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Arsenic (As) removal from portable water bodies using the nanotechnology-based adsorption technique offers a unique method to lower the As contamination below the World Health Organization’s (WHO) maximum contaminant level (MCL). This work promotes a systematic methodological-based adsorption study by optimizing the different parameters that affect As removal using TiO2/γ-Fe2O3 nanocomposites (T/M NCs) prepared with the green, facile, and cost-effective ball milling method. The studies using X-ray Diffraction (XRD) illustrate the structural modifications with variations in the constituting T/M ratios, with high-resolution transmission electron microscopy (HRTEM) being used for the NC morphological studies. The optical characterization studies showed that bandgap tuning between 2–2.8 eV reduced the maghemite (γ-Fe2O3) content in the NCs and the elemental analysis confirmed the desired stoichiometry of the NCs. The magnetic measurements showed that the magnetic interaction among the particles tends towards exchange coupling behavior as the weight ratio of γ-Fe2O3 content decreases in the NCs. The adsorption studies using the most efficient NCs with an optimized condition (NC dose (8 g/L), contact time (15 min), As concentration (2 ppm), and pH (4)) resulted in a more than 99% removal of As species, suggesting the excellent behavior of the synthesized nanomaterial for water treatment and making it more economical than other competing adsorption techniques and materials.

Primary aliphatic or aromatic amino acids on Phyllanthus emblica seed coat are derivatized in the form of N-substituted 2-sulfanylacetamide derivative. Pristine P. emblica (PPE) and derivatized P. emblica (DPE) products were used for removal of trivalent arsenic from aqueous sample. Thioglycolic acid and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimidehydrochloride (EDC) were used for the derivatization process. The carboxylic group of thioglycolic acid reacts with EDC to form an activated ester leaving group, which is displaced by nucleophilic attack of primary amino acids on seed coat. The BET surface area (0.3152±0.0081 m2/g) and Langmuir surface area (0.3571±0.0054 m2/g) of PPE are changed after modification. DPE showed high surface area compared to un-derivatized adsorbent due to presence of more modified groups on the surface (BET surface area 0.5812 m2/g, Langmuir surface area 0.6372 m2/g). Infrared and EDX studies confirmed modification of prepared material. The batch study was carried out by using 0.06 g/L of adsorbent dose at pH 7 for 120 minutes of contact time. The Langmuir qmax for PPE and DPE were observed to be 76.92 and 90.90 mg/g respectively. HIGHLIGHTS Facile modification on P. emblica seed coat.; N-substituted derivative of 2-sulfanylacetamide.; Trivalent arsenic has high affinity for sulfhydryl groups.; Removal of trivalent arsenic from aqueous sample.; Characterized by IR, SEM, EDX, and XRD techniques.;

Scrap steel is a kind of resource that can be recycled indefinitely. However, the enrichment of arsenic in the recycling process will seriously affect the performance of the product, making the recycling process unsustainable. In this study, the removal of arsenic from molten steel using calcium alloys was investigated experimentally, and the underlying mechanism was explored based on thermodynamic principles. The results show that the addition of calcium alloy is an effective means of reducing the arsenic content in molten steel, with the highest removal percentage of 56.36% observed with calcium aluminum alloy. A thermodynamic analysis revealed that the critical calcium content required for arsenic removal reaction is 0.0037%. Moreover, ultra-low levels of oxygen and sulfur were found to be crucial in achieving a good arsenic removal effect. When the arsenic removal reaction occurs in molten steel, the oxygen and sulfur concentrations in equilibrium with calcium were w O = 0.0012 % and w S = 0.00548 % , respectively. After successful arsenic removal, the arsenic removal product of the calcium alloy is Ca3As2, which usually does not appear alone. Instead, it is prone to combining with alumina, calcium oxide, and other inclusions to form composite inclusions, which is beneficial for the floating removal of inclusions and the purification of scrap steel in molten steel. [ABSTRACT FROM AUTHOR]

Due to the high-acidic arsenic-containing wastewater pollution greatly threatening human health and ecological safety, a simple and efficient method for reducing arsenic was proposed in this paper to solve this problem. By using potassium borohydride (KBH4) as a reducing agent, the soluble arsenic was converted into the gaseous arsine (AsH3) or solid arsenic (As0) to achieve the purpose of removing arsenic in wastewater. By exploring the reaction kinetics of the arsenic removal process, it was found that the fast reaction stage (0–2 min) conformed to pseudo-first-order kinetics. The removal rate of arsenic increased to over 73% in 0.5 min, and reaction equilibrium was reached after 30 min. Various influence factors including arsenic valence, aeration, addition method, concentrations of reducing agent, and hydrogen ion (H+) were investigated. The results showed that As(III) was easier to be removed by reduction than As(V), while adding KBH4 in multiples and aeration were both favorable to the removal of arsenic. Increased concentration of KBH4 also enhanced the removal of arsenic. Appropriate H+ concentration contributed to the arsenic removal, but excessive H+ concentration conversely has an inhibitory effect. The maximum removal rate of arsenic was 95.87%, with the maximum removal capacity of 45.50 mg/g. Based on the XRD and SEM–EDS analysis of residue, amorphous arsenic (As0) with a mass ratio of more than 94.52% was generated after the reduction of soluble arsenic. Our study demonstrated that the reaction mechanism of reductive degradation is soluble arsenic with hydrogen radicals (H•) to form arsenic (As0) and arsine (AsH3) (in the molar ratio of 6:1). Although the generated solid arsenic (As0) is convenient for the soluble arsenic removal from wastewater, attention must be paid to the formation of AsH3, and strategies for AsH3 treatment should be considered. [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. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride/boehmite composite membranes with hydrophilic surfaces were prepared using the nonsolvent induced phase inversion technique (NIPS) method to remove arsenate ions from water. The nanoparticles were added with different boehmite filler content. The contact angle of the bare membrane is 850, and it is reduced to 530, imparting hydrophilicity due to the presence of boehmite nanoparticles. The mechanical characteristics of the membranes have significantly improved. The BET and SEM results have shown that the average pore diameter gets reduced with boehmite addition, and surface area increases. Additionally, the use of nanoparticles enhanced the membranes' thermal stability. The nanofiltration unit is used to filter the arsenic‐contaminated water. The transmembrane pressure of ~4 bar is applied to all the membranes, and arsenic rejection; the flux of the membranes was calculated. The membrane has shown the highest rejection of 55% with a flux of 3.5659 L/m2.h. [ABSTRACT FROM AUTHOR]

