Efficient extraction of gold from model and real leach solutions using guanidinium ionic liquids

With the rapid development of modern industry, it is necessary to effectively recycle precious metals such as gold and palladium from e-waste. IL (ionic liquid) is an efficient extractant with high boiling points, non-flammability, and high thermal stability. The properties of IL can be improved by modifying the n-substituted groups of their cations, enhancing the separation efficiency of noble metals. Thus, two guanidinium ILs, with the substituents of -R and -OR, were synthesized to extract Au(III) from a HCl medium. These ILs exhibited excellent extraction properties, including high selectivities, rapid kinetics, and significant extraction capacities. The maximum extraction capacities of Au(III) by [diMTMG][Tf2N] and [diPTMG][Tf2N] were 519.4 mg/g and 427.9 mg/g, respectively, achieving rapid extraction equilibrium within 30 s. The introduction of O-containing functional atoms enhanced extraction capacity and selectivity. The extraction selectivity of the two ILs for real e-waste leachate was investigated in pure-ILs and diluent-involved systems, respectively. The results indicated that [diPTMG][Tf2N] showed excellent extraction of Au(III) from e-waste in both conditions.