[Influence of operating parameters on surfactant-enhanced washing to remedy PAHs contaminated soil]

Liquid/solid ratio (L/S) is an important influencing factor on contaminant removal in soil washing. The impact of different liquid/solid ratio on washing performance with Triton X-100 and Tween-80 was studied respectively and evaluated through removal ratio (R), surfactant adsorption loss ratio (V(s)) and solubilization percent (SP). The results presented that the performance of washing to remove PAHs in soil was significantly affected by liquid/solid ratio. PAH removal ratio was gradually increased with liquid/solid ratio increasing in the non-linear form, R presented nonlinear increasing until L/S = 10: 1. Surfactant adsorption loss ratio was insignificantly decreased. At the same liquid/solid ratio, removal ratio of Triton X-100 is more than that of Tween-80. V(s) presented drastic decreasing until L/S = 10: 1, adsorption loss ratio of Triton X-100 is less than that of Tween-80. SP was decreased after maximum value is occurred at L/S = 10: 1. Combining with R, V(s) and SP, L/S = 10:1 should be an effective washing point, Triton X-100 should be a reasonable washing solution and SP is a more effective index to chose liquid/solid ratio. When Triton X-100 is as washing solution and L/S = 10: 1, R, V(s) and SP is 74.7%, 23.47% and 48.99%, respectively.