DOI: https://doi.org/10.55373/mjchem.v27i6.1

Keywords: Coffee grounds; activated carbon; zinc, adsorption; wastewater treatment

Abstract

Heavy metals are still a problem in aquatic systems; for example, Zinc represents environmental and health risks due to its toxicity, persistence, and bio-accumulative character. This work focuses on a sustainable and cost-effective approach for the elimination of Zinc by activated carbon derived from coffee grounds (ACCG). The ACCG was chemically activated by phosphoric acid, which greatly improved its surface reactivity and porosity. The physicochemical characterization supports this by revealing a high specific surface area (421 m²/g), a pore volume of 0.35 cm³/g and the presence of functional groups (-COOH, -OH) favoring adsorption. The adsorption experiments achieved a maximum efficiency of 99.8% under optimal conditions. Kinetic studies have shown that the adsorption follows a pseudo-second order model, suggesting chemisorption dominance. The analysis of adsorption isotherms showed that the Langmuir model offers the best fit, indicating monomolecular adsorption on a homogeneous surface. Regeneration studies showed that ACCG maintained its effectiveness over three cycles before its performance gradually decreased, as observed in desorption experiments. These results confirm that ACCG is an economical and environmentally friendly adsorbent, making it a promising material for wastewater treatment and the removal of Zinc ions.