As(V) and As(III) reactions on pristine pyrite and on surface-oxidized pyrite

Sun, Fenglong; Dempsey, Brian A.; Osseo‐Asare, K.

doi:10.1016/j.jcis.2012.08.019

Cited by 47 publications

(23 citation statements)

References 33 publications

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“…The theoretical neoformation of As-sulfides agrees with the SEM-EDS observations that also exclude any detectable incorporation of As into Fe-sulfide or adsorption onto their surfaces (Sun et al, 2012). The microscopic observations also show that As-sulfides occur in micro areas rich in organic remains, in agreement with the requirement of very reducing conditions, as indicated by the modeling.…”

Section: Aquifer Conditions and Arsenic Precipitationsupporting

confidence: 85%

Effects of redox conditions on the control of arsenic mobility in shallow alluvial aquifers on the Venetian Plain (Italy)

Carraro

Fabbri

Giaretta

et al. 2015

Science of The Total Environment

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Section: Aquifer Conditions and Arsenic Precipitationsupporting

confidence: 85%

Effects of redox conditions on the control of arsenic mobility in shallow alluvial aquifers on the Venetian Plain (Italy)

Carraro

Fabbri

Giaretta

et al. 2015

Science of The Total Environment

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“…The free energy value of the reference electrode half-cell reaction is calculated using the relevant species involved in the redox reaction of the reference electrode system. There are experimentally determined absolute values available for these reference electrodes in different solvents; for example, the absolute values of the SHE in H 2 O, methanol, ethanol, acetonitrile, and dimethylsulfoxide (DMSO) are different, these absolute values were derived from thermodynamic parameters [6,7,26,27,35,37] (see Table 1). In addition, the absolute value of the Fc/Fc + reference electrode with respect to the SHE is also known.…”

Section: Direct Methodsmentioning

confidence: 99%

“…The penta-valent As is more toxic than the tri-valent As [6]. Surface mediated redox process of As(V) and As(III) on Fe-sulfide mineral surfaces, such as pyrite [7] and mackinawite [8], are unexplored and not well understood.…”

Section: Introductionmentioning

confidence: 99%

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Arumugam

Becker

2014

Minerals

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Abstract:Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict and determine redox potentials of electron transitions are discussed along with their respective pros and cons for the prediction of redox potentials. Subsequently, recommendations are made for certain necessary computational settings required for accurate calculation of redox potentials. This article reviews the importance of computational parameters, such as basis sets, density functional theory (DFT) functionals, and relativistic approaches and the role that physicochemical processes play on the shift of redox potentials, such as hydration or spin orbit coupling, and will aid in finding suitable combinations of approaches for different chemical and geochemical applications. Identifying cost-effective and credible computational approaches is essential to benchmark redox potential calculations against experiments. Once a good theoretical approach is found to model the chemistry and thermodynamics of the redox and electron transfer process, this knowledge can be incorporated into models of more complex reaction mechanisms that include diffusion in the solute, surface diffusion, and dehydration, to name a few. This knowledge is important to fully understand the nature of redox processes be it a geochemical process that dictates natural redox reactions or one that is being used for the optimization of a chemical process in industry. In addition, it will help identify materials that will be useful to design catalytic OPEN ACCESSMinerals 2014, 4 346 redox agents, to come up with materials to be used for batteries and photovoltaic processes, and to identify new and improved remediation strategies in environmental engineering, for example the reduction of actinides and their subsequent immobilization. Highly under-investigated is the role of redox-active semiconducting mineral surfaces as catalysts for promoting natural redox processes. Such knowledge is crucial to derive process-oriented mechanisms, kinetics, and rate laws for inorganic and organic redox processes in nature. In addition, molecular-level details still need to be explored and understood to plan for safer disposal of hazardous materials. In light of this, we include new research on the effect of iron-sulfide mineral surfaces, such as pyrite and mackinawite, on the redox chemistry of actinyl aqua complexes in aqueous solution.

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“…Zouboulis et al (1993) first proposed the use of pyrite fines as an adsorbents for the removal of arsenite [As (III)] and arsenate [As(V)] [3]. In the uptake of As(V) by pristine pyrite, As(V) is first reduced to As(III) and then is incorporated into the solid phase; however, on surface-oxidized pyrite, As(V) reduction rarely occurs [4]. The products formed on pyrite surfaces are complicated.…”

mentioning

confidence: 99%

Treatment of strongly acidic wastewater with high arsenic concentrations by ferrous sulfide (FeS): Inhibitive effects of S(0)-enriched surfaces

Liu

Yang

et al. 2016

Chemical Engineering Journal

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h i g h l i g h t sFeS shows higher removal efficiency towards As(III) than As(V). In acidic solution FeS dissolve to S(-II) for As(V) reduction and As 2 S 3 formation. S(-II) react with As(V) to form S(0)-rich surface on FeS and inhibit As removal. S(II)-rich surface inhibit FeS dissolution and arsenic removal. As(V) reduction to As(III) by dosing Na 2 S prior to FeS improve As(V) removal. The utilization of arsenopyrite (FeAsS), the As ore mineral, produces strongly acidic wastewater with extremely high arsenic (As) concentrations. This study investigates the feasibility of using ferrous sulfide (FeS) as a sulfide [S(-II)] source to treat strongly acidic wastewater with high concentrations of arsenite [As(III)] and arsenate [As(V)]. The removal of As(III) by FeS was nearly 30% higher than that of As(V), and higher acidity and elevated FeS doses benefited their removal. At extremely high acidity of above 7 mol/L as H 2 SO 4 , the consumption of S(-II) by H 2 SO 4 inhibited As removal. At lower acidity of below 2 mol/L as H 2 SO 4 , elevated FeS doses up to 4 times the theoretical dose could achieve good As removal. SEM/EDS and XPS analysis indicated the formation of As 2 S 3 precipitates, and sulfur [S(0)] also formed in the As(V)-removing system. The tiny and negatively-charged S(0) particles tend to coat the FeS surface. The S(0)-enriched surface acts as a barrier to inhibit S(-II) detachment and As(V) penetration and inhibits As(V) removal thereafter. The reduction of As(V) to As(III) by Na 2 S, prior to dosing with FeS, is preferred to achieve rapid and favorable As(V) removal. The low-cost FeS provides available Fe(II) and S(-II) for As removal, and is practically valuable to treat acidic high-As wastewater.

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As(V) and As(III) reactions on pristine pyrite and on surface-oxidized pyrite

Cited by 47 publications

References 33 publications

Effects of redox conditions on the control of arsenic mobility in shallow alluvial aquifers on the Venetian Plain (Italy)

Effects of redox conditions on the control of arsenic mobility in shallow alluvial aquifers on the Venetian Plain (Italy)

Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces

Treatment of strongly acidic wastewater with high arsenic concentrations by ferrous sulfide (FeS): Inhibitive effects of S(0)-enriched surfaces

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