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Graphene-based nanomaterials have been proved to be robust sorbents for efficient removal of environmental contaminants including arsenic (As). Biobased graphene oxide (bGO-P) derived from sugarcane bagasse via pyrolysis, GO-C via chemical exfoliation, and magnetite nanoparticles (FeNPs) via green approach using Azadirachta indica leaf extract were synthesized and characterized by Ultraviolet-Visible Spectrophotometer (UV-vis.), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), mean particle size and Scanning electron microscopy (SEM) along with Energy dispersive spectroscopy (EDX) analysis. Compared to cellulose and hemicellulose, the lignin fraction was less in the precursor material. The GOC, bGO-P and FeNPs displayed maximum absorption at 230, 236, and 374 nm, respectively. FTIR spectrum showed different functional groups (C-OH, C-O-C, COOH and O-H) modifying the surfaces of synthesized materials. Graphene based nanomaterials showed clustered dense flakes of GO-C and thin transparent flakes of bGO-P. Elemental composition by EDX analysis of GO-C (71.26% C and 27.36% O), bGO-P (74.54% C and 24.61% O) and FeNPs (55.61% Fe, 4.1% C and 35.72% O) confirmed the presence of carbon, oxygen, and iron in synthesized nanomaterials. Sorption study was conducted with soil amended with different doses of synthesized nanomaterials (10, 50 and 250 mg) and exposed to 100, 300 and 500 ppm of As. Arsenic concentrations were estimated by colorimetry and atomic absorption spectroscopy (AAS). GO-C, bGO-P, and FeNPs showed substantial As removal efficiency i.e., 81 to 99.3%, 65 to 98.8% and 73.1–89.9%, respectively. Green synthesis of bGO-P and magnetite nanoparticles removed substantial amounts of As compared to GO-C and can be effectively deployed for As removal or immobilization. Higher and medium sorbent doses (250 and 50 mg) exhibited greater As removal and data was best fitted for Freundlich isotherm evidencing favorable sorption. Nevertheless, at low sorbent doses, data was best fitted for both models. Newly synthesized nanomaterials emerged as promising materials for As removal strategy for soil nano-remediation and can be effectively deployed in As contaminated soils. [ABSTRACT FROM AUTHOR]

Adsorptive nanofiber electrospun membranes (ANEMs) show promise for heavy metal removal, particularly in dilute solutions. Nanofibrous polyacrylonitrile (PAN) membranes incorporating Cloisite 20A (C20) organoclay were fabricated via electrospinning for As(V) removal. The impact of C20 on structural properties and As(V) removal efficiency of the nanofiber membranes was investigated. The results indicated that the PAN‐C20 membranes morphology was uniform, with fiber diameters mostly falling within the 100–300 nm range. Incorporation of C20, especially in an exfoliated structure, led to increased hydrophilicity, mechanical strength, and roughness of the membranes. Batch adsorption results revealed that the adding C20 up to 1.5 wt.% significantly enhanced adsorption capacity due to the higher concentration and proper C20 dispersion. Dynamic filtration showed that the PAN‐C20(1.0) membrane achieved over 90% As(V) removal efficiency for 960 min and demonstrated excellent regeneration ability. Highlights: Cloisite 20A organoclay was incorporated into PAN by electrospinning to prepare adsorptive membrane.Adsorptive membranes were used for As(V) removal from water.Type of Cloisite 20A dispersion in PAN in dynamic filtration was more important than in static adsorptionPAN‐C20‐1.0 with exfoliated structure showed higher removal efficiency than PAN‐C20‐1.0 with intercalated structure.PAN‐C20‐1.0 membrane was usable for multiple adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

During coal combustion, the harmful element arsenic can be released into environment and cause potential significant harm to human beings. Therefore, it is very important to study the removal of arsenic from coal before combustion. In this work, simulated SO2-containing flue gas was used to leach arsenic from coal in a 1 L UV photoreactor. The effects of FeCl3, ultraviolet (UV), pH and the Cl−/Fe3+ molar ratio on arsenic leaching and SO2 removal were experimentally investigated and the enhancing mechanism was analysed. Experimental results demonstrated that FeCl3 and UV could efficiently increase iron and arsenic leaching percentages and SO2 removal efficiency. UV irradiation could induce the oxidation of most trivalent arsenic. The arsenic leaching percentage was significantly larger than that of iron. Low pH was favourable for iron and arsenic leaching. The optimal Cl−/Fe3+ molar ratio was determined to be 3:1. The introduced ferric chloride could not only increase the concentrations of free radicals and ferric iron oxidants, the chloride ion might also impede the formation of passive coatings, thus increasing the arsenic leaching percentage, intensifying the oxidation of trivalent arsenic and enhancing the removal of SO2. [ABSTRACT FROM AUTHOR]

The removal of arsenic compounds from water is classified as an urgent concern by the World Health Organization, since many of these species are hazardous to human health. However, the conventional water treatments are not able to extract them, which makes the development of new methodologies of arsenic removal noteworthy. The application of metal‐organic frameworks (MOFs) as adsorbents to attend this purpose is very promising, because these materials can be intelligently built for the desired application. In this work, the performance of common subunits usually found in MOFs were individually evaluated for the adsorption of some arsenic species through computer simulations based on density functional theory (DFT). Thus, important information at molecular level was obtained, which can assist the design of an optimized adsorbent. Three factors were identified to strengthen the adsorption: ionic coordinate bond, hydrogen bonds, and cycle formation. Furthermore, the evaluated subunits showed to be proper for the removal of HAsO2, once the change in the Gibbs free energy was up to −30.8 kcal mol−1. The comparison with possible coexistent species showed that Cl−, HSO4−${\mathrm{HSO}}_4^ - $, and H2PO4−${\mathrm {H}}_2 {\mathrm{PO}}_4^ - $ can interfere with adsorptive process depending on the MOF composition and on the arsenic species to be removed from water. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Extractive Metallurgy) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Graphene-based nanomaterials have been proved to be robust sorbents for efficient removal of environmental contaminants including arsenic (As). Biobased graphene oxide (bGO-P) derived from sugarcane bagasse via pyrolysis, GO-C via chemical exfoliation, and magnetite nanoparticles (FeNPs) via green approach using Azadirachta indica leaf extract were synthesized and characterized by Ultraviolet-Visible Spectrophotometer (UV-vis.), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), mean particle size and Scanning electron microscopy (SEM) along with Energy dispersive spectroscopy (EDX) analysis. Compared to cellulose and hemicellulose, the lignin fraction was less in the precursor material. The GOC, bGO-P and FeNPs displayed maximum absorption at 230, 236, and 374 nm, respectively. FTIR spectrum showed different functional groups (C-OH, C-O-C, COOH and O-H) modifying the surfaces of synthesized materials. Graphene based nanomaterials showed clustered dense flakes of GO-C and thin transparent flakes of bGO-P. Elemental composition by EDX analysis of GO-C (71.26% C and 27.36% O), bGO-P (74.54% C and 24.61% O) and FeNPs (55.61% Fe, 4.1% C and 35.72% O) confirmed the presence of carbon, oxygen, and iron in synthesized nanomaterials. Sorption study was conducted with soil amended with different doses of synthesized nanomaterials (10, 50 and 250 mg) and exposed to 100, 300 and 500 ppm of As. Arsenic concentrations were estimated by colorimetry and atomic absorption spectroscopy (AAS). GO-C, bGO-P, and FeNPs showed substantial As removal efficiency i.e., 81 to 99.3%, 65 to 98.8% and 73.1–89.9%, respectively. Green synthesis of bGO-P and magnetite nanoparticles removed substantial amounts of As compared to GO-C and can be effectively deployed for As removal or immobilization. Higher and medium sorbent doses (250 and 50 mg) exhibited greater As removal and data was best fitted for Freundlich isotherm evidencing favorable sorption. Nevertheless, at low sorbent doses, data was best fitted for both models. Newly synthesized nanomaterials emerged as promising materials for As removal strategy for soil nano-remediation and can be effectively deployed in As contaminated soils.

