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Graphical abstract Highlights • The q max of MNCA are 131.00 mg g−1 (AsIII) and 119.58 mg g−1 (AsV). • Surface layer of MNCA significantly affect its arsenic removal performance. • Flexible and non-covalent surface layer can improve arsenic anion diffusion. • More than 80% of arsenic can be removed from blood by MNP@CTAB-BSA in 150 min. Abstract Magnetic nano capture agent (MNCA)-based magnetic separation can remove heavy metals from blood efficiently and safely. It has been considered as the next-generation therapy for heavy metal intoxication. In this work, we report the first use of MNCA to remove arsenic (As) with high efficiency from blood. MNCA with a flexible, non-covalent and biocompatible surface layer has been synthesized by packaging cetyltrimethylammonium bromide (CTAB) and bovine serum albumin (BSA) together with oleic acid coated magnetic iron oxide nanoparticles (MNP@OA) via Van der Waals force. This surface layer enhances arsenic anion diffusion from the surface to the binding sites, leading to increased arsenic removal performance of MNCA. The adsorption capacities of BSA and CTAB enfolded MNP@OA (MNP@CTAB-BSA) for As (III) and As (V) are 131.00 mg g−1 and 119.58 mg g−1, respectively. 89.02% of As (III) and 81.78% of As (V) are removed from blood using MNP@CTAB-BSA, and the residual concentrations of As (III) and As (V) in blood decrease from 400.00 μg L−1 to 43.93 μg L−1 and 72.88 μg L−1, respectively. The as-synthesized MNP@CTAB-BSA shows excellent biocompatibility. Under operation condition, only 0.80% of hemolysis and 1.64% of plasma protein adsorption are induced by MNP@CTAB-BSA, and the cell viability of peripheral blood mononuclear cells (PBMCs) is more than 95.53%. This study paves a fast, safe and effective way for arsenic intoxication therapy. [ABSTRACT FROM AUTHOR]

Abstract Sulfidogenic process using sulfate-reducing bacteria (SRB) has been used to remove arsenite from the arsenic-contaminated waters through the precipitation of arsenite with sulfide. However, excessive sulfide production and significant pH increase induced by sulfate reduction result in the formation of the mobile thioarsenite by-products and the inefficiency and instability of arsenite removal, especially when the arsenite level fluctuates. In this study, we proposed a novel sulfidogenic process driven by sulfur reducing bacteria (S0RB) for the arsenite removal under acidic conditions. In a long term experiment, efficient sulfide production (0.42 ± 0.2 kg S/m3-d) was achieved without changing the acidic condition (pH around 4.3) in a sulfur reduction bio-reactor. With the acidic sulfide-containing effluents from the bio-reactor, over 99% of arsenite (10 mg As/L) in the arsenic-contaminated water was precipitated without the formation of soluble thioarsenite by-products, even in the presence of excessive sulfide. Maintaining the acidic condition (pH around 4.3) of the sulfide-containing effluent was essential to ensure the efficient arsenite precipitation and minimize the formation of thioarsenite by-products when the arsenite to sulfide molar ratios ranged from 0.1 to 0.46. An acid-tolerant S0RB, Desulfurella , was found to be responsible for the efficient dissimilatory sulfur reduction under acidic conditions without changing the solution pH significantly. The microbial sulfur reduction may proceed through the direct electron transfer between the S0RB and sulfur particles, and also through the indirect electron transport mediated by electron carriers. The findings of this study demonstrate that the proposed sulfidogenic process driven by S0RB working under acidic conditions can be a promising alternative to the SRB-based process for arsenite removal from the arsenic-contaminated waters. Graphical abstract Image 1 Highlights • Efficient sulfide production by sulfur reducing bacteria (S0RB) was achieved at pH ∼4.3. • The pH increase during the microbial sulfur reduction was insignificant. • Arsenite was efficiently precipitated by sulfide at varied As/S molar ratios. • Maintaining acidic conditions is essential to minimize the thioarsenite formation. [ABSTRACT FROM AUTHOR]

Abstract Facile fabrication of magnetic metal-organic frameworks (MOFs) using a direct epitaxial approach for eliminating arsenic from water is highly desirable. Herein, a two-step solvothermal method of elegant design is proposed to synthesize Fe 3 O 4 @UiO-66. Such resulting composite was systematically characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption-desorption isotherms, and thermogravimetric analysis (TGA). Results clearly reveal that this novel composite exhibits a unique core-shell structure with high specific surface area and plentiful micropores as well as good thermal stability. Specifically, batch adsorption data for arsenate demonstrate that a pseudo-second order kinetic model (R 2 = 0.9996) better describes this adsorption process than a pseudo-first order model (R 2 = 0.8582), revealing the chemical interaction between the composite and arsenate. The Freundlich model with better coefficient (R 2 = 0.9566) further verified multi-layer heterogeneous adsorption, which may be ascribed to the unique core-shell structure of this composite (Fe 3 O 4 @UiO-66). Its excellent adsorption performance for arsenate (73.2 mg (As) g−1 (adsorbent)) is comparable to most MOFs-containing adsorbents but is also magnetic, allowing for ready separation of the composite from aqueous solution. Given this combination of qualities, this new composite could offer a promising alternative for wastewater remediation. Graphical abstract Facile fabrication of magnetic composite based on UiO-66 for efficient removal of As(V) from water with easy separation after the adsorption. Image 1 Highlights • Magnetic Fe 3 O 4 @UiO-66 composite was fabricated using a direct epitaxial method. • The core-shell structure had high specific surface and abundant micro-/mesopores. • Adsorption capacity for As(V) was good and separation from aqueous solution easy. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate the application of a steel waste, basic oxygen furnace sludge (BOFS), rich in iron, to treat water contaminated with elevated arsenic and sulfate concentrations. In the first step, three doses (10, 60, and 80 g L−1) of BOFS were tested to investigate the removal of As(III) and As(V) (67 mg L−1) and sulfate (3700 mg L−1) separately from an aqueous solution. In the second step, the efficacies of BOFS (10 g L−1) and commercial ZVI (5 g L−1) were compared to simultaneously remove arsenic and sulfate. The pH of the feed solution was adjusted to 2.5 and monitored during the experiment. The use of BOFS achieved arsenic removal up to 92% and sulfate removal of nearly 40% after 72 h of contact time. Use of BOFS also increased the solution pH to 12. Similar removal levels were achieved with both BOFS and ZVI. These results confirm the potential application of BOFS to remove high arsenic and sulfate concentrations from acidic solutions. The data obtained here should be used as a basis for further studies on the remediation of acid mine drainage with high concentrations of arsenic and sulfate using an abundant and low-cost steel waste. [ABSTRACT FROM AUTHOR]

