Extraction Of Arsenic Research Articles

Ultrasonic-assisted micro solid phase extraction of arsenic on a new ion-imprinted polymer synthesized from chitosan-stabilized pickering emulsion in water, rice and vegetable samples.

Pickering emulsion polymerization has been employed for the Ultrasonic assisted-micro solid phase extraction (UA-µSPE) of ultra trace arsenic species by a new magnetic ion imprinted polymer (MIIP) prior to hydride generation atomic absorption spectrometry. 2-acetyl benzofuran thiosemicarbazone (2-ABT) as a new chelating agent and core- shell hydrophobic magnetic nanoparticles was synthesized and the polymerization was carried out at the presence of arsenic - ligand complex, crosslinker, monomer, initiator, stabilizing agent and water-oil emulsion magnetic carrier. In second step, the nanoparticles and polymers were characterized. The analytical parameters such as pH, amount of polymer and ultrasonic time were selected and optimozed by Plackett-Burman and Box-Behnken designs respectively. Linear dynamic range, detection limit and relative standard deviation were 0.01-85.000 µg·L-l, 0.003 µg·L-l, and 3.21%, respectively. The proposed preconcentration procedure was successfully applied to the determination of arsenic ion in a wide range of food samples with different and complex matrixes.

Empirical kinetic models for the electrochemical extraction of arsenic and heavy metals from clay containing tailings

Three empirical kinetic models for the arsenic, iron and manganese electrochemical extraction from clay containing tailings highly contaminated were analysed: the intraparticle diffusion model, the Elovich model and the two first-order reactions model. Models were chosen regarding their relative simplicity and accuracy of fitting experimental data. Elovich model was the best fitted model for the As extraction data with the lowest average relative error (ARE = 0.320) and the highest coefficient of determination (R2 = 0.986). The intraparticle diffusion model was the most adequate to describe the Fe and Mn extraction (ARE = 0.142, R2 = 0.942 for Fe, and ARE = 0.112, R2 = 0.926 for Mn). The influence of the current intensity, extractant concentration and liquid/solid ratio on the coefficients of the extraction kinetic models was also determined. Arsenic extraction Elovich model coefficients showed a direct linear relationship with the process variables while iron and manganese extraction diffusion model coefficients showed a direct linear relationship with the current intensity and the extractant concentration but an inverse relationship with the liquid/solid ratio. Response surface plots were used for estimating the interactive effect of the four independent variables studied (current intensity, extractant concentration, liquid/solid ratio and time) on the electrochemical extraction.

Market Basket Survey of Arsenic Species in the Top Ten Most Consumed Seafoods in the United States.

The study focused on the determination of arsenic species in the top ten most consumed seafoods in the United States. Fifty-four samples were collected from local supermarkets, and their species identities were confirmed by DNA barcoding. The total arsenic in the samples varied greatly in the range of 8-22200 ng/g (wet mass). Speciation analysis based on extraction of water-soluble and nonpolar arsenic showed that inorganic arsenic (iAs) was found only in clams and crabs, while arsenobetaine (AsB) predominates in most samples. Among the other arsenicals, trimethylarsoniopropionate (TMAP) was found in most matrices with higher concentrations in crabs, and arsenosugars existed in most clams and crabs. Nonpolar arsenic accounted for 1-46% of the total arsenic in the samples. The accuracy of the analytical results was evaluated using standard reference materials and spike recovery tests. The survey showed that the iAs concentrations in America's most consumed seafood products are much lower than the tolerable intake set by the Joint FAO/WHO Expert Committee, even at the highest levels found in this study.

