Removal of heavy metal ions from wastewaters: a review

Hierarchical V2O3 spiny hollow nanosphere for efficient adsorption of precious metal ions in complicated matrices

Treatment of precious metals in electronic waste has attracted tremendous attention and is essential for both environmental protection and resource sustainable development. In this study, a novel adsorbent for precious metal ions, V2O3 spiny hollow nanospheres (p-V2O3 SHN), was synthesized through a one-step hydrothermal-assisted methodology for the adsorption of Au(III), Ag(I), Pd(II), and Pt(IV) from the leaching solution of electronic waste. The results reveal that the p-V2O3 SHN hierarchy was successfully constructed with a hollow structure and dense spiny morphology. The prepared p-V2O3 SHN can effectively remove precious metal ions such as Au(III), Ag(I), Pd(II), and Pt(IV), with the selective capture order being Au(III) > Ag(I) > Pt(IV) > Pd(II) > other metal ions. This superior adsorption capability can be attributed to the multi-diffusible, intermingled composition, and numerous active sites decorating the p-V2O3 SHN hierarchy, facilitating the uptake of Au(III), Ag(I), Pd(II), and Pt(IV) ions from electronic waste. The Langmuir model provided a better fit for the uptake process, revealing maximum uptake capacities of 833.33 mg/g for Au(III), 370.37 mg/g for Ag(I), 42.01 mg/g for Pd(II), and 77.51 mg/g for Pt(IV) on p-V2O3 SHN. Remarkably, p-V2O3 SHN exhibited a robust affinity for the adsorbate due to the presence of surface defects and reduction reactions. The new p-V2O3 SHN also demonstrated good reusability for three sorption cycles, highlighting its potential for electronic waste treatment. Due to its facile synthesis and excellent efficiency, hierarchical p-V2O3 SHN presents itself as a promising candidate for the selective uptake of Au(III), Ag(I), Pt(IV), and Pd(II) from electronic waste.

Preparation of porous sustainable adsorbent and its adsorption behavior for Pb2

Using granulated blast furnace slag as raw material, chitosan and NaCl as modifier, chitosan modified granulated blast furnace slag based porous geopolymer (PCG) was prepared under the activation conditions of NaOH and sodium silicate. It was used to wrap different types of lightweight aggregates to obtain PCG-lightweight aggregate shell-core structure (PCG-L). PCG-L was used for the adsorption of Pb2+. Firstly, the influencing factors on the adsorption performance of the main component materials (PCG, lightweight aggregates) of PCG-L were studied. Then, the static adsorption properties and sustainable adsorption properties of Pb2+ by different shell-core structures were investigated. The relationship between the water absorption characteristics of the paste and the aggregate and the adsorption characteristics of PCG-L towards Pb2+ was established. The adsorption kinetics, adsorption isotherms and adsorption thermodynamics were analyzed. Finally, the adsorption mechanism of PCG-L was discussed by Zeta analyzer, FT-IR, EDS, XPS and MIP. The results indicate that as chitosan (0-2 wt%) and NaCl (0-60 wt%) increase, the saturated adsorption capacity of PCG for Pb2+ rises (98.57-159.93 mg/g). The Pb2+ adsorption capacity of lightweight aggregate (0.34-1.21 g/dm3) increases with its water absorption (0.2-15.0%). Under the premise that the water absorption rate of aggregate is greater than that of PCG, the higher the water absorption rate of the two, the stronger the adsorption capacity of the matching PCG-L, the maximum adsorption capacity of A2N30-H is 5.12 g/dm3 and it can still maintain a high removal rate after 40 cycles of adsorption. PCG-L adsorption via ion exchange, electrostatic attraction, surface complexation, and pore fixation.

Applications of protein-based nanomaterials in mercury detection and removal: advantages and challenges

Mercury is one of the most toxic heavy metals because it can be accumulated in the human body by the food chain and may induce severe influences on food safety and human health. The detection and removal of mercury are of great importance. Traditional methods have some inherent disadvantages, such as the expensive, time-consuming, and producing secondary pollution. Hence, it is highly desirable to develop novel methods for mercury detection and removal. Protein-based nanomaterials with excellent optical, enzymatic, mechanical, and electronic properties have been developed for mercury detection and removal with high efficiency and selectivity. The reported methods based on protein nanomaterials have allowed the detectability down to nanomolar concentrations or lower levels. The removal efficiency of mercury can reach up to 90%, proving their practical applications in natural water or food samples. This review highlights the current advances in the nanomaterials constructed from proteins for mercury detection and mercury removal. Furthermore, the current challenges and prospects in this research field are also discussed in-depth to provide an overview for future research directions.

Assessing the spatial distribution and sources of heavy metal pollution in the snow cover: A case study from Pavlodar, Northeastern Kazakhstan

This study assesses heavy metal contamination in the snow cover of northeastern Kazakhstan by analyzing both the melted filtrated water and the solid sediment after filtration near various pollution sources. The research examines the impact of oil refining, thermal power plants (northern industrial zone), aluminum production (eastern industrial zone), and transportation on heavy metal dispersion. Results indicate that Zn, Cr, and Pb concentrations in the solid phase of snow in residential areas exceed those in industrial zones, reaching 436.6, 259.1, and 218.6 mg/kg, respectively. The highest overall concentrations were found for barium (949.4 mg/kg) and manganese (638.1 mg/kg). In the liquid fraction (meltwater), Zn (58.6 μg/l) and Sr (34.8 μg/l) were predominant, while Mn (28.3 μg/l) was the main pollutant in the eastern industrial zone. Dust load values in the snow cover ranged from 42.3 to 418.5 mg/m²/day, with the highest pollution load observed for Cd, Pb, and Mo. Despite variations in dust load across the city (135.5 mg/m²/day in the northern industrial zone, 152.3 mg/m²/day in the eastern industrial zone, and 147.1 mg/m²/day in residential areas), the overall dust pollution level remains low. However, a sanitary-hygienic assessment revealed that most heavy metal concentrations in snow exceed maximum permissible levels for soil in areas influenced by industrial facilities and transportation, except for Mo, V, and Mn. The ecological risk index of snow pollution in Pavlodar was calculated at 192.13, indicating a high potential ecological risk. These findings highlight the importance of snow as an indicator of environmental pollution and the need for continuous monitoring to assess urban contamination trends.

Optimization of facile synthesis of xanthan gum xanthate based hydrogel for the capturing of heavy metal ions from aqueous solutions

This study investigated the elimination of Co2+, Ni2+ and Cu2+ ions from water using a mesoporous, cost-effective, reusable, biodegradable and efficient xanthan gum xanthate-based hydrogel (XGmXHs hydrogel) as an adsorbent. The XGmXHs hydrogel was prepared via free radical polymerization process with varying the ratios of 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) as monomers. These ratios were optimized based on grafting efficiency, swelling capacity and point of zero charge (ΔpHPZC) analysis. The results demonstrate that the XGmXHs hydrogel containing copolymer of HEMA: AA in a 1:3 ratio is optimal for grafting on xanthan gum (XGm) during polymerization process. The 1:3 ratio of monomer grafted on xanthan gum xanthate (XGmX) is referred to as XGmXHs-3 hydrogel. The XGmXHs-3 hydrogel showed a consistently negative surface charge across a diverse pH range, resulting the AA content was enhanced. Consequently, the swelling and adsorption capacity of the XGmXHs-3 hydrogel is significantly high. The optimum swelling capacity of the XGmXHs-3 hydrogel was found 40,128 % in water at pH 11. The maximum removal efficiency was 92.21 % for Co2+, 95.45 % for Ni2+ and 98.30 % for Cu2+ ions at pH 7. According to isothermal studies, the adsorption data aligns most closely with Langmuir isotherm model, resulting the adsorption capacities of 358.42, 469.48 and 555.55 mg/g Co2+, Ni2+ and Cu2+ ions, respectively. The adsorption kinetics were consistent with a pseudo-first-order kinetic model, showing rate constant of -2.6 × 10-2, -4.0 × 10-2 and - 6.3 × 10-2 min-1 for Co2+, Ni2+ and Cu2+ ions, respectively. The desorption efficiencies were 64.76 % for Co2+, 68.83 % for Ni2+ and 72.11 % for Cu2+ ions to the XGmXHs-3 hydrogel after being regenerated for the fifth cycle.

