Recycled aluminum foil waste-derived nano-aluminum oxide adsorbent: an eco-friendly solution for treating phenolic wastewater

Abstract

This study explored the potential of repurposing domestic foil waste to synthesize nano-aluminum oxide (nano-γ-Al2O3) for effective phenol removal from wastewater. The synthesized nano-aluminum oxide was comprehensively characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray (EDX) spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, and Fourier-transform Infrared Spectroscopy (FTIR). Characterization revealed functional groups including C = O, C–H, C–O, O–H, and C–C, which facilitate phenol adsorption on the material surface. Batch studies evaluated factors such as initial phenol concentration, pH, temperature, and desorption efficiency. Optimal phenol removal was achieved at pH 8.0 with a maximum adsorption capacity (qmax) of 48.54 mg/g at 35 °C. The thermodynamic analysis indicated a spontaneous and exothermic adsorption process, with ΔH° of -77.6 kJ/mol and ΔS° of 232.2 J/mol·K. The adsorption was attributed to non-covalent interactions between the highest occupied molecular orbital (HOMO) of phenol and the lowest unoccupied molecular orbital (LUMO) of nano-γ-Al2O3. In addition, the adsorbent demonstrated effective regeneration using NaOH and effectively removed phenol in real wastewater samples. These findings highlight the potential of waste-derived nano-adsorbents as sustainable solutions for wastewater treatment.