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

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

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

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

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

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

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

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

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

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

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

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

The presence of arsenic in water samples of different nature represents a serious problem with severe consequences all around the world, but mainly in India, China, Central Africa, and Latin America. In this regard, the groundwater of the Bahía Blanca region (Bs. As. Province, Argentina in Latin America) clearly represents this problem, containing As levels higher than 200 µg L−1. On many occasions, this resource is almost the unique source of water for human consumption and other uses. The available technology is not suitable and efficient enough to provide solutions in this context. This work proposes the preparation of low-cost, easy handle and efficient material to mitigate the As contamination problem. The aim is to provide useful materials that may be implemented in the real environment; in particular, to remediate groundwater from critical rural zone. Nanocomposites with different nominal ratios of zeolite and magnetite nanoparticles were synthesized. These materials were entirely characterized by FTIR, XRD, TEM, capillary microelectrophoresis, and dynamic light scattering. Adsorption assays were performed in batches using groundwater samples collected in the rural region of Bahía Blanca (southern Chaco-Pampean plain, Argentina). The stability and reuse capability of these adsorbents were evaluated. The possibility of designing a continuous flow system was also explored by comparing the As removal data achieved in this condition with the percentage of removal corresponding to the performed batch assays. The findings collected within this work appear very promising in view of the design of a household system to remove As from groundwater. [ABSTRACT FROM AUTHOR]

Arsenic is among the major drinking water contaminants affecting populations in many countries because it causes serious health problems on long-term exposure. Two low-cost micro-sized iron oxyhydroxide-based adsorbents (which are by-products of the industrial production process of granular adsorbents), namely, micro granular ferric hydroxide (μGFH) and micro tetravalent manganese feroxyhyte (μTMF), were applied in batch adsorption kinetic tests and submerged microfiltration membrane adsorption hybrid system (SMAHS) to remove pentavalent arsenic (As(V)) from modeled drinking water. The adsorbents media were characterized in terms of iron content, BET surface area, pore volume, and particle size. The results of adsorption kinetics show that initial adsorption rate of As(V) by μTMF is faster than μGFH. The SMAHS results revealed that hydraulic residence time of As(V) in the slurry reactor plays a critical role. At longer residence time, the achieved adsorption capacities at As(V) permeate concentration of 10 μg/L (WHO guideline value) are 0.95 and 1.04 μg/mg for μGFH and μTMF, respectively. At shorter residence time of ~ 3 h, μTMF was able to treat 1.4 times more volumes of arsenic-polluted water than μGFH under the optimized experimental conditions due to its fast kinetic behavior. The outcomes of this study confirm that micro-sized iron oyxhydroxides, by-products of conventional adsorbent production processes, can successfully be employed in the proposed hybrid water treatment system to achieve drinking water guideline value for arsenic, without considerable fouling of the porous membrane. [ABSTRACT FROM AUTHOR]

With the aim of developing generalized equation for predicting effect of pH on arsenic removal efficiency through adsorption process, this study presents experimental results on the arsenic removal efficiency using a natural sand (Skye sand which was earlier found to be very effective in removing arsenic from water) under varying pH conditions. Series of batch experiments were conducted with the Skye sand (naturally found in Victoria, Australia) as adsorbent and commercially available standard solution (diluted with deionised water) as arsenic contaminated water. It is observed that highest arsenic removal efficiency was achieved with arsenic contaminated water having a pH of 5.0, below and above which the removal efficiencies decreased following a convex parabolic pattern. Most of the other similar studies also found similar patterns with the varying pH values, achieving maximum Arsenic removal efficiencies for pH values ranging 4.0–8.0. All the experimental measured values of arsenic removals were converted to a standard scaling factor for pH, termed as "SFPH". Study reveals that the SFPH values can be expressed as a second-order polynomial equation. Also, SFPH values for As(III) and As(V) are having insignificant differences. [ABSTRACT FROM AUTHOR]

We have explored the use of two different iron-based porous materials for arsenic uptake from neutral pH aqueous solutions. Both materials are reminiscent of a material known as MIL-100(Fe), a Metal Organic Framework (MOF) built upon the coordination of Fe(III) ions with trimesate organic linkers (benzene tricarboxylic acid). Aside from the proverbial high surface area with extended microporosity/mesoporosity, the presence of Fe(III) centers offers the possibility of specific strong interactions with arsenic, therefore making it appealing for its use in detection and purification technologies. Our approach tackles the characterization of the system from both physical and chemical perspectives. We report equilibrium isotherms and time dependent arsenic uptake for the determination of adsorption capacity and kinetics; and also, by means of synchrotron-based X-ray absorption techniques, we probe possible changes in coordination environments and oxidation states of Fe and As in the porous network occurring upon adsorption at high and low loadings. The results presented bring further insight on the nature and diversity of adsorption sites present and confirm the suitability of the proposed adsorbents for the intended use. [ABSTRACT FROM AUTHOR]

