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Academic literature on the topic 'Arsenic – Oxidation'

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Published: 4 June 2021
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Journal articles on the topic "Arsenic – Oxidation"

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Sorlini, S., F. Gialdini, and M. Stefan. "Arsenic oxidation by UV radiation combined with hydrogen peroxide." Water Science and Technology 61, no. 2 (January 1, 2010): 339–44. http://dx.doi.org/10.2166/wst.2010.799.

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Arsenic is a widespread contaminant in the environment around the world. The most abundant species of arsenic in groundwater are arsenite [As(III)] and arsenate [As(V)]. Several arsenic removal processes can reach good removal yields only if arsenic is present as As(V). For this reason it is often necessary to proceed with a preliminary oxidation of As(III) to As(V) prior to the removal technology. Several studies have focused on arsenic oxidation with conventional reagents and advanced oxidation processes. In the present study the arsenic oxidation was evaluated using hydrogen peroxide, UV radiation and their combination in distilled and in real groundwater samples. Hydrogen peroxide and UV radiation alone are not effective at the arsenic oxidation. Good arsenic oxidation yields can be reached in presence of hydrogen peroxide combined with a high UV radiation dose (2,000 mJ/cm2). The quantum efficiencies for As(III) oxidation were calculated for both the UV photolysis and the UV/H2O2 processes.
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Kato, Tatsuya, Yohei Kawasaki, Masakazu Kadokura, Kohei Suzuki, Yasuhiro Tawara, Yoshiyuki Ohara, and Chiharu Tokoro. "Application of GETFLOWS Coupled with Chemical Reactions to Arsenic Removal through Ferrihydrite Coprecipitation in an Artificial Wetland of a Japanese Closed Mine." Minerals 10, no. 5 (May 23, 2020): 475. http://dx.doi.org/10.3390/min10050475.

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Passive systems that utilize a natural power such as a pond, plant, or microorganisms, is expected to be a cost-effective method for acid mine drainage (AMD) treatment. The Ningyo-toge mine, a non-operational uranium mine located in Okayama Prefecture, Japan, generates AMD containing arsenic and iron. To quantitatively study arsenic and iron ion removal in an artificial wetland and pond, chemical reactions were modeled and incorporated into the GETFLOWS (general-purpose terrestrial fluid-flow simulator) software. The chemical reaction models consisted of arsenite and ferrous oxidation equations and arsenic adsorption on ferrihydrite. The X-ray diffraction analysis of sediment samples showed ferrihydrite patterns. These results were consistent with the model for arsenite/ferrous oxidation and arsenic adsorption on ferrihydrite. Geofluid simulation was conducted to simulate mass transfer with the utilized topographic model, inlet flow rate, precipitation, and evaporation. The measured arsenic and iron ions concentrations in solution samples from the wetland and pond, fitted well with the model. This indicated that the main removal mechanism was the oxidation of arsenite/ferrous ions and that arsenic was removed by adsorption rather than dilution.
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Spaziani, Fabio, Yuli Natori, Yoshiaki Kinase, Tomohiko Kawakami, and Katsuyoshi Tatenuma. "Elementary Iodine-Doped Activated Carbon as an Oxidizing Agent for the Treatment of Arsenic-Enriched Drinking Water." Water 11, no. 9 (August 27, 2019): 1778. http://dx.doi.org/10.3390/w11091778.

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An activated carbon impregnated with elementary iodine (I2), named IodAC, characterized by oxidation capability, was developed and applied to oxidize arsenite, As(III), to arsenate, As(V), in arsenic-rich waters. Batch and column experiments were conducted to test the oxidation ability of the material. Comparisons with the oxidizing agents usually used in arsenic treatment systems were also conducted. In addition, the material has been tested coupled with an iron-based arsenic sorbent, in order to verify its suitability for the dearsenication of drinking waters. IodAC exhibited a high and lasting oxidation potential, since the column tests executed on water spiked with 50 mg/L of arsenic (100% arsenite) showed that 1 cc of IodAC (30 wt% I2) can oxidize about 25 mg of As(III) (0.33 mmol) before showing a dwindling in the oxidation ability. Moreover, an improvement of the arsenic sorption capability of the tested sorbent was also proved. The results confirmed that IodAC is suitable for implementation in water dearsenication plants, in place of the commonly used oxidizing agents, such as sodium hypochlorite or potassium permanganate, and in association with arsenic sorbents. In addition, the well-known antibacterial ability of iodine makes IodAC particularly suitable in areas (such developing countries) where the sanitation of water is a critical topic.
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Song, Wei Feng, Qi Deng, Li Ying Bin, Wei Wang, and Chun Wu. "Arsenite Oxidation Characteristics and Molecular Identification of Arsenic-Oxidizing Bacteria Isolated from Soil." Applied Mechanics and Materials 188 (June 2012): 313–18. http://dx.doi.org/10.4028/www.scientific.net/amm.188.313.

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Arsenite oxidation characteristics were studied through domesticated bacteria from soil added arsenic artificially, which came from Dinghu Mountain Natural Reserve of Zhaoqing, Guangdong, China. Two individual bacterial strains were selected as arsenite-oxidizing bacteria by reaction of silver nitrate and detected in community DNA fingerprints generated by PCR coupled with denaturing gradient gel electrophoresis. Physiological, biochemical and arsenite oxidation characteristics of arsenic-oxidizing bacteria were researched. They were gram-negative and rod-shaped bacteria, which were 99% related to Alcaligenes sp.(strain H) and 100% related to Agrobacterium sp. (strain Q) respectively. The arsenic-oxidizing experiment showed that the optimal temperature and pH were 30°Cand 9.0 respectively for both strains. Strain H was an efficient arsenite-oxidizing bacteria. It oxidized As(III) by nearly 100% after 21 hours. Therefore, It was detected as the most perspective strains in this study.
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Rowland, H. A. L., A. G. Gault, J. M. Charnock, and D. A. Polya. "Preservation and XANES determination of the oxidation state of solid-phase arsenic in shallow sedimentary aquifers in Bengal and Cambodia." Mineralogical Magazine 69, no. 5 (October 2005): 825–39. http://dx.doi.org/10.1180/0026461056950291.

