Occurrence form and environmental effect of heavy metal in flue gas desulfurization gypsum from Shanxi Province, China

Desulfurization gypsum, a byproduct of flue gas desulfurization in thermal power plants, poses potential environmental risks due to its heavy metal content. Therefore, a systematic analysis of the physicochemical properties of desulfurization gypsum is essential, with a specific focus on heavy metal content, occurrence form, and leaching characteristics. The results indicate that desulfurization gypsum is a powdery particle with high water content, primarily composed of CaSO₄·2H₂O and CaSO₄·0.5H₂O. The heavy metal content in desulfurization gypsum from Shanxi province consistently follows the order of Pb > Zn > As > Cr > Mn > Ba > Cu > Ni > Cd; and Cu, Zn, Ni, Cr, Mn, and Ba are predominantly present in an effective form, which increases their potential for environmental migration. Notably, the concentrations of heavy metals in the leachate obtained through the three standard leaching methods do not exceed regulatory standards. During the column leaching process, heavy metals are released into the leachate at varying rates. The dynamic leaching characteristics of each heavy metal are influenced by their contents and their chemical speciation. Particular attention should be given to the dynamic migration of Ni and Pb from desulfurization gypsum during its storage, disposal, and resource utilization.