Search Results (210)

This study theoretically investigates the potential of a polyacrylamide copolymerized with amylose, a primary component of starch, to evaluate its efficiency in removing heavy metals from industrial wastewater. This material concept seeks to combine the high adsorption capacity of polyacrylamide with the low cost and biodegradability of starch, ultimately aiming to offer an economical, efficient, and sustainable alternative for wastewater treatment. To this end, a computational model based on density functional theory (DFT) was developed, utilizing the B3LYP functional with the 6-311++G(d,p) basis set, a widely recognized combination that strikes a balance between accuracy and computational cost. The interactions between an acrylamide-amylose (AM/Amy) polymer matrix, as well as the individual polymers (AM and Amy), and the metal ions Pb, Hg, and Cd in their hexahydrated form (M·6H₂O) were analyzed. This modeling approach, where M represents any of these metals, simulates a realistic aqueous environment around the metal ion. Molecular geometries were optimized, and key parameters such as total energy, dipole moment, frontier molecular orbital (HOMO-LUMO) energy levels, and Density of States (DOS) graphs were calculated to characterize the stability and electronic reactivity of the molecules. The results indicate that this proposed copolymer, through its favorable electronic properties, exhibits a high adsorption capacity for metal ions such as Pb and Cd, positioning it as a promising material for environmental applications. Full article

In this study, the presence of heavy metals (HMs) is determined to assess surface water contamination; biosorbent materials are also used to remove them and thus improve their quality. The objective of this work was to study the spatial distribution of HMs in water samples from Tequesquitengo Lake, Morelos, Mexico; pectin was also used for HM biosorption. For this, fifteen water samples were collected from the central and peripheral zones of the lake; HMs such as Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, As, and Hg were identified and quantified by atomic absorption spectroscopy (AAS). The metal evaluation index (HEI) was calculated, as well as the percentage of HM removal with pectin. The water samples presented high concentrations of Pb, Cr, and Mn in contrast to the other HMs studied. Furthermore, these showed high concentrations (161.2, 85.2, and 65.6 µg/L, respectively) in the peripheral zone. Therefore, these values exceed the permissible limit for human consumption, except for Mn. The HEI value indicated that the lake water exhibits low contamination. After the adsorption of HMs with pectin, Cr (100%), Ni (83%) and Cd (37%) were removed, reducing the total concentration of HMs in the water in all samples. Full article

Potentially toxic elements such as cadmium (Cd) in agricultural soils represent a global concern due to their toxicity and potential accumulation in the food chain. However, our understanding of cadmium’s complex sources and the mechanisms controlling its spatial distribution across diverse edaphic and geological contexts remains limited, particularly in underexplored agricultural regions. Our study aimed to assess the total accumulated Cd content in soils under avocado cultivation and its association with edaphic, geochemical, and geomorphological variables. To this end, we considered the total concentrations of other metals and explored their associations to gain a better understanding of Cd’s spatial distribution. We analyzed 26 physicochemical properties, the total concentrations of 22 elements (including heavy and trace metals such as As, Ba, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sr, Tl, V, and Zn and major elements such as Al, Ca, Fe, K, Mg, and Na), and six geospatial variables in 410 soil samples collected from various avocado-growing regions in Peru in order to identity potential associations that could help explain the spatial patterns of Cd. For data analysis, we applied (1) univariate statistics (skewness, kurtosis); (2) multivariate methods such as Spearman correlations and principal component analysis (PCA); (3) spatial modeling using the Geodetector tool; and (4) non-parametric testing (Kruskal–Wallis test with Dunn’s post hoc test). Our results indicated (1) the presence of hotspots with Cd concentrations exceeding 3 mg·kg⁻¹, displaying a leptokurtic distribution (skewness = 7.3); (2) dominant accumulation mechanisms involving co-adsorption and cation competition (Na⁺, Ca²⁺), as well as geogenic co-accumulation with Zn and Pb; and (3) significantly higher Cd concentrations in Leptosols derived from Cretaceous intermediate igneous rocks (diorites/tonalites), averaging 1.33 mg kg⁻¹ compared to 0.20 mg·kg⁻¹ in alluvial soils (p < 0.0001). The factors with the greatest explanatory power (q > 15%, Geodetector) were the Zn content, parent material, geological age, and soil taxonomic classification. These findings provide edaphogenetic insights that can inform soil cadmium (Cd) management strategies, including recommendations to avoid establishing new plantations in areas with a high risk of Cd accumulation. Such approaches can enhance the efficiency of mitigation programs and reduce the risks to export markets. Full article