The effects of the combined addition of Mg- and Ca-based adsorbents (MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, and CaCO3) were systematically tested for improving arsenic-removal performance and inhibiting the leaching of base material components from the adsorbent. Arsenic-removal tests were conducted with each single type or combination of two types of adsorbents. Results obtained after the combined-addition tests were compared with those obtained from the single-addition test with each adsorbent. The arsenic-removal performance improved in most combined additions but decreased in certain combined additions of MgO or Mg(OH)2 with Ca-based adsorbents. The arsenic-removal performance of the combined addition of MgCO3 and Ca(OH)2 was the highest. The combination of Mg-based adsorbents with CaO or Ca(OH)2 inhibited Mg-leaching, whereas that of CaO or Ca(OH)2 with MgCO3 inhibited Ca-leaching. Improvement in arsenic-removal performance for the combination of MgCO3 with CaO or Ca(OH)2 was caused by the incorporation and co-precipitation with arsenic when Mg(OH)2 and CaCO3 were produced. MgCO3-Ca(OH)2 and MgCO3-CaO are recommended for both arsenic removal and environmental adsorbent stability that can be effectively applied over a wide range of arsenic concentrations. [ABSTRACT FROM AUTHOR]

Brackish water has attracted increasing attention as a promising source to augment fresh water supply in many areas around the world. However, the ubiquitously high content of arsenic in brackish water presents a vexing technical challenge to reverse osmosis (RO) desalination plants. In this study, an integrated RO/vacuum membrane distillation (VMD) process was investigated for enhanced As(III) removal and water recoveries of brackish water desalination without requirement of pre-oxidation step as in other conventional treatment processes. The experimental results demonstrate that As(III) removal and water flux of the single RO process were profoundly affected by the conditions of the brackish water feed and the process water recovery. At pH 10, the As(III) removal maximized at 90%, and sharply dropped to below 80% as the process water recovery exceeded 70%. Exceeding the process water recovery of 70% also significantly reduced the RO process water flux. On the other hand, the VMD process was able to further treat concentrated RO brines with a 100% As(III) removal and stable water flux. Thanks to advantage of VMD, the integrated RO/VMD process at the global water recovery of 95.5% achieved adequate global As(III) removal, bringing the As(III) concentration in the product water down to below the 10-ppb allowable maximum limit. [ABSTRACT FROM AUTHOR]

Among various forms of anthropogenic pollution, the release of toxic metals in the environment is a global concern due to the high toxicity of these metals towards living organisms. In the last 20 years, sediment washing has gained increasing attention thanks to its capability to remove toxic metals from contaminated matrices. In this paper, we propose a Response Surface Methodology method for the washing of selected marine sediments of the Bagnoli-Coroglio Bay (Campania region, Italy) polluted with arsenic and other contaminants. We focused our attention on different factors affecting the clean-up performance (i.e., liquid/solid ratio, chelating concentration, and reaction time). The highest As removal efficiency (i.e., >30 μg/g) was obtained at a liquid/solid ratio of 10:1 (v/w), a citric acid concentration of 1000 mM, and a washing time of 94.22 h. Based on these optimum results, ecotoxicological tests were performed and evaluated in two marine model species (i.e., Phaeodactylum tricornutum and Aliivibrio fischeri), which were exposed to the washing solutions. Reduced inhibition of the model species was observed after nutrient addition. Overall, this study provides an effective tool to quickly assess the optimum operating conditions to be set during the washing procedures of a broad range of marine sediments with similar physicochemical properties (i.e., grain size and type of pollution). [ABSTRACT FROM AUTHOR]

Clean water is very important for the good health of society. In South Africa, it is estimated that people need 20 to 50 litres of safe water daily for basic hygiene, drinking, and cooking. In recent times, water bodies have harboured harmful pollutants, including oil, heavy metal ions, and dyes. As a result, this has become a major global concern. Societies with limited clean water are often forced to utilise contaminated water or buy filtered water, which might be a problem for poor residents. The health consequences that are related to contaminated water include Guinea worm disease, dysentery, cholera, etc. The side effects associated with the utilisation of unclean water are gastrointestinal diseases such as cramps, vomiting, and diarrhoea. The wastewater disposed of by chemical industries contains toxic elements such as arsenic. Wastewater that is released directly without treatment causes serious damage to the environment. Chronic arsenic poisoning can lead to keratinisation of the skin and even cancer. Cellulose biomass materials have the potential to become the greatest bio-based materials used in wastewater treatment applications. There are two major reasons that validate this statement: firstly, cellulose is a low-cost material that is abundant in nature, and, secondly, cellulose is an environmentally friendly material. However, these are not the only reasons that validate cellulose as a good candidate for wastewater treatment applications. Cellulose has a unique structure a large surface area, good mechanical properties and is degradable, renewable, and biocompatible. Cellulose also has an abundance of hydroxyl groups on its surface. These hydroxyl functional groups allow cellulose to be chemically modified in various ways, which results in the fabrication of nanocomposites with tunable characteristics. Since arsenic pollution has become a serious global concern, this review uniquely provides a broad discussion of the work that has been accomplished recently on the fabrication of functionalised cellulose-based materials designed specifically for the removal of arsenic heavy metal species from wastewater treatment facilities. Furthermore, the functionalised cellulose materials' arsenic adsorption capacities are also discussed. These adsorption capacities can reach up to a maximum of 350 mg/g, depending on the system used. Factors such as pH and temperature are discussed in relation to the adsorption of arsenic in wastewater. The removal of As(V) was found to be effective in the pH range of 3.0–8.8, with a removal efficiency of 95%. Moreover, the removal efficiency of As(III) was reported to be effective in the pH range of 6–9. However, the effective pH range also depends on the system used. The selective extraction of cellulose from various sources is also discussed in order to verify the percentage of cellulose in each source. Future work should be focused on how the chemical modification of cellulose affects the toxicity, efficiency, selectivity, and mechanical stability of cellulose materials. The use of cheaper and environmentally friendly chemicals during cellulose functionalisation should be considered. [ABSTRACT FROM AUTHOR]