Drinking water sludge (DWS) contains organic carbon and metal ions with the potential to prepare adsorbents. In this research, DWS was separated into two parts by acid leaching, i.e., an acid leaching carbonization sludge (ALCS) and an acid leaching solution. Iron and aluminum were extracted from the acid leaching solution and loaded onto ALCS by sedimentation and liquid-phase reduction to prepare a carbon/Al2O3/nZVI magnetic adsorption material (ALCS-Al-Fe). The optimum arsenic removal conditions, adsorption kinetics, and isotherm were determined, and the characteristics of the adsorbent ALCS-Al-Fe were investigated. The results showed that the composite exerted a favorable arsenic removal effect due to the electrostatic adsorption of nanometer zero-valent iron as well as ion exchange and complexation between the OH− groups on the surface of ALCS-Al-Fe and As(V). The pH change had a slight effect on the adsorption capacity, while the common anions SO42− and SiO32− showed obvious inhibitory effects. Considering that alkalinity is beneficial to arsenic ion desorption, NaOH was used in desorbing to conduct 6 cycles of regeneration experiments, and the final removal rate could still reach 90.5%. Therefore, the concept of green development of preparing magnetic adsorbents by using whole component of DWS is significant to the exploitation of sludge recycling. [ABSTRACT FROM AUTHOR]

Substantial quantities of openly dumped slag contribute to the absence of recovery and utilization of valuable metals as well as potential environmental pollution to water and soil. Owing to the excessively high arsenic content present in iron extracted from copper smelting slag, we propose a new arsenic removal process in this paper. The results indicate that arsenic sulfides in copper smelting slag can be significantly removed at 1100 °C in an N2 atmosphere, leading to a 0.15% residual arsenic content. Furthermore, undecomposed arsenate in the slag can be reduced in an N2–CO atmosphere. During a coal-based direct reduction process, under optimal conditions, the removal efficiency of arsenic is relatively low. Subsequently, under optimal conditions, the arsenic content drops significantly from 0.18 to 0.080%. This new removal process engenders lower arsenic content in iron extracted from slag than the standards of pig iron and direct reduced iron in steelmaking. [ABSTRACT FROM AUTHOR]

Natural groundwater from the towns of Wabana and Freshwater and treated well water from the town of Wabana in Newfoundland and Labrador, Canada were tested separately and together in sand columns to study the removal of arsenic. The most ideal conditions for arsenic removal appeared to include an arsenic concentration of approximately 35 µg/L and lower, an Fe:As mass ratio in the order of 65 and lower, and aeration of the sand media. Active aeration by pumping air though the filter, passive aeration by scraping off top layers of sand and virtual aeration by diluting the strength of the water being treated, were employed and compared. For tests where groundwater from the towns of Wabana and Freshwater was combined, arsenic removal was optimized and other elements, in addition to iron, were also correlated with effluent arsenic. Further, for these same tests there was a gradual increase in effluent pH that could have been due to oxygen depletion or gradually more reducing conditions in the sand column. Where Ni, Mn and Zn were correlated with effluent arsenic it was concluded that the increase in pH increased heavy metal removal and arsenic release. In the test where the treated Wabana water made up a greater proportion of the mix than the Wabana groundwater, lithium was also correlated with arsenic. [ABSTRACT FROM AUTHOR]

Since arsenic is highly toxic and carcinogenic, it now causes serious health problems all over the world. Therefore, there is an urgent need to develop new techniques that are cost-effective and easily applicable to remove arsenic from contaminated waters. Layer double hydroxides have the potential to be a good adsorbent to remove arsenic from contaminated waters due to high surface area and high anion exchange capacity. In this paper, arsenic removal from water by calcined Fe–hydrotalcite (CFeHT) known as layered double hydroxide and prepared synthetically with coprecipitation method was researched. The study brings out that the effect of initial solution pH values was limited for the adsorption. The experimental study indicates that the adsorption of arsenic rapidly occured in comparison with other studies. It was determined that the pseudo-second-order kinetic model was more suitable than the first order. In isotherm studies, it was seen that the experimental data were compatible with Langmuir model. In this study was determined that CFeHT has a high arsenic removal potential. And also the concentration of the arsenic solution (600 µg/L) has been reduced below the allowable value by the World Health Organization (< 10 µg/L). The desorption test indicates that the desorption ratio of As(V) was obtained as 72.7. [ABSTRACT FROM AUTHOR]