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AbstractDetermination of the solid-phase arsenic speciation in sediments hosting high-arsenic groundwaters, utilized for drinking and irrigation in Bengal, SE Asia and elsewhere is important in order to understand the biogeochemistry of arsenic. Despite this, there is a relative paucity of speciation data for solid-phase arsenic in such systems, due to preservation difficulties, low arsenic concentrations in the sediments, multiple coordination environments and sample heterogeneity. In this study, X-ray absorption near edge structure spectroscopy was used in conjunction with linear least-squares fitting of model compounds to determine the oxidation state of arsenic in sediments from West Bengal and Cambodia. Whatever the collection and storage method used, substantial oxidation of arsenic was commonly observed over periods of weeks to several months. Sands were particularly susceptible to changes in arsenic oxidation state during storage. Analysis within two or three weeks of collection is therefore recommended, whilst on-site storage under a nitrogen atmosphere immediately after collection is particularly recommended for the preservation of sandy samples. Both muds and sands from West Bengal and Cambodia were dominated by arsenite (As(III)) with <35±10% arsenate (As(V)). Complete oxidation to arsenate was never observed suggesting that a significant proportion of the sedimentary arsenic is inaccessible within crystalline phases. Centrifuging under anaerobic conditions enabled more detailed information about a variety of arsenic coordination environments to be determined.
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Ai, L. Nguyen, A. Sato, D. Inoue, K. Sei, S. Soda, and M. Ike. "Enrichment of arsenite oxidizing bacteria under autotrophic conditions and the isolation and characterization of facultative chemolithoautotrophic arsenite oxidizing bacteria for removal of arsenic from groundwater." Water Supply 12, no. 5 (August 1, 2012): 707–14. http://dx.doi.org/10.2166/ws.2012.045.

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Arsenic contamination in groundwater has caused severe health problems throughout the world. Developing cost-effective processes for arsenic removal is an emerging issue. Because As(III) is predominant in groundwater and is more difficult to remove than As(V) is, oxidation of As(III) to As(V) is necessary to improve overall arsenic removal. This study was undertaken to enrich arsenite oxidizing bacteria under autotrophic conditions and to isolate and characterize facultative chemolithoautotrophic arsenite oxidizing bacteria (CAOs) that can oxidize As(III) effectively to As(V). An enrichment culture which adapted wide As(III) concentrations and completely oxidized 12 mM As(III) within 4 days under autotrophic conditions was established and maintained. Among 10 isolated strains, 6 strains, B1, B2, C, D, E1 and E2 belonging to β-Proteobacteria, were facultative CAOs and contained aoxB genes encoding the arsenite oxidase large subunit. Furthermore, they displayed various As(III) oxidation capabilities: B1, B2, E1 and E2 efficiently oxidized 1–10 mM As(III). The others showed efficient oxidation at 1–5 mM As(III), suggesting the coexistence of facultative CAOs with various As(III) oxidation capabilities in the enrichment. These results suggest that constructed enrichment and strains B1, B2, E1 and E2 can be useful for the bioremediation of arsenic-contaminated groundwater.
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YAMAZAKI, H., K. ISHII, Y. TAKAHASHI, S. MATSUYAMA, Y. KIKUCHI, Ts AMARTAIVAN, T. YAMAGUCHI, et al. "IDENTIFICATION OF OXIDATION STATES OF TRACE-LEVEL ARSENIC IN ENVIRONMENTAL WATER SAMPLES USING PIXE." International Journal of PIXE 15, no. 03n04 (January 2005): 241–47. http://dx.doi.org/10.1142/s012908350500057x.

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An enhanced sample preparation method for PIXE analysis is described allowing to separate and concentrate arsenic ions of different oxidation states in water samples. Arsenate ions are separated from arsenite ions by co-precipitating into 10 ppm indium hydroxide colloids that are generated at pH 4.0 in a 25 ml solution containing 1 ppm phosphate ions and 25 ppm sulfate ions. Arsenite ions are oxidized to the pentavalent state with permanganate ions and adsorbed by indium hydroxide colloids generated afterwards in solution. The standard procedure for collecting the colloids adsorbing arsenic ions on Nuclepore filter of 0.2 μm pores is based on an investigation of the pH-dependence of the recovery of dissolved arsenic ions and the obtained standard calibration curve covers the concentration range from 1 to 100 ppb for arsenic ions. The prepared targets were examined for 5 to 10 minutes by 3 MeV proton beam (0.7-4 nA beam currents). The lower detection limit of arsenic in a 25 ml aquatic sample is 0.3 ppb for the arsenic-precipitated targets based on the 3σ error of background counts integrated over the FWHM of arsenic peak in the PIXE spectrum. This sample preparation technique was then applied to analyze concentrations and oxidation states of arsenic in a river basin where hot springs are located upstream being possible sources for releasing arsenic in the river.
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Menezes, Regina A., Catarina Amaral, Liliana Batista-Nascimento, Claudia Santos, Ricardo Boavida Ferreira, Fréderic Devaux, Elis C. A. Eleutherio, and Claudina Rodrigues-Pousada. "Contribution of Yap1 towards Saccharomyces cerevisiae adaptation to arsenic-mediated oxidative stress." Biochemical Journal 414, no. 2 (August 12, 2008): 301–11. http://dx.doi.org/10.1042/bj20071537.

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In the budding yeast Saccharomyces cerevisiae, arsenic detoxification involves the activation of Yap8, a member of the Yap (yeast AP-1-like) family of transcription factors, which in turn regulates ACR2 and ACR3, genes encoding an arsenate reductase and a plasma-membrane arsenite-efflux protein respectively. In addition, Yap1 is involved in the arsenic adaptation process through regulation of the expression of the vacuolar pump encoded by YCF1 (yeast cadmium factor 1 gene) and also contributing to the regulation of ACR genes. Here we show that Yap1 is also involved in the removal of ROS (reactive oxygen species) generated by arsenic compounds. Data on lipid peroxidation and intracellular oxidation indicate that deletion of YAP1 and YAP8 triggers cellular oxidation mediated by inorganic arsenic. In spite of the increased amounts of As(III) absorbed by the yap8 mutant, the enhanced transcriptional activation of the antioxidant genes such as GSH1 (γ- glutamylcysteine synthetase gene), SOD1 (superoxide dismutase 1 gene) and TRX2 (thioredoxin 2 gene) may prevent protein oxidation. In contrast, the yap1 mutant exhibits high contents of protein carbonyl groups and the GSSG/GSH ratio is severely disturbed on exposure to arsenic compounds in these cells. These results point to an additional level of Yap1 contribution to arsenic stress responses by preventing oxidative damage in cells exposed to these compounds. Transcriptional profiling revealed that genes of the functional categories related to sulphur and methionine metabolism and to the maintenance of cell redox homoeostasis are activated to mediate adaptation of the wild-type strain to 2 mM arsenate treatment.
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Zargar, Kamrun, Shelley Hoeft, Ronald Oremland, and Chad W. Saltikov. "Identification of a Novel Arsenite Oxidase Gene, arxA, in the Haloalkaliphilic, Arsenite-Oxidizing Bacterium Alkalilimnicola ehrlichii Strain MLHE-1." Journal of Bacteriology 192, no. 14 (May 7, 2010): 3755–62. http://dx.doi.org/10.1128/jb.00244-10.

