Solvent extraction of zirconium(IV) from chloride media by D2EHPA in kerosene

The apparent equilibrium of extraction of zirconium(IV) from chloride media by D2EHPA in kerosene is found to depend on ageing of the aqueous phase. When the aqueous phase, just after preparation, is used in the extraction study, reproducible results are not obtained. With increasing ageing time, the apparent distribution ratio (D) is increased for a particular set of experimental parameters. The system has been thoroughly investigated for 1- and 30-day ageing. In both cases, the apparent equilibration time is 15 min. D is decreased with increasing Zr(IV) concentration in the aqueous phase but the nature depends on ageing. In both cases of ageing, logD vs, - log[HCl] plots are peculiar in nature. For 1-day ageing, the slope is similar to - 1 above 3 M HCl and also below 0.3 M HCl, and is zero within 0.3-3.0 M HC1 In contrast, for the 30-day aged system, the slope is similar to - 2 above 2 M HC1, similar to - 1 below 0.5 M HCl, and zero between 0.5 and 2.0 M HCl The extract-ant dependencies are 2 and 4 for 1- and 30-day aged, systems respectively. Chloride ion has a large effect on D for the 1-day aged system, but no effect on D for the 30-day aged system. From the temperature dependence data, DeltaH values have been determined. The possible extraction equilibrium reactions have been suggested and supported by the loading tests, as well as by the molecular weight, Zr/P ratio, Zr/Cl ratio and infrared spectral data of the extracted species. (C) 2002 Published by Elsevier Science B.V.