To reduce sludge volume, Mg-Al layered double hydroxide (LDH) was used to remove pollutants from mine wastewater. Mg-Al LDH can remove both cations and anions from mine wastewater via co-precipitation and anion exchange mechanisms, respectively. We herein investigated the difference in removal efficiencies between Mg-Al LDH and Ca(OH)2. Initial As and Fe concentrations of 8.4 and 308.6 mg/L led to final concentrations of <0.001 and 15.4 mg/L, respectively, when 5 g/L LDH with an Mg/Al molar ratio of 2:1 was employed. This suggests that As was removed in the form of , which exchanged with intercalated in the Mg-Al LDH structure, while Fe was removed by the formation of Fe-Al LDH via co-precipitation. In contrast, treatment with 5 g/L Ca(OH)2 gave As and Fe concentrations of 0.1 and <0.01 mg/L, respectively. Thus, under Ca(OH)2 treatment, As is removed by the co-precipitation of arsenate with the formation of ferric oxyhydroxide (FeO(OH)), while Fe is removed by co-precipitation of the formed Fe(OH)3. The sludge volume obtained using Mg-Al LDH was approximately ten times lower than that obtained when using Ca(OH)2. [ABSTRACT FROM AUTHOR]

Abstract This study involved fabricating biogenic Fe(III) flocs enriched from municipal sludge using microbial nitrate-dependent anaerobic Fe(II)-oxidizing (NAFO) processes. The research focused on bacterial community compositions and physicochemical properties of the biogenic Fe(III) flocs and their ability to adsorb arsenic (As). High-throughput sequencing analysis showed that significant microbial succession occurs in the raw sludge after the NAFO processes. The predominant bacterial communities in the biogenic Fe(III) flocs included Rhodanobacter , Parvibaculum , Gemmatimonas and Segetibacter genera. Microscopic and spectroscopic analyses included scanning electron microscopy - energy disperse spectroscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. These tests indicated that biogenic Fe(III) flocs were a mixture of NAFO bacteria and nanosized, poorly crystalline Fe(III) oxide particles. Batch experiments showed that after 120 min of reaction time, more than 95% of As(III) and As(V) (at an initial concentrations of 0.25 mg/L) were effectively removed with 120 ppm biogenic Fe(III) flocs. In addition, biogenic Fe(III) flocs removed As more effectively than abiotic Fe(III) flocs. These findings indicated that biogenic Fe(III) flocs produced from municipal sludge using NAFO processes performed well in removing As. Highlights • Biogenic Fe(III) flocs were produced from sludge by NAFO processes. • A significant microbial succession occurs in sludge after NAFO processes. • Biogenic Fe(III) flocs are excellent at removing inorganic arsenic. [ABSTRACT FROM AUTHOR]

Highlights • Arsenic removal from lead-zinc smelter ash by NaOH-H 2 O 2 leaching was investigated. • More than 98% of arsenic was extracted from the smelter ash. • The leaching process belonged to diffusion-controlled type in Avrami model. • The apparent activation energy of the leaching process was 16.03 kJ/mol. Abstract The safe treatment of smelter ash with high arsenic is of great importance both for environmental protection and resource comprehensive utilization. In this study, arsenic removal from lead-zinc smelter ash by NaOH-H 2 O 2 leaching was studied. The effects of different operating parameters on the leaching rate of arsenic and leaching kinetics were investigated based on thermodynamic calculation. The results indicate that NaOH concentration and H 2 O 2 addition have significant effects on the leaching rate of arsenic. The optimum conditions were established as: liquid-solid ratio, 10:1; NaOH concentration, 3 mol/L; H 2 O 2 concentration, 2.4%; leaching time, 2 h; and leaching temperature, 75 °C. Under these conditions, the leaching rate of arsenic was as high as 98.17%. The kinetic study reveals that the arsenic leaching process is in accordance with the diffusion-controlled type in the Avrami model, and the apparent activation energy is 16.03 kJ/mol. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the efficient removal of As(V) from contaminated water using enhanced coagulation by Fe-Mn bimetal nano-oxides in combination with poly-ferric chloride (PFC) and poly-aluminum chloride (PAC). The effects of coagulant dose, initial pH, initial As(V) concentration, Fe-Mn nano-oxide dose and flocs properties were investigated. The results showed that the combination of coagulants and nano-oxides significantly increased the As(V) removal efficiency in the optimal coagulants doses (25 mg/L). The As(V) removal efficiencies for PAC and PFC were 82.93% and 88.22% and for PFC + Fe-Mn and PAC + Fe-Mn were increased to 96.83% and 98.26%, respectively. The residual As(V) concentration was decreased to ˂10 μg/L in the presence of Fe-Mn nano-oxides. The best removal efficiencies for PAC + Fe-Mn and PFC + Fe-Mn were in pH 7 and 9, respectively. Based on FESEM - EDX analysis, the combined floc formation by coagulants - nano-oxides and the existence of Fe, Mn and As elements in the precipitated flocs was confirmed, and the PFC + Fe-Mn flocs were more uniform and bigger than PAC + Fe-Mn flocs. Total Fe and Al residual concentrations in optimum dose of PAC + Fe-Mn and PFC + Fe-Mn were 0.15 and 0.25 mg/L and Cl− residue concentrations were 6.87 and 4.72 mg/L, respectively. Therefore, the combination of Fe-Mn bimetal nano-oxides with PFC and PAC coagulants can be a suitable option to improve the removal of As(V) from the contaminated water resources. Graphical abstract Image 1 Highlights • Efficient As(V) removal investigated by enhanced coagulation with Fe-Mn nano-oxide. • ≥96% As(V) was removed by combination of PFC + Fe-Mn and PAC + Fe-Mn. • Residual As(V) concentration decreased to <10 μg/L in the presence of nano-oxides. • Combined flocs formation by coagulants – nano-oxides was confirmed by FESEM – EDX. [ABSTRACT FROM AUTHOR]

