Arsenic Solution Research Articles

Simple colorimetric assay using pectin hydrogel reagent coupled with camera-based photometry for trace arsenic determination.

Humans mainly ingest arsenic through contaminated drinking water, causing serious health effects. The World Health Organization (WHO) has set the permissible limit of arsenic in drinking water at 0.01 mg/L and concentrations should be regularly determined to ensure a safe supply. In this study, a leucomalachite green (LMG) pectin-based hydrogel reagent was prepared that selectively reacted with arsenic over other metals including manganese, copper, lead, iron, and cadmium. Pectin, optimized at 0.2% (w/v), was used to form the hydrogel matrix. Arsenic reacts with potassium iodate in sodium acetate buffer medium to liberate iodine that then oxidizes LMG entrapped in pectin hydrogel to form a blue product. Camera-based photometry/ImageJ software was used to monitor the color intensity, eliminating the need for a spectrophotometer. The intensity of gray in the red channel was chosen as optimal for the red, green, and blue (RGB) analysis. The colorimetric assay revealed a dynamic detection range toward arsenic solution standards of 0.003-1 mg/L, covering the WHO recommendation of below 0.01 mg/L arsenic in drinking water. The assay gave recovery rates between 97 and 109% at a 95% confidence interval, with precision of 4-9%. Concentrations of arsenic in the spiked drinking water, tap water, and pond water samples monitored by the developed method agreed well with conventional inductively coupled plasma optical emission spectrometry. This assay showed promise for on-site quantitative analysis of arsenic in water samples.

Effect of arsenic exposure on MDA, SOD, H2O2 and TNF-α levels of uterus homogenate of female Sparague-Dawleys rats

Background and Aim: Arsenic exposure to the body through the oral, dermal, and inhalation routes have a detrimental impact on health, including women’s reproductive health. However, the effect of arsenic exposure through the vulva of women is unclear. The present study therefore examined the effects of long-term arsenic exposure of vulva on uterus inflammation mediated by oxidative stress and inflammatory mechanism. Materials and Methods: Female Rattus norvegicus L was used as the animal model and the arsenic were exposed through vulvar immersion. The arsenic solution was made into four concentrations while the duration of exposure was made in four-time combinations. Uterus inflammation was assessed through histopathological observation of uterus tissue through hematoxylin and eosin (H&E) staining. Oxidative stress was assessed using malondialdehyde (MDA), superoxide dismutase (SOD), and hydrogen peroxide (H2O2); while inflammatory profile was assessed by measuring using tumor necrosis factor α (TNFα). Results: Our data suggested that inflammation could occur at the permissible quality standard concentrations when arsenic was exposed for more than two weeks. At higher concentrations and a longer exposure time, arsenic exposure could lead to chronic inflammation. Arsenic exposure was able to increase the levels of MDA and H2O2 and reduced the SOD suggesting stress oxidative of the organ. Arsenic also could increase the level of TNFα at any concentration after 6 and 8 weeks of exposure suggesting the inflammation process in the uterus. Conclusion: Continuous exposure of vulva with arsenic could induce oxidative stress and chronic inflammation of the uterus. Further study to investigate this finding in human is critical as basic to propose health campaign program to the community in the high arsenic regions.

The solubility behavior of sodium arsenate in NaOH solution based on the Pitzer model

Alkaline leaching is an effective method for dealing with arsenic-containing resources. Arsenic is dissolved in an alkaline solution in the form of arsenate, but the lack of relevant basic data has caused difficulties in the theoretical analysis during production and research. The dissolution behavior of arsenic in the solution was systematically studied in this paper. The solubility behavior of the self-made sodium arsenate in water and NaOH solution were measured. The research on sodium arsenate solution was carried out to obtain the quasi-solubility product using the Pitzer model, and the effect of temperature and NaOH concentration on the solubility and quasi-solubility product of sodium arsenate was clarified.

Modified oyster shell powder with iron (II) sulfate heptahydrate to improve arsenic uptake in solution and in contaminated soils.

