Separation and recovery of iridium(IV) from simulated secondary resource leachate by extraction - electrodeposition

Abstract

In this work, a novel extraction–electrodeposition process is employed to separate and recover Ir(IV) from a multi-metal mixed solution comprising Ir(IV), Pt(IV), Fe3+, Al3+, Cu2+, Mg2+, and Ca2+. The mixed ionic liquid ([EBTOA]Br/[Bmim]PF6) can efficiently separate Pt(IV) from Ir(III) once Ir(IV) has been reduced to Ir(III). The separation coefficient of βPt(IV)/Ir(III) was higher than 1.0 × 104. Following Pt(IV) extraction, 30% (w/w) H2O2 was added to the extraction raffinate to oxidize Ir(III) to Ir(IV). The same mixed ILs system was adopted to select IV ely extract Ir(IV) from the extraction raffinate. The electrochemical window of mixed ILs and the optimum Ir(IV) deposition voltage are investigated using cyclic voltammetry (CV). Ir(IV) can be reduced to Ir(0) at an optimal potential voltage of −1.72 V using [EBTOA]Br-Ir(IV)/[Bmim]PF6 as an electrolyte. SEM-EDS, TEM, and XPS analysis demonstrate that a black coating of iridium metal has been deposited on the copper surface. In addition to its excellent extraction efficiency, the proposed method offers low volatility and good stability. Furthermore, DFT calculations have been used to examine the platinum and iridium separation mechanism, as well as to determine the key factors affecting extraction, including bond length, charge density, molecular polarity, and electrostatic potential. The electrostatic potential surface models indicate that the [EBTOA]Br/[Bmim]PF6 system is not capable of extracting Ir(III). This technique has enormous potential for separating and recovering iridium from wasted catalyst leaching liquor.