In this work, the removal of arsenic (III) using zeolite/chitosan nanocomposite membranes was studied and characterized using scanning electron microscopy (SEM), atomic force microscope (AFM), etc. The water contact angle of the membrane decreased from 74.2 to 59.2° and the porosity of the prepared membranes increased from 20.38 to 45.81% with an increase in the concentration of zeolite. The rejection of arsenic (III) increases with increase in the zeolite loading for 500 and 1000 µg/L; but at 100 and 150 µg/L, the trend was opposite. The membrane with 1.0 [Chi-Z (1.0)] and 1.25 [Chi-Z (1.25)] wt% zeolite showed the highest rejection (>94%) for 1000 µg/L concentration of arsenic trioxide aqueous solution. [ABSTRACT FROM AUTHOR]

Highlights • Fluoride and arsenic removal from real groundwater by electrocoagulation. • Aluminum electrodes in a continuous filter-press reactor with three cell stack. • Hydrated silica species in groundwater facilitate the removal of F and As. • XRD and FTIR analyses indicated that flocs are composed by aluminum silicates. • Fluoride and arsenic concentrations after EC met the WHO standard. Abstract An electrocoagulation (EC) process to remove fluoride and arsenic from groundwater (fluoride 5.5 mg L−1, arsenic 50.4 µg L−1, hydrated silica 132 mg L−1, sulfate 40 mg L−1, nitrate 6.7 mg L−1, phosphate 0.55 mg L−1, hardness 23 mg L−1, alkalinity 59.0 mg L−1, pH 8.5 and conductivity 824.5 µS cm−1) was investigated. The EC was carried out in a filter-press flow reactor, containing a three-cell stack equipped with aluminum electrodes. The influence of current density (j), mean linear flow rate in the EC reactor (u r) and the co-existing ions on the fluoride and arsenic removal efficiencies was analyzed. All EC tests, performed at 0.23 ≤ u r ≤ 0.93 cm s−1 and 5 ≤ j ≤ 7 mA cm−2, satisfied the World Health Organization (WHO) standard for fluoride (C F - ≤ 1.5 mg L−1). The EC tests that satisfied the WHO standard for arsenic (C As ≤ 10 µg L−1) were at 0.23 cm s−1 and 6 ≤ j ≤ 7 mA cm−2. Spectroscopic analyses on aluminum flocs showed that these are mainly composed of aluminum silicates. Fluoride replaces a hydroxyl group from aluminum flocs and arsenates adsorb on aluminum aggregates. The best EC test in terms of energy consumption (6.7 kWh m−3) was obtained at 0.23 cm s−1 and 6 mA cm−2. [ABSTRACT FROM AUTHOR]

The present study deals with the effect of two different conditions for modification of raw granular activated carbon (GAC) with FeCl3 under acidic granular activated carbon (AGAC) and basic granular activated carbon (BGAC) conditions for removal of arsenic – As(V) – from aqueous solution. X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller (BET) were used for structural properties. Obtained images show that for raw GAC most of the peaks are related to SiO2 and graphite, but, for AGAC related to Fe2O3, Fe3O4, and SiO2, and for BGAC related to Fe3O4 and hydrogen aluminum silicate. Surface area and total pore volume of raw GAC > AGAC > BGAC. Kinetics study for arsenic removal by raw GAC and BGAC obeyed pseudo-first-order model, but, AGAC obeyed pseudo-second-order model. Isotherm study showed that raw GAC has a good fit with Langmuir model, and AGAC and BGAC have a good fit with Freundlich model. The adsorption capacity of AGAC, BGAC, and raw GAC (As(V) concentration = 0.3 mg/L) was 22.7, 18.33, and 14.35 mg/g, respectively. It was concluded that modified raw GAC under the acidic condition had better than basic condition. [ABSTRACT FROM AUTHOR]

In present work, controlled TiO2-ZnO ratio nanostructure composite powders synthesized via co-precipitation method from zinc acetate and titanium tetrachloride as starting materials were obtained. Samples with different Ti/Zn precursor ratios were prepared for the study. Photocatalytic activities of the particles were evaluated under UV and visible light sources, using both arsenic-laced solution and industrial copper smelting wastewater. Results generally show that nanopowder composites are formed. Samples with Ti/Zn precursor ratio of 90:10 and 50:50 showed considerable photocatalytic activities leading to up to 90% arsenic degradation under UV and visible light irradiation; however, compared experientially made a solution in the laboratory, the industrial wastewaters resulted in less arsenic photodegradation. [ABSTRACT FROM AUTHOR]

Highlights • Arsenic and iron concentrations were removed in microbial fuel cell systems. • Biofilms on electrodes were tolerant to low pH and high concentrations of metals. • pH neutralization favored the formation of Fe minerals, and subsequent As removal. • XRD analysis suggests the precipitation of Amorphous Fe minerals. [ABSTRACT FROM AUTHOR]

Abstract Ferric hydroxide precipitation and flocculation is the most commonly used method for the removal of arsenic in water treatment. However, citrate often interrupts the precipitation of ferric hydroxides and thus affects arsenic removal. To date, the mechanisms controlling the effects of citrate on arsenic removal with ferric hydroxide flocculation and precipitation at very low citrate-to-Fe molar ratios are not well understood. Herein, we report a new mechanism by which citrate inhibits arsenic removal using ferric hydroxide. At a substoichiometric citrate-to-Fe molar ratio of 0.28, citrate forms a high-molecular-weight Fe−citrate (Fe 4 Cit) species. The optimized structure of the Fe 4 Cit species was obtained by the density functional theory calculation. To the best of our knowledge, this study is the first to report the formation and to identify the structure of dominant Fe–citrate species at a very low citrate-to-Fe molar ratio. Graphical abstract Image 1 Highlights • Citrate at substoichiometric concentrations inhibits ferric hydroxide precipitation. • This effect results in hindered arsenic removal at low citrate-to-Fe molar ratios. • Inhibition effect by citrate is due to the formation of Fe–citrate species. • Structure of Fe–citrate species is identified as [Fe 4 O 13 H 3 Cit·2H 2 O]+. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Arsenic imprinted polymer synthesized for the detoxification drinking water. • 1-Vinylimidazole and methacrylic acid were to synthesize arsenic imprinted polymer. • Synthesized imprinted polymer has excellent selectivity for arsenic then other competitive ion. • Taguchi method was applied to optimize the process parameters for adsorption of arsenic on As-IIP. Abstract In the present study, As3+ imprinted polymer as an active detoxification material has been synthesized through microwave assisted preparation method. By inducing the microwave radiation during the polymerization process decreases the reaction time to about 10 folds than conventional method. The imprinted polymer is one of the best possible techniques for the removal of arsenic, and various other contaminants from drinking water. The SEM and FTIR analyses have been conducted to clarify microstructure, surface morphology and size distribution of the synthesized imprinted polymer. The main parameters affecting the pzc, pH, agitation time, shaking speed, concentration, the temperature of adsorbent and percent of sorption, have been examined and optimized by Taguchi design. Taguchi L9 orthogonal array was employed to optimize the important factors versus % sorption values with nine experimental runs at 3 levels. Moreover, to understand the reaction phenomenon Langmuir and Freundlich isotherms, kinetic models and thermodynamics of adsorption process were calculated. The relative selectivity coefficient of imprinted polymer for As3+/Cd2, As3+/Zn2+, As3+/Ni2+were respectively 45.93, 131.01, 262.63 times greater than for non-imprinted polymer. The limit of detections (LOD) and limit of quantification (LOQ) of the proposed procedure for As3+ ion was found to be 1.0 µg/L and 3.3 µg/L for the As3+ ion respectively, with the relative standard deviation (RSD) of 4%. The excellent adsorption performance along with their low cost and convenient synthesis makes this range of adsorbent highly promising for commercial applications in drinking water purification and water treatment. [ABSTRACT FROM AUTHOR]