AbstractThe study provides significant advances in the production and evaluation of biochar (BC) and activated carbon (AC) through the use of different precursors and conditions. It has been shown how the pore size distribution, surface area, and chemical functional groups of various materials affect their capacity to adsorb arsenic (As). Nanoporous carbonaceous materials (nP-CMs) have become the focus of great attention from researchers due to their excellent porous properties. These materials are expected to be used in a variety of new industrial applications that utilize ordered nanospace structures. They have excellent physicochemical properties and are inexpensive and environmentally friendly (low density, low thermal conductivity, nanoporous with large surface area, three-dimensional network structure, etc.). Numerous studies have examined the use of nP-CMs as an adsorbent in the removal of As by improving properties including biocompatibility, stability, charge density, functionality, surface area, etc. An extensive summary of the removal of As(III) and As(V) using nano BC/AC made from different plant wastes was included in this paper. The potential interaction processes between As and nP-CMs were addressed. nBC/AC modified with different metals or metal oxides are one of the most often used modifiers for As removal. The potential of nanoporous BC and AC to remove As from aquatic environments is discussed, which has been carefully analyzed in both recent and earlier findings. This review article emphasizes how critical it is to support research initiatives, increase public awareness, and encourage interdisciplinary cooperation in order to solve the environmental concerns related to As. [ABSTRACT FROM AUTHOR]

Copper smelting flue dust (CFD) is a byproduct of pyrometallurgical copper production, containing valuable metals like lead, zinc, and copper, but also hazardous arsenic, which complicates its handling and recycling. Traditional methods for arsenic removal from CFD, such as pyrometallurgical and hydrometallurgical processes, are often inefficient or result in the loss of valuable metals. This study explores the efficacy of ultrasound-assisted leaching for selective arsenic extraction from CFD, offering a potentially more efficient and environmentally friendly alternative. We employed a combination of sodium hydroxide and sodium sulfide in an aqueous solution, enhanced by ultrasonic waves, to selectively recover arsenic into solution. The optimal leaching conditions were determined to be 0.4 M NaOH, 0.2 M Na2S, a liquid-to-solid ratio of 50 mL/g, a temperature of 80 °C, an ultrasound power of 150 W, and an ultrasound frequency of 100 kHz, under which up to 99% of arsenic was extracted within 45 min. The kinetic analysis conducted suggests that the leaching process is controlled by the chemical reactions occurring at the surface of the particles. [ABSTRACT FROM AUTHOR]

A pyro-hydrometallurgical process is proposed in this study for the selective arsenic removal and the Pb and Sb recovery from lead softening slag, which incorporates NaOH roasting followed by water leaching, carbothermic reduction, and HNO3 leaching as process steps. Lead softening slag, containing 63.9 wt% Pb, 17.7 wt% Sb, and 4.4 wt% As, is first roasted with NaOH at 400°C, followed by water leaching at room temperature. The effect of the roasting temperature and NaOH dosage is investigated with regard to the removal yield of As, Pb, and Sb. The arsenic-free slag is reduced with carbon for Pb recovery as the antimonial lead. The reduction temperature and carbon dosage are optimized by applying FactSage modeling and performing experimental tests for selective Pb recovery. The residual slag is leached with HNO3 solution for the further removal of Pb and enrichment of Sb. The chemical and phase composition of the final leaching residue is determined to assess the possibility of using it as a feedstock for antimony trioxide production. The proposed process flowsheet enables the recovery of Pb and Sb as antimonial lead and antimony trioxide, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] Remediation of arsenic contamination is of great importance given the high toxicity and easy mobility of arsenic species in water and soil. This work reports a new and stable adsorbent for efficient elimination of arsenic by coating polyethyleneimine (PEI) molecules onto the surface of iron-doped birnessite (Fe-Bir). Characterization results of surface microstructure and crystalline feature (scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS), etc.) suggest that Fe-Bir/PEI possesses a fine particle structure, inhibiting the agglomeration of birnessite-typed MnO 2 and offering abundant active sites for arsenic adsorption. Fe-Bir/PEI is capable of working in a wide pH range from 3 to 11, with an efficient removal capacity of 53.86 mg/g at initial pH (pH 0) of 7. Meanwhile, commonly coexisting anions (NO3−, SO 4 2−, and Cl−) and cations (Na+, K+, Ca2+ and Mg2+) pose no effect on the arsenic removal performance of Bir/PEI. Fe-Bir/PEI exhibits a good reusability for arsenic removal with low Mn and Fe ions leaching after 5 cycles. Besides, Fe-Bir/PEI possesses efficient remediation capability in simulated As-contaminated soil. The modification of PEI in Fe-Bir/PEI can adsorb newly formed As(V), which is impossible for the adsorbent without PEI. Further, the arsenic removal mechanism of Fe-Bir/PEI is revealed with redox effect, electrostatic attraction and hydrogen bonding. [ABSTRACT FROM AUTHOR]

