Six types of activated carbons were prepared from coffee residues by varying activating agents of zinc chloride, nitrogen, carbon dioxide
and steam. Characterization of these samples was performed by using nitrogen adsorption isotherms, thermogravimetric analysis (TGA),
scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) in order to understand the coffee residue activated
carbon and its adsorptive capacity. All of activated carbons and one commercial activated carbon (CH-I1000) were subjected to the adsorption
of formaldehyde vapor. The coffee activated carbon prepared with ZnCl2 impregnation and nitrogen activation (CZn N2) demonstrates its
highest capacity of formaldehyde adsorption owing to the hydrophilic functional groups of O H, C=O, C O on the surface. The coffee
activated carbon prepared with ZnCl2 impregnation coupled with carbon dioxide activation (CZn N2 CO2) yields the highest total surface
area (914 ± 21m2/g) and total pore volume (1.010 ± 0.003 cc/g) with the hydrophobic groups on the surface adsorbed formaldehyde less
than CZn N2. Therefore, we conclude that the formaldehyde adsorption by activated carbons in this work is affected by surface chemistry
more than texture characteristics of surface area and pore volume.