Incorporation of trace metals Cu, Zn, and Cd into gypsum: Implication on their mobility and fate in natural and anthropogenic environments

Abstract The coexistence of calcium (Ca2+), sulfate (SO42−) with trace metal cations (M(II)) can possibly lead to M(II)-gypsum coprecipitation and solid solution formation. However, gypsum's role in the fixation of M(II) is still largely unknown. This study investigated the precipitation of Ca2+ and SO42− in the presence of M(II) (i.e., Cu2+, Zn2+, or Cd2+) and the incorporation of the metal cations into the gypsum structure at different environmental conditions. Trace metals in two natural gypsum samples (Yunnan and Neimeng, China) and one hydrometallurgical byproduct gypsum sample from a Cu refinery were also assessed. X-ray diffraction, scanning electron microscopy-energy dispersive X-ra…