Effect of electrochemical reduction and oxidation of a viscose rayon based activated carbon cloth for Cr(VI) sorption from aqueous solution

A viscose rayon based activated carbon cloth (ACC) was electrochemically reduced and oxidized to enhance its anion and cation sorption capacity for comparison with the as-received ACC. ACCs were characterized by chloride capacity measurement, sodium capacity measurement, pH titration, elemental analysis, Brunauer-Emmet-Teller surface area measurement, Fourier transform infrared spectroscopy analysis and scanning electron microscopy. Batch sorption experiments showed that chromium(VI) sorption capacity of electrochemically reduced ACC increased 2.12 times at solution pH 4 and chromium(VI) sorption capacity for electrochemically oxidized ACC increased 11.35 times at solution pH 8. The highest chromium(VI) sorption capacity was obtained on electrochemically reduced ACC at solution pH 4 (i.e., 3.8 mmol/g). Chromium(VI) sorption decreased with an increase in solution pH for electrochemically reduced ACC, while it increased with an increase in solution pH for electrochemically oxidized ACC. Chromium(VI) ions were sorbed onto ACCs by ion exchange.