Amalgamation of a supported liquid membrane (SLM) and electrocoagulation are carried out to remove As(III) and As(V) from drinking water to achieve a high treatment efficiency. The process is based on uphill transport of arsenic ions against their concentration gradients across phases and has the advantage of simultaneous extraction and recovery followed by electrocoagulation of arsenic. The aim of the process is selective separation of arsenic from drinking water and to reduce its concentration below 10 ppb. An iron‐arsenic precipitate is obtained by using an iron anode and the said precipitate is a value‐added saleable product. Various adsorption isotherms are evaluated to understand the removal mechanism of arsenic by the formation of iron‐arsenic precipitates. The Freundlich isotherm and Dubinin‐Radushkevich model are found to fit well with the adsorption data of the removal of arsenic ions. [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.

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.

Sulfuric acid was used as the leaching medium, and the leaching conditions, including acid concentration, liquid-solid ratio and temperature, were optimized by response surface methodology and Box-Behnken design (BBD). The results showed that the acid concentration was the most important factor, followed by temperature and liquid-solid ratio. Through response surface optimization, the optimal process conditions were determined as follows: acid concentration of 116.77 g/L, liquid-solid ratio of 8, and temperature of 170℃. Under these conditions, the arsenic extraction rate of copper converter reached 94.49%, indicating that the acid extraction experiment of lead converter arsenic ash could be successfully optimized by response surface methodology.

Arsenic decontamination is a major worldwide concern as prolonged exposure to arsenic (>10 µg L-1) through drinking water causes serious health hazards in human beings. The selection of significant, cost-effective, and affordable processes for arsenic removal is the need of the hour. For the last decades, iron-oxide nanomaterials (either in the magnetite or bimetallic form) based adsorptive process gained attention owing to their high arsenic removal efficiency and high regenerative capacity as well as low yield of harmful by-products. In the current state-of-the-art, a comprehensive literature review was conducted focused on the applicability of iron-based nanomaterials for arsenic removal by considering three main factors: (a) compilation of arsenic removal efficiency, (b) identifying factors that are majorly affecting the process of arsenic adsorption and needs further investigation, and (c) regeneration capacity of adsorbents without affecting the removal process. The results revealed that magnetite and bimetallic nanomaterials are more effective for removing Arsenic (III) and Arsenic (V). Further, magnetite-based nanomaterials could be used up to five to six reuse cycles, whereas this value varied from three to six reuse cycles for bimetallic ones. However, most of the literature was based on laboratory findings using decided protocols and sophisticated instruments. It cannot be replicated under natural aquatic settings in the occurrence of organic contents, fluctuating pH and temperature, and interfering compounds. The primary rationale behind this study is to provide a comparative picture of arsenic removal through different iron-oxide nanomaterials (last twelve yearsof published literature) and insights into future research directions.

Even though metal organic frameworks (MOFs) have rapidly emerged as useful materials in many applications, their inherent low conductivity necessitate hybridizing them with conductive carbon nanostructures like graphene or carbon nanotubes (CNTs) or carbon black especially in energy storage and energy generation applications like batteries, super capacitors, and electro-catalysts in oxygen reduction reaction (ORR). However, to date the synthesis of MOF/CNT is carried out by mixing pre-synthesized MOFs with oxidized or chemically modified CNTs. In this article, we report synthesis of nanometer-sized Ni-MOF/CNT by the reaction of nickelocene-derived nickel oxide-decorated CNTs with terepthalic acid synthesized from waste polyethylene terephthalate (PET). Morphological studies by scanning electron microscopy and transmission electron microscopy shows nanometer-sized Ni-MOF particles anchored on defect-rich carbon nanotubes, whereas the chemical changes associated wit transformation of NiO@CNT into nanometer-sized Ni-MOF/CNT were evaluated by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy analysis. The utility of nanometeric Ni-MOF/CNT as an electro-catalyst in urea oxidation reactions and removal of arsenic from contaminated water is reported. The applicability of our developed technique to synthesize nanometer Fe-MOF/CNT is also demonstrated. [ABSTRACT FROM AUTHOR]

