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Mercury, a highly toxic metal and pollutant, poses a significant risk to human health and the environment. This study describes the synthesis of a new nitrogen-doped heteroaromatic hyper-crosslinked polyamine (HCPA) via the polycondensation of 2,6-diaminopyrazine and tris(4-formylphenyl)amine for the efficient removal of mercury ions from aqueous solutions. The HCPA polymer was characterized by solid-state 13C-NMR and FT-IR spectroscopy. A powder X-ray diffraction and thermogravimetric analysis showed that the polymer was semicrystalline in nature and stable up to 500 °C. Adsorption isotherms indicated that mercury adsorption occurred via mono- and multilayer adsorption by HCPA, as depicted by the Langmuir, Freundlich, and Redlich–Peterson isotherm models, with a maximum adsorption capacity of qm = 333.3 mg/g. Adsorption kinetic models suggested that the adsorption process was fast and effective, reaching equilibrium within 20 min. Thermodynamics of the adsorption process revealed that it was endothermic and spontaneous in nature due to the positive ΔH0 of 48 kJ/mol and negative ΔG0 values of −4.5 kJ/mol at 293 K. Wastewater treatment revealed 98% removal of mercury indicating the selective nature of HCPA. Finally, HCPA exhibited excellent performance and regeneration up to three cycles, demonstrating its great potential as an adsorbent for environmental remediation applications. [ABSTRACT FROM AUTHOR]

The study proposed the use of aspen wood sawdust and biochar derived from this sawdust for the removal of Pb(II), Cd(II), and Cr(VI) ions from soil in systems containing single metals as well as a mixture of all the studied metals. The effectiveness of the applied sorbents was compared with the sorptive properties of activated carbon. The results showed that all the tested materials reduced the metal content in the soil, and the obtained biochar was able to sorb lead, cadmium, and chromium ions in both studied systems. The influence of the type of sorbent, its dose, process duration, and the impact of metal on the removal efficiency and sorption capacity was analyzed. A statistical analysis of the obtained results was also conducted, determining the influence of process parameters on the removal capabilities of metal ions. The highest Pb, Cd and Cr ion removal efficiencies were obtained in a 36-day process at a sorbent dose of 10%. Aspen sawdust, biochar and activated carbon removed 46%, 50% and 71% of Pb(II), 35%, 43% and 53% of Cd(II) and 15%, 27% and 38% of Cr(VI), respectively. In turn, the highest sorption capacity values were achieved in a 36-day process at a sorbent dose of 2%, obtaining results of 20.2 mg/g, 22.3 mg/g and 23.2 mg/g of Pb(II), 5.1 mg/g, 7.9 mg/g and 11.7 mg/g of Cd(II) and 3.8 mg/g, 5.8 mg/g and 8.5 mg/g of Cr(VI), respectively. It was found that both raw aspen wood sawdust and biochar derived from this wood are effective in removing toxic metal ions from soil, which presents a potential solution to their presence in the natural environment. [ABSTRACT FROM AUTHOR]

The energy sector is the sector that generates the highest amount of environmental contamination, especially in water sources, mostly in the case of coal-based energy production. The aim of this study was to examine a significant contamination source, heavy metal contamination, in coal mining effluents. The current investigation introduces an MOF platform based on zirconium clusters and isophthalic acid with NH2-MIP-SO3H mixed amine and sulfonic acid functional groups in order to remove the most common heavy metal ions in coal mining effluents, including Hg, Cd, Pb, and Cu ions. The water matrix and the operational conditions were identified to be very influential in the removal process, such as the pH of water, the initial metal concentration and operating time. NH2-MIP-SO3H offers a great removal efficiency of metals starting from 745.83 mg/g for Cd, 673.67 mg/g for Cu, 589.85 mg/g for Hg, and 481.66 mg/g for Pb ions, with the Langmuir equation for equilibrium and pseudo-second-order equation for kinetics being the ideal models to express the equilibrium and kinetic data, respectively. A significant impact of water pH was found to occur, with the NH2-MIP-SO3H platform performing best at pH 6. Reuse of NH2-MIP-SO3H demonstrates excellent reusability, sustaining 90% of initial performance over eight regeneration cycles. The interaction of functional group-functional metal was the dominant mechanism in the removal process. The NH2-MIP-SO3H unique approach to heavy metal removal provides a very hopeful outlook for additional investigations in larger-scale studies. [ABSTRACT FROM AUTHOR]

Biochar is crucial for agricultural output and plays a significant role in effectively eliminating heavy metals (HMs) from the soil, which is essential for maintaining a soil–plant environment. This work aimed to assess machine learning models to analyze the impact of soil parameters on the transformation of HMs in biochar–soil–plant environments, considering the intricate non-linear relationships involved. A total of 211 datasets from pot or field experiments were evaluated. Fourteen factors were taken into account to assess the efficiency and bioavailability of HM–biochar amendment immobilization. Four predictive models, namely linear regression (LR), partial least squares (PLS), support vector regression (SVR), and random forest (RF), were compared to predict the immobilization efficiency of biochar-HM. The findings revealed that the RF model was created using 5-fold cross-validation, which exhibited a more reliable prediction performance. The results indicated that soil features accounted for 79.7% of the absorption of HM by crops, followed by biochar properties at 17.1% and crop properties at 3.2%. The main elements that influenced the result have been determined as the characteristics of the soil (including the presence of different HM species and the amount of clay) and the quantity and attributes of the biochar (such as the temperature at which it was produced by pyrolysis). Furthermore, the RF model was further developed to predict bioaccumulation factors (BAF) and variations in crop uptake (CCU). The R2 values were found to be 0.7338 and 0.6997, respectively. Thus, machine learning (ML) models could be useful in understanding the behavior of HMs in soil–plant ecosystems by employing biochar additions. [ABSTRACT FROM AUTHOR]

Magnetic ion-imprinted polymers (MIIPs) are an innovative material that combines the selectivity of ion imprinting with the ease of separation provided by magnetic properties. Recent advancements in MIIPs have shown that they have higher selectivity coefficients compared to non-imprinted materials. The synthesis of MIIPs involves creating specific recognition sites for target ions in magnetic nanomaterials. Various nanomaterials, such as graphene oxide, carbon nanotubes, and silica, have been incorporated into the IIPs to improve their analytical performance for different environmental applications, including metal extraction, monitoring, detection, and quantification. This review stresses the need to develop new monomers with a high affinity for the target analyte and to find supporting materials with groups that facilitate the effective removal of the target analyte. It also explores the influence of experimental parameters on metal determination. [ABSTRACT FROM AUTHOR]

The increase in the world population and the intensification of agricultural practices have resulted in the release of several contaminants into the environment, especially pesticides and heavy metals. This article reviews recent advances in using adsorbent and catalytic materials for environmental decontamination. Different materials, including clays, carbonaceous, metallic, polymeric, and hybrid materials, are evaluated for their effectiveness in pollutant removal. Adsorption is an effective technique due to its low cost, operational simplicity, and possibility of adsorbent regeneration. Catalytic processes, especially those using metallic nanoparticles, offer high efficiency in degrading complex pesticides. Combining these technologies can enhance the efficiency of remediation processes, promoting a more sustainable and practical approach to mitigate the impacts of pesticides and other agricultural pollutants on the environment. Therefore, this review article aims to present several types of materials used as adsorbents and catalysts for decontaminating ecosystems affected by agricultural pollutants. It discusses recent works in literature and future perspectives on using these materials in environmental remediation. Additionally, it explores the possibilities of using green chemistry principles in producing sustainable materials and using agro-industrial waste as precursors of new materials to remove contaminants from the environment. [ABSTRACT FROM AUTHOR]

Medium-density fiberboard (MDF) waste generation has increased steadily over the past decades, and therefore, the investigation of novel methods to recycle this waste is very important. The potential of repurposing MDF waste as an adsorbent for the treatment of Cd(II), Cu(II), Pb(II), and Zn(II) ions in water was investigated using MDF offcuts. The highest adsorption potential in single-metal ion solution systems was observed for Pb(II) ions. The experimental data of Pb(II) ions fit well with the Freundlich isotherm and pseudo-second-order kinetic models. Complexation and electrostatic interactions were identified as the adsorption mechanisms. The adsorption behavior of multi-metal ion adsorption systems was investigated by introducing Cd(II) ions as a competitive metal ion. The presence of the Cd(II) ions reduced the adsorption potential of Pb(II) ions, yet the preference for the Pb(II) ions remained. Regeneration studies were performed by using 0.1 M HCl as a regeneration agent for both systems. Even though a significant amount of adsorbed metal ions were recovered, the adsorption potential of the MDF was reduced in the subsequent adsorption cycles. Based on these results, MDF fines have the potential to be used as an economical adsorbent for remediation of wastewater containing heavy metal ions. [ABSTRACT FROM AUTHOR]

