Application of electrochemical depassivation in PRB systems to recovery Fe^0 reactivity

Permeable reactive barriers （PRBs） show remarkable Cr（VI） removal performance. However, the diminished removal rate because of mineral fouling over time is the bottleneck for application of PRBs. The present study demonstrated that electrochemical depassivation was effective for recovering the Fe^0 reactivity, and minerals can be cleaned layer by layer with no secondary ion contamination and no transformation from Cr（III） to Cr（VI）. The removal recovery rate increased with increasing electrolysis voltage before reaching the optimal electrolysis voltage, and then decreased as the electrolysis voltage further increased. The recovery effect at electrolysis voltages of 5, 10, and 15 V show the same trend as a function of electrolysis time, where recovery rate first increased and then decreased after reaching the optimal electrolysis time. The Cr（VI） removal rate significantly decreased with increasing electrolysis distance. Furthermore, Fe^0 brush meshes electrode, Fe^0 fillings, and polyvinyl chloride （PVC） meshes separators were combined to create an Electro-PRB configuration for the caisson excavation construction technique, which lays the foundation for establishment of promising Electro-PRB systems to treat Cr（VI）-contaminated groundwater.