Arsenic contamination in water poses a significant global health threat, necessitating urgent and comprehensive measures to address this pervasive issue. This research investigates the efficacy of a novel microwave-assisted bionanomaterial derived from Calotropis procera stem, an abundant and eco-friendly adsorbent, for removing arsenite ions from aqueous solutions. Surface properties of Bionanomaterial was Characterised using Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis revealed a significant increase in surface area (578 m2/g) after high-energy ball milling, with SEM images showing an uneven surface with enlarged holes. Optimal arsenite removal was achieved at pH 5, a contact time of 90 min, an adsorbent dosage of 4 g, an initial arsenite concentration of 30 ppm, and a temperature of 60 °C. The zeta potential analysis indicated a shift in the isoelectric point from pH 6.2 to pH 5.0, reflecting effective adsorption and surface charge modification. Thermodynamic parameters suggested that adsorption is endothermic and spontaneous, with the Freundlich isotherm model providing the best fit for the adsorption data. Kinetic studies revealed that the process is governed by rapid external diffusion, intraparticle diffusion, and surface chemisorption, consistent with pseudo-second-order kinetics. These findings highlight the bionanomaterial’s potential as a viable adsorbent for arsenic removal from aqueous solutions.

In recent years, porous ceramics have been widely studied because of their excellent technological properties. The intrinsic technological characteristics depend on the forming process and the application for which the materials are intended. A clay raw material (75 mass%) which is rich in melting oxides and waste peanut shells (25 mass%) were used to manufacture porous ceramics for the removal of arsenic from borehole water in Burkina Faso. A borehole water analysis shows a concentration of arsernic of 39 μg L−1 above the WHO standard. The porous ceramics were obtained from samples shaped by unidirectionnal pressing and after sintering at 900 °C (MKOR9) or 1100 °C (MKOR11). Unlike MKOR9 materials, MKOR11 materials consist of 27 % mullite phases. MKOR9 and MKOR11 porous materials presented a diametrical compression stress to rupture greater than 0.15 MPa, as recommended in the literature for ceramic filters. The obtained permeability value of MKOR11 ceramic materials (53,802 L/h.m2.bar) is much higher than that of MKOR9 (18596 L/h m2 bar), although its open porosity (61 %) is lower than that of MKOR9 materials (65 %). The removal rate obtained with MKOR9 is 24 % compared to 95 % for MKOR11. MKOR11 filters almost completely reduce arsenic concentration below the WHO limit values, which is not the case for MKOR9 materials. The adsorption kinetics and thermodynamic parameters showed that the adsorption process is the chemisorption. This work has shown that MKOR11 ceramic filters have a very impressive effectiveness, and they could be manufactured for the benefit of the remote population.

The aim of this study is the synthesis of nanoparticles with selective arsenic recognition capability for the removal of arsenic from water. Arsenic recognition based molecularly imprinted (As(V)-MIP) were synthesized using the molecular imprinting technique via mini-emulsion polymerization. The synthesized As(V)-MIP nanoparticles were characterized using zeta sizer, zeta potential, FTIR, Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and elemental analysis. The adsorption behavior of nanoparticles was investigated in a batch system at pH 4.0–9.0. The maximum adsorption capacity of As(V)-MIP nanoparticles was determined to be 54.29 mg As/g polymer at pH 5.0. Various parameters such as pH, concentration and adsorption time were examined to determine the optimum adsorption conditions. As(V)-MIP nanoparticle selectivity experiments were conducted in the presence of NO3−, PO43−, and SO42− anions to determine the relative selectivity coefficients (K'). The experimental data showed a good correlation with the Langmuir isotherm equation and adherence of the adsorption process to pseudo-second-order kinetics was observed. Applying As(V)-MIP nanoparticles to real water sample showed up to 95.3% As(V) removal efficiency. Reusability experiments were performed by renewal of nanoparticles using a 1 M HNO3 solution containing 0.05% thiourea. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effective treatment of wastewater generated from households, communities, and industries is vital for preserving our environment. Chemical treatment, which involves adding coagulant chemicals directly into the wastewater, is the most popular treatment method. However, due to its high operating costs and the issue of secondary contamination, there is a need for an effective method to address these issues. In this study, we investigated the electrocoagulation (EC) system, which is currently undergoing a revival in research due to its promising features, such as low system and operating costs and its environmentally friendly process. We developed two-dimensional unsteady mathematical models supported by Langmuir isotherm theory to elucidate the underlying physics of the aluminum-based EC process and to understand key control parameters. The developed model was used to analyze the effects of EC cell geometry and operating conditions on the local distribution of intermediate ionic species and their impact on the adsorption behaviors of EC-generated coagulants on arsenic pollutants in the wastewater for the first time. It was found that a higher removal rate was achieved as the EC treatment time and current intensity increased, while the cell gap and inflow rate decreased. Applying the current-off condition during the EC process was found to be an efficient method for increasing the removal rate with less consumption of electrical energy. [ABSTRACT FROM AUTHOR]

Dusts from furnaces for pyrometallurgical refining of copper (Cu) in which arsenic (As) was pre-removed through the use of vacuum carbothermal reduction methods could be used as raw materials. After treating the As pre-removed dusts through oxidative leaching using waste acids, the process of neutralizing and precipitating As and iron (Fe) in the leaching solution was investigated, as well as the precipitation and stabilization process of As and Fe residues. The results show that the leaching rate of Cu, Zn, and As from such dusts can reach 98.98%, 97.46%, and 95.22%, respectively, after leaching operation with waste acids under a liquid–solid ratio of 8:1, a leaching temperature of 80°C, an airflow rate of 300 ml/min, and a leaching time of 120 min. When the molar ratio of Fe to As (n(Fe)/n(As)) is 1.50 in the solution after advanced oxidization, and the final pH value of neutralization is 2.0, the precipitation rate of As and Cu in the residues as ferric arsenates is 93.65% and 2.2%, respectively. As and Fe are neutralized and precipitated, which allows Cu to enter the solution, while As enters the residues. After being transformed, the unstable As and Fe residues can be stockpiled as nontoxic, stable waste. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we synthesized La-incorporated O-rich defective MoS2 nanosheets by a simple, inexpensive, in situ hydrothermal reaction to self-exfoliate the bulky MoS2 layers themselves so that they can readily trap hard base anions, arsenic (arsenite and arsenate), from water. Attempting to modify MoS2 surfaces by incorporating O allows for more active sites, which is confirmed by powder XRD patterns where the exfoliated layers have a d-spacing of 0.63 nm, while the spacing for the bulky layers is 0.60 nm. The substitution of La at different equivalent ratios on the interlayer/surface improves the adsorption properties of arsenite and arsenate in simple solutions, as shown by the Langmuir adsorption density values of 0.7760 and 1.4363 mmol g–1, respectively. When the O-rich MoS2 layers were loaded with La, the adsorption densities improved, with La1.0 equiv showing the best values among the materials studied. The presence of O and S was more responsible for the removal of arsenite ions, and La and O, together with a small amount of N, were able to remove arsenate ions from water according to the well-known Pearson's Lewis acid−base principle. The stability of the materials was characterized after the experiments, and it was found that there was no leaching of the materials by ICP-OES and the stability was maintained after 6 regeneration cycles. With the exception of phosphate, which behaves chemically similar to arsenic, the adsorption densities were not significantly affected by the mono- and divalent anions, indicating the selectivity of the prepared materials. The synthesis cost of MoOxS2–x was 2 times lower than that of bulky MoS2, and its adsorption properties were 10 times higher than those of the latter. The results suggest that La-substituted O-rich MoS2 is a potential candidate for the removal of soft and hard base metals from water. [ABSTRACT FROM AUTHOR]

