Remediation Of DDTs Contaminated Soil By Combination Washing & Washing- Chemical Oxidation Combined Method

DDT is a kind of typical organochlorine pesticide, and one of the twelve Stockholm Convention persistent organic pollutants (POPs). DDTs are organic compounds that, to a varying degree, resist photolytic, biological and chemical degradation making the environment and human health in danger. Soil washing and chemical oxidation are two methods of soil remediation that can remove DDTs from the contaminated soil. In this study, comprehensive analysis was performed to assess the soil washing and chemical oxidation performance.1-propanol solution and hydroxypropyl-β-cyclodextrin (HPCD) solution were adopted to extract DDTs in soil, together with elevated temperature, combination and successive washing, to investigate the feasibility and removal efficiency of DDTs contaminated soil of Wuhan. The effectiveness of thermal activated persulfate oxidation for the destruction of DDTs in spiked soil was evaluated. In addition, the effect of oxidant dose, pH, metal oxides and oxidation times was investigated. The effect of the combination of soil washing and oxidation was also evaluated.The washing result showed that the thermal effect were notable within the experimental domain. Increasing the concentration of 1-propanol and HPCD in the solution could improve the amount of DDT removed in different degree. The binary interaction between the low concentration of 1-propanol and HPCD was remarkable. The combination of 1-propanol with the concentrtion of 20% and 50 g/L HPCD was chosen the best formula and could make the total DDTs removal up to 94% by four times washing under 50℃.In the oxidation study, we found that DDTs degradation increased with increasing the concentration of persulfate in solution, with the highest DDTs degradation of 95% obtained for 800mmol/L persulfate dosage. The acidic (pH=3) and neutral (pH=7) condition had little different in thermal activation batch experiments, however, high pH (pH=12) inhibited the oxidation. Evaluating the effects of metal oxides on the reactivity of persulfate oxidation revealed that hematite increased persulfate activity and siderite showed on the contrary. This may be due to the high dosage of Fe2+ around the surface of siderite, and superfluous Fe2+ consumed SO4-·.Moreover, the further research showed that with the low concentration of 1-propanol and HPCD alone could hardly achieve the remediation goal, while, the combination of soil washing and thermal activated persulfate oxidation made the DDTs removal up to 90%.A new idea with some certain application value was put forward in this study, and which, had a great significance in practice and theory for the removal of pollutnats from the contaminated soil.