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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.

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.

Nanoparticles have been applied to remediate heavy metal pollutants (e.g., arsenic) in groundwater and soil, where the migration mechanism of pollutants in this multi-component system has not been fully understood. To better understand how nano-iron oxide affects arsenic migration under multivariate influence, this study prepared arsenic loaded composite colloids using arsenic (As(V)), humic acid, and nano iron oxide (n-α-Fe2O3). Then we explored the migration behavior of the composite colloids (HA-n-α-Fe2O3) loaded As(V) in a quartz sand column affected by n-α-Fe2O3 under various humic acid concentrations, pH values, ionic strengths, and ferric oxide contents. Two migration models, including a classical advection-dispersion equation (ADE) and a Hausdorff fractal advection-dispersion equation (HADE), were used to quantify the observed co-migration of arsenic conveyed by HA-n-α-Fe2O3 colloids loaded As(V) in the column. Our analysis indicates that the adsorption capability of nano-iron oxide on arsenic decreases with pH, humic acid and iron oxide concentrations, thus accelerating arsenic movement. While, the increasement of ionic strength enhances the adsorption force of nano-iron oxide on arsenic and suppresses arsenic migration. Furthermore, simulation results suggest that the HADE model outperforms the traditional ADE model in characterizing arsenic migration, where the time derivative index is an indicator of anomalous diffusion.

Arsenic is a highly toxic and carcinogenic element, which poses a huge threat to millions of people. The toxicity of arsenic links to its solubility. Therefore, the immobilization of arsenic is of great significance. Among a series of arsenic immobilization materials (include arsenate, arsenite and arsenide), scorodite is the most suitable one due to its excellent stability. In this study, we propose a novel method to synthesize scorodite using ferrihydrite as an in situ iron donator. The process occurs via the dissolution of ferrihydrite followed by the coprecipitation of iron and arsenic ions on the surface of ferrihydrite. A series of experiments were carried out to investigate the optimal reaction conditions and applicable scope of initial arsenic concentration for this process. The results indicated that 99.9% of arsenic was removed from aqueous solution and immobilized as stable scorodite at reaction time of 6 h, pH 1.5, Fe/As molar ratio of 1.1 and reaction temperature of 90°C. This process is applicable to the solution with initial arsenic concentration ranging from 1 to 10 g/L, which shows great potential for practical applications.

Arsenic is a harmful associated element in antimony ore, which might bring out the risk of leakage during complex industrial production of high-purity antimony. Herein, we reported a novel and efficient way to remove the trace arsenic impurity from acidic SbCl 3 solution by utilizing copper-system bimetallic particles. Specifically, galvanically coupled Cu 2 Sb/Cu was in-situ synthesized by introducing precursor copper powder to the specific SbCl 3 solution. DFT studies revealed that Sb(III) was easily reduced by Cu to form Cu 2 Sb due to the strong adsorption of Sb(III) on Cu (111) crystal plane. The Cu 2 Sb/Cu coupling exhibited excellent activity for As(III) reduction, over 99.4% arsenic were removed under optimal conditions and residual arsenic concentration dropped to only 2.7 mg L -1 . Crucially, Sb(III) concentration changes could be neglected. Besides, the dearsenization residues were extensively characterized to analyze the evolvement and cause in the reaction process. The results confirmed that the arsenic removal mechanisms by Cu 2 Sb/Cu particles were multi-affected, including adsorption, displacement, and precipitation. And the strong electrostatic attraction of AsO + under high HCl conditions was identified as a key step to achieving dearsenization. This research will provide a theoretical guidance for the green synthesis of high-purity antimony and related products., Competing Interests: Declaration of Competing Interest No conflict of interest exists., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Adsorption-oxidation is a promising technique to decontaminate As(III) polluted water. In present study, ZrO 2 -modified covalent organic framework (ZrO 2 -COF) was fabricated and used to remove arsenic from water under visible light irradiation. The results showed that ZrO 2 -COF (0.2 g/L) could efficiently capture As(III) (5 mg/L) from water and then oxidize the adsorbed As(III) into less toxic As(V) under visible light irradiation (60 min), achieving the complete decontamination of As(III) polluted water. Based on characterization results and theoretical calculations, we found that in ZrO 2 -COF composite, ZrO 2 served as sites for adsorption of As(III)/the latter transformed As(V), while COF worked as photocatalytic center for As(III) oxidation. Effective As(III) removal could also be achieved by ZrO 2 -COF under visible light irradiation in complex water chemistry conditions including wide solution pH range (3-11), broad solution ion strength range (1-100 mM), the copresence of natural organic matter (0.1-1 mg/L humic acid) and various coexisting ions in solutions, as well as in real water samples. In addition, we found that ZrO 2 -COF had excellent reuse performance in 4 consecutive cycles. Our results showed that under visible light irradiation, ZrO 2 -COF composites could be a promising technique for efficient As(III) removal from 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 © 2023 Elsevier B.V. All rights reserved.)

Combining adsorption with other technologies holds great potential in fast and deep arsenic ion removal. Herein, chitosan‑zirconium composite adsorptive membranes (CS-Zr CM) were successfully prepared using simple casting and sodium hydroxide coagulation strategies, which was demonstrated the use in arsenic ion-capture electrodialysis based on their good adsorption performance. In the batch adsorption tests, the maximum adsorption capacities of CS-Zr CM for As(III) and As(V) were 134.2 mg/g and 119.5 mg/g, respectively. CS-Zr CM also exhibited satisfying adsorption selectivity and good reusability toward As(III) and As(V). However, the adsorption kinetics showed that they needed 48 h to reach the adsorption equilibrium and the adsorption ability toward trace arsenic ion was ineffective. Furthermore, CS-Zr CM was applied as the adsorptive membrane in the electrodialysis process. Under the influence of electric field, the As(III) and As(V) removal equilibrium time was shortened to 12 h and the concentrations of As(III) and As(V) ions could be efficiently reduced to below the WHO limit in drinking water (10 μg/L), which far surpassed the physicochemical adsorption method. Such good arsenic ion removal ability of CS-Zr CM together with the ease scalable fabrication, low cost, and biodegradable properties shows its huge prospects in arsenic-containing wastewater treatment., 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 © 2023 Elsevier B.V. All rights reserved.)