Abstract The simultaneous removal of hydrated silica, fluoride and arsenic from deep well water (hydrated silica 72 mg L − 1 , fluoride 4.4 mg L − 1 , arsenic 106.2 μg L − 1 , sulfate 50 mg L − 1 , phosphate 0.99 mg L − 1 , pH = 8.2 and conductivity 659 μS cm − 1 ) by electrocoagulation (EC) was investigated. The EC was performed in a continuous electrochemical reactor using aluminum plates as sacrificial anodes coupled directly to a jar test device. The effect of current density (4 ≤ j ≤ 8 mA cm−2) and mean linear flow rates in the EC reactor (0.057 ≤ u ≤ 0.57 cm s−1) on the hydrated silica, fluoride, and arsenic removal efficiencies was analyzed. The abatement of hydrated silica was obtained at 8 mA cm−2 and 0.057 cm s−1, while the residual concentrations of F− and As after the same electrolysis were 0.19 mg L − 1 and 9.8 μg L − 1 , satisfying the WHO guidelines for F− (≤1.5 mg L − 1 ) and As (≤10 μg L − 1 ). Spectroscopic analyses on aluminum flocs revealed that they are predominantly composed of aluminum silicates. Arsenates adsorb on aluminum flocs and fluoride replaces a hydroxyl group from aluminum aggregates. Highlights • Hydrated silica abatement from real groundwater by electrocoagulation. • Aluminum electrodes in an up-flow reactor with twelve cell stack. • Hydrated silica reacts with large dose of coagulant to form aluminum silicates. • Fluoride replaces a hydroxyl group from flocs, and arsenate adsorbs on aggregates. • Fluoride and arsenic concentrations after EC fulfill the WHO guidelines. [ABSTRACT FROM AUTHOR]

Arsenic removal consecutive to biological iron oxidation and precipitation is an effective process for treating As-rich acid mine drainage (AMD). We studied the effect of hydraulic retention time (HRT)—from 74 to 456 min—in a bench-scale bioreactor exploiting such process. The treatment efficiency was monitored during 19 days, and the final mineralogy and bacterial communities of the biogenic precipitates were characterized by X-ray absorption spectroscopy and high-throughput 16S rRNA gene sequencing. The percentage of Fe(II) oxidation (10-47%) and As removal (19-37%) increased with increasing HRT. Arsenic was trapped in the biogenic precipitates as As(III)-bearing schwertmannite and amorphous ferric arsenate, with a decrease of As/Fe ratio with increasing HRT. The bacterial community in the biogenic precipitate was dominated by Fe-oxidizing bacteria whatever the HRT. The proportion of Gallionella and Ferrovum genera shifted from respectively 65 and 12% at low HRT to 23 and 51% at high HRT, in relation with physicochemical changes in the treated water. aioA genes and Thiomonas genus were detected at all HRT although As(III) oxidation was not evidenced. To our knowledge, this is the first evidence of the role of HRT as a driver of bacterial community structure in bioreactors exploiting microbial Fe(II) oxidation for AMD treatment. [ABSTRACT FROM AUTHOR]

In this study, two types of novel hybrid nanomaterials, i.e., graphene oxide‐manganese ferrite (GMF) and titania nanotube‐manganese ferrite (TMF), were synthesized and used as adsorbent for removing arsenate (As(V)) ions from water via adsorption mechanisms. The synthesized nanomaterials were characterized by different techniques prior to use in the adsorption process. Batch adsorption studies revealed that the maximum adsorption capacities of GMF and TMF against As(V) are 102.0 and 80.8 mg g−1, respectively, when tested using feed water solution containing 400 ppm As(V). Two types of innovative hybrid nanomaterials, namely, graphene oxide‐manganese ferrite and titania nanotube‐manganese ferrite, with enhanced properties were synthesized and applied as adsorbent to remove As(V) from water. A high level of reusability after undergoing a simple desorption process coupled with the promising adsorption capacity make the hybrid nanomaterials highly potential. [ABSTRACT FROM AUTHOR]

Arsenic is a toxic element that is often found in drinking water in developing countries in Asia, while arsenic poisoning is a serious worldwide human health concern. The objective of this work is to remove arsenic (V) (As(V)) from water by using an adsorbent material prepared from mine waste, called MIRESORBTM, which contains Fe, Al. The performance of the MIRESORBTM adsorbent was compared with granular ferric hydroxide (GFH), which is a commercial adsorbent. Adsorbents were characterized by using scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), and N2 sorption with Brunauer–Emmett–Teller (BET) analysis. The kinetics, isotherms, and pH-dependency of arsenic adsorption were interrogated to gain insights into arsenic adsorption processes. The maximum adsorption capacity of MIRESORBTM was 50.38 mg/g, which was higher than that of GFH (29.07 mg/g). Moreover, a continuous column test that used environmental samples of acid mine drainage was conducted to evaluate the MIRESORBTM material for practical applications. The column could be operated for more than 5840 bed volumes without a breakthrough. Successful operation of a pilot plant using MIRESORBTM adsorbent was also reported. Thus, these studies demonstrate MIRESORBTM as a highly efficient and economical adsorbent derived from recycled mine sludge waste.

