Switching effects of electrode polarity and introduction direction of reagents in electrokinetic-Fenton process with anionic surfactant for remediating iron-rich soil contaminated with phenanthrene

This study investigated effective operating method of enhanced electrokinetic-Fenton (EK-Fenton) process with anionic surfactant to remediate contaminated iron-rich clayey soil with phenanthrene, which had soil properties being frequently in contaminated sites. Introduction of 30 mM SDS as H2O2 stabilizer improved not only H2O2 stability but also degradation of phenanthrene compared to experiment without SDS. However, electrical potential drop in regions near cathode terminated electro-osmotic flow, and then phenanthrene in region near cathode kept initial concentration before switching of the electrodes polarities and introduction direction of reagents. After the polarity of the electrodes and introduction direction of reagents were switched, electro-osmotic flow was re-generated with re-distribution of electrical potential and electrical current. Furthermore, after switching electrode, decrease of iron concentration and pH in the soil specimen near cathode before switching electrode generated decrease of H2O2 decomposition rate. Therefore, H2O2 could be introduced in the cathode regions before switching the polarity of the electrodes and introduction direction of reagents. Furthermore, residual phenanthrene was degraded homogeneously after switching of the electrodes polarity and introduction direction of reagents, and then about 70% phenanthrene could be degraded.

► Introduction of 30 mM SDS as H2O2 stabilizer improved H2O2 stability and phenanthrene degradation. ► Switching of polarity and introduction direction of reagents could re-generate the electro-osmotic flow. ► H2O2 could be introduced regions near cathode before switching. ► Residual phenanthrene was degraded homogeneously after switching.