Surface modification of activated carbon for CO2 adsorption

Activated carbon was oxidized by an acid mixture of concentrated HNO 3 and H 2 SO 4 with a volume ratio of 1:1 diluted with the same volume of de-ionized water, followed by reduction with iron dust to modify its surface chemical properties for CO 2 adsorption. The samples before and after the modification were characterized by N 2 adsorption, elemental analysis, FT-IR and XPS. CO 2 adsorption properties of the samples were investigated by high pressure adsorption. It was found that the adsorption capacities of the modified sample were 17.72 and 14.01 mmol/g at room temperature and 319.15 K respectively, showing an increase of 49% and 70% respectively, based on the surface area of the samples. The modified activated carbon can be recycled 4 times at ambient conditions without a significant decrease in CO 2 adsorption capacity. Surface basic nitrogen-containing functional groups on the modified sample, such as primary amino groups, are responsible for the increased adsorption. [New Carbon Materials 2014, 29(2): 96–101]