Eco-Friendly Zinc Adsorption in Textile Wastewater Using Pyrolyzed Coffee Waste

This study explores the utilization of coffee waste as a sustainable precursor for activated carbon to remove zinc (Zn) from textile wastewater. The activated carbon was produced via pyrolysis and chemically activated using KOH. The adsorption behavior was optimized using Response Surface Methodology (RSM), which identified the optimal activation parameters at 2.96 M KOH and 86.6 minutes of activation time. Under these conditions, the maximum Zn adsorption capacity reached 0.4986 mg/g, following the Langmuir isotherm model, indicating monolayer adsorption. Morphological analysis confirmed that KOH activation enlarged and increased pore density, directly enhancing adsorption efficiency. Compared with previously reported coffee-ground-based adsorbents, the optimized material exhibited higher Zn removal efficiency and better surface uniformity. The combination of RSM-based optimization, SEM characterization, and adsorption isotherm modeling represents a novel approach, demonstrating that waste coffee grounds can be effectively converted into high-performance adsorbents for heavy metal remediation.