Surface modification of activated carbon for CO2 adsorption

Activated carbon was oxidized by an acid mixture of concentrated HNO3 and H2SO4 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 CO2 adsorption. The samples before and after the modification were characterized by N2 adsorption, elemental analysis, FT-IR and XPS. CO2 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 CO2 adsorption capacity. Surface basic nitrogen-containing functional groups on the modified sample, such as primary amino groups, are responsible for the increased adsorption. arbon Materials 2014, 29(2): 96–101]