Water Science & Technology: Water Supply—WSTWS Vol 9 No 2 pp 159–165 © IWA Publishing 2009 doi:10.2166/ws.2009.252

Effects of acid treatment on the improvement of specific capacitance and deionization efficiency of porous carbon electrodes

R. L. Machunda, H. Jeon, J. K. Lee and J. Lee

We report the effect of acid treatment on porous carbon materials on their double layer capacitance and electrosorption of ions in capacitive deionization systems. The as-received activated carbon cloth (ACC) had the capacitance value of 210 F/g and was markedly (~175%) improved when treated with acid solution. Surface functional groups such as hydroxyl, quinines, lactones and ethers on carbon after modification were increased by 40% and 29% with HNO₃ and H₂SO₄ respectively. In capacitive deionization test of NaCl solution, the ACC treated with HNO₃ had more than two times removal efficiency when charged with a 1.5 V current than the untreated one. This is attributed to activation and changes of surface functional groups when charged with a current.

Keywords: acid treatment; activated carbon cloth; capacitive deionization; functional groups; specific capacitance

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