纳米四氧化三铁/过碳酸钠降解DDTs及降解产物

以滴滴涕(DDTs)为降解对象,采用基于纳米Fe_3O_4/过碳酸钠的新型非均相类芬顿试剂进行处理,考察了纳米Fe_3O_4投加量、过碳酸钠投加量和初始pH值对水中DDE、DDD、o,p′-DDT和p,p′-DDT4种DDTs去除率的影响.同时,采用响应面法进行多因素实验设计,利用二次多项式和逐步回归法拟合了DDTs降解率与实验条件之间的关系,并对实验条件进行了优化.结果表明,纳米Fe_3O_4和过碳酸钠单独处理对DDTs降解率的最大值均小于60%,两者联合处理可大幅度提高DDTs降解率,表明两者对于DDTs降解存在较好的协同作用,纳米Fe_3O_4/过碳酸钠体系在碱性条件下可以有效降解水样中的DDTs.在纳米Fe_3O_4投加量为8.0 g·L~(-1)、过碳酸钠投加量为1.5 g·L~(-1)、溶液初始pH值为11的条件下,DDE、DDD、o,p′-DDT和p,p′-DDT的降解率分别为95.5%、84.3%、96.8%和87.5%,与模型预测值接近.自由基猝灭实验结果表明,羟基自由基是降解过程中主要的活性物质.GC/MS检测结果表明,DDTs脱氯生成DDE和DDD,随后DDE和DDD进一步降解生成DDMU、o,p′-TDE、DDNU、DDMS及DBP等物质.

Degradation of DDTs by nano Fe3O4/sodium percarbonate and their degradation products

This paper treated DDTs by a new heterogeneous Fenton reagent based on nano Fe₃O₄ and sodium percarbonate. The effects of nano Fe₃O₄ dose, sodium percarbonate dose, and the initial pH value on degradation efficiency of four DDTs, including DDE, DDD, o,p''-DDT, and p,p''-DDE in water was analyzed. The multi-factor experimental design was carried out by response surface methodology. The relationship between the degradation rate of DDTs and experimental conditions was fitted by quadratic polynomial and stepwise regression method. The experimental conditions were optimized. The results showed the maximum degradation rates of DDTs by nano Fe₃O₄ and sodium percarbonate alone were both less than 60%. The combined nano Fe₃O₄/sodium percarbonate treatment of DDTs could significantly increase the degradation rate of DDTs, indicating that they have a good synergistic effect on DDTs degradation. The combined nano Fe₃O₄/sodium percarbonate treatment process can effectively degrade DDTs in alkaline aqueous system. When the nano Fe₃O₄ dose was 8.0 g·L^-1, the sodium percarbonate dose was 1.5 g·L^-1, and the initial solution pH value was 11, the removal rates of four DDTs, including DDE, DDD, o,p''-DDT and p,p''-DDE, reach 95.5%, 84.3%, 96.8%, and 87.5%, respectively, which were all close to the values from verification experiment result. The free radical quenching test proved that hydroxyl radicals are the main active substances during the degrading process. GC/MS test results showed the DDTs dechlorination produces DDE and DDD, and further degradation produces DDMU, o,p''-TDE, DDNU, DDMS and DBP.