Electrochemical polarization of activated carbons for the reversible sorption of lithium ions

Abstract

Reversible sorption of lithium ions, present in trace amounts (10 ppm) in aqueous solution, was investigated for chemically and physically activated carbons. The adsorption properties of carbons were strictly defined by the physicochemical nature of their surface and their texture, i.e. pore volume, pore size distribution, surface area. The surface functionality of carbons was modified by washing, neutralization and electrochemical treatment, and its role in lithium sorption was determined. The influence of the oxygen-containing surface groups on the adsorption and desorption of lithium ions has been studied in the absence and the presence of an electrochemical polarization. A cathodic treatment of activated carbons during the sorption process significantly increased the lithium ion uptake. The possible mechanisms for lithium chemisorption and electrosorption are discussed. The role of charging an electrical double layer and the properties of the carbon/electrolyte interface during electrosorption have been considered, taking into account the peculiar structural and surface properties of the various sorbents used in this work.