This research introduces an enhanced limonite‐based composite fiber adsorbent for arsenic (As) removal. The modification involves creating polyethersulfone (PES)–limonite composite fibers loaded with 60 wt% limonite powders, designed to be applicable in water flow environments. The fibers were prepared using a wet‐spinning process based on phase inversion, with varying concentrations (10, 20, and 30 wt%) of PES in NMP solution. The composite fiber with 10 wt% NMP exhibited a porous structure and demonstrated efficient absorption of both As(III) and As(V). Adsorption followed the Langmuir model, with qm values of 1.5 mg/g for As(III) and 3.2 mg/g for As(V) at pH 6. In column experiments, As removal rates increased with contact time, attributed to decreased flow rates (1 mL/min). Moreover, increasing fiber column height led to enhanced removal rates, as indicated by the Adams–Bohart model. The mechanism for As(V) removal involved the formation of an inner‐sphere complex through ion exchange between α‐FeOOH and HAsO4− and H2AsO42− in an aqueous solution at pH 6.8. Practitioner Points: Changing the polyethersulfone ratio in the composite leads to variations in the appearance of limonite within each composite fiber.Limonite composite fibers effectively remove As(III) and As(V) at neutral pH.The adsorption behavior follows Langmuir kinetic model, the qm of 1.5 mg/g for As(III) and 3.2 mg/g for As(V).Longer columns and contact times enhance arsenic (As) removal in practical water treatment systems.Adam–Bohart model aids in predicting breakthrough and saturation time in As adsorption column design. [ABSTRACT FROM AUTHOR]

While the worldwide distribution of geogenic arsenic (As)-affected groundwater is highly overlapped with the areas with abundant groundwater, utilization of As-contained groundwater is an inevitable compromise in those areas where surface water is not enough for irrigation. Since the occurrence of As in groundwater is often accompanied by high iron (Fe) contents, the facilitation of As and Fe precipitation without adding additional oxidizers and adsorbents is considered an environmental-friendly approach to removing As in groundwater. In the present study, the oxidation/filtration dual-process with sprinkling height of 25 cm and 120 kg filter media efficiently increased the dissolved oxygen (DO) concentration (0.36–1.52 mg/L) and oxidation–reduction potential (ORP) (24–63 mV), which facilitated the formation of Fe oxides and As co-precipitation. The correlation of As removal efficiencies with their respective flow rates indicated that a decrease in groundwater Fe and an increase of Fe in sands and gravels filters as the flow rate increased evidenced the rapid oxidation of Fe to form the Fe hydroxides. In a 40-hour continuous aeration/filtration operation, As and Fe concentrations in groundwater were reduced by 79.5% and 64.88% within 40 hrs, respectively. The ease of filter replacement and cost-effectiveness in operation can be the major attractions and innovations for future field practices. [ABSTRACT FROM AUTHOR]

Arsenic is a harmful element that widely exists in various non-ferrous metal minerals including copper. With the depletion of free and low arsenic copper ores, containing arsenic copper ore has become an important mineral resource for copper smelting and processing. In the smelting and extraction of copper minerals, arsenic poses a serious hazard to the environment. Therefore, the safe and effective removal arsenic plays a crucial role in copper smelting and processing, and it has a great significance in promoting the green and healthy development of the copper industry. This review summarized the resource characteristics of arsenic containing copper minerals, systematically analyzed current smelting progress of containing arsenic copper minerals, and searched for the difficult and key points existed in pyrometallurgical and wet processes for containing arsenic copper mines. The reasons for difficult point formation were explored in treating arsenic containing copper minerals. The pyrometallurgical roasting followed by high-temperature filtration is documented to be an important development direction for smelting and processing of arsenic containing minerals. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a highly toxic metalloid, and its widespread contamination of water is a serious threat to human health. This study explored As removal using Fe(II)-oxidizing bacteria. The strain Fe7 isolated from iron mine soil was classified as the genus Pseudarthrobacter based on 16S rRNA gene sequence similarities and phylogenetic analyses. The strain Fe7 was identified as a strain of Gram-positive, rod-shaped, aerobic bacteria that can oxidize Fe(II) and produce iron mineral precipitates. X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy patterns showed that the iron mineral precipitates with poor crystallinity consisted of Fe(III) and numerous biological impurities. In the co-cultivation of the strain Fe7 with arsenite (As(III)), 100% of the total Fe and 99.9% of the total As were removed after 72 h. During the co-cultivation of the strain Fe7 with arsenate (As(V)), 98.4% of the total Fe and 96.9% of the total As were removed after 72 h. Additionally, the iron precipitates produced by the strain Fe7 removed 100% of the total As after 3 h in both the As(III) and As(V) pollution systems. Furthermore, enzyme activity experiments revealed that the strain Fe7 oxidized Fe(II) by producing extracellular enzymes. When 2% (v/v) extracellular enzyme liquid of the strain Fe7 was added to the As(III) or As(V) pollution system, the total As removal rates were 98.6% and 99.4%, respectively, after 2 h, which increased to 100% when 5% (v/v) and 10% (v/v) extracellular enzyme liquid of the strain Fe7 were, respectively, added to the As(III) and As(V) pollution systems. Therefore, iron biomineralized using a co-culture of the strain Fe7 and As, iron precipitates produced by the strain Fe7, and the extracellular enzymes of the strain Fe7 could remove As(III) and As(V) efficiently. This study provides new insights and strategies for the efficient remediation of arsenic pollution in aquatic environments. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a toxic metalloid disseminated in water, soil, and air. Arsenic contamination is currently a major public health concern. This study investigated arsenic removal by Fe(II)-oxidising bacteria in an aqueous solution. A bacterial strain, Z1, isolated from concentrated sludge, was identified as Sphaerotilus natans based on microscopic morphology, culture characteristics, and 16s rRNA gene sequences. After arsenic-resistant acclimation, Sphaerotilus natans Z1 successfully survived and propagated in high arsenic conditions (100 mg·L−1 As(V) or As(III)). To a certain extent, the isolated strain could decrease the concentration of As(III)/As(V) by biosorption under organic substance supply. Partial As(V) could be reduced to As(III) due to cytoplasmic arsenic reduction of bacteria. In addition, ferrihydrite, one of the iron oxides, was formed by the mediation of Sphaerotilus natans in the Winogradsky medium. Most of As(III)/As(V) could be effectively removed by sorbing onto the resultant ferrihydrite mineral. Thus, iron oxide minerals facilitated by Sphaerotilus natans may be an alternative remediation strategy for scavenging arsenic in the water environment. [ABSTRACT FROM AUTHOR]