Selective Separation of Arsenic from Lead Smelter Flue Dust by Alkaline Pressure Oxidative Leaching

This study investigated the feasibility of using an alkaline pressure oxidative leaching process to treat lead smelter flue dust containing extremely high levels of arsenic with the aim of achieving the selective separation of arsenic. The effects of different parameters including NaOH concentration, oxygen partial pressure, liquid-to-solid ratio, temperature, and time for the extraction of arsenic were investigated based on thermodynamic calculation. The results indicated that the leaching efficiency of arsenic reached 95.6% under the optimized leaching conditions: 80 g/L of NaOH concentration, 1.0 MPa of oxygen partial pressure, 8 mL/g of liquid-to-solid ratio, 120 °C of temperature, 2.0 h of time. Meanwhile, the leaching efficiencies of antimony, cadmium, indium and lead were less than 4.0%, basically achieving the selective separation of arsenic from lead smelter flue dust. More than 99.0% of arsenic was converted into calcium arsenate product and thus separated from the leach solution by a causticization process with CaO after other metal impurities were removed from the solution with the addition of Na2S. The optimized causticization conditions were established as: 4.0 of the mole ratio of calcium to arsenic, temperature of 80 °C, reaction time of 2.0 h. The resulting product of calcium arsenate may be used for producing metallic arsenic.

Removal and recovery of arsenic from concentrated sulfuric acid by solvent extraction

Arsenic-contaminated sulfuric acid solutions are produced in large quantities as by-product during pyrometallurgical processing of sulfide minerals. Options for re-using such acid solutions are increased if the arsenic is removed and recovered as a product. The performances of tributyl phosphate and a mixture of 6 wt-% 1,2-octanediol in 2-ethylhexanol were studied in liquid-liquid extraction of arsenic from an industrial solution containing 10.4 M H2SO4. It was found that, due to the complex phase equilibria, a process design based on conventional batch equilibrium data did not describe the countercurrent processes accurately. A countercurrent flowsheet utilizing undiluted tributyl phosphate was investigated by pseudo-countercurrent extractions. 83.7% extraction of arsenic and 31.4% coextraction of H2SO4 was obtained in three-stage countercurrent extraction operated at a solvent-to-feed ratio of 0.79. Two-stage countercurrent scrubbing with pure water at O/A = 4.03 back-extracted 83.6% of H2SO4 and 24.9% of arsenic. 100% and 89.7% back-extraction was achieved in four-stage stripping at O/A = 2.01 for H2SO4 and arsenic, respectively. The effects of varying the flowsheet and operating parameters on separation efficiency are discussed.

Arsenic and antimony extraction from high arsenic smelter ash with alkaline pressure oxidative leaching followed by Na2S leaching

In this study, a combined process of alkaline pressure oxidative leaching (APOL) and Na2S leaching was proposed to extract arsenic and antimony from high arsenic smelter ash. The arsenic was selectively dissolved into the leachate during APOL, while the antimony was separated into the residue as insoluble NaSb(OH)6. The effects of different process parameters on the extraction of arsenic and antimony were investigated based on thermodynamic calculation. The results indicated that the extraction of arsenic was as high as 96% after APOL process under the conditions: 2 mol/L of NaOH concentration, 95 °C of leaching temperature, 90 min of leaching time, 1.5 MPa of oxygen partial pressure, 10:1 of liquid-to-solid ratio. The NaSb(OH)6 generated after APOL could be converted to Na3SbS4·10H2O and thus was leached out by Na2S leaching. The optimum conditions were established as: 2.75 mol/L of Na2S concentration, 95 °C of leaching temperature, 120 min of leaching time and 10:1 of liquid-to-solid ratio, under which the extraction of antimony was as high as 97.01%. A series of tests indicated that the leaching toxicity of the leaching residue met the Chinese identification standards.

Extraction of arsenic(III) in aqueous two-phase systems: A new methodology for determination and speciation analysis of inorganic arsenic

This work utilizes the liquid–liquid extraction technique of aqueous two-phase systems (ATPS) formed by a polymer and electrolyte to develop a novel methodology for the extraction, determination, and speciation analysis of inorganic arsenic. To optimize the methodology, the following parameters were studied: pH of the system, nature of the ATPS-forming electrolyte and the polymer, tie-line length (TLL) of the system, type and concentration of extractants, and the mass ratio of the top and bottom phases. The highest extraction (%E = 98%) was obtained for an ATPS composed of L64 + Na2SO4 + H2O, at pH = 6.00, TLL = 33.55% w/w using the ammonium pyrrolidine dithiocarbamate (APDC) extractant in a molar ratio (APDC/As(III)) of 960, and with a mass ratio of 1/4. In these same conditions, As(V) was not extracted satisfactorily (%E = 18%) to ATPS top phase, with a separation factor equal to 530 after three extractions, showing the great potential of the system for the speciation analysis of inorganic arsenic. Moreover, the method was validated employing HG-ICP OES with a coefficient of determination of 0.9957 and limits of detection and quantification equal to 0.20 μg kg−1 and 0.66 μg kg−1, respectively, proving that the method is capable of detecting the low concentrations required by legislation. The relative standard deviation (RSD) values varied between 4.88 and 9.45%, and the RSD in inter-day precision was 11.07%, which are in accordance with the limits of the validation guide used by the National Institute of Metrology, Quality and Technology, COD-CGCRE-008. Furthermore, relative error rates ranged from −7.44 to 9.90% and recovery percentages were between 92.6 and 110% for the accuracy studies. This method was also applied in a spiked tap water sample, presenting a recovery value equal to 87.10%.