Microporous carbon fibers prepared by controlled carbonization of cellulose proved promising carrier of nano- and microparticles of solid active substances. The average pore size of the carbon fibers ranges from 0.5 to 0.6 nm and, therefore, molecules of many low- molecular substances are excluded. Consequently, the nano- and microparticles formed by precipitation of a solution in the presence of fibers are deposited exclusively on their outer surface. In this way, composite materials with favorable macro-structure can be created because large surface of appropriate active substance remains easily accessible for the desired action. Technical problems connected with the direct application of nano- and microparticles are avoided. The practical advantages of the microporous carbon fibers prepared from cellulose comprise feasibility of their preparation, as well as general availability and low price of the raw material. Moreover, compared to particulate carriers with identical diameter, fibrous carriers exhibit reduced resistance against flow of liquids and gases. The pertinence of carriers based on the microporous carbon fibers prepared from delignified cellulose has been tested with the deposition of nano- and microparticles of hydrated ferric hydroxide, Fe(OH)3·(H2O)n. Compared with particulate ferric hydroxide, the resulting heterogeneous composite showed increased efficiency in adsorptive removal of harmful arsenic from water. [ABSTRACT FROM AUTHOR]

This study discusses synthesis and characterization of iron-incorporated activated carbon (MAC) from biomass mixture by FeSO4 impregnation and subsequently pyrolysis, and its application in arsenic adsorption from aqueous solution. The textural, morphological, and structural properties were determined with BET surface area, total pore volume, average pore size, pHpzc, XRD, VSM, and SEM-EDX analysis. The results showed that the MAC has 375.32 m2/g surface area and 0.2391 cm3/g of total pore volume and contains a single iron compound in the magnetite structure. Arsenic removal efficiency was evaluated depending on MAC dosage, pH, contact time, and As(V) concentration. The data was analyzed by Freundlich and Langmuir isotherms. Also, pollution potential of the adsorption residue was examined by TCLP. 10 mg/l of As(V) in the solution could be removed in the presence of 1.5 g/l of MAC at pHs above 2.5 for 60 min. As(V) adsorption fitted better to the Langmuir isotherm, and adsorption capacity was found to be 42.92 mg/g. It has been found that the adsorption residue has no potential pollutants; thus, they are safe for regular landfill waste disposal. The results suggested that FeSO4 impregnation and subsequently pyrolysis were suitable process for synthesis of MAC from biomasses for arsenic adsorption. [ABSTRACT FROM AUTHOR]

Selective removal of trace arsenic is crucial for obtaining safe drinking water. Here, the selective adsorptive performance of arsenate (As(V)) on a hybrid ZMAE (nanoscale zirconium molybdate embedded a macroporous anion exchange resin) was examined. It was found that the As(V) adsorption efficiency of ZMAE was almost retained in the presence of competing ions (NO3− or SO42−) up an [SO42−]/[As] or [NO3−]/[As] ratio of 150/1, whereas that of bare AE (anion exchange resin) was negligible for [SO4]/[As] over 15/1. In addition, the As(V) maximum adsorption capacity of ZMAE was found to be 41.2 mg/g, which is in contrast with the negligible adsorption of bare AE under sulfate-rich condition. The enhanced arsenate selectivity of ZMAE can be attributed to the excellent selectivity of ZM NPs (zirconium molybdate nanoparticles), which contributed up to 45% of the adsorption capacity of ZMAE. The behavior of ZMAE towards arsenate was compared with that towards phosphate showing similar adsorption performances between them, which indicates the similar affinity of ZMAE towards arsenate and phosphate. Finally, ZMAE examined for fixed-bed column adsorption for As(V) removal from synthetic As(V) water was effective for up to 5100 BVs, treating As(V) from 0.1 mg/L to below 0.01 mg/L (meeting the WHO guidelines). [ABSTRACT FROM AUTHOR]

PVA/ZnO nanofibrous composite polymer was synthesized as a novel sorbent via electrospinning method at ambient conditions. Physicochemical characteristics of the samples were analyzed using XRD, SEM, EDS, TGA/DSC, and BET techniques. Efficiency of the composite samples for arsenic removal [i.e., As (III) and As (V) anions] was studied under different conditions using RSM optimization approach. Experimental results of adsorption tests indicated that the synthesized PVA/ZnO polymer with the maximum removal of 97% is a highly efficient sorbent for arsenic comparable with other sorbents studied for arsenic removal. The effect of some cations on arsenic removal was also studied in this research. Results showed that the tested ions do not cause a significant reduction in the removal rate. PVA/ZnO composite polymer, which is highly biocompatible, can be considered as a new adsorbent for removal of arsenic from contaminated water. [ABSTRACT FROM AUTHOR]

