Synergistic adsorption–photocatalytic degradation of water pollutants using sustainable activated carbon/ZIF-67 hybrid nanocomposites

In this work, an efficient hybrid composite was prepared by integrating Zeolitic Imidazolate Framework-67 (ZIF-67) nanoparticles onto activated carbon (AC) derived from palm petiole, an abundant renewable agricultural waste, through a simple and sustainable impregnation method. The resulting AC-ZIF-67 architecture promotes close contact between the ZIF-67 phase and the carbonaceous support, which may partially shield the framework under acidic conditions. A composition containing 60 wt.% ZIF-67 and 40 wt.% AC was selected for this study. The composite was evaluated for the removal of the anionic dye Acid Green 25 (AG25) and persistent pharmaceutical pollutants, including ciprofloxacin (CIP), diclofenac (DCF), and naproxen (NPX), under visible light irradiation.The AC-ZIF-67 hybrid showed remarkable adsorptive performance, reaching a maximum AG25 adsorption capacity of 235 mg·g⁻¹ at pH 2, almost twice that of pristine AC. This acidic stress condition was used to assess the stabilizing role of AC, which may physically hinder hydronium ion attack on the ZIF-67 framework. Adsorption data followed the Langmuir isotherm and pseudo-second-order kinetics, suggesting monolayer adsorption dominated by strong surface interactions. Beyond adsorption, the hybrid achieved 90% removal of AG25 within 60 min. Mechanistic results support an “adsorb-and-shuttle” pathway, where AC concentrates pollutants near ZIF-67 photoactive sites. Under visible light irradiation (λ > 420 nm) at pH 6, the composite also achieved elimination efficiencies of 95% for ciprofloxacin, 80% for diclofenac, and 25% for naproxen, demonstrating its effectiveness toward different classes of pharmaceutical contaminants. Furthermore, the AC-ZIF-67 composite maintained high photocatalytic activity after successive reuse cycles, supporting its operational reusability and practical potential as a sustainable biomass-derived material for wastewater treatment. The integration of ZIF-67 with low-cost biomass-derived activated carbon not only creates a synergistic adsorption–photocatalytic system but also reduces the overall reliance on the more expensive MOF component, improving the economic feasibility and scalability of the composite for large-scale wastewater treatment applications.