Adsorption of sulphur dioxide onto activated carbon prepared from oil-palm shells with and without pre-impregnation

Adsorption of sulphur dioxide (SO₂), a common gaseous pollutant, on oil-palm-shell activated carbon in a fixed bed was studied in this paper. Oil-palm shell is an abundant agricultural solid waste in tropical countries like Malaysia and Thailand. The effects of fixed-bed length, SO₂ gas superficial velocity, adsorbent particle size and internal pore structure on fixed-bed performance were investigated. Some characteristic parameters such as the breakthrough time, τ_0.05, exhaustion time, τ_0.95, length of mass transfer zone, L_MTZ, adsorptive capacity, W, and adsorption rate constant, K, were derived from the breakthrough curves. Tests of SO₂ adsorption onto activated carbons prepared from oil-palm shells pre-impregnated with potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) of different concentrations were also carried out. It was found that the fixed-bed performance was not only dependent on the operating conditions and the textural properties of the adsorbent but was also influenced by the surface chemistry of the adsorbent, which was related to the type and concentration of the impregnating agent. In general, the quality of oil-palm-shell activated carbon prepared by CO₂ activation is comparable to that of a commercial product, and the samples prepared from oil-palm shell with KOH pre-impregnation are more suitable for the removal of SO₂ gas.