Stabilization/Solidification of High Mercury Wastes with Reactivated Carbon

Abstract

This paper presents the study results for a novel stabilization/solidification (S/S) process for high mercury wastes (Hg >260 ppm). In this study, a low-cost powder reactivated carbon (PAC) was used to stabilize mercury in contaminated soils. Two types of contaminated soils were used: (1) a mercury-doped pure sand, used as a waste surrogate so as to minimize competitive adsorption by substances in real soils; and (2) a mercury-contaminated soil with about 2,300 ppm Hg from a mercury cell chlor-alkali plant. To improve the mercury adsorption capacity, PAC was impregnated with sulfides. It was found that sulfurized PAC significantly lowered mercury mobility. After stabilization, wastes were subjected to cement solidification. Results of toxicity characteristic leaching procedure and constant pH leaching tests showed that the S/S process successfully immobilized mercury in the treatment matrix. Even under attack from high chloride concentration, little mercury was leached from the matrix. Optimal S/S treatment parameters and treatment process flows are discussed for possible commercial implementation of the process. Based on the experimental data, it can be concluded that the S/S process by reactivated carbon and cement is a robust and effective technology for immobilization treatment of high mercury wastes.