Heavy metals and organic pollutants are prevalent in water bodies, causing great damage to the environment and human beings. Hence, it is urgent to develop a kind of adsorbent with good performance. Anion interlacing layered double hydroxides (LDHs) are a promising adsorbent for the sustainable removal of heavy metal ions and dyes from wastewater. Using aluminum chloride, zinc chloride and ammonium pentaborate tetrahydrate (NH4B5O8 · 4H2O, BA) as raw materials, the LDHs complex (BA-LDHs) of B5O8− intercalation was prepared by one-step hydrothermal method. The BA-LDHs samples were characterized by a X-ray powder diffractometer (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR) and the Brunauer–Emmett–Teller (BET) method. The results showed that B5O8- was successfully intercalated. Adsorption experimental results suggested that BA-LDHs possess a maximum adsorption capacity of 18.7, 57.5, 70.2, and 3.12 mg·g−1 for Cd(II), Cu(II), Cr(VI) and Methylene blue (MB) at Cs = 2 g·L−1, respectively. The adsorption experiment conforms to the Langmuir and Freundlich adsorption models, and the kinetic adsorption data are well fitted by the pseudo-second-order adsorption kinetic equation. The as-prepared BA-LDHs have potential application prospects in the removal of heavy metals and dyes in wastewater. More importantly, they also provide a strategy for preparing selective adsorbents. [ABSTRACT FROM AUTHOR]

Elements are released into water bodies, affecting the environment and human health. To address this problem, the adsorption-desorption capacity of untreated rice husk (URH) and rice husk treated with alkali (RHTA) for Cu(II), Pb(II), Fe(II), Cd(II), and Zn(II) was investigated. Analyses during the process were performed by X-ray diffraction (XRD), scanning electron microscopy, and elemental analysis by energy dispersive X-ray spectroscopy (SEM-EDS), as well as Fourier transform infrared spectroscopy (FTIR). Adsorption-desorption kinetics and isotherms were carried out. The FTIR analysis of RHTA revealed a lowering of intensity of the bonding signals (OH, C-O, CH2, CH3, SiO2, Si-OH) and loss of some signals due to the adsorbent-elements interaction. The adsorption on RHTA presented higher adsorption of Fe, followed by Pb, Zn, Cu, and Cd. Meanwhile, in URH, the adsorption was Fe > Pb > Cu > Zn and Cd. On the other hand, the desorption values for RHTA were Zn > Cd > Pb > Cu > and Fe and Zn > Cd > Cu > Pb and Fe for URH. The adsorption kinetics showed that data fit (R2 ≥ 0.89) to pseudo-second-order kinetics and Freundlich isotherms (R2 ≥ 0.84) for both ATRH and URH, indicating that the process occurs in the multilayer form and is controlled by chemisorption, where the adsorption depends on the active sites of the adsorbent surface. [ABSTRACT FROM AUTHOR]

Precipitation is an important factor that influences the quality of surface water in many regions of the world. The pollution of stormwater runoff from roads and parking lots is an understudied area in water quality research. Therefore, a comprehensive analysis of the physicochemical properties of rainwater flowing from parking lots was carried out, considering heavy metals and organic micropollutants. High concentrations of zinc were observed in rainwater, in addition to alkanes, e.g., tetradecane, hexadecane, octadecane, 2,6,10-trimethyldodecane, 2-methyldodecane; phenolic derivatives, such as 2,6-dimethoxyphenol and 2,4-di-tertbutylphenol; and compounds such as benzothiazole. To remove the contaminants present in rainwater, adsorption using silica carriers of the MCF (Mesostructured Cellular Foams) type was performed. Three groups of modified carriers were prepared, i.e., (1) SH (thiol), (2) NH2 (amino), and (3) NH2/SH (amine and thiol functional groups). The research problem, which is addressed in the presented article, is concerned with the silica carrier influence of the functional group on the adsorption efficiency of micropollutants. The study included an evaluation of the effects of adsorption dose and time on the efficiency of the contaminant removal process, as well as an analysis of adsorption isotherms and reaction kinetics. The colour adsorption from rainwater was 94–95% for MCF-NH2 and MCF-NH2/SH. Zinc adsorbance was at a level of 90% for MCF-NH2, and for MCF-NH2/SH, 52%. Studies have shown the high efficacy (100%) of MCF-NH2 in removing organic micropollutants, especially phenolic compounds and benzothiazole. On the other hand, octadecane was the least susceptible to adsorption in each case. It was found that the highest efficiency of removal of organic micropollutants and zinc ions was obtained through the use of functionalized silica NH2. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is considered as a promising adsorbent material for the removal of metal from aqueous environments. Here, we have used the density functional theory (DFT) approach and a combination of parameters to characterise the interactions of GO with lead (Pb) and cadmium (Cd), i.e., typical harmful metals often found in water. Our model systems consist of a singly and doubly adsorbed neutral ( Pb 0 , Cd 0 ) and charged ( Pb 2 + , Cd 2 + ) atoms adsorbed on the GO nanoparticle of the chemical formula C 30 H 14 O 15 . We show that a single charged metal ion binds more strongly than a neutral atom of the same type. Moreover, to determine the possibility of multiple adsorptions of the GO nanoparticle, two metal atoms of the same species were co-adsorbed on its surface. We found a site-dependent adsorption energy such that when two atoms of the same specie are adsorbed at sites S i and S j , the binding energy per atom depends on whether one of the two atoms is adsorbed firstly on the S i or S j sites. Furthermore, the binding energy per atom for the two co-adsorbed atoms of the same specie (i.e., neutral or charged) is less than the binding energy of a singly adsorbed atom. This suggests that atoms may become less likely to be adsorbed on the GO nanoparticle when their concentration increases. We adduce the origin of this observation to be interplay between the metal–metal interaction on the one hand and GO–metal on the other, with the former resulting in less binding for the charged adsorbed metals in particular, due to repulsive interaction between two positively charged ions. The frontier molecular orbitals analysis and the calculated global reactivity descriptors of the respective GO–metal complexes revealed that all the GO–metal complexes have a smaller HOMO–LUMO gap (HLG) relative to that of pristine metal-free GO nanoparticle. This may indicate that although the GO–metal complexes are stable, they are less stable compared to metal-free GO nanoparticles. The negative values of the chemical potentials obtained for all the GO–metal complexes further confirm their stability. Our work differs from previous experimental studies in that those lacked details of the interaction mechanisms between GO, Pb and Cd, as well as previous theoretical studies which used limited numbers of parameters to characterise the GO–metal interactions. Rather, we present a set of parameters or descriptors which provide comprehensive physical and electronic characterisation of GO–metal systems as obtained via the DFT calculations. These parameters, along with those reported in previous studies, may find applications in rational design and high-throughput screening of graphene-based materials for water purification, as an example. [ABSTRACT FROM AUTHOR]

Novel functionalized and/or grafted crosslinked chitosan adsorbents were synthesized and used to remove several toxic heavy metal ions such as nickel, lead, chromium, and cadmium ions from contaminated water. The chitosan biopolymer was functionalized by maleic anhydride (CS_MA) acting also as a crosslinking agent. Glutaraldehyde-crosslinked chitosan (CS_GA) grafted with poly(methyl methacrylate) (CS_MMA) was also synthesized. The synthesized adsorbents were characterized using a variety of analytical techniques such as SEM, TGA, and FTIR, which confirmed their chemical structures and morphology. The adsorption capacity of the adsorbents was analyzed under various conditions of contact time, adsorbent dose, initial concertation, temperature, and pH and evaluated against those of pure chitosan (CS) and the crosslinked chitosan(CS_GA). The ultimate removal conditions were 0.5 g/100 mL adsorbent dose, an initial metal ion concentration of 50 ppm, a temperature of 45 °C, and pH 9. CS_MMA had the highest removal percentages for all metal ions, ranging from 92% to 94%. The adsorption was demonstrated to fit a pseudo-first-order model that followed a Langmuir adsorption isotherm. The results highlight the capacity of the synthesized polymers to efficiently remove major toxic contaminants at low cost from contaminated water, present especially in low-income areas, without harming the environment. [ABSTRACT FROM AUTHOR]