In an effort to explore the potential for the removal of arsenic from water, mesoporous iron oxide (MI) was prepared using a sonochemical method. The surface area and average pore size of the MI sample were determined using a Brunauer Emmett Teller (BET) analysis to be 269 m2/g and 6.9 nm, respectively. Kinetic experiments revealed that more than 90% of the As(III) and As(V) were adsorbed onto the MI sample within 5 min at 0.1 g/L of MI dosage. The Langmuir equation model suited As(V), whereas As(III) related better to the Freundlich equation model due to different adsorption mechanisms. The predominant mechanism of As(V) adsorption onto MI is thought to be the electrostatic force between As(V) and MI, whereas As(III) in the solution bound to the adsorbed As(III) on the MI in a way consistent with van der Waals attraction. The removal rate of As(III) and As(V) has the highest adsorption efficiency in the pH 5–9 range. The adsorption of As(III) and As(V) was little affected by ionic strength, however the presence of H4SiO40 and PO43− significantly reduced the arsenic adsorption capacity. Furthermore, the adsorption and regeneration efficiency of MI was maintained at around 100% for given adsorption–regeneration cycles.

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. [Display omitted] • Adsorption-FDFO system for extremely acidic As-containing heavy metal treatment. • Effective solidification of As(III,V) with various ratios by CoFe 2 O 4 @MIL-100 @ ε -MnO 2. • Extremely low detection of metals in the final nutrient solution. • Neglected metal fouling on membrane due to pre-settlement of metal-As precipitates. • Nutrient-rich solution suitable for hydroponics systems with excellent reusability. [ABSTRACT FROM AUTHOR]

Steel rolling sludge (SRS) is the by-product of metallurgical industry with abundant iron content, which needs to be utilized for producing high value-added products. Herein, cost-effective and highly adsorbent α-Fe 2 O 3 nanoparticles were prepared from SRS via a novel solvent-free method and applied to treat As(III/V)-containing wastewater. The structure of the prepared nanoparticles was observed to be spherical with a small crystal size (12.58 nm) and high specific surface area (145.03 m2/g). The nucleation mechanism of α-Fe 2 O 3 nanoparticles and the effect of crystal water were investigated. More importantly, compared with the traditional methods of preparation cost and yield, this study was found to have excellent economic benefits. The adsorption results indicated that the adsorbent could effectively remove arsenic over a wide pH range, and the optimal performance of nano adsorbent for As(III) and As(V) removal was observed at pH 4.0–9.0 and 2.0–4.0, respectively. The adsorption process was consistent with pseudo-second-order kinetic and Langmuir isothermal model. The maximum adsorption capacity (q m) of adsorbent for As(III) and As(V) was 75.67 mg/g and 56.07 mg/g, respectively. Furthermore, α-Fe 2 O 3 nanoparticles exhibited great stability, and q m remained at 64.43 mg/g and 42.39 mg/g after five cycles. Particularly, the As(III) was removed by forming inner-sphere complexes with the adsorbent, and it partially oxidized to As(V) during this process. In contrast, the As(V) was removed by electrostatic adsorption and reaction with –OH on the adsorbent surface. Overall, resource utilization of SRS and the treatment of As(III)/(V)-containing wastewater in this study are in line with the current developments in the environmental and waste-to-value research. [Display omitted] • α-Fe 2 O 3 nanoparticles were prepared from SRS via solvent-free method. • α-Fe 2 O 3 nanoparticles exhibited great As(III/V) adsorption capacity. • As(III) were removed via formation of monodentate inner-sphere complexes. • As(V) were adsorbed via electrostatic interaction and OH− group reaction. • Economic analysis proved this novel method as economically viable. [ABSTRACT FROM AUTHOR]

In the past few years, human activities, such as mining and metallurgical industries, have made the arsenic concentration in natural waters elevate. To provide clean and safe water to people worldwide, tremendous endeavors have been made to accomplish low-cost and effective treatment of arsenic-containing water. Among the methods employed, electro-coagulation has been the one that stands out attributable to its high efficiency and low cost. However, its high energy consumption has become an obstacle to further applications, particularly in the regions where electricity is limited. Here, an innovative self-powered electro-coagulation system (SPECS) driven by flexible electromagnetic flag wind generators (FEFWGs) is developed to realize the power-free removal of dissolved arsenic in water. The FEFWGs exhibit an excellent output performance under a moderate wind speed (6.3 m s−1), with a peak open-circuit voltage of 3.7 V and a peak short-circuit current of 13.6 mA. Using the SPECS to purify polluted water, a large volume of wastewater containing 5 ppm of arsenic can be purified with our SPECS in 20 min, which is more efficient than that of existing reports. [Display omitted] • A fully flexible electromagnetic wind generator that can yield mA level of current. • The very first example of self-powered electro-coagulation system for arsenic removal. • Best-in-class current density and shortest removal time of pollutants in water. • Excellent adaption for the treatment of wastewater with a complicated composition. [ABSTRACT FROM AUTHOR]

• F − and As removal from natural groundwater by capacitive deionization (CDI). • Contaminated real groundwater with F − (1.6 mg L−1) and As (19.6 μg L−1). • CDI cell equipped with the versatile GF as the anode and cathode in a flow plant. • Treated water fulfills the WHO guidelines (< 1.5 mg L−1 F − , and < 10 μg L−1 As). • GF reuse (cycling) intensifies CDI as an affordable technology to supply safe water. This paper reports for the first time the removal of fluoride and arsenic from natural groundwater by capacitive deionization (CDI). The CDI trials were performed in a laboratory-scale flow cell, in recirculation mode, equipped with two graphite felts (GFs) as the anode and cathode. The characterization of the cell in terms of anodic applied potential (E app , 0-1.3 V vs. SHE) and flow rate (Q , 0.1-0.4 L min−1) was systematically examined in a synthetic solution containing F − , finding E app = 1.2 V vs. SHE and Q = 0.2 L min−1 as the best conditions. Afterward, F − and arsenic removal from real groundwater (1.6 mg L−1 F − , 19.6 μg L−1 As, 0.4 mg L−1 PO 4 3‒, pH 6.6, and 430 μS cm−1 conductivity) was performed by using E app = 1.2 V vs. SHE and Q = 0.2 L min−1. After three rounds of CDI, the solution reached ending values of 1.2 mg L−1 F − , 7.4 μg L−1 As, 0.2 mg L−1 PO 4 3‒, with energy consumption (EC) of 0.023 kWh m−3. The treated water fulfills the WHO guidelines (< 1.5 mg L−1 F − , and < 10 μg L−1 As). CDI using GF electrodes is an affordable technology to supply safe drinking water. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the adsorption performance of three types of adsorbents for removal of As(V) from water: Bayoxide® E33 (granular iron(III) oxide), Titansorb® (granular titanium oxide) and a suspension of precipitated iron(III) hydroxide. Results of As(V) adsorption stoichiometry of two commercial adsorbents and precipitated iron(III) hydroxide in tap and demineralized water were fitted to Freundlich and Langmuir adsorption isotherm equations, from which adsorption constants and adsorption capacity were calculated. The separation factor RL for the three adsorbents ranged from 0.04 to 0.61, indicating effective adsorption. Precipitated iron(III) hydroxide had the greatest, while Titansorb had the lowest capacity to adsorb As(V). Comparison of adsorption from tap or demineralized water showed that Bayoxide and precipitated iron(III) hydroxide had higher adsorption capacity in demineralized water, whereas Titansorb showed a slightly higher capacity in tap water. These results provide mechanistic insights into how commonly used adsorbents remove As(V) from water.