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ABSTRACT Although arsenic is highly toxic to most organisms, certain prokaryotes are known to grow on and respire toxic metalloids of arsenic (i.e., arsenate and arsenite). Two enzymes are known to be required for this arsenic-based metabolism: (i) the arsenate respiratory reductase (ArrA) and (ii) arsenite oxidase (AoxB). Both catalytic enzymes contain molybdopterin cofactors and form distinct phylogenetic clades (ArrA and AoxB) within the dimethyl sulfoxide (DMSO) reductase family of enzymes. Here we report on the genetic identification of a “new” type of arsenite oxidase that fills a phylogenetic gap between the ArrA and AoxB clades of arsenic metabolic enzymes. This “new” arsenite oxidase is referred to as ArxA and was identified in the genome sequence of the Mono Lake isolate Alkalilimnicola ehrlichii MLHE-1, a chemolithoautotroph that can couple arsenite oxidation to nitrate reduction. A genetic system was developed for MLHE-1 and used to show that arxA (gene locus ID mlg_0216) was required for chemoautotrophic arsenite oxidation. Transcription analysis also showed that mlg_0216 was only expressed under anaerobic conditions in the presence of arsenite. The mlg_0216 gene is referred to as arxA because of its greater homology to arrA relative to aoxB and previous reports that implicated Mlg_0216 (ArxA) of MLHE-1 in reversible arsenite oxidation and arsenate reduction in vitro. Our results and past observations support the position that ArxA is a distinct clade within the DMSO reductase family of proteins. These results raise further questions about the evolutionary relationships between arsenite oxidases (AoxB) and arsenate respiratory reductases (ArrA).
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Ike, M., T. Miyazaki, N. Yamamoto, K. Sei, and S. Soda. "Removal of arsenic from groundwater by arsenite-oxidizing bacteria." Water Science and Technology 58, no. 5 (September 1, 2008): 1095–100. http://dx.doi.org/10.2166/wst.2008.462.

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The presence of arsenic in groundwater has been of great public concern because of its high toxicity. For purification of arsenic-contaminated groundwater, bacterial oxidation of arsenite, As(III), with a chemical adsorption process was examined in this study. After As(III) oxidation to arsenate, As(V), arsenic is easily removable from contaminated groundwater because As(V) is more adsorptive to absorbents than As(III). By acclimation to As(III) of high concentrations, a mixed culture of heterotrophic bacteria with high As(III)-oxidizing activity was obtained from a soil sample that was free from contamination. With initial concentration up to 1,500 mg l−1 As(III), the mixed culture showed high As(III)-oxidizing activity at pH values of 7–10 and at temperatures of 25–35°C. The mixed culture contained several genera of heterotrophic As(III)-oxidizing and arsenic-tolerant bacteria: Haemophilus, Micrococcus, and Bacillus. Activated alumina was added to the basal salt medium containing 75 mg l−1 As(III) before and after bacterial oxidation. Arsenic removal by activated alumina was greatly enhanced by bacterial oxidation of As(III) to As(V). The isotherms of As(III) and As(V) onto activated alumina verified that bacterial As(III) oxidation is a helpful pretreatment process for the conventional adsorption process for arsenic removal.
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Dissertations / Theses on the topic "Arsenic – Oxidation"

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Sun, Wenjie. "Microbial Oxidation of Arsenite in Anoxic Environments: Impacts on Arsenic Mobility." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194899.

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AbstractArsenic (As) contamination of groundwater and surface water is a worldwide problem. Exposure to arsenic in drinking water is an important current public health issue. Arsenic is well known for its carcinogenic and teratogenic effects. The U.S. Environmental Protection Agency (USEPA) has recently enacted a stricter drinking water standard for arsenic that lowers the maximum contaminant level (MCL) from 50 to 10 ug l-1.Localized elevated As concentrations in groundwater or surface water have been attributed to the natural release of As from the weathering of As bearing minerals. Microbial reduction of arsenate (As(V)) to arsenite (As(III)) and ferric (hydr)oxides to Fe(II) is hypothesized to be the dominant mechanisms of As mobilization in subsurface environments. If oxidizing conditions can be restored, As can be immobilized by the formation of As(V) and ferric (hydr)oxides. As(V) is more strongly adsorbed than As(III) at circumneutral conditions by common non-iron metal oxides in sediments such as those of aluminum. Ferric (hydr)oxides have strong affinity for both As(III) and As(V) in circumneutral environments. Oxygen can be introduced into the anaerobic zone by injection of gaseous O2 to promote oxidation reactions of As(III) and Fe(II), but O2 is poorly soluble and chemically reactive and thus difficult to distribute in the subsurface. Nitrate or chlorate can be considered as alternative oxidants with advantages over elemental oxygen due to their high aqueous solubility and lower chemical reactivity which together enable them to be better dispersed in the saturated subsurface.The objective of this study is to evaluate the importance of anoxic oxidation of As(III) to As(V) by anaerobic microorganisms such as chemolithotrophic denitrifying bacteria and chlorate respiring bacteria in the biogeochemical cycle of arsenic. This study also investigated a arsenic potential bioremediation strategy based on injecting nitrate or chlorate into contaminated groundwater and surface water under anaerobic conditions.In this study, denitrification or chlorate reduction linked to the oxidation of As(III) to As(V) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. The biological oxidation of As(III) utilizing nitrate or chlorate as sole electron acceptor was feasible and stable over prolonged periods of operation in continuous-flow anaerobic bioreactors. Evidence for the complete denitrification was demonstrated by direct measurement of N2 formation dependent on As(III) addition. Also complete chlorate reduction to chloride was attributable to the oxidation of As(III). A 16S rRNA gene clone library characterization of enrichment cultures indicated that the predominant phylotypes responsible for As(III) oxidation linked to denitrification were from the genus Azoarcus and the family Comamonadaceae. A bioremediation strategy was explored that is based on injecting nitrate to support the microbial oxidation of Fe(II) and As(III) in the subsurface as a means to immobilize arsenic. Two models were utilized to illustrate the mechanisms of As removal.1) Sediment columns packed with activated alumina were utilized to demonstrate the role of nitrate in supporting microbial As(III) oxidation and arsenic mobility in anoxic sediments containing mostly non-iron oxides;2) Sand-packed columns were used to simulate natural anaerobic groundwater and sediment systems with co-occurring As(III) and Fe(II) in the presence or absence of nitrate. Microbial oxidation by denitrifying microorganisms lead to the formation of ferric (hydroxides) which adsorbed As(V) formed from As(III)-oxidation.The studies presented here demonstrate that anoxic microbial oxidation of As(III) and Fe(II) linked to denitrification significantly enhance the immobilization of As in the anaerobic subsurface environments.
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Simeonova, Diliana Dancheva. "Arsenic oxidation of Cenibacterium arsenoxidans : Potential application in bioremediation of arsenic contaminated water." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/SIMEONOVA_Diliana_Dancheva_2004.pdf.

