In this study, the efficiency of oxidants (Ca(ClO)2, H2O2 and ClO2) for cyanide removal from soils was investigated. The results indicated that the addition of bleaching powder (containing Ca(ClO)2 as oxidant) may cause abrupt changes of pH values and physico-chemical characteristics of the soil. The oxidation efficiency of hydrogen peroxide was the lowest compared with the other oxidants. The addition of ClO2did not cause abrupt changes of pH values of the soil, and had the highest oxidation efficiency among the three oxidants. Thus, a low concentration of ClO2 was chosen as the most suitable oxidant, and the effects of reaction time, ClO2 dosage and temperature on cyanide removal efficiencies were further studied. The results showed that the removal rate of cyanide increased with the reaction time and temperature, and it reached a maximum of 55.57% in 45 min at room temperature with 0.1% ClO2 as oxidant. When the temperature was increased to 65°C, the removal rate reached a maximum of 98.85% in 30 min. Based on the above results, a new chemical method was set up to remediate the cyanide contaminated soils with chlorine dioxide. This study suggests that chemical oxidants may be a feasible option for cleaning soils contaminated with cyanide.
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