Biochar enriched with metals has an increased potential for sorption of organic and inorganic pollutants. The aim of the research was to identify the possibility of using biochar composites produced on the basis of waste plant biomass and waste FFH (ferryferrohydrosol) containing iron atoms, after CO2 capture. The composites were produced in a one-stage or two-stage pyrolysis process. Their selected properties were determined as follows: pH, ash content, C, H, N, O, specific surface area, microstructure and the presence of surface functional groups. The produced biochar and composites had different properties resulting from the production method and the additive used. The results of experiments on the removal of methylene blue (MB) from solutions allowed us to rank the adsorbents used according to the maximum dye removal value achieved as follows: BC1 (94.99%), B (84.61%), BC2 (84.09%), BC3 (83.23%) and BC4 (83.23%). In terms of maximum amoxicillin removal efficiency, the ranking is as follows: BC1 (55.49%), BC3 (23.51%), BC2 (18.13%), B (13.50%) and BC4 (5.98%). The maximum efficiency of diclofenac removal was demonstrated by adsorbents BC1 (98.71), BC3 (87.08%), BC4 (74.20%), B (36.70%) and BC2 (30.40%). The most effective removal of metals Zn, Pb and Cd from the solution was demonstrated by BC1 and BC3 composites. The final concentration of the tested metals after sorption using these composites was less than 1% of the initial concentration. The highest increase in biomass on prepared substrates was recorded for the BC5 composite. It was higher by 90% and 54% (for doses of 30 g and 15 g, respectively) in relation to the biomass growth in the soil without additives. The BC1 composite can be used in pollutant sorption processes. However, BC5 has great potential as a soil additive in crop yield and plant growth. [ABSTRACT FROM AUTHOR]

Heavy metal contamination in drinking water is a growing concern due to its severe health effects on humans. Among the many metals, lead (Pb), which is a toxic and harmful element, has the most widespread global distribution. Pb pollution is a major problem of water pollution in developing countries and nations. The most common sources of lead in drinking water are lead pipes, faucets, and plumbing fixtures. Adsorption is the most efficient method for metal removal, and activated carbon has been used widely in many applications as an effective adsorbent, but its high production costs have created the necessity for a low-cost alternative adsorbent. Biochar can be a cost-effective substitute for activated carbon in lead adsorption because of its porous structure, irregular surface, high surface-to-volume ratio, and presence of oxygenated functional groups. Extensive research has explored the remarkable potential of biochar in adsorbing Pb from water and wastewater through batch and column studies. Despite its efficacy in Pb removal, several challenges hinder the real application of biochar as an adsorbent. These challenges include variability in the adsorption capacity due to the diverse range of biomass feedstocks, production processes, pH dependence, potential desorption, or a leaching of Pb from the biochar back into the solution; the regeneration and reutilization of spent biochar; and a lack of studies on scalability issues for its application as an adsorbent. This manuscript aims to review the last ten years of research, highlighting the opportunities and engineering challenges associated with using biochar for Pb removal from water. Biochar production and activation methods, kinetics, adsorption isotherms, mechanisms, regeneration, and adsorption capacities with process conditions are discussed. The objective is to provide a comprehensive resource that can guide future researchers and practitioners in addressing engineering challenges. [ABSTRACT FROM AUTHOR]

The process of mining produces a large amount of heavy metals and high-sulfate mine water, which is the main factor leading to environmental degradation in the mining area, and the removal of heavy metals and the recovery of sulfate from mine water is a difficult problem faced by mines today. Currently, sulfate is treated as a hazardous substance and is not recycled. In this paper, the precipitation–adsorption bipolar membrane electrodialysis (BMED) multi-technology-coupled recovery of sulfate method was used to treat mine water. The results showed that the coupling technology could remove heavy metals and sulfate in water better, while the sulfate desalination rate was about 96.8%, current efficiency was 54.2%, energy consumption was 0.823 kWh/kg, and the acid production concentration was 0.168 at an electrolyte concentration of 0.1 mol/L, an operating voltage of 12 V, an initial salt concentration of 30 g/L, and a flow rate of 3.5 mL/min. Mechanistic results showed that the precipitation–adsorption method could realize the removal of heavy metals from mine water. The BMED process realized the removal of sulfate and also the recovery of acid. The multi-technology coupling of precipitation–adsorption and bipolar membrane electrodialysis explored in this paper provides a direction for the in-depth treatment of mine water. [ABSTRACT FROM AUTHOR]

Water pollution, particularly from heavy metals, poses a significant threat to global health, necessitating efficient and environmentally friendly removal methods. This study introduces novel zeolite-based adsorbents, specifically alkali-activated foamed zeolite (AAFZ), for the effective adsorption of Cu(II) and Ni(II) ions from aqueous solutions. The adsorbents' capabilities were comprehensively characterized through kinetic and isotherm analyses. Alkaline activation induced changes in chemical composition and crystalline structure, as observed via XRF and XRD analyses. AAFZ exhibited a significantly larger pore volume (1.29 times), higher Si/Al ratio (1.15 times), and lower crystallinity compared to ZZ50, thus demonstrating substantially higher adsorption capacity for Cu(II) and Ni(II) compared to ZZ50. The maximum monolayer adsorption capacities of ZZ50 and AAFZ for Cu(II) were determined to be 69.28 mg/g and 99.54 mg/g, respectively. In the case of Ni(II), the maximum monolayer adsorption capacities for ZZ50 and AAFZ were observed at 48.53 mg/g and 88.99 mg/g, respectively. For both adsorbents, the optimum pH for adsorption of Cu(II) and Ni(II) was found to be 5 and 6, respectively. Equilibrium was reached around 120 min, and the pseudo-second-order kinetics accurately depicted the chemisorption process. The Langmuir isotherm model effectively described monolayer adsorption for both adsorbents. Furthermore, the regeneration experiment demonstrated that AAFZ could be regenerated for a minimum of two cycles using hydrochloric acid (HCl). These findings highlight the potential of the developed adsorbents as promising tools for effective and practical adsorption applications. [ABSTRACT FROM AUTHOR]

Graphene oxide and its magnetic nanoparticle-based composites are a well-known tool to remove heavy metals from wastewater. Unfortunately, one of the major issues in handling such small particles consists of their difficult removal from treated wastewater (even when their magnetic properties are exploited), due to their very small diameter. One possible way to overcome this problem is to embed them in a macroscopic biopolymer matrix, such as alginate or chitosan beads. In this way, the adsorbent becomes easier to handle and can be used to build, for example, a packed column, as in a traditional industrial adsorber. In this work, the removal performances of two different embedded magnetic nanocomposite adsorbents (MNAs) are discussed. The first type of MNA is based on ferrite magnetic nanoparticles (MNPs) generated by coprecipitation using iron(II/III) salts and ammonium hydroxide, while the second is based on a 2D material composed of MNP-decorated graphene oxide. Both MNAs were embedded in cross-linked alginate beads and used to treat artificial water contaminated with chromium(III), nickel(II), and copper(II) in different concentrations. The yield of removal and differences between MNAs and non-embedded magnetic nanomaterials are also discussed. From the results, it was found that the time to reach the adsorption equilibrium is higher when compared to that of the nanomaterials only, due to the lower surface/volume ratio of the beads, but the adsorption capacity is higher, due to the additional interaction with alginate. [ABSTRACT FROM AUTHOR]

Hybrid material-derived adsorbents have shown a great applicable efficiency in various fields, including industrial uses and environmental remediation. Herein, zinc oxide nanoparticle modified with carbon (ZnO-C) was fabricated and utilized for wastewater treatment through the adsorption of Zn(II), Cd(II), Co(II), and Mn(II). The surface and structural characteristics were examined using TEM, SEM, XRD, FTIR spectroscopy, EDS, and the BET surface area. Kinetics and equilibrium investigations were applied to optimize the adsorptive removal of Zn(II), Cd(II), Co(II), and Mn(II) onto ZnO-C. The results indicated that the formation of ZnO-C in crystalline sphere-like granules with a nano-size between 16 and 68 nm together with carbon matrix. In addition, the spherical granules of zinc oxide were gathered to form clusters. FTIR spectroscopy indicated that the ZnO-C surface was rich with OH groups and ZnO. The adsorption capacity 215, 213, 206, and 231 mg/g for Zn(II), Cd(II), Co(II), and Mn(II), respectively, at the optimal conditions pH between 5 and 6, a contact time of 180 min, and an adsorbent dose of 0.1 g/L. The adsorptive removal data modeling for the uptake of Zn(II), Cd(II), Co(II), and Mn(II) onto ZnO-C showed agreement with the assumption of the pseudo-second-order kinetic model and the Freundlich isotherm, suggesting a fast adsorption rate and a multilayered mechanism. The achieved adsorption capacity using the prepared ZnO-C was more effective compared to ZnO, carbon, Fe3O4, and Fe3O4-C. Real wastewater samples were applied, including valley water, industrial wastewater, and rain wastewater, and evaluated for the applicable uptake of Zn(II), Cd(II), Co(II), and Mn(II) using ZnO-C and Fe3O4-C with effective removal efficiency. [ABSTRACT FROM AUTHOR]