Bromide accelerates oxidation of selenite by unactivated peroxymonosulfate: PH-dependent kinetics, mechanism and pathways

Selenium (Se) is an essential trace element that is toxic to humans in a relatively small excess. In natural waters it occurs mainly in inorganic form as Se(IV) and Se(VI) oxyanions with the former being more toxic at high levels. With the increasing use of advanced oxidation processes in drinking water treatment, the oxidation of Se(IV) with unactivated peroxymonosulfate (PMS) has been investigated, but the role of bromide (Br-) on the oxidation of Se(IV) during reaction with unactivated PMS remains unknown. In the present work, several influencing factors on this reaction are reported, including PMS and Se(IV) concentrations, pH, Br-, and natural organic matter (NOM), on the oxidation of Se(IV), as well as the influence of different water matrices. Results show that the second-order rate constant for reaction of Se(IV) with PMS increases with increasing pH (5.0-10.0) from 0.02 to 0.33 M-1s-1, and that Se(IV) oxidation occurs mainly via a direct oxidation pathway. This increases with increasing initial concentrations of PMS and Se(IV), but is inhibited by the presence of NOM. However, the presence of Br- significantly enhances Se(IV) oxidation at circumneutral pH, but has negligible effect in alkaline conditions. It is proposed that Se(IV) oxidation by PMS involves formation of a hypobromous acid/hypobromite (HOBr/OBr-) intermediate in the presence of Br-, and its formation is supported by DFT calculations. Based on these results, a kinetics model for Se(VI) formation in bromide-containing water has been developed. Also, compared to the Br-/NOM/PMS system, the presence of Se(IV) inhibited the formation of brominated disinfection by-products (i.e., bromform and tribromoacetic acid). Overall, these results help improve our understanding of the behavior of selenium in water containing Br- during a common oxidative treatment process.

Calixarene-based cryopolymers: a versatile smart materials platform suitable for both air and water remediation

Environmental pollution caused by the release of hazardous chemicals into air and water poses serious risks to ecosystems, public health, and infrastructure. Addressing these challenges requires innovative materials capable of both detecting and removing diverse pollutants. However, most current materials are designed to target either air or water pollutants, leaving a gap in multifunctional solutions. This study presents a pioneering approach to bridge this gap by introducing two novel calixarene-based cryopolymers, combining the macroporous structure of cryogels with the recognition capabilities of calixarenes. The synthesized materials were found to be valuable tools for detecting and capturing pollutants in both air and water, taking advances from a dual mechanism of absorption: by chelation through the acidic functionality inserted on calixarene scaffold and by a host-guest complex formation with calixarene cavity through cation-π interactions. As an additional advantageous property, they have the ability to detect the presence of NO2 in the air through an evident color change. These multifunctional materials represent a breakthrough in environmental remediation, offering a single platform for addressing pollutants in air and water, marking a step forward in pollution management technologies.

Development of sulfonated polystyrene resin-supported tungsten oxide for Pb2+ ion sequestration

A sulfonated polystyrene resin-supported tungsten oxide (SO3-PSWO) was synthesized and evaluated for its efficiency in removing lead (Pb2+) from aqueous solutions. Morphology, phase purity, structural properties, thermal stability, and elemental composition of SO3-PSWO, are evaluated using SEM, XRD, FTIR, TGA, and CHNS analyzers. The ICP-OES technique was utilized for quantitative measurements of the Pb2+ ions. The influence of key parameters such as pH, adsorbent dose, contact time, metal ion concentration, temperature, and interference of competing ions on Pb2+ removal is systematically investigated. Under optimum conditions (pH 3.5-5.5), SO3-PSWO achieved a maximum Pb2+ removal efficiency of 99.7% within one hour and demonstrated an exceptional adsorption capacity of 386 mg g-1, as described by the Langmuir isotherm model. Kinetic analysis revealed a pseudo-second-order mechanism, highlighting chemisorption as the predominant process. Thermodynamic studies indicated an exothermic and spontaneous adsorption behavior. With its easy synthesis, cost-effectiveness, rapid kinetics, high adsorption capacity, and superior efficiency, SO3-PSWO emerges as a promising material for the remediation of Pb2+ contamination in water treatment applications.

Synthesis and adsorption performance of a novel pyridinium-functionalized hypercrosslinked resin for the removal of chromium(vi) ions

This study presents the synthesis and characterization of a novel anion exchange hypercrosslinked resin (HPR1) designed for the removal of high-concentration hexavalent chromium Cr(vi) from aqueous solutions. The resin was synthesized via a one-step Friedel-Crafts alkylation reaction using a low-crosslinking copolymer of divinylbenzene and vinylbenzyl chloride (DVB-co-VBC), prepared by suspension polymerization with toluene as a porogen. The successful incorporation of pyridinium groups into the resin network was confirmed using elemental analysis, FTIR spectroscopy, and solid-state 13C NMR spectroscopy. The adsorption performance of HPR1 was evaluated at various pH (2, 4, and 6.5) and initial Cr(vi) concentrations. The nonlinear Langmuir isotherm model provided the best fit for the experimental data compared with tc Freundlich and Redlich-Peterson isotherms. Notably, the adsorption equilibrium was achieved within 4 min, with a maximum capacity of 207 mg g-1 at pH 2. Kinetic studies indicated that the adsorption process was best described by a pseudo-second-order model, with higher rates observed at pH 4 than at pH 2. Additionally, intraparticle diffusion has been identified as the mechanism that controls the adsorption process. The high adsorption capacity of HPR1 at acidic pH values suggests its potential for treating industrial wastewater containing elevated concentrations of Cr(vi).

Multivariate analyses to evaluate the contamination, ecological risk, and source apportionment of heavy metals in the surface sediments of Xiang-Shan wetland, Taiwan

Nowadays, heavy metal (HM) contamination and their ecological risk in coastal sediments are global issues. This research provides insight into the heavy metals' contamination, source apportionment, and potential ecological risks in the surface sediments of the Xiang-Shan wetland in Taiwan, which is undergoing rapid economic development, mainly by the semiconductor industries. The levels of twelve metals and total organic matter (TOM) were measured in 44 samples of surface sediment during the spring and winter seasons of 2022. Subsequently, the single and comprehensive pollution indices were assessed. The findings showed that the average of HM contents exhibited a descending sequence of Al > Fe > Mn > Zn > Co > Ga > Cr > Cu > In > Ni > Pb = Cd during both seasons. The E f , I geo , and PI showed that the majority of sediment samples were uncontaminated to heavily contaminated by Fe, Al, Zn, Cu, Mn, Cr, Ni, Co and Ga, and extremely contaminated by In. Moreover, PLI and mC deg unveiled that the surface sediments of DJ, OB, and KY stations were strongly or extremely polluted. PERI revealed that the sediment shows minimal to moderate ecological risk. The findings of multivariate analyses suggested that Fe, Al, Cu, Zn, and Ni derived from natural sources, while Ga, In, Co, Cr, and Mn originated from both anthropogenic and natural origins. Hence, it is critical that HM contamination, particularly Co, In, and Ga, be continuously monitored in the study area. Our data provide significant insights for more effective prevention and evaluation of HM contamination in the aquatic-sedimentary ecosystems of Taiwan.

Probe-infused polymer monolithic sensor for colorimetric detection of Pb2+ in environmental water samples and tobacco extracts

This study focuses on developing an affordable and cost-effective colorimetric solid-state optical sensor for target-specific naked-eye detection of Pb2+, offering significant potential for real-time environmental monitoring and public health applications. The indigenously developed porous polymer monolithic template, poly(lauryl methacrylate-co-ethylene glycol dimethacrylate) (poly(LMC-co-EGDMA) is infused with a chromoionophoric probe, i.e., 6,6-(naphthalene-1,5-diyl bis(diazene-2,1-diyl)bis(4-(butan-2-yl)phenol) (NDBP) to develop a durable/reusable solid sensor. The perforated structural assemblies of the porous poly(LMC-co-EGDMA) are analyzed using a range of microscopic, spectroscopic, and diffraction methods. The template features a homogeneous configuration of interlinked macro/mesoporous networks, allowing for the enhanced integration of NDBP probe molecules to facilitate rapid and improved Pb2+ detection. The fabricated sensor demonstrates a significant solid-state colorimetric shift from pale peach to deep maroon in proportion to Pb2+ concentration, with a precise absorption peak at 543 nm. The operational parameters of the poly(LMC-co-EGDMA)NDBP sensor are optimized to maximize the ion-sensing ability. The sensor demonstrates a linear signal response from 0 to 300 ppb for Pb2+ and corresponding detection and quantification limits of 0.28 and 0.93 ppb, respectively. The sensing effectiveness of the sensor using cigarette samples and natural water samples reveals outstanding accuracy with recovery results of ≥ 98.9 % (RSD ≤1.8 %) and ≥ 99.1 %, with RSD of ≤ 1.7 % from quadruplicate analysis. The proposed solid-state sensor offers exceptional sensitivity and selectivity for trace Pb²⁺ detection with a rapid response time of 40 s. The cost-effective and portable sensor provides a valuable tool for environmental monitoring and public health protection by enabling fast, on-site detection of the toxic Pb2+ in contaminated water and tobacco samples, particularly for developing and underdeveloped regions with limited access to sophisticated instruments. Its reusability and accuracy features offer a sustainable and practical solution for addressing widespread lead pollution, thus contributing to safer water quality assessments and pollution control.

