Effects of Surfactants on the Sorption of Sulfamethoxazole by Sediment
Yuan Zhang1, Ziqiang Tian1, Jian Xu1, Zhenxing Zhong1, 2, Changsheng Guo1, Tao Yu1, Yucheng Chen2
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1State Key Laboratory of Environmental Criteria and Risk Assessment,
Laboratory of Riverine Ecological Conservation and Technology,
Chinese Research Academy of Environmental Sciences, Beijing 100012, China
2College of Resources and Environment, Southwest University, Chongqing 400716, China
Pol. J. Environ. Stud. 2012;21(5):1505–1511
Adsorption and desorption of sulfamethoxazole (SMX) at water-sediment interfaces from Taihu Lake, China, were investigated in this study. The effects of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), on the adsorption/desorption processes were also studied. Results show that adsorption and desorption could be well described by the Freundlich isotherm model. CTAB significantly increased the SMX adsorption on sediments, while SDBS decreased the adsorption of SMX, probably because SDBS at high concentrations competed in the limited adsorption sites with SMX, and the addition of SDBS increased SMX solubility, thereby reducing the SMX adsorption on sediment. The degree of adsorption irreversibility was quantified by the Thermodynamic Index of Irreversibility (TII) values. It shows that the TII values increased with the increase of CTAB concentration, and decreased with the increase of SDBS concentration. These results imply that cationic and anionic surfactants may have contrasting impacts on the distribution and transport of SMX in the environment.