The Extraction of Zirconium(IV) from Hydrochloric Acid Solutions by Long-Chain Alkylamine and Alkylammonium Compound

Abstract

The extraction of zirconium(IV) from hydrochloric acid solutions with trioctylamine (TOA, R3N) and tricaprylmethylammonium chloride (Aliquat-336, R3R'NCl) in benzene has been investigated under different conditions. In both extraction systems, it is found that the distribution coefficient increases steeply with increasing of initial aqueous hydrochloric acid concentration at 6.0 molg, although Aliquat-336 is more efficient for the extraction of zirconium(1v) than TOA. It is observed that the stoichiometric composition of the organic extracts with TOA and Aliquat-336 are (R3NH)2ZrCl6 and (R3R'N)2ZrCl6, respectively. This is supported by the dependency of distribution coefficient on solvent concentration. Accordingly it is inferred that the extractions of zirconium(1V) from hydrochloric acid solutions with TOA and Aliquat-336 proceed as the following equilidrium reactions, respectively,
ZrCl4(aq) + 2 R3NHCl(0, 0 (R3NH) 2ZrCloorg)
and
ZrCl62-(aq) + 2 RSR'NCI(org) 4t (R3R'N) 2ZrO6(org) + 2 CI-cud
These results are also confirmed by IR and high resolution NMR spectral studies of the organic phases.
Further the effect of diluent on the extraction is surveyed with Aliquat-336. The results show that the extraction is enhanced in 1, 2-dichloroethane and reduced in carbon tetrachloride and xylene.