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Hersey, Michelle. "Oxidation of Arsenite Via Chelator-mediated Fenton Systems." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/HerseyMX2006.pdf.

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Radabaugh, Timothy. "Oxidation and reduction of inorganic arsenic in mammalian systems." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280379.

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Arsenic is a toxic metalloid and is ubiquitous in our environment. In ancient cultures it was valued as a poison and today is becoming an increasing public health problem. Chronic arsenic exposure has a broad range of toxic effects including cancer. Currently millions of people are exposed to higher levels of arsenic in their food and drinking water than is considered safe by the World Health Organization. Although arsenic metabolism is not completely understood, it is known that inorganic arsenate is reduced to arsenite which can then be methylated and excreted in the urine. It is also known that some arsenic is retained in the body, presumably by binding to cellular proteins. To better understand how arsenic is metabolized, our approach was to identify and characterize proteins that are involved in arsenic metabolism. Using biochemical approaches we demonstrated that arsenate reductase activity from human liver was purine nucleoside phosphorylase (PNP). We were able to demonstrate that calf spleen PNP has arsenate reductase activity in vitro in the presence of inosine and dihydrolipoic acid, and that the reaction exhibits Michaelis-Menten kinetics. This identifies an enzymatic route for arsenate reduction. We also demonstrate that ferritin, an iron storage protein containing phosphate, can bind arsenic both in vitro and in vivo. In addition, we demonstrate that ferritin can oxidize arsenite to arsenate, and then interact with arsenate as it does with phosphate. We also establish that arsenate can inhibit ferritin's ability to store iron in vitro. Our results combined with data reported by others, suggest that DNA damage and enzyme inactivation associated with arsenic challenge may occur via reactive oxygen species generated by arsenic-iron redox reactions in ferritin, and that iron may augment arsenic toxicity. The interaction between ferritin and arsenate has two important implications. First, it suggests that iron exposure may be an important parameter to examine in epidemiological studies of arsenic sensitivity. Second, it suggests that iron chelation therapy might be beneficial in conjunction with arsenic chelation therapy for patients suffering from acute arsenic poisoning.
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Walker, Forest P. "Kinetics of Arsenopyrite Oxidative Dissolution by Oxygen." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9881.

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The objective of this study is to use a mixed flow reactor system to determine the dissolution rate and infer potential mechanisms of arsenopyrite (FeAsS) oxidation by dissolved oxygen at 25°C and circumneutral pH. Release rates for iron, arsenic and sulfur are calculated for a variety of initial dissolved oxygen (DO) concentrations. Results indicate that the rate of arsenopyrite oxidation, represented by the rate law r = A(6.76 x 10-11) where the rate, r, is in mol/s and surface area, A, is in m2, is not significantly dependent on DO concentration. Arsenic and sulfur are released in a 1:1 molar ratio while iron is released more slowly due to precipitation of iron oxyhydroxides. Our results suggest that the rate determining step in arsenopyrite oxidation is determined by the attachment of oxygen at the anodic site in the mineral, and not the transfer of electrons from the cathodic site to oxygen, as is suggested for other sulfide minerals such as pyrite. Previous work on FeAsS oxidation has been limited to low pH conditions with ferric iron as the oxidant. However, not all arsenopyrite weathering occurs exclusively in acidic environments. For example, at an abandoned arsenopyrite mine in Virginia, the pH of ground and surface waters is consistently between 4 and 7. Results of this study provide important insight to arsenic mobilization processes and rates, at field-relevant conditions, consequently aiding in the effort to understand arsenic release and retention in the environment.
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Moore, Kenneth. "Treatment of Arsenic Contaminated Groundwater using Oxidation and Membrane Filtration." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/866.

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Arsenic is a known carcinogen, causing cancers of the skin, lungs, bladder and kidney. Current research suggests that drinking water is the most common pathway for long-term low dose exposure. Arsenic contaminated drinking water has caused serious health problems in many countries including: India, Bangladesh, Argentina, Chile, Taiwan, the United States and Canada. Nanofiltration (NF) is a promising technology for arsenic removal since it requires less energy than traditional reverse osmosis membranes. Several studies have shown that nanofiltration is capable of removing the oxidized form of arsenic [As(V)] while the reduced form of arsenic [As(III)] is poorly removed. To exploit this difference it has been suggested that a pretreatment step which oxidizes the As(III) to As(V) would improve the performance of membrane filtration, but this has never been demonstrated. The research had three objectives: The first was to investigate the ability of NF membranes to treat arsenic contaminated groundwater and evaluate the influence of the membrane type and operating conditions. Secondly, the effectiveness of a solid phase oxidizing media (MnO2) to oxidize arsenite to arsenate was investigated. Lastly, the MnO2 was combined with NF membrane filtration to determine the benefit, if any, of oxidizing the arsenic prior to membrane filtration. A pilot membrane system was installed to treat a naturally contaminated groundwater in Virden, Manitoba, Canada. The groundwater in Virden contains between 38 and 44 µg/L of arsenic, primarily made up of As(III), with little particulate arsenic. In the first experiment three Filmtec® membranes were investigated: NF270, NF90 and XLE. Under all conditions tested the NF90 and NF270 membranes provided insufficient treatment of Virden's groundwater to meet Canada's recommended Interim Maximum Acceptable Concentration (IMAC) of 25 µg/L. The XLE membrane provided better arsenic removal and under the conditions of 25 Lmh flux and 70% recovery produced treated water with a total arsenic concentration of 21 µg/L. The XLE membrane is therefore able to sufficiently treat Virden's ground water. However treatment with the XLE membrane alone is insufficient to meet the USEPA's regulation of 10 µg/L or Canada's proposed Maximum Allowable Concentration (MAC) of 5 µg/L. The effects of recovery and flux on total arsenic passage are consistent with accepted membrane theory. Increasing the flux increases the flow of pure water through the membrane; decreasing the overall passage of arsenic. Increasing the recovery increases the bulk concentration of arsenic, which leads to higher arsenic passage. The second experiment investigated the arsenic oxidation capabilities of manganese dioxide (MnO2) and the rate at which the oxidation occurs. The feed water contained primarily As(III), however, when filtered by MnO2 at an Empty Bed Contact Time (EBCT) of only 1 minute, the dominant form of arsenic was the oxidized form [As(V)]. At an EBCT of 2 minutes the oxidation was nearly complete with the majority of the arsenic in the As(V) form. Little arsenic was removed by the MnO2 filter. The third and final experiment investigated the benefit, if any, to combining the membrane filtration and MnO2 treatment investigated in the first and second experiments. The effect of MnO2 pretreatment was dramatic. In Experiment I, the NF270 and NF90 membranes were unable to remove any arsenic while the XLE removed, at best, approximately 50% of the arsenic. Once pretreated with MnO2 the passage of arsenic through all of the membranes dropped to less than 4 µg/L, corresponding to approximately 91% to 98% removal. The dramatic improvement in arsenic removal can be attributed to charge. All three membranes are negatively charged. Through a charge exclusion effect the rejection of negatively charged ions is enhanced. During the first experiment, As(III) (which is neutrally charged) was the dominant form of arsenic, and was uninfluenced by the negative charge of the membrane. Once oxidized to As(V), the arsenic had a charge of -2, and was electrostatically repelled by the membrane. This greatly improved the arsenic rejection characteristics of the membrane. Nanofiltration alone is not a suitable technology to remove arsenic contaminated waters where As(III) is the dominant species. When combined with MnO2 pre-oxidation, the arsenic rejection performance of nanofiltration is dramatically improved.
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Botfield, Andrew Civil &amp Environmental Engineering Faculty of Engineering UNSW. "Kinetic modelling studies of As(III) oxidation in dark pH 3 and 8 Fenton - mediated and pH 8 Cu(II) - H2O2 systems." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2006. http://handle.unsw.edu.au/1959.4/31969.

