Wastewater treatment by multi-stage batch adsorption and electrochemical regeneration

Abstract

The removal and destruction of a tri-phenyl methane dye, Acid Violet 17 (AV17), from aqueous solution by adsorption and electrochemical regeneration was studied using a graphite intercalation compound (GIC) adsorbent. It was demonstrated that the adsor­bent could be regenerated by anodic oxidation of the adsorbed dye in a simple electro­chemical cell. The GIC adsorbent recovered its initial adsorption capacity after 40 to 60 min of treatment at a current density of 10 mA cm - 2 , corresponding to a charge of 12 to 18 C g - 1 of adsorbent. The charge passed is consistent with that expected for mine­rali­sation of the dye, suggesting that the dye was removed and destroyed with high charge efficiency. The energy cost of the regeneration was found to be around 120 J per g of adsorbent regenerated or 115 J per mg of the AV17 dye removed and destroyed. A model describing the process of wastewater treatment by multiple cycles of adsorption and electrochemical regeneration, based on adsorption isotherm data, has been deve­loped and validated. It was found that relatively modest improvements in the adsorption capacity of the adsorbent material could significantly improve the process performance.