In this study, kaolinite-based clay (Ka-Clay) was used as an adsorbent for the efficient removal of Pb(II), Cd(II) and Hg(II) ions from aqueous media. The selection of Pb(II), Cd(II) and Hg(II) ions for experimental studies took into account their high toxicity, while the choice of Ka-Clay, the ease of preparation and high availability of this material were the most important arguments. Ka-Clay exhibits high adsorption performance, with removal percents over 98% for Pb(II) and 93% for Cd(II), even at high concentrations of metal ions (over 150 mg/L, pH = 6.5, 4 g adsorbent/L, 21 ± 1 °C). For Hg(II) ions, the adsorption percent does not exceed 55%, and this moderate value is mainly due to the significant change in pH. The adsorption behavior was in accordance with the Langmuir model (R² > 0.95) and the pseudo-second order kinetic model (R² > 0.99), indicating an adsorption process that occurs mainly through chemical interactions at the adsorbent surface between the metal ions and the functional groups. Adsorption processes are spontaneous (ΔG = −8.66 ÷ −15.76 kJ/mol) and endothermic (ΔH = 7.09 ÷ 21.81 kJ/mol), and the adsorption mechanism is the results of elementary processes of electrostatic attraction, ion exchange and superficial complexation. The insignificant effect of other ions (Ca(II), Mg(II), Na(I), K(I)) present in real wastewater samples as well as the desorption behavior of exhausted adsorbent highlight the practical utility of this adsorbent on a large scale. The experimental results included in this study suggest that Ka-Clay can be used as a promising adsorbent for the removal of high concentrations of toxic heavy metals with low cost and high efficiency, and this can contribute to the design of a sustainable wastewater treatment method. Full article

Radionuclides and heavy metals pose potential risks to marine ecosystems and human health. Daya Bay, the site of China’s first commercial nuclear power plant, has experienced significant anthropogenic impacts, yet the extent of radionuclide and heavy metal contamination remains unclear. Nineteen surface sediment samples were collected in January 2024 and analyzed for natural (²¹⁰Pb, ²²⁸Th, ²²⁶Ra, ²²⁸Ra, and ⁴⁰K) and anthropogenic (¹³⁷Cs) radionuclides, heavy metals (Cu, Pb, Zn, Cd, Cr, Mn, Hg, and As), grain size, and total organic carbon (TOC). The surface sediments of Daya Bay were predominantly fine-grained, with TOC levels ranging from 0.41% to 1.83%, influenced significantly by riverine input from the Dan’ao River. Natural radionuclides exhibited distinct spatial patterns: ²¹⁰Pb and ²²⁸Th activity levels were higher in fine-grained sediments, and correlated with TOC, indicating adsorption and sedimentation controls. In contrast, anthropogenic ¹³⁷Cs activity was low and showed no significant impact from the nuclear power plant. Notably, the absence in the samples of key anthropogenic radionuclides typically associated with nuclear power plant operations further confirmed the negligible impact of the power plant on local sediment contamination. The results indicated that the baseline levels of both natural and anthropogenic radionuclides and heavy metals were predominantly influenced by natural processes and local anthropogenic activities rather than the operation of the nuclear power plant. This study establishes critical baselines for radioactivity and heavy metals in Daya Bay, underscoring effective pollution control measures and the resilience of local ecosystems despite anthropogenic pressures. Full article