Arsenic is a metalloid whose presence can be due to natural or anthropological causes. It is considered as a toxic chemical that puts human health at high risk. In this study, we evaluated a novel modified oyster shell (MOS) that was coated with iron (II) sulfate heptahydrate using two different proportions through batch sorption experiments in an arsenic solution and in arsenic-contaminated soils. The arsenic solution was prepared using As(III)-standard solution. The arsenic contaminated soils were extracted from a contaminated site in Cheonan, South Korea, where the average arsenic concentration of the soil was reported as 136.28mg/kg. Different doses of oyster shell and modified oyster were used to understand the effect of the addition of iron (II) sulfate heptahydrate via sorption batch experiments in solution and sorption tests in soils. The sorption tests were conducted with 50g of contaminated soil; then, 150g of soils was used for the pot cultivation tests, and finally, 150g of contaminated soils was used for column percolation test. Through the experiments, the authors observed a comparable improvement of arsenic stabilization from 10 to 60% with the addition of iron (II) sulfate heptahydrate to oyster shell.

Application of δ-MnO2 and biochar materials in an arsenic-contaminated groundwater.

Two activated biochar materials, peanut char (δ-MnO2 /A-PC) and corn char (δ-MnO2 /A-CC), were used to treat an arsenic solution containing 97.5% As(III) and 2.5% As(V). After reacting with δ-MnO2 /A-PC for 24 h, 18.8% of As(III) and 35.4% of As(V) remained in the solution, revealing that some As(III) was oxidized to As(V) and the other was removed by adsorption. However, δ-MnO2 /A-CC caused the solution to retain 15.6% of As(III) and 41.7% of As(V) under the same conditions, indicating that δ-MnO2 /A-CC had higher oxidation for arsenic species than δ-MnO2 /A-CC. Adsorption capacities for δ-MnO2 /A-PC and δ-MnO2 /A-CC to arsenic were 1.50 and 1.53 mg/g in a solution with 0.5ppm As(III), respectively. After coating with δ-MnO2 , the proportion of mesopore surface areas of δ-MnO2 /A-CC increased from 33.3% to 79.0%, but their mesopore volumes increased from 67.6% to 89.4%. Fourier-transform infrared spectroscopy and X-ray diffraction analyses demonstrated that δ-MnO2 was coated onto the surfaces of the biochars. The 600°C-ACC had a higher specific surface area, 221 m2 /g, than the δ-600°C-APC, 81.5m2 /g; δ-MnO2 /A-CC could attach more Mn (38.2%) than δ-MnO2 /A-PC (27.8%). The elemental analysis revealed that δ-MnO2 /A-PC and δ-MnO2 /A-CC had similar carbon contents of 26.2%. PRACTITIONER POINTS: The δ-MnO2 /biochar adsorbent can oxidize As(III) into As(V) in the groundwater. δ-MnO2 /biochar adsorbed large amounts of As(III) and As(V). Adsorbent that contains more δ-MnO2 has a higher oxidation capacity. The δ-MnO2 /biochar made from corn stalks could combine with more δ-MnO2 .

Arsenic removal from solution using nano-magnetic compound: optimization modeling by response surface method.

This study was aimed to investigate the effectiveness of compounds containing iron and manganese to reduce the mobility of arsenic and its effective adsorption and optimize the arsenic adsorption process by CCD. In this study, MnFe2O4 nanoparticles (MFO-n) were synthesized using the co-precipitation method to remove arsenic and reduce its toxicity in solution. Several tests including Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), X-ray fluorescence (XRF), and Brunauer-Emmett-Teller (BET) tests were used to characterize the synthesized MFO-n. To model and optimize the As adsorption process using the response surface methodology, four independent variables affecting the efficiency of arsenic adsorption were investigated. These variables including pH (3 to 11), concentration of arsenic in solution (1000 to 4000µg/L), concentration of nanoparticles (1 to 5g/L), and time (15 to 195min) were investigated. The central composite design (CCD) approach was used to design the experiments and optimize the model parameters. The variance analysis indicated that the prediction of As adsorption from solution by the synthesized nanoadsorbent using the CCD model was well performed (p < 0.0001) with high accuracy (R2 = 0.97). The results further indicated that the optimum quantity of pH, concentration of nanoparticles, time, and initial concentration of As are 5, 2g/L, 60min, and 3250µg/L, respectively. The highest As elimination from the solution was estimated to be 94.77%. Our results further indicated that MFO-n had high efficiency in eliminating both toxic arsenic species from the solution.

