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 wast es generated from palm-oil processing mills. Experimental results showed th at the particle size of the starting material and heating rate appeared to have no significant effects on the BET surface areas of the activated carbo ns but CO2 flow-rate had a significant influence. Increasing the heating ra te resulted in slight reductions in the micropore surface areas. The BET an d micropore surface areas of the activated carbons were also found to be de pendent on the activation temperature and the hold time. The optimum condit ions 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 foun d to be maximum at 1410 and 942 m(2) g(-1) respectively. The pore size dist ributions of the activated carbon also confirmed these conditions. The deve lopment of microporosities in these activated carbons suggest their potenti al applications in gaseous pollutant adsorption. From chemical characterisa tion, the activation temperature was found to have an insignificant effect on the inorganic components of the activated carbons but possible effects o n their surface functional groups. The amounts of NO2 adsorbed onto the oil -palm-stone activated carbons and a commercial one were measured during ads orption tests. The relationship between the amount of gas adsorbed and the BET surface area of the activated carbon indicated that the adsorptive capa city was linearly proportional to the surface area. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.