Arsenic (As) contamination poses a significant threat to human health, ecosystems, and agriculture, with levels ranging from 12 to 75% attributed to mine waste and stream sediments. This naturally element is abundant in Earth's crust and gets released into the environment through mining and rock processing, causing ≈363 million people to depend on As-contaminated groundwater. To combat this issue, introducing a sustainable hydrochar system has achieved a remarkable removal efficiency of over 92% for arsenic through adsorption. This comprehensive review presents an overview of As contamination in the environment, with a specific focus on its impact on drinking water and wastewater. It delves into the far-reaching effects of As on human health, ecosystems, aquatic systems, and agriculture, while also exploring the effectiveness of existing As treatment systems. Additionally, the study examines the potential of hydrochar as an efficient adsorbent for As removal from water/wastewater, along with other relevant adsorbents and biomass-based preparations of hydrochar. Notably, the fusion of hydrochar with nanoparticle-centric approaches presents a highly promising and environmentally friendly solution for achieving the removal of As from wastewater, exceeding >99% efficiency. This innovative approach holds immense potential for advancing the realms of green chemistry and environmental restoration. Various challenges associated with As contamination and treatment are highlighted, and proposed solutions are discussed. The review emphasizes the urgent need to advance treatment technologies, improve monitoring methods, and enhance regulatory frameworks. Looking outlook, the article underscores the importance of fostering research efforts, raising public awareness, and fostering interdisciplinary collaboration to address this critical environmental issue. Such efforts are vital for UN Sustainable Development Goals, especially clean water and sanitation (Goal 6) and climate action (Goal 13), crucial for global sustainability., 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 © 2023 Elsevier Inc. All rights reserved.)

Microwave-hydrothermal method was used for the synthesis of TiO2 and TiO2 doped with zirconium. The method was fast and simple and adsorbents were used for removal of As(III) and As(V) from aqueous solutions. The adsorbents were characterized by BET surface area measurements and powder XRD. Experiments showed that TiO2 doped with 10% of Zr using the microwave-hydrothermal method have greater specific surface area and total pore volume in comparison with TiO2 synthesized using the same method. Better removal with doped adsorbent was obtained for both, As(III) and As(V). Further experiments were carried out with Zr doped TiO2 sorbent in order to examine kinetic of adsorption, influence of pH and effect of common anions present in natural waters.

Arsenic is a toxic metalloid existing widely in the environment, and its removal from contaminated water has become a global challenge. The use of bacteria in this regard finds a promising solution. In the present study, Exiguobacterium sp. As-9, which is an arsenic resistant bacterium, was selected with respect to its arsenic removal efficiency. Quantification of arsenic in the water treated with bacterium showed that Exiguobacterium efficiently removed up to 99% of arsenic in less than 20 h. In order to reveal the possible effect of this bacterium in removal of arsenic from water and protecting fishes from the detrimental effects of arsenic, we initiated a range of studies on fresh water fish, Channa striata. It was observed that the fishes introduced into bacteria treated water displayed no symptoms of arsenic toxicity which was marked by a decreased oxidative damage, whereas the fishes exposed to arsenic revealed a significant (p

Solidification of soluble arsenic from extremely acidic water and direct use of recovery water have been the major challenges in global water management, with the urgent need for new treatment system development. Thus, magnetic adsorption - fertilizer drawn forward osmosis (FDFO) hybrid system with a novel adsorbent and fertilizer mixture to solve the drawbacks of each process was developed with the ultimate goals of metal removal and direct reuse for hydroponic irrigation. Magnetic metal-organic framework-based adsorbent (CMM) was synthesized with various promising capabilities, i.e., wide pH range efficiency, strong pH adjustment, good stability, fast adsorption (1 h), and oxidation (40 min), high capacity (175 and 126 mg/g for As(III), As(V)), strong magnetization (75 emu/g), complete separation by a magnet, excellent interference-tolerance and reusability. In the FDFO system, a massive water volume (50 times higher than the initial draw solution with suitable nutrients for hydroponics irrigation with acceptable NaCl levels was obtained for the first time up to now. However, low As(III) rejection (50%) required the FDFO process to improve more. After integrating with magnetic adsorption, nearly 100% of As was removed. The pH of feed solutions adjusted from extremely acidic to close to neutral conditions further solidified metal by precipitation and membrane separation processes, leading to almost no detection of metals in the final draw solution. Also, favorable nutrients and excellent reusability were obtained. This hybrid process would generally offer an environmentally sustainable and high efficiency for decontaminating As-containing heavy metal water for hydroponic irrigation., 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 © 2023. Published by Elsevier B.V.)

Removal of arsenic from drinking water is one of the most important global concerns. Among the various techniques, adsorptive removal of arsenic is considered as a viable most effective method. However, limited attention is given to understand the overall relative sorption capacity of different sorbents (e.g., biocomposite, biochar and nano-composite etc.) since various factors influence the sorption capacity. The aim of this study is to assess the effectiveness of various adsorbents with quantitative estimation (Langmuir adsorption maxima, Qmax) as well as to evaluate the influence of experimental conditions on the achievement of maximum adsorption. A number of analyses including meta-analysis, analysis of variance (ANOVA), scientometric and regression were performed. The results revealed that among the sorbents, nanoparticles show the greatest sorption capacity while pre-doped biochar performed the best among different biochars. Average across all sorbents, As (V) removal efficacy was higher than As (III). As expected, a high point of zero charge (PZC) and higher positive surface charge favored adsorption. The relative contribution of different mechanisms was also discussed. Our scientometric analyses revealed that, research should focus on the development of low-cost adsorbents and increase their reusability, safe disposal of adsorbed arsenic. Altogether, our findings provide a molecular understanding of arsenic sorption to different sorbents with implications for tailoring a good sorbent for arsenic removal from drinking 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 © 2022 Elsevier B.V. All rights reserved.)

