Application of sodium dodecyl sulfate and humic acid as surfactants on electrokinetic remediation of cadmium-contaminated soil

The evaluation of a chemical (sodium dodecyl sulfate, SDS) and a natural (humic acid) surfactant, in order to enhance the electrokinetic removal of cadmium from contaminated soil has been investigated in this study. SDS was used either for soil washing as well as purging solution. When SDS was used as purging solution in the electrode compartment, there was no cadmium solubility, since SDS can not migrate in the soil specimen. On the contrary, using SDS as washing solution more than 90 % of cadmium removal was achieved. Humic acid was applied on the contaminated soil at various concentrations, while 1M acetic acid was used as purging solution in the cathode compartment. Under acidic conditions humic acid was complexed with cadmium forming relatively weak bonds. This explains the results obtained, since as it was proved that the extraction efficiency of cadmium was not affected by the increase of humic acid concentration.

In this study the electrokinetic removal of cadmium was evaluated by the application of SDS and humic acid as surfactants. First, the use of SDS as purging solution in the electrode compartment was not sufficient to solubilize cadmium as it could not migrate in the soil specimen. When SDS was used as washing solution more than 90% removal was achieved in a very short of time. Second, under acidic conditions the use of humic acid caused the formation of weak complexes with cadmium. Furthermore, the extraction efficiency of cadmium was not affected by the increase of humic acid concentration.