Electrochemical Immobilization of Arsenic

Arsenic handling and immobilization are critical issues in the mining of sulfarsenide minerals, due to arsenic’s toxicity to the environment. Significant amount of arsenic can be present in Cu, Zn, Ni, and Co minerals. Cobaltite (CoAsS) for example, is one of those sulfides from which cobalt can be mined as the primary mineral. However, cobalt extraction from cobaltite generates equivalent mass of arsenic per extracted cobalt. To unlock the domestic cobalt production, efficient arsenic immobilization techniques are needed. Compared to traditional hydrometallurgical and pyrometallurgical processes, an electrochemical method is proposed to efficiently immobilize arsenic from cobaltite. An electrochemical cell was assembled to promote the immobilization of arsenic, in the presence of iron, via the precipitation of crystalline scorodite (FeAsO4 · 2H2O). Various electrochemical mechanisms were studied to maximize the oxidation and precipitation rates, such as galvanostatic and potentiostatic techniques. Results using both surrogate solution of arsenic, iron, and cobalt, as well as cobaltite solution show high immobilization rates of arsenic.

Magnetic Torus Microreactor as a Novel Device for Sample Treatment via Solid-Phase Microextraction Coupled to Graphite Furnace Atomic Absorption Spectroscopy: A Route for Arsenic Pre-Concentration.

This work studied the feasibility of using a novel microreactor based on torus geometry to carry out a sample pretreatment before its analysis by graphite furnace atomic absorption. The miniaturized retention of total arsenic was performed on the surface of a magnetic sorbent material consisting of 6 mg of magnetite (Fe3O4) confined in a very small space inside (20.1 µL) a polyacrylate device filling an internal lumen (inside space). Using this geometric design, a simulation theoretical study demonstrated a notable improvement in the analyte adsorption process on the solid extractant surface. Compared to single-layer geometries, the torus microreactor geometry brought on flow turbulence within the liquid along the curvatures inside the device channels, improving the efficiency of analyte–extractant contact and therefore leading to a high preconcentration factor. According to this design, the magnetic solid phase was held internally as a surface bed with the use of an 8 mm-diameter cylindric neodymium magnet, allowing the pass of a fixed volume of an arsenic aqueous standard solution. A preconcentration factor of up to 60 was found to reduce the typical “characteristic mass” (as sensitivity parameter) determined by direct measurement from 53.66 pg to 0.88 pg, showing an essential improvement in the arsenic signal sensitivity by absorption atomic spectrometry. This methodology emulates a miniaturized micro-solid-phase extraction system for flow-through water pretreatment samples in chemical analysis before coupling to techniques that employ reduced sample volumes, such as graphite furnace atomic absorption spectroscopy.

The Effect and Activity of Free Radical Enzymes Due to Arsenic Exposure Through the Vulva and Vagina

BACKGROUND OF THE STUDY: Geogenic arsenic is ubiquitous, found in water and soil that is used daily, can be exposed to the female body through the genital organs. The vulva and vagina are open channels that allow toxic agents to enter the internal genitalia and distributed throughout the body.&#x0D; AIM OF THE STUDY: This study investigated the effects of vaginal arsenic exposure via vulvar immersion and vaginal douching in Rattus norvegicus on the damage of uterus and ovaries through oxidative mechanisms (MDA, SOD, and H₂O₂).&#x0D; METHODOLOGY: The experimental animals were divided into three treatment groups, i.e., K0 (control group), K1 (group treated with vulvar immersion in 0.8 mg/L arsenic solution), and K2 (group treated with vaginal douching using 0.5-mL of 0.8 mg/L arsenic solution). For each group, the treatment was repeated six times and carried out for fourteen days. Before the study, a seven-day acclimatization period was conducted for adaptation purposes. The experimental animals were euthanized using ketamine xylazine. The uterus and ovaries were collected for MDA, SOD, and H₂O analysis, as well as histopathology examination.&#x0D; RESULTS: The vaginal douching group had the highest MDA level both on the uterus (210.66±4.92μM) and the ovaries (214.67±2.50 μM). The immersion group also experienced an increase in MDA in the uterus (198.66±3.33μM) and ovaries (206.33± .21μM). However, a higher level of MDA was found in the ovaries. The highest H₂O₂ level was also found in the uterine and ovarian organs in the douching group. In contrast, the lowest SOD levels of uterine and ovarian were identified in the vaginal douching group. Arsenic exposure through vaginal immersion and douching affected the uterine MDA, SOD, and H₂O levels (Ρ&lt;0.05). Arsenic exposure through vaginal douching also affected the ovarian MDA, SOD, and H₂O levels (Ρ&lt;0.05). There was a significant difference in the mean of inflammatory cells (infiltrated neutrophils, macrophages, and lymphocytes) in the uterus and ovaries in the control, immersion, and vaginal douching groups (Ρ&lt;0.05).&#x0D; CONCLUSION: Exposure to 0.8 mg/L arsenic solution through vulvar immersion and vaginal douching can cause oxidative stress and trigger inflammation of the uterine and ovarian tissue.