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In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).
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Masur, Deanne Christine. "Microbial and geochemical processes controlling the oxidation and reduction of arsenic in soils." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/masur/MasurD0507.pdf.

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Edvardsson, Matilda. "Geochemical tracing of Arsenic sources in groundwater at the remediated Storliden mine, Skellefte district." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82694.

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The Swedish mining industry has changed from the historical situation with several smaller mines to the present situation with a few, bigger mines. This results in presence of abandoned mines around Sweden. Remediation of mines is regulated by legislation and the present demands are considerably higher than it was some decades ago.  The Storliden mine was a Zink- and Coppermine active between 2001-2008. Storliden is located in Malå municipality, Västerbotten county, and is included in the Skellefte district, known for its sulfide mineralizations.  The ore was broken underground with a technique called cut and fill mining. It was estimated that the ore was to be consumed in 2007, but due to rising ore prices, the mine was operated until 2008. Remediation was done through backfilling the mine with waste rock from Storliden and Boliden’s mines Renström, Kedträsk, and Kankberg. Also, tailings, concrete, and sludge from the sedimentation basins were backfilled. Today, the mine is filled with water.  High Arsenic concentrations in water is a serious health issue in parts of the world. Bangladesh is perhaps the most common example where Arsenic in groundwater has caused health problems for millions of people. In Sweden, the Skellefte field is known for its elevated Arsenic concentrations in the bedrock, related to sulfide mineralizations. Studies confirm a correlation between Arsenic-bearing bedrock and elevated concentrations in water.  This thesis work has been conducted together with the consultant company Golder Associates (Golder) in Luleå. Golder has performed environmental investigations in the Storliden area during the period 2018-2020. Installation and sampling of groundwater wells were included in this investigation. High concentrations of Arsenic was found in some of the groundwater wells. This thesis aims to review potential sources of Arsenic and their potential significance. The purposes are to be fulfilled by evaluating and interpreting the results from the sampling, Piper diagrams, ratios, and modeling in the program PHREEQC.  The results indicate that the presence of Arsenopyrite in the bedrock is the most likely source of the elevated concentrations of Arsenic in deep groundwater. Oxidation of Arsenopyrite is likely caused by mainly dissolved oxygen in groundwater. Further, the water quality differs from different depths, indicating that deep groundwater and water flow from the mine via the ramp do not have any immediate connection. It is likely that remains of tailings on the industrial area cause low pH and leaching of metals locally.  High concentrations of Arsenic can occur very locally, highlighting the importance of conducting sampling of groundwater used as drinking water in areas where sulfide mineralizations are confirmed or suspected. Further, a relation between the time that water is in contact with the bedrock/mineralization and the concentration of Arsenic is stated. Higher concentration HCO3- tends to correlate with elevated Arsenic concentration.
Sveriges gruvindustri har förändrats i snabb takt, från ett flertal mindre gruvor till dagens läge med ett mindre antal större gruvor. Detta resulterar i förekomst av nedlagda gruvor runt om i Sverige. Efterbehandling av gruvor regleras genom lagstiftning, och kraven idag är betydligt högre än för bara något decennium sedan.   Storlidengruvan var en zink- och koppargruva verksam mellan 2001–2008. Storliden ligger i Malå kommun och området ingår i Skelleftefältet, känt för sina sulfidmineraliseringar. Malmen bröts i en underjordsgruva med så kallad igensättningsbrytning, dvs. tomrum har succesivt fyllts ut med material under driften. Malmen beräknades vara förbrukad 2007, men när malmpriset ökade kunde gruvan leva vidare till 2008. Efterbehandlingen innebar att fylla igen gruvan med gråberg från Storliden men också gråberg från Bolidens gruvor Renström, Kedträsk och Kankberg. Dessutom användes anrikningssand, cement och slam från sedimentationsbassängerna för att fylla igen gruvan. Länshållning av gruvan upphörde och idag är gruvan vattenfylld. Höga arsenikhalter i vatten är ett hälsoproblem i delar av världen. Det kanske vanligaste exemplet är Bangladesh, där arsenik i grundvatten har orsakat hälsoproblem för miljontals människor. I Sverige är Skelleftefältet utmärkande för den höga arsenikhalten i berggrunden. Naturlig arsenikhalt i borrade brunnar har undersökts i flera studier som visar ett samband mellan arsenikhaltig berggrund och förhöjda halter i vatten.  Examensarbetet har utförts tillsammans med konsultföretaget Golder Associates i Luleå. Golder har fått i uppdrag att utföra miljötekniska undersökningar i Storlidenområdet, bland annat ingick installation och provtagning av grundvattenrör. Denna provtagning skedde under perioden 2018–2020. I några av grundvattenrören påträffades förhöjda halter av arsenik. Detta examensarbete syftar till att utreda förekomsten av Arsenik i grundvattnet, undersöka vilka källor som kan vara orsaken till arsenikhalterna samt källornas förväntade betydelse. Detta har gjorts genom att utvärdera och tolka resultaten från provtagningarna samt användningen av Piper-diagram, geokemiska kvoter och geokemisk modellering i programmet PHREEQC. Resultaten indikerar att förekomst av arsenikkis som mineralisering i berggrunden är den mest troliga källan till de förhöjda halterna av arsenik i djupt grundvatten. Oxidationen av arsenikkis sker troligtvis främst av löst syre i grundvattnet. Vidare skiljer sig vattenkvalitén åt från olika djup och delar av området som provtagits, dvs. det verkar inte finnas någon omedelbar koppling mellan djupt grundvatten och vatten som kommer via rampen som leder till gruvan. Det är troligt att rester av anrikningssand på industriområdet orsakar lågt pH och metallutlakning lokalt.  Höga arsenikhalter kan förekomma lokalt, vilket understryker vikten av att utföra provtagning av grundvatten som används för dricksvatten i områden där misstänkt eller konstaterade sulfidmineraliseringar förekommer, eftersom arsenik annars kan vara en mycket skadlig ”diffus” förorening. Vidare konstateras också samband mellan den tid som vatten är i kontakt med mineralisering och arsenikhalt. Högre halt HCO3- tenderar att korrelera med förhöjd arsenikhalt
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Rodríguez-Freire, Lucía. "The Role of Microorganisms in the Biogeochemical Cycle of Arsenic in the Environment." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333167.