Elevated arsenic (As) contamination in water, especially groundwater, has been recognized as a major problem of catastrophic proportions. This work explores As(V) removal via the coagulation-flocculation process by use of ferric chloride coagulant and polyacrylamide k16 co-coagulant as a first time. The effects of major operating variables such as coagulant dosing (50, 125 and 200 mg/L), co-coagulant dosing (5, 12.5 and 20 mg/L), pH (6, 7and 8), fast mixing time (1, 2 and 3 min), and fast mixing speed (110, 200 and 300 rpm) on As(V) removal efficiency were investigated by a Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM). According to factors F values, coagulant dosing, rapid mixing speed, pH, and co-coagulant dosing showed the most effect on As(V) removal efficiency, and the rapid mixing time factor indicated the slightest effect. The proposed quadratic model was significant with a p value < 0.0001 and has satisfactorily described the experimental data with R2 and adjusted R2 values of 0.9855 and 0.9738, respectively. Predicted model optimal conditions with target of complete As(V) removal were coagulant dosing = 197.63 ppm, co-coagulant dosing = 19.55 ppm, pH = 7.37, fast mixing time = 1.43 min and fast mixing speed = 286.77 rpm. The treatment of Nazarabad well water sample with an initial As(V) concentration of 5 mg/L under the optimal conditions removed 100% As(V) with the volume of produced sludge of 10.7 mL/200 mL. Increasing coagulant dosing, co-coagulant dosing, fast mixing time and fast mixing speed operation parameters from low-level to high-level values indicated 78%, 20%, 10.52% and 9.47% increases in volume of the produced sludge, respectively. However, a reduction of 13.63% in volume of the produced sludge resulted via pH increases. [ABSTRACT FROM AUTHOR]

Arsenic (III) is a toxic contaminant in water bodies, especially in drinking water reservoirs, and it is a great challenge to remove it from wastewater. For the successful extraction of arsenic (III), a nanocomposite material (ZnO–CuO/g–C3N4) has been synthesized by using the solution method. The large surface area and plenty of hydroxyl groups on the nanocomposite surface offer an ideal platform for the adsorption of arsenic (III) from water. Specifically, the reduction process involves a transformation from arsenic (III) to arsenic (V), which is favorable for the attachment to the –OH group. The modified surface and purity of the nanocomposite were characterized by SEM, EDX, XRD, FT–IR, HRTEM, and BET models. Furthermore, the impact of various aspects (temperatures, pH of the medium, the concentration of adsorbing materials) on adsorption capacity has been studied. The prepared sample displays the maximum adsorption capacity of arsenic (III) to be 98% at pH ~ 3 of the medium. Notably, the adsorption mechanism of arsenic species on the surface of ZnO–CuO/g–C3N4 nanocomposite at different pH values was explained by surface complexation and structural variations. Moreover, the recycling experiment and reusability of the adsorbent indicate that a synthesized nanocomposite has much better adsorption efficiency than other adsorbents. It is concluded that the ZnO–CuO/g–C3N4 nanocomposite can be a potential candidate for the enhanced removal of arsenic from water reservoirs. [ABSTRACT FROM AUTHOR]

Groundwater is one of the primary sources of water for both drinking and industrial use in northeastern Mexican territory, around 46% of the total, due to the lack of precipitation during the year and solar radiation index. The presence of arsenic in brackish soil and groundwater is a severe health issue, specifically in semi-arid and arid regions in the north of Mexico. Additionally, it represents the only source of drinking water in communities far from big cities, mainly due to the absence of hydric infrastructure. This work presents a new approach to treating polluted water with arsenic. The system based on activating jute fiber with nanoparticles of zero-valent iron immobilized over graphene oxide will allow nZVI particles to preserve their unique qualities for water sanitization. A dynamic flow test was designed to determine the effectivity of activated jute fibers as a water sanitation system. The results showed a reduction in the total arsenic content from 350 ppb to 34 ppb with a filtrate flow of 20 mL/min. The above represents 90% adsorption by the activated fiber. The analyzed sample corresponds to contaminated groundwater taken from Coahuila, Mexico. This sanitation system could be applied to low-income populations lacking robust infrastructure, such arsenic treatment plants. [ABSTRACT FROM AUTHOR]

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Arsenic contamination of water is a global environmental concern, and membrane technology combined with nanotechnology contributes to more efficient removal of arsenic. In this study, Fe–Mn oxide (FM), Polydopamine (PDA), and PDA-modified FM (PFM) were incorporated into polysulfone (PSF) to prepare adsorption membranes (PFMP) for arsenic removal. The prepared nanoparticles and membranes were characterized using TEM, SEM, FTIR, TGA, contact angle, and pure water flux. The introduction of particles enhanced the hydrophilicity of the membranes and significantly enhanced the pure water flux of the membranes. Adsorption experiments indicated that the PFMP membrane exhibited the best arsenic removal performance, with maximum adsorption capacities for As(III) and As(V) were 11.57 mg/g and 12.39 mg/g, respectively. The Langmuir model fitted the adsorption isotherms well, and the kinetics followed the pseudo-second-order model. The filtration experiment revealed that the PFMP membrane was capable of reducing As(III) solution (915 L/m2) and As(V) solution (1075 L/m2) from a concentration of 100 μg/L to the safe limit of As (＜10 μg/L). The As-loaded membrane was regenerated using NaOH solution (pH = 11), and the filtration experiment was repeated. FTIR and XPS demonstrated that the mechanism of the reaction between the membrane and arsenic was ligand exchange, where the arsenic ions were bonded to the oxygen ions to form Mn– O –As and Fe– O –As. [Display omitted] • Arsenite and Arsenate was high efficiently simultaneous removed by a new PDA functionalized FM oxide/PSF membrane. • The membrane includes two properties of adsorption and water separation. • The membrane is capable of reducing a large amount of the world's average concentration level of arsenic solution to the MCL level. • Removal of arsenite is a simultaneous process of oxidation and adsorption. [ABSTRACT FROM AUTHOR]