Household sand filters (SFs) are widely applied to remove iron (Fe), manganese (Mn), arsenic (As), and ammonium (NH 4 + ) from groundwater in the Red River delta, Vietnam. Processes in the filters probably include a combination of biotic and abiotic reactions. However, there is limited information on the microbial communities treating varied groundwater compositions and on whether biological oxidation of Fe(II), Mn(II), As(III), and NH 4 + contributes to the overall performance of SFs. We therefore analyzed the removal efficiencies, as well as the microbial communities and their potential activities, of SFs fed by groundwater with varying compositions from low (3.3 μg L -1 ) to high (600 μg L -1 ) As concentrations. The results revealed that Fe(II)-, Mn(II)-, NH 4 + -, and NO 2 - -oxidizing microorganisms were prevalent and contributed to the performance of SFs. Additionally, groundwater composition was responsible for the differences among the present microbial communities. We found i) microaerophilic Fe(II) oxidation by Sideroxydans in all SFs, with the highest abundance in SFs fed by low-As and high-Fe groundwater, ii) Hyphomicropbiaceae as the main Mn(II)-oxidizers in all SFs, iii) As sequestration on formed Fe and Mn (oxyhydr)oxide minerals, iv) nitrification by ammonium-oxidizing archaea (AOA) followed by nitrite-oxidizing bacteria (NOB), and v) unexpectedly, the presence of a substantial amount of methane monooxygenase genes (pmoA), suggesting microbial methane oxidation taking place in SFs. Overall, our study revealed diverse microbial communities in SFs used for purifying arsenic-contaminated groundwater, and our data indicate an important contribution of microbial activities to the key functional processes in SFs., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Among the contaminants found in groundwater, arsenic poses a great threat to human health and the ecosystem. Therefore, it is vital to eliminate arsenic from water sources. This study utilizes one of the most efficient and emerging decontamination techniques known as the sono-electrocoagulation method. In recent years, sono-electrocoagulation has attracted many scientists due to its unique features, such as being cost-effective, rapid process, and high efficiency. The required groundwater samples were artificially synthesized in the laboratory, where the anode and cathode were determined to be Fe, Ti/PbO2, and Al, respectively. During the experiment, the impact of pH (5,6,7,8), various initial concentrations (100, 200, 300,400, 500, 600 μg/l), exposure times of 5,10,15,20,25 min, electrode distances of 1.5,2,2.5,3,3.5 cm and different current intensities of 5,10,15,20,25 mA/cm2 were examined. The ambient temperature of the laboratory was kept at 30 and 40 °C. Furthermore, this study showed that the system containing Ti/PbO2 as the anode and Al as the cathode electrodes removed arsenic contamination more effectively in the base environment. The performance of arsenic removal was directly related to current intensity, pH, and time. Nevertheless, time elapse played a negative factor due to the corrosion of the electrodes' surface and the dissolution of floating materials in the solution. With the surge of arsenic concentration from 100 to 300 mg/L, the arsenic removal efficiency increased from 61.9 to 98.5 percent, where the maximum removal efficiency due to the rise of the current intensity was 84.16 percent. The sono-electrocoagulation method reduced the risk of carcinogenic and non-carcinogenicity from 5.15E-03 to 7.73E-05 and 26.71 to 0.40. Accordingly, it was found that a combination of ultrasonic and electrocoagulation processes is a promising approach for arsenic removal., (Copyright © 2022. Published by Elsevier Inc.)

Mesoporous silica (MCM-41) is widely used as a supporting material due to its large specific surface area and good stability, but it cannot remove heavy metals due to the lack of adsorption active sites. In this study, the MCM-41 (a mesoporous SiO 2 material) decorated with iron and magnesium oxide (Fe/Mg-MCM-41) was found to be an excellent adsorbent to remove arsenic(V) from water. FTIR, BET, TEM-EDS, XRD, XPS, etc. were applied for characterization analysis. Adsorption isotherms were fitted well by the Langmuir model and the experimental maximum adsorption capacity of Fe/Mg 4 -MCM-41 (magnesium accounts for 4%) was 71.53 mg/g at pH = 3. Thermodynamics analysis suggested exothermic nature of adsorption behavior. Kinetic process was well described by the pseudo-second-order model and adsorption rate was controlled by intraparticle diffusion and film diffusion. Moreover, the adsorption behavior of As(V) onto Fe/Mg 4 -MCM-41 was investigated under different reaction conditions, such as pH, temperature, Mg-doping and competing ions. The results showed that loading a certain amount of magnesium can significantly improve arsenic removal efficiency. Additionally, Fe/Mg 4 -MCM-41 exhibits high arsenic(V) removal in the wide pH range of 3-10. The Fe/Mg 4 -MCM-41 can be regenerated and used after four consecutive cycles. The high arsenic(V) sorption capacity, wide range of pH applications, ability to regenerate, and reusability of Fe/Mg 4 -MCM-41 confirmed that this adsorbent is promising for treating As-contaminated wastewater., 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 © 2022 Elsevier B.V. All rights reserved.)

As(III) removal from groundwaters is challenging because of its neutral charge and low surface affinity under circumneutral pH conditions. In this work, we investigate the influence of Ca 2+ and Mg 2+ on the removal of As(III) by a redox active polyvinylferrocene (PVF) functionalized electrode in a modified double potential step chronoamperometry (DPSC) setup. In the absence of divalent cations, nearly 90% As(III) removal is achieved over ten continuous cycles by single-pass DPSC, even in the presence of competing anions, however the presence of divalent cations at concentrations ≥ 1.25 mM significantly inhibits As(III) removal. The divalent cations enhance arsenic removal in the first (removal) step but suppress electrode regeneration in the 2 nd step. Our results suggest that Ca 2+ /Mg 2+ either acts as a bridge between the electrode surface and As anions or the sorption of Ca 2+ /Mg 2+ increases the positive charge on the electrode surface thereby facilitating As(V) sorption. We show that effective electrode regeneration can be achieved using an NaOH wash however the overall complexity of the process increases. Overall, we conclude that the influence of divalent cations on As removal by electro-sorption processes needs to be taken into consideration for application of this technology for real groundwater treatment., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Iron manganese oxide resources are widely derived from the geological structure, and their combinations play an important role in the migration and transformation of arsenic. Iron oxide and manganese oxide exist generally in a mixed state in Fe-Mn oxides synthesized via the well studied co-precipitation methods using potassium permanganate and manganese/iron sulfates. Herein, a newly designed Fe-Mn-O compositing oxide with Fe-MnO 2 , Mn-Fe 2 O 3 , (Fe 0.67 Mn 0.33 )OOH solid solution and FeOOH as the main components, simply through solvent-free mechanical ball milling pyrolusite (MnO 2 ) and ferrihydrite (FeOOH) together has been reported. Atomic-scale integrations by doping Fe and Mn with each other were detected and an adsorption-oxidation bifunctionality was achieved, where Fe-doped MnO 2 served as oxidizer for As(III) and amorphous/ground FeOOH acted as adsorbent first for As(III) and then As(V) from the oxidization. The maximal adsorption for As(III) could reach 44.99 mg/g and over 82.5% of As(III) was converted to As(V). More importantly, high removal ability of arsenic worked in a wide pH range of 2-10.5%, and 87.2% of its initial adsorption-oxidation capacity could be kept even after 5-cycles reuse for treating 20 mg/L As(III) with a dosage at 1 g/L. Together with the enhanced adsorption capacity by the milled FeOOH, surface electron transfer efficiency of the developed Fe-MnO 2 surrounded with Mn-Fe 2 O 3 has been studied for the first time to understand the oxidization effect to As(V). Besides the environment-friendliness of ball milling method, the prepared sample is quite stable without noticeable metal release into solution. Mechanism studies of arsenic removal by the as-prepared Fe-Mn-O oxide provide a new direction for improving the oxidation efficiency of MnO 2 to As(III) based on the widely available cheap Mn and Fe oxides, contributing to the development of advanced oxidization process in the treatment of waste water., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The function of biochar (BC) as an eco-friendly adsorbent for environmental remediation is gaining much attention. However, the pristine BC had limited abilities for the removal of As (III, V). Towards this issue, this study synthesized biochar/micro-nanosized α-MnO 2 (BM) composites with different mass ratios of biochar to MnO 2 . Comprehensive characterizations confirmed the successful loading of micro-nanosized α-MnO 2 onto the BC surface and the obvious specific surface area enhancement (7.5-13.5 times) of BM relative to BC. BM composites exhibited 5.0-13.0 folds higher removal capacity for As (III, V) than pristine BC since the composites gave full play to the oxidation contributed by micro-nanosized α-MnO 2 substrate and adsorption functions provided by the Mn-OH, BC-COOH, and BC-OH functional groups. Moreover, BM was well reused maintaining a relatively high removal efficiency for As (III, V). Regardless of reaction time and initial As (III) concentration (C 0 ), the removal of As (III) by pristine BC was negligibly contributed by the oxidized As (V) remaining in solutions, with the relative contribution <15.0%. For the BM composites, relative contribution of adsorbed As (III, V) dominated over that of oxidation to mobile As (V) remaining in solution, and exhibited the decreasing trend with increasing C 0 . These findings demonstrated BM as a promising candidate in remediating As (III, V)-polluted water, and provide mechanistic insights into the role of oxidation and adsorption in As (III, V) removal., 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 © 2021 Elsevier B.V. All rights reserved.)

