Glycine based modification of activated carbons for VOCs adsorption

Abstract

Activated carbons (ACs) derived from coconut husk were modified by impregnating with glycine, a non-polar fatty amino acids. The effect of this modification method on the physicochemical characteristics of ACs and adsorption performance of VOC were investigated and compared with ammonia modification. TEM, SEM and BET were used to identify morphology and pore structure, XPS and elemental analysis were applied to analyze surface chemistry of the tested ACs. The adsorption performance of the selected VOC of toluene was tested using a fixed-bed reactor. The results show that the breakthrough adsorption capacity of toluene over 10 wt% glycine modified AC was about 147% and 139% higher than that of the original and 5 wt% ammonia modified ACs, respectively, while the saturated adsorption capacities of glycine modified ACs were less than that of 5 wt% ammonia modified AC. Glycine can be deposited on the surface of ACs and form polypeptide chains by self-condensation, which is favorable to increase the nitrogen-containing groups and reduce the surface polarity of ACs. While ammonia modification was more beneficial to improving the specific surface area and pore volume. Therefore, ammonia/glycine composite modification technology was proposed. The improved breakthrough and saturated adsorption capacities of toluene reached 75.02 mg/g and 451.48 mg/g, respectively.