Removal of platinum (IV) from aqueous solutions with yeast- functionalised bentonite Alseno K. Mosai * , Luke Chimuka, Ewa M. Cukrowska, Izak A. Kotz  e, Hlanganani Tutu ** Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag X3, WITS, 2050, South Africa highlights graphical abstract  Pt(IV) lost during processing can become quite significant in the environment.  Yeast (rich in amine) from brewing waste can be used to functionalise bentonite.  Yeast-functionalised bentonite was used to recover Pt(IV) from aqueous solutions.  Pt(IV) was significantly recovered (>95%) by the adsorbent at pH 2 within 90 min.  Adsorption of Pt(IV) was still >95% in the presence of competing ions (incl. PGMs). article info Article history: Received 28 January 2019 Received in revised form 27 August 2019 Accepted 4 September 2019 Available online 5 September 2019 Handling Editor: Martine Leermakers Keywords: Brewer's yeast Platinum group metals Pt(IV) removal Adsorption efficiency Cost-benefit analysis abstract There is a need for cheap but, efficient methods for the removal of precious metals from wastewaters, which are normally lost during mineral processing. Moreover, the disposal of yeast waste from brewing has been a problem in many parts of the world. In this study, the removal of Pt(IV) from aqueous so- lutions using the readily available bentonite clay functionalised with spent yeast from brewing was investigated. The maximum adsorption capacity of Pt(IV) with 100 mg yeast-functionalised bentonite at pH 2 within 90 min was 255 mgg 1 (98.5% efficiency) but, decreased as pH increased. The adsorption capacity of Pt(IV) was insignificantly (p > 0.05) affected by the presence of competing ions (Fe(III), Ca(II), Mg(II), K(I), Co(II) , Ni(II), Hf(IV), Zn(II) and other platinum group metals (PGMs)). Moreover, most of these metals were significantly adsorbed along with Pt(IV). The indicative cost-benefit analysis showed that 1 kg of the yeast-functionalised bentonite can remove ~700 g Pt(IV) in which a profit of more than USD20000 can be made. The bentonite functionalised with spent yeast from brewing has a potential to recover lost PGMs in wastewater. Since, this is a cheap process, the mining and other industries can make much profit from such recoveries. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The waste produced from mineral processing can contain sig- nificant amount of minerals including valuable or precious metals such as platinum, gold and palladium (Rankin, 2011). Moreover, the amount of waste produced has been increasing over the years due * Corresponding author. ** Corresponding author. E-mail addresses: mosai.alseno32@gmail.com (A.K. Mosai), hlanganani.tutu@ wits.ac.za (H. Tutu). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2019.124768 0045-6535/© 2019 Elsevier Ltd. All rights reserved. Chemosphere 239 (2020) 124768