Shenghong Kang,Guozhong Wang,Huijun Zhao,Weiping Cai
The remediation of soil contaminated by 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) has been a challenge. In this paper, the degradation performances of the ball milling-induced plate-like sub-microstructured zero valent iron (SMZVI) to DDT in a real soil environment is studied. It has been found that such SMZVI exhibits much higher degradation performances to DDT in soil than commercial ZVI powders under acidic conditions. More than 95% DDT could be degraded within 80 min in the 5 ppm DDT-contaminated soil with addition of 50 mg g–1 SMZVI, which is much better than the previously reported results. The time-dependent DDT removal amount can be well described by the pseudo first-order kinetic model. Further experiments have revealed that the ZVI dosages, surfactant’s and acidic additions, and the weight ratio of soil-to-water in the slurries are important to DDT degradation, and the degradation products were mainly DDD (a product with less chlorine). An acid-assisted ZVI-induced reductive dechlorination process is proposed, which can well explain the DDT degradation behaviors in soil and the influence from the other factors. This work not only deepens the understanding of DDT degradation in soils based on ZVI but also demonstrates that the SMZVI could be a promising material for DDT degradation in real environments.
In this study, three different structures of MnO 2 were synthesized and used to activate peroxymonosulfate (PMS) for the degradation of DDT in aqueous solutions. It was found that DDT was efficiently degraded in the MnO 2 /PMS system and the degradation rate was dependent on the properties of MnO 2 including crystal structure (followed the order: α-MnO 2 > γ-MnO 2 > β-MnO 2 ), surface area and Mn(III) content. Sulfate radicals (SO 4 − ) was primarily responsible for the degradation of DDT based on the results of electron paramagnetic resonance (EPR) and quenching experiments. The degradation of DDT was suppressed at alkaline pH because the formation of SO 4 − was inhibited. The results of GC–MS indicated that dichlorobenzophenone, 4-chlorobenzoic acid and benzylalcohol were the dominant intermediates for DDT degradation. The possible pathways of DDT degradation were proposed according to the identified products.
A novel Ni@FeO x composite was prepared via a facile hydrothermal method and their heterogeneous catalytic activity in Fenton-like reaction to decompose 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) pollutant was systematically investigated. FeO x was doped by nickel ions and modified by nickel particles in this process. In the Fenton-like reaction, 40%Ni@Fe 3 O 4 could remove almost 90% of DDT within 8 h in the presence of H 2 O 2 , exhibiting much higher rate constant than any other systems with lower Ni content. It indicated that too much catalyst is unhelpful to increase the activity further, and excessive H 2 O 2 even decreases the activity. The composite exhibits excellent activity at pH = 7, almost as high as in acid environment, superior to homogenous catalysts. According to GC–MS results, the decomposing process mainly is a successive dechlorination process, partially accompanied with the fragmentation of small molecular. The Ni 2+ and Ni 0 are deduced to promote the Fe 3+ /Fe 2+ cycle together to provide abundant Fe 2+ for Fenton reaction .
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