Adding Value into Elementary Sulfur for Sustainable Materials

Sulfur-rich copolymers, characterized by high sulfur contents and dynamic disulfide bonds, show significant promise as sustainable alternatives to conventional carbon-based plastics. Since the advent of inverse vulcanization in 2013, numerous synthesis strategies have emerged - ranging from thermopolymerization and photoinduced polymerization to the use of crosslinkers such as mercaptans, episulfides, benzoxazines, and cyclic disulfides. These advancements coupled with the rising demand for degradable plastics have driven research for diverse applications, including optical windows, metal uptake, and adhesives. Due to the unique electronic properties of sulfur-rich materials, they are promising candidates for cathodes in Li-S batteries and triboelectric nanogenerators. This review highlight the latest exciting ways of synthesis strategy in which sulfur and sulfur-based reactions are bing utilized to produce sustainable materials in energy, optics, engeneering material, environemtal, and triboelectric nanogenerators. Finally, this review provides a forward-looking perspective on the opportunities and challenges shaping this rapidly evolving field.

Advancing Ceramic Membrane Technology for Sustainable Treatment of Mining Discharge: Challenges and Future Directions

Mining discharge, namely acid mine drainage (AMD), is a significant environmental issue due to mining activities and site-specific factors. These pose challenges in choosing and executing suitable treatment procedures that are both sustainable and effective. Ceramic membranes, with their durability, long lifespan, and ease of maintenance, are increasingly used in industrial wastewater treatment due to their superior features. This review provides an overview of current remediation techniques for mining effluents, focusing on the use of ceramic membrane technology. It examines pressure-driven ceramic membrane systems like microfiltration, ultrafiltration, and nanofiltration, as well as the potential of vacuum membrane distillation for mine drainage treatment. Research on ceramic membranes in the mining sector is limited due to challenges such as complex effluent composition, low membrane packing density, and poor ion separation efficiency. To assess their effectiveness, this review also considers studies conducted on simulated water. Future research should focus on enhancing capital costs, developing more effective membrane configurations, modifying membrane outer layers, evaluating the long-term stability of the membrane performance, and exploring water recycling during mineral processing.

Geochemical processes and sensitivity analysis of flow velocity and column depth for effective nickel removal

Eliminating heavy metals from the environment is crucial, even in low concentrations, due to their high toxicity, persistence, and tendency to accumulate in living organisms, posing serious threats to human health and ecosystems. This study investigates the geochemical processes that govern nickel (Ni) removal in Filtralite and evaluates how different parameters influence its effectiveness. The interaction between contaminated water and Filtralite-forming minerals results in a rapid increase in pH, leading to the immediate precipitation of teophrastite (Ni(OH)2) at the initial filtration stages. However, as water continues to interact with Filtralite, its capacity to maintain high pH levels declines over time, reducing the Ni removal efficiently. In regions with a Mediterranean climate and considering an infiltration system that manages runoff from 10 % of the urban landscape, a filter layer of 200 mm combined with flow velocities below 828 mm/h has been found to optimize metal retention. Under these conditions, more than 90 % of the filter's total Ni-holding capacity is effectively used, and replacement is expected to be necessary roughly every three years. Additionally, tests simulating intense rainfall confirm that the eliminated Ni remains securely bound within the filter media, reinforcing Filtralite's reliability as a filtration material for infiltration systems. This research contributes to a better understanding of the geochemical mechanisms involved in metal removal and lays the groundwork for future design considerations in Filtralite-based filtration applications.

A Review on Advances in the Use of Raw and Modified Agricultural Lignocellulosic Residues in Mono- and Multicomponent Continuous Adsorption of Inorganic Pollutants for Upscaling Technologies

Using raw and modified lignocellulosic residues as bioadsorbents in continuous adsorption is challenging but it marks significant progress in water treatment and the transition to a bio-based circular economy. This study reviews the application of bioadsorbents in fixed-bed columns for treating water contaminated with inorganic species, offering guidance for future research. It evaluates chemical modifications to enhance adsorptive properties, explores adsorption mechanisms, and analyzes bioadsorbent performance under competitive adsorption conditions. Analysis of adsorption data included evaluation of adsorption capacity in mono- and multicomponent solutions, regeneration, reuse, bed efficiency, and disposal of spent bioadsorbents. This enabled assessing their scalability to sufficiently high levels of maturity for commercialization. In multicomponent solutions, selectivity was influenced by the characteristics of the bioadsorbents and by competitive adsorption among inorganic species. This affected adsorption performance, increasing the complexity of breakthrough curve modeling and controlling the biomaterial selectivity. Models for mono- and multicomponent systems are presented, including mass transfer equations and alternatives including "bell-type" equations for overshooting phenomena and innovative approaches using artificial neural networks and machine learning. The criteria discussed will assist in improving studies conducted from cradle (synthesis of new biomaterials) to grave (end use or disposal), contributing to accurate decision making for transferring the developed technology to an industrial scale and evaluating the technical and economic feasibility of bioadsorbents.

Cost-Effective Leachate Treatment and Resource Recovery in Hazardous Waste Landfills through Pipe Freeze Crystallization

This study aimed to develop a practical, economically viable solution for treating hazardous landfill leachate using Pipe Freeze Crystallization (PFC) technology. The objective was to concentrate and solidify leachate from an effluent treatment plant processing approximately 8750 m3 annually, achieving resource recovery and environmental compliance. A 300 L h-1 cooling demonstration plant was designed and implemented, incorporating a chiller, a secondary refrigerant mixture (40% ethylene glycol and 60% water), a clarifier, a reactor, and pumps. Μodelling with OLI software estimated recovery rates for salt and ice, providing a basis for operational adjustments. Leachate samples (2000 L) and concentrate (1000 L) were processed to evaluate the plant's performance in recovering clean water and Na2SO4. Experimental results confirmed the model predictions, with 302 L of concentrate yielding 102.9 kg of Na2SO4 over 6 h and 273 L of leachate producing 118.7 kg of high-purity ice over 5.5 h. The energy consumption was measured at 171 kWh t-1 of ice, aligning with theoretical predictions for a coefficient of performance of 1. These results validate the efficiency and feasibility of PFC in resource recovery. This study highlights the importance of PFC as a low-cost, energy-efficient technology for hazardous leachate treatment. Its scalability and ability to recover valuable resources such as Na2SO4 and clean water present a sustainable alternative to conventional methods, contributing to zero-waste management goals in waste treatment practices.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40710-025-00757-3.

Preparation and application of composite magnetic flocculants for wastewater treatment: A review

Wastewater treatment plays a vital role in protecting natural environments. Among the various wastewater treatment methods, flocculation achieves effective wastewater treatment, owing to its high efficiency, convenience, and cost-effectiveness. Compared to traditional flocculants, Composite magnetic flocculants have attracted significant attention due to their distinctive "core-shell" structure, magnetic flocculation mechanism and high efficiency recovery. This promotes sustainable development in wastewater treatment, highlighting the significant prospects for its application and potential advancement. This review begins by discussing the raw materials and treatment methods of composite magnetic flocculants and presenting common materials and associated preparation techniques. By combining the advantages of organic and inorganic components, disparate raw materials give flocculants different properties and flocculation efficiency. Through the comprehensive analysis of the flocculation mechanism, the flocculation efficiency of various wastewater treatment targets was elucidated, and the exceptional performance in overcoming steric hindrance was introduced. Subsequently, recycling approaches were summarized to determine the advantages and disadvantages in terms of recovery efficiency, operational difficulty, and impact on particle structure. Based on the current developmental status, this review provides a prospective outlook on future exploration trends in composite magnetic flocculants, valuable references, and theoretical foundations for related research and engineering practices.

A critical review of recent advancements in the photocatalysis process, mechanism, and degradation pathways for the removal of phthalates from the contaminated water matrix

Phthalates, a sort of plasticizer, are widely utilized in various consumer products and pose significant environmental and health risks due to their persistence and potential toxicity. This review explores the occurrence, sources, environmental impact, and remediation strategies for phthalates. Various remediation techniques have been investigated to address phthalate contamination. Among these, photocatalysis, an advanced oxidation process (AOP), has emerged as a viable approach due to its ability to mineralize organic contaminants into innocuous byproducts. The review discusses the recent advancements in photocatalytic processes, the underlying mechanisms, and degradation pathways for phthalate removal. The mechanism of photocatalytic degradation includes the generation of reactive oxygen species like hydroxyl radicals (OH•) and superoxide radicals (O2-•) and their role in breaking down phthalate molecules. It also highlights recent advancements in photocatalytic materials, such as metal-doped semiconductors and composite materials, which enhance the removal efficiency. The review concludes by emphasizing the need for integrated approaches to achieve effective and sustainable phthalate remediation. Future research should focus on developing efficient and cost-effective photocatalytic materials, optimizing reactor design, and scaling up photocatalytic processes for practical applications. The review also highlights the challenges and limitations of photocatalytic processes, including low quantum efficiency, catalyst deactivation, and mass transfer limitations. Potential areas of study are put forward to address these challenges and further advance the application of photocatalysis for phthalate removal. This review intends to help the development of efficient photocatalytic technologies for the remediation of phthalate-contaminated water by providing a complete overview of the present state of the art.