Arsenic-containing multi-metallic materials, are typical hazardous wastes generated in the process of tin recovery from zinc smelting leach slag, exhibit low resource utilization and pose a significant risk of environmental pollution. This research proposed a vacuum reduction roasting technique utilizing anthracite as the reducing agent to remove arsenic and reclaim tin from such materials, characterized by high arsenic levels (8∼wt%) and the presence of several valuable metals. The results indicated that the arsenate in these materials was transformed into As 2 O 3 , which has better volatility, while SnO 2 was converted to SnO and Sn. Moreover, under the optimal conditions of a roasting temperature of 750 °C, 10 % anthracite, and a roasting duration of 3 h, the arsenic removal efficiency reached 96.97 %, and the tin recovery rate was 84.48 %. Consequently, the arsenic concentration decreased to 0.53 %, and the tin concentration in the roasted product increased from 17.70 % to 31.41 %. The final product contained phases of arsenic and tin, including Sn, SnO 2 , and FeAs. Meanwhile, this study provides a promising solution for the green and efficient separation of tin and arsenic in typical arsenic-containing multi-metallic materials. • The evolution mechanisms of typical compositions Zn 3 (AsO 4) 2 , As 2 O 3 , As, SnO 2 , SnO, and Sn in arsenic-containing multi-metallic materials were investigated and discussed in detail. • Highly efficient arsenic removal (96.97 %) and green enrichment of tin in aresenic-containing multi-metallic materials. [ABSTRACT FROM AUTHOR]

Some studies have reported the removal of As (As) and fluoride (F −) using different sacrificial anodes; however, they have been tested with a synthetic solution in a batch system without hydrated silica (SiO 2) interaction. Due to the above, concurrent removal of As, F − , and SiO 2 from natural deep well water was evaluated (initial concentration: 35.5 μg L−1 As, 1.1 mg L−1 F − , 147 mg L−1 SiO 2 , pH 8.6, and conductivity 1024 μS cm−1), by electrocoagulation (EC) process in continuous mode comparing three different configurations of sacrificial anodes (Al, Fe, and Al–Fe). EC was performed in a new reactor equipped with a small flow distributor and turbulence promoter at the entrance of the first channel to homogenize the flow. The best removal was found at j = 5 mA cm−2 and u = 1.3 cm s−1, obtaining arsenic residual concentrations (C As) of 1.33, 0.45, and 0.77 μg L−1, fluoride residual concentration (C F − ) of 0.221, 0.495, and 0.622 mg L−1, and hydrated silica residual concentration (C SiO 2 ) of 21, 34, and 56 mg L−1, with costs of approximately 0.304, 0.198, and 0.228 USD m−3 for the Al, Fe and Al–Fe anodes, respectively. Al anode outperforms Fe and Al–Fe anodes in concurrently removing As, F − and SiO 2. The residual concentrations of As and F − complied with the recommendations of the World Health Organization (WHO) (As < 10 μg L−1 and F − < 1 mg L−1). The spectroscopic analyses of the Al, Fe, and Al–Fe aggregates showed the formation of aluminosilicates, iron oxyhydroxides and oxides, and calcium and sodium silicates involved in removing As, F − , and SiO 2. It is concluded that Al would serve as the most suitable sacrificial anode. • As, F−, and SiO 2 removal efficiency between different sacrificial anodes is reported. • Concurrent As, F−, and SiO 2 removal from deep well water is achieved. • After the EC process, the As, and F− concentrations met the WHO recommendations. • Al anode outperform Fe and Al–Fe anodes in concurrently removing As, F−, and SiO 2. • Aluminosilicates and iron oxides mainly form the aggregates of sacrificial anodes. [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.

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 (2SO4 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.

Nanomaterials such as copper nanoparticles have attracted significant attention because of their interesting size- and shape-dependent properties. However, their increased instability remains a challenge. This study therefore focuses on the growth of copper/copper oxide nanocrystals within nanofiber scaffolds, achieved by thermal reduction of poly-(vinyl alcohol) nanofibers cross-linked with copper-(II) acetate. A reduction temperature of up to 800 °C in 15% H2 balanced in N2 was found to lead to the formation of copper-based nanofibers (CuNFs) of sub-250-nm diameter that presented a core–sheath morphology, resulting from copper efflorescence. Enrobing a hydrolysis-resistant polymer core, the sheath layer was found to be composed of a discrete distribution of polymer-embedded crystalline nanospheres with diameters below 20 nm and of round crystallites of up to 65 nm protruding at the surface of CuNFs. With a significant proportion in copper intermediary states, this heterogeneous material is promising for various applications benefiting from the surface reactivity and versatile efficiency from the simultaneous presence of a transition metal and transition-metal oxide. For instance, with a material dose of 0.20 g·L–1 and an initial arsenic-(V) concentration of 120 mg·L–1, CuNFs yielded up to 96.5% arsenic-(V) removal. This route for the manufacture of copper hybrid nanofibers can be adapted to other transition metals and blends. [ABSTRACT FROM AUTHOR]

Arsenic present in drinking water is a serious concern due to its high toxicity. In this study, pomelo peel biochar coated with iron (PPCI) through slow pyrolysis carbonization and iron-coating processes was investigated for its ability to remove arsenite As(III) and arsenate As(V). The maximum adsorption capacity of As(III) and As(V) on PPCI at pH = 7 determined by the Langmuir model was11.77 mg/g and 15.28 mg/g, respectively. The PPCI's adsorption capacity was much higher than that of raw pomelo peel (PP) (0.033 mg/g and 0.034 mg/g for As(III) and As(V), respectively) and many other biomass-derived adsorbents reported in the literature. The change of solution pH (2.0–10 range) did not significantly affect the PPCI's adsorption capacity to As(III) or As(V) ions. In contrast, the presence of co-existing anions caused differential reductions in As removal efficiency (the effecting order: Cl–

