Decomposition of Insoluble Cyanide in Contaminated Soil by Base-Activated Sodium Persulfate

This study examines the use of base-activated sodium persulfate as a means of treating two types of soil contaminated with ferric and cupric cyanide complexes. The proposed treatment uses sodium persulfate and sodium hydroxide to convert insoluble cyanides into soluble form. The soils used in this study had high and low total cyanide contents of 1000 and 50 mg/kg, respectively, and free cyanide contents of 360 and 1.7 mg/kg, respectively. When sodium hydroxide was added, the concentrations of cyanides solubilized from soil were 5-10 times higher than those of samples not treated with sodium hydroxide. When 5% sodium persulfate and 1.5% sodium hydroxide were used, the proposed treatment decreased the total cyanide content in contaminated soil to less than 5 mg/kg and the cyanide content eluted from soil contaminated with ferric cyanide complexes to less than 1 mg/L, respectively. These values are below the values stipulated by environmental standards and the emission standards in Japan. Therefore, base-activated sodium persulfate treatment is considered effective for the removal of persistent cyanide from soil.