Affiliations: Department of Environmental Science, Zhejiang University, Hangzhou 310028, China
Abstract: Water solubility enhancements of naphthalene (Naph), phenantherene (Phen) and pyrene (Py) in sodium castor oil sulfonate (SCOS) microemulsions were evaluated. The apparent solubilities of PAHs are linearly proportional to the concentrations of SCOS microemulsion, and the enhancement extent by SCOS solutions is greater than that by ordinary surfactants on the basis of weight solubilization ratio (WSR). The log K_{em} values of Naph, Phen, and Py are 3.13, 4.44 and 5.01 respectively, which are about the same as the log K_{ow} values. At 5000 mg/L of SCOS conccentration, the apparent solubilities are 8.80, 121, and 674 times as the intrinsic solubilities for Naph, Phen, and Py. The effects of inorganic ions and temperature on the solubilization of solutes are also investigated. The solubilization is improved with a moderate addition of Ca^{2+}, Na^{+}, NH_{4}^{+} and the mixture of Na^{+}, K^{+}, Ca^{2+}, Mg^{2+} and NH_{4}^{+}. WSR values are enhanced by 22.0% for Naph, 23.4% for Phen, and 24.6% for Py with temperature increasing by 5°C. The results indicated that SCOS microemulsions improve the performance of the surfactant-enhanced remediation (SER) of soil, by increasing solubilities of organic pollutants and reducing the level of surfactant pollution and remediation expenses.
