Electrochemical Reactivation of Granular Activated Carbon: Effect of Electrolyte Mixing

Bench-scale experiments investigated the effect of electrolyte mixing on the effectiveness of an electrochemical reactor for the reactivation of granular activated carbon (GAC). Two different GACs (F-400 and WV-B) were loaded with phenol via batch adsorption tests, then electrochemically reactivated and finally reloaded with phenol. Reactivation was conducted in a recirculating flow reactor with a 0.1  M NaCl solution as the electrolyte. Cathodic reactivation was more efficient than the anodic reactivation and increasing the degree of electrolyte mixing decreased the cathodic reactivation efficiencies, while there was no significant change in the anodic reactivation efficiencies. Higher degrees of electrolyte mixing decreased the local pH at the cathode and consequently reduced the desorption driving force and therefore reduced the reactivation efficiency. The electrolyte mixing lowered the cell voltage. However, this advantage was overshadowed by the increased energy consumption required for the electrolyte pumping, the reduction of the oxidation rate of phenol, and a 20% reduction in the reactivation efficiencies. Thus, electrolyte mixing of the electrolyte is not recommended in the electrochemical reactivation of GAC.