[Elution of endosulfan from contaminated soil by surfactants and their combination]

The elution efficiency and dynamic characteristic of endosulfan from the contaminated soil were studied using non-ionic surfactants and anionic/non-ionic surfactants in the presence or absence of Na2SiO3 with batch experiment and parallel desorption experiment. The results showed that the elution percents of alpha-, beta-endosulfan followed a decreasing order of Tween 80/SDS, Tween 80 and Triton X-100 in the absence of Na2SiO3, while that by Triton X-100/SDS at low concentration (100-500 mg x L(-1)) and high concentration (800-1000 mg x L(-1)) were lower and higher than those by the corresponding concentrations of Triton X-100, respectively. The elution efficiencies for four elution modes obviously increased in the presence of Na2SiO3, and the elution percents of alpha-, beta-endosulfan followed a decreasing order of Tween 80/SDS, Tween 80, Triton X-100/SDS and Triton X-100, and that of alpha-endosulfan were as 1.17-2.73, 1.87-4.02, 1.85-6.56 and 1.87-2.85 times as that in the absence of Na2SiO3. The elution process of endosulfan could be described by a 4-parameter biphasic first-order kinetic model, and obviously showed a rapid elution phase and a slow elution phase. Both of the elution percent and elution rate of beta-endosulfan were lower than those of alpha-endosulfan, which indicated that beta-endosulfan was difficult to be eluted from soil. The addition of Na2SiO3 could increase the rate constants of rapid elution and slow elution, and decrease the slow elution percent. Compared with other elution modes, Tween 80/SDS in the presence of Na2SiO3 could elute endosulfan from soil more effectively and rapidly, and shown as a fine mixed eluent for endosulfan.