A new method to remove arsenic from aqueous chloride solution by using lead oxide was proposed, and the effects of the lead(II)/arsenic(V) molar ratio (nPb(II):nAs(V)), initial pH of solution, initial concentrations of chloride ion (Cl−) and arsenic(V) on arsenic removal were investigated. The results showed that nPb(II):nAs(V), initial pH and initial Cl− concentration had great influence on arsenic removal. The suitable conditions of arsenic removal were initial pH of 1.8–2.4 and initial Cl− concentration of 0.52–2.00 g L−1 for 200 mg L−1 As(V) solution. Initial As(V) concentration had little influence on arsenic removal when the appropriate nAs(V):nCl− was controlled in the solution at nPb(II):nAs(V) of 1.52. Based on these conditions, As(V) removal efficiency reached up to 99.99% and As(V) concentration decreased from 200 mg L−1 to less than 0.01 mg L−1 at initial pH of 1.8 with nPb(II):nAs(V) of 2.12. Various characterizations confirm that the formed precipitate was mimetite (Pb5(AsO4)3Cl) and had better thermal stability within 500 °C. For the prevalent problem of lead dissolution by forming mimetite, Pb residual concentration reduced from 337.6 to 0.07 mg L−1 using sodium sulfide in the solution after arsenic removal. Therefore, lead oxide could be used as an effective reagent of arsenic removal to remove As(V) from aqueous chloride solution. [ABSTRACT FROM AUTHOR]

Developing affordable and efficient materials for the removal of arsenic from drinking water is crucial for human and environmental safety. In the present study, the adsorptive performance of magnetic GO/ZnFe2O4 nanocomposite and ZnFe2O4 nanospinel for arsenic removal from aqueous water was analyzed. The adsorbents were characterized using Fourier-transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, selected area electron diffraction and vibrating sample magnetometer. The conditions were optimized by response surface methodology (RSM) by considering the main factors as adsorption time, arsenic concentration, dose of adsorbent and pH. The optimum condition for the removal of arsenic was observed at pH 9.76, 30 min of contact time, 13.4 mg L−1 of initial arsenic concentration and 0.048 g of adsorbent dosage. The predicted arsenic removal percent under optimized conditions was noted as 98%; on the other hand, the experimental values at optimized conditions were observed as 96%. The Pareto analysis predicted that pH of the polluted water is the major factor in adsorptive arsenic removal and the relative importance of the process factors was found in the following order: pH > arsenic concentration > contact time > adsorbent dosage. Thus, introduced compositions form a promising material for the decontamination of polluted water or using in environmental remediation programs. [ABSTRACT FROM AUTHOR]

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In the present study, a process for selective removal of arsenic from Cu–As-containing filter cakes using Na2CO3 leach was examined. When decreasing the weight percentage of arsenic in Cu–As-containing filter cakes, environmental problems can be eliminated while valuable metals will be recycled. The effect of α(Na2CO3) (where α represents excess coefficient), temperature, L/S ratio and leaching time were investigated. the optimal leaching conditions were achieved as follows: α(Na2CO3) = 2.7, L/S ratio 6 : 1 (mL/g), temperature 75°C, leaching time 3 h, where the leaching efficiency were 96.47% for As, 0.41% for Cu with final As and Cu concentrations of 11.72 and 0.02 g/L respectively. Further analysis showed that the Cu content in the leach residue increased to 51.42% with CuS as the major Cu phase. Notably, only 0.92% of As remained in the leach residue. The leaching solution was treated by sodium persulfate oxidation and arsenic precipitation which eliminated As 99%, leaving 0.5 mg/L As in the solution. Therefore, the proposed process is a viable method for the effective separation of Cu and As in Cu–As-containing filter cakes. Broadly, the results of this paper provide a reference for the treatment of arsenic sulfide from nonferrous metallurgy cyclic leaching process. [ABSTRACT FROM AUTHOR]

A new alkaline pressure oxidative leaching process (with NaNO3 as the oxidant and NaOH as the alkaline reagent) is proposed herein to remove arsenic, antimony, and lead from bismuth-rich and arsenic-rich lead anode slime for bismuth, gold, and silver enrichment. The effects of the temperature, liquid-to-solid ratio, leaching time, and reagent concentration on the leaching ratios of arsenic, antimony, and lead were investigated to identify the optimum leaching conditions. The experimental results under optimized conditions indicate that the average leaching ratios of arsenic, antimony and lead are 95.36%, 79.98%, 63.08%, respectively. X-ray diffraction analysis indicated that the leaching residue is composed of Bi, Bi2O3, Pb2Sb2O7, and trace amounts of NaSb(OH)6. Arsenic, antimony, and lead are thus separated from lead anode slime as Na3AsO4· 10H2O and Pb2Sb2O7. Scanning electron microscopy and energy-dispersive spectrometry imaging revealed that the samples undergo appreciable changes in their surface morphology during leaching and that the majority of arsenic, lead, and antimony is removed. X-ray photoelectron spectroscopy was used to demonstrate the variation in the valence states of the arsenic, lead, and antimony. The Pb(IV) and Sb(V) content was found to increase substantially with the addition of NaNO3. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles (IONPs) were synthesized via an affordable and environmentally friendly route using waste banana peel extract. The polyphenol-rich extract acted as a stabilizing and reducing agent resulting in formation of α-Fe2O3 with a particle size of around 60 nm. The composition, phase, morphology and size of the nanoparticles were analyzed by X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and a Zetasizer. The efficiency of the IONPs was assessed in terms of arsenic(V) remediation from contaminated water within the range of 0.1–2.0 mg/L. Batch study showed that IONPs had a high As(V) adsorption capacity of about 2.715 mg/g at 40 °C. A statistical approach, viz. an artificial neural network, was adapted for modeling and optimization of the process parameters for achieving maximum As(V) removal efficiency. A set of 54 experimental sets were conducted and the predicted model generated showed an R2 value of 0.9971 and the corresponding mean squared error value was 0.0000601. Surface binding of the As(V) phenomenon on the green synthesized IONPs was explained on the basis of FTIR spectroscopy, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy of the control and the As(V)-loaded IONPs.The spent adsorbent was successfully immobilized in phosphate glass matrix with an objective to provide a complete and sustainable solution for arsenic contamination. [ABSTRACT FROM AUTHOR]

