Au and BM Concentrations in Leachates and Leaching Yields. Chemical analysis results of the Au and BM (Cu, Al, Ni, and Fe) concentrations in the leachates produced after each sequential leaching stage during the preparation of WPCB iodide leachate are presented in Table . show that after the final iodide leaching stage, 1.07 ± 0.009 g of Au reported into 2.0 L of WPCB iodide leachate, with Cu the only BM impurity which reported into in the WPCB iodide leachate, present in a concentration of 0.121 ± 0.001 g. Chemical analysis results of Au and BM leaching yields after each respective leaching stage are summarised in Table . These results show that the total Au leaching yield obtained after the preparation of the WPCB iodide leachate was 97.78 %. The high Au leaching yield observed following the preparation of the WPCB iodide leachate is comparable to the Au leaching yield observed by Batnasan et al. who used a similar conventional iodide lixiviant to leach Au from WPCBs at a >95 % yield . Results in Table also show that the BM leaching yields observed during the preparation of the WPCB iodide leachate (with cumulative yields ranging between 57.02 % to 78.56 %) are significantly lower than the WPCB BM leaching yields reported by previous authors who used either HNO3, HCl, or H2SO4-H2O2 lixiviants to leach BMs from WPCBs with >95 % yields , , , , . The lower BM leaching yields observed can be attributed to the high 500 g/L S/L ratio employed, which is significantly greater than the 100 g/L to 333 g/L S/L ratio employed by previous authors , , , , . Although the high 500 g/L S/L ratio employed resulted in less feasible BM leaching yields, a high Au leaching yield was observed at this S/L ratio. The high 500 g/L S/L ratio employed in this work is also supported by Yannopoulos who reported that Au is effectively leached at high S/L ratios between 350 g/L to 500 g/L in industrial operations . A higher S/L ratio can also be beneficial since it may result in a reduced leaching reactor size requirement and cost.