Valorization of oil palm fiber waste into mesoporous silica for selective removal of heavy metals from industrial wastewater

The increasing need for sustainable waste management and circular material use has encouraged research into converting agricultural residues into high-value functional materials. This study explores the valorization of oil palm fiber (OPF) waste for the production of mesoporous silica through sequential acid-alkali treatment and thermal calcination at 500 °C and 600 °C. The optimized silica synthesized at 600 °C exhibited a surface area of 138.3 m²/g and a pore diameter of 16.4 nm, indicating a mesoporous structure favorable for adsorption. Characterization using FTIR and XRF confirmed the presence of silanol and siloxane groups with low impurity levels. Adsorption performance was evaluated using industrial wastewater from silver processing, targeting copper (Cu²⁺) and silver (Ag⁺) removal. Results demonstrated high selectivity for Ag⁺, achieving 99.8% removal, while Cu²⁺ showed limited uptake. SEM–EDX mapping confirmed the presence and distribution of metal ions on the silica surface. This study highlights the potential of OPF-derived silica as a low-cost, eco-friendly adsorbent, contributing to both waste valorization and heavy metal remediation within a cleaner production framework. • Silica was synthesized from oil palm fiber waste through a sustainable thermochemical method. • FTIR analysis confirmed the presence of active functional groups: silanol (Si–OH) and siloxane (Si–O–Si) • Optimal calcination at 600°C produced mesoporous silica with 138.3 m²/g surface area and 16.4 nm pore size. • The silica showed excellent selectivity for Ag⁺ over Cu²⁺ in silver industrial wastewater. • Silver (Ag⁺) removal exceeded 99.8%, reducing concentration from 12.8 ppm to 0.013 ppm