Recovery of gadolinium ions based on supported ionic liquid membrane: parametric optimization via central composite design approach

Gadolinium is a contrast agent in magnetic resonance imaging, and the extraction and purification process has been very much considered due to the importance of its applications. The transport of gadolinium ions was investigated by utilizing the supported liquid membrane with mixtures of extractants as a carrier. The systematic conditions of the process were optimized based on the experimental design approach. At the first time, the effect of mixing of two extractants such as di-(2-ethylhexyl) phosphoric acid, tributyl phosphate extractants and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as a green environmental solvent was studied on the gadolinium ion transport and the optimal concentration was utilized in the preparation of carrier concentration. In the second time, the main variables such as reaction time, the concentration of gadolinium ions, acidity in the source and stripping phases were optimized equal to 6 h, 200 mg/L, 5 and 1.86 M, respectively. The permeability coefficients were calculated based on the predicted equation for the transport percent of gadolinium ions, and the results were in agreement with the calculated values from the experimental data (coefficient of determination equal to 0.959). Finally, the applicability of gadolinium extraction through the supported liquid membrane was confirmed in the process with the presence of ionic liquids.