OICC Press Anthropogenic Pollution 2588-4646 10 1 2026 06 30 Optimal Adsorption for High COD Reduction in Petrochemical Wastewater Using Pomegranate Peel– Silica Composites 10.57647/AP.2026.1001.03 EN Atefeh Barahimi Department of Environmental Sciences, Institute of Agriculture, Water, Food, and Nutraceuticals, Isf.C., Islamic Azad University, Isfahan, Iran Mozhgan Ahmadi Nadoushan Department of Environmental Sciences, Waste and Wastewater Research Center, Isf.C., Islamic Azad University, Isfahan, Iran Aliasghar Besalatpour Inter 3 GmbH - Institut für Ressourcenmanagement, Berlin, Germany Mitra Ataabadi Department of Soil Sciences, Institute of Agriculture, Water, Food, and Nutraceuticals, Isf.C., Islamic Azad University, Isfahan, Iran Journal Article 2026 06 30 Petrochemical industrial wastewater poses a significant environmental threat due to its high chemical oxygen demand (COD) and diverse pollutants, necessitating sustainable treatment solutions. Despite advances in adsorption, optimal conditions and mechanisms for multi-pollutant removal using composite adsorbents remain underexplored. This study evaluates the efficacy of pomegranate peel and silica-based adsorbents, in simple and composite forms with activated carbon, for removing COD, nitrate, sulfide, turbidity, total dissolved solids (TDS), total suspended solids (TSS), lead (Pb), and zinc (Zn) from PIW. Batch experiments tested organic, inorganic, and composite adsorbents at dosages of 2 and 4 g/L and contact times of 20, 40, and 60 minutes, with three repetitions. The composite adsorbent at 4 g/L and 60 minutes reduced COD by 62.0%, sulfide by 52.7%, Pb by 46.0%, and Zn by 39.8% across initial concentrations of 800–1200 mg/L, outperforming simple adsorbents. Pseudo-first-order kinetics (R² = 0.98, χ² = 0.02) and the Freundlich isotherm (R² = 0.95) models confirmed physical adsorption via van der Waals forces and multilayer binding. These findings position pomegranate peel–silica composites as effective, scalable solutions for mitigating PIW pollution through optimized multi-pollutant adsorption.