Efficient Remediation of an Actual Cyanide-Contaminated Soil by Persulfate Oxidation: Tube- and Column-Scale Studies and Restoration Quality Evaluation

The removal of cyanide complexes in an actually contaminated soil (pollution level 930 mg CN/kg soil) by sulfate radical (SO4 center dot)-based advanced oxidation processes (SR-AOPs) was investigated in tube and column tests. Experimental parameters including soil/water ratio, sodium persulfate (SP) dosage, Fe2+/ tartaric acid/SP mole ratio, and reaction time were optimized in the tube test. The column-scale experiment shows that the addition of SP solution at the bottom and middle of the column was more effective than injecting one slug from the column bottom. Experimental results show that more than 98% of total cyanide (TCN) was removed in the soil within 4 h, and the quality of the remediated soil can meet the requirement of construction land. SP dosage of the column experiments is 23.6% higher than that of the tube tests, but no soil-water separation was needed for the column treatment. The soil corrosivity to building materials was only slightly modified by the oxidation treatment, and the numbers of indigenous microbes may quickly restore after nutrient stimulation. Overall, the results underline the significance and the potential of iron chelate-activated SR-AOPs in the remediation of highly contaminated soils by the column oxidation.