An integrated process of filtration and electrosorption was first applied to enable high-performance arsenic removal for groundwater remediation. An active manganese dioxide-rice husk biochar composite (active BC) filter was utilized for oxidization of As(III) to As(V) and initial removal of As(III, V). Subsequently, electrosorption by capacitive deionization (CDI) was applied as a posttreatment to improve arsenic removal. The active BC approach exhibited fast removal rates of 0.75 and 0.63 g mg -1 h -1 and high maximum removal capacities of 40.76 and 48.15 mg g -1 for As(III) and As(V), respectively. Importantly, column experiments demonstrated that the arsenic removal capacity in the active BC filter was 2.88 mg g -1 , which was 72 times higher than that of BC. The results were due to the high efficiency (94%) of redox transformation of As(III) to As(V). The electrosorptive removal of arsenic was further controlled by changing the voltage in CDI. With a charging step of 1.2 V, the total arsenic concentration can be reduced to 0.001 mg L -1 with a low energy consumption of 0.0066 kW h m -3 . Furthermore, the integrated system can remove As from real groundwater to achieve the World Health Organization guideline value for drinking water quality., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this study, the effective removal of organoarsenic by the combined process of "chlorination + Fe(II)" was achieved. Chlorine could effectively degrade roxarsone (ROX) over pH from 5 to 10. The fitting results of acid-base protonation model proved that the degradation of ROX was mainly attributed to the reaction of HOCl and deprotonated ROX. The transformation of arsenic species conformed to the fitting results of two-channel kinetic model, in which 32.4% of ROX was oxidized to As(V) via electron transfer pathway (ii) and the rest was converted into monochloro-ROX via electrophilic substitution pathway (i). Humic acid inhibited the degradation of ROX due to the competitive consumption of chlorine and the restraint on the pathway ii. Subsequently, an enhanced removal of total arsenic achieved after chlorination, due to that the generating As(V) and monochloro-ROX were easier adsorbed compared with ROX, over 97.8% of total arsenic was removed by ferric (oxyhydr)oxides which in-situ formed from the oxidation of Fe(II). Additionally, toxicity studies indicated that the acute toxicity was significantly eliminated by adding Fe(II) after chlorination, likely due to the removal of As(V) and chlorinated products. Furthermore, organoarsenic was also effectively removed by the combined process of "chlorination + Fe(II)" in real water., (Copyright © 2021. Published by Elsevier B.V.)

Arsenic contamination is a global problem, as it affects the health of millions of people. For this study, data-driven artificial neural network (ANN) software was developed to predict and validate the removal of As(V) from an aqueous solution using graphene oxide (GO) under various experimental conditions. A reliable model for wastewater treatment is essential in order to predict its overall performance and to provide an idea of how to control its operation. This model considered the adsorption process parameters (initial concentration, adsorbent dosage, pH, and residence time) as the input variables and arsenic removal as the only output. The ANN model predicted the adsorption efficiency with high accuracy for both training and testing datasets, when compared with the available response surface methodology (RSM) model. Based on the best model synaptic weights, user-friendly ANN software was created to predict and analyze arsenic removal as a function of adsorption process parameters. We developed various graphical user interfaces (GUI) for easy use of the developed model. Thus, a researcher can efficiently operate the software without an understanding of programming or artificial neural networks. Sensitivity analysis and quantitative estimation were carried out to study the function of adsorption process parameter variables on As(V) removal efficiency, using the GUI of the model. The model prediction shows that the adsorbent dosages, initial concentration, and pH are the most influential parameters. The efficiency was increased as the adsorbent dosages increased, decreasing with initial concentration and pH. The result show that the pH 2.0-5.0 is optimal for adsorbent efficiency (%)., (Copyright © 2021 Elsevier Inc. All rights reserved.)

This study reports the effects of an external voltage (0 V, 0.4 V and 0.9 V) on soil arsenic (As) release and sequestration when amended with organic carbon (NaAc) and inorganic carbon (NaHCO 3 ), respectively, in a soil bioelectrochemistry system (BES). The results demonstrated that although an external voltage had no effect on the As removal capacity in an oligotrophic environment fueled with NaHCO 3, 93.6% of As(III) in the supernatant was removed at 0.9 V with an NaAc amendment. Interestingly, the content of As detected on the electrodes was higher than that removed from the supernatant, implying a continuous release of soil As under external voltages and rapid adsorption onto the electrodes, especially the cathode. In addition, the species of As on the cathode were similar to those in the supernatant (the As(III)/As(V) ratio was approximately 3:1), indicating that the removal capacity was independent of preoxidation. From the viewpoint of electroactive microorganisms (EABs), the relative abundances of the arrA gene and Geobacter genus were specifically enriched at the anode, thus signifying stimulation of the reduction and release of soil As in the anode region. By comparison, Bacillus was particularly abundant at the cathode, which could contribute to the oxidation and sequestration of As in the cathode region. Additionally, specific extracellular polymeric substances (EPSs) secreted by EABs could combine with As, which was followed by electrostatic attraction to the cathode under the effect of an electric field. Furthermore, the formation of secondary minerals and coprecipitation in the presence of iron (Fe) may have also contributed to As removal from solution. The insights from this study will enable us to further understand the biogeochemical cycle of soil As and to explore the feasibility of in situ As bioremediation techniques, combining the aspects of microbial and physicochemical processes in soil bioelectrochemical systems., 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 © 2021 Elsevier B.V. All rights reserved.)