Fundamental research on selective arsenic removal from high-salinity alkaline wastewater

The alkaline leaching process of arsenic-containing solid waste discharged during nonferrous metal smelting affords typical high-salinity alkaline arsenic-containing wastewater (HSAW). In this study, for the first time, Me (Ca2+ and Mg2+)–AsO43−–OH−–H2O and Me (Ca2+ and Mg2+)–AsO43−–CO32−–H2O systems are studied based on a thermodynamic equilibrium diagram and an arsenic removal experiment, proving that the removal of arsenic using single metal ions in the presence of CO32− is infeasible because of carbonate coprecipitation. Based on this observation, a new method that uses magnesium ammonium complex salts (MACSs) for HSAW treatment is proposed. Based on the thermodynamic calculations of the Mg2+–AsO43−–NH4+–CO32−–H2O system and the arsenic removal experiment, carbonate and arsenate can be selectively separated by the formation of magnesium ammonium arsenate (NH4MgAsO4·6H2O). In an arsenic solution containing 150-g/L Na2CO3, the arsenic removal rate and the arsenic grade of the precipitation product reach 90.16% and 27.13%, respectively, when the molar ratios of Mg2+/NH4+:As(V) are 1.8:1 and 2:1, respectively. The proposed method is successfully employed for treating a leaching solution of alkaline arsenic slag discharged during antimony smelting. The findings of this study will broaden the basic theory of HSAW treatment and lay a foundation for the resource treatment of arsenic-containing solid waste.

Silica- Iron Oxide Nanocomposite Enhanced with Porogen Agent Used for Arsenic Removal.

This study aims to remove arsenic from an aqueous medium by adsorption on a nanocomposite material obtained by the sol–gel method starting from matrices of silica, iron oxide and NaF (SiO2/Fe(acac)3/NaF). Initially, the study focused on the synthesis and characterization of the material by physico–chemical methods such as: X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, atomic force microscopy, and magnetization. Textural properties were obtained using nitrogen adsorption/desorption measurements. The zero load point, pHpZc, was also determined by the method of bringing the studied system into equilibrium. In addition, this study also provides a comprehensive discussion of the mechanism of arsenic adsorption by conducting kinetic, thermodynamic and equilibrium studies. Studies have been performed to determine the effects of adsorbent dose, pH and initial concentration of arsenic solution, material/arsenic contact time and temperature on adsorption capacity and material efficiency. Three theoretical adsorption isotherms were used, namely Langmuir, Freundlich and Sips, to describe the experimental results. The Sips isotherm was found to best describe the experimental data obtained, the maximum adsorption capacity being ~575 µg As(III)/g. The adsorption process was best described by pseudo-second order kinetics. Studies have been performed at different pH values to establish not only the optimal pH at which the adsorption capacity is maximum, but also which is the predominantly adsorbed species. The effect of pH and desorption studies have shown that ion exchange and the physiosorption mechanism are implicated in the adsorption process. From a thermodynamic point of view, parameters such as ΔG°, ΔH° and ΔS° were evaluated to establish the mechanism of the adsorption process. Desorption studies have been performed to determine the efficiency of the material and it has been shown that the material can be used successfully to treat a real-world example of deep water with a high arsenic content.