Arsenic (As) removal from portable water bodies using the nanotechnology-based adsorption technique offers a unique method to lower the As contamination below the World Health Organization's (WHO) maximum contaminant level (MCL). This work promotes a systematic methodological-based adsorption study by optimizing the different parameters that affect As removal using TiO2/γ-Fe2O3 nanocomposites (T/M NCs) prepared with the green, facile, and cost-effective ball milling method. The studies using X-ray Diffraction (XRD) illustrate the structural modifications with variations in the constituting T/M ratios, with high-resolution transmission electron microscopy (HRTEM) being used for the NC morphological studies. The optical characterization studies showed that bandgap tuning between 2–2.8 eV reduced the maghemite (γ-Fe2O3) content in the NCs and the elemental analysis confirmed the desired stoichiometry of the NCs. The magnetic measurements showed that the magnetic interaction among the particles tends towards exchange coupling behavior as the weight ratio of γ-Fe2O3 content decreases in the NCs. The adsorption studies using the most efficient NCs with an optimized condition (NC dose (8 g/L), contact time (15 min), As concentration (2 ppm), and pH (4)) resulted in a more than 99% removal of As species, suggesting the excellent behavior of the synthesized nanomaterial for water treatment and making it more economical than other competing adsorption techniques and materials. [ABSTRACT FROM AUTHOR]

A lot of anthropogenic activities can discharge arsenic into the ecosystem such as industrial wastes, incineration of municipal, pesticide production and wood preserving. In addition, most arsenic soluble species can enter surface waters via runoff and leach into the groundwater. Around forty million people from all over the world are affected by arsenic through drinking water above the maximum contaminant level of 0.01 mg/L. The affected by inorganic arsenic through drinking water can cause a lot of diseases especially a unique peripheral vascular disease and blackfoot disease. These diseases usually cause gangrene and end with amputation of the legs and can also cause severe systemic atherosclerosis. In addition, the wastewater treatment techniques can be divided into two groups, adsorbents and membrane separations such as electrodialysis, nanofiltration and reverse osmosis. Furthermore, most of these techniques do not function at a low level of concentration, so that moderate to high levels of concentration are required. However, the use of some of these arsenic removal approaches is costly because they require a lot of energy and reagents. Moreover, this review discusses readily adsorption technologies that have been applied to remove arsenic from wastewater along with an analysis of arsenic chemistry and contamination. This review is also focused on the removal of arsenic from wastewater using different adsorbents such as iron, aluminium, natural and biological adsorbents. Its goal is to increase our fundamental understanding of this developing research subject and to identify future research and development strategies for sustainable and cost-effective arsenic adsorption technology. [ABSTRACT FROM AUTHOR]

This paper concerns the removal of arsenic and hydrated silica (HS) from groundwater (32.45 µg L−1 As, 5.70 mg L−1 F − , 155.5 mg L−1 HS, 30.0 mg L−1 SO 4 2-, 0.77 mg L−1 PO 4 3-, pH 8.36, and conductivity of 533 µS cm−1) by electrocoagulation (EC) using an up-flow continuous reactor. Iron electrodes were used as sacrificial anodes. The EC efficiency on pollutants removal at current densities from 4 to 8 mA cm−2 and mean linear flow velocities ranging from 1.1 to 4.5 cm s−1 were analyzed. The best EC trial was obtained at 8 mA cm−2 and 1.1 cm s−1, where the residual concentrations of As and HS were 1.1 µg L−1, and 33 mg L−1, respectively, giving values of electrolytic energy consumption (E cons) and overall costs (OC) of 1.96 kWh m−3 and 0.28 USD m−3. The proposed EC process agrees with the WHO guideline for the concentration of As (<10 μg L−1). XRF, SEM-EDS, XRD, FTIR, and Raman analyzes indicate that HS reacts with coagulant forming iron silicates. Arsenic was removed by adsorption on iron hydroxides, iron oxyhydroxides, and iron silicates flocs. Sulfate and phosphate are trapped and swept within the sedimentation of the flocs. The removal of fluorides (17%) is attributed to weak adsorption on the iron agglomerates. • Arsenic (As) and hydrated silica (HS) removal from groundwater by electrocoagulation (EC). • Iron plate sacrificial electrodes installed in an up-flow continuous EC reactor. • HS reacts with Fe(II) forming iron silicates, As was removed by adsorption on flocs. • EC meets the WHO guideline for arsenic (<10 μg L−1) and HS is eliminated. • Overall cost of 0.28 USD m−3, highlight the EC as an economical technology. [ABSTRACT FROM AUTHOR]

This article critically evaluates the conventional Kanchan Arsenic Filter (KAF) in order to determine the main reasons for its reported poor performance. The KAF was introduced in 2004 in Nepal and makes use of non-galvanized nails as a Fe0 source for As removal. As early as 2009, the KAF was demonstrated to be ineffective for As removal in many cases. This was unambiguously attributed to the Fe0 layer which is placed on top of a sand filter instead of being incorporated into a sand matrix. Despite this conceptual mistake, the conventional KAF has been largely distributed in Asia, and recent articles have assessed its sustainability. This study reiterates that the suitability of the technology, rather than its sustainability, should be addressed. Evidence shows that the KAF has the following design limitations: (i) uses iron nails of unknown reactivity, and (ii) operates on the principle of a wet/dry cycle. The latter causes a decrease in the corrosion rate of the used nails, thereby limiting the availability of the iron corrosion products which act as contaminant scavengers. Taken together, these results confirm the unsuitability of the conventional KAF. Besides correcting the design mistakes, more attention should be paid to the intrinsic reactivity of the used iron nails, including using alternative Fe0 materials (e.g., iron filings, steel wool) for filters lasting for just 6 or 18 months. Specific design considerations to be addressed in the future are highlighted. [ABSTRACT FROM AUTHOR]