Estimating Arsenic Mobility and Phytotoxicity Using Two Different Phosphorous Fertilizer Release Rates in Soil

Deficiencies in phosphorus (P), an essential factor for plant growth and aided phytostabilization, are commonly observed in soil, especially near mining areas. The objective of this study was to compare the effect of P-based fertilizer types on arsenic (As) extractability and phytotoxicity in As-contaminated soil after stabilizer treatment. Different treatments with respect to the P-releasing characteristics were applied to soil to determine As mobility and phytotoxicity in P-based fertilizers, with bone meal as a slow-releasing P fertilizer and fused superphosphate as a fast-releasing P fertilizer. In addition, P fertilizers were used to enhance plant growth, and two types of iron (Fe)-based stabilizers (steel slang and acid mine drainage sludge) were also used to reduce As mobility in As-contaminated soil under lab-scale conditions. A water-soluble extraction was conducted to determine As and P extractability. A phytotoxicity test using bok choy (Brassica campestris L. ssp. chinensis Jusl.) was performed to assess the elongation and accumulation of As and P. Within a single treatment, the As stabilization was higher in steel slag (84%) than in acid mine drainage sludge (27%), and the P supply effect was higher in fused superphosphate (24740%) than in bone meal (160%) compared to the control. However, a large dose of fused superphosphate (2%) increased not only the water-soluble P, but also the water-soluble As, and consequently, increased As uptake by bok choy roots, leading to phytotoxicity. In combined treatments, the tendency towards change was similar to that of the single treatment, but the degree of change was decreased compared to the single treatment, thereby decreasing the risk of phytotoxicity. In particular, the toxicity observed in the fused superphosphate treatments did not appear in the bone meal treatment, but rather the growth enhancement effect appeared. These results indicate that the simultaneous application of bone meal and stabilizers might be proposed and could effectively increase plant growth via the stabilization of As and supplementation with P over the long term.

Extraction of elemental arsenic and regeneration of calcium oxide from waste calcium arsenate produced from wastewater treatment

Roasting waste calcium arsenate with charcoal powder was studied, serving the purpose of minimizing and/or reclaiming the waste by obtaining elemental arsenic of commercial value while regenerating recyclable CaO. Exploratory experiments were carried out to confirm the feasibility of the suggested process, in which elemental arsenic reaching the grade of 94.5% was obtained. Effects including roasting temperature, dosage of charcoal powder and roasting time were then investigated. The results showed that about 99.0% arsenic could be extracted by volatilization after the sample was roasted at 900 °C for 150 min with 14% charcoal powder, leaving the roasting residue, mainly consisting of CaO, containing arsenic as low as 0.42%. Thermodynamic calculations with respect to equilibrium compositions of the reaction system are diagramed and discussed. Attempts were made to determine and explain the mechanism by comprehensively analyzing the results of Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that As (V) in the waste calcium arsenate was reduced to As (III) before its conversion into the elementary state.

Can hydrogen sulphide gas be produced during alkaline leach of enargitic copper concentrates?