With the increasing concern about antimony (Sb) pollution and remediation in aquatic ecosystems, more and more feasible technologies have been developed. Adsorption has been extensively studied due to the simplicity of its operation and its minimal environmental effects, but the lack of cheap and stable adsorbents has limited its application in Sb treatment. In this study, pseudo-boehmite (PB) was successfully synthesized via aluminum isopropylate hydrolysis, and its potential for removing Sb(V) from wastewater was explored. The removal efficiency of Sb(V) was 92.50%, and the maximum adsorption capacity was 75.25 mg/g under optimal conditions (pH 5.0, 2 g·L−1 PB, and 10 mg·L−1 Sb(V)). In addition, better performance could be obtained at acidic conditions (pH 3.0–5.0). Surface complexation, electrostatic attraction, and hydrogen bonding were identified as potential major processes for Sb(V) elimination by PB based on experimental and characterization data. This study presents a promising approach for the efficient removal of Sb(V) from wastewater, offering a new insight into the application of aluminum-based materials for heavy metal removal. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is a major environmental problem caused by the release of acidic, toxic, and sulfate-rich water from mining sites. This study aimed to develop novel adsorbents for the removal of chromium (Cr(VI)), cadmium (Cd(II)), and lead (Pb(II)) from simulated and actual AMD using hybrid ion-exchange resins embedded with hydrous ferric oxide (HFO). Two types of resins were synthesized: anionic exchange resin (HAIX-HFO) for Cr(VI) removal and cationic exchange resin (HCIX-HFO) for Cd(II) and Pb(II) removal. The resins were characterized using scanning electron microscopy and Raman spectroscopy, which confirmed the presence of HFO particles. Batch adsorption experiments were conducted under acidic and sulfate-enhanced conditions to evaluate the adsorption capacity and kinetics of the resins. It was found that both resins exhibited high adsorption efficiencies and fast adsorption rates for their respective metal ions. To explore the potential adsorption on actual AMD, HCIX-HFO demonstrated significant removal of some metal ions. The saturated HCIX-HFO resin was regenerated using NaCl, and a high amount of the adsorbed Cd(II) and Pb(II) was recovered. This study demonstrates that HFO-embedded hybrid ion-exchange resins are promising adsorbents for treating AMD contaminated with heavy metals. [ABSTRACT FROM AUTHOR]

Wastewater discharges from industrial processes typically include elevated concentrations of contaminants, which largely consist of potentially harmful chemicals such as heavy metals. These contaminants are characterized by their slow rate of decomposition. Hence, the removal of these metallic ions from effluents poses a challenge. Among different treatments, the adsorption approach has considerable potential due to its ability to effectively eliminate both soluble and insoluble pollutants from effluent, even at lower levels of concentration. Of various wastes, fly ash (FA) material has been the subject of attention because it is abundant, has favorable qualities, and contains a high percentage of minerals. This review investigates multiple facets, with a specific focus on the application of FA, an industrial byproduct, as an adsorbent in removing heavy metals. A comprehensive examination was conducted on a range of concerns pertaining to the pollution caused by metallic ions, including the underlying causes, levels of contamination, health implications of heavy metals, and removal methods. Multiple factors were found to affect the adsorption process. Of all the factors, the pH value considerably influences the elimination of heavy metals. An acidic pH range of 2.5–4.5 was found to be optimal for achieving the highest possible elimination of As(V), Cu(II), Hg(II), and Cr(VI). The latter elimination rate reached 89% at the optimal pH level. Most heavy metals' adsorption isotherms conformed to the Langmuir or Freundlich models, while the pseudo-second-order kinetics provided a satisfactory match for their removal. Using a raw FA, adsorption capacities were achieved in the removal of metallic ions, Ni(II), Pb(II), and Cr(VI), that ranged from 14.0 to 23.9 mg g−1. Meanwhile, the FA-zeolite showed a remarkable capacity to adsorb ions Mn(II), Ni(II), Cd(II), Cu(II), and Pb(II), with values ranging from about 31 to 66 mg g−1. The cost analysis showed that the treatment of FA is economically advantageous and may result in significant cost reductions in comparison to commercial adsorbents. In summary, FA is an inexpensive waste material with potential for water treatment applications and several other purposes due to its excellent chemical and mineralogical composition. [ABSTRACT FROM AUTHOR]

With the development of industrial activities and the agricultural and mining industries, farmland soils are facing serious problems related to heavy metal contamination, especially cadmium (Cd) and arsenic (As) contamination. In this study, two industrial by-products, phosphogypsum (PG) and red mud (RM), were modified by lanthanum (La) impregnation to form a new composite (L-PR) to investigate the adsorption performance of Cd(II)/As(V) in both single and binary systems. The adsorption mechanisms of Cd(II)/As(V) on L-PR were analyzed using SEM, XRD, FTIR, and XPS. The passivation effect of L-PR on the Cd-As composite contaminated soil was confirmed through a soil cultivation experiment. The adsorption experiments revealed that L-PR showed superior adsorption capabilities for Cd(II) and As(V) compared to PG and RM. Additionally, L-PR was found to be less affected by changes in pH. The kinetic studies indicated that Cd(II) and As(V) adsorption by L-PR followed the second-order kinetic model most accurately. Isothermal adsorption experiments revealed that the adsorption of Cd(II) by L-PR was more in accordance with the Freundlich model, while As(V) was more in accordance with the Langmuir model. The mechanisms of Cd(II) and As(V) adsorption on L-PR involved electrostatic attraction, ion exchange, complexation, and precipitation. The adsorption of Cd(II) is dominated by complexation and precipitation, and the adsorption of As(V) is dominated by ion exchange and complexation. Soil cultivation experiments showed that L-PR significantly reduced the available Cd and As concentrations in soil by 86.01% and 27.80%, respectively, and it could induce the transformation of non-stable Cd(II)/As(V) to the more stable residual. In summary, L-PR exhibits facile preparation, excellent adsorption performance, and is capable of simultaneously removing Cd(II) and As(V) from aqueous solutions while immobilizing these contaminants in soil. These remarkable attributes made it a highly promising alternative for the simultaneous treatment of various toxic metal contaminants. [ABSTRACT FROM AUTHOR]

Toxic heavy metals are ubiquitous in the aquatic environment and show a significant danger to human health. Carbon nanotubes have been extensively used in treating the contamination of groundwater due to their porous multi-layer nature. Batch tests revealed that oxidized multiwalled carbon nanotubes (O-MWCNTS) offer better removal of Pb(II). The removal rate of Pb(II) was 90.15% at pH 6 within 24 h, which was ~58% more than that of Cd(II). The removal rate decreased to 55.59% for Pb(II) and to 16.68% for Cd(II) when the initial concentration of Pb(II)/Cd(II) ranged from 5 to 15 mg·g−1. The removal rate in the competitive tests was about 60.46% for Pb(II) and 9.70% for Cd(II). The Langmuir model offered better description of the adsorptive data for both ions. And the Qm of Pb(II) was 5.73 mg·g−1, which was 2.39 mg·g−1 more than that of Cd(II) in a single-icon system, while Qm was 7.11 mg·g−1 with Pb(II) and 0.78 mg·g−1 with Cd(II) in competitive water. And thermodynamic tests further indicated that the activating energy of Pb(II) and Cd(II) was 83.68 and 172.88 kJ·mol−1, respectively. Lead and cadmium adsorbed on the surface of O-MWCNTS are antagonistic in the competitive system. Based on XPS analyses, it was concluded that the absorbed lead/cadmium species on O-MWCNTS were (-COO)2Pb, (-COO)Pb(-O)/(-COO)2Cd, and (-COO)Cd(-O). Additionally, they offered theoretical evidence supporting the practicality of using nanocomposite membranes as a means to remove cadmium and lead. [ABSTRACT FROM AUTHOR]

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced. [ABSTRACT FROM AUTHOR]