Pure water is necessary for healthy life; however natural ground water has many toxic metals. Before drinking, it must be free from toxic metals that commonly causes cancer. For example, arsenic is hazardous element but unfortunately it is naturally present in ground water. Due to its high solubility, removal of arsenic from water is not easy. In recent decades, presence of arsenic in ground water has been reported in many areas of Pakistan. Purpose of current project is to estimate and eliminate arsenic contents from the ground drinking water of Tribal Belt of DG Khan. For the comprehensive survey, 200 water samples were collected from the areas where large proportion of ground water is being consumed for drinking. In this work, relatively cheaper and effective adsorbent namely S‒CuFe 2 O 4 have been synthesized for the quick removal of arsenic. Arsenic contents were converted to the arsenomolybdate complex (AMC) and this complex was then adsorbed on S‒CuFe 2 O 4 . Morphology and chemical characteristics have been evaluated via XRD, SEM, FT-IR, Raman, TGA, EDX, AFM and XPS techniques. Additionally, various kinetic models were employed to confirm and validate the adsorption phenomena. Based on the results and assessment, it has been concluded that 1.5 g of aforementioned adsorbent is adequate to deliver 432 gal of arsenic free water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Abstract The catalytic performance of a perovskite‐type lanthanum ferrite LaFeO3 to remove arsenic from water has been investigates for the first time. LaFeO3 was prepared by citrate auto‐combustion of dry gel obtained from a solution of the corresponding nitrates poured into citric acid solution. Kinetic studies were performed in the dark with As(V) and in the dark and under UV‐C irradiation at pH 6–7 with As(III) (both 1 mg L−1), and As : Fe molar ratios (MR) of 1 : 10 and 1 : 100 using the LaFeO3 catalyst. As(V) was removed from solution after 60 min in the dark in 7 % and in 47 % for MR=1 : 10 and MR=1 : 100, respectively, indicating the importance of the amount of the iron material on the removal. Oxidation of As(III) in the dark was negligible after 60 min in contact with the solid sample, but complete removal of As(III) was observed within 60 min of irradiation at 254 nm, due to As(III) photooxidation to As(V) and to As(III) sorption to a minor extent. Morphological and microstructural studies of the catalyst complement the catalytic testing. This work demonstrates that LaFeO3 can be used for the removal of As(III) from highly arsenic contaminated water.

Chemical precipitation is one of the most widely known methods for treatment of industrial wastewaters with high sulphate content, where sulphate can be precipitated as practically insoluble ettringite (Ca6Al2(SO4)3(OH)12·26H2O). This treatment method is also widely recognised for solidifying hazardous components and toxic elements e.g. arsenic in wastewater. In the ettringite precipitation process, lime and aluminium salts are typically used as starting materials, in stoichiometric amounts to form ettringite from the sulphate-containing water, leading to a pH rise to ∼11.5 and ettringite precipitation. In the current study, for the first time, ye’elimite mineral (Ca4Al6O12SO4), also known as calcium sulfoaluminate (CSA) in cements, is used in order to investigate its suitability to form ettringite precipitate from sulphate and arsenic containing synthetic wastewater and industrial wastewater solutions. The dissolution of ye’elimite prior to dosing, optimal precipitation pH, and arsenic co-precipitation were studied. The effluent and precipitates were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM-EDS) and inductively coupled plasma atomic emission spectroscopy (ICP-OES). The results showed that high percentage of sulphate removal (98% in the synthetic wastewater and 87% in the industrial wastewater) can be achieved using ye’elimite as the aluminium source in ettringite precipitation. Additionally, up to 95% arsenic removal was achieved in arsenic co-precipitation experiments from the synthetic wastewater. The current developed technology can be used as a novel ecological and cost-effective approach for removal of sulphate and toxic elements from wastewater.

Electrocoagulation (EC) is a significantly efficient method for As removal from waters and received considerable attention recently. In this study, the natural groundwater (GW) samples containing As concentrations of GW-1: 538.8 μg L−1, GW-2: 1132.1 μg L−1, and GW-3: 52, 000 μg L−1 were obtained from different provinces and treated by EC process using different iron anodes (plate, ball, and scrap). To achieve drinking water As standard (10 μg L−1), the operational time, applied current, and As removal optimization for all anode types were studied. At applied current of 0.025 A, the As removal efficiency, EC time, and operating cost were >99.9%, 180 min and 0.406 $ m−3 for ball anodes, >99.9%, 100 min and 0.0813 $ m−3 for plate anodes, >99.9%, 80 min and 0.0815 $ m−3 for scrap anodes for GW-3, respectively. It was observed that as the As concentration in the GW increased, the EC time and operating cost increased. Overall, it was concluded that Fe scrap anodes are more advantageous than other types of anodes in terms of operating cost in EC reactor for As removal.

The presence of high levels of carcinogenic metalloid arsenic (As) in the groundwater system of Bangladesh has been considered as one of the major environmental disasters in this region. Many parts of Bangladesh have extensively reported the presence of high levels of arsenic in the groundwater due to both geological and anthropogenic activities. In this paper, we reviewed the available literature and scientific information regarding arsenic pollution in Bangladesh, including arsenic chemistry and occurrences. Along with using As-rich groundwater as a drinking-water source, the agricultural activities and especially irrigation have greatly depended on the groundwater resources in this region due to high water demands for ensuring food security. A number of investigations in Bangladesh have shown that high arsenic content in both soil and groundwater may result in high levels of arsenic accumulation in different plants, including cereals and vegetables. This review provides information regarding arsenic accumulation in major rice varieties, soil-groundwater-rice arsenic interaction, and past arsenic policies and plans, as well as previously implemented arsenic mitigation options for both drinking and irrigation water systems in Bangladesh. In conclusion, this review highlights the importance and necessity for more in-depth studies as well as more effective arsenic mitigation action plans to reduce arsenic incorporation in the food chain of Bangladesh. [ABSTRACT FROM AUTHOR]

Fluoride and arsenic are hazardous inorganic contaminants due to associated health risks and relatively higher levels of occurrence in groundwater. Metal-organic frameworks, (MOFs) with their high surface area, versatile building blocks and numerous active sites, are a novel approach to fluoride and arsenic uptake. This review presents the different types of MOFs for fluoride and arsenic removal along with a study of dynamic breakthrough times and cost analysis. MOF performances are based on a variety of synthesis methods, notable among which solvothermal one is more described. However, all research works concluded that MOFs have poor yield compared to conventional adsorbents. But, their high adsorption capacity, tailored chemical structure and ionic uptake of fluoride and arsenic make them a more favorable option than many other adsorbents. The cost of different MOFs usually varies between 0.1 and 5 US$/g depending on the synthesis routes. [ABSTRACT FROM AUTHOR]

