Sorption and Desorption Kinetics of Surfactants TX-100 and DPC on Different Fractions of Soils

Abstract

Surfactant-based technologies are promising remediation alternatives. The information on sorption and desorption kinetics of surfactants on soils is important in the successful application of surfactant-based technologies. In this study, the sorption and desorption rates of nonionic surfactant TX-100 and cationic DPC were correlated to the surfactant concentration, soil organic matters (SOM), and soil cation exchange capacity (CEC). The results indicated that at higher initial surfactant concentrations, sorption rates of surfactants increased linearly with SOM and soil CEC for TX-100 and DPC, respectively. The sorption rates and initial surfactant concentrations followed the first order relation for TX-100 and second order for DPC. A linear relationship between the sorption rates of surfactants and soil characteristics was developed. The desorption rates of TX-100 and DPC increased linearly with the increased surfactant levels sorbed on soils but were irrelevant to soil characteristics and the contact time of surfactant sorption. The rate of surfactant desorption was similar as the amount of surfactants sorbed on soils was in the same range. The cationic DPC sorbed and desorbed at two orders of magnitude faster than the nonionic TX-100, suggesting that both sorption and desorption have to be considered in the remediation process.