Activated carbon prepared from coffee pulp: potential adsorbent of organic contaminants in aqueous solution

The processing of coffee beans generates large amounts of solid and liquid residues. The solid residues (pulp, husk and parchment) represent a serious environmental problem and do not have an adequate disposal mechanism. In this work, activated carbons (ACs) for adsorption of organic compounds were prepared from coffee pulp by controlled temperature at different pulp/Na₂HPO₄ ratios (4:1, 2:1, 5:4 and 1:1). The N₂ adsorption/desorption isotherms showed ACs with high quantities of mesopores and micropores and specific surface areas of 140, 150, 450 and 440 m²g⁻¹ for AC 4:1, AC 2:1, AC 5:4 and AC 1:1, respectively. The prepared material AC 5:4 showed a higher removal capacity of the organic contaminants methylene blue (MB), direct red (DR) and phenol than did a Merck AC. The maximum capacities for this AC are approximately 150, 120 and 120 mg g⁻¹ for MB, DR and phenol, respectively. Thus, a good adsorbent was obtained from coffee pulp, an abundant Brazilian residue.