Arsenic (As), a naturally occurring element found in rocks and in the Earth's crust, is one of the most dangerous things that can get into drinking water. A unique system for filtering arsenic has been developed that makes use of naturally available laterite soil. To scale this technology and realize its full potential, a deep understanding of the relationship between filter life and operating regime (inlet concentration of arsenic, filter size, and laterite material) is required. We aim to study a mathematical model that presents relationship between the concentration (c) and adsorption (G) with dimensionless time. Based on Langmuir kinetics, the model integrates intra-particle mass transport of the contaminant within the filter medium. The model predicts the dependency of the filter adsorption rate and outlet concentration on several dimensionless parameters. Filter efficiency for both treated laterite and raw laterite are also studied here. [ABSTRACT FROM AUTHOR]

A novel ternary adsorbent was prepared by reductive deposition of zerovalent iron on reduced graphene oxide through in-situ polymerization of aniline. SEM/EDS study showed an irregular, porous, and heterogeneous surface morphology with iron available for As binding. Batch adsorption experiments were conducted to determine the optimum conditions for As adsorption with optimum adsorbent dose, initial concentration of As, pH etc. Under optimized conditions, the maximum removal percentage of As was 99.6% for As(III) and 89% for As(V). The adsorption of arsenic on the composite was fitted well to the pseudo-second-order kinetic model and obeyed both Langmuir [R2 = 0.955 for As(III) and 0.992 for As(V)] and Freundlich [R2 = 0.975 for As(III) and 0.993 for As(V)] models. In aqueous solutions, the common co-ions phosphate hindered As removal more than the any other ions. The absorptive ability of adsorbent was compared with those of different adsorbents and found to be considerably efficient. [ABSTRACT FROM AUTHOR]

In this study, arsenic removal was carried out via low-temperature vacuum carbothermal reduction method by utilizing dust containing higher content of arsenic and copper from pyrometallurgical refining furnaces of copper as raw materials. Effect of various factors such as reduction temperature, residual pressure, reductant dosage and time on the removal rate of arsenic was investigated and explored in detail. Arsenic reduction kinetics was analyzed and elaborated in detail on the basis of "shrinking-core model". The results show that arsenic removal rate is enhanced with low reduction temperature and increasing amount of reduction dose, and decreasing residual pressure. Arsenic reduction removal is indicated to be controlled by ash diffusion. Apparent activation energy ~15.96 kJ/mol is determined for the reaction in the temperature range of 623–773 K. The kinetic equations for arsenic removal during vacuum carbothermal reduction can be described as 1 – 2a/3 – (1 – a)2/3 = 0.05774 exp[–1919.05/T]t. [ABSTRACT FROM AUTHOR]

In this study, four systems (S1, S2, S3, and S4) were evaluated to determine whether basic oxygen furnace sludge (BOFS), mainly composed of Fe (84%, mostly as elemental Fe and FeO), Ca (3%, as CaCO3), and Si (1%), is capable of removing As-spiked, Mn, Mg, and sulfate from an industrial acid mine drainage (AMDi) collected in a gold mine in Minas Gerais, Brazil. In the S1 system (BOFS/deionized water pH 2.5), the stability of the residue was evaluated for 408 h under agitation. The results showed that only Ca and Mg were solubilized, and the pH increased from 2.5 up to 11.4 within the initial 24 h and kept still until the end of the experiment (408 h). The S2 system (BOFS/AMDi) achieved 100% removal of As and Mn, and 70% removal of sulfate after 648 h. In the first 30 min, the pH increased from 2.5 to 10, which was maintained until the end of the experiment. The removal of As, Mn, and sulfate in the presence of hydrogen peroxide (S3 and S4 systems — BOFS/AMDi/H2O2) was similar to that in the S2 system, which contained only BOFS. The formation of iron oxides was not accelerated by H2O2. As regards the removal of arsenic and sulfate species, the formation of incipient calcium arsenate and calcium sulfate dehydrated was indicated by X-ray diffraction analysis and PHREEQC modeling. Dissolved manganese and magnesium precipitated as oxides, according to the geochemical modeling. After contact with AMDi, the raw BOFS, initially classified as hazardous waste, became a non-inert waste, which implies simplified, less costly disposal. Except for sulfate, the concentrations of all the other elements were below the maximum permitted levels. [ABSTRACT FROM AUTHOR]

The development of industrialisation increases the abundance of heavy metals, anionic, and harmful gases in the environment. Several techniques are already being used for the removal of different kinds of contaminants, but most of them are far away from their optimum performance. Among different approaches, the capturing of water and air pollutants by functionalised materials has been investigated widely due to cost-effectiveness, and high efficiency. From this point of view, silicon-based nanoclusters have attracted much attention due to their outstanding performance in terms of sensing properties. In the present work, we have applied the CrSi14 cluster for selective capturing of environmental pollutants. To this end, the adsorptions of heavy metal ions (As3+, Pb2+, Cd2+, Hg2+), inorganic anions (CN−, S2−, NO2−), and gas molecules (CO, N2, CH4, CO2, NO2, H2S) on the pristine CrSi4 cluster (PC) and the functionalised cluster (FC) by 1-ethyl-3-methyl imidazolium have been investigated using first-principles methods. The results indicate that PC is not only sensitive to capture As3+ but also acts highly selective so that other examined metals would not interfere with the arsenic removal. The PC also exhibits high sensitivity toward S2- and can be considered as a prominent sorbent for the removal of sulfide. [ABSTRACT FROM AUTHOR]

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