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., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The aim of the present study was: development of activated carbon modified with iron (Fe@AC) and modified with iron and zirconium (Fe-Zr@AC) from the Tectona grandis sawdust (TGS) waste biomass and its potential applicability for the removal of As (III) from contaminated water by batch and column mode. The biomass waste was pre-treated with ferric chloride (FeCl 3 ) and the mixture of FeCl 3 and zirconium oxide (ZrO 2 ) and then pyrolyzed at 500 °C for 2 h. The properties of both bioadsorbents were comprehensively characterized by using Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), Particle Size analysis (PSA), point of zero charge (pH ZPC ), Brunauer-Emmett-Teller (BET) to prove successful impregnation of the Fe and Zr on the surface of AC of TGS. FTIR analysis clearly indicates the Fe and Fe-Zr complexation on biosorbents surface and biosorption of As (III). The results revealed that maximum As (III) removal was achieved 86.35% by Fe-Zr@AC (3 g/L dose, pH-7.0, temperature-25 °C and concentration 0.5 mg/L). However, maximum removal of As (III) was attained ~75% by Fe@AC (with dose-4g/L, pH-7.0, temperature-25 °C and concentration 0.5 mg/L) at the initial concentration of 0.5 mg/L of As (III). Fe-Zr@AC exhibits higher efficiency with q max value 1.206 mg/g than Fe@AC with the q max value 0.679 mg/g for the removal of As(III). While in the column study, Fe-Zr@AC exhibited 98.8% removal at flow rate of 5 mL/min and bed height of 5 cm. Biosorption Isotherm and Kinetics were fitted good with Langmuir isotherm (R 2  ≥ 0.99) and followed pseudo-second-order (R 2  ≥ 0.99). The regeneration study indicates that the prepared biosorbents efficiently recycled up to five cycles. Therefore, Fe@AC and Fe-Zr@AC derived from TGS has been showed to be novel, effective, and economical biosorbent. The collective benefits of easy development, good affinity towards As (III), good separability, reusability, and inexpensive of magnetized Fe@AC and Fe-Zr@AC make it a novel biosorbent. The application of Fe-Zr@AC for the removal of As (III) from the water was very efficient its concentration in the solution after treatment was found below the 10 μg/L as per the guideline WHO., (Copyright © 2021 Elsevier Inc. All rights reserved.)

As the typical hazardous arsenic pollutants, copper smelting flue dust (CSFD) and arsenic sulfide residue (ASR) are produced extensively during copper smelting process, which pose significant pressure on environmental protection and green development of the copper industry. This work proposed an economic, efficient, and applicable approach to treat waste with waste, in which the simultaneous removal and recovery of As from CSFD and ASR were realized by a roasting process, with adding sulfuric acid, at a relatively low temperature (300-350 ℃). The thermodynamic analysis and experiments confirmed that the main phases of As 2 S 3 and S 0 in the ASR were used as a reductant for reducing As(Ⅴ) in the CSFD, and the introduction of sulfuric acid favorably enhanced the thermodynamic driving force and greatly lowered the reaction temperature. The results indicated that removal and behavior of As were highly dependent on the mass ratio of ASR to CSFD, roasting temperature, and H 2 SO 4 dosage. By regulating the parameters, the species As 2 S 3 , As 2 O 5 , and arsenate were all converted to volatile As 2 O 3 , which could be captured and deposited in cold water. In the optimized co-treatment, a satisfied As removal efficiency of 96.12% was achieved, while getting the 97.03% pure As 2 O 3 ., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Although the chitosan-WTRs particulate adsorbent prepared by embedding method has been proved to have arsenic adsorption capacity, the capacity of it is greatly weakened compared with the original water treatment residuals (WTRs). In this study, WTRs and chitosan were used as raw materials to prepare a new kind of adsorbent beads by a homogeneous method. At the same time, in order to enhance the adsorption capacity and reduce the limitation of kinetics, freeze-drying method was chosen to dry the adsorbent. The WTRs-chitosan beads by homogeneous method (WCB) were characterized by SEM, XRD, XPS and other methods. According to the characterization results, there are regularly arranged pores inside the particles, and the iron in the particles mainly exists in the form of amorphous iron oxyhydroxide. According to the results of batch experiment, the pseudo-second-order kinetic model has a higher degree of fit, indicating that the WCB adsorbs As(V) mainly by chemical adsorption. The maximum adsorption capacity estimated from the Langmuir isotherm model is 42.083 mg/g, which is almost same as the WTRs. Weak acid and neutral conditions are conducive to adsorption, while alkaline conditions have a significant inhibitory effect on arsenic adsorption., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Generally, abstracted groundwater is aerated, leading to iron (Fe 2+ ) oxidation to Fe 3+ and precipitation as Fe 3+ -(hydr)oxide (HFO) flocs. This practice of passive groundwater treatment, however, is not considered a barrier for arsenic (As), as removal efficiencies vary widely (15-95%), depending on Fe/As ratio. This study hypothesizes that full utilization of the adsorption capacity of groundwater native-Fe 2+ based HFO flocs is hampered by rapid Fe 2+ oxidation-precipitation during aeration before or after storage. Therefore, delaying Fe 2+ oxidation by the introduction of an anoxic storage step before aeration-filtration was investigated for As(III) oxidation and removal in Rajshahi (Bangladesh) with natural groundwater containing 329(±0.05) µgAs/L. The results indicated that As(III) oxidation in the oxic storage was higher with complete and rapid Fe 2+ oxidation (2±0.01 mg/L) than in the anoxic storage system, where Fe 2+ oxidation was partial (1.03±0.32 mg/L), but the oxidized As(V)/Fe removal ratio was comparatively higher for the anoxic storage system. The low pH (6.9) and dissolved oxygen (DO) concentration (0.24 mg/L) in the anoxic storage limited the rapid oxidation of Fe 2+ and facilitated more As(V) removal. The groundwater native-Fe 2+ (2.33±0.03 mg/L) removed 61% of As in the oxic system (storage-aeration-filtration), whereas 92% As removal was achieved in the anoxic system., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

