Impregnation of Chitosan onto Activated Carbon for High Adsorption Selectivity towards CO2: CO2 Capture from Biohydrogen, Biogas and Flue Gas

Abstract

In this study, a novel bio-based adsorbent was developed for CO2 adsorption. Palm shell activated carbons were immersed in chitosan solutions at the concentrations between 0.1-2 g/L under agitation. A series of chitosan impregnated activated carbon was obtained: 0.12-0.98 wt% chitosan. The chitosan impregnated activated carbon that was the most suitable for CO2/H2 separation was the one impregnated with 0.1 g/L chitosan solution yielding 0.12 g chitosan per one hundred gram activated carbon. A lab-scale pressure swing adsorption process using the modified activated carbon as the adsorbent (adsorption pressure of 4 bar and the feed flowrate of 2 L/min 50-50 mixture of H2 and CO2 for a period of 2 min) yielded ultra pure H2 for 8 cycles before the breakthrough of CO2, while only 3 cycles were achieved with the native activated carbon. The chitosan impregnated activated carbon that was the most suitable for CO2/CH4 separation was the one impregnated with 2 g/L chitosan solution yielding 0.76 g chitosan per one hundred gram activated carbon. The lab-scale adsorption process using the modified activated carbon as the adsorbent yielded ultra pure CH4 for 3 cycles before the breakthrough of CO2, while only 1 cycle was achieved with the native activated carbon. For the CO2/N2 dynamic adsorption of 0.12 wt% CHI/AC, 100% nitrogen was achieved for 1-8 cycles. For the CO2/N2 dynamic adsorption of 0.76 wt% CHI/AC, 100% nitrogen was achieved for 1-9 cycles.