The usual answer to the question stated in the title of this manuscript would be a definitive no due to the high stability of dissolved sulphide ions in water under strong alkaline conditions; nevertheless, experimental results presented in this research shows the opposite. Two arsenic-bearing copper concentrates coming from two different Chilean mine sites were used to carry out alkaline sulphide leach experiments. One of them (Concentrate 1) exhibits a P80 of 45 μm and 3.8% arsenic while the other (Concentrate 2) has a P80 of 98 μm and 2.3% arsenic. The arsenic extractions at 60 and 90 °C after 2 h reaction for concentrates 1 and 2 are around 10 and 80% and 14 and 93%, respectively.More relevantly, notwithstanding the strong alkaline conditions used in the experiments, the production of toxic hydrogen sulphide gas was detected and measured in tests performed at 90 °C. The molar ratio between the arsenic leached and the formation of hydrogen sulphide is 20:1 and 5:1 for concentrate 1 and 2, respectively. Stoichiometric computations associated to the mechanisms of carbonation of alkaline solutions and to the thermodynamic predominance of H2S at high pH values cannot fully explain the significant quantity of gas formed during the leaching process. One hypothesis to explain the formation of the gas is mineralogy related. It involves the occurrence of specific parallel secondary reactions taking place at the solid-liquid interface triggering the increase of the local acidity and producing the gas. Due to the high concentration of sulphide ions in solution and the high temperature conditions, the gas is not fully scrubbed by the strong alkaline solution. Looking at the mineralogy of the gangue material in both concentrates, the mass ratio of the gas produced between both concentrate matches the mass ratio of galena, haematite, goethite and kaolinite present in both concentrates suggesting that these minerals would be responsible for producing the gas. Reactions associated to each one of the mentioned species are presented suggesting two different mechanisms for local acidification. This finding would have a strong impact on the implementation of the process at large scale safety-wise.

Selective leaching of arsenic from enargite concentrate using alkaline leaching in the presence of pyrite

Alkaline leaching is a promising treatment to extract arsenic from enargite. This study investigates the feasibility of leaching enargite concentrate in the presence of pyrite in alkaline solution with sodium hydroxide only. Single factor and orthogonal experiments were performed to determine the effect of sodium hydroxide concentration, temperature, leaching time and liquid-to-solid ratio on enargite dissolution and to optimize leaching conditions. The results indicate that sodium hydroxide concentration has the greatest effect on arsenic dissolution from enargite, while the liquid-to-solid ratio has the smallest effect. Finally, over 99% of arsenic was removed using optimal conditions. Characterization of the leach residue by XRD and SEM-EDS analyses showed that enargite was converted into non‑arsenic copper sulfides such as anilite (Cu7S4), geerite (Cu8S5) and djurleite (Cu31S16). This research is applicable to solving problems related to arsenic pollution.

Extraction of Metal Arsenic from Waste Sodium Arsenate by Roasting with Charcoal Powder

The current paper explored the directly reductive decomposition of waste sodium arsenate by roasting it with charcoal powder to volatilize less toxic As0 and to simultaneously obtain sodium salts with potential commercial value, serving the purpose of developing a more sustainable route to deal with the environmental issues faced by the antimony production industry in China. The process was firstly evaluated by thermogravimetric (TG) analysis and thermochemical calculations. The effects of N2 flow rate, roasting temperature, dosage of charcoal powder, and roasting time were then investigated. The results showed that the arsenic extraction could reach 99.84% under optimal conditions. The roasting residue, containing arsenic as low as 0.0598%, was a promising source for the production of Na2CO3 as expected. In addition, X-ray diffraction (XRD), scanning electron micrograph (SEM), and X-ray photoelectron spectroscopy (XPS) were conducted to reveal the roasting mechanism and formation of metal arsenic was thereby confirmed.

Use of hydrolytic enzymes as green and effective extraction agents for ultrasound assisted-enzyme based hydrolytic water phase microextraction of arsenic in food samples