Hierarchical porous N-doped carbon spheres featuring a combination of micropores, mesopores and macropores as well as tuneable properties were synthesised using dopamine as a carbon precursor and triblock copolymers (F127, P123 and F127/P123 composites) as templates via direct polymerisation-induced self-assembly. The structures and textures of these materials were characterised using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N₂ adsorption–desorption isotherm analysis, Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The sample synthesised at an F127:P123 molar ratio of 1:3 (NCS-FP3) exhibited the highest surface area (463 m²/g) and pore volume (0.27 cm³/g). The hydrophobic/hydrophilic molar ratios of the templates were adjusted to control the morphology of the corresponding micelles and hence the porous structures and morphologies of the carbon spheres, which exhibited high CO₂ capture capacities (2.90–3.46 mmol/g at 273 K and 760 mmHg) because of their developed microporous structures and N doping. Additionally, NCS-FP3 exhibited an outstanding electrochemical performance, achieving a high specific capacitance (328.3 F/g at a current density of 0.5 A/g) and outstanding cycling stability (99.2% capacitance retention after 10,000 cycles). These high CO₂ capture and electrochemical performances were ascribed to the beneficial effects of pore structures and surface chemistry features. Full article

Zero-valent iron (ZVI), particularly in its nanoscale form (nZVI), is now considered a highly promising material for the remediation of toxic metal ions from polluted groundwater owing to its strong reductive potential, significant surface area, and reactive behavior. This review systematically explores the application of pristine and modified ZVI systems—including doped ZVI, bio-stabilized composites, and ZVI supported on advanced materials like MXene and nanocellulose—for effective treatment of water containing metal species like As(III/V), Hg(II), Cr(VI), and Ni(II). Emphasis is placed on understanding the underlying mechanisms, including redox reactions, surface complexation, and synergistic adsorption–reduction pathways. Key factors affecting adsorption efficiency—such as pH, temperature, ZVI dosage, and competing ions—are thoroughly analyzed, alongside adsorption kinetics and isotherm models. Modified ZVI composites exhibit enhanced stability, selectivity, and reusability, demonstrating promising performance even in complex aqueous environments. Despite significant progress, challenges such as nanoparticle passivation, limited field-scale data, and potential toxicity of byproducts remain. The review concludes by highlighting future research directions focused on improving material longevity, regeneration efficiency, selective adsorption, and integration with other advanced remediation technologies for sustainable and scalable groundwater treatment. Full article

Heavy metal and pesticide contaminations represent significant environmental and health hazards to humans and animals. Toxic heavy metals such as lead (Pb), cadmium (Cd), mercury (Hg), and copper (Cu) persist in the environment, bioaccumulating in beverages and food products from both natural and anthropogenic sources. Traditional remediation techniques, such as chemical precipitation and ion exchange, are effective but often costly and challenging to apply at a large scale. In recent years, grape pomace—a winemaking by-product rich in bioactive compounds—has emerged as a promising, low-cost biosorbent for the removal of such pollutants. Its high adsorption capacity, environmental friendliness, and availability make it a strong candidate for water and food decontamination processes. This study evaluates grape pomace and its biochar as sustainable biosorbents for heavy metal removal from water and soil, examining their adsorption efficiency, adsorption mechanisms, environmental benefits, advantages, limitations, and perspectives for future industrial-scale applications. Full article

Heavy metal pollution severely affects soil and rice quality in China. In a one-year field experiment conducted in Hg-Cd co-contaminated farmland in Tongren, Guizhou, we examined the effects of low-accumulation rice cultivars, soil amendments (Fupei (D1), Wansan (D2), Shengwujun (D3), and Shigou (D4)) and foliar barrier agents on Hg and Cd transport and uptake. The rice cultivar Longliangyouhuanglizhan (P1) showed lower Hg and Cd accumulation. When combined with amendments, P1 further reduced health risks. All amendments effectively reduced non-carcinogenic health risks, with Fupei reducing Hg and Cd accumulation in rice by 65.16% and 97.54%, respectively, achieving a 91.74% reduction in health risks. Foliar barrier agents further decreased heavy metal content in rice. Additionally, D1 was the most cost-effective option. Soil assessments showed amendments reduced available Hg content by 66.67–70.51%, while Cd content increased by 3.51–16.67%. Mechanistic analysis indicated that D1 and D2 mainly immobilized heavy metals through adsorption and precipitation, while D3 facilitated removal via microbial reduction, and D4 relied on adsorption. Overall, D1 was most effective in mitigating heavy metal risks and improving soil quality, providing a comprehensive strategy for managing contamination in rice production with important implications for food safety and sustainable agriculture. Full article

