The Preparation and Characterization of Activated Carbon from Coffee Residue

Coffee residues from instant coffee plants were used to produce mesoporous activated carbon. A series of carbonization and activation conditions were examined to elucidate the effect of each condition. The specific surface area, mesopore and total pore volumes were evaluated by nitrogen adsorption at 77 K, and the surface chemistry was characterized by FTIR. The activated carbon derived in the conditions of a ZnCl2/coffee weight ratio of 3, an activation temperature of 600°C and a CO2 activation time of 4 h (R30T600H4) yielded a surface area of 900 m2/g, a total pore volume of 1.01 cm3/g with a mesopore content of 92%. The FTIR results demonstrated that the C–H group was the main functional group on the surface of coffee-derived activated carbon. The adsorptive capacities of R30T600H4 compared with a commercial activated carbon CAL for phenol, methylene blue and erythrosine red. We found that for small molecules such as phenol and methylene blue the adsorption capacity of R30T600H4 was lower than that of CAL, whereas, for larger molecules such as erythrosine red R30T600H4 was higher. The mesoporous structure and the surface chemistry of coffee-derived activated carbon associated in the adsorption were discussed.