Adsorption characteristics of activated carbon prepared from spent ground coffee

This paper reports results of a research project which attempts to produce low-cost activated carbon from agro-residue wastes. The ground coffee residue which is a by-product of coffee making was collected from coffee shops, prepared, and converted to activated carbon by a chemical activation method. The objective of this work is to investigate the effects of preparation conditions on properties of the activated carbon obtained. The preparation condition is defined by pyrolysis rate, concentration of ZnCl₂, impregnation time, and carbonization temperature. The pyrolysis rate was fixed at 10 °C min⁻¹ for 4 h with three concentrations of ZnCl₂ (5, 10, and 15 wt%), three durations of impregnation time (8, 12, and 24 h), and three carbonization temperatures (400, 450, and 500 °C). The morphology and specific surface area were, respectively, determined using SEM and BET techniques. It was found in this study that the activated carbon with the best properties was obtained at the preparation condition given by 15 wt% of ZnCl₂, impregnation time of 24 h, and 500 °C carbonization temperature. On average, the activated carbon had a pore diameter of 0.61 nm, specific surface area of 831 m² g⁻¹, and a total pore volume of 0.44 cm³ g⁻¹. It was also found that the adsorption isotherm of Cu (II) fitted well with Freundlich isotherm.