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Arsenic (As) is a highly toxic chemical that is widely distributed in groundwater around the world. As-bearing sulfide minerals (ASM) are known to contribute to high background concentrations of As in groundwater in regions where the geochemistry of the parent material is dominated by sulfide minerals. The fate of As in groundwater depends on the activity of microorganisms which can oxidize arsenite (Asᴵᴵᴵ), or reduce arsenate (Asᵛ). In oxidizing environments, Asᵛ is the predominant species, and the accumulation of As is limited by the sorption of As onto iron (Fe) oxides and hydroxides. Under reducing environments, Asᴵᴵᴵ is the predominant specie, and while the sorption strength of Asᴵᴵᴵ on the Fe-surface of Fe (oxy)hydroxides is weaker, the accumulation of As in water can be limited by the precipitation of As as part of an ASM. The main aim of this research is to study the impact of microbial activity on the mobilization and immobilization of As in the environment. The first objective of this research was to characterize the metabolic activity of three Asᴵᴵᴵ-oxidizing bacteria, Azoarcus sp. pb-1 strain EC1, Azoarcus sp. pb-1 strain EC3 and Diaphorobacter sp. pb-1 strain MC, isolated from a non-contaminated, pristine environment. These Asᴵᴵᴵ-oxidizing bacteria demonstrated a great metabolic flexibility to use oxygen and nitrate to oxidize Asᴵᴵᴵ as well as organic and inorganic substrates as alternative electron donors (e-donors) explains their presence in non-As-contaminated environments. The findings suggest that at least some Asᴵᴵᴵ-oxidizing bacteria are flexible with respect to electron-acceptors and e-donors and that they are potentially widespread in low As concentration environments. The second objective of this research was to investigate the stability of orpiment (As₂S₃) and arsenopyrite (FeAsS), at circumneutral pH and 30°C, under aerobic- and or anoxic conditions (nitrate amended as electron acceptor (e-acceptor)), in order to assess the feasibility of immobilizing As by formation of ASM as a long-term option for the bioremediation of As contamination. The percentage of As released from the minerals ranged from zero when FeAsS was biologically incubated to 87% for As₂S₃(s) under anoxic abiotic conditions. While the dissolution of ASM was greater in biological conditions, the presence of inoculum provided as sludge served as a sink for As, limiting the mobilization of As into aqueous phase. Thus, the mobilization of As from ASM can be controlled by altering the environmental conditions such as the redox conditions or by stimulating microbial activity. Further research investigated the formation of ASM catalyzed by biological reduction of Asᵛ and sulfate (SO₄²⁻). In particular, the third objective of this research was to study the effect of the pH on the removal of As due to the biological-mediated formation of ASM in an iron-poor system. A series of batch experiments were performed to study the reduction of SO₄²⁻ and Asᵛ by an anaerobic mixed culture in a range of pH conditions (6.1-7.2), using ethanol as the e-donor. A marked decrease of the total aqueous concentrations of As and S and the formation of a yellow precipitate was observed in the inoculated treatments amended with ethanol, but not in the non-inoculated controls, indicating that the As-removal was biologically mediated. The pH dramatically affected the extent and rate of As removal, as well as the stoichiometric composition of the precipitate. The precipitate was composed of a mixture of orpiment and realgar, and the proportion of orpiment in the sample increased with increasing pH. The results suggest that ASM formation is greatly enhanced at mildly acidic pH conditions. The fourth objective was to investigate the biomineralization of As through simultaneous Asᵛ and SO₄²⁻ reduction in a minimal iron environment for the As-contaminated groundwater bioremediation. A continuous bioreactor, inoculated with an anaerobic sludge was maintained at circumneutral pH (6.25-6.50) and fed with Asᵛ and SO₄²⁻, utilizing ethanol as an e-donor for over 250 d. A second bioreactor running under the same conditions but lacking SO₄²⁻ was operated as a control to study the fate of As removal. The reactor fed with both Asᵛ and SO₄²⁻ removed on the average 91.2% of the total soluble As, while less than 5% removal was observed in the control bioreactor without S. The biomineralization of As in the bioreactor was also evident from the formation of a yellow precipitate made of a mixture of As₂S₃ and AsS minerals. These results taken as a whole indicate that a bioremediation process relying on the addition of a simple, low-cost e-donor offers potential to promote the removal of As from groundwater by precipitation of ASM. The fifth objective was to evaluate the toxic impact that the exposure to soluble As or the formation of ASM could have on the anaerobic mixed culture used as inocula. The methanogenic community on the reactors was impacted by addition of As. The biogenic ASM inhibited the acetoclastic methanogens causing an accumulation of acetate. In the SO₄²⁻-free bioreactor, the methanogens were initially highly sensitive to Asᴵᴵᴵ (formed from Asᵛ reduction) but quickly adapted to its toxicity. Consequently, the formation of ASM would impact the methanogenic activity of an anaerobic biofilm, while the exposure to Asᴵᴵᴵ would not have a negative impact if the biofilm undergoes adaptation. The sixth and final objective was to study the stability of a biogenic ASM at two different pH values (6.5 and 7.5) and under different redox conditions. The long-term stability was evaluated in three different bioreactors that operated for 145 d: aerobic (R1), anoxic (nitrate as alternative e-acceptor (R2) and anaerobic (R3). The dissolution of ASM was greatly affected by the pH, and slightly by the presence and nature of the e-acceptor. The ASM was very stable at pH 6.5, however, the As mobilization rate was up to 7-fold higher at pH 7.5, likely due to the formation of thioarsenic species. The stability of ASM was also impacted by the e-acceptor present. The As mobilization rate was 77% higher under anaerobic conditions than under aerobic conditions, most likely due to the formation of secondary As-bearing minerals. Therefore, the stability of ASM depends on the conditions of the operation, and it can be controlled by altering the environmental conditions, such as the pH or the presence of the e-acceptor.
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Books on the topic "Arsenic – Oxidation"