Study on the selective adsorption of Ag+ by thermosensitive poly(n-isopropylacrylamide)/guanylthiourea/chitosan composites

In this work, temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) and the ‌guanylthiourea (GLA) were used to modify chitosan (CS) to prepare a novel PNIPAM/GLA/CS adsorbent for Ag(I) ions. Temperature variations near the lower critical solution temperature (LCST) facilitate the adjustment of functional group distribution within the composite material, thereby influencing its adsorption performance for silver ions. The characteristics of this composite material were confirmed using a variety of techniques, including scanning electron microscopy (SEM), variable-temperature ultraviolet-visible near-infrared spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Studies on the adsorption of Ag(I) ions by the PNIPAM/GLA/CS adsorbent indicated that the optimal pH for adsorption is 6.0. The adsorption kinetics were best described by the pseudo-second order kinetic model, while the equilibrium adsorption data aligned more closely with the Langmuir adsorption isotherm model, achieving a maximum adsorption capacity of 336.33 mg/g at 40°C. Experimental results demonstrated that higher adsorption amounts were observed above the LCST, while desorption of target ions was more favorable below the LCST. This research provides valuable insights for the design of new structural adsorbents.

Advances in graphene-based nanomaterials for heavy metal removal from water: Mini review

The environment and public health are seriously at risk from the increasing levels of heavy metal (HM) pollution in water bodies, hence efficient remediation techniques must be developed. Unique physicochemical properties of graphene (Gn) such as its enormous surface area, chemical stability, and extraordinary adsorption capabilities have made it a promising candidate for application in various adsorption processes. Recent studies indicate the heavy metal removal capabilities of Gn-based materials such as Gn oxide (GO) and reduced GO (rGO) reach 99% efficiency rates for lead (Pb2+), cadmium (Cd2+), and mercury (Hg2+) through strong electrostatic bonds and metal coordination along with π-π stacking interactions. In addition, the selective nature of Gn-based adsorbents grows better through functionalization because it incorporates thiol, amine, and sulfonic acid groups. The integration of Gn-based materials with metal-organic frameworks (MOFs) combined with magnetic nanoparticles along with bio-based polymers enhances adsorption efficiency and increases stability while offering recyclability features. The conclusion of this study discusses the current obstacles such as cost, scalability, environmental impact, and selectivity and potential future developments for the widespread use of Gn-based adsorbents in water treatment, highlighting the significance of continued research to improve these substances for useful environmental applications. PRACTITIONER POINTS: Graphene-based materials exhibit high capacity for adsorbing various heavy metals, enhancing water purification. Functionalization of graphene improves its ability to selectively target and remove specific heavy metals like mercury and lead. Graphene derivatives can achieve heavy metal removal within minutes, making them efficient for water treatment. Despite high synthesis costs, graphene's superior performance may lower long-term operational costs in wastewater treatment.

Combined clinoptilolite and Fe(O)OH for efficient removal of Cu(II) and Pb(II) with enhanced solid-liquid separation

This study investigated combining fine clinoptilolite with iron hydroxide coagulant, as a cost-effective, dual-purpose flocculant for enhanced removal of Pb2⁺ or Cu2⁺ ions, along with the solid-liquid separation and physicochemical analysis. For the clinoptilolite, adsorption kinetics fitted a pseudo-second-order (PSO) rate model with higher rate constants for Pb2+, while equilibrium adsorption data fitted the Langmuir monolayer model, with Q max similar at 18.8 mg/g for Pb2+ and 18.3 mg/g Cu2+. TEM elemental mapping of the clinoptilolite evidenced areas of K and Fe impurities, while SEM suggested a uniform distribution of aggregates comprising a clinoptilolite core with decorated FeOOH. X-ray diffraction (XRD) indicated the FeOOH phase as α-FeOOH (Goethite) with no change in structure on inclusion of adsorbed Pb2+. Combined clinoptilolite-FeOOH flocs were significantly larger than FeOOH only precipitates, while flocs formed from 0.5 wt% FeOOH and 1 wt% clinoptilolite produced the fastest settling rates and greatest consolidation. Compressive yield stress data also correlated with enhanced dewatering of the combined systems, due to the dense clinoptilolite acting as a weighter material. For final metals removal, combined flocs outperformed FeOOH across a broad concentration range, achieving > 98% removal for both Pb2⁺ or Cu2⁺. The greater metals removal combined with denser floc production and improved settling features highlights significantly enhanced performance above that possible from either ion exchange or precipitation alone.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43938-025-00075-y.

Enhanced Removal of Cu2+ and Pb2+ Ions from Wastewater via a Hybrid Capacitive Deionization Platform with MnO2/N-Doped Mesoporous Carbon Nanocomposite Electrodes

Integrating MnO2 with carbon is a reliable strategy to improve capacitive deionization (CDI) performance by leveraging the unique properties of both components (i.e., MnO2 and carbon). However, the influences of preliminary functionalization of carbon (e.g., nitrogen doping, KOH activation) and pairing of cathodes and anodes on the CDI performance have yet to be systematically explored. Herein, we prepared a group of MnO2-decorated mesoporous carbon composites with nitrogen as a dopant (i.e., MK-NMCS, K-NMCS, NMCS, and CS), and systematically evaluated the desalination performance of various cathode//anode pairs in a hybrid capacitive deionization (HCDI) for capturing Na+, Cu2+, and Pb2+, respectively. Of all electrodes, the MK-NMCS//K-NMCS pair demonstrates the optimum desalination performance based on salt adsorption capacity (SAC) and cycling stability, offering a SAC of 25.4 mg g-1 and a SAC retention of 102.4% after 50 consecutive charge-discharge cycles at 1.2 V in 500 ppm of NaCl solution. In addition, the MK-NMCS//K-NMCS electrodes also show the maximum ion adsorption capacity (IAC) toward Cu2+ and Pb2+ ions compared to other cathode//anode pairs, attaining an IAC of 37.0 and 30.0 mg Cu2+ per gram electrode materials at 1.2 V in 500 and 200 ppm of Cu2+ solutions, respectively (cf. 32.2 mg of Pb2+ per gram of electrode materials in 200 ppm of Pb2+ solution). Besides, these electrodes exhibit excellent cycling stability when applied in removing each heavy metal ion separately, with IAC retentions of 90.0 and 98.5% after 50 cycles toward Cu2+ and Pb2+ ions, respectively. Mechanical analysis reveals that both heavy metals are likely to be sequestered via capacitive electrosorption by carbon, intercalation with MnO2, and surface complexation at the external surface of the [MnO6] octahedral layers. Our results demonstrated a great potential of the MnO2-decorated N-doped carbon//prefunctionalized carbon pairs, in particular, the MK-NMCS//K-NMCS electrode pair for capturing heavy metal ions via HCDI platforms. Such prefunctionalization and pairing strategies are very promising for screening high-performance composite electrodes for wastewater remediation.

Typical heavy metals in wastewater treatment plants in Nanjing, China: perspective of abundance, removal, and microbial response

Heavy metals (HMs) are hazardous contaminants with persistence and bioaccumulation, attracting widespread attention. Wastewater treatment plants (WWTPs) play vital roles in the pollution control of sewage, closely related to human health and the biological environment. Therefore, eight HMs in three typical WWTPs of Nanjing were determined in this study. The results revealed that Cr, Ni, Cu, and Zn were high-level HMs in all WWTPs. Notably, the highest contents of high-level HMs were found in electroplating WWTP (EWWTP) influent among three WWTPs, probably causing their higher removal (19.34-55.32%) during their primary treatment. In contrast, most HMs could be removed in the secondary treatment stage of municipal WWTP (MWWTP) and industrial WWTP (IWWTP) with the highest removal of As (72.00-85.81%). Analogously, nutrients were mainly removed during the secondary stage, with superior performance in MWWTP. A decrease in HMs removal was observed in the tertiary treatment of MWWTP and IWWTP compared to the secondary stage, while higher HMs removal (0.51-29.15%) was found in EWWTP except Hg. The highest content of HMs in sludge was Zn and Cr, which was more abundant in EWWTP than other WWTPs. The results of Illumina Miseq sequencing demonstrated the inhibition of microbial richness and diversity of EWWTP and IWWTP by industrial wastewater. Besides, alterations of microbial community structure and components were also observed owing to various influent sources. More similarity was found between EWWTP and MWWTP, in which the abundance of dominant genera, including Saccharimonadales (7.60-9.56%), Raineyella (5.06-7.38%), and Thauera (2.48-4.45%) was much higher than IWWTP.