The contamination of arsenic from natural processes and anthropogenic activities represents a global concern; therefore, the study of arsenic transformation is an important research topic. This work proposes a simple phenomenological kinetic model that describes the removal of arsenic by means of the crystallisation of scorodite using an extremophile archaeon (Acidianus brierleyi), considering the chemical reaction network to propose the corresponding mass balances. To determine the satisfactory predictive capacitive of the kinetic model structure and the usefulness of the parametric identification, two additional experimental campaigns of the formation of bioscorodite performed in shaking flasks with initial As(III) concentrations of (mM): 4.3–13 and Fe(II) concentrations of (mM): 6–18 were tested. Furthermore, a parametric sensitivity analysis was performed to determine points of special importance related to analytical techniques, to improve the precision of the results that can be used for further in silico studies. Statistical results suggest that the proposed model showed an acceptable fit for all tested conditions. [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]

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]

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]

Fe-based metal-organic framework MIL-88A microrods were synthesized by hydrothermal method, which were used to adsorb As(V) in water for the first time. The experimental results indicated that MIL-88A has a very fast adsorption rate towards arsenic in water. The kinetic and isothermal data for arsenic removal were better fitted to the pseudo-second-order kinetic model and Langmuir model, respectively, implying a chemical and monolayer adsorption for As(V) on MIL-88A microrods. Two rate-controlling processes during adsorption were revealed by the intraparticle diffusion model. The maximum adsorption capacity of MIL-88A reached 145 mg g−1, higher than those of Fe-based MIL adsorbents reported previously, which probably originates from its unique microstructure with abundant OH− groups and an unusual large swelling towards water. These show that Fe-based MIL-88A is a good candidate for arsenic removal. [ABSTRACT FROM AUTHOR]

Arsenic is among the most dangerous contaminants which can limit groundwater use for drinking water consumption. Among the most diffused As-removal technologies around the world, adsorptive media systems are usually favored for relatively low cost and simplicity of operation. This study examines the performance of a laboratory-scale iron oxide-coated sand (IOCS) column filter, to remove arsenic (arsenate (As[V]) and arsenite (As[III])) from groundwater. This technology could be adopted in small communities, as it showed consistent removal rates of 99% with an easy-to-operate process. Some considerations about the possible introduction of such technology in developing countries are provided, highlighting the general impacts to human health related to high arsenic concentrations in groundwater. This, among other adsorption processes, could be recommended as a sustainable mean of ensuring good drinking water quality in developing regions, reducing human health impacts. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes prepared by varying compositions of Cellulose acetate, acetone and formamide for the synthesis of ultrafiltration/nanofiltration membranes with and without nanoparticles for the removal of arsenic from synthetic solution. Zinc oxide nanoparticles were synthesized by an in situ ultrasonic technique and characterization done using XRD and SEM. In the current study, batch experiments were conducted to characterize the maximum removal efficiency of arsenic by cellulose acetate-ZnO mixed matrix membrane. It was found that 58.77% of arsenic removal was obtained for the feed concentration of 1000 mg/L and pH range 6.8 ± 0.6. The nanoparticle-embedded membranes show higher removal efficiency, high flux and permeation rate than cellulose acetate membranes without embedded nanoparticles. [ABSTRACT FROM AUTHOR]