Elevated concentrations of heavy metals in natural waters can cause significant ecological problems. It is therefore essential to ensure their removal from any water discharged into the environment immediately, especially in case of an accident, where there is a risk of releasing large quantities or high concentrations. The aim of this paper is to test a newly developed adsorbent for the removal of heavy metals from aqueous solutions—in particular, it is very fast adsorption, and thus efficiency, during clean-ups. The alkali-activated foamed zeolite adsorbent was laboratory-prepared and -tested in both batch and flow-through arrangements on single and multi-component solutions and compared with natural zeolite. The experimental setup for batch adsorption consisted of a set of samples and solutions containing iron, cobalt, manganese, zinc and nickel. The samples were put on a horizontal shaker with a 500 mg adsorbent loading in a 50 mL solution. The column adsorption experimental setup consisted of a glass column with an inside diameter of 15 mm and a bed length of 165 mm. A measured amount of each adsorbent was added to the column to achieve a filter fixed-bed height of 160 mm. The high efficiency of the tested adsorbent on various heavy metals was confirmed. The adsorbent has a high potential for use in decontamination processes, water protection and landscape revitalization. Due to its rapid precipitation and subsequent fixation of metal cations in the form of insoluble oxide or hydroxide, it can be used as an emergency adsorbent, the great advantage of which is its low production cost and natural origin. [ABSTRACT FROM AUTHOR]

Constructed wetlands are a versatile technology for various treatment approaches, especially in emerging countries. The research aims to study and optimize the hybridizing process of a vertical subsurface flow constructed wetland with adsorption technology to provide energy-efficient and sustainable removal of heavy metals and bulk organics before their discharge into water bodies or water reuse for irrigation. This study focuses on the adsorption of selected heavy metals present in sewage from Kanpur, India, a cluster of tanning industries and other relevant industrial polluters, investigating the pollutant adsorption onto activated carbon and zeolites in batch and column tests. The results of the batch tests indicated high zeolite loading rates for lead (91.6 mg/g), chromium (60.8 mg/g) and copper (47.4 mg/g). In the column tests applying different adsorbent combinations and ratios, the average removal rates were as follows: 54.6% for cadmium, 14.1% for chromium, 52.4% for copper, 2.2% for iron, 29.2% for manganese, 26.6% for nickel, 35.2% for lead and 44.6% for zinc. The column tests conducted in preparation for field testing in pilot wetlands showed that shorter retention times and background bulk organic concentrations, as well as high ammonium concentrations, negatively affected heavy metal removal by reducing the adsorption and ion exchange capacity of the adsorbents. [ABSTRACT FROM AUTHOR]

Using straightforward and cost-effective methods, persimmon leaves were converted into high-quality powder. This powder was applied as an adsorbent for the removal of Cu(II) and Cd(II) from aqueous solutions. Scanning electron microscopy (SEM) revealed the presence of particles with non-homogeneous sizes and rough textures. The biosorbent exhibited a specific surface area of approximately 0.44 ± 0.015 m2 g−1. Elemental analysis and energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of elements such as sulfur, phosphorus, nitrogen, and oxygen. The results of 13C nuclear magnetic resonance (13C-NMR), obtained using the cross-polarization technique, show the presence of groups containing sulfur and oxygen. Infrared spectroscopy (FTIR) indicated the existence of amine and hydroxyl groups. The material was used in the solid-phase extraction of Cu(II) and Cd(II) in batch experiments, and its adsorption capacity was evaluated as a function of time, pH, and analyte concentration. The fraction with a diameter between 63 and 106 μm was selected for the adsorption tests. Kinetic equilibrium was reached within 5 min, and the experimental data were fitted to the pseudo-second-order kinetic model. The optimum pH for the adsorption of both metal species was approximately 5.0. The adsorption isotherms were adjusted using the modified Langmuir equation, and the maximum amount of metal species extracted from the solution was determined to be 0.213 mmol g−1 for Cu(II) and 0.215 mmol g−1 for Cd(II), with high linear correlation coefficients for both metals. Persimmon leaves are typically abundant during the growing season, and because they are seasonal, the Diospyros kaki L.f. tree undergoes the natural process of leaf abscission, ensuring the availability of leaves for application. [ABSTRACT FROM AUTHOR]

Pharmaceuticals and heavy metals pose significant risks to human health and aquatic ecosystems, necessitating their removal from water and wastewater. A promising alternative for this purpose involves their removal by adsorption on composite sorbents prepared using a conventional layer-by-layer (LbL) method or an innovative coacervate direct deposition approach. In this study, four novel composite materials based on a silica core (IS) and a polyelectrolyte coacervate shell were used for the investigation of dynamic adsorption of three heavy metals (lead, nickel and cadmium) and an organic drug model (diclofenac sodium salt, DCF-Na). The four types of composite sorbents were tested for the first time in dynamic conditions (columns with continuous flow), and the column conditions were similar to those used in wastewater treatment plants. The influence of the polyanion nature (poly(acrylic acid) (PAA) vs. poly(sodium methacrylate) (PMAA)), maintaining a constant poly(ethyleneimine) (PEI), and the cross-linking degree (r = 0.1 and r = 1.0) of PEI chains on the immobilization of these pollutants (inorganic vs. organic) on the same type of composite was also studied. The experiments involved both single- and multi-component aqueous solutions. The kinetics of the dynamic adsorption process were examined using two non-linear models: the Thomas and Yoon–Nelson models. The tested sorbents demonstrated good adsorption capacities with affinities for the metal ions in the following order: Pb2+ > Cd2+ > Ni2+. An increase in the initial diclofenac sodium concentration led to an enhanced adsorption capacity of the IS/(PEI-PAA)c-r1 sorbent. The calculated sorption capacities were in good agreement with the adsorption capacity predicted by the Thomas and Yoon–Nelson models. The substantial affinity observed between DCF-Na and a column containing composite microparticles saturated with heavy metal ions was explained. [ABSTRACT FROM AUTHOR]

Lignosulfonate/polyaniline (LS/PANI) nanocomposite adsorbent materials were prepared by the chemical polymerization of lignosulfonate with an aniline monomer as a dopant and structure-directing agent, and the adsorption behavior of dyes as well as heavy metal ions was investigated. LS/PANI composites were used as dye adsorbents for the removal of different cationic dyes (malachite green, methylene blue, and crystal violet). The adsorption behavior of LS/PANI composites as dye adsorbents for malachite green was investigated by examining the effects of the adsorbent dosage, solution pH, initial concentration of dye, adsorption time, and temperature on the adsorption properties of this dye. The following conclusions were obtained. The optimum adsorption conditions for the removal of malachite green dye when LS/PANI composites were used as malachite green dye adsorbents were as follows: an adsorbent dosage of 20 mg, an initial concentration of the dye of 250 mg/L, an adsorption time of 300 min, and a temperature of 358 K. The LS/PANI composite adsorbed malachite green dye in accordance with the Langmuir adsorption model and pseudo-second-order kinetic model, which belongs to chemisorption-based monomolecular adsorption, and the equilibrium adsorption amount was 245.75 mg/g. In particular, the adsorption of heavy metal ion Pb2+ was investigated, and the removal performance was also favorable for Pb2+. [ABSTRACT FROM AUTHOR]

This study explores the potential of modified shrimp-based chitosan (MSC) as an innovative adsorbent for eliminating heavy metals (HMs) from contaminated water sources. The modifications encompassed various chemical treatments, surface functionalization, and structural optimization to enhance the chitosan's adsorption capabilities. Comprehensive analyses using FT-IR and SEM-EDS were conducted to evaluate the properties of the chitosan. The adsorption capacity of MSC was assessed using ICP-MS before and after the adsorption process. Moreover, the study investigated the efficiency of HM removal by MSC under different conditions, including variations in pH, adsorbent dosage, and contact time. Under neutral pH conditions, the highest adsorption rates of copper, zinc, cadmium, and lead were determined as 99.72%, 84.74%, 91.35%, and 99.92%, respectively, with corresponding adsorption capacities of 20.30 mg/g for copper, 7.50 mg/g for zinc, 15.00 mg/g for cadmium, and 76.34 mg/g for lead. Analysis based on the Langmuir and Freundlich isotherm models revealed highly significant adsorption of HMs, supported by strong correlation coefficients (r2 > 0.98) obtained from the data. The pseudo-second-order kinetic model with linear coefficients (r2) greater than 0.97 effectively explained the kinetic studies of metal adsorption employing modified shrimp shells. These coefficients indicate a robust fit of the models to the experimental adsorption data for heavy metals. Further confirmation of the effectiveness of the adsorbent was obtained through FT-IR spectroscopy, which confirmed the presence of specific functional groups on the adsorbent, such as N–H joined with –COO−, H–O, C−O−C, and C–H. Additionally, the SEM-EDS analysis detected the presence of elements on the surface of MSC chitosan. The results emphasize that MSC is a highly effective and cost-efficient adsorbent for eliminating Cu, Zn, Cd, and Pb from wastewater, making it a promising eco-friendly choice. [ABSTRACT FROM AUTHOR]

