Surface properties of electrochemically oxidised viscose rayon based carbon fibres

A viscose rayon based activated carbon cloth (ACC) was subjected to electrochemical oxidation under a wide variety of current conditions to modify the surface properties. The changes in the surface properties were physically and chemically characterised. The cation exchange capacity of ACC increased with an increase in the extent of oxidation. The electrochemically oxidised ACC at 1.1 A for 6 h showed highest cation exchange capacity without any change in surface morphology. A loss of 49% BET surface area and a significant loss in microporosity were observed and attributed to blockage of pores through formation of carboxylic acidic groups and humic substances. However, the cation exchange capacity and oxygen content increased by about 365% and 121%, respectively. Increase in surface acidity shifted the point of zero charge from pH of 6.8 to 2.8 and the isoelectric point from pH of 3 to 1.15. The optimum constant current for electrochemical oxidation was found to be 1.1 A.