A novel graphene-based nanocomposite membrane was synthesized by interfacial polymerization (IP) through chemical bonding of the graphene oxide (GO) layer to polyethersulfone surface. Detailed characterization of the composite membrane through AFM, SEM, ATR-FTIR, XRD analysis, and Raman spectroscopy indicates strong potential of the membrane in highly selective removal of the toxic contaminants like arsenic and fluoride while permeating the essential minerals like calcium and magnesium. This makes the membrane suitable for production of safe drinking water from contaminated water. The membrane applied in a flat-sheet cross-flow module succeeded in removal of more than 98% arsenic and around 80% fluoride from contaminated water while selectively retaining the useful calcium and magnesium minerals in drinking water. A sustained pure water flux of around 150 LMH (liter per square meter per hour) during operation over long hours (> 150 h) with only 3-5% drop in flux indicates antifouling character of the membrane module. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the 2D modeling of a laboratory scale ion exchange/electrodialysis (IXED) flow cell for removal of As(V) ions from water. The cell consists of a central compartment (DS) delimited by two anion membranes and packed with anion exchange resin, one compartment on each side of the central compartment (CC and AC compartment) lined with a cation exchange membrane and a rinse compartment at each end of the cell. The developed model comprises: the anion exchange in the resin bed in a process controlled by the mass transport rate; the ion transport in the solutions of resin-free compartments, in the membranes and resin, based on Nernst-Planck equation; and enhanced water dissociation at the anion membrane/solution interface. The obtained results show the potential profiles, Donnan potential, concentration polarization and the contribution of each mechanism (diffusion and migration) to ion transport rate as well as the effect of the potential difference on water dissociation rate along the membrane surface. The results show that, at typically low arsenic concentrations in arsenic removal processes, water dissociation plays a key role in ion exchange resin regeneration, process whose intensity grows as the cell potential rises. Moreover, the non-homogeneous distribution of current produces uneven resin regeneration that depends on design and operating parameters. The ion exchange/electrodialysis model is applied to the IXED cell operating in recirculation mode by using individual tanks connected to each cell compartment to describe the experimental batch behavior where arsenic concentration varied from (initial) 13.3 ppm to (final concentration) less than 0.01, 8.9 and 21.3 ppm in DS, CC and AC compartments, respectively, at an operating current density of 8.4 A m−2 removing 99.9% of arsenic in DS compartment with 18.9% of total current efficiency. The model results of As(V) concentration decline in the solution flowing over the ion exchange bed agree very closely with experimental data; however, the As(V) concentration results in the resin-free compartments show deviations from experimental data during the process with 6 and 16% deviations at the end of the batch. These deviations are attributed to model assumptions, in particular to the effect of diverse, non-considered, As(V) ion species.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: This work involved the synthesis of bimetallic complex of [Cu(bpy)3][Cu(dipic)2]·2H2O (1) where dipic is pyridine-2,6-dicarboxylic acid and bpy is 2,2′-bipyridine, through the reaction of [Cu(bpy)5]2+ with [Cu(dipic)2]2−. The structure of complex (1) was characterized by, Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, atomic absorption spectroscopy (AAS), elemental analysis and conductivity measurement. Also, thermal behavior of the complex was studied by thermo-gravimetric analysis (TGA and DTA) and the morphology of the complex was studied by scanning electron microscopy technique (SEM). The complex (1) was used as a precursor for the preparation of ferromagnetic nanoparticles of CuO by thermal decomposition at 600 °C. CuO nanoparticles were characterized by FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Magnetic properties of complex (1) and CuO nanoparticles were studied at room temperature by vibrating sample magnetometer (VSM). The results of VSM indicate paramagnetic and ferromagnetic feature of and CuO nanoparticles, respectively. CuO nanoparticles with specific surface area of 69 m2/g and particle size of 20 nm were used as adsorbents to remove arsenic from contaminated water. The highest amount of arsenic adsorption on the surface of CuO nanoparticles occurs at pH 8 to 9 and contact time of 40 min. Based on this study, copper oxide nanoparticles can be effectively used to remove arsenic from water.Graphical Abstract: Magnetization curves at 298 K (a) complex of [Cu(bpy)3][Cu(dipic)2]·2H2O: (b) nanoparticles of CuO [ABSTRACT FROM AUTHOR]

Recently, nano zero-valent iron (nZVI) has emerged as an effective adsorbent for the removal of arsenic from aqueous solutions. However, its use in various applications has suffered from reactivity loss resulting in a decreased efficiency. Thus, the aim of this study was to develop an effective arsenic adsorbent as a core/shell structural nZVI/manganese oxide (or nZVI/Mn oxide) to minimize the reactivity loss of the nZVI. As the major result, the arsenic adsorption capacities of the nZVI/Mn oxide for As(V) and As(III) were approximately two and three times higher than that of the nZVI, respectively. In addition, the As(V) removal efficiency of the nZVI/Mn oxide was maintained through 4 cycles of regeneration whereas that of the nZVI was decreased significantly. The enhanced reactivity and reusability of the nZVI/Mn oxide can be successfully explained by the synergistic interaction of the nZVI core and manganese oxide shell, in which the manganese oxides participate in oxidation reactions with corroded Fe and subsequently retard the release of aqueous iron providing additional surface sites for arsenic adsorption. In summary, this study reports the successful fabrication of a core/shell nZVI/Mn oxide as an effective adsorbent for the removal of arsenic from aqueous solutions. [ABSTRACT FROM AUTHOR]