The ceramic filter amended with iron (Fe) has proven to be a potential low‐cost method for arsenic (As) removal from groundwater. The presence of Fe, phosphate (P), and silicate (Si) significantly affects the As removal efficiency of the ceramic filter, which has not been passably investigated. The present research aimed to examine the effect of Fe, P, and (or) Si presence as single or in combination on As (III) removal from synthetics groundwater by a low‐cost iron amended ceramic filter (IACF). Laboratory‐scale filtration experiments at different compositions of Fe, P, Si, and As (III) were conducted by the IACF fabricated with a ceramic candle and iron netting box. Fe (II) in synthetic groundwater positively impacted As (III) removal. At a concentration of 2 mg/L of Fe (II), the As levels in the effluent decreased to less than the maximum contamination level (MCL) of 50 μg/L. Groundwater P concentration needed less than 3 mg/L or Si concentrations required less than 35 mg/L to effectively reduce As (III) to below the MCL at 5 mg/L of groundwater Fe (II). The cumulative effect of P and Si on As removal was found to be more significant than distinct contributions. The presence of 2 mg/L P and 35 mg/L or higher Si in the groundwater cumulatively reduced the As removal performance from 92% to 63%, and the MCL was not met. The negative impact of P and Si on As (III) removal followed the order of (P + Si) > P > Si. P competed with As for adsorption sites during the process, while Si inhibited the Fe release and floc formation, significantly reducing As removal performance. The study findings can potentially contribute to optimizing IACF as a low‐cost method for As removal from groundwater. [ABSTRACT FROM AUTHOR]

Arsenic (As) is a prominent carcinogen component produced via both geogenic and anthropogenic processes, posing serious risks to human health. This study aimed to investigate the potential of hydrochar prepared from red macroalgae for removing As from synthetic wastewater. The hydrochar was produced through 5 h hydrothermal carbonization (HTC) treatment at 200 °C, and then, chemically activated with ferric chloride hexahydrate (FeCl3·6H2O). SEM analysis revealed a permeable structure of hydrochar, while FTIR analysis detected the occurrence of several functional groups at the hydrochar interface. EDS analysis showed an increase in carbon concentration after FeCl3·6H2O activation. Hydrochar was then tested in batch experiments to investigate its As removal efficiency, with ICP-MS used to determine the levels of As after the adsorption process. The results showed that As removal efficiency increased with increasing initial As concentration from 50 to 250 mg/L, and the highest As removal efficiency was 84.75% at a pH of 6, initial concentration of 0.25 mg/L, and adsorbent dose of 1000 mg at 120 min. The Langmuir isotherm model supported the occurrence of homogeneous adsorption over the surface of hydrochar, while the pseudo-second-order model confirmed the chemisorptive nature of the process. [ABSTRACT FROM AUTHOR]

The presence of arsenic in water bodies poses a significant risk to both human health and the environment. Arsenic (As) contamination in water sources is a global environmental concern caused by both natural processes and human activities. Due to its toxic and persistent nature, arsenic has detrimental effects on ecosystems and human wellbeing. This study aimed to elucidate the mechanisms behind arsenic accumulation in water bodies. In aquatic environments, arsenic concentrations in drinking water have been reported as high as 1,320 μg/L (Nicaragua), while groundwater levels exceeded 5,000 μg/L (Thailand), and wastewater contained up to 134,000 μg/L (landfill leachate in Brazil). Furthermore, bioaccumulation of arsenic (μg/g) in fish species ranges from 0.4 (catfish in the Paraná River Delta, Brazil) to 362 (Pteromylaeus bovinus, Northern Adriatic Sea). Recent research has predominantly focused on removing arsenic from aqueous solutions through adsorption methods. Notably, nanoparticle adsorbents and graphene-based adsorbents demonstrate a high capacity for arsenic removal from water bodies.

Copper smelting flue dust (CFD) is a byproduct of pyrometallurgical copper production, containing valuable metals like lead, zinc, and copper, but also hazardous arsenic, which complicates its handling and recycling. Traditional methods for arsenic removal from CFD, such as pyrometallurgical and hydrometallurgical processes, are often inefficient or result in the loss of valuable metals. This study explores the efficacy of ultrasound-assisted leaching for selective arsenic extraction from CFD, offering a potentially more efficient and environmentally friendly alternative. We employed a combination of sodium hydroxide and sodium sulfide in an aqueous solution, enhanced by ultrasonic waves, to selectively recover arsenic into solution. The optimal leaching conditions were determined to be 0.4 M NaOH, 0.2 M Na2S, a liquid-to-solid ratio of 50 mL/g, a temperature of 80 °C, an ultrasound power of 150 W, and an ultrasound frequency of 100 kHz, under which up to 99% of arsenic was extracted within 45 min. The kinetic analysis conducted suggests that the leaching process is controlled by the chemical reactions occurring at the surface of the particles.