This study investigated the biological removal of heavy metals from mine tailings in Kazakhstan using acidophilic microorganism strains Acidithiobacillus ferrivorans 535 and Acidithiobacillus ferrooxidans 377. The experiments were conducted in shake flasks at pH 1.6, various temperatures (28 °C, 18 °C, and 8 °C), and 10% solid concentration (w/v). The results of inductively coupled plasma optical emission spectroscopy and X-ray diffraction analyses showed that arsenic was particularly efficiently removed at 28 °C. At this temperature, A. ferrooxidans 377 was more efficient at removal than the other strain. Meanwhile, A. ferrivorans 535 was more efficient than A. ferrooxidans 377 at 8 °C. One of the more significant findings to emerge from this study is that arsenic can be removed at a low temperature and high solid concentration. The results of this study support the idea that microorganisms can be used for removing arsenic via a combination of biooxidation and chemical methods.

Threats due to insufficient, inadequate and costlier methods of treating contaminants such as arsenic have emphasized the significance of optimizing and managing the processes adopted. This study was aimed at the complete elimination of arsenic from an aqueous medium with minimum energy consumption using the electrocoagulation process. Arsenic removal around 95% was rapidly attained for optimized conditions having a pH of 7, 0.46 A current intensity, 10 mg/L initial concentration and only 2 min of applied time duration using the energy of 3.1 watt-hour per gram of arsenic removed. Low values of applied current for longer durations resulted in the complete removal of arsenic with low energy consumption. Various hydroxide complexes including ferrous hydroxide and ferric hydroxide assisted in the removal of arsenic by adsorption along with co-precipitation. Surface models obtained were checked and found with a reasonably good fit having high values of coefficient of determination of 0.933 and 0.980 for removal efficiency and energy consumption, respectively. Adsorption was found to follow pseudo-first-order kinetics. Multivariate optimization proved it as a low-cost effective technology having an operational cost of 0.0974 Indian rupees (equivalent to USD 0.0013) per gram removal of arsenic. Overall, the process was well optimized using CCD based on response surface methodology.

Natural zeolites are used as adsorbents in purification processes due to their cation-exchange ability and molecular sieve properties. Surface modified natural zeolites (SMNZs), produced by attaching cationic organic surfactants to the external surface, can simultaneously act as ionic exchangers and organic molecule adsorbents. In this paper, SMNZs were produced and investigated as adsorbents for As(V) removal from wastewater: two natural zeolites, clinoptilolite and phillipsite, were modified using HDTMA-Br and HDTMA-Cl as surfactants. The obtained samples were then characterized under static and dynamic conditions. Results showed that As(V) removal follows a pseudo-second order kinetic, with fast adsorption rates: every sample reached 100 % removal in 2 h, while equilibrium data showed a Langmuir-like behavior, with a greater anion uptake by the HDTMA-Br modified SMNZs due to the formation of a compact and complete micellar structure. Finally, fixed-bed tests were performed to characterize the samples under dynamic conditions assessing the effect of severe operating parameters on the dynamic exchange capacity, selectivity and efficiency of the process. The obtained results demonstrate a good ability of the tested materials to adsorb As(V) from wastewater, confirming the effectiveness of the proposed surface modification technique in expanding the possibility of using natural zeolites in these processes.

Even though manganese oxides are attractive materials for batteries, super-capacitors and electro-catalysts for oxygen reduction reactions, in most practical applications MnO2 needs to be hybridized with conductive carbon nano-structures to overcome its inherent poor electrical conductivity. In this manuscript we report microwave-assisted synthesis of MnO2 embedded carbon nanotubes (MnO2@CNT) from Mn-H3BTC (benzene-1,3,5-carboxylic acid) metal organic frameworks (MOF) precursors. Using graphene oxide as microwave susceptible surface, MnO2 nano-particles embedded in three dimensional reduced graphene oxide (rGO) -CNT frameworks (MnO2@CNT-rGO) were synthesized which when applied as electro-catalysts in oxygen reduction reaction (ORR) demonstrated comparable half-wave potential to commercial Pt/C, better stability, and excellent immunity to methanol crossover effect in alkaline media. When carbon fiber (CF) was used as substrate, three-dimensional MnO2@CNT-CF were obtained whose utility as effective adsorbents for arsenic removal from contaminated waters is demonstrated.

Novel citrate/FeCO3 nanocomposites (CF-NCs) were synthesized for effective arsenic (III and V) sorption with constant addition of Fe2+ into HCO3− solution in the presence of citrate. This paper is the first report on the formation of CF-NCs, and in this study we investigate the mechanisms of arsenic uptake by the sorbent under anoxic conditions through various solid- and liquid-phase spectroscopic methods, including X-ray absorption spectroscopy. In CF-NCs, citrate was found to be incorporated into the structure of siderite (up to 17.94%) through (Fe2+citrate)− complexes. The crystal morphology of rhombohedral siderite was changed into hierarchically nanostructured spherical aggregates composed of several sheet-like crystals, which improved the surface reactivity in the presence of sufficient citrate. Compared to pure siderite (15.2%), enhanced removal of As(III) in the range of 19.3% to 88.2% was observed, depending on the amount of incorporated citrate. The maximum sorption capacities of CF-NCs for As(III) and As(V) were 188.97 and 290.22 mg/g, respectively, which are much higher than those of previously reported siderite-based adsorbents. It was found that arsenic (III and V) sorption on CF-NCs occurred via bidentate corner-sharing surface complexation, predominantly without changes in the arsenic oxidation states. These results suggest that arsenic (III and V) can be attenuated by siderite in anoxic environments, and this attenuation can be even more effective when siderite is modified by incorporation of organic compounds such as citrate.