Near-Native Imaging of Metal Ion-Initiated Cell State Transition

Metal ions are indispensable to life, as they can serve as essential enzyme cofactors to drive fundamental biochemical reactions, yet paradoxically, excess is highly toxic. Higher-order cells have evolved functionally distinct organelles that separate and coordinate sophisticated biochemical processes to maintain cellular homeostasis upon metal ion stimuli. Here, we uncover the remodeling of subcellular architecture and organellar interactome in yeast initiated by several metal ion stimulations, relying on near-native three-dimensional imaging, cryo-soft X-ray tomography. The three-dimensional architecture of intact yeast directly shows that iron or manganese triggers a hormesis-like effect that promotes cell proliferation. This process leads to the reorganization of organelles in the preparation for division, characterized by the polar distribution of mitochondria, an increased number of lipid droplets (LDs), volume shrinkage, and the formation of a hollow structure. Additionally, vesicle-like structures that detach from the vacuole are observed. Oppositely, cadmium or mercury causes stress-associated phenotypes, including mitochondrial fragmentation, LD swelling, and autophagosome formation. Notably, the organellar interactome, encompassing the interactions between mitochondria and LDs and those between the nuclear envelope and LDs, is quantified and exhibits alteration with multifaceted features in response to different metal ions. More importantly, the dynamics of organellar architecture render them more sensitive biomarkers than traditional approaches for assessing the cell state. Strikingly, yeast has a powerful depuration capacity to isolate and transform the overaccumulated cadmium in the vacuole, mitochondria, and cytoplasm as a high-value product, quantum dots. This work presents the possibility of discovering fundamental links between organellar morphological characteristics and the cell state.

Determination of Cd2+ and Pb2+ in seawater using a shipborne detection device

ABSTRACTA shipborne detection device has been developed for the detection of heavy metal ions in offshore seawater, utilizing a mercury film electrode. The automatic determination of Cd2⁺ and Pb2⁺ ions in seawater can be conducted without any manual intervention. Waste solutions are collected in a recycling bag for subsequent treatment, thereby preventing environmental pollution. The accuracy, as well as the stability of the measurements, were thoroughly examined. The relative standard deviation for Pb2⁺ was determined to be 7.02% after conducting 10 repeated tests using a standard solution concentration of 5 μg L⁻1 and the relative standard deviation of Cd2+ is 2.65%. Linear calibration curves have been established along with detection limits of 0.31 μg L⁻1 for both Cd2⁺ and Pb2⁺ ions. Ultimately, this shipborne detection device was successfully employed for the in-situ determination of Cd2⁺ and Pb2⁺ ions in seawater.

Efficient Removal of Co(II) Ions from Aqueous Solutions Using Polyampholyte Resin: Synthesis, Properties, and Performance

This paper presents the properties of a novel polyampholyte resin synthesized through the phosphinomethylation of diethylenetriamine. The resin, derived from inexpensive and safe building blocks, avoids the typical crude-oil resin matrix, such as poly(DVB), offering a notable advantage over commercially available solutions. Moreover, the synthesis process is straightforward and environmentally benign, aligning with the principles of sustainability and environmental protection. The primary objective of this study was to evaluate the efficiency of Co(II) ion removal from aqueous solutions using the synthesized resin under both static and kinetic conditions. Key parameters, including the initial metal ion concentration, pH, temperature, contact time, and resin dosage, were systematically investigated. A comprehensive mathematical analysis of static, kinetic, and thermodynamic parameters confirmed the effectiveness of the polyampholyte resin in removing Co(II) ions from aqueous solutions. Data analysis using the Langmuir isotherm model revealed a maximum sorption capacity of 191.7 mg/g at 328 K. Kinetic data were assessed using pseudo-first order, pseudo-second order, and Elovich kinetic models, while the Weber-Morris model was employed to determine the rate-controlling step in the Co(II) ion removal process. The results indicated that the removal of Co(II) ions follows a pseudo-second-order kinetic model, suggesting chemisorption as the dominant mechanism, with diffusion identified as the rate-controlling step according to the Weber-Morris model. Thermodynamic analysis demonstrated that the removal of Co(II) ions is spontaneous and endothermic (ΔH = 24.83 kJ/mol), with efficiency increasing at higher temperatures. Desorption studies using various reagents showed that 2 M H2SO4 achieved the maximum desorption of Co(II) ions (98%). The high ion removal efficiency and ease of regeneration make the synthesized resin a competitive alternative to currently available commercially adsorbents. Notably, the use of this novel polyampholyte resin represents a significant advancement in environmental protection (through reduced reliance on crude oil derivatives) and water treatment (via the removal of toxic ions).

Highly efficient removal of Pb2+ from aqueous solution using polyaniline-cobalt composite nanorods: Kinetics, isotherm and mechanistic investigation

Nanosized cobalt (Co) particles exhibit unique chemical, magnetic, electronic, and catalytic properties. Like nanoscale metallic iron, nanostructured Co and its composite nanostructures also show significant potential for the removal of toxic metal cations from water and wastewater. To explore this potential, composite nanorods (CNRs) of nanosized Co immobilized polyaniline (PANI) nanorods (NRs) matrix (PANI-Co CNRs) were synthesized and effectively applied for the treatment of lead ions (Pb2⁺), serving as a model for heavy metal pollutants in water bodies. Physico-chemical characterization of PANI-Co CNRs revealed that weak ferromagnetic Co nanoparticles (NPs) were effectively deposited onto the surface of the PANI NRs. The enhanced surface properties and superior reactivity of PANI-Co CNRs resulted in greater Pb2+ removal efficiency compared to their individual components. The adsorption kinetics were notably rapid, with the time required to reach equilibrium varying between 60 and 150 min for initial concentrations ranging from 50 to 150 mg/L, all at a pH of 5.0. The isotherm data revealed an impressive Pb2+ adsorption capacity of 1130 mg/g at 25 °C, as determined using the non-linear Langmuir model. Exothermic and spontaneous Pb2+ removal process was deduced from the thermodynamic investigations. Among co-contaminating metal ions, only Cu2+ ions significantly affected the Pb2+ removal performance of the PANI-Co CNRs, implying its possible applications in decontaminating industrial effluent laden with various metal ions. Mechanistic investigation revealed that the treatment process primarily involves the adsorption and precipitation of Pb2+ onto the surface of PANI-Co CNRs, followed by its subsequent reduction to form metallic Pb (Pb0).

Specific nickel recovery using screen-printed carbon electrode electrografted with ionic liquid

This study presents an innovative electrochemical method for selectively extracting nickel ions from aquatic solutions, employing electrodes enhanced with electrografted ionic liquids. Specifically, a styrenyl-imidazolium ionic liquid (SI-IL) was synthesized, featuring a double bond for immobilization and an imidazole group targeting nickel ions. The electrografting process ensured uniform SI-IL distribution on the electrode's surface, as confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). SI-IL-treated electrodes exhibited notable selectivity towards nickel ions, efficiently recovering them as nanoparticles while reducing the required reduction potential. In pH conditions similar to industrial wastewater, SI-IL modified electrodes demonstrated substantial enhancement in nickel recovery rates compared to unmodified electrodes.

Fluorometric Innovations for Ultrasensitive Trace Element Analysis in Environmental Matrices

Trace elements in environmental matrices and their potential harm to humans and the ecosystem are causing growing concern. For environmental monitoring and assessment, trace element analysis in water, soil, and air must be precise. Due to its selectivity and sensitivity, fluorometric analysis has grown in popularity. This review covers the latest fluorometric approaches for trace element measurement in environmental samples. This review discusses sensitive and selective fluorometric probes. A significant increase in fluorescence intensity makes this probe better for trace element research. Various parameters like pH, temperature, and reaction time were carefully optimized in each approach to increase sensitivity and accuracy. The current study sheds light on this analytical approach's concepts, applications, and difficulties. In general, fluorometric analysis is important for environmental studies. For researchers, it allows them to use fluorometric technology with other methods and focus on real-time analysis to solve environmental challenges.

