LAUSR

Abstract Economies of many countries around the world have been improved by the mining of precious elements such as gold and platinum group elements (PGEs). As such, the demand for these elements has increased over the years, which led to increased rate of mining. However, the resources and reserves of these elements have been reduced as a result. The alarming rate of mining indicates a need for secondary sources for precious elements. This study was aimed at using a cheap and efficient spent brewer’s yeast-functionalised zeolite to recover Pd(II), Ir(III) and Rh(III) from aqueous solutions. The solutions represent industrial wastewaters which normally contain PGEs which were lost during processing. The adsorbent bed height, solution pH, initial concentration and flow rate were optimised to obtain the best working conditions of the adsorbent. The bed depth service time, Adams-Bohart, Thomas, Yoon-Nelson, Clark column, Wolborska and modified dose response models were used to evaluate the dynamic behaviour of the column. The maximum recovery was achieved at longer bed height, low concentration (2 mg L−1) and low flow rate (2 mL min−1). The speciation of the elements at different conditions motivated the recovery outcome. For example, the dominant species Pd(II) and Ir(III) were negatively charged at highly acidic pH hence, their uptake was favoured by the positively charged surface but, the uptake of Rh(III) was not favoured at these conditions since, [RhCl(H2O)5]2+ and [RhCl2(H2O)4]+ were dominant and thus, repelled by the adsorbent. The success of the recovery of Pd(II), Ir(III) and Rh(III) from aqueous solutions makes the adsorbent a potential recovery agent in the PGEs mining industrial wastewater.