活化过硫酸钠氧化法修复DDTs污染场地土壤研究

Application of Activated Persulfate Oxidation Method in Degradating DDT in Field Contaminated Soil

本研究探讨了利用Fe2+活化过硫酸钠氧化修复长江三角洲地区某典型DDTs污染场地土壤的可行性。研究了不同因素对目标污染物去除效率的影响,包括起始pH与矿物耦合因素、过硫酸钠/Fe2+浓度比值因素和过硫酸钠浓度因素等。结果表明,当磁铁矿和赤铁矿投加到只含有过硫酸钠的泥浆体系时,在酸性和中性条件下都能显著提高DDTs的降解率(P<0.01),并且pH 3.2条件时DDTs的降解率高于pH 7.7条件时的DDTs降解率;零价铁和菱铁矿因其二价铁含量较高,导致矿物近表面Fe2+过剩而消耗硫酸根自由基,进而降低了DDTs氧化效率。pH 3.2时,Fe2+/Na2S2O8的最优值为1/20,在此条件下0.16 mol/L的活化过硫酸钠反应24 h后得到DDTs最高降解率约为90%。同时还比较了活化过硫酸钠、过硫酸钠、Fenton试剂、H2O2、双氧化试剂(活化过硫酸钠与双氧水混用)和高锰酸钾6种氧化剂对DDTs氧化效果,评价了不同氧化剂的优劣之处。研究发现Fe2+活化过硫酸钠可以有效地降解DDTs的4种同系物,pH 3.2条件时6种氧化剂对DDTs的氧化降解率由大到小顺序为:活化过硫酸钠>过硫酸钠>Fenton试剂>双氧化剂>高锰酸钾>H2O2。本研究结果表明活化过硫酸钠氧化法是修复DDTs污染场地土壤的有效方法,有较好的应用推广性。

This paper evaluated the use of Fe2＋ activated sodium persulfate oxidation method to remedy DDT-contaminated soil from a typical former organochlorine pesticide field in the Yangtze River Delta. The influence of different factors on the target pollutants removal efficiency was studied, including the initial pH and mineral coupling factor, sodium persulfate/Fe2＋ concentration ratio factor and oxidant concentration factor. Results showed that the magnetite and hematite, when adding to slurry system with only sodium persulfate, could significantly improve the degradation of DDTs rate （P 〈 0.01） under the acidic and neutral condition, and the DDTs degradation rate at pH 3.2 was higher than when pH was 7.7. Due to high ferrous content of zero-valent iron and siderite, Fe2~ concentration nearby mineral surface was excess and Fe2~ would react with sulfuric radical, thereby lowering the DDTs oxidation efficiency. The optimal persulfate/Fe2~ ratio in this slurry system was found to be 20 ： 1 at pH 3.2, while the most effective in degrading DDTs was more than 90% within 24 h. At the same time, results of DDT oxidation by six kinds of oxidants including Fe2＋ catalyzed sodium persulfate, sodium persulfate, Fenton reagent, hydrogen peroxide, double oxidation reagents （mixture of activated persulfate and hydrogen） and potassium permanganate were compared, and evaluated the advantages and disadvantages of different oxidants. DDTs oxidation efficiency and rates by six oxidants followed degrading sequence of Fe2＋ catalyzed sodium persulfate 〉 sodium persulfate 〉 Fenton reagent 〉 double oxidation reagents 〉 permanganate 〉 hydrogen peroxide at pH 3.2. This study indicated that the application of activated persulfate oxidation is a feasible method to treat soil contaminated by DDT, which is suitable in remediation applications.