Mechanism of gold (III) extraction using a novel ionic liquid-based aqueous two phase system without additional extractants

• A novel ionic liquid, 1-hexyl-3-methyl imidazole dodecyl sulfonate, was synthesized.
• [C6mim][C12SO3]/PEG6000 aqueous two phase system was applied for gold extraction.
• The ion-exchange mechanism of above was analyzed by UV–vis and FT-IR spectra first.

In our work, the imidazolium ionic liquid-based aqueous two phase system was applied for gold (III) extraction for the first time. A novel ionic liquid, 1-hexyl-3-methyl imidazole dodecyl sulfonate ([C6mim][C12SO3]), was synthesized and used for the construction of an aqueous two phase system together with PEG6000 which was investigated for Au (III) extraction later. The [C6mim][C12SO3] acted as a component of the aqueous two phase system as well as the gold (III) extractant. To optimize the process, the influence of several experimental parameters, namely the vibration time, the pH of the PEG stock solution, initial gold (III) concentration, the PEG molecular weight, was studied in the extraction process. Then, the ion-exchange mechanism of gold (III) extraction was discussed in the process. It demonstrated that the [C6mim][C12SO3]/PEG6000 aqueous two phase system would be a promising and potential approach for gold (III) extraction and separation in acid solutions.