Arsenic pollution of water is one of the severest environmental challenges threatening human health. Iron-based nanomaterials have been demonstrated effective in arsenic removal. However, they generally suffer from low removal efficiency towards highly toxic As(III), loss of active sites owing to agglomeration, and poor reusability. Herein, we report a carbonized melamine foam supported Mn(IV)-doped β-FeOOH nanospindles(CF@Mn-FeOOH NSp) for tackling the technical hurdles. The designed CF@Mn-FeOOH NSp appears as a free-standing monolith through a low-cost and straightforward hydrothermal method. The atomic-scale integration of Mn(IV) into β-FeOOH enables an oxidation-adsorption bifunctionality, where Mn(IV) serves as oxidizer for As(III) and Fe(III) acts as adsorber for As(V). The maximal adsorption capacity for As(V) and As(III) can reach 152 and 107 mg g-1, respectively. Meanwhile, As in simulated high arsenic groundwater can be decreased to below 10 μg L-1 within 24 h. By simple "filtrating-washing", 85% and 82% of its initial adsorption capacity for As(V) and As(III) can be easily recovered even after 5-cycles reuse. Kinetics and isotherm adsorption study indicate that the arsenic adsorption behavior is mainly through chemical bonding during single-layer adsorbing process. The as-prepared CF@Mn-FeOOH offers a scalable, efficient, and recyclable solution for arsenic removal in groundwater and wastewater from mines and industry.

This study investigated the effect of oxides on the removal of As when present in simple mixtures with granular activated carbon (GAC) particles. The performance of these mixtures was compared with other reported GAC-based adsorbents. A standard curve for ultraviolet adsorption vs. As concentration was obtained using the silver diethyldithiocarbamate (SDDC) method to evaluate various samples. A preliminary study was carried out to find the optimal conditions for experiments. For 50 mL samples with 2.35 ppm As, the optimal values of pH, adsorption time, and amount of adsorbent were pH 7, 30 min, and 50 mg, respectively. The ratio between the amount of adsorbent and well water in this study showed a superior As adsorption capacity (1 g/L, 2.1 mg/g) compared to similar adsorbents reported previously (12.5 g/L, 1.0-1.4 mg/g). Among the adsorbents, KOH-treated AC-Mn3O4 exhibited the best performance in As removal with an efficiency of ~95%. The oxide particles had a synergistic effect with GAC on As removal. This was primarily due to the change in the potential of partially agglomerated nano Mn3O4 particles on the ACK surface. The influence of the surface area of the adsorbents was not pronounced. All results were explained in terms of microstructure, specific surface area, and zeta potential. This finding could be extended to other activated carbons (AC) obtained from different sources.

One of the main drawbacks of the application of photocatalysis for wastewater treatment is the use of dispersed photocatalysts, which are difficult to remove from effluent after the treatment process and may pose additional toxicity to the receiving bodies. As an alternative, immobilized catalysts can be applied; however, this strategy can increase the difficulties in mass and photo transfer. This work presents the development of an inert and highly porous support for TiO2 immobilization. The produced materials have a high surface area and contribute to diminishing the difficulties in mass and phototransfer during photocatalysis. Different types of polymeric materials were tested as support, and a Taguchi experimental design with an L9 arrangement was used to optimize the immobilization process and evaluate the effect of TiO2 content and the use of bidding agents, ultrasound, and thermic treatment. The grey automotive polyurethane foam proved to be the best support, using 5.0% of TiO2 (wt.%) in the immobilization suspension with Triton X as the binding agent and heat treatment during immobilization. At the optimal conditions, it was possible to achieve total As(III) oxidation (below the analytical detection limit) in 240 min, with nearly 100% As(V) present in solution at the end of the reaction (almost no As adsorption on the catalyst surface). In addition, the catalytic bed was able to promote the As(III) complete oxidation in up to five consecutive cycles without significant leaching or deactivation of the immobilized TiO2. [ABSTRACT FROM AUTHOR]

The threat of arsenic contamination in water is a challenging issue worldwide. Millions of people utilize untreated groundwater having high levels of arsenic in developing countries. Design Expert 6.0.8 has been used to design experiments and carried out statistical analysis for optimization of different parameters. It is of prime importance to develop cheap environment friendly bio-sorbent for protecting health of the poor from ill effects of arsenic. In the present investigation, we prepared bio-sorbent from the solid waste seed biomass of Mangifera indica (M), Artocarpus heterophyllus (JF), and Schizizium commune (JP). The characterization of bio-sorbents has been done by using different techniques namely FTIR and XRD. Arsenic concentration was estimated using ICP and adsorption parameters optimized for pH, adsorbent dose, and initial arsenic concentration. At pH 8.4, kinetics study of arsenic removal was M (94%), JF (93%), and JP (92%) for initial concentration of 2.5 ppm. The adsorption kinetics was well explained by Freundlich model and pseudo-second reaction order. [ABSTRACT FROM AUTHOR]

The remediation of arsenic contamination in potable water is an important and urgent concern, necessitating immediate attention. With this objective in mind, the present study investigated arsenic removal from water using batch adsorption and fixed-bed column techniques. The material employed in this study was a waste product derived from the treatment of groundwater water for potable purposes, having a substantial iron composition. The material's properties were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FT-IR). The point of zero charge (pHPZC) was measured, and the pore size and specific surface area were determined using the BET method. Under static conditions, kinetic, thermodynamic, and equilibrium studies were carried out to explore the influencing factors on the adsorption process, namely the pH, contact time, temperature, and initial arsenic concentration in the solution. It was found that the adsorption process is spontaneous, endothermic, and of a physical nature. In the batch adsorption studies, the maximum removal percentage was 80.4% after 90 min, and in a dynamic regime in the fixed-bed column, the efficiency was 99.99% at a sludge:sand = 1:1 ratio for 380 min for a volume of water with arsenic of ~3000 mL. The kinetics of the adsorption process conformed to a pseudo-second-order model. In terms of the equilibrium studies, the Sips model yielded the most accurate representation of the data, revealing a maximum equilibrium capacity of 70.1 mg As(V)/g sludge. For the dynamic regime, the experimental data were fitted using the Bohart–Adams, Thomas, and Clark models, in order to establish the mechanism of the process. Additionally, desorption studies were conducted, serving as an essential step in validating the practical applicability of the adsorption process, specifically in relation to the reutilization of the adsorbent material. [ABSTRACT FROM AUTHOR]

