Feasibility study on the use of thiosulfate to remediate mercury-contaminated soil

The feasibility of using sodium thiosulfate to remediate the mercury-contaminated soil around a local chemical plant in northeastern China has been investigated. Effects of solid-to-reagent ratio and temperature on mercury extraction from soil samples with thiosulfate solutions were examined. BCR (European Community Bureau of Reference) analysis indicated that more than 90% of weak acid soluble and reducible mercury in the soil sample could be extracted by thiosulfate solution. Mercury extraction kinetics can be described by the two-step first-order reaction model in which the readily extractable fraction and the less extractable fraction of mercury were associated with their own rate constants. Mercury extraction with thiosulfate solutions could be slightly promoted when the contaminated soil was pre-oxidized with hydrogen peroxide. The results suggest that thiosulfate is a potentially effective complexing lixiviant in mercury-contaminated soil remediation.