Mercury contamination in groundwater seriously affects human health and ecosystem security. The remediation of Hg-contaminated groundwater remains a challenging task. The applicability of an as-synthesized supramolecular polymer (SP) for low-concentration mercury in a high-salinity groundwater matrix has been verified through a batch process and column test. The remediation of mercury-contaminated groundwater, particularly in complex high-salinity environments, represents a significant and enduring challenge in environmental science. The batch test study demonstrated that the SP can efficiently adsorb Hg from groundwater with superior selectivity and a high uptake capacity (up to 926.1 ± 165.3 mg g⁻¹). Increasing the pH and dissolved organic matter (DOM) and reducing the ionic strength can facilitate Hg adsorption; the coexistence of heavy metal ions slightly weakens the removal. In terms of its performance as a permeable reactive barrier, the SP can intercept Hg in flowing groundwater with a capacity of up to 3187 mg g⁻¹. A low influent mercury concentration, low pore velocity, and high SP dosage can effectively extend the breakthrough time in column tests. Additionally, the Yan model (R² = 0.960−0.989) can accurately depict the whole dynamic interception process (150 PVs) of SPs in a fixed column, and the Adams–Bohart model (R² = 0.916−0.964) describes the initial stage (≤35 PVs) well. Considering the functional group in the SP and the Hg species in groundwater, complexation, electrostatic attraction, ion exchange, and precipitation/co-precipitation are the plausible mechanisms for mercury removal based on the characterization results of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrometer (FT-IR). These impressive features render the SP a promising candidate for the remediation of trace Hg in saline groundwater using permeable reactive barrier (PRB) technology. Full article

Chitosan (CS) and polyvinyl alcohol (PVA) nanofiber membranes were synthesized via electrospinning and used as supporting materials for powdered porous organic polymer (POP). These membranes were then crosslinked with glutaraldehyde, resulting in nanofiber membranes (CS/PVA/POP) as an efficient adsorbent for Hg(II) ions. Characterization using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy showed that the membranes effectively removed up to 92.9% of mercury ions at optimal conditions, with an adsorption capacity of 116.1 mg/g. The adsorption data fit well with the Langmuir isotherm and pseudo-second-order kinetic models. The efficient uptake of mercury ions was attributed to chemisorption involving active groups (C=S, -NH₂, -OH), facilitated by mechanisms such as chelation, complexation, or electron exchange. The CS/PVA/POP nanofiber membranes demonstrated significant advantages in adsorption capacity, economic viability, and recyclability, providing an effective solution to mercury pollution in water. Full article

The conventional manganese carbonate preparation process faces challenges such as low resource utilization efficiency and difficulties in treating by-product Mg-containing ammonium sulfate solution. In this study, a two-stage leaching process was developed to efficiently extract Mn and Mg from the ore. NH₄HCO₃ was used as a precipitant to convert Mn²⁺ in the leachate to MnCO₃, achieving a Mn precipitation efficiency of 99.89%, and the resulting product contained 44.45% Mn, meeting the first-class product indicators of HG/T 4203-2011 (Chinese standard on manganese carbonate for industrial use). To further enhance resource utilization, a combined stripping–adsorption process was designed to treat the Mg-containing ammonium sulfate solution generated during the carbonization process. Subsequently, the economically valuable gypsum and magnesium oxide products were prepared. Additionally, 88.20% of the NH₃ in the solution was stripped and recycled to prepare NH₄HCO₃ and then used during carbonization. Finally, a purified solution free of ammonia nitrogen was obtained using 001×7 resin to dynamically adsorb the filtrates obtained during the stripping process, and the maximum adsorption capacity of resin for ammonia nitrogen was 51.14 mg/g. This process provides a novel approach to achieving clean production in the manganese carbonate production industry. Full article

