Influence of surface chemistry of activated carbon electrodes on electro-assisted adsorption of arsenate

In this work, the influence of oxygen-containing surface groups of activated carbon electrodes on the charge efficiency of electro-assisted adsorption of As(V) was investigated. It was distinguished between activated carbons modified through acidic (oxidation) and thermal (reduction) treatments, starting with a granular pristine commercial activated carbon of bituminous origin. The textural characterization of the three materials showed that the treatments did not produce significant changes in the surface area and in the distribution of pores. The three carbon samples were used to fabricate packed electrodes with stainless-steel mesh as electric current collector. This work report that the application of anodic potentials (1.01 and 1.41 V vs. NHE) increased the adsorption capacity and rate of arsenate uptake in solutions containing only this contaminant (2.5 mg L-1) at pH 7. The oxidized carbon electrode presented the lowest capacitance and adsorption capacity during electro-adsorption (0.33 mg g(-1)), compared to pristine material (1.77 mg g(-1)). On the other hand, the reduced electrode displayed the highest adsorption capacity of arsenate (3.14 mg g(-1)) when applying a potential of 1.01 V. The results were correlated with the potential of zero charge values. In addition, for this material, the rate of kinetics increased 26.7 % compared to experiments without applied potential.