Innovative engineering of α-Al2O3 from recycled aluminum: A functional material for cadmium removal and environmental remediation

Abstract

Water pollution, driven by anthropogenic activities, is a global environmental concern, particularly due to heavy metal contamination. Sustainable solutions are urgently needed to address this issue. This study reports the synthesis of monolithic α-Al2O3 adsorbents derived from recycled aluminum cans via acid dilution and sol–gel methods for Cd2+ removal. Sintering at 1600 °C yielded α-Al2O3 monoliths with 40 nm crystallite size and 97% phase purity. Physicochemical characterization revealed 0.204 meq g−1 acid sites, an isoelectric point at pH 2, and a zeta potential of − 50 mV at pH 5, confirming favorable electrostatic adsorption of Cd2+. The adsorbent exhibited a maximum capacity of 2.2 mg g−1, effectively removing Cd2+ from aqueous solutions. Adsorption mechanisms followed the Freundlich isotherm indicating heterogeneous surface sites, and the Elovich kinetic model suggesting strong adsorbate–adsorbent interactions. These results demonstrate the potential of recycled aluminum cans as a low-cost source for high-performance α-Al2O3 adsorbents, contributing to sustainable water remediation strategies.