Highly selective and reusable nanoadsorbent based on Fe3O4-embedded sodium alginate-based hydrogel for cationic dye adsorption: Adsorption interpretation using multiscale modeling

This study aims to develop a stable and efficient magnetic nanocomposite hydrogel (MNCH) for selective removal of methylene blue (MB) and crystal violet (CV). MNCHs with different Fe3O4 contents (0-9 wt%) were synthesized following graft co-polymerization method using sodium alginate, acrylamide, itaconic acid, ammonium persulfate and N,N-methylene bisacrylamide. Among them, MNCH5, with 5 wt% Fe3O4, showed highest removal efficiency (>95 %). Optimal dye removal occurred at pH 10, with 40 min for CV and 60 min for MB using 30 mg dose. MNCH was characterized using various techniques, with X-ray diffraction (XRD) revealing crystallite size of 30.5 nm, and Brunauer-Emmett-Teller (BET) indicating surface area of 59.80 m2 g-1. Adsorption kinetics followed fractal pseudo-first-order and fractal Vermeulen diffusion models, reflecting MNCH's heterogeneous nature as suggested by fractal exponent (h) ranging 0.38-0.44, significantly deviating from zero. Langmuir-Freundlich isotherm accurately described the process, demonstrating MNCH's superior affinity for MB (4216.69 mg g-1) over CV (3730.17 mg g-1). Thermodynamics of MB adsorption was exothermic as suggested by negative ΔH value, while CV adsorption was endothermic. Density functional theory confirmed stronger interaction between MNCH and MB (Eads = -49.29 kcal mol-1) compared to CV (Eads = -41.30 kcal mol-1). These findings underscore MNCH's excellent adsorption capacity, making it promising for removing dyes.

MXene-based materials for enhanced water quality: Advances in remediation strategies

Two-dimensional MXenes are promising candidates for water treatment because of their large surface area (e.g., exceeding 1000 m²/g for certain structures), high electrical conductivity (e.g., >1000 S/m), hydrophilicity, and chemical stability. Their strong sorption selectivity and effective reduction capacity, exemplified by heavy metal adsorption efficiencies exceeding 95 % in several studies, coupled with facile surface modification, make them suitable for removing diverse contaminants. Applications include the removal of heavy metals (e.g., achieving >90 % removal of Pb(II)), dye removal (e.g., demonstrating >80 % removal of methylene blue), and radioactive waste elimination. Furthermore, 3D MXene architecture exhibit enhanced performance in antibacterial activities (e.g., against bacteria), desalination rejection percentage, and photocatalytic degradation of organic contaminants. However, several challenges have remained, which necessitate further investigation into toxicity (e.g., assessing effects on aquatic organisms), scalability, and cost-effectiveness of large-scale production. This review summarizes recent advancements in 3D MXene-based functional materials for wastewater treatment and water remediation, critically analyzing their both potential and limitations.

Optical Chemosensors Synthesis and Appplication for Trace Level Metal Ions Detection in Aqueous Media: A Review

In recent years, the development of optical chemosensors for the sensitive and selective detection of trace level metal ions in aqueous media has garnered significant attention within the scientific community. This review article provides a comprehensive overview of the synthesis strategies and applications of optical chemosensors dedicated to the detection of metal ions at low concentrations in water-based environments. The discussion encompasses a wide range of metal ions, including but not limited to heavy metals, transition metals, and rare earth elements, emphasizing their significance in environmental monitoring, industrial processes, and biological systems. The review explores into the synthesis methodologies employed for designing optical chemosensors, discovering diverse materials like organic dyes, nanoparticles, polymers, and hybrid materials. Special attention is given to the design principles that enable the selective recognition of specific metal ions, highlighting the role of ligand chemistry, coordination interactions, and structural modifications. Furthermore, the article thoroughly surveys the analytical performance of optical chemosensors in terms of sensitivity, selectivity, response time, and detection limits. Real-world applications, including water quality assessment, environmental monitoring, and biomedical diagnostics, are extensively covered to underscore the practical relevance of these sensing platforms. Additionally, the review sheds light on emerging trends, challenges, and future prospects in the field, providing insights into potential advancements and innovations. By synthesizing the current state of knowledge on optical chemosensors for trace level metal ions detection. The collective information presented herein not only offers a comprehensive understanding of the existing technologies but also inspires future research endeavors to address the evolving demands in the realm of trace metal ion detection.

Covalent Organic Frameworks and 2D Materials Hybrids: Synthesis Strategies, Properties Enhancements, and Future Directions

Covalent organic frameworks (COFs) are highly porous, thermally and chemically stable organic polymers. Their high porosity, crystallinity, and adjustable properties make them suitable for numerous applications. However, COFs encounter critical challenges, such as their difficult processability, self-stacking propensity, low electrical conductivity, pore blockage which limits their ionic conductivity, and high recombination rates of photoinduced electrons and holes. To overcome these issues, the hybridization of COFs with 2D materials (2DMs) has proven to be an effective strategy. 2DMs including graphene-like materials, transition metal dichalcogenides, and MXenes are particularly advantageous because of their unique physicochemical properties, such as exceptional electrical and optical characteristics, and mechanical resilience. Over the past decade, significant research efforts have been focused on hybrid 2DMs-COFs materials. These hybrids leverage the strengths of both materials, making them suitable for advanced applications. This Review highlights the latest advancements in 2DM-COF hybrids, examining the physicochemical strengths and weaknesses of the pristine materials, together with the synergistic benefits of their hybridization. Moreover, it emphasizes their most remarkable applications in chemical sensing, catalysis, energy storage, adsorption and filtration, and as anticorrosion agents. Finally, it discusses future challenges and opportunities in the development of 2DM-COFs for new disruptive technologies.

Culture-Dependent and -Independent Wastewater Surveillance for Multiple Pathogenic Yeasts

Wastewater surveillance is a promising tool to monitor potential outbreaks and determine the disease burden within a community. This system has been extensively used to monitor polio and COVID-19 infection levels, yet few attempts have been made to apply it to monitoring pathogenic yeast. This study aimed to investigate the application of wastewater surveillance for potentially pathogenic yeast in wastewater treatment plant influent. This was done by comparing culture-dependent data with culture-independent data and investigating the fluconazole concentration in wastewater. Additional studies on the growth of isolated strains were conducted. We found that a multiplex PCR system to detect multiple yeasts holds promise as a molecular detection tool for wastewater surveillance. Culture-dependent results indicated that Candida spp. specifically C. krusei and C. glabrata, were most prominent. Growth studies supported that these species grow well in this environment while the less frequently isolated yeasts grew poorly. The data from culture-dependent and independent techniques showed some correlation, with similar species being identified with both, further promoting the use of molecular tools for surveillance. This study highlights the presence of potentially pathogenic yeasts in wastewater, which may indicate the prevalence of these yeasts in the environment or community. This wastewater may also be a potential source of infection for persons encountering it due to poor wastewater management.

Imidazolium-Functionalized Ionic Porous Organic Polymer for Efficient Removal of Oxo-Anions Pollutants from Water

The development of highly efficacious materials for the removal of toxic heavy metal-based oxo-anions is of utmost importance. Herein, an ionic porous organic polymer (designated as HB-IPOP) was synthesized through a quaternization reaction between hexa(imidazole-1-yl)benzene and 5,5'-Bis(bromomethyl)-2,2'-bipyridine. HB-IPOP exhibited high saturation uptake capacities, specifically 292 mg·g-1 for Cr2O72- and 531 mg·g-1 for ReO4-, and demonstrated exceptional selectivity for both Cr2O72- and ReO4-. Additionally, HB-IPOP demonstrates high recyclability, allowing its reuse over at least five cycles. DFT calculations confirmed that the superior interaction sites and binding energies of HB-IPOP with Cr2O72- and ReO4- outperform the affinities of other competing anions. This theoretical validation aligns with the experimentally observed high capacity and selectivity of HB-IPOP for these oxo-anions. Hence, HB-IPOP emerges as a promising candidate to replace current adsorbent materials in the effective removal of Cr2O72- and TcO4- anions from water.

Relationship Between Electronegativity of the Extra-Framework Cations and Adsorption Capacity for CO2 Gas on Mordenite Framework

Synthetic mordenite is widely used as a molecular sieve, adsorbent, and catalyst. To enhance these functionalities, it is crucial to understand the ion-exchange properties and cation-exchange sites of the zeolite. In this study, we analyzed the structural changes in fully Cs-, Sr-, Cd-, and Pb-exchanged mordenite by using synchrotron X-ray powder diffraction under ambient conditions. Rietveld structure refinement revealed that the Cs+ cation is predominantly located near the 8-membered ring (8MR) due to its low electronegativity and hydration energy. In contrast, divalent cations such as Sr2+ and Cd2+ cations, with higher hydration energies compared to monovalent cations, are present as hydrated ions at the center of the 12-membered ring along the c-axis (12MRc). Pb2+ ions, due to their higher electronegativity than the framework atoms, exhibit a strong affinity for the electron cloud of framework oxygen atoms, which positions them close to the wall of the 12MRc. The observed differences in the locations of the extra-framework cations are attributed to electrostatic and hydration effects. Furthermore, the CO2 adsorption capacity was assessed based on the type and site of exchangeable cations. The findings indicate that an increase in the CO2 adsorption capacity correlates with the number of cations that can effectively interact with CO2.

