Textural and chemical characterisations of activated carbon prepared from oil-palm stone with H2SO4 and KOH impregnation

Textural and chemical characterisations of the activated carbon prepared from oil-palm stone, an abundant tropical solid waste, by pre-treatment with H2SO4 and KOH impregnations were carried out in this study. The effects of impregnations concentration and soaking time on the textural properties, such as adsorption isotherm, porosity, surface area and pore size distribution were investigated. A reasonably high BET surface area and predominant microporosity of the oil-palm stone carbons suggested their potential applications in gas-adsorbing processes. From adsorption tests of SO2 and NH3, it was found that the activated carbons pre-treated with KOH could adsorb more SO2 but less NH3 than those pre-treated with H2SO4, even though they had almost identical BET and micropore surface areas. This indicated that the adsorptive capacity of the activated carbon was not only determined by its textural characteristics, but also related to the surface chemistry. Chemical characterisation showed that impregnation affected significantly the surface chemistry, i.e. inorganic component and surface organic functional group. For organic functional groups, the samples pre-treated with H2SO4 presented acidic groups such as phenols and carboxylic acids, whereas those with KOH impregnation showed alkaline groups suggested to be pyrones (cyclic ketone) and other keto-derivatives of pyran. In general, the activated carbons prepared from oil-palm stones with impregnation of KOH and H2SO4 are suitable for use as gas-phase adsorbents for the removal of acidic and alkaline gases, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.