The anion-complexation mechanism and anion-adsorption capacity of a hybrid material based on hyperbranched polyethyleneimine (HBPEI) covalently bonded onto an activated carbon (AC) is presented. The anion-scavenger behavior of this hybrid material toward CrO₄²⁻, PO₄³⁻, AsO₄³⁻ and HgCl₄²⁻ was explored by direct potentiometric and adsorption measurements, which revealed a novel approach to predict the interactions between the supported polymeric complexing units and the different anions. The results were analyzed by considering the reactivity data of the HBPEI/anion (HBPEI free in solution) and AC-HBPEI/anion systems. The results corroborated that the AC-HBPEI hybrid material is an excellent anion-complexing material, whose anion adsorption ability is defined by the complexing properties of the HBPEI molecules toward the anions. This assessment provides a straightforward tool to determine the type and strength of the interactions involved in supported polymer-based/anion systems, which can provide valuable information for predicting and designing efficient energy and scavenger materials. Full article

The temperature at which pollutants are treated varies across different industrial processes. To address the high cost of raw materials for MOFs and the low efficiency of Hg⁰ removal in low-temperature environments, a series of MIL-101(Cr)-derived carbon matrix composite materials were prepared by combining MIL-101(Cr) with biomass and multiple metals. These materials were synthesized through a sol-gel method followed by carbonization. This study investigates the effects of composite ratios and adsorption temperatures on Hg⁰ removal, utilizing XRD, BET, and other characterization techniques to elucidate the mercury-removal mechanism of the PDC-MIL composite materials. The results indicate that MIL101(Cr) significantly influences the formation of the gel skeleton. When the composite ratio of MIL-101(Cr) to biomass is 1:1, the material exhibits an optimal pore structure, leading to high Hg⁰ removal efficiency over a wide temperature range. The removal of Hg⁰ by these composite materials involves both physical adsorption and chemisorption. Low temperatures favor physical adsorption, while high temperatures promote chemisorption. The sol-gel composite method facilitates cross-linking polymerization between MOFs and SiO₂, enabling better pore structure connectivity with biomass and MOFs, thereby optimizing the poor pore structure observed after pyrolysis. Consequently, the improved pore structure enhances physical adsorption at low temperatures, mitigates desorption at high temperatures, and increases the contact probability of Hg⁰ with active sites within the pores, significantly improving the mercury-removal ability of the material across a broad temperature range. Full article

To propel the development of a robust methylmercury immobilisation technology, CH₃Hg⁺ adsorption on montmorillonite surfaces was simulated herein using density functional theory. This study involved a thorough molecular-level analysis, including factors such as electron potential energy, molecular orbital configurations, stable adsorption configurations, adsorption energies, charge distributions, and density of states. The principal findings are summarised as follows: (1) CH₃Hg⁺ adsorption on the (001) surface was characterised by an adsorption energy ranging from −27 to −51.7 kJ/mol. In this case, Hg was attracted to the involved silicon–oxygen ring cavities. Meanwhile, on the (010) surface, CH₃Hg⁺ exhibited an adsorption energy ranging between −119.4 and −154.3 kJ/mol. In this case, Hg was attracted to hydroxyl groups such as ≡Al(OH)(OH₂) and ≡Si(OH), forming a covalent bond with the oxygen atom of these groups. (2) Comparative analysis revealed that the adsorption energy of CH₃Hg⁺ on the (010) surface surpassed that on the (001) surface. On the (001) surface, electrostatic interactions were the predominant factor influencing adsorption, while on the (010) surface, electrostatic and covalent bonding interactions were important. Notably, the strength of electrostatic interactions was greater on the (001) surface than on the (010) surface. (3) The formation of covalent bonds between CH₃Hg⁺ and the (010) surface was primarily attributed to the overlap of electron cloud between Hg and surface O atoms. In particular, the interaction between the s orbital of Hg and the p orbital of O facilitated the formation of a σ bond. Overall, these findings provide a theoretical framework for the advancement of efficient in situ immobilisation technologies for methylmercury. Full article