in UO 2 SO 4 and UO 2 HPO 4 to form water-soluble uranyl-carbonate. The capturing ability of CO 3 2– was not diminished by the increase in anion concentration. And the electrochemical experiments revealed the high efficiency of uranium electrochemical extraction in the above system. In addition, the results showed that uranium could be separated from Co2+, Cd2+, and Ni2+ ions under the coexistence of Cl−, SO 4 2−, NO 3 –, and PO 4 3−, thus achieving the selective separation of uranium in the wastewater. And the retention ratio of impurity cations in the liquid phase after separation was less than 0.003. Overall, this method provides new insights into the selective separation of uranium and heavy metal removal in real uranium tailings wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-pyrolysis of sewage sludge with CaSO 4 (SSCB) largely enhanced Pb(II) removal. • SSCB is able to remove 152.7 mg/g of Pb, superior to most reported biochar. • SSCB shows good anti-interference for Na+, K+, Mg2+, Cl−, NO 3 –, and Ac−. • Ion exchange and mineral precipitation contributed to 65.6% of Pb adsorption on SSCB. Lead (Pb) is a toxic heavy metal posing potential harm to the environment and human health. In this study, Pb(II) adsorption performance of co-pyrolysis biochar derived from sewage sludge and gypsum (CaSO 4) was first investigated. The anti-interference to environmental factors was investigated, with the underlying mechanisms being explored quantitatively. The maximum Pb(II) adsorption capacity of co-pyrolysis biochar (SSCB, 152.66 mg/g) was largely improved compared to single sewage sludge biochar (SSB, 29.95 mg/g) at a dosage of 1 g/L and initial pH of 6.0. Model analysis results indicated that monolayer sorption, chemisorption, intraparticle diffusion and endothermic processes were involved in the adsorption process. Among the tested co-existing ions, Fe2+ and NH 4 + mostly disrupted the Pb(II) removal. Mineral precipitation (37.55%) and ion exchange (28.05%) were calculated as the major adsorption mechanisms (65.60%) for Pb(II) removal using co-pyrolysis biochar. SSCB showed better reusability for Pb(II) removal in 5 regeneration cycles. This work provides fundamental references for the utilization of solid wastes via co-pyrolysis to biochar for heavy metals removal towards sustainable development. [ABSTRACT FROM AUTHOR]

[Display omitted] • From nickel waste solution to hydrogen storage alloys. • Process of hazardous Ni removal for preparation of nickel electrolyte. • Electrolytes modified with ammonia to improve electrochemical properties of Ni-AB 5. • Improvement in electrocatalytic properties of AB 5 alloys by Ni from waste solution. In light of the need to protect the environment from hazardous heavy metals, waste management is becoming not just a proposal but a necessity for the reduction of wastewater toxicity and, additionally, a value-added substitute for processes of extracting raw materials from primary sources. This article demonstrates the feasibility of using critical and hazardous element as Ni(II) from industrial nickel waste solutions to produce hydrogen storage alloys (HSA), perfectly fulfilling the circular economy assumptions. The hydrometallurgical process proposed for the preparation of the Ni-containing electrolyte (NiE) from the waste solution included the following stages: diffusion dialysis, Cr(III) and Al(III) hydroxide precipitation, extraction to separate Co(II) from Ni(II), and the organic phase regeneration by Co(II) stripping with dialysate. The raffinate after extraction performed as NiE (∼10–15 g/dm3 Ni(II), 0.1 g/dm3 Co(II)) for the preparation of HSA. However, to improve the quality of Ni deposit on NiCo foam or steel plates, NiE should be modified with an ammonia solution (to pH ∼ 12). A better voltammetric characteristic of the modified electrodes (25–30 percentage points higher peaks resulting from NaBH 4 electrooxidation), compared to those unmodified was reported. It was proven that the electroactive materials obtained showed high catalytic performance for the borohydride oxidation reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified semi-carbonized plant fibers have high heavy metal adsorption capacity. • The maximal heavy metal ion adsorption capacity presents Zn(II) > Cd(II) > Pb(II) • The optimum adsorption conditions are 30 °C, pH = 6, and ionic strength of 0.1 mol/L. • Heavy metal adsorption is a spontaneous, endothermic, and entropy-increasing process. • Specific surface area and cation exchange capacity remarkably affect the adsorption. Highly efficient remediation materials can treat wastewater contaminated by heavy metals. In this study, semi-carbonized plant fiber (Spf) and chemical fiber (Spf) were prepared as the research material. Dodecyl dimethyl betaine and chitosan were used to singly modify semi-carbonized fibers (Sfs). Then, the single-modified Sfs were remodified by sodium alginate to produce composite-modified Sfs. The microscopic morphology of the tested materials was studied by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, energy dispersion spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and specific surface area (S BET) detection. The selective adsorption effect of the tested materials on water polluted by multiple heavy metals was studied, and the effects of temperature, pH, and ionic strength were compared. SEM, FTIR, and TG results proved that single and composite modifiers were modified on the surface and changed the surface properties of Spf and Scf. The metal