The adsorptive properties of carbonised olive stones

Abstract

Olive stones were carbonised to 1120°K and activated in carbon dioxide at 1100°K to 20% burn-off. Adsorptive properties were measured by adsorption of nitrogen (77°K) and carbon dioxide (195°K, 273°K) using the Langmuir and Dubinin equations of adsorption to deduce effective surface areas. The extents of development, with activation of meso- and macro-porosity were monitored by mercury porosimetry; the surface textures of the parent olive stones, and carbonised and activated products were described by scanning electron microscopy. The carbonised stones had a surface area of 500 k(m) 2 kg −1 in microporosity increasing to 1500 k(m) 2 kg −1 at twenty per cent burn-off. This sample had a micropore volume of 600 cm 3 kg −1 and 600 cm 3 kg −1 in the meso- and macro-porosity. The activation process did not occur evenly, but selectivity. There was no strong evidence for catalytic initiation of the selective gasification. The activated carbons were pseudomorphs of the parent olive stones and did not abraid easily. Their purity (0·21% ash) and low sulphur content (less than 0·1%) may make these active carbons commercially attractive.