Behavior, mechanism and equilibrium studies of Au(iii) extraction with an ionic liquid [C-4-6-C(4)BIm]Br-2

摘要

The first gemini-type benzimidazole ionic liquid ([C-4-6-C(4)BIm]Br-2) with two sites of action was synthesized and applied for gold extraction. The effects of [C-4-6-C(4)BIm]Br-2 concentration, initial gold(iii) concentration, acidity, and the loading capacity of [C-4-6-C(4)BIm]Br-2 were examined in detail. It was found that [C-4-6-C(4)BIm]Br-2 has excellent extraction ability for obtaining high purity gold. The anion exchange mechanism between [C-4-6-C(4)BIm]Br-2 and Au(iii) was proved by Job's method and H-1 NMR and FTIR spectroscopy. Quantum chemical calculations were carried out to prove the mechanism theoretically. The extraction equilibrium process was modeled using Langmuir and Freundlich isotherms. Thermodynamic parameters Delta H, Delta G and Delta S indicated that the extraction process was exothermic and spontaneous. The pseudo-second-order kinetic model well fitted the experimental data (R = 0.99). In addition, [C-4-6-C(4)BIm]Br-2 has high selectivity for Au(iii) compared to other base metals. In summary, [C-4-6-C(4)BIm]Br-2 has great application prospects in industry due to its excellent characteristics such as low cost, easy availability, and high extraction capacity.