Nature of surface interactions among Fe3O4 particles and arsenic species during static and continuous adsorption processes

This study explored the mechanistic approaches to understand the adsorptive removal of arsenic species from aqueous medium in static and continuous adsorption processes. Fe3O4, an adsorbent is this study, is synthesized by reverse coprecipitation method using iron oxide waste of steel industry as a starting material. The surface properties of Fe3O4 were confirmed by several characterization techniques including XRD, XPS, SEM, TEM, FTIR, EDS, Raman, and zeta potential. The arsenic removal rate was found to be dependent on the synthesis pathway of Fe3O4 especially, the pH during reverse coprecipitation. Beside synthesis conditions, the adsorbent size, adsorbent quantity, an initial concentration of arsenic species, contact time, and the solution pH also influenced the arsenic removal rate. Over 90% arsenate and arsenite concentrations were effectively removed from the solution in initial 10 min of contact between Fe3O4 and arsenic solution. The adsorption sites of Fe3O4 were successfully reclaimed by regeneration of used particles with 0.1N NaOH solution. To assess the practicability of the Fe3O4 particles in continuous adsorption process, particles were used in column and plug flow reactors and the adsorption profile is examined under different operational conditions (operational scheme, influent flow direction, contact time, initial arsenic concentration, etc.). The operational performances of reactors confirmed that the synthesized particles have the potential to be successfully applied for arsenic removal from water.

Arsenopyrite Dissolution and Bioscorodite Precipitation by Acidithiobacillus ferrivorans ACH under Mesophilic Condition

Arsenopyrite is the most abundant arsenic-bearing sulfide mineral in the lithosphere, usually associated with sulfide gold ores. The recovery of this highly valuable metal is associated with the release of large quantities of soluble arsenic. One way to mitigate the effects of high concentrations of arsenic in solution is to immobilize it as scorodite precipitate, a more stable form. Hence, we addressed the scorodite formation capacity (under mesophilic conditions) of psychrotolerant Acidithiobacillus ferrivorans ACH isolated from the Chilean Altiplano. Bio-oxidation assays were performed with 1% arsenopyrite concentrate as unique energy source and produced solids were evaluated by X-ray diffraction (XRD) and QEMSCAN analysis. Interestingly, the results evidenced scorodite generation as the main sub-product after incubation for 15 days, due to the presence of the microorganism. Moreover, the QEMSCAN analysis support the XRD, detecting a 3.5% increase in scorodite generation by ACH strain and a 18.7% decrease in arsenopyrite matrix, implying an active oxidation. Finally, we presented the first record of arsenopyrite oxidation capacity and the stable scorodite production ability by a member of A. ferrivorans species under mesophilic conditions.

Loading ferric lignin on polyethylene film and its influence on arsenic-polluted soil and growth of romaine lettuce plant.

This work developed a composite (Pe-FeLs) which loaded ferric lignin on polyethylene film (PE film) by chemical modification and physico-chemically characterized by Microscope, FESEM with elemental mapping analysis, and XRD. Microscope pictures showed that chemical modification did not destroy the appearance of PE film. The FESEM images of Pe-FeLs showed the well-distributed clusters could be clearly seen and most of the particles were spherical morphology. Elemental mapping of individual element on Pe-FeLs clearly indicated the existing of iron. The XRD pattern showed the amorphous hydroxides of iron on Pe-FeLs. In arsenic solution, the total arsenic adsorption capacity of Pe-FeLs was much higher than that of ferric lignin and PE, which showed Pe-FeLs had the ability to adsorb arsenic. For making Pe-FeLs work well in the soil, a Pe-FeLs system was set up with plastic grid plate, PE film with holes, Pe-FeLs, PE film, and plastic grid plate from the upper to bottom in order. With applying Pe-FeLs system under the soil, arsenic was significantly reduced by 25.5 ~ 53.4% in heavily, moderately, and lower arsenic-polluted soils, the biomass of the romaine lettuce increased and arsenic accumulation in the romaine lettuce decreased.

Critical Evaluation of Specific Efficacy of Preparations Produced According to European Pharmacopeia Monograph 2371.