ion adsorption capacity of modified Spfs was higher than that of modified Scfs. The maximal adsorption capacity of metal ions on test materials presented the trend of Zn(II) > Cd(II) > Pb(II). The optimum adsorption conditions were 30 °C, pH = 6, and ionic strength of 0.1 mol/L, and the adsorption process was a spontaneous, endothermic, and entropy-increasing reaction. Electrostatic adsorption, precipitation, complexation, and ion exchange were the forms of adsorption for heavy metal ions. S BET and cation exchange capacity of the modified Sfs were the key factors that determine the adsorption capacity of heavy metal ions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new extraction solution was prepared for the selective recovery of Cr. • The charged state of metal ions was adjusted using an in-situ reduction mechanism. • Improved FCDI can recover both Cr and Cu from wastewater simultaneously. • Membrane performance can be restored through acid washing to ensure long-term operation. Recovering valuable metal resources from industrial wastewater has environmental and economic significance. Flow-electrode capacitive deionization (FCDI) has been successfully used to remove salt and heavy metals. However, the use of this technology in heavy metal treatment has several limitations, including low selectivity, poor long-term stability, and production of low-quality metal products. In this study, a new strategy for recovering chromium (Cr) from wastewater was proposed using an in-situ reduction method. A liquid membrane chamber (LMC) was introduced into a classic three-chamber FCDI and an extraction solution containing Na 2 SO 3 and NaCl was used to capture Cr in wastewater. During FCDI operation, the CrO 4 2− ions entered the LMC were immediately reduced to Cr3+ and retained in the extraction solution. Completing anions (i.e., Cl−) in the extraction solution maintained the concentration of SO 3 2− ions, and thereby reducing the consumption of reagents. The improved FCDI system exhibited satisfactory separation performance and high stability during semi-continuous operation. Freshwater, Cr, and copper were obtained in the separation chamber, LMC, and flow electrode chamber, respectively. The facile approach may open the doors for the separation and recovery of metal resources from water/wastewater with high scalability and universality. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bifunctional CS/DS@ZIF-8 microspheres were prepared by electrospray method. • The microspheres grow the MOFs layer in situ to improve the interface contact. • The maximum adsorption capacities of Pb2+ and Cu2+ were 340.94 mg/g and 308.27 mg/g. • CS/DS@ZIF-8 has excellent antibacterial properties, easy to recycle and reuse. • Reveal the adsorption and antibacterial mechanism of bifunctional microspheres. A bifunctional composite microsphere adsorbent with high adsorption and antimicrobial activity was synthesized by combining zeolite imidazolate framework (ZIF-8) chitosan microspheres doped with silica (CS/DS) prepared by electrospraying method for removing heavy metal ions Pb2+ and Cu2+. The samples were characterized by chemical, morphological, thermal behavior, specific surface area and pore size analysis. Compared with chitosan microspheres and CS/DS, CS/DS@ZIF-8 has good crystallinity, high specific surface area, multi-pore size distribution, better thermal stability and more active groups. The adsorption process of Pb2+ and Cu2+ on CS/DS@ZIF-8 conformed to the Langmuir model and Pseudo 2nd kinetics model, of which the maximum adsorption capacities were 340.94 mg/g and 308.27 mg/g, respectively, which were better than those of CS and CS/DS microsphere adsorbents. At the same time, the composite microspheres have excellent antibacterial properties and have application potential in solving practical wastewater treatment. It is worth mentioning that CS/DS@ZIF-8 maintains 81.3 % and 72.9 % adsorption rates for Pb2+ and Cu2+ after five cycles. This study aims to help design new bifunctional adsorbents with the ability to remove chemical and biological pollutants to promote practical application scenarios. [ABSTRACT FROM AUTHOR]

• Regeneration of chitosan adsorbents after heavy metal adsorption is reviewed. • Desorption ability of different desorption agents is summarized. • Desorption mechanism of heavy metal ions from chitosan-based adsorbents is described. • Factors affecting regeneration of chitosan adsorbents are highlighted. Adsorption of heavy metal ions on chitosan-based adsorbents has been extensively investigated. However, few studies explored the feasibility of desorbing and regenerating chitosan. Adsorbents used after adsorption of heavy metals are discarded, and this practice exacerbates the solid treatment problem. Regeneration and reuse of exhausted adsorbents should be considered to operate environment-friendly and cost-effective adsorption. This review was performed to summarize the desorption of heavy metal ions and possible regeneration of chitosan-based adsorbents using various desorption agents such as acids, alkalis, salts, and chelating agents. It was found that the highest desorption efficiencies obtained by acidic eluents. The percentage use of desorption agents for desorbing followed the order of acids (49.3%) > chelators (26.9%) > alkalis (14.9%) > salts (8.9%). Moreover, the proper desorption time were estimated to be 0.84 by 1.37 h. Beneficial information is provided for regeneration and recovery of chitosan adsorbents. [ABSTRACT FROM AUTHOR]