Reducing waste, including waste generated through environmentally protective processes, is a primary goal of the circular economy. It is important to properly dispose of waste to promote sustainability and a cleaner environment. This article considered the disposal method for spent adsorbents using ceramic technology. The results indicate that the addition of spent adsorbent does not significantly reduce the performance characteristics of ceramic materials while providing an efficiency of over 99% for Cr (VI) retention in all experiments. [ABSTRACT FROM AUTHOR]

Environmental pollution has been widely considered by researchers, especially the heavy metals damage to the human and ecological environment is irreversible. Adsorption is an important method to remove heavy metal ions from the environment. In this paper, humic acid (HA) was functionalized by the improved Hummers method, and its adsorption capacity for Pb(II) was studied. The results of scanning electron microscope (SEM), X-ray diffraction (XRD), Roman, and Brunauer-Emmett-Teller (BET) showed that the thickness of irregular particles decreases to a layered structure during the transformation process. In addition, X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectra (FT-IR) spectra showed that the surface of oxidized-biochar (OBC) was rich in reactive oxygen species, which was conducive to the formation of coordination bonds with Pb(II). Further adsorption experiments showed that it was a spontaneous monolayer chemisorption. The results of the DFT calculation showed that -COOH had the lowest adsorption energy for Pb(II), and it was easier to form stable chemical bonds than -OH, -C=O, and -C-O-C-. Because those oxygen-containing functional groups not only can promote electrostatic attraction but also are more favorable for forming a covalent bond with Pb(II). This study had guiding significance for the deep modification and application of weathered coal as a heavy metal ion adsorbent or cation exchanger. [ABSTRACT FROM AUTHOR]

Due to its high carbon content, lignin, particularly for lignin-containing solid waste, is considered an excellent raw material for the preparation of carbon materials like biochar. To produce high-quality lignin-based biochar (LGBCs), lignin extracted from black liquor was employed to prepare biochar at various pyrolysis temperatures (300~600 °C). The physicochemical properties of LGBCs were assessed using scanning electron microscopy, N2 adsorption/desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. Furthermore, the adsorption capability and potential mechanism of LGBCs in removing Cd(II) were investigated as well. The results indicate that LGBCs produced at higher pyrolysis temperatures exhibit rougher surfaces and more developed pore structures, which facilitate the exposure of numerous active adsorption sites. The adsorption of Cd(II) by LGBCs generally follows the order of LG-300C < LG-400C < LG-500C < LG-600C. According to the Langmuir adsorption isotherm model, the theoretical maximum adsorption capacity of LG-600C for Cd(II) is calculated to be 18.54 mg/g. Adsorption mechanism analysis reveals that the complexation interaction, dependent on the surface functional groups, plays a crucial role in the adsorption of Cd(II) by LGBCs prepared at higher pyrolysis temperatures. This study demonstrates that, by controlling the pyrolysis temperature during biochar preparation, high-quality lignin-based biochar can be readily obtained. [ABSTRACT FROM AUTHOR]

Using agricultural and forestry wastes as raw materials, adsorbent materials were prepared for dye adsorption in wastewater, which can minimize the environmental load and fully realize sustainability by treating waste with waste. Taking lignosulfonate as a raw material, due to its molecular structure having more reactive groups, it is easy to form composite materials via a chemical oxidation reaction with an aniline monomer. After that, using a sodium lignosulfonate/polyaniline composite as the precursor, the activated high-temperature pyrolysis process is used to prepare porous carbon materials with controllable morphology, structure, oxygen, sulfur, and nitrogen content, which opens up a new way for the preparation of functional carbon materials. When the prepared O-N-S co-doped activated carbon materials (SNC) were used as adsorbents, the adsorption study of cationic dye methylene blue was carried out, and the removal rate of SNC could reach up to 99.53% in a methylene blue solution with an initial concentration of 100 mg/L, which was much higher than that of undoped lignocellulosic carbon materials, and the kinetic model conformed to the pseudo-second-order kinetic model. The adsorption equilibrium amount of NC (lignosulfonate-free) and SNC reached 478.30 mg/g and 509.00 mg/g, respectively, at an initial concentration of 500 mg/L, which was consistent with the Langmuir adsorption isothermal model, and the adsorption of methylene blue on the surface of the carbon material was a monomolecular layer. The adsorption of methylene blue dye on the carbon-based adsorbent was confirmed to be a spontaneous and feasible adsorption process by thermodynamic parameters. Finally, the adsorption of SNC on methylene blue, rhodamine B, Congo red, and methyl orange dyes were compared, and it was found that the material adsorbed cationic dyes better. Furthermore, we also studied the adsorption of SNC on different kinds of heavy metal ions and found that its adsorption selectivity is better for Cr3+ and Pb2+ ions. [ABSTRACT FROM AUTHOR]

This study investigates the performance of municipal compost as a heavy metal adsorbent for environmental protection systems. The performed assays test the effects of the pH (2–9) and contact time (5–250 min) on metal retention. To simulate leaching in natural systems, the soluble organic fraction was removed, leading to variations in the surface properties, including a 10% increase in the cation exchange capacity (CEC) and a 242% increase in the BET-specific surface area, accompanied by a small decrease in the surface charge (characterized by a less negative zeta potential values) of the washed municipal compost (WMC). Notably, these variations, which have not been found in previous research, yielded improved retention of Cu(II) and Zn(II) compared to raw municipal compost (RMC), attaining 96% retention for Cu(II) and 97% retention for Zn(II) at a pH of approximately 6.8–7.2 for a contact time of 120 min. The vast availability, cost-effectiveness, and resistance to desorption make municipal compost a viable option in a circular economy context for mitigating metal pollution across various environmental conditions. It is worth noting that this study can serve as a proxy for the expected outcomes in long-term exposure to environmental protection systems, enhancing the practical relevance of using compost for metal retention purposes. [ABSTRACT FROM AUTHOR]

Renewable and biodegradable polysaccharides have attracted interest for their wide applicability, among them their use as sorbents for heavy metal ions. Their high sorption capacity is due mainly to the acidic groups that populate the polysaccharide backbone, for example, carboxylic groups in alginate and sulfate ester groups in the iota and lambda carrageenans. In this study, these three polysaccharides were employed, alone or in different mixtures, to recover different heavy metal ions from aqueous solutions. All three polysaccharides were capable of adsorbing Eu3+, Sm3+, Er3+, or UO22+ and their mixtures, findings that were also confirmed using XPS, TGA, and FTIR analyses. In addition, the highest sorption yields of all the metal ions were obtained using alginate, alone or in mixtures. While the alginate with carboxylic and hydroxyl groups adsorbed different ions with the same selectivity, carrageenans with sulfate ester and hydroxyl groups exhibited higher adsorption selectivity for lanthanides than for uranyl, indicating that the activity of the sulfate ester groups toward trivalent and smaller ions was higher. [ABSTRACT FROM AUTHOR]

Superparamagnetic magnetic nanoparticles (MNPs, Fe3O4) were first synthesized based on a chemical co–precipitation method, and the core–shell magnetic silica nanoparticles (MSNPs, Fe3O4@SiO2) were obtained via hydrolysis and the condensation of tetraethyl orthosilicate onto Fe3O4 seed using a sol–gel process. Following that, MSNPs were immobilized using a three–step grafting strategy, where 8-hloroacetyl–aminoquinoline (CAAQ) was employed as a metal ion affinity ligand for trapping specific heavy metal ions, and a macromolecular polymer (polyethylenimine (PEI)) was selected as a bridge between the surface hydroxyl group and CAAQ to fabricate a network of organic networks onto the MSNPs' surface. The as–synthesized MSNPs–CAAQ nanocomposites possessed abundant active functional groups and thus contained excellent removal features for heavy metal ions. Specifically, the maximum adsorption capacities at room temperature and without adjusting pH were 324.7, 306.8, and 293.3 mg/g for Fe3+, Cu2+, and Cr3+ ions, respectively, according to Langmuir linear fitting. The adsorption–desorption experiment results indicated that Na2EDTA proved to be more suitable as a desorbing agent for Cr3+ desorption on the MSNPs–CAAQ surface than HCl and HNO3. MSNPs–CAAQ exhibited a satisfactory adsorption capacity toward Cr3+ ions even after six consecutive adsorption–desorption cycles; the adsorption efficiency for Cr3+ ions was still 88.8% with 0.1 mol/L Na2EDTA as the desorbing agent. Furthermore, the MSNPs–CAAQ nanosorbent displayed a strong magnetic response with a saturated magnetization of 24.0 emu/g, and they could be easily separated from the aqueous medium under the attraction of a magnet, which could facilitate the sustainable removal of Cr3+ ions in practical applications. [ABSTRACT FROM AUTHOR]

