Effective treatment of arsenic-bearing water by a layered double metal hydroxide: Iowaite. (February 2017)

• Record Type: Journal Article
• Authors: Guo, Qinghai; Cao, Yaowu; Zhuang, Yaqin; Yang, Yijun; Wang, Mindai; Wang, Yanxin
• Is Part Of: Applied geochemistry. Volume 77(2017:Feb.)
• Page Start: 206
• Page End: 212
• Publication Date: 2017-02
• Subjects: Arsenic -- LDHs -- Iowaite -- Anion exchange -- Dissolution-reprecipitation; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2016.04.008
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: Iowaite with designed Mg/Fe ratios of 2.5, 3.0, 3.5, 4.0 and 5.0 was synthesized for treating both arsenate- and arsenite-spiked waters in this study. The experimental results show that there is a positive correlation between the molar ratio of Fe to Mg of synthetic iowaite and its arsenic uptake capacity. The dearsenication mechanisms were investigated based on the XRD, SEM and EDX analyses of solid samples before and after reaction with arsenic-bearing solutions. When the initial solution concentration of arsenic is not higher than 7500 μg/L, anion exchange between arsenate or arsenite in solution and chloride in the interlayer regions of iowaite is the primary mechanism for arsenic removal. However, at a very high initial arsenic concentration in solution (750 mg/L), the dissolution of iowaite and subsequent formation of new minerals, such as scorodite and karibibite, are responsible for the substantial removal of arsenic from water. Iowaite is superior to other types of layered double metal hydroxides (LDHs) such as hydrotalcite and hydrocalumite in terms of water dearsenication, and therefore promising for treatment of arsenic-rich waters, either naturally occurring waters or industrial wastewaters. Highlights: Iowaites with designed Mg/Fe ratios were synthesized for treating As-bearing waters. Increase in the Fe/Mg ratio of iowaite enhances its As uptake capacity. Anion exchange is the primary mechanism for water dearsenication by iowaite Iowaite is an anion clay promising for treatment of As-contaminated waters.