Stabilization and Release Characteristics of Heavy Metals in Desulfurization Sludge from Coal-Fired Power Plants

Abstract

ABSTRACT The leaching risk of heavy metals from flue gas desulfurization (FGD) by-product sludge of coal-fired power plants is high, and there is an urgent need for effective treatment using solidification. In this paper, dithiocarbonates (DTC), 2,4,6-tri-mercapto-S-triazine trisodium salt (TMT-15) curing agent, fly ash and cement were used to cure the desulfurization sludge and study the environmental release characteristics of heavy metals before and after curing. The results show that all four curing agents had a good curing effect. The best chelating agent was DTC, and the best curing conditions were achieved at a liquid-to-solid ratio of 3:1 and a mass fraction of 8%. The leaching concentrations of As, Pb, Cd, Cr, Ni, Cu, Zn, and Hg were reduced by 87.95%, 100%, 85.29%, 86.17%, 70.11%, 95.06%, 90.28%, and 98.44%, respectively, after curing. In the environmental release characteristics test, the leaching concentrations of heavy metals in the cured sludge were lower than those of the original samples at different pH values and temperatures, indicating better stability. The mass fraction had the greatest effect on the leaching concentration of heavy metals, followed by the pH value and temperature.