The presence of heavy metals with high acute toxicity in wastewater poses a substantial risk to both the environment and human health. To address this issue, we developed a nanocomposite of alginate-encapsulated polypyrrole (PPy) decorated with α-Fe2O3 nanoparticles (Alg@Mag/PPy NCs), fabricated for the removal of mercury(II) from synthetic wastewater. In the adsorption experiments, various parameters were examined to identify the ideal conditions. These parameters included temperature (ranging from 298 to 323 K), initial pH levels (ranging from two to nine), interaction time, amount of adsorbent (from 8 to 80 mg/40 mL), and initial concentrations (from 10 to 200 mg/L). The results of these studies demonstrated that the removal efficiency of mercury(II) was obtained to be 95.58% at the optimum pH of 7 and a temperature of 303 K. The analysis of adsorption kinetics demonstrated that the removal of mercury(II) adhered closely to the pseudo-second-order model. Additionally, it displayed a three-stage intraparticle diffusion model throughout the entire adsorption process. The Langmuir model most accurately represented equilibrium data. The Alg@Mag/PPy NCs exhibited an estimated maximum adsorption capacity of 213.72 mg/g at 303 K, surpassing the capacities of most of the other polymer-based adsorbents previously reported. The thermodynamic analysis indicates that the removal of mercury(II) from the Alg@Mag/PPy NCs was endothermic and spontaneous in nature. In summary, this study suggests that Alg@Mag/PPy NCs could serve as a promising choice for confiscating toxic heavy metal ions from wastewater through adsorption. [ABSTRACT FROM AUTHOR]

Chitosan/Hydroxyapatite composites, enriched with relatively active -NH2 and -OH groups, have emerged as promising adsorbents for heavy metal removal. In this study, we harnessed the potential of CS/HAP composites by developing monolithic PLA@CS/HAP filters utilizing 3D printing and freeze-drying techniques. These filters possess both macroscopic and microscopic porous structures, endowing them with exceptional capabilities for removing heavy metals from water. The adsorption properties of CS/HAP composites were explored by varying the dosage, duration, and initial concentrations of copper ions. The maximum adsorption capacity for Cu2+ was determined to be approximately 119+/−1 mg/g at the natural pH and 298 K. Notably, the monolithic PLA@CS/HAP filters demonstrated remarkable efficiency in the removal of copper ions, with 90% of copper ions effectively removed within a mere 2-h period in a cyclic adsorption experiment. Furthermore, the PLA@CS/HAP filters exhibited a robust dynamic Cu2+ removal capacity (80.8% or even better in less than 35 min) in a dynamic adsorption experiment. Importantly, all materials employed in this study were environmentally friendly. In summary, the PLA@CS/HAP filter offers advantages such as ease of preparation, eco-friendliness, versatility, and broad applicability in diverse wastewater treatment scenarios, thereby presenting a significant potential for practical implementation. [ABSTRACT FROM AUTHOR]

The modification of pristine biochar derived from the waste of sweet prickly pear using the green modification method to produce nano-sized biochar (nanobiochar) for the removal of steroidal hormones and heavy metals from water and wastewater is reported in this study. Based on the characterisation results using FTIR, Raman spectroscopy, and XPS, the material had (COOH), (C=O), and (OH) functional groups typical of graphitic amorphous carbon. The SEM-EDS and XRD results showed that the material was mesoporous and amorphous in nature. The BET analysis results revealed that the surface area significantly increased from 220.1 m2/g to 354.6 m2/g after the modification of the pristine biochar. Based on the TGA-DSC results, the material was thermally stable up to 550 °C. A complete factorial experimental design using Minitab 21 Statistical Software (version 18.1) was employed to optimise the experimental adsorption conditions. The F-values and p-values for the lack-of-fit of the model showed the acceptability and significance of the ANOVA model. The Freundlich adsorption isotherm was found to provide a better fit for the steroid adsorption data than the Langmuir adsorption isotherm, with moderate values of R2 ≥ 0.92 for Langmuir and R2 ≥ 0.95 for Freundlich, as well as maximum adsorption capacities of 14.53 mg/g, 10.58 mg/g, 12.50 mg/g, 5.73 mg/g, 5.63 mg/g, and 9.75 mg/g obtained for estriol, α-oestradiol, β-oestradiol, testosterone, progesterone, and bisphenol A. Freundlich R2 values were lower than Langmuir R2 values for metal adsorption, with maximum adsorption capacities of 8.58 mg/g, 4.15 mg/g, and 6.95 mg/g obtained for nickel, cadmium, and lead, respectively. The maximum percentage of removal for effluents and influents was between 84–89% and 78–86% for steroid hormones and heavy metals, respectively. The highest removal percentage between 90–95% was obtained for spiked ultrapure water for both steroid hormones and heavy metals. The material exhibited a removal percentage up to 60% after the first four cycles. [ABSTRACT FROM AUTHOR]

The usage of a highly efficient, low-cost, and sustainable adsorbent material as an industrial wastewater treatment technique is required. Herein, the usage of the novel, fully sustainable tannin-5-(hydroxymethyl)furfural (TH) aerogels, generated via a water-based sol–gel process, as compatible biosorbent materials is presented. In particular, this study focusses on the surface modification of the tannin biosorbent with carboxyl or amino functional groups, which, hence, alters the accessible adsorption sites, resulting in increased adsorption capacity, as well as investigating the optimal pH conditions for the adsorption process. Precisely, highest adsorption capacities are acquired for the metal cations and cationic dye in an alkaline aqueous environment using a carboxyl-functionalized tannin biosorbent, whereas the anionic dye requires an acidic environment using an amino-functionalized tannin biosorbent. Under these determined optimal conditions, the maximum monolayer adsorption capacity of the tannin biosorbent ensues in the following order: Cu2+ > RB > Zn2+ > MO, with 500, 244, 192, 131 mg g−1, respectively, indicating comparable or even superior adsorption capacities compared to conventional activated carbons or silica adsorbents. Thus, these functionalized, fully sustainable, inexpensive tannin biosorbent materials, that feature high porosity and high specific surface areas, are ideal industrial candidates for the versatile adsorption process from contaminated (heavy) metal or dye solutions. [ABSTRACT FROM AUTHOR]

This study presents a novel polyurethane-activated carbon composite (PACC) as an effective and sustainable adsorbent for treating lead-ion-contaminated waters. The PACC was characterized using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer, Emmett, and Teller (BET) surface area analyzer, X-ray Diffraction (XRD), and Thermogravimetric Analyzer (TGA) to evaluate its physicochemical and thermal properties. Furthermore, the PACC was employed in an experimental column adsorption setup to investigate its adsorption performance and to develop a dynamic method suitable for industrial implementation. Parameters such as bed height (50, 100, 150 mm), flow rate (4, 6, 8 mL min−1), pH (2, 4, 6), and initial metal-ion concentrations (10, 50, 100 mg L−1) were examined. The experimental data exhibited strong agreement with the Thomas and Yoon–Nelson models (R2 ≥ 0.96), indicating efficient adsorption mechanisms. Remarkably, the used adsorbent has the potential for facile regeneration without substantial loss in capacity. The PACC demonstrated excellent adsorption performance for lead ions in aqueous solutions in a fixed-bed column system. Thus, the novel PACC material holds the potential for scalable application in industrial settings to address water pollution challenges, especially in regions with uncontrolled effluent discharge. [ABSTRACT FROM AUTHOR]

