| The batch equilibrium washing of copper (Ⅱ) in the soil matrix by anionic surfactant, sodium dodecylbenzyl sulfonate (SDBS), nonionic surfactant, octylphenoxypolyethoxyethanol (TX100), and their mixture (SDBS-TX100), was studied and compared. The influences of surfactant concentrations, washing time, pH values of solutions, ratios of soil to water and inorganic salts on washing efficiency were investigated. It was shown that the washing efficiency differed with the kinds of surfactants. Given the initial surfactant concentrations, the washing of copper (Ⅱ) by single SDBS was greater than those by single TX100 and the mixed SDBS-TX100. The washing efficiency by 6 000 mg·L-1 of SDBS was up to 46.3%, which was 5.8, 10.8, 10.8 and 19.3 times as those by SDBS-TX100(3∶1), SDBS-TX100(1∶1), SDBS-TX100(1∶3) and single TX100 respectively. When the ratio of soil to water was 1 to 10 and washing time reached 24 h, the washing efficiency achieved the maximum. pH values of solutions had obvious effect on the washing of copper (Ⅱ). The washing efficiency of copper decreased sharply with the increase of pH. At the high acidity (pH=1.50), the washing efficiency of copper (Ⅱ) was up to 95%. The smaller the ratios of soil to water were, the higher the washing efficiencies would be. The existence of inorganic salts with the certain concentrations, such as Na+, Ca2+and Mg2+, could not influence the washing capacity of surfactants, but the excessive Mg2+ (more than 500 mg·L-1) could resulted in the precipitation of SDBS. The results will make an implication for surfactant-enhanced remediation of soils contaminated with heavy metals. |
