Activated carbon adsorption in oxidizing environments

Molecular oxygen-induced enhancement in the adsorption capacity of GAC was investigated thoroughly from sorbate types point of view. Isotherm studies on phenol, o-cresol, and 4-nitrophenol at 23°C showed a 20-163% increase in retention capacities with the incremental capacity increasing with decreasing equilibrium concentrations. The incremental capacity was strongly dependent on the DO to GAC mass ratio and the adsorptive capacity under anoxic conditions. The phenomenon was observed when oxidizing agents such as hydrogen peroxide and potassium permanganate were used instead of molecular oxygen. GC-MS analysis performed on GAC extracts suggested polymerization of adsorbates on the carbon surface as a potential reason for this enhancement phenomenon. Four different aliphatic compounds namely chloroform, bromoform, 1,1,1 trichloromethane, and 1,1,2,2 tetrachloroethane were also studied. The results showed no significant effect on the adsorptive capacity of GAC for those aliphatics due to dissolved oxygen existence in the test environment. Significant enhancement was found in the case of wastewater samples from both domestic and industrial sources.