Synthesis of Vegetable-Based Activated Carbons with Mixed Micro- and Mesoporosity for Use in Cigarette Filters

Activated carbons with micropores for adsorption and filtration of the volatile constituents of mainstream cigarette smoke, together with mesopores for enhanced mass transport were prepared by a novel route. Treatment of coconut shell or other lignocellulosic precursors with aqueous NaOH, followed by thorough washing, charring and steam activation produced carbons with enhanced adsorption characteristics in smoking trials, compared with their microporous analogues. The mechanism of formation of these carbons is explained in terms of initial partial dissolution of the precursor in an aqueous alkali solution, followed by catalytic gasification of carbon in steam involving residual sodium.