Reactivity of Cork and Lignin for the Production of Activated Carbons

Abstract:

Activated carbons have been prepared by physical activation in CO2 of commercial byproduct kraft lignin (as received, after de-ashing and after impregnation with NaCl) and natural cork. The results obtained show that the presence of natural inorganic impurities increases the reactivity of cork and lignin significantly and also results in limiting values for the micropore volume and in widening of the micropore size. Pure de-ashed lignin is exceptionally non-reactive but allows microporous activated carbons to be obtained which have very narrow micropore widths of ~0.5-0.6nm. When the de-ashed lignin is impregnated with NaCl similar micropore volumes and widths can be obtained but in a considerably shorter time (~30min instead of ~8h) which would result in a considerable energy saving and is therefore a promising procedure for the production of microporous activated carbons from low-cost kraft lignin.