Chemical Behavior of Cadmium in Purple Soil as Affected by Surfactants and EDTA

A soil batch experiment was conducted to investigate both separate and compound effects of three types of surfactants:anionic dodecylbenzene sulfonic acid sodiumsalt (DBSS), cationic cetyltrimethylammonium bromide (CTAB), and nonionic nonyl phenol polyethyleneoxy ether (TX-100), as well as ethylenediaminetetraacetic acid (EDTA) on cadmium solubility, sorption kinetics, and sorption-desorption behavior in purple soil. The results indicated that both individual application of the three types of surfactants and surfactants combined with EDTA could stimulate Cd extraction from the soil with a general effectiveness ranking of EDTA/TX-100 ＞ EDTA/DBSS ＞ EDTA/CTAB ＞ EDTA ＞ TX-100 ＞DBSS ＞ CTAB. Further study showed that the compound application of surfactants and EDTA had stronger (P ＜ 0.05)effects on Cd solubility than those added individually. The application of surfactants and EDTA to purple soil (P ＜ 0.05)decreased the proportion of Cd sorbed, while their effectiveness ranking was similar to that of enhanced solubilization. The sorption kinetics of Cd in purple soil was best described by the double-constant equation, while the Freundlich equation gave an excellent fit to the sorption isotherm curves. Therefore, surfactant-enhanced remediation of Cd contaminated soil is feasible and further research should be conducted.