Chemical immobilization of lead, cadmium, and arsenic in a smelter-contaminated soil using 2,4,6-trimercaptotriazine, trisodium salt, nonahydrate and ferric sulfate

Abstract

Chemical immobilization has been widely used for remediation of heavy metal-contaminated soils. The present study evaluated the feasibility of simultaneous immobilization of lead, cadmium, and arsenic in a smelter-contaminated soil. 2,4,6-Trimercaptotriazine, trisodium salt, nonahydrate (TMT) and ferric sulfate were used as amendments to reduce the bioavailability of heavy metals and to improve the stability of immobilization. The effects of TMT dosage, ferric sulfate dosage, percentage of the field capacity, soil pH, and reaction time on immobilization were investigated. TMT is effective for immobilization of Pb and Cd in soils. The immobilization efficiencies of Pb, Cd, and As increase by 55% via addition of ferric sulfate. The optimal conditions for immobilization of Pb, Cd, and As occurred at a TMT dosage of 0.02 to 0.06 L kg−1, a ferric sulfate dosage of 48.0 to 80.0 g kg−1, a percentage of the field capacity of 60 to 80%, and a soil pH of 5.7 to 6.5. The extractable concentrations of Pb, Cd, and As in the immobilized soils met the environmental quality standard for soils in China (GB 15618-1995). The immobilization using TMT and ferric sulfate was high in efficiency and reliable in stability.