This study used porous nanomaterials MCM-41 and SBA-15, as well as their modified species, to remove lead and cadmium ions from water. We used X-ray diffraction (XRD), a scanning electron microscope (SEM), the Brunauer–Emmett–Teller (BET), and the Fourier transform infrared (FT-IR) method to investigate the characteristics of porous nanomaterials. Additionally, atomic absorption spectroscopy (AAS) measured the concentration of lead and cadmium ions. The stratigraphic analysis showed the samples' isothermal shape to be type IV. This study investigated the amount, absorbent, pH changes, and adsorption time parameters. We observed that the adsorption efficiency of lead by the synthesized samples was higher than that of the adsorption of cadmium. Mesoporous structures also displayed increased adsorption efficiency due to the amino group. Four testing stages were conducted to determine the reproducibility of the adsorption by the synthesized samples, with the results showing no significant changes. As a result of the adsorption process, the structure of the recycled sample N H 2 - M C M - 41 was preserved. We also used artificial neural networks (ANN) to propose predictive models based on the experimental results. The ANN models were very accurate, such that the mean absolute error (MAE) was less than 2% and the R 2 was higher than 0.98. [ABSTRACT FROM AUTHOR]

This study aims to comprehensively investigate the current advances in water treatment technologies for the elimination of heavy metals using biomass-based adsorbents. The enhancement of adsorption capacity in biomass materials is achieved through surface modification, which increases their porosity and surface area. The study therefore focuses on the impact of different surface modification techniques on the adsorption capacity, as well as the evaluation of adsorptive removal techniques and the analysis of various isotherm and kinetics models applied to heavy metal contaminants. The utilization of kinetic and isotherm models in heavy metal sorption is crucial as it provides a theoretical background to understand and predict the removal efficiency of different adsorbent materials. In contrast to previous studies, this research examines a wide range of adsorbent materials, providing a comprehensive understanding of their efficacy in removing heavy metals from wastewater. The study also delves into the theoretical foundations of the isotherm and kinetics models, highlighting their strengths, limitations, and effectiveness in describing the performance of the adsorbents. Moreover, the study sheds light on the regenerability of adsorbents and the potential for their engineering applications. Valuable insights into the state-of-the-art methods for heavy metal wastewater cleanup and the resources required for future developments were discussed. [ABSTRACT FROM AUTHOR]

In this study, activated carbons derived from walnut shells (CA-N) and apple wood (CA-M) were used as adsorbents to remove cobalt(II) and strontium(II) ions from aqueous solutions. The novel materials were obtained using nitric acid (CA-Mox) and nitric acid/urea mixture (CA-Mox-u, CA-Nox-u) as oxidizing agents. The physical–chemical characteristics of activated carbons were determined from nitrogen sorption isotherms, SEM-EDX, FTIR, pH metric titrations, the Boehm titration method and elemental analysis. The results of batch experiments indicate that maximum adsorption can be achieved in broad pH ranges: 4–8 for Co(II) and 4–10 for Sr(II). The maximum adsorption capacities of Co(II) and Sr(II) on oxidized activated carbons at pH = 4 are: CA-Mox, 0.085 and 0.076 mmol/g; CA-Mox-u, 0.056 and 0.041 mmol/g; and CA-Nox-u, 0.041 and 0.034 mmol/g, respectively. The mathematical models (pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models, and Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin–Pyzhev isotherm models) were used to explain the adsorption kinetics, to study the adsorption mechanism and predict maximum adsorption capacity of the adsorbents. The adsorption mechanisms of toxic metal ions on activated carbons were proposed. [ABSTRACT FROM AUTHOR]

Heavy metal contamination in wastewater is a significant concern for human health and the environment, prompting increased efforts to develop efficient and sustainable removal methods. Despite significant efforts in the last few decades, further research initiatives remain vital to comprehensively address the long-term performance and practical scalability of various adsorption methods and adsorbents for heavy metal remediation. This article aims to provide an overview of the mechanisms, kinetics, and applications of diverse adsorbents in remediating heavy metal-contaminated effluents. Physical and chemical processes, including ion exchange, complexation, electrostatic attraction, and surface precipitation, play essential roles in heavy metal adsorption. The kinetics of adsorption, influenced by factors such as contact time, temperature, and concentration, directly impact the rate and effectiveness of metal removal. This review presents an exhaustive analysis of the various adsorbents, categorized as activated carbon, biological adsorbents, agricultural waste-based materials, and nanomaterials, which possess distinct advantages and disadvantages that are linked to their surface area, porosity, surface chemistry, and metal ion concentration. To overcome challenges posed by heavy metal contamination, additional research is necessary to optimize adsorbent performance, explore novel materials, and devise cost-effective and sustainable solutions. This comprehensive overview of adsorption mechanisms, kinetics, and diverse adsorbents lays the foundation for further research and innovation in designing optimized adsorption systems and discovering new materials for sustainable heavy metal remediation in wastewater. [ABSTRACT FROM AUTHOR]

Due to higher levels of industrial activity, the concentrations of toxic substances in natural water bodies are increasing. One of the most dangerous groups of toxic compounds is heavy metals, with even trace amounts of most heavy metals being harmful to aquatic life. This is why purifying water has become an urgent priority. In this context, ion-exchange resins have become more widely used in water treatment processes. However, to reduce the costs and improve the sustainability of this strategy, natural resins are favored over synthetic versions. Therefore, in the present study, a natural tamarind-based chelating resin was developed. The tamarind triazine amino propanoic acid (TTAPA) resin was synthesized and characterized using Fourier-transform infrared spectroscopy, thermogravimetry analysis, scanning electron microscopy, elemental analysis, and physicochemical analysis of the moisture content, total ion-exchange capacity, bulk volume, bulk density, and percentage nitrogen content. The biological oxygen demand and chemical oxygen demand of the industrial effluent before and after treatment were also analyzed. The batch analysis was used to determine the distribution coefficient and percentage removal of the metal ions Fe(II), Zn(II), Pb(II), Cu(II), and Cd(II). The removal efficiency of the prepared TTAPA resin was highest for Fe(II), followed by Cu(II), Zn(II), Pb(II), and Cd(II) in order. The chelating ion-exchange resin also had a metal ion recovery of more than 95%, thus demonstrating great promise for the sequestration of heavy metal ions from industrial wastewater. The proposed TTAPA resin is biodegradable, non-toxic, cost-effective, reproducible, and eco-friendly. [ABSTRACT FROM AUTHOR]

Bentonitic clay and wood sawdust are natural materials widely available in nature at low cost with high heavy metals sorption properties that, in this work, were combined to achieve an effective composite biosorbent with high sorption properties and enhanced mechanical stability. Pine, aspen, and birch wood sawdust, as well as different bentonite clays and different sawdust modification methods (H3PO4 or HCl) were used for preparing new composite biosorbents. A mixture of wood sawdust and bentonite in a ratio of 2:1 was used. All materials were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) methods and tested for Cu and Ni ions removal from water. The adsorption process for all composite biosorbents was well described from a pseudo-second order kinetic model (R2 > 0.9999) with a very high initial adsorption rate of Cu and Ni ions and a maximum uptake recorded within 2 h. The results have shown that the adsorption capacity depends mainly on the kind of wood and the acid treatment of the wood that enhances the adsorption capacity. At a concentration of 50 mg/L, the biosorbent prepared using birch wood sawdust showed the worst performance, removing barely 30% of Cu and Ni ions, while aspen wood sawdust improved the adsorption of Cu (88.6%) and Ni (52.4%) ions. Finally, composite biosorbent with pine wood sawdust showed the best adsorption be haviour with an efficiency removal of 98.2 and 96.3% of Cu and Ni ions, respectively, making it a good candidate as an inexpensive and effective biosorbent for the removal of heavy metals. [ABSTRACT FROM AUTHOR]

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges. [ABSTRACT FROM AUTHOR]

The progress of the textile industry has led to a severe increase in the discharge of colored effluents, polluted with dyes and metal ions (non-biodegradable, carcinogenic to humans and environmental hazards). The implementation of effective methodologies and materials for the treatment of wastewater has become an urgent requirement. The present work describes the application of two samples of mineral materials—Ghidirim diatomite and modified diatomite—as adsorbents for the removal of dyes—Acid Blue 350, Methylene Blue, Basic Red 2—and of metal ions—copper, zinc, and lead—from aqueous solutions. In order to determine the optimal working conditions by which to ensure maximum removal efficiency, the influence of the nature and amount of the sorbent, the initial concentration of pollutant, and the temperature were studied. Working under normal conditions (room temperature, solution pH) efficiencies greater than 80% were obtained for the removal of dyes and metal ions. The adsorption fitted well with the pseudo-second order kinetic model, and the maximum adsorption capacities were determined from the Langmuir isotherm model. The adsorption of investigated pollutants is an endothermic and spontaneous process. The results indicate that Ghidirim diatomite and modified diatomite have potential applications in water purification management, providing high removal efficiency of both dyes and metal ions. [ABSTRACT FROM AUTHOR]