Rapid Removal of Cr(VI) from Aqueous Solution Using Polycationic/Di-Metallic Adsorbent Synthesized Using Fe3+/Al3+ Recovered from Real Acid Mine Drainage

The mining of valuable minerals from wastewater streams is attractive as it promotes a circular economy, beneficiation, and valorisation. To this end, the current study evaluated rapid removal aqueous Cr(VI) by polycationic/di-metallic Fe/Al (PDFe/Al) adsorbent recovered real acid mine drainage (AMD). Optimal conditions for were 50 mg/L initial Cr(VI), 3 g PDFe/Al, pH = 3, 180 min equilibration time temperature 45 °C. resulted in ≥95% maximum adsorption capacity Q 6.90 mg/g. Adsorption kinetics followed two-phase pseudo-first-order behaviour, i.e., fast (likely due to adsorption) slower secondary Cr(III) reduction on surface). More than 90% adsorbed could be after five adsorption–desorption cycles. A reaction mechanism involving onto at least two distinct surfaces situ reduction, well adsorption-induced internal surface strains consequent area magnification, was proposed. This demonstrated rapid, effective, economical application PDFe/Al bona fide AMD treat Cr(VI)-contaminated wastewater.