Efficient extraction of gold from e-waste using functional guanidinium ionic liquids

Abstract

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 hydrochloric acid 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 519.4mg/g and 427.9mg/g, respectively, achieving rapid extraction equilibrium within 30s. The introduction of o-containing functional atoms enhanced extraction capacity and selectivity. The extraction mechanism involving anion exchange was confirmed by slope method, jobs method, as well as ultraviolet and nuclear magnetic resonance analysis.