Adsorption of sulfur dioxide on activated carbon from oil-palm waste

Adsorption of sulfur dioxide (SO2) onto activated carbons prepared from oil-palm shells was investigated in this paper. Experimental results showed that the adsorption temperature and SO2 concentration significantly determined the amount of SO2 adsorbed and the equilibrium time. However, sample particle size had minimum effect on the equilibrium time. For a fixed SO2 concentration, the adsorption rate and adsorption kinetic parameters (activation energy and frequency factor) were obtained. A linearly proportional relationship between the Brunauer-Emmett-Teller surface area and the adsorptive capacity of the activated carbon from oil-palm shells was observed. An intraparticle Knudsen diffusion model based on a Freundlich isotherm was developed for predicting the amount of SO2 adsorbed and the SO2 concentration profile within the particle. Based on the estimated isotherm parameters and diffusion coefficients by experimental data fitting, this model could predict the amount adsorbed under different concentrations very well. However, this model was unsuitable for the activated carbon prepared from oil-palm shells by chemical activation because of the occurrence of chemisorption, which was related to the nature of the sample surface functional groups.