In order to contribute to the development and improvement of green sample preparation techniques, a new special approach combining the principles and advantages of microextraction techniques, hydrolytic enzymes and ultrasonic radiation power is presented. This new approach is called as ultrasound assisted-enzyme based hydrolytic water phase microextraction method (UA-EH-WPME). In this study, We developed and used a solvent-free UA-EH-WPME method as innovative, green and simple sample preparation method for the extraction of arsenic (As) in rice and flour samples prior to Inductively Coupled Plasma–Mass Spectrometer (ICP-MS) determination. The UA-EH-WPME method based on the extraction of total As in 10.0 mg of food samples to 300 µL of pH 7.0 aqueous phase with the help of the 3.0 mg of α-amylase in as little as 5 min. In this method, α-amylase acts as a bond breaker agent to break down certain bonds of bio-molecules in food matrix, which lead to extraction of As from food matrix to aqueous phase. 1568A Rice Flour certified reference material was used to optimize the important analytical parameters, which were type of hydrolytic enzyme, pH, volume of aqueous phase, amount of enzyme, temperature of extraction medium and time of ultrasonic radiation, for the quantitative extraction of As from food matrix to aqueous phase. This innovative solvent-free method leads to emerge new ideas in the sample preparation field, by using the benefits of microextraction techniques, hydrolytic enzymes and ultrasonic radiation power, such as elimination of the toxic solvent usage, necessity of mg level of enzyme and food samples, very short and simple extraction process. The LOD, inter-day RSD and intra-day RSD values for the developed UA-EH-WPME/ICP-MS procedure were found as 27.3 µg kg−1, 4.27% and 6.13%, respectively.

Extractive recovery and valorisation of arsenic from contaminated soil through phytoremediation using Pteris cretica

Contamination of ground water and soil by arsenic poses serious environmental challenges globally. A possible solution to this problem is through phytoremediation using hyper-accumulating plants. This study investigates phytoremediation of soil containing 200 ± 3 mg kg−1 of arsenic using Pteris cretica ferns, and the strategies for arsenic extraction from the ferns biomass and subsequent conversions to valuable arsenic products. The Pteris cretica ferns achieved maximum arsenic accumulations of 4427 ± 79 to 4875 ± 96 mg of arsenic per kg dry biomass after 30 days. Extraction efficiencies of arsenic in the ferns fronds were 94.3 ± 2.1% for ethanol-water (1:1 v/v), 81.5 ± 3.2% for 1:1 (v/v) methanol-water, and 70.8 ± 2.9% for water alone. Molybdic acid process was used to recover 90.8 ± 5.3% of the arsenic, and 95.1 ± 4.6% of the phosphorus in the biomass extract. Quantitative precipitation of Mg3(AsO4)2 and Mg3(PO4)2 occurred on treatment of the aqueous solutions of arsenic and phosphorus after stripping at pH of 8–10. The efficiencies of Mg3(AsO4)2 and Mg3(PO4)2 precipitation were 96 ± 7.2% and 94 ± 3.4%, respectively. Arsenic nanoparticles produced from the recovered Mg3(AsO4)2, using two-stage reduction process, had average particle diameters of 45.5 ± 11.3 nm. These nanoparticles are potentially valuable for medical applications, while the Mg3(AsO4)2 could be converted to more valuable forms of arsenic or used as a pesticide, and the Mg3(PO4)2 in fertiliser. Recovery of these valuable products from phytoremediation biomass would incentivise and drive commercial industries' participation in remediation of contaminated lands.

Arsenic Geochemistry of Alluvial Sediments and Pore Waters Affected by Mine Tailings along the Belle Fourche and Cheyenne River Floodplains

Gold mining operations in the northern Black Hills of South Dakota resulted in the discharge of arsenopyrite-bearing mine tailings into Whitewood Creek from 1876 to 1977. Those tailings were transported further downstream along the Belle Fourche River, the Cheyenne River, and the Missouri River. An estimated 110 million metric tons of tailings remain stored in alluvial deposits of the Belle Fourche and Cheyenne Rivers. Pore-water dialysis samplers were deployed in the channel and backwaters of the Belle Fourche and Cheyenne Rivers to determine temporal and seasonal changes in the geochemistry of groundwater in alluvial sediments. Alluvial sediment adjacent to the dialysis samplers were cored for geochemical analysis. In comparison to US Environmental Protection Agency drinking water standards and reference concentrations of alluvial sediment not containing mine tailings, the Belle Fourche River sites had elevated concentrations of arsenic in pore water (2570 μg/L compared to 10 μg/L) and sediment (1010 ppm compared to < 34 ppm), respectively. Pore water arsenic concentration was affected by dissolution of iron oxyhydroxides under reducing conditions. Sequential extraction of iron and arsenic from sediment cores indicates that substantial quantities of soluble metals were present. Dissolution of arsenic sorbed to alluvial sediment particles appears to be affected by changing groundwater levels that cause shifts in redox conditions. Bioreductive processes did not appear to be a substantial transport pathway but could affect speciation of arsenic, especially at the Cheyenne River sampling sites where microbial activity was determined to be greater than at Belle Fourche sampling sites.