Nano-Fibrillated Bacterial Cellulose Nanofiber Surface Modification with EDTA for the Effective Removal of Heavy Metal Ions in Aqueous Solutions

Nano-fibrillated bacterial cellulose (NFBC) has very long fibers (>17 μm) with diameters of approximately 20 nm. Hence, they have a very high aspect ratio and surface area. The high specific surface area of NFBC can potentially be utilized as an adsorbent. However, NFBC has no functional groups that can bind metal ions, limiting its potential applications. In this study, the hydroxyl groups on the surface of NFBC were chemically modified with EDTA monoanhydride to convert NFBC into a metal adsorbent. The fiber morphology and crystal structures of the modified NFBC were almost identical to those of the unmodified NFBC, suggesting that the surface hydroxyl groups of NFBC were well-conjugated with the EDTA groups. Surface-modified NFBC preferentially adsorbed transition metals in aqueous solutions, such as Cu(II), Hg(II), Pb(II), and Cd(II), but hardly adsorbed Mg(II) and Cr(VI). The adsorption of heavy metal ions can be explained by the pseudo-second-order kinetics of the chemisorption process and the Langmuir isotherm model. Furthermore, the EDTA-modified NFBC is a renewable and recyclable adsorbent. The results of this study indicate that surface-modified NFBC can be utilized as a biosorbent for heavy metal removal in chemical, food, pharmaceutical, and other industrial fields.

Efficient recovery of valuable metals from electroplating sludge smelting soot via a combined alkali roasting and acid-free aluminum salts leaching methods

Electroplating sludge smelting soot (ESSS), contains high-grade value metals (such as Zn, Sn, Pb, precious metals Au and Pt) and large amounts of harmful elements Br and S, which could potentially cause valuable resources wastage and environmental pollution, therefore requires responsible recycling. An efficient and eco-friendly process for the cascade recovery of Zn, Sn, Pb, and precious metals Au and Pt from ESSS was proposed, combining NaOH roasting and acid-free aluminum salts leaching. Optimal NaOH roasting conditions achieved high extraction efficiencies for Zn, Sn, and Pb, which were then separated via water leaching. A novel Al(NO3)3 + AlCl3 leaching system was developed to recover Au and Pt from the enriched residue. By optimizing the NaOH roasting conditions and the Al(NO3)3 + AlCl3 leaching conditions, the decomposition and conversion of 99.91 % Zn, 99.56 % Sn, and 98.72 % Pb in ESSS were achieved, simultaneously accomplishing the leaching of 87.89 % Au and 100 % Pt. Mechanisms of NaOH roasting and Al(NO3)3 + AlCl3 leaching were elucidated using XRD, SEM, ICP, XRF, and DFT calculations. Leaching kinetics of Au and Pt were also studied. Finally, Au and Pt were efficiently recovered from the leaching solution by lead powder replacement. This study provides a feasible and promising solution for the green and efficient recovery of valuable metals from ESSS.

Zirconium-based nanoclusters as molecular robots for water decontamination

Water contamination owing to anionic pollutants is a persisting and ubiquitous global threat. The current remediation technologies are mostly low in efficiency, expensive in materials and often associated with complicated processes. Herein, we report a characteristic zirconium-based nanocluster that can work as molecular robots for the efficient remediation of anions-contaminated water with great effectiveness and molecular-level accuracy. It exhibits a stimuli-responsive behavior to facilitate the water treatment process: dissolve in acidic aqueous solutions for molecular-level decontamination and quickly aggregate for post-remediation collection. It can precisely capture the representative anionic pollutants, whilst featuring satisfactory capacities (ca. 175 mg-arsenic/g, 60 mg-chromium/g, 45 mg-fluoride/g, 70 mg-phosphorus/g, respectively), super-fast kinetics (finishing uptake within seconds, which is two to four orders of magnitude faster than typical sorbents), as well as multi-cycle applications without appreciable loss of activity. The coexisting common ions show no effect on the target uptake. The responsible active site investigation shows that four active sites are responsible for the monovalent pollutant removal, and the active sites work in pairs to capture divalent chromate species. Cost analysis shows its economical applicability in practical applications. This work would lead to the development of effective water decontamination with higher effectiveness, more convenience, lower cost and more practical application value.

Jute-Copper Nanocomposite Embedded PSf Membrane for Sustainable and Efficient Heavy Metal Removal from Water Sources

Numerous corporations have overlooked environmental regulations concerning wastewater treatment, leading to a worldwide issue regarding hazardous pollutant discharge, particularly dyes and heavy metal ions, into river sources. Various industries, with water, energy, and biological sectors, actively employ membranes. Membranes capable of showing flux, metal and dye sorption, and catalysis have been developed and are extensively used by functionalizing the pores of ultrafiltration, microfiltration, and nanofiltration membranes with responsive properties. The enhancement of synthetic membrane performance can be achieved by developing new polymers or modifying the surface of existing polymers. In this study, high porosity and large internal pore volume polysulfone (PSf) membrane composites were produced on a laboratory scale by adjusting the polymer coagulation conditions during the phase inversion process, incorporating copper nanoparticles for antifouling properties, and utilizing pretreated natural jute fibers. A comprehensive characterization of the composites was conducted by using FTIR, XRD, XPS, ICP-MS, and SEM techniques. To calculate their possible uses in separation and purification methods, the performance of PSf-based membrane composites was evaluated in terms of heavy metal rejection rates (%) in water.

Effective removal of heavy metal ions (Pb, Cu, and Cd) from contaminated water by limestone mine wastes

Limestone mining waste and its derived CaO were checked as an adsorbents of pb2+, Cu2+, and Cd2+ ions from water solution. The characterization of Limestone and calcined limestone was studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), and Surface area measurements (BET). The optimum conditions of sorbent dosage, pH, initial concentration, and contact time factors were investigated for pristine limestone and calcined limestone absorbents. The results indicate that the optimum initial concentrations of (Ci) were 1200, 500, and 300 ppm for Pb, Cu, and Cd, respectively, using calcined limestone adsorbent, while using the pristine limestone adsorbent, the corresponding optimum initial concentrations were 700, 110, and 50 ppm. In the ternary system sorption, the results indicated that the selectivity sequence of the studied metals by limestone can be expressed as Pb2+ > Cd2+ > Cu2+, while calcined limestone exhibits a higher selectivity for Pb2+ compared to Cu2+ and Cd2+. Hence, various adsorption isotherm and kinetic models were examined to explore different patterns and behaviors of adsorption. So, the results indicate that calcined limestone has great potential for eliminating cationic heavy metal species from industrial water solutions.

Effective removal of Pb from industrial wastewater: A new approach to remove Pb from wastewater based on engineered yeast

The use of synthetic biology to construct engineered strains has provided new perspectives for addressing Pb contamination; however, the large-scale treatment of contaminants is still limited by high operating costs and technological constraints. This study introduces a novel technique for applying engineered yeast in the removal of heavy metals, offering a solution to the cost and process scale challenges associated with utilizing engineered yeast. Hydrogen sulfide-producing engineered yeast strains were constructed based on existing strategies by knocking out the gene encoding the O-acetyl-L-homoserine mercapturic enzyme, which plays a role in sulfate assimilation. To facilitate the transition of engineered yeast from laboratory settings to industrial applications while reducing operating costs and addressing process scale-up issues, we proposes a new operational technology for engineered yeast based on their mechanistic understanding and a response surface optimization approach. The development and application of low-cost engineered media provide important guidance for utilizing engineered yeast to tackle Pb-contaminated wastewater and for the production of PbS crystalline nanomaterials. The industrial culture system was designed using economical materials and, through the response surface methodology, achieved removal rates of 99.02 ± 0.06 % and 80.95 ± 9.68 % of Pb²⁺ from Pb acid electrolyte and industrial Pb wastewater, respectively. This study presents a new technological solution for cost control and process scale-up based on the bioregulatory mechanisms of engineered yeast, laying the groundwork for their industrial application. Furthermore, it offers essential parameters and theoretical support for the industrial applications of engineered yeast in Pb wastewater treatment.

Molecular dynamics simulations reveal efficient heavy metal ion removal by two-dimensional Cu-THQ metal-organic framework membrane

Two-dimensional (2D) metal-organic frameworks (MOFs) have been extensively utilized across various research areas. However, the application of 2D MOF-based membranes for the removal of heavy metal ions remains largely unexplored, despite their potential as suitable candidates due to their inherent porosity. In this study, we employed molecular dynamics (MD) simulations to investigate the capacity of a typical 2D MOF, Cu-THQ, for the separation of heavy metal ions, including Cd²⁺, Cu²⁺, Hg²⁺, and Pb²⁺. Our MD results demonstrate that single-layered Cu-THQ MOF membranes exhibit excellent performance in heavy metal ion removal, with nearly 100% ion rejection while also allowing high water permeability. Free energy calculations confirm that water transport through the Cu-THQ membrane is energetically more favorable compared to the transport of heavy metal ions. Further simulations of multilayered Cu-THQ membranes indicate that increasing the number of Cu-THQ MOF layers hinders water molecule transport, resulting in a reduction in water permeability due to a more widespread adsorption, that is primarily driven by electrostatic interactions within the membrane pores. Therefore, our simulations not only identify a promising MOF membrane candidate for efficient heavy metal ion removal but also suggest an optimal MOF construction scheme, which provide beneficial information for future applications in the sieving field.

