Waste-to-zeolite pathways for industrial residue valorization, material flow integration, and end-of-waste considerations

Waste-derived zeolite synthesis is increasingly proposed as a route for converting large-scale residues into functional sorbents, ion exchangers, and catalysts. This review evaluates the conversion pathways as material-cycle processes rather than only as synthesis recipes. The literature is organised through a feedstock-synthesis-performance framework that links residue chemistry, mineralogy, reactive silicon and aluminium availability, impurity burden, conditioning route, zeolite framework outcome, application performance, and deployment constraints. The evidence shows that the bulk silicon and aluminium contents alone are insufficient predictors of zeolite formation, as reactive species may be locked in quartz, mullite, feldspar, talc, gehlenite, or calcium-bearing phases. Therefore, route selection must consider activation demand, alkali consumption, water use, solid-liquid separation, liquor recycle, residue fate, and product qualification. Quantitative comparisons showed that waste-derived zeolite routes can deliver useful adsorption, ion-exchange, and catalytic performance. However, sustainability claims depend on normalised inventories, product specifications, techno-economic analysis, life-cycle assessment, regeneration behaviour, and leachability. Future studies should prioritise pilot-scale mass balances, closed-loop reagent recovery, wastewater management, shaped-product performance, and application-specific release criteria.