The environmental risks of industrial jarosite (JAR) were mainly attributed to its average particle size (8.6 µm) and its content of leachable heavy metals such as cadmium (Cd, 64.2 mg L−1), lead (Pb, 4.16 mg L−1), and arsenic (As, 0.27 mg L−1). In this study, various methods were reported to eliminate the leachable elements contained in JAR without collapsing the crystalline structure: acid leaching, ionic exchange, and extended remediation. The effect of pH (2–10), temperature (20–175 °C), and time (<30 min) on the leaching of Cd, Pb, and As were studied. The ultrasound-assisted leaching process (at <60 °C and for 12 min) using a 0.19 M H2SO4 solution allowed to obtain a reduction of leachable Cd (99.2 wt. %), Pb (94.2 wt. %), and As (98.1 wt. %). Although the H2SO4 remediated jarosite, for example, still had a content of Pb, Cd, As, and Mn of 9.25, 0.91, 3.89, and 2.41 g kg−1, respectively, these metallic compounds were insoluble in the pH interval of 2 to 10. The jarosite obtained using acid leaching, JAR2L, had the highest adsorption capacity of As(V) (Qmax = 7.55 g kg−1), while the jarosite obtained using extended remediation had the highest water adsorption capacity (165 mL kg−1). The JAR can be remediated using acid ultrasound-assisted leaching and it can be applied in formulating strategic materials for the chemical industry. [ABSTRACT FROM AUTHOR]

Arsenic is a toxic metalloid widely present in the aquatic environment, showing severe health hazards. Natural bentonite clay (BN) showed little affinity toward arsenic (arsenic(III) and arsenic(V)). However, organosilane functionalized clay showed greater affinity toward arsenic(III) and arsenic(V). Therefore, natural bentonite was functionalized with 3-mercaptopropyltrimethoxysilane (3-MPTS) and 3-aminopropyltrimethoxysilane (3-APTES). Materials' characterization was extensively conducted with advanced analytical methods and surface area analysis by the BET analyzer. Under batch experiments, the materials were then utilized to eliminate arsenic(III) and arsenic(V) in an aqueous medium. Compared to the pristine bentonite, the functionalized materials increased the adsorption capacities of arsenic(III) and arsenic(V). The moderate solution pH (pH 4–6) significantly favored the elimination of arsenic(III) and arsenic (V) by these advanced materials. The maximum sorption capacity of arsenic(III) by 3-MPTS/BN and arsenic (V) by 3-APTES/BN was found at 11.93 and 10.50 mg/g, respectively. These functionalized materials showed fast uptake of arsenic, which attained apparent equilibrium within 180 and 120 min of contact, respectively, for arsenic(III) and arsenic(V). The influence of ionic strength and several co-existing ions showed an insignificant influence on the removal effectiveness except in EDTA and phosphate. The results further showed the selectivity and efficiency of functionalized materials toward the studied pollutants. The novel functionalized materials showed potential for the efficient decontamination of arsenic. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron (nZVI) has a high removal affinity toward arsenic (As). However, the agglomeration of nZVI reduces the removal efficiency of As and, thus, limit its application. In this study, we report an environmentally friendly novel composite of Chlorella vulgaris–supported nanoscale zero-valent iron (abbreviated as CV-nZVI) that exhibits a fast and efficient removal of As(III) from As-contaminated water. Scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS), X-ray diffractometry (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterize and analyze the CV-nZVI. These results indicated that the stabilization effect of C. vulgaris reduced the nZVI agglomeration and enhanced the reactivity of nZVI. The experiments showed a removal efficiency of 99.11% for As(III) at an optimum pH of 7.0. The adsorption kinetics and isotherms followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm with the superior maximum adsorption capacities of 34.11 mg/g for As(III). The FTIR showed that the As(III) was adsorbed on the CV-nZVI surface by complexation reaction, and XPS indicated that oxidation reaction was also involved. After five reuse cycles, the removal efficiency of As(III) by CV-nZVI was 32.93%, suggesting that the CV-nZVI had some reusability and regeneration. Overall, this work provides a practical and highly efficient approach for As remediation in As-contaminated water, and simultaneously resolves the agglomeration problems of nZVI nanoparticles. [ABSTRACT FROM AUTHOR]

Many technologies for the treatment of arsenic-containing drinking water are available, but most of them are more effective on arsenic oxidized forms. Therefore, the pre-oxidation of As3+ is necessary. The electrochemical processes represent a very promising method due to the simultaneous oxidation of compounds using electrochemical conditions and the reactive radicals produced. In this work, As3+ oxidation was experimentally studied at a pilot scale using an electrochemical oxidation cell (voltage: 10 V; current: 1.7 A). The effect of the initial arsenite concentration, pH, and conductivity of drinking water on the oxidation of As3+ into As5+ was investigated. The results showed that the initial As3+ concentration strongly directly influences the oxidation process. Increasing the initial arsenite concentration from 500 to 5000 µg L−1, the pseudo-first order kinetic constant (k) strongly decreased from 0.521 to 0.038 min−1, and after 10 min, only 21.3% of As3+ was oxidized (vs. 99.9% in the case of As3+ equal to 500 µg L−1). Slightly alkaline conditions (pH = 8) favored the electrochemical oxidation into As5+, while the process was partially inhibited in the presence of a more alkaline or acidic pH. The increase in conductivity up to 2000 µS cm−1 enhanced the kinetic of the oxidation, despite remaining on the same order of magnitude as in the case of conductivity equal to 700 µS cm−1. After 10 min, 99.9 and 95% of As3+ was oxidized, respectively. It is the opinion of the authors that the influence of other operational factors, such as voltage and current density, and the impact of the high concentration of other pollutants should be deeply studied in order to optimize the process, especially in the case of an application at full scale. However, these results provide helpful indications to future research having highlighted the influence of initial As3+ concentration, pH, and conductivity on the electrochemical oxidation of arsenic.

