Electrochemically reversible foam enhanced flushing for PAHs-contaminated soil: Stability of surfactant foam, effects of soil factors, and surfactant reversible recovery.

Although surfactant foams enhanced-remediation for PAHs-contaminated soil has been proved to be an effective method, lack of simple/economic surfactant recovery methods from the eluent solutions limit its further remediation application for organic contaminated soil. Here, we prepared a electrochemically reversible ferrocene surfactant FcCHN(CH)CH (Fc12), then investigated the foaming ability and foam stability of Fc12 under its reduced (active state) and oxidation (inactive state) states and explored the flushing efficiency of reduced Fc12 foam for PAHs-contaminated soil and the recovery efficiency of collected eluent solution. The results showed that the foaming ability and foam stability of reduced Fc12 are greatly higher than those of oxidized Fc12, which is indicative of a well reversibly switchable characteristic of Fc12. The contaminated soil flushing efficiencies of reduced Fc12 for phenanthrene and pyrene were 65.28% and 46.45%. The respective desorption efficiency of phenanthrene and pyrene from collected eluent solutions were calculated to be 74.94% and 72.75% by electrochemical oxidation control, which indicates that Fc12 can be well recovered by simple electrochemical control. This study provides a feasible method for the recovery of surfactants from surfactant-enhanced remediation processes by simply electrochemical control.