Electrochemical Regeneration of Various Graphitic Adsorbents in an Air Agitated Sequential Batch Reactor

With the aim to address the issues related to the regeneration of activated carbon used for wastewater treatment, a novel and state of the art water treatment technology (Arvia) was introduced at the University of Manchester, UK. This technology employs the adsorption of dissolved toxic pollutants present in water onto the surface of graphitic adsorbents followed by their quick and cheap electrochemical regeneration in a simple electrochemical reactor. The main mechanism of regeneration is based on the anodic oxidation of adsorbed species at the adsorbent surface. The adsorbed species are thought to be completely mineralized. However, some of the adsorbed organic contaminants may lead to the generation of toxic intermediate breakdown species owing to incomplete mineralization and/or indirect oxidation of organics present in solution. The former phenomenon may also depend upon the adsorption capacity of the adsorbent to be used. In this paper, a range of graphitic adsorbents including graphite intercalation compound-bisulphate (GIC-bisulpahte), recycled vein graphite (RVG) and exfoliated graphite (EG) were selected so as to investigate the formation of breakdown products during their electrochemical regeneration. Relatively fewer quantities of breakdown products in terms of p-benzoquinone and 4chlorophenol were observed for EG. However, higher concentrations of oxalic acid were found for EG in comparison to GIC-bisulphate and RVG leading to conclude that the electrochemical degradation of phenol at the surface of exfoliated graphite could be through the direct oxidation of phenol into carboxylic acids.