Regeneration of acid orange 7-exhausted granular activated carbon with dielectric barrier discharge plasma

A novel process for regenerating activated carbon based on high active species (O3, OH, HO2, O2 and RO, etc.) generated by dielectric barrier discharge (DBD) oxidation was proposed. The method was assayed with granular activated carbon (GAC) exhausted with azo dye acid orange 7. The regeneration efficiency of this technique was evaluated, and the regeneration efficiencies could reach over 73% after five continuous regeneration cycles. The effects of DBD on the adsorption rate, the texture characteristic, the surface chemistry, and the adsorption capacity of GAC samples after different regeneration cycles were investigated. The adsorption rate remained stable after multi-successive regeneration cycles. The analysis of texture of GAC samples showed that the specific surface area and pore volume decreased after DBD regeneration cycles except for the first regeneration sample. It was observed that DBD also resulted in the increase of carboxylic functional groups of GAC's surface. Furthermore, all adsorption equilibrium isotherms fitted the Freundlich model fairly well, which demonstrated DBD plasma did not appear to modify adsorption process but to shift the equilibrium towards lower adsorption concentrations.