Valorisation of alkaline effluent derived from iron ore upgrading by Calcium-aluminium-silicate-hydrate (CASH) production and in its application as an adsorbent for heavy metals (Cu2+ and Zn2+) removal from aqueous medium

• A process proposed for the valorisation of iron ore alkaline effluent. • Calcium aluminium silicate hydrate (C-A-S-H) was produced using a precipitation route. • The produced C-A-S-H product was a mesoporous material and applied as an adsorbent. • The product showed excellent adsorption behaviour towards Cu 2+ and Zn 2+ uptake. • Kinetic modelling of the adsorption fitted a pseudo-first-order equation. This study presents a route for valorising highly alkaline effluents generated during caustic soda leaching of low-grade iron ore, where dissolved sodium alumino-silicate species are typically considered a processing liability. By converting this challenging effluent into a mixture of predominantly calcium–aluminium–silicate–hydrate (CASH) phases, which follows hydrothermal zeolite recovery reported elsewhere, the study demonstrates that a post-zeolite waste stream with low (