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Published on: March 24, 2018
Behavior, mechanism and equilibrium studies of Au(iii) extraction with an ionic liquid [C4-6-C4BIm]Br2
Hongmei Su1, Qi Wang, Ning Wang
1Key Laboratory for Special Functional Aggregate Materials of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, China. yzhyang@sdu.edu.cn.
Abstract:
The first gemini-type benzimidazole ionic liquid ([C4-6-C4BIm]Br2) with two sites of action was synthesized and applied for gold extraction. The effects of [C4-6-C4BIm]Br2 concentration, initial gold(iii) concentration, acidity, and the loading capacity of [C4-6-C4BIm]Br2 were examined in detail. It was found that [C4-6-C4BIm]Br2 has excellent extraction ability for obtaining high purity gold. The anion exchange mechanism between [C4-6-C4BIm]Br2 and Au(iii) was proved by Job's method and 1H 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 ΔH, ΔG and ΔS 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, [C4-6-C4BIm]Br2 has high selectivity for Au(iii) compared to other base metals. In summary, [C4-6-C4BIm]Br2 has great application prospects in industry due to its excellent characteristics such as low cost, easy availability, and high extraction capacity.
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