One of the promising applications of nanomaterials is to use them as catalysts and sorbents to remove toxic pollutants such as nitroaromatic compounds and heavy metal ions for environmental protection. This work reports the synthesis of Cu/CuO-deposited composite track-etched membranes through low-temperature annealing and their application in catalysis and sorption. The synthesized Cu/CuO/poly(ethylene terephthalate) (PET) composites presented efficient catalytic activity with high conversion yield in the reduction of nitro aryl compounds to their corresponding amino derivatives. It has been found that increasing the time of annealing raises the ratio of the copper(II) oxide (CuO) tenorite phase in the structure, which leads to a significant increase in the catalytic activity of the composites. The samples presented maximum catalytic activity after 5 h of annealing, where the ratio of CuO phase and the degree of crystallinity were 64.3% and 62.7%, respectively. The catalytic activity of pristine and annealed composites was tested in the reduction of 4-nitroaniline and was shown to remain practically unchanged for five consecutive test cycles. Composites annealed at 140 °C were also tested for their capacity to absorb arsenic(III) ions in cross-flow mode. It was observed that the sorption capacity of composite membranes increased by 48.7% compared to the pristine sample and reached its maximum after 10 h of annealing, then gradually decreased by 24% with further annealing.

Arsenic (As) removal is of major significance because inorganic arsenic is highly toxic to all life forms, is a confirmed carcinogen, and is of significant environmental concern. As contamination in drinking water alone threatens more than 150 million people all over the world. Therefore, several conventional methods such as oxidation, coagulation, adsorption, etc., have been implemented for As removal, but due to their cost-maintenance limitations; there is a drive for advanced, low cost nanofiltration membrane-based technology. Thus, in order to address the increasing demand of fresh and drinking water, this review focuses on advanced nanofiltration (NF) strategy for As removal to safeguard water security. The review concentrates on different types of NF membranes, membrane fabrication processes, and their mechanism and efficiency of performance for removing As from contaminated water. The article provides an overview of the current status of polymer-, polymer composite-, and polymer nanocomposite-based NF membranes, to assess the status of nanomaterial-facilitated NF membranes and to incite progress in this area. Finally, future perspectives and future trends are highlighted.

Arsenic (As) is considered one of the most serious inorganic pollutants, and the wastewater produced in some smelters contains a high concentration of arsenic. In this paper, we purified the high-concentration arsenic solution with red mud and Fe3+ synergistically. In this system, arsenite anions reacted with Fe(III) ions to form ferric arsenite, which attached on the surface of red mud particles. The generated red mud/Fe1−x(As)x(OH)3 showed a better sedimentation performance than the pure ferric arsenite, which is beneficial to the separation of arsenic from the solution. The red mud not only served as the carrier, but also as the alkaline agent and adsorbent for arsenic treatment. The effects of red mud dosage, dosing order, pH, and molar ratio of Fe/As on arsenic removal were investigated. The efficiency of arsenic removal increased from a pH of 2 to 6 and reached equilibrium at a pH of 7. At the Fe/As molar ratio of 3, the removal efficiency of arsenic ions with an initial concentration of 500 mg/L reached 98%. In addition, the crystal structure, chemical composition, and morphological properties of red mud and arsenic removal residues (red mud/Fe1−x(As)x(OH)3) were characterized by XRD, XPS, X-ray fluorescence (XRF), SEM-EDS, and Raman spectroscopy to study the mechanism of arsenic removal. The results indicated that most of the arsenic was removed from the solution by forming Fe1−x(As)x(OH)3 precipitates on the red mud surface, while the remaining arsenic was adsorbed by the red mud and ferric hydroxide.

Modification of a commercial iron oxide ion exchanger (Arsen Xnp) was carried out to enhance the removal of arsenic(V) ions. The modification consisted of the adsorption of lanthanum(III) ions on the Arsen Xnp surface. After adsorption, the material was dried at 313 K to obtain the modified ion exchanger Arsen Xnp-La(III). The modification process itself was tested for optimal pH, kinetics, and equilibrium adsorption isotherm study. Accurate sorbent characteristics were made using, among others, SEM, FTIR, and nitrogen adsorption/desorption isotherms. Then, various tests were carried out to compare the adsorption properties of the modified and unmodified material. It turned out that the tested material was able to completely remove arsenic from an aqueous solution with an initial concentration of up to 50 mg/dm3. Without modification, it was not possible to reach the WHO recommended 10 μg/dm3 arsenic limit even at an initial concentration of 25 mg/dm3. Moreover, the maximum sorption capacity increased from 22.37 to 61.97 mg/g after modification (3 times greater than before modification). It is worth noting that the process of removing arsenic on Arsen Xnp-La(III) is fast—equilibrium is reached after about 120 min. Under almost neutral conditions, precipitation and adsorption can be the main mechanisms of As(V) removal. After modification, the removal capacity was enhanced by the co-precipitation and adsorption by exchange of the OH– group with arsenic ions. Such La(III) based adsorbent can be successfully applied in wastewater purification and displays superior performance for removing arsenic.

Nitrogen doped carbon nanotubes (NCNT) that were prepared by simple microwave pyrolysis of Niacin (Vitamin B3) as noble metal free electrocatalyst for oxygen reduction reaction (ORR) is reported. Our newly developed technique has the distinct features of sustainable and widely available niacin as a bi-functional source of both carbon and nitrogen, whereas the iron catalyst is cheap and the fourth most common element in the Earth’s crust. The results of the electrochemical tests show that our newly developed iron impregnated NCNT anchored on reduced graphene substrate (Fe@NCNT-rGO) catalyst exhibit: a positive half-wave potential (E1/2) of 0.75 V vs. RHE (reversible hydrogen electrode), four-electron pathway, and better methanol tolerance when compared to commercial 20% Pt/C. When applied as adsorbent for arsenic removal, our newly discovered NCNT-Fe illustrate the efficient and effective removal of arsenic across a wide range of pH values.

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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.