1

Ghurye, Ganesh. Laboratory study on the oxidation of arsenic III to arsenic V. Cincinnati, OH: National Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 2001.

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Frank, Phyllis. Arsenic (III) oxidation and removal from drinking water. Cincinnati, OH: U.S. Environmental Protection Agency, Water Engineering Research Laboratory, 1986.

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Lowry, Jerry. Arsenite oxidation by solid phase media or a UV sulfite process. Denver, CO: AWWA Research Foundation and American Water Works Association, 2005.

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Lei, K. P. V. Silver-catalyzed oxidative leaching of an arsenical copper sulfide concentrate. Avondale, Md (4900 LaSalle Rd., Avondale 20782): U.S. Dept. of the Interior, Bureau of Mines, 1987.

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United States. Bureau of Mines. Silver-Catalyzed Oxidative Leaching of an Arsenical Copper Sulfide Concentrate. S.l: s.n, 1987.

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Naidu, Ravi, Euan Smith, Gary Owens, Prosun Bhattacharya, and Peter Nadebaum. Managing Arsenic in the Environment. CSIRO Publishing, 2006. http://dx.doi.org/10.1071/9780643093515.

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Arsenic is one of the most toxic and carcinogenic elements in the environment. This book brings together the current knowledge on arsenic contamination worldwide, reviewing the field, highlighting common themes and pointing to key areas needing future research. Contributions discuss methods for accurate identification and quantification of individual arsenic species in a range of environmental and biological matrices and give an overview of the environmental chemistry of arsenic. Next, chapters deal with the dynamics of arsenic in groundwater and aspects of arsenic in soils and plants, including plant uptake studies, effects on crop quality and yield, and the corresponding food chain and human health issues associated with these exposure pathways. These concerns are coupled with the challenge to develop efficient, cost effective risk management and remediation strategies: recent technological advances are described and assessed, including the use of adsorbants, photo-oxidation, bioremediation and electrokinetic remediation. The book concludes with eleven detailed regional perspectives of the extent and severity of arsenic contamination from around the world. It will be invaluable for arsenic researchers as well as environmental scientists and environmental chemists, toxicologists, medical scientists, and statutory authorities seeking an in-depth view of the issues surrounding this toxin.
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G, Carnahan T., ed. Silver-catalyzed oxidative leaching of an arsenical copper sulfide concentrate. Avondale, Md (4900 LaSalle Rd., Avondale 20782): U.S. Dept. of the Interior, Bureau of Mines, 1987.

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G, Carnahan T., ed. Silver-catalyzed oxidative leaching of an arsenical copper sulfide concentrate. Avondale, Md (4900 LaSalle Rd., Avondale 20782): U.S. Dept. of the Interior, Bureau of Mines, 1987.

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Book chapters on the topic "Arsenic – Oxidation"

1

Kuehnelt, D., W. Goessler, and K. J. Irgolic. "The oxidation of arsenite in aqueous solutions." In Arsenic, 45–54. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5864-0_4.

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Criscuoli, A., A. Galizia, and E. Drioli. "Arsenic Oxidation by Membrane Contactors." In Water Treatment Technologies for the Removal of High-Toxity Pollutants, 107–18. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3497-7_9.

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Keimowitz, A. R., H. J. Simpson, S. N. Chillrud, M. Stute, M. Tsang, S. Datta, and J. Ross. "Oxidation of Groundwater Arsenic and Iron." In ACS Symposium Series, 206–19. Washington, DC: American Chemical Society, 2005. http://dx.doi.org/10.1021/bk-2005-0915.ch015.

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Ellis, Bobby D., and Charles L. B. Macdonald. "Cationic Low Oxidation State Phosphorus and Arsenic Compounds." In ACS Symposium Series, 108–21. Washington, DC: American Chemical Society, 2005. http://dx.doi.org/10.1021/bk-2005-0917.ch008.

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Manning, Bruce A., Scott E. Fendorf, and Donald L. Suarez. "Arsenic(III) Complexation and Oxidation Reactions on Soil." In ACS Symposium Series, 57–69. Washington, DC: American Chemical Society, 2002. http://dx.doi.org/10.1021/bk-2003-0835.ch005.

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Pearce, Mark S., Mike Waldron, and James A. Jacobs. "Prevention of Arsenic Mobilization Related to Sulfide Oxidation in Aquifers." In Acid Mine Drainage, Rock Drainage, and Acid Sulfate Soils, 197–203. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118749197.ch17.

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Paktunc, Dogan, Yves Thibault, and Chris Weisener. "Sulfide Oxidation and Mobilization of Arsenic in the Ketza River Mine Tailings." In Proceedings of the 10th International Congress for Applied Mineralogy (ICAM), 503–11. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27682-8_60.

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Slyemi, Djamila, Jeanine Ratouchniak, and Violaine Bonnefoy. "Regulation of the Arsenic Oxidation Encoding Genes of a Moderately Acidophilic, Facultative Chemolithoautotrophic Thiomonas sp." In Advanced Materials Research, 427–30. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-452-9.427.

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Tabacova, S., E. S. Hunter, and L. Balabaeva. "Potential role of oxidative damage in developmental toxicity of arsenic." In Arsenic, 135–44. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5864-0_12.

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Zargari, Felor. "Arsenic and Oxidative Stress: An Overview." In Arsenic Toxicity: Challenges and Solutions, 27–63. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-6068-6_2.

