Valorisation of aluminum ash for catalytic applications: a review of activation strategies and sustainable remediation

Aluminum ash, an abundant byproduct of aluminum manufacturing, is enriched with aluminum oxide, metal oxides, carbon, and reactive phases that impart remarkable catalytic potential. Traditionally regarded as waste, it is now emerging as a versatile material for advanced catalytic processes, particularly in carbon dioxide reduction and wastewater remediation two critical challenges in sustainable development. This review provides a comprehensive and novel perspective, consolidating the catalytic applications of aluminum ash while critically evaluating performance-enhancement strategies such as thermal and chemical activation, doping-based surface modification, microwave-assisted activation, and hydrothermal synthesis. These approaches significantly improve its structural and chemical properties, enabling superior catalytic efficiency. Beyond technical insights, the review introduces a unique sustainability dimension, highlighting how aluminum ash valorisation promotes waste minimisation, resource recovery, and the transition towards a circular economy. By bridging catalytic science with sustainable practice, this work positions aluminum ash as an underexplored yet highly promising candidate for next-generation catalysts, capable of reducing dependence on virgin materials, lowering energy consumption, and enabling cleaner industrial operations. Ultimately, the study not only addresses existing research gaps but also provides fresh insights and future directions underscoring the novelty and significance of aluminum ash in advancing both catalysis and sustainability.