Arsenic poisoning from contaminated drinking water has evolved as one of the major health hazards in recent times. High concentrations of arsenic in water and soil have been found in many parts of the world. Developing countries like Taiwan, Chile, Argentina, Bangladesh, Nepal and Vietnam are most affected by the contamination of groundwater with arsenic. These countries also cannot afford expensive and large-scale treatments to remove arsenic from drinking waters to acceptable limits (10 ppb, as recommended by WHO and US EPA). The aim of this review is to summarize low-cost, effective conventional technologies currently described in the literature for arsenic removal that can be used in the third world and developing countries, compare them with the emerging technologies and discuss their advantages and disadvantages along with a brief analysis of arsenic chemistry. [ABSTRACT FROM AUTHOR]

FeO-TiO porous ceramic (Fe/TiPC) beads with photo-catalytic performances and high adsorption capacities were prepared by a simple high temperature solid reaction and were applied for arsenic removal from drinking water. The microstructure and morphology of Fe/TiPC were characterized by X-ray diffraction and scanning electron microscopy. More than 90% removal ratio for As (III) and As (V) were respectively achieved by Fe/TiPC within 2 h under UV irradiation. The Langmuir capacity values of Fe/TiPC for As (III) and As (V) were 13.86 and 15.73 mg/g, respectively. In addition, Fe/TiPC could be reused for up to five times without significant reduction in the photocatalytic sensitivity and adsorption capacity aspects. Good catalytic oxidation performances and high adsorption capacities as well as a sample preparation for Fe/TiPC suggest that the composites may have practical prospects for the As (III) and As (V) removal from contaminated water. [ABSTRACT FROM AUTHOR]

Zeolite and limestone were tested for their capability of removing As and Fe from acidic water in batch and column experiments. Synthetic acidic water with 3 mg/L As and 50 or 100 mg/L Fe at pH = 2 was used in the column experiments. In the batch experiments, the As concentration, the mass of media, and the contact time were varied between 0.2 and 5 mg As/L, 0.5 and 50 g, and 0.25 and 42 h, respectively. Maximum As sorption capacity as indicated by the Langmuir model was 0.17 mg/g for zeolite and 1.3 mg/g for limestone, at 18-h contact time and 6.3 g/L medium concentration. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses revealed that As and Fe were retained in zeolite at the end of the batch experiments. The main factors affecting As and Fe removal efficiency and pH raising capacity were the contact time and the media concentration. This was confirmed in the column experiments, since zeolite and limestone columns presented 99% As removal, under a hydraulic loading rate of 21.8 mm/day. However, limestone columns presented a higher Fe removal: 99 versus 73% for zeolite. The results indicate that limestone could be more appropriate than zeolite when As and Fe are present under acidic conditions, given its higher capacity to remove both As and Fe and to raise pH. [ABSTRACT FROM AUTHOR]

The mechanism of arsenic removal during a sintering process was investigated through experiments with a sintering pot and arsenic-bearing iron ore containing arsenopyrite; the corresponding chemical properties of the sinter were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The experimental results revealed that the reaction of arsenic removal is mainly related to the oxygen atmosphere and temperature. During the sintering process, arsenic could be removed in the ignition layer, the sinter layer, and the combustion zone. A portion of FeAsS reacted with excess oxygen to generate FeAsO, and the rest of the FeAsS reacted with oxygen to generate AsO(g) and SO(g). A portion of AsO(g) mixed with AlO or CaO, which resulted in the formation of arsenates such as AlAsO and Ca3(AsO), leading to arsenic residues in sintering products. The FeAsS component in the blending ore was difficult to decompose in the preliminary heating zone, the dry zone, or the bottom layer because of the relatively low temperatures; however, AsO(g) that originated from the high-temperature zone could react with metal oxides, resulting in the formation of arsenate residues. [ABSTRACT FROM AUTHOR]

Arsenic contamination in groundwater is an environmental problem that affects large populations on the global scale. The anion exchange material, Mg-Al layered double hydroxide (Mg-Al LDH) intercalated with NO , is an effective adsorbent for removing As(V) from aqueous solutions. In this study, we prepared Mg-Al LDH with a high anion exchange capacity by the co-precipitation method, and investigated its adsorption isotherm and reaction kinetics with As(V). The adsorption process is well described by the Langmuir model. The maximum adsorption capacities were determined to be 142.86 and 76.92 mg/g for LDHs synthesized with initial Mg/Al molar ratios of 2 and 4, respectively. The reaction kinetics of As(V) with Mg-Al LDH is demonstrated to be pseudo-second order, which indicates that chemisorption (i.e., anion exchange of HAsO with the intercalated NO ) is the rate determining step. The values of the activation energy also indicate that anion exchange is the predominant adsorption mechanism. [ABSTRACT FROM AUTHOR]

