Enhanced oxidation of arsenite to arsenate using tunable K+ concentration in the OMS-2 tunnel. (July 2018)

• Record Type: Journal Article
• Authors: Hou, Jingtao; Sha, Zhenjie; Hartley, William; Tan, Wenfeng; Wang, Mingxia; Xiong, Juan; Li, Yuanzhi; Ke, Yujie; Long, Yi; Xue, Shengguo
• Is Part Of: Environmental pollution. Volume 238(2018)
• Page Start: 524
• Page End: 531
• Publication Date: 2018-07
• Subjects: OMS-2 -- K+ doping -- Arsenite oxidation -- Arsenate -- Competitive adsorption; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.03.047
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Cryptomelane-type octahedral molecular sieve manganese oxide (OMS-2) possesses high redox potential and has attracted much interest in its application for oxidation arsenite (As(III)) species of arsenic to arsenate (As(V)) to decrease arsenic toxicity and promote total arsenic removal. However, coexisting ions such as As(V) and phosphate are ubiquitous and readily bond to manganese oxide surface, consequently passivating surface active sites of manganese oxide and reducing As(III) oxidation. In this study, we present a novel strategy to significantly promote As(III) oxidation activity of OMS-2 by tuning K + concentration in the tunnel. Batch experimental results reveal that increasing K + concentration in the tunnel of OMS-2 not only considerably improved As(III) oxidation kinetics rate from 0.027 to 0.102 min −1, but also reduced adverse effect of competitive ion on As(III) oxidation. The origin of K + concentration effect on As(III) oxidation was investigated through As(V) and phosphate adsorption kinetics, detection of Mn 2+ release in solution, surface charge characteristics, and density functional theory (DFT) calculations. Experimental results and theoretical calculations confirm that by increasing K + concentration in the OMS-2 tunnel not only does it improve arsenic adsorption on K + doped OMS-2, but also accelerates two electrons transfers from As(III) to each bonded Mn atom on OMS-2 surface, thus considerably improving As(III) oxidation kinetics rate, which is responsible for counteracting the adverse adsorption effects by coexisting ions. Graphical abstract: Image 1 Highlights: As(III) oxidation performance of OMS-2 with tunable K + concentration in the tunnel was investigated. Increasing K + concentration in the tunnel of OMS-2 considerably improved As(III) oxidation activity. Origin of K + concentration levels effect on As(III) oxidation was experimentally and theoretically investigated. Presence of high K + concentration in the tunnel promotes highly efficient contact between OMS-2 and arsenic species. Presence of high K + concentration in the tunnel accelerates charge transfer from As to Mn atom in OMS-2. Abstract : We present a novel strategy to promote As(III) oxidation kinetics rate and counteract the adverse effects of coexisting ions on As(III) oxidation by tuning K + content in the OMS-2 tunnel.