Effect Of Anionic Surfactant On The Sorption Behavior Of DDT On Jiaozhou Bay Sediment

Organochloyine pesticides (OCPs) are priority pollutants and typical persistent organic pollutants (POPs). Because of their persistence, half-volatility and high toxicity in the environment, OCPs are great harmful to the environment and human health. Although their use has been restricted in our country since 1983, OCPs are still the most widespread POPs in the environment due to the persistence. These OCPs are transported in to marine environment through different ways, such as atmospheric transport and river transportion. Because OCPs have a strong affinity for suspended particles, they tend to subsequently settle down with sediments to the bottom of the ocean. Meanwhile, OCPs in sediments can also release into water by resuspension and lead to recontamination of water. Therefore the study on migration and transformation of OCPs in water and sediments is very important.In this thesis,the sorption behaviors of DDT on Jiaozhou Bay sediments were studied in the presence of an anionic surfactant dodecylbenzenesulfonic acid sodium(sodium dodecylbenzene sulfonate, SDBS) by laboratory experimently. In addition, the effect of CTAB (cetyltrimethylammonium bromide, a cationic surfactant) was also investigated. Major results and conclusions are shown as follows:1) The sorption kinetic process of DDT on the sediments followed the pesudo-second-order kinetic rate equation. The sorption of DDT was accelerated remarkably by the addition of SDBS and CTAB, and CTAB showed a more remarkable impact.2) The sorption isotherms of DDT on sediment could be described by the Freundlich isotherm. The results showed that SDBS with the initial concentrations of 5, 10, 15, 30 mg·L^-1 and CTAB with the initial concentrations15, 30, 50 mg·L^-1 could remarkably enhance the sorption of DDT and linearized the isotherms of DDT. CTAB played a more important role. SDBS had a negative effect on the sorption when the initial concentration was 60 mg·L^-1. 3) The sorption capability of DDT on the sediment with different treatment procedures was in such a sequence as: HCl treated﹥H₂O-treated﹥H₂O₂ treated. The sorption capability correlated with the contents of the organic matter in the sediments. The presence of SDBS could accelerate the sorption of DDT on H₂O₂ treated sediment while reduced the sorption of DDT on HCl treated sediment.4) The effects of environmental factors, such as temperature, salinity, on the sorption of DDT were obvious. The sorption amount of DDT on sediments increased with increasing salinity, but decreased with increasing of temperature in both single and combined systems.The sorption capacity was also increased with the decrease of sediment particle size.5) Estimation of thermodynamic parameters indicated that the sorption of SDBS and DDT was spontaneous (ΔG^θ<0) and exothermic (ΔH^θ<0) with an increase in the degree of freedom (ΔS^θ>0). In the presence of 15 mg·L^-1SDBS and CTAB caused |ΔG^θ| and|ΔH^θ|values higher andΔS^θvalue smaller during the DDT sorption process.