European Pharmacopoeia monograph 2371 describes the production of homeopathic preparations. A specific efficacy of these preparations in high dilution levels is questionable in view of basic scientific principles. There is empirical evidence for such effects, for example in a Lemna-intoxication bioassay published 2010. To test the replicability and robustness of this bioassay, we conducted two experimental series (five independent blinded and randomised experiments each). The specimen of Lemna gibba L., clone-number 9352, were stressed in arsenic solution for 48 h (158 mg/L AsNa2HO4 (250 mg/L in series 2)), then grew in either As2O3 preparations produced according to Eu. Pharm. Monogr. 2371 or control solution. Comparing the area-related relative growth rate of day 3–9 (rgr 3–9) between treatment and control groups for each series showed differences that were not significant in series 1 (p = 0.10), significant in series 2 (p = 0.04) and significant in the pooled data of both series (p < 0.01). The effect direction (rgr 3–9 increase) was comparable to experiments of 2010, but the effect size was smaller, likely due to a changed light cycle. These results are not compatible with the hypothesis that the application of European Pharmacopoeia monograph 2371 results in pharmaceutical preparations without specific effects. Further studies are needed to investigate a potential mode of action explaining these effects.

Polyvinylidene fluoride/boehmite nanocomposite membrane for effective removal of arsenate ion from water

Groundwater arsenic contamination is a serious threat that has affected the health of 130 million people globally. Long-term exposure to arsenic leads to arsenic poisoning, i.e., arsenicosis. Therefore, the development of new technology to reject arsenic from water has been increased. Polyvinylidene fluoride (PVDF) polymer possesses outstanding properties mainly as thermal stability, chemical and mechanical resistance. Boehmite, a polymorphic aluminium oxide, is an essential industrial mineral used as an adsorbent due to its ability to retain high surface area. It has a positive charge, and its surface renders it easy for compounds with negative charges to be attached by electrostatic attraction. Also, the nanoparticles have a high isoelectric value. High adsorption is expected on a higher isoelectric point value. PVDF/boehmite composite membrane was prepared using solvent casting method at room temperature. The nanoparticles were added in Al/As (w/w) ratio of 0:1, 50:1, 200:1 and 500:1. Al/As ratio of 200:1 has shown the best result in batch process, and in static adsorption study, 65% rejection of arsenate ion was achieved from 100 μg/L arsenate solution in 1 h. Flux was calculated in a dead-end filtration setup at 1 bar trans-membrane pressure. The water flux of the membranes was in the range of 62 to 270 L/m2h.

As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria.

Iron oxides/oxyhydroxides, namely maghemite, iron oxide-silica composite, akaganeite, and ferrihydrite, are studied for AsV and AsIII removal from water in the pH range 2–8. All sorbents were characterized for their structural, morphological, textural, and surface charge properties. The same experimental conditions for the batch tests permitted a direct comparison among the sorbents, particularly between the oxyhydroxides, known to be among the most promising As-removers but hardly compared in the literature. The tests revealed akaganeite to perform better in the whole pH range for AsV (max 89 mg g−1 at pH0 3) but to be also efficient toward AsIII (max 91 mg g−1 at pH0 3–8), for which the best sorbent was ferrihydrite (max 144 mg g−1 at pH0 8). Moreover, the study of the sorbents’ surface chemistry under contact with arsenic and arsenic-free solutions allowed the understanding of its role in the arsenic uptake through electrophoretic light scattering and pH measurements. Indeed, the sorbent’s ability to modify the starting pH was a crucial step in determining the removal of performances. The AsV initial concentration, contact time, ionic strength, and presence of competitors were also studied for akaganeite, the most promising remover, at pH0 3 and 8 to deepen the uptake mechanism.

Effects of aluminum incorporation on the schwertmannite structure and surface properties.

