Study on the Cloud Point Extraction of Gd(III) with 8-Hydroxyquinoline

The extraction of gadolinium was studied using Cloud Point Extraction (CPE) with 8-hydroxyquinoline (8-HQ) as a chelating agent. The structure of the extracted Gd3+ complex with 8-HQ in the micelle of Triton X114 was determined using log-log analysis of the extraction data. A ratio of 8-HQ to Gd3+ of 3:1 was found. The CPE results were compared with those obtained by classical liquid-liquid extraction with chloroform as solvent. The parameters of the extraction process in both media were determined and compared. A quantitative extraction of Gd3+ at pH 5.5 was obtained by CPE using a 8-HQ/Gd3+ ratio of 10 although a 8-HQ/Gd3+ ratio of 500 was necessary for solvent extraction using chloroform as solvent, illustrating an increase of the mass action of extractants when using CPE instead of solvent extraction. Under those conditions, a higher extraction constant was determined for CPE compared with solvent extraction even if the formation of adducts in the CPE system could not be checked experimentally.