Bioaccumulation of As, Hg, and Se in tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific: tissue distribution and As speciation.

With the aim of knowing the distribution of As, Hg, and Se in skipjack (Katsuwonus pelamis, Linnaeus, 1758) and yellowfin tuna (Thunnus albacares, Bonnaterre, 1788) from the Eastern Pacific, elemental concentrations were determined in the muscle and liver; As species were also analyzed in the stomach content. Additionally, health risk for consumers was assessed. For both tunas, levels of As and Se were significantly higher (p < 0.05) in the liver than in the muscle. In K. pelamis, Hg concentrations in the muscle were significantly higher (p < 0.05) than those in the liver. In T. albacares, As, Hg, and Se showed a trend to increase with fish dimensions. Arsenic extractability was better in the muscle than in the liver of both species; in K. pelamis, As species were better extracted than in T. albacares. In both tuna species, the most extractable arsenic was arsenobetaine (AsB) and a minor part was dimethylarsinic acid (DMA). The liver contained mainly AsB with some DMA and arsenocholine (AsC). Hazard indexes (HI) indicated no risk from Hg and Se intake through these tuna species. Considering the individual contribution to the HI, Hg contributed more (80 to 86%) than Se. In the context of health risk, none of the As and Hg values were above the permissible limits; however, two samples of T. albacares (9%) and three samples of K. pelamis (12%) had Se concentrations over the limits. If Hg and Se in the edible portion of tuna are considered under the approach of the HBVSe, tuna consumption is beneficial.

Synergistic effect and different toxicities of adjuvant components of Realgar–Indigo Naturalis formula

ObjectiveRealgar–Indigo Naturalis formula (RIF) is a well-known arsenic-containing preparation that is used to treat acute promyelocytic leukemia (APL) in China. In recent multicenter clinical trials, complete remission rates in APL patients have ranged from 96.08% to 100%. RIF has a satisfactory therapeutic effect, but its safety is a widespread concern, since the preparation contains arsenic, a wide-ranging and naturally occurring toxicant. In this study, in order to determine the toxic potential of RIF, acute toxicity and sub chronic toxicity assays were performed to evaluate the toxic potential of Realgar and the adjuvant components of RIF in addition to Realgar's synergy with these adjuvant components. MethodsKM mice and Wistar rats were selected for these experiments. To evaluate acute toxicity, the toxic effects of a single dose of a gradient of concentrations of Realgar were firstly determined. Then, the toxic effects of combinations of gradient doses of Realgar and fixed doses of Indigo naturalis and Salvia miltiorrhiza were evaluated. ResultsThe results showed that when Realgar was used alone, the LD50 was 2756.73 mg/kg (equivalent to 23.6 mg/kg As2O3). However, the LD50 dropped to 936.90 mg/kg when Realgarwas used with I. naturalis. By contrast, the LD50 increased to 7538.86 mg/kg when Realgar was used with S. miltiorrhiza. Hence, I. naturalis strengthened the toxicity of Realgar, whereas S. miltiorrhiza displayed the opposite effect. The sub chronic toxicity assessment results revealed a trend that was consistent with acute toxicity. Changes in the levels of different valence states of arsenic were also taken into account. The test results of the effects of in vitro combinations of Realgar and adjuvant components on soluble arsenic dissolution showed that I. naturalis increased the level of soluble arsenic in Realgar extracts and I. naturalis suspensions when theRealgar/I. naturalis ratio was 2, 1.5, and 1.0. However, S. miltiorrhiza did not affect it. ConclusionBased on the collective experimental results presented here, it can be concluded that the toxicity of RIF is the result of the soluble arsenic in Realgar and that the I. naturalis and S. miltiorrhiza in the RIF exert completely opposite effects on the toxicity of Realgar. This maybe an intelligent explanation for the compatibility of this formula, and this RIF study may therefore be viewed as a classic case of traditional Chinese medicine research on compatibility.