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Conference papers on the topic "Arsenic – Oxidation"

1

Alsecz, A., J. Osa´n, J. Pa´lfalvi, I. Sajo´, Z. Ma´the´, R. Simon, Sz To¨ro¨k, and G. Falkenberg. "Study of the Oxidation State of Arsenic and Uranium in Individual Particles From Uranium Mine Tailings, Hungary." In The 11th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2007. http://dx.doi.org/10.1115/icem2007-7354.

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Uranium ore mining and milling have been terminated in the Mecsek Mountains (southwest Hungary) in 1997. Mine tailings ponds are located between two important water bases, which are resources of the drinking water of the city of Pe´cs and the neighbouring villages. The average U concentration of the tailings material is 71.73 μg/g, but it is inhomogeneous. Some microscopic particles contain orders of magnitude more U than the rest of the tailings material. Other potentially toxic elements are As and Pb of which chemical state is important to estimate mobility, because in mobile form they can risk the water basis and the public health. Individual U-rich particles were selected with solid state nuclear track detector (SSNTD) and after localisation the particles were investigated by synchrotron radiation based microanalytical techniques. The distribution of elements over the particles was studied by micro beam X-ray fluorescence (μ-XRF) and the oxidation state of uranium and arsenic was determined by micro X-ray absorption near edge structure (μ-XANES) spectroscopy. Some of the measured U-rich particles were chosen for studying the heterogeneity with μ-XRF tomography. Arsenic was present mainly in As(V) and uranium in U(VI) form in the original uranium ore particles, but in the mine tailings samples uranium was present mainly in the less mobile U(IV) form. Correlation was found between the oxidation state of As and U in the same analyzed particles. These results suggest that dissolution of uranium is not expected in short term period.
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TANABE, KIMIKO, KOICHIRO SHIOMORI, KAZUHIRO YABUUCHI, KAZUHIRO HAMABE, and HIROSHI YOKOTA. "ARSENIC REMOVAL BY OXIDATION OF IRON HYDROXIDE AND SETTLEMENT OF CO-PRECIPITATION INTO GRAVEL SPACES." In Proceedings of the 13th IAHRߝ;APD Congress. World Scientific Publishing Company, 2002. http://dx.doi.org/10.1142/9789812776969_0175.

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van Genuchten, Case M., and Arslan Ahmad. "IMPACT OF OXIDIZING AGENT ON GROUNDWATER ARSENIC TREATMENT BY AS(III), FE(II) AND MN(II) CO-OXIDATION." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-359557.

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Tillman, David A. "Petroleum Coke as a Supplementary Fuel for Cyclone Boilers: Characteristics and Test Results." In 2002 International Joint Power Generation Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/ijpgc2002-26157.

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Petroleum coke is periodically tested and used as a supplementary fuel for cyclone boilers. Its high heat content and low cost make it an attractive fuel for power generation. In cyclone boiler firing, it also has environmental advantages. While it is high in sulfur content, it can be used to reduce NOx emissions along with such trace metal emissions as mercury and arsenic. Successful firing of petroleum coke in cyclone boilers, however, requires considerable attention to fuel properties of the coal and the opportunity fuel including fuel structure and reactivity, and ash chemistries. This paper reviews selected properties of petroleum coke including traditional analyses plus structural characterization using 13Carbon Nuclear Magnetic Resonance (NMR), drop tube reactor (DTR) characterization for kinetics and volatility evaluation, and thermogravimetric analysis (TGA) for char oxidation kinetics. The paper then summarizes results of petroleum coke firing at the Paradise Fossil Plant of TVA, and Bailly Generating Station of Northern Indiana Public Service Company (NIPSCO). Results presented include impacts of cofiring on boiler efficiency, NOx emissions, and the fate of selected trace metals including arsenic, mercury, nickel, and vanadium. It documents the overall benefits and issues associated with cofiring petroleum coke with coal in cyclone boilers as a significant opportunity fuel.
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Bansal, Iqbal K. "Hydrophobic Silicon-Direct Bonding for Fabrication of RF Microwave Devices." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41161.

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Direct wafer bonding (DWB) is an operation of ultra-fine alignment, joining and thermal bonding of two silicon wafers. The first silicon wafer “handle” substrate is a Czochralski (&lt;CZ&gt;) substrate with N+ arsenic dopant with very low bulk resistivity, whereas second wafer “device” is a float-zone (&lt;FZ&gt;) having extremely high resistivity N-phosphorus dopant. Prior to the joining step, silicon wafers are chemically cleaned in order to minimize surface contamination. The wafer surface is “hydrophobic” which is achieved using an insitu oxide etching process. The surface quality is also characterized in terms of sub-micron light point defects (LPD’s) counts and haze concentration using a laser beam scanning system. After chemical clean, none of the LPD’s counts is greater than 1.0 μ size. The joining step is performed in a Class 100 or better environment by employing a commercial joiner. Then, thermal bonding operation is carried out by employing an extended stream oxidation cycle at elevated temperatures. Typical failure modes of DWB are misalignment errors and “voided” or “disbonded” regions. The area of “voided” regions for each bonded pair is determined by employing a scanning acoustic microscope. Detailed product throughtput and yield data are presented in this paper. A spreading resistivity profile (SRP) system is employed for accurate measurement of doping carrier concentration as a function of the depth. The superior uniformity for capacitance-voltage characteristics of a Si-Si bonded wafer versus an inverse epitaxial silicon wafer substrate is shown in terms of the device performance. The applications of silicon-direct wafer bonded substrates provide a quantum jump in the device electrical performance of PIN diodes.
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Li, Ping. "Different Regulating Strategies of Arsenite Oxidation by Thermus Tengchongensis from Hot Spring." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1507.

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"A Plant Model for Assessing Arsenic Phytotoxicity: Effect on Growth and Oxidative Stress Response Molecules." In 5th International Conference on Agriculture, Environment and Biological Sciences. International Academy of Arts, Science & Technology, 2016. http://dx.doi.org/10.17758/iaast.a0416001.

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Li, Xiaomin, Shuang Li, Jiangtao Qiao, and Fangbai Li. "Bacteria and Genes Associated with Arsenite Oxidation and Nitrate Reduction in a Paddy Soil." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1525.

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Brown, Erika T., Clement G. Yedjou, and Paul B. Tchounwou. "Abstract 4209: Genotoxic effects of arsenic trioxide-induced oxidative stress in human hepatocellular carcinoma (HepG2) cells." In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-4209.

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Walker, Alice M., Jacqueline J. Stevens, and Paul B. Tchounwou. "Abstract 4210: Oxidative stress, DNA damage, and apoptosis mediated by arsenic trioxide in lung carcinoma cells." In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-4210.

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