Mercury (II) adsorption process from an aqueous solution through activated carbon blended with fresh pistachio green shell powder

In this research, fresh pistachio green shell as an agricultural waste was blended with activated carbon to study the adsorption process of mercury (II) from several aqueous solutions with various concentrations. Central Composite Design under Response Surface Methodology was statistically used to consider the independent variables involving pH, contact time, fresh pistachio green shell powder dosage, initial concentration of mercury (II) and activated carbon dosage effects on the mercury (II) removal. pH of 6.13, initial mercury (II) concentration of 36.68 g/l, fresh pistachio shell powder dosage of 9.21 g/l, activated carbon dosage of 7.25 g/l as an optimal operating conditions for 99.25% of mercury (II) removal was experimentally found. The adsorption kinetic models such as the pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion were examined. The pseudo-second-order model (with R2 ≈ 1) could properly investigate the adsorption process kinetics. The adsorption isothermal behavior was considered using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. Langmuir isotherm model showed the best results demonstrating the blended adsorbent homogeneous surface. The activation energy for the adsorption process was obtained at 2.158 kJ/mol. Several morphological tests (such as SEM, XRD, FTIR and EDX) were done to investigate the porosity and surface area of adsorbent although interaction of surface functional groups and synergistic effects can also be considered by these tests. The fresh pistachio green shell powder blended with activated carbon could physically adsorb (physisorption process) mercury (II) from an aqueous wastewater.

Electro-bioremediation of wastewater: Transitioning the focus on pure cultures to elucidate the missing mechanistic insights upon electro-assisted biodegradation of exemplary pollutants

Electro-bioremediation of exemplary water pollutants such as nitrogenous, phosphorous, and sulphurous compounds, hydrocarbons, metals and azo dyes has already been studied at a macro-scale level using mixed cultures. The technology has been generally established as a proof of concept at the technology readiness level (TRL) of 3, and there are already specific cases where the technology reached TRL 5. However, this technology is less utilized compared to traditional approaches. Although, mixed cultures result in high electro-biodegradation efficiency, their use hinders process' mechanistic insights which are better determined through pure cultures studies. This knowledge can lead to improved technologies. Therefore, this manuscript focuses on the specific pollutants' electro-biodegradation by pure cultures, assessing the availability of information regarding genes, enzymes, proteins and metabolites involved. Furthermore, studies characterizing the dominant genera or species are assessed, in which the available information at molecular level is evaluated. In total, less than 40 studies were found which were predominantly focused on the electro-biodegradation potential rather than the mechanistic insights. This highlights a gap in the field featuring a motivation to transitioning the focus on the study of pure cultures to unravel the mechanistic insights. Therefore, specific actions are suggested. Characterization of the mixed cultures followed by microorganisms' isolation is crucial. Thus, electroactive and biodegradation characteristics will be revealed using omics, genome annotation and transcriptional kinetics. This can lead to optimization at the microbiological level through genetic engineering, synthetic biology, mathematical modelling and strategic building of co-cultures. This research focus offers new avenues for sustainable wastewater treatment.

Enhanced Cd2+ removal from aqueous solution using olivine and magnesite combination: New insights into the mechanochemical synergistic effect

In this study, an efficient stabilizer material for cadmium (Cd2+) treatment was successfully prepared by simply co-milling olivine with magnesite. Several analytical methods including XRD, TEM, SEM and FTIR, combined with theoretical calculations (DFT), were used to investigate mechanochemical interfacial reaction between two minerals, and the reaction mechanism of Cd removal, with ion exchange between Cd2+ and Mg2+ as the main pathway. A fixation capacity of Cd2+ as high as 270.61 mg/g, much higher than that of the pristine minerals and even the individual/physical mixture of milled olivine and magnesite, has been obtained at optimized conditions, with a neutral pH value of the solution after treatment to allow its direct discharge. The as-proposed Mg-based stabilizer with various advantages such as cost benefits, green feature etc., will boosts the utilization efficiency of natural minerals over the elaborately prepared adsorbents.

Efficient removal of uranium (VI) from environmental water samples by cyclodextrin-intercalated layered double hydroxide-coated magnetic nanoparticles

This manuscript describes the successful synthesis of Fe3O4 nanoparticles coated with β-cyclodextrin-intercalated layered double hydroxide, which were utilized to remove Uranium (VI) from an aqueous solution effectively. The newly developed nano-adsorbent underwent thorough analysis through advanced techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), and energy-dispersive X-ray analysis (EDX). Through the utilization of a one-variable-at-a-time strategy, we effectively enhanced the removal process by optimizing key factors such as the sample's pH and the amount of adsorbent utilized. These adjustments proved crucial in achieving utmost success. The adsorption mechanism was identified by plotting Langmuir and Freundlich isotherms. Under the optimized conditions, the removal efficiency of as high as 96.21%, as well as the adsorption capacity of 461.89 mg g- 1, were obtained showing the desirable performance of the synthesized nano-adsorbent in Uranium (VI) removal from aqueous solutions. The selectivity of the adsorbent was evaluated by calculating distribution coefficients for Uranium (VI) and some interfering ions. The applicability of the adsorbent was tested by removing uranium (VI) from diverse complex environmental water samples. As a result of the removal efficiencies exceeding 92.76% with relative standard deviations (RSDs%) below 6.73%, the synthesized adsorbent can successfully remove Uranium (VI) from complex real samples with acceptable precisions.

Minimum-Run Resolution IV Design for Optimized Bio Removal of Fe2+ Using Enteromorpha intestinalis Aqueous Extract and Its Extract-Coated Silver Nanoparticles

Biosorbents have demonstrated considerable potential for the remediation of metals in aqueous environments. An aqueous extract of Enteromorpha intestinalis L. (EiE) and its extract-coated silver nanoparticles have been prepared and employed for the removal of iron. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV-visible spectroscopy, transmission electron microscopy (TEM), gas chromatography-mass spectroscopy (GC-MS), and zeta potential were employed to characterize the prepared biosorbents. The adsorption properties of the biosorbents were investigated in batch experiments, with a range of factors taken into account, including pH, contact time, initial ion concentrations, biosorbent dosage, and temperature. A minimum-run resolution IV design (MRR-IV) was developed with the objective of optimizing the removal efficiency. The mechanisms of adsorption were investigated using both the Langmuir and Freundlich isotherms. Kinetic studies were conducted using the pseudo-first-order and pseudo-second-order models. A variety of active constituents, including organic acids, lipids, alcohols, and terpenes, were identified through the use of GC-MS, with the findings supported by FTIR spectra. Transmission electron microscopy (TEM) revealed that the nanoparticle size ranged from 5 to 44 nm, while X-ray diffraction (XRD) demonstrated a high degree of crystallinity. A screening study employing the MRR-IV methodology, facilitated by the Design-Experiment, Ver 13., indicates that three factors exert a considerable influence on the biosorption process. The study demonstrated that the biosorption mechanism is pH-dependent, with an optimal pH of 5. The adsorption performance was found to follow Freundlich isothermal models and pseudo-first-order kinetics.

Engineered biochar for in-situ and ex-situ remediation of contaminants from soil and water

Tailoring physical and chemical properties of biochar enhances its selectivity, treatability, and efficiency in contaminant remediation. Thus, engineered biochar has emerged as a promising remedy for both in-situ and ex-situ remediation of polluted soil and water. Several factors influence the effectiveness of engineered biochar, including feedstock sources, pyrolysis conditions, surface functionalization, mode of application, and site characteristics. The advantages and disadvantages of different modification approaches to engineered biochar and their specific treatability for in-situ and ex-situ remediation are obscure and must be adequately addressed. This review critically evaluates the application of engineered biochar for on/off-spot contamination management, taking into account the long-term stability and biocompatibility prospects. The properties of engineered biochar resulting from modification with clay minerals, nanoparticles, polymers, surfactants, and oxidants/reductants were critically reviewed. Recent progress and advances in remediation mechanisms and modes of application were elaborated for the effective removal of organic and inorganic contaminants, including heavy metals, pesticides, dyes, polycyclic aromatic hydrocarbons, per- and poly-fluoroalkyl substances, and agrochemicals. Several crucial parameters influence in-situ remediation, including the distribution of contaminants, background electrolytes, hydraulic conductivity, as well as dispersion and stability of adsorbents. Ex-situ remediation of pollutants relies heavily on adsorption or degradation kinetics, background electrolytes, adsorbent dose, and pollutant concentrations. In addition, factors restricting the application of engineered biochar were highlighted for long-term sustainable contaminant management and maintaining low environmental impact. Finally, the challenges and future perspectives of utilizing engineered biochar for field-scale demonstration of contaminated sites are proposed.