Influence of the Type of Surfactant on the Mobility of Flushing Fluids for Electro-Remediation Processes

The mobility of four flushing fluids in an electro-remediation process has been studied. A mock-up plant with two rows of three electrodes positioned in semipermeable electrolyte wells was used in this study. Two different cases were considered: first an initial state when the soil was wet with water and the addition of surfactant starts, and second a second state when the surfactant front had passed through the soil. The results show that the electro-osmotic flux strongly depends on the nature of the flushing fluid and on the voltage gradient applied between electrode rows. The presence of ionic surfactants (both cationic and anionic) led to lower electro-osmotic flow-rates. The concentration of surfactants in the drain tanks increased in the case of the flushing fluid with the non-ionic surfactant because the surfactant transport was more efficient. Conversely, the anionic surfactant accumulated more in the injection well. This finding is related to the effect of migration, which in the reception wells was opposite to the electro-osmotic flux.