Speciation analysis of arsenic in seafood and seaweed: Part II-single laboratory validation of method.

Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76-106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90-105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80-92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6-16ng g-1 arsenic.

Surface characterization of arsenopyrite during chemical and biological oxidation

The surface properties of arsenopyrite during chemical and biological oxidation were investigated by synchrotron X-ray diffraction (S-XRD), X-ray absorption near-edge structure (XANES) and scanning electron microscope (SEM), accompanying with leaching behaviors elucidation. The moderate thermophile S. thermosulfidooxdians was used as the bioleaching microorganism. Leaching experiments showed that only 16.26% and 44.37% of total arsenic extractions were obtained for sterile acid and culture medium controls, whereas 79.20% of total arsenic was recovered at the end of bioleaching. SEM indicated that new products were layered on the surface of arsenopyrite after chemical and biological oxidation. As displayed in S-XRD patterns, scorodite and elemental sulfur were formed after acid leaching, while only elemental sulfur was detected in the residue leached by acid culture medium. During bioleaching, elemental sulfur was produced from day 4 and jarosite was produced from day 9. The results of iron and arsenic L-edge XANES were in good consistence with S-XRD. The accumulation of scorodite and jarosite on arsenopyrite surface should be the main reason for the hindered dissolution of arsenopyrite during acid leaching and bioleaching. These studies are pretty meaningful for better understanding the oxidation mechanism of arsenopyrite and evaluating arsenic risk to the environment.

Efficiency evaluation of arsenic(III) adsorption of novel graphene oxide@iron-aluminium oxide composite for the contaminated water purification

Abstract Prolong consumption of arsenic-rich drinking water causes serious health problem. Aiming to minimize the problem, it is attempted to develop cheap and advanced materials for arsenic extraction from the contaminated water. Thus, multifunctional graphene oxide (GO)-incorporated iron-aluminium mixed oxide (GIAMO) composite has been prepared with five different GO content, and evaluated by batch method for the arsenic(III) removal efficiency. Among the as-prepared GIAMO samples, three samples consisting 1.0, 2.0 and 3.0 g of GO show equally good (92–95%) arsenic(III) removal efficiency, which is 30–35% higher than pristine iron-aluminium oxide (IAMO) from an aqueous solution (5.0 mg AsIII·L−1) at pH 7.0 (± 0.2) and 303 K. Thus, 1.0 g GO-inserted GIAMO (GIAMO-1) sample was characterized as microcrystalline (10–15 nm) with BET surface area about 1.45 times higher than IAMO and investigated for the arsenic(III) adsorption. Optimized pH for arsenic(III) adsorption is 6.0–8.0. The kinetic data agree more closely with pseudo-first order equation (R2 = 0.98–0.99) than pseudo-second order equation (R2 = 0.92–0.93). The equilibrium data describe the Langmuir isotherm (R2 = 0.97–0.98) better than the Freundlich isotherm (R2 = 0.91–0.92), showing the Langmuir monolayer capacity 42.2836 mg·g−1 at 293 K which drops to 24.9170 mg·g−1 at 313 K. High negative enthalpy change (ΔH° ∼ −224 kJ. mol−1) is responsible for the spontaneous reaction (ΔG° = negative) despite unfavorable entropy change (ΔS° = −0.71 kJ. mol−1). The order of competitive effect of PO43−, SO42− and HCO3− on arsenic(III) removal efficiency is PO43− > SO42− > HCO3−. However, the high HCO3− (> 200 mg·L−1) enhances the arsenic(III) removal efficiency of this material. 2.0 M NaOH can regenerate arsenic adsorbed GIAMO-1 only up to 50–60%. 0.65 g. of composite per L of high arsenic (Astotal: 0.115 mg L−1) groundwater can upgrade to potable standard, encouraging possible safe use for high arsenic water treatment. Highly negative enthalpy change, poor regeneration, FTIR, XRD and CV analyses of arsenic-rich solid suggested that arsenic(III) is stabilized over the solid surface without oxidation by surface complex formation.