A laboratory-scale horizontal subsurface flow constructed wetland system was used to quantify the arsenic removal capacity in the treatment of highly acidic, arsenic and metal-rich water: pH ≈ 2, Fe ≈ 57 mg/L, Pb ≈ 0.9 mg/L, Zn ≈ 12 mg/L. The system was operated in two stages, being As ≈ 2.1 mg/L in stage one, and ≈ 3.7 mg/L in stage 2. Limestone and zeolite were employed as main supporting media to build non-vegetated and vegetated cells with Phragmites australis. The system was very effective in the removal of arsenic and iron (> 96%), and lead (> 94%) throughout the whole experimental period, having the four treatment types a similar performance. The main effect of the media type was on the pH adjustment capacity: limestone cells were able to raise the pH to ≈ 7.1, whereas zeolite cells raised it to ≈ 3.8. The contribution of plant uptake to the overall removal of As, Fe and Zn was minor; accounting for less than 0.02%, 0.07% and 0.7% respectively. As such, pollutants were mainly retained in the wetland beds. Our results suggest that limestone is recommended over zeolite as wetland medium mainly due to its neutralization capacity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Arsenic (As) removal is a huge challenge, since several million people are potentially exposed (>10 μg/L World Health Organization guideline limit) through As contaminated drinking water worldwide. Review attempts to address the present situation of As removal, considering key topics on nano-technological and biological process and current progress and future perspectives of possible mitigation options have been evaluated. Different physical, chemical and biological methods are available to remove As from contaminated water/soil/wastes, where removal efficiency mainly depends on absorbent type, initial adsorbate concentration, speciation and interfering species. Oxidation is an important pretreatment step in As removal, which is generally achieved by several media such as O 2 /O 3 , HClO, KMnO 4 and H 2 O 2 . The Fe-based-nanomaterials (α/β/γ-FeOOH, Fe 2 O 3 /Fe 3 O 4 -γ-Fe 2 O 3 ), Fe-based-composite-compounds, activated-Al 2 O 3 , HFO, Fe-Al 2 O 3 , Fe 2 O 3 -impregnated-graphene-aerogel, iron-doped-TiO 2 , aerogel-based- CeTiO 2 , and iron-oxide-coated-manganese are effective to remove As from contaminated water. Biological processes (phytoremediation/microbiological) are effective and ecofriendly for As removal from water and/or soil environment. Microorganisms remove As from water, sediments and soil by metabolism, detoxification, oxidation-reduction, bio-adsorption, bio-precipitation, and volatilization processes. Ecofriendly As mitigation options can be achieved by utilizing an alternative As-safe-aquifer, surface-water or rainwater-harvesting. Application of hybrid (biological with chemical and physical process) and Best-Available-Technologies (BAT) can be the most effective As removal strategy to remediate As contaminated environments., (Copyright © 2020 Elsevier B.V. All rights reserved.)

As(III) oxidation to As(V) is deemed necessary for better arsenic removal, and separation is still the optimal approach for water remediation from As(III). Herein, sulfite (SIV) was adopted to activate MnFe 2 O 4 for simultaneous oxidation and adsorption of As(III) in neutral water. The As(III) removal was more efficient than a peroxidation of As(III) followed by adsorption. The adsorption capacity of MnFe 2 O 4 /S(IV) for As(III) (26.257 mg g -1 ) was much higher than those of MnFe 2 O 4 alone for As(III) (9.491 mg g -1 ) and As(V) (9.142 mg g -1 ). The mechanistic study corroborated that intermediate Mn(III) was the dominant oxidant responsible for rapid oxidation of As(III), and the dual roles of S(IV) as a complexing ligand and a precursor of oxysulfur radicals accelerated the redox cycle of Mn(II)/Mn(III). Moreover, S(IV) enhanced arsenic adsorption by driving more production of monodentate complexes. As(III) can be effectively removed over a wide range of temperatures (283.15-313.15 K) and pH (3-10) with the optimal pH of 7. The effect of coexisting ions and reusability of MnFe 2 O 4 were also investigated. Especially, the superior performance of MnFe 2 O 4 /S(IV) for As(III) removal in various water matrixes may help develop new removal technologies based on active Mn(III) for the water decontamination from As(III)., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The environmental sector has expressed a growing interest in using electrocoagulation (EC) to treat groundwater/wastewater for drinking/recycling purposes. In the EC process, the electro-dissolution of sacrificial metallic anodes through direct application of current/cell potential dissolves the metals, which precipitate as oxides and hydroxides depending on the electrolyte pH. These particles have large surface areas and can remove pollutants by coagulation. The EC process has been considered an alternative technology due to its versatility, efficiency, low cost, and environmental compatibility. Unfortunately, the lack of knowledge about scaling-up this process has limited its implementation at the industrial scale. The aim of this study is to provide a review of the EC process used for removing arsenic and fluoride from groundwater and wastewater. Approximately 80 published studies were reviewed for this paper. The fundamentals of the EC process and importance of its operating conditions, i.e., electrode material, current density, supporting electrolyte, and pH, are reported in this paper. Additionally, overview of floc characterization and energy consumption are also presented. Finally, this paper also discusses the future perspectives., 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 © 2020 Elsevier B.V. All rights reserved.)

