Abstract

In recent years, contamination by dicofol-type DDTs has attracted immense concern as a new source of DDT pollution. In this study, sediment samples from a dicofol manufacturing factory in Tianjing, China exhibited serious DDT contamination [p,p'-DDE (115.27 mg kg^-1) and p,p'-DDT (11.84 mg kg^-1)]. Results of the batch experiments showed that total DDT degradation rates increase as S₂O₈^2?/Fe²⁺ molar ratios increase. The S₂O₈^2-/Fe²⁺ molar ratios used in this study were as follows: 60/10 < 10/30 < 20/30 < 60/50 < 60/20 < 40/30 < 60/40 < 60/30 < 80/30. Their corresponding degradation rates were 31, 43, 52, 69, 70, 71, 72, 89, and 91 ug g^-1, respectively. The optimal S₂O₈^2-/Fe²⁺ molar ratio was 60/30, which resulted in 64% and 96% degradation of p,p'-DDE and p,p'-DDT, respectively. However, when an excessive amount of ferrous ion was used (<S₂O₈^2-/Fe²⁺ molar ratio of 60/30), then competition for SO₄^? between ferrous ion and DDTs resulted in decreased DDT degradation efficiency and increased persulfate decomposition (represented by the generated amount of sulfate). Our results implied that a slow and steady production of sulfate free radicals is favorable for DDT degradation, and that Fe²⁺ availability plays an important role in controlling persulfate reactions activated by ferrous ion. Fe²⁺-activated persulfate oxidation may be significant in developing environment friendly and fast-remediation options for DDT-contaminated sediments and soil. Therefore, this study contributes to current knowledge on remediating DDT contamination.

This work is licensed under a Creative Commons Attribution 4.0 License.