This study investigated the effect of oxides on the removal of As when present in simple mixtures with granular activated carbon (GAC) particles. The performance of these mixtures was compared with other reported GAC-based adsorbents. A standard curve for ultraviolet adsorption vs. As concentration was obtained using the silver diethyldithiocarbamate (SDDC) method to evaluate various samples. A preliminary study was carried out to find the optimal conditions for experiments. For 50 mL samples with 2.35 ppm As, the optimal values of pH, adsorption time, and amount of adsorbent were pH 7, 30 min, and 50 mg, respectively. The ratio between the amount of adsorbent and well water in this study showed a superior As adsorption capacity (1 g/L, 2.1 mg/g) compared to similar adsorbents reported previously (12.5 g/L, 1.0-1.4 mg/g). Among the adsorbents, KOH-treated AC-Mn3O4exhibited the best performance in As removal with an efficiency of ~95%. The oxide particles had a synergistic effect with GAC on As removal. This was primarily due to the change in the potential of partially agglomerated nano Mn3O4 particles on the ACK surface. The influence of the surface area of the adsorbents was not pronounced. All results were explained in terms of microstructure, specific surface area, and zeta potential. This finding could be extended to other activated carbons (AC) obtained from different sources. [ABSTRACT FROM AUTHOR]

The intrinsic hydrophilicity of metal compounds, such as copper ferrite (CuFe2O4), and organic compounds, including graphene oxide (GO) and triethylenetetramine (TETA), make them promising adsorbents for heavy metals removal. The presence of lone pairs in these compounds is observed in modified polyethersulfone membranes used for the separation of arsenic (As) and total dissolved solids (TDS), including mono and divalent salts from aqueous solutions. The objective of this study was to investigate the performance of GO–TETA–CuFe2O4 membranes for wastewater treatment applications. The membranes were characterized for their optimal mechanical strength (tensile strength) and high negative charge (zeta potential) on the surface. Separation tests were conducted at different pressures and pH levels to evaluate the membrane's effectiveness in removing contaminants. In addition, the membranes were examined for their antibacterial properties. The modified membrane exhibited superior performance compared with the control membrane, with TDS removal rates of 93.8%, As3+ removal rates of 81.2%, and As5+ removal rates of 87.9%. The contact angle of the modified membrane was reduced, resulting in an increase in pure water flux from 13.11 to 27.87 L/m2.h. The modified membrane also demonstrated significantly higher resistance to fouling than the control membrane, with a resistance increase from 6.78 × 10+12 to 2.07 × 10+12 m−1. This contributed to the improved separation performance of As and TDS in a cross‐flow setup. The results suggest that the GO–TETA–CuFe2O4 modified membrane has great potential for use in water treatment applications. Practitioner Points: GO–TETA–CuFe2O4 was successfully used for modification of PES NF membrane structure.The efficiency of blended NF membranes with GO–TETA–CuFe2O4 significantly increased.The modified membranes exhibited significant water flux and antifouling properties.The GO–TETA–CuFe2O4/PES membranes showed high rejection of heavy metal ions and TDS than PES.The GO–TETA–CuFe2O4/PES membranes exhibited desirable antibacterial activity. [ABSTRACT FROM AUTHOR]

A novel manganese dioxide–hydrogen peroxide (MnO2–H2O2) system was developed for effective Arsenic (As) removal. Under the specified conditions of no external mechanical stirring, a trace H2O2 concentration of 0.015 wt%, and a MnO2 concentration of 25 mg/L, high removal efficiency (88%) of As (100 µg/L) was achieved by the MnO2–H2O2 system within 30 min, which differs from conventional adsorption processes that require external mechanical stirring and conventional arsenite (As (III)) oxidation–adsorption processes that require high quantities of oxidants (such as ozone) and specially synthesized adsorbents/catalysts. The high removal efficiency of As (III) by the MnO2–H2O2 system was attributed to the turbulent conditions precipitated by the extensively generated oxygen (O2) from the catalytic decomposition of H2O2, the efficient adsorption of As on the surface of MnO2, and the effective generation of reactive radicals including hydroxyl and superoxide radicals (•OH and •O2−). Moreover, the MnO2 adsorbents before and after As removal were characterized systematically, and the generated radicals were verified using electron spin resonance (ESR). The results showed that the formation of inner-sphere surface complexes by the surface hydroxyl groups of MnO2 particles and As was responsible for the effective As adsorption process, and the oxidation of As (III) to arsenate (As (V)) was achieved via the generated radicals. The influences of representative environmental factors on As removal performance and the application of the MnO2–H2O2 system in river water and ground water were further studied and tested. In conclusion, the MnO2–H2O2 system offers several advantages, including low cost, ease of operation, and strong environmental adaptability, making it highly promising for practical water treatment applications. [ABSTRACT FROM AUTHOR]

Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10,000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over 2 years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 μg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 μg/L As removed per kWh) compared to before cleaning (72.9 μg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales.

Drinking water contaminated with arsenic is a threat to human health. The present study attempts to remove arsenic using electrocoagulation with iron electrodes (ECFe) in continuous flow mode. Two experimental runs were separately conducted using untreated and treated (acid treatment followed by pH neutralization step) hematite as granular bed. The treatment of the hematite formed ferric oxy-hydroxides on hematite surface which was beneficial for arsenic removal. Total arsenic concentration reduced below 10 ppb from initial concentration of 500 ppb [As(III): As(V) = 1:1] with Fe dose of 5 mg/L after 48 h and 2 h of run conducted with untreated and treated hematite granular bed, respectively. The required Fe/As ratio of 10 was much lesser than the reported requirement of 250 in conventional systems. In the filter prototype using market-available filter cartridge, arsenic concentration reduced below 10 ppb from an initial concentration of 500 ppb [As(III): As(V) of 1:1] in both the absence and presence of phosphate (2 ppm) and silicate (30 ppm). HIGHLIGHTS The present study attempts to develop a household arsenic removal unit based on electrical system and natural hematite.; The designed prototype filter in the current study reduced As(tot) below 10 ppb from initial concentration of 500 ppb in the presence of phosphate (2 ppm) and silicate (30 ppm).;

Using the high arsenic copper dust from the copper fire refining furnace as the raw material, the low-temperature vacuum carbothermic reduction method is used to remove As from the dust. Differential thermal analysis of the raw materials was carried out by TGA-DSC, and the phase, chemical composition and morphology of the dust and evaporation residue were analyzed by XRD, ICP, SEM and other analytical methods. On the basis of thermodynamic analysis, the effect of evaporation temperature, residual pressure, reducing dose, evaporation time, etc. on the removal rate of As and other valuable metals. The results show that when the evaporation temperature is 350℃, the residual pressure is 100 Pa, the reducing amount is 25%, and the evaporation time is 50 min, the removal rate of As can reach 81.63% while ensuring that other metals do not evaporate basically, realizing As Selective separation of other valuable metals. The evaporate is As2O3 with higher purity, which can be used as primary As2O3 product. Valuable metals are enriched in the evaporation residue, which is convenient for the subsequent recovery of the waste acid leaching process.