Water-soluble polymer based on alkylated chitosan with a quaternary ammonium group (Ch-QAG) was prepared, characterized, and applied to remove arsenate ions from aqueous solution by LPR technique. The arsenic removal was performed by the washing method (WM) and enrichment method (EM). Through the WM, studies of the pH and variation in the concentrations of interferents and arsenate ions were carried out. The effect of the removal of arsenate ions in simulated water was determined from the Camarones River in northern Chile. Ch-QAG showed high affinity for binding arsenate species (99% of removal) at pH 11.0 at a molar ratio of 20:1 polymer: As(V). High selectivity was also observed in the presence of interfering ions such as Cl - , SO 4 2- , and PO 4 3- , resulting in a removal rate over 80% at percentages over 95% for a concentration of 100 mg L -1 of As (V). The maximum retention capacity obtained was 112, 105, and 98 mg g -1 for three load cycles. The retention percentage for simulated water was 46.3% at a concentration of 1300 μ g L -1 . In conclusion, the results presented in this study show that using Ch-QAG with ultrafiltration membranes is a great alternative to remove As (V) at high removal rates., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Over 2 million mostly rural Americans are at risk of drinking water from private wells that contain arsenic (As) exceeding the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 10 micrograms per liter (μg/L). How well existing treatment technologies perform in real world situations, and to what extent they reduce health risks, are not well understood. This study evaluates the effectiveness of household As treatment systems in southern-central Maine (ME, n = 156) and northern New Jersey (NJ, n = 94) and ascertains how untreated well water chemistry and other factors influence As removal. Untreated and treated water samples, as well as a treatment questionnaire, were collected. Most ME households had point-of-use reverse-osmosis systems (POU RO), while in NJ, dual-tank point-of-entry (POE) whole house systems were popular. Arsenic treatment systems reduced well water arsenic concentrations ([As]) by up to two orders of magnitude, i.e. from a median of 71.7 to 0.8 μg/L and from a mean of 105 to 14.3 μg/L in ME, and from a median of 8.6 to 0.2 μg/L and a mean of 15.8 to 2.1 μg/L in NJ. More than half (53%) of the systems in ME reduced water [As] to below 1 μg/L, compared to 69% in NJ. The treatment system failure rates were 19% in ME (>USEPA MCL of 10 μg/L) and 16% in NJ (>NJ MCL of 5 μg/L). In both states, the higher the untreated well water [As] and the As(III)/As ratio, the higher the rate of treatment failure. POE systems failed less than POU systems, as did the treatment systems installed and maintained by vendors than those by homeowners. The 7-fold reduction of [As] in the treated water reduced skin cancer risk alone from 3765 to 514 in 1 million in ME, and from 568 to 75 in 1 million in NJ., Competing Interests: Declaration of competing interest The authors declare that they do not have any conflict of financial interests to this work., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Leaching of the hazardous electric arc furnace (EAF) dust containing mainly zinc ferrite and zinc oxide, accompanied by minor concentrations of arsenic compounds, was investigated using sulfuric acid. In order to reach the maximum recovery of zinc, the leaching solution was adjusted to recover both iron and zinc at their maximum possible values. To obtain a high recovery value of zinc and iron, analyzed by AAS, the optimum leaching condition was found to be the temperature of 90 °C, the sulfuric acid concentration of 3 M, the particle size of 75 μm, the S/L ratio of 1:10 g/mL and the leaching time of 2 h. The percentages of the zinc and iron recovery under the optimum condition were ca. 98.6% and 99.1% respectively, which were verified by a confirmation test and were very close to the predicted values of 100% based on the optimized model, obtained through the software. From the thermodynamics' point of view, it has been found that Zn 2+ is the predominant species (90%) under the leaching condition applied. Moreover, the predominant species of iron are FeSO 4 + , FeHSO 4 2+ , Fe(SO 4 ) 2 - and Fe 3+ in the magnitudes of 65.8%, 25.6%, 4.4% and 4.0%, respectively. According to the kinetic results, the controlling step in the leaching was the chemical reaction at the most of the operating temperatures and times. In order to purify the zinc solution for electrowinning, iron and arsenic were removed through the jarosite formation process as confirmed by the XRD results. The speciation of arsenic in the precipitated jarosite was explored by XPS. Finally, the low concentrations of arsenic (less than 0.1 ppm) and iron (less than 50 ppm) were determined by the ICP analysis., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Iron-modified graphitic carbon nitride (FG materials) was prepared through a simple and cost-effective method using iron oxide and melamine to achieve simultaneous oxidation and adsorption of arsenic. We hypothesized that graphitic carbon nitride oxidizes As(III) to As(V) under light irradiation, and the converted As(V) is adsorbed by the amorphous iron phase on FG materials. FG materials were characterized by X-ray diffraction, Fourier transform infrared spectra, field-emission scanning electron microscopy, specific surface area, ultraviolet-visible light spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy. As(III) was efficiently transformed to As(V) due to the photocatalytic-oxidation ability of graphic carbon nitride under visible and UV light irradiation, the oxidized As(V) was adsorbed by the amorphous iron phases, and As species were removed from the system. The removal efficiency of As(III) decreased from 50%, 41%, and 33% under UV light, visible light and dark, respectively. FG materials exhibited the photocatalytic-oxidation ability and adsorption capacity, and a synergistic effect was observed between graphitic carbon nitride and iron oxide. Removal of As can be achieved even under visible light, confirming the field applicability of low-cost FG materials., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Discharge of treated municipal wastewater containing arsenic (As) may cause adverse effects on the environment and drinking water sources. Arsenic concentrations were measured throughout the treatment systems at two municipal wastewater plants in New Jersey, USA. The efficiency of As removal by ferric chloride and alum coagulants were evaluated. Besides, the effects of suspended solids in the mixed liquor, pH, and orthophosphate (PO 4 3- ) on As removal were investigated. The total recoverable As (TAs) concentrations in the influent and effluent of Plant A were in the ranges of 2.00-3.00 and 1.50-2.30 μg/L, respectively. The results indicated that <30% of the As was removed by the conventional biological wastewater treatment processes. The influent and effluent TAs concentrations at Plant B was below 1.00 μg/L. The bench-scale coagulation results demonstrated for the first time that the coagulation treatment could not effectively remove As from the municipal wastewater to <2.00 μg/L. Very high doses of the coagulants (8 and 40 mg/L of Fe(III) or Al(III)) were required to reduce the TAs from 2.84 and 8.61 μg/L in the primary clarifier effluent and arsenate-spiked effluent samples to <2.00 μg/L, respectively, which could be attributed to the high concentrations of PO 4 3- and dissolved organic matters (DOM) in the wastewater. The protein DOM in wastewater may negatively impact removal efficiencies more than the DOM in natural water, which mainly consists of humic substances. Furthermore, an artificial neural network was constructed to determine the relative importance of different parameters for As removal. Under the experimental conditions, the importance followed the order: coagulant dose>dissolved PO 4 3-  > initial As concentration > pH. The findings of this study will help develop effective treatment processes to remove As from municipal wastewater., 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 © 2020 Elsevier B.V. All rights reserved.)

