Investigation of enhanced gas absorption by adsorptive bucky balls in a multiphase slurry reactor in the presence and absence of ultrasound

Fullerenes (e.g., bucky balls) constitute a fascinating class of novel materials, which have shown very high adsorption capacities for hydrogen (5-10 wt % at pressures of less than 1 bar near room temperature by the single-wall nanotubes) under gas-solid conditions. In this work, hydrogen absorption in aqueous slurries of bucky balls has been investigated in a flat stirred cell under slurry conditions at different solid loadings in the presence and in the absence of ultrasound. Enhancements in the gas absorption up to 2.4 were observed using suspended bucky balls. Further enhancements could be obtained by application of ultrasound during the experiment or by presonication of the slurry. Gas absorption rates are a strong function of the solid loading and the stirrer speed. The performance of the bucky balls was compared to that of activated carbon. Bucky balls showed a higher adsorption capacity for H-2 than activated carbon. The increase in the gas absorption in the presence and in the absence of ultrasound was theoretically analyzed using the enhanced gas absorption model. Good agreement between observed and theoretical enhancement factors was obtained.