New Surfactant for Gallium and Aluminum Extraction by Microemulsion

A new surfactant, 12-(N,N-diethylamino)-9,10-dihydroxyoctadecanoate, synthesized from castor oil, was used in microemulsified systems to separate gallium and aluminum from a synthetic Bayer liquor. The extraction/re-extraction process by microemulsion consists of two stages. In the first one, the metal ion, present in the aqueous phase, is extracted by the microemulsion phase. In a second step, the re-extraction process occurs: the microemulsion phase, rich in metal, is acidified, and the metal is released to a new aqueous phase that contains higher metal concentration. The knowledge of these systems, as well as of its properties, requires a previous study based on pseudoternary phase diagrams, which were constructed with the purpose of delimitating Winsorʹs regions. The experiments were carried out by varying the cosurfactant/surfactant (C/S) ratio from 4 to 60, seeking to use the smallest amount of surfactant. The surfactant saturation study was made using the best C/S ratio, where metal concentrations (Ga and Al) were varied in the synthetic Bayer liquor. The microemulsion extraction points (18) were chosen inside the Winsor II region. In re-extraction experiments, hydrochloric acid, in different concentrations, was used, and it was observed that gallium and aluminum can be re-extracted in a selective way. Ga and Al extraction/re-extraction processes by microemulsion showed to be effective, reaching extraction percentiles of 99.63% for gallium and 98.89% for aluminum.