Recycling waste aluminium foil to bio-acceptable nano photocatalysts [aluminium oxide (Al2O3) & aluminium oxyhydroxide (AlOOH)]; dye degradation as proof-of-concept

Abstract

The surge in the world's population resulting from urbanization and industrialization has led to a significant uptick in water and soil pollution. Aligned with the United Nations’ sustainable development goals, investigating innovative methods for repurposing waste into beneficial materials and effective catalysts that are compatible with ecosystems and capable of efficiently decomposing dyes is earnestly recommended. Additionally, in alignment with the objectives of a sustainable society, this study serves as a prototype for repurposing discarded aluminium foil—an everyday single-use material contributing to landfill accumulation—into aluminium oxide (Al₂O₃) and aluminium oxyhydroxide (AlOOH) nanocatalysts, intended for efficient photodegradation applications. Al₂O₃ and AlOOH nanosystems were synthesized using a well-optimized chemistry route. The developed nanosystems were characterized using FTIR, EDX mapping, XRD, FE-SEM, and TGA/DTA that found the bonds, composition, structure, morphology of the particles, and thermal stability, respectively. These particles were used for the degradation of cationic methylene blue (MB) dye in neutral (pH 7), basic (pH 9), and acidic (pH 5) mediums. Liquid chromatography mass spectrometry (LC-MS) was performed to check the MB intermediate product formation on photodegradation. The findings suggest that exposing cationic MB to light in neutral pH conditions with Al₂O₃ is highly effective, with a dye degradation rate of 99.29%. Exposing MB to the dark in neutral conditions with AlOOH is the least effective, with a dye degradation rate of 6.64%. As the pH is made more acidic and/or basic, the effectiveness of Al₂O₃ and AlOOH also slightly changes. The outcomes related to reusability and toxicity studies also proved the acceptability of the developed systems. Degradation using both compounds led to more germination when compared to MB, and both compounds showed outstanding reusability. The research emphasizes the importance of sustainable materials synthesis and offers valuable insights for the development of efficient photocatalysts tailored for specific environmental conditions in the context of dye degradation.