Some boron deposits in Turkey contain considerable amounts of arsenic. Arsenic in the boron deposits can create a great risk due to its environmental effects on surface and underground waters. Water sources containing more than a certain concentration of boron and arsenic have negative effects on plants, animals and human beings. Thus, their removals are necessary. In this paper, the removal of arsenic (As) and boron (B) from aqueous solutions by electrocoagulation using aluminum (Al) electrode material was investigated. Specifically, the effects of initial pH, initial arsenic and boron concentrations and operating time on the performance of EC were investigated. Experiments were carried out with different pHs ranging from 2 to 8. Results showed that initial pH was highly effective on the efficiency and high removal efficiencies were observed at initial pH of 4.0 for both arsenic and boron. Initial arsenic and boron concentration affected the removal efficiencies. Arsenic removal efficiency decreased with increasing boron concentration, and boron removal efficiency decreased with increasing arsenic concentration. The results also showed that boron ions prevented to arsenic removal and boron ions competed with arsenic ions. This situation led to the low arsenic and boron removal. [ABSTRACT FROM AUTHOR]

In this work, a functional magnetic nanohybrid consisting of manganese ferrite magnetic nanoparticles (MnFeO) deposited onto graphene oxide (GO) nanosheets was successfully synthesized using a modified co-precipitation method. The as-prepared GO-MnFeO magnetic nanohybrids were characterized using x-ray diffraction, transmission electron microscopy, Fourier transformed infrared spectroscopy, and vibrating sample magnetometer measurements. Adsorption experiments were performed to evaluate the adsorption capacities and efficient removal of arsenic of the nanohybrid and compared with bare MnFeO nanoparticles and GO nanosheets. Our obtained results reveal that the adsorption process of the nanohybrids was well fitted with a pseudo-second-order kinetic equation and a Freundlich isotherm model; the maximum adsorption capacity and removal efficiency of the nanohybrids obtained ~240.385 mg/g and 99.9% with a fast response of equilibrium adsorption time ~20 min. The larger adsorption capacity and shorter equilibrium time of the GO-MnFeO nanohybrids showed better performance than that of bare MnFeO nanoparticles and GO nanosheets. The advantages of reusability, magnetic separation, high removal efficiency, and quick kinetics make these nanohybrids very promising as low-cost adsorbents for fast and effective removal of arsenic from water. [ABSTRACT FROM AUTHOR]

In this study, arsenic as an environmental top-ranked hazardous substance was efficiently removed by a novel adsorbent fabricated by magnetite FeO nanoplates decorated on anodized aluminum oxide (AAO) nanofibers. AAO nanofibers were prepared by anodic polarization method, and then FeO nanoplates were grown on AAO-based substrate by hydrothermal method to fabricate AAO/FeO nanosorbent. Morphology of the fabricated adsorbents was characterized by field emission scanning electron microscopy (FE-SEM), and their crystallinity was studied by X-ray diffraction (XRD). Arsenic (III) removal potential of the proposed adsorbent from contaminated water samples was investigated by the determination of As(III) amounts in the samples by inductively coupled plasma optical emission spectroscopy before and after adsorption process at sub-μg L levels. The results showed that without pre- and post-treatments such as pH adjustment, As(III) was removed effectively from contaminated water samples by using the proposed adsorbent. AAO/FeO sorbent showed excellent ability to remove 0.1 mg L As(III) from water samples up to 96 % uptake. Freundlich adsorption isotherm model was used to interpret the As(III) adsorption on proposed sorbent. The Freundlich isotherm parameters n and k were obtained to be 2.2 and 10.2, respectively, representing the high affinity of proposed adsorbent for arsenic removal. [ABSTRACT FROM AUTHOR]

Composite material Zr-doped TiO, suitable for the removal of arsenic from water, was synthetized with fast and simple microwave-hydrothermal method. Obtained material, Zr-TiO, had uniform size and composition with zirconium ions incorporated into crystal structure of titanium dioxide. Synthetized composite material had large specific surface area and well-developed micropore and mesopore structure that was responsible for fast adsorption of As(III) and As(V) from water. The influence of pH on the adsorption capacity of arsenic was studied. The kinetics and isotherm experiments were also performed. The treatment of natural water sample containing high concentration of arsenic with composite material Zr-TiO was efficient. The concentration of arsenic was reduced to the value recommended by WHO. [ABSTRACT FROM AUTHOR]