Impregnation of Chitosan onto Activated Carbon for Adsorption Selectivity Towards CO2: Biohydrogen Purification

Abstract

In this study, a novel bio-based adsorbent was developed for biohydrogen purification by an adsorption process. Palm shell activated carbons were immersed in the chitosan solutions at the concentrations between 0.1-2 g/L.The results showed that the impregnation of chitosan onto activated carbons at every concentration under the investigation changed the BET surface areas, pore size distribution, CO₂ adsorption capacity and the CO₂/H₂ selectivity. The chitosan impregnated activated carbon that was the most suitable for carbon dioxide/hydrogen separation was the one impregnated in the 0.1 g/L chitosan solution yielding 0.12 g chitosan per 100 gram activated carbon. The modified activated carbon was found to have 11% higher CO₂ adsorption capacity than the native activated carbon even though its BET surface area was reduced by 3% due to the impregnation process. From a lab-scale pressure swing adsorption process using the modified activated carbon as the adsorbent (under an adsorption pressure of 4 bar and the feed flow rate of 2 L/min 50-30-20 mixture of CO₂, H₂ and N₂ for a period of 2 min per cycle), the CO₂ concentration in the effluent was not detected for at least 5 cycles.