Brackish Water Desalination by Capacitive Deionization using Nanoporous Carbon Aerogel Electrodes

Abstract

Capacitive deionization or otherwise called electrosorption is a collection / discharge process which relies on the formation of double-layer supercapacitor at the solution/electrode interface. The process needs micro-or nano-porous electrodes with very high specific areas and high salt sorption capacities, such as carbon aerogel, activated carbon cloth, carbon nanotubes and nanofibres. The objective of this study is to elucidate the efficiency of capacitive deionization on desalination of a brackish water sample containing 1000 mg/L NaCl using nano-structured carbon aerogel electrodes. Experiments showed that the removal efficiency of NaCl increases with increasing applied voltage, higher concentration gradient and less double-layer overlapping effect. At the optimum applied voltage of 1.5 Volt, pH 7 and initial NaCl concentration of 1000 mg/L the electrosorption capacity was found to be 14.22 mg NaCl/g carbon aerogel. The proposed process is reversible, as the electrode charge/discharge procedure can be repeated many times without any significant loss of salt sorption capacity in all cycles.