title: Incorporation of arsenic into gypsum: Relevant to arsenic removal and immobilization process in hydrometallurgical industry.
abstract: Gypsum precipitates as a major secondary mineral during the iron-arsenate coprecipitation process for the removal of arsenic from hydrometallurgical effluents. However, its role in the fixation of arsenic is still unknown. This work investigated the incorporation of arsenic into gypsum quantitatively during the crystallization process at various pHs and the initial arsenic concentrations. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray absorption near edge spectroscopy (XANES) and scanning electron microscopy (SEM) were employed to characterize the coprecipitated solids. The results showed that arsenate was measurably removed from solution during gypsum crystallization and the removal increased with increasing pH. At lower pH where the system was undersaturated with respect to calcium arsenate, arsenate ions were incorporated into gypsum structure, whereas at higher pH, calcium arsenate was formed and constituted the major arsenate bearing species in the precipitated solids. The findings may have important implications for arsenic speciation and stability of the hydrometallurgical solid wastes.
authors.affiliation: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
authors.forename: Danni
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
authors.forename: Zidan
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: wangshaofeng@iae.ac.cn.
authors.forename: Shaofeng
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: yongfeng.jia@iae.ac.cn.
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Jia
authors.affiliation: Department of Mining and Materials Engineering, McGill University, Montreal, QC H3A 2B2, Canada.
authors.forename: George P
authors.initials: GP
authors.lastname: Demopoulos
keywords: Arsenic; Gypsum; Incorporation