The purpose of this study was a detailed characterization of Shewanella sp. O23S, a strain involved in arsenic transformation in ancient gold mine waters contaminated with arsenic and other heavy metals. Physiological analysis of Shewanella sp. O23S showed that it is a facultative anaerobe, capable of growth using arsenate, thiosulfate, nitrate, iron or manganite as a terminal electron acceptor, and lactate or citrate as an electron donor. The strain can grow under anaerobic conditions and utilize arsenate in the respiratory process in a broad range of temperatures (10–37 °C), pH (4–8), salinity (0%–2%), and the presence of heavy metals (Cd, Co, Cr, Cu, Mn, Mo, Se, V and Zn). Under reductive conditions this strain can simultaneously use arsenate and thiosulfate as electron acceptors and produce yellow arsenic (III) sulfide (As2S3) precipitate. Simulation of As-removal from water containing arsenate (2.5 mM) and thiosulfate (5 mM) showed 82.5% efficiency after 21 days of incubation at room temperature. Based on the obtained results, we have proposed a model of a microbially mediated system for self-cleaning of mine waters contaminated with arsenic, in which Shewanella sp. O23S is the main driving agent.

Background: Contamination of water with arsenic has attracted the researchers’ attention as a global problem in recent years and has been observed in some parts of Iran. The purpose of this study is to assess the efficiency of welding iron waste in removing arsenic from aqueous solutions. Methods: In this study, the effects of different parameters, such as pH (3-9), initial concentration of arsenic (100-3000 μg/l), contact time (5-90min) and adsorbent dose (2.5-20 g/l), were studied. The final concentrations of arsenic were analyzed by atomic absorption. Results: The results indicated that at pH=3 and fixed dose of 1 g, arsenic removal efficiency of iron waste was 89.73%. By increasing the pH to 7, the removal efficiency increased to 96.44%. Also, an increase in the amount of iron waste from 2.5 to 10g/l, the removal rate increased from about 42.37% to 96.70%. For contact times of 5 and 30 minutes, the removal rate was 9% and 96.62%, respectively. Then, with increasing the contact time to 90 minutes, the removal rate increased to 99.24%. Correlation coefficient of Freundlich and Langmuir isotherms for As(III) was 0.7593 and 0.9979, respectively . Conclusion: The results of the study showed that welding iron waste has a high potential as an effective, fast and cheap method for removal of arsenate and arsenite from aqueous solutions.

Water contamination with harmful arsenic compounds represents one of the most serious calamities of the last two centuries. Natural occurrence of the toxic metal has been revealed recently for 21 countries worldwide; the risk of arsenic intoxication is particularly high in Bangladesh and India but recently also Europe is facing similar problem. Liquid membranes (LMs) look like a promising alternative to the existing removal processes, showing numerous advantages in terms of energy consumption, efficiency, selectivity, and operational costs. The development of different LM configurations has been a matter of investigation by several researching groups, especially for the removal of As(III) and As(V) from aqueous solutions. Most of these LM systems are based on the use of phosphine oxides as carriers, when the metal removal is from sulfuric acid media. Particularly promising for water treatment is the hollow fiber supported liquid membrane (HFSLM) configuration, which offers high selectivity, easy transport of the targeted metal ions, large surface area, and non-stop flow process. The choice of organic extractant(s) plays an essential role in the efficiency of the arsenic removal. Emulsion liquid membrane (ELM) systems have not been extensively investigated so far, although encouraging results have started to appear in the literature. For such LM configuration, the most relevant step toward efficiency is the choice of the surfactant type and its concentration.

Background: Arsenic has been considered as one of the most hazardous element for the living organisms and its presence in natural waters, can result in serious health and environmental problems. In this study, Pistacia Atlantica seed extract ability in a batch system to remove arsenate from aqueous solutions was investigated. Materials and methods: This study is an experimental study that was performed in a batch reactor. The effects of major operating variables such as coagulant dose (3–35 mg/L), coagulant aid dose (0.5-5 ml/L), initial arsenic (10-1000µg/L), initial turbidity (10 -100 NTU) and pH (2-12) were investigated. Results: The optimum pH for arsenic and turbidity removal by coagulation using ferric chloride was 6. The highest removal for an initial arsenic concentration of 100 µg/L using 5 mg/L ferric chloride and 0.5 ml/L coagulant aid was found to be 94%, while at the same conditions without use of a coagulant aid, required ferric chloride was 10 mg/L. Conclusion: According to achieved results, it was found that Pistacia atlantica seed extract not only was an inexpensive coagulant aid, but also a quite effective factor in removal of As(v) and turbidity from aqueous environments.

The removal of arsenic from synthetic effluent was studied using the adsorbent particle flotation technique (APF) and dissolved air flotation (DAF). A sample of an iron mineral was used as adsorbent particles of arsenic, ferric chloride as coagulant, cationic poly-acrylamide (NALCO 9808) as flocculants, and sodium oleate as collector. Adsorption studies to determine the pH influence, contact time, and adsorbent particles concentration on the adsorption of arsenic were carried out along with flotation studies to determine the removal efficiency of adsorbents particles. The results achieved indicate that the adsorption kinetic of arsenic is very rapid and that in range of pH’s from 2 to 7 the adsorption percentages remain constant. The equilibrium conditions were achieved in 60 minutes and about 95% of arsenic was adsorbed when used an adsorbent concentration of 2 g/L and pH 6.3. The maximum adsorption capacity of adsorbent particles was 4.96 mg/g. The mean free energy of adsorption (E) was found to be 2.63 kJ/mol, which suggests physisorption. The results of the flotation studies demonstrated that when synthetic effluents with 8.9 mg/L of arsenic were treated under the following experimental conditions; 2 g/L of adsorbent particles, 120 mg/L of Fe(III), 2 mg/L of Nalco 9808, 20 mg/L of sodium oleate, and 40% of recycle ratio in the DAF, it was possible to reach 98% of arsenic removal and 6.3 NTU of residual turbidity in clarified synthetic effluent.

High-level arsenic contamination of drinking water in West Bengal (WB), India is a grave public health concern, with 26 million people remaining affected. Two decades of research has provided detailed information on multiple aspects of exposure assessment and risk characterization. However, policy paralysis due to lack of finances and lack of any administrative coordination between the Central and State Governments has hampered the implementation of long-term solutions. Household- and community-level arsenic removal units have provided some relief to the suffering population. In view of the increased funding through the 12th Five-Year Plan period, it is the responsibility of the authorities to implement piped water supply schemes with single-point treatment facilities as the permanent solution to this three-decade-long crisis. Incorporating research evidence into policy and focusing on behavior change communication would be crucial to that end.

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