Rapid removal of Cr(VI) from aqueous solution using polycationic/Di-metallic adsorbent synthesized using Fe3+/Al3+ recovered from real acid mine drainage

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Authors

Muedi, Khathutshelo Lilith
Masindi, Vhahangwele
Maree, Johannes Philippus
Brink, Hendrik Gideon

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MDPI

Abstract

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

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DATA AVAILABILTY : The data presented in this study are openly available in the University of Pretoria Research Data Repository at https://doi.org/10.25403/UPresearchdata.21342765.

Keywords

Chromium removal, Acid mine drainage, Wastewater streams, Circular economy, Wastewater beneficiation, Polycationic/di-metallic adsorbent (nanocomposite)

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Citation

Muedi, K.L.; Masindi, V.; Maree, J.P.; Brink, H.G. Rapid Removal of Cr(VI) from Aqueous Solution Using Polycationic/ Di-Metallic Adsorbent Synthesized Using Fe3+/Al3+ Recovered from Real Acid Mine Drainage. Minerals 2022, 12, 1318. https://DOI.org/10.3390/min12101318.