Schwertmannite is a common nanomineral in acid sulfate environments such as Acid Mine Drainage (AMD) and Acid Sulfate Soils (ASS). Its high surface area and positively charged surface result in a strong affinity towards toxic oxyanions such as arsenate in solution. However, natural precipitation of schwertmannite also involves the accumulation of other impurities, in particular aluminum, an element that is often incorporated into the structure of Fe-oxide minerals, such as goethite and ferrihydrite, affecting their structural and surface properties. However, little is known about the effect of Al incorporation in schwertmannite on the removal capacity of toxic oxyanions found in AMD and ASS (e.g. arsenate). In this paper, schwertmannite samples with variable Al concentration were synthetized and employed in arsenate adsorption isotherm experiments at a constant pH of 3.5. Solid samples before and after arsenate adsorption were characterized using high energy X-ray diffraction and pair distribution function analyses in order to identify structural differences correlated with the Al content as well as variations in the coordination of arsenate adsorbed on the mineral surface. These analyses showed limited Al accumulation on schwertmannite (up to 5%) with a low effect on its structure. The maximum arsenate sorption capacity (258 mmolH2AsO4 molFe-1) was in the range of that with pure schwertmannite, but a higher proportion of inner-sphere coordination was observed. Finally, Al was found to desorb from schwertmannite, with adsorbed arsenate preventing this effect and increasing the stability of the mineral. These results are useful to interpret observations from the field, in particular from river water affected by AMD and ASS, where similar conditions are observed, and where aluminum incorporation is expected.

Functionalised carbon from Musa Balbisiana stems - a byproduct of edible alkali preparation and a suitable adsorbent for fluoride and arsenic from contaminated water

A popular traditional food additive amongst the Assamese people of North East India is Kol-Khar or banana peel alkali. The preparation of this edible alkali is carried out by aqueous extraction of ashes obtained from slow burning of hard sun dried banana stems and peels of Musa Balbisiana. The alkali is extracted from the ashes by water washing. The carbon fraction obtained in the process remains as a byproduct. This carbon due to exposure to high alkalinity during alkali extraction undergoes a base mediated surface functionalisation. From FESEM images, some holes and cave type openings are found on the surface of this carbon. From EDX spectra the chemical composition of the carbon was obtained. The number of acidic and basic sites so formed could be determined by Boehm titration. This functionalized waste bio carbon was used as an adsorbent for fluoride and arsenic from ground water. Effect of different parameters like adsorbent dose, contact time, temperature and pH of adsorbate on defluoridation capacity of the material was studied in the present work. The adsorption isotherm and adsorption kinetics were also investigated. From batch mode study 73 % removal of fluoride and 79.8 % removal of arsenic are obtained from each 5 mg/L spiked fluoride and arsenic solution.

Removal of Arsenic Through the Process of Biosorption

Increase in human population and its need for its lifestyle improvisation leads to nature at risk. One of the natural source on which all live forms depends is water. Water pollution due to non- essential heavy metals is very common. Non- essential heavy metals are very toxic and are threats to human life and other life forms also. Arsenic is one of the non-essential heavy metal which is toxic as well as carcinogenic. Problem due to arsenic pollution is continuously increasing in Asian countries. Arsenic pollution in drinking water along with in paddy fields is global problem all around the world. In almost all regions of West Bengal, India concentration of arsenic in rice continuously increases. Arsenic toxicity is very serious for humans and causes various diseases. Hence, it is necessary to remove arsenic from aqueous solutions to protect human life from its toxic effect. This paper focuses on removal of arsenic using low cost adsorbents through process of biosorption. For removal of arsenic in this study a mixed biosorbent is prepared by mixing roots of Shatavari and Erandmool, leaves of Sadabahar, fruit of Nimbu and panchang of Brahmi. For removal of arsenic ultraviolet spectroscopy method is used here based on the principle of that arsenic when treated with acidified potassium iodate to liberate iodine. The Liberated iodine bleaches the violet colour of azure B which is measured at 644 nm. Results obtained show that maximum percentage of arsenic removal was obtained at 0.5 and 1.0 g of adsorbent dose at 3 mg/l and 5 mg/l of initial arsenic concentration in 3 hour contact time, pH of solution 7 and 8 and 40 rpm agitation speed. Maximum percentage removal obtained at pH 7 by 0.5 g adsorbent dose at 5 mg/l arsenic solution was 82 %. Adsorption isotherm model which supports arsenic removal was Freundlich model whose r2 value obtained was 0.99 and value of n is 1.78 and Kf is 2.53.