Extraction of indium with N,N-di(1-methylheptyl)acetamide, di(1-methylheptyl)methyl phosphate, and tributylphosphate by solvent extraction in hydrochloric acid solution

Solvent extraction of indium from hydrochloric acid solution using N,N-di(1-methyl-eptyl) acetamide (N503), di (l-methylheptyl)methyl phosphate (P350), and tributyl phosphate (TBP) diluted in sulfonated kerosene was investigated. Extraction was studied as a function of hydrochloric acid and chloride ion concentrations, organicphase composition, initial indium concentration, phase contact time, and aqueous/organic (A/O) volumetric ratio. The extraction stoichiometry was determined by slope analysis and confirmed by Fourier-transform infrared spectroscopy. It was found that indium extraction efficiency decreased in the order: N503 > P350 > TBP. The extracted complexes with N503 and P350 were determined to be [InCl4](-) [2S center dot H](+); the complex formed with TBP was [InCl4](-) [3S center dot H](+), where S represents the neutral extractant species. N503 was found to be best extractant of the three with respect to extracting indium from solutions containing a high concentration of hydrochloric acid. Almost quantitative (99%) indium extraction was obtained using 0.5 mol.L-1 N503 in three extraction stages at an A/O ratio of 2/1; 100% of the indium on the loaded organic phase was stripped by water in two stages at an A/O ratio of 1/3. Indium can therefore be extracted from hydrochloric acid and enriched in a low-acidity strip solution.