The purpose of this study is to determine the capacity of four industrial waste materials originate from steelmaking processes and from gas treatment at a thermal power plant to remove As and other contaminants from a leachate from the spoil heap of an abandoned mercury mine. Arsenic removal is faster in the first minutes, then increases only slightly over time reaching equilibrium in 8 hours. As removal efficiency increased with increasing adsorbent concentration. As removal efficiency was found to be 82.7%, 71%, 37.2% and 27.2% for EA, FA, HA and G, respectively, when employing 80 g/dm 3 of adsorbent concentration. The main mechanism of As removal appears to be the results show that Hg and Pb are completely removed using low concentrations of adsorbents regardless of the waste material used in the treatment. FA removed more than 82% of other toxic elements such as Ni, Cu and Cd. EA is the most effective byproduct of the four employed in this study for removing pollutants, while G is the least effective. The present study shows it is possible to carry out an efficient and economical treatment of mine leachate using these byproducts., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, magnetic ordered mesoporous Fe/Ce bimetal oxides (OMICs) were successfully synthesized via the modified sol-gel-based inverse micelle method. The textural/structure properties, surface chemistry and adsorption behavior of OMICs could be easily adjusted by using the calcination temperature. The sintering of samples would decrease the surface area, while expand the pore and crystallite size, which resulted in the formation of highly ordered inner-connected structure. Compared with pure mesoporous iron oxides (MI) and mesoporous cerium oxides (MC), this ordered mesoporous iron-cerium bimetal oxides (OMIC-3, 450 °C) exhibited remarkable arsenic adsorption performance. The maximum adsorption capacities of As(III) and As(V) for OMIC-3 were 281.34 and 216.72 mg/g, respectively, and both As(III)/As(V) adsorption kinetics were well described by the pseudo-second order. The ionic strength and coexisting ions (except SiO 3 2- ) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater.4 3- ) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In the Red River Delta, Vietnam, arsenic (As) contamination of groundwater is a serious problem where more than seventeen million people are affected. Millions of people in this area are unable to access clean water from the existing centralized water treatment systems. They also cannot afford to buy expensive household water filters. Similar dangerous situations exist in many other countries and for this reason there is an urgent need to develop a cost-effective decentralized filtration system using new low-cost adsorbents for removing arsenic. In this study, seven locally available low-cost materials were tested for arsenic removal by conducting batch adsorption experiments. Of these materials, a natural laterite (48.7% Fe 2 O 3 and 18.2% Al 2 O 3 ) from Thach That (NLTT) was deemed the most suitable adsorbent based on arsenic removal performance, local availability, stability/low risk and cost (US$ 0.10/kg). Results demonstrated that the adsorption process was less dependent on the solution pH from 2.0 to 10. The coexisting anions competed with As(III) and As(V) in the order, phosphate > silicate > bicarbonate > sulphate > chloride. The adsorption process reached a fast equilibrium at approximately 120-360 min, depending on the initial arsenic concentrations. The Langmuir maximum adsorption capacities of NLTT at 30 °C were 512 μg/g for As(III) and 580 μg/g for As(V), respectively. Thermodynamic study conducted at 10 °C, 30 °C, and 50 °C suggested that the adsorption process of As(III) and As(V) was spontaneous and endothermic in nature. A water filtration system packed with NLTT was tested in a childcare centre in the most disadvantaged community in Ha Nam province, Vietnam, to determine arsenic removal performance in an operation lasting six months. Findings showed that the system reduced total arsenic concentration in groundwater from 122 to 237 μg/L to below the Vietnam drinking water standard of 10 μg/L., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report for the very first time, development of a dual functional nanocomposite to perform as an optical probe as well as removal system for As(III) from ground water. Upon suitable thiolation using dithiothreitol (DTT), the Fe 3 O 4 (core)-Au(shell) nanocomposite (DTT-Fe 3 O 4 @Au) has been fabricated that can detect As(III) in aqueous solution with significantly low limit of detection and holds potential for selective removal of As(III) from water owing to its magnetic core. Due to high affinity of -SH groups for As(III), the nanoparticles undergo aggregation in the presence of As(III), resulting in a significant decrease in absorbance, yielding the limit of detection (LOD) as 0.86 ppb, which is much lower than the World Health Organisation (WHO) recommended threshold value of 10 ppb. UV-vis spectroscopy in conjunction with dynamic light scattering and electron microscopy techniques have further elaborated the detailed interaction between As(III) and DTT-Fe 3 O 4 @Au nanocomposite regarding their size dynamics and solution behaviour during the interaction. Moreover, ca.70% removal of As(III) from aqueous solution by DTT-Fe 3 O 4 @Au has been observed by ICP-MS measurement strengthening the potential of this nanocomposite as a dual-functional probe and filter., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Improper disposal of arsenic-rich biomass and the lack of efficient methods to treat it may cause contamination in the environment. We developed an efficient method for arsenic (As) removal and biomass reduction of As-rich biomass of the As-hyperaccumulator Pteris vittata by coupling ethanol extraction with anaerobic digestion. This study assessed As partitioning among the three phases (gas, liquid and solid) after anaerobic digestion of P. vittata biomass. Biomass with and without As was first extracted with ethanol. Ethanol extraction removed ~93% As, with remaining As concentration at 197 mg kg -1 . The extracted biomass was then digested at 35 °C under anaerobic conditions for 35 d. Arsenic in the digested biomass was reduced by 89%, with remaining As concentration at 60 mg kg -1 . In addition, anaerobic digestion reduced the biomass by 64-71% and decreased the volatile solids content from 94 to 15-18%. Methane production was 145 and 160 L N CH 4 /kgVS after 35 d for As-rich and control biomass, respectively. As a final step, As concentration in anaerobic digestate supernatant was reduced to 0.26 mg L -1 by As-Mg precipitation. Overall, coupling ethanol extraction with anaerobic digestion decreased As concentration in P. vittata biomass from 2665 to 60 mg kg -1 , or by 98%. At this level (<100 mg As kg -1 ), P. vittata biomass can be considered a safe material based on USEPA regulations. Effective As removal from P. vittata biomass prior to disposal improves the phytoremediation process and lowers biomass transport and landfill disposal costs., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Cellulose acetate (CA) and cellulose acetate phthalate (CAP) were used as additives (1 wt%, 3 wt%, and 5 wt%) to prepare polyphenylsulfone (PPSU) hollow fiber membranes. Prepared hollow fiber membranes were characterized by surface morphology using scanning electron microscopy (SEM), surface roughness by atomic force microscopy (AFM), the surface charge of the membrane was analyzed by zeta potential measurement, hydrophilicity by contact angle measurement and the functional groups by fourier transform infrared spectroscopy (FTIR). Fouling resistant nature of the prepared hollow fiber membranes was evaluated by bovine serum albumin (BSA) and molecular weight cutoff was investigated using polyethylene glycol (PEG). By total organic carbon (TOC), the percentage rejection of PEG was found to be 14,489 Da. It was found that the hollow fiber membrane prepared by the addition of 5 wt% of CAP in PPSU confirmed increased arsenic removal from water as compared to hollow fiber membrane prepared by 5 wt% of CA in PPSU. The removal percentages of arsenic with CA-5 and CAP-5 hollow fiber membrane was 34% and 41% with arsenic removal permeability was 44.42 L/m 2 h bar and 40.11 L/m 2 h bar respectively. The increased pure water permeability for CA-5 and CAP-5 hollow fiber membrane was 61.47 L/m 2 h bar and 69.60 L/m 2  h bar, respectively., (Copyright © 2019 Elsevier B.V. All rights reserved.)