Electrochemical reactivation of granular activated carbon: pH dependence

Abstract

The objectives of this paper were to verify and to quantify the dependence of granular activated carbon (GAC) electrochemical reactivation efficiency on the extreme pH values that occur at the electrodes. Phenol-loaded GAC was reactivated using a bench-scale electrochemical reactor. The pH values in the cathode and anode compartments during reactivation were 12 and 2, respectively. The pH of the electrolyte controlled the reactivation efficiency, and cathodic reactivation efficiencies were about 30% higher at pH 12 than at pH 2. Cathodic reactivation was about 20% more efficient than the anodic reactivation. The cathode, the reducing electrode, generates OH– ions, which increase the local pH at the cathode. Reduced phenol adsorbability at high pH promotes desorption from previously loaded GAC, thus increasing the reactivation efficiency. Greater phenol desorption was observed at pH 12 when the GAC was subjected to a 50-mA current than in the absence of a current. Thus, electrochemical reactivation is more efficient than chemical reactivation. Key words: granular activated carbon, pH, electrochemical, regeneration, reactivation, adsorption, desorption, phenol, F-400.