Abstract:
Rice hulls and Coconut shells are used as raw materials to prepare activated carbon by
chemical activation, as well as by physical activation, using phosphoric acid and steam
as activating agents respectively. The effect of process variables such as chemical
activation temperature, impregnation ratio (w/w)% between the raw material and
phosphoric acid and soaking time, on adsorption of methylene blue was investigated in
order to find out the optimum conditions for adsorption. The adsorption capacity of
methylene blue on all the activated carbon samples prepared was determined using
spectrophotometric method. The activated carbon produced by using coconut shells
with soaking temperature of 400°C, impregnation ratio 80% and soaking time of 1 hour,
exhibits the best performance towards the methylene blue adsorption among all the
coconut shell based carbon samples studied. The activated carbon produced by using
rice hulls with soaking temperature of 370 °C, impregnation ratio 100% and soaking
time of 30 min, has better performance than the best coconut shell based activated
carbon sample, as it gave 2.7 times higher adsorption capacity. Also, this sample has
about 1.3 times higher adsorption capacity when compared with the physically activated
rice-hull based carbons produced in this study. It was also established that adsorption of
oxalic acid on chemically activated rice hull based carbon obeys the Freundlich
isotherm.
