Activated carbon prepared from oil palm stone by one-step CO2 activation for gaseous pollutant removal

The feasibility of preparing activated carbons from oil palm stones by one-step CO2 activation was studied. These oil palm stones are major solid wastes generated from palm-oil processing mills. Experimental results showed that the particle size of the starting material and heating rate appeared to have no significant effects on the BET surface areas of the activated carbons but CO2 flow-rate had a significant influence. Increasing the heating rate resulted in slight reductions in the micropore surface areas. The BET and micropore surface areas of the activated carbons were also found to be dependent on the activation temperature and the hold time. The optimum conditions for activation were for an activation temperature of 850 degrees C and a hold time of 2 h, at which the BET and micropore surface areas were found to be maximum at 1410 and 942 m(2) g(-1) respectively. The pore size distributions of the activated carbon also confirmed these conditions. The development of microporosities in these activated carbons suggest their potential applications in gaseous pollutant adsorption. From chemical characterisation, the activation temperature was found to have an insignificant effect on the inorganic components of the activated carbons but possible effects on their surface functional groups. The amounts of NO2 adsorbed onto the oil-palm-stone activated carbons and a commercial one were measured during adsorption tests. The relationship between the amount of gas adsorbed and the BET surface area of the activated carbon indicated that the adsorptive capacity was linearly proportional to the surface area. (C) 2000 Elsevier Science Ltd. All rights reserved.