The effect of surface metal oxides on activated carbon adsorption of phenolics

The adsorptive capacity of granular activated carbon (GAC) for many phenolic compounds has been found to increase in the presence of molecular oxygen (oxic condition). This enhanced adsorption is due to oxidative coupling of the adsorbed molecules and is accompanied by significant oxygen consumption and decreased adsorbate recovery by solvent extraction. The present study investigated the possible catalytic effect of metals and metal oxides on activated carbon surface for this reaction. The ash and metal content of seven GACs were compared to the enhanced adsorption found under the oxic conditions, oxygen consumption during adsorption and adsorbate recovery. No correlation between ash or metal content and these parameters was found. Reduction of metal content by acid washing did not impact the adsorptive properties of the carbon. In addition, a carbonaceous resin impregnated with metal oxides of copper, iron and manganese showed no ability to promote oxidative coupling of phenolics. The results of this study suggest that acid-washable metals and metal oxides that are present on the surface of activated carbon are not a key factor in promoting oligomerization of adsorbates in the presence of oxygen.