Nitrate samples back-extracted with

The liquid-liquid extraction feed solutions were prepared by dilution of the neodymium nitrate stock solution with distilled water and nitric acid. These then were contacted with equal volumes of 1M HDEHP in separatory funnels, agitated for. 5 hr by a mechanical shaker, allowed to separate for. 5 hr, shaken another. 5 hr, then allowed to settle for 12 hr before the phases were separated carefully. A volumetric sample of the organic phase was back-extracted four times with an equal volume of 6M HN03. This solution was evaporated to dryness in order to remove the excess acid and then diluted to an appropriate concentration. The pH of this solution was adjusted to 3.0 to eliminate any hydrolysis effects... 

For the uranyl-TRUEX system, the average water soluble uranyl concentration was low, 7 X 10 M. It appears that TRUEX bound uranyl ions are not back extracted into the neutral pH simulated groundwater. For uranyl samples deposited as nitrate salts or hydroxides, the solubility in the absence of phosphate is about 1 x 10" M at pH 5 and pH 6, rising to 2 x 10" M at pH 7 and 2.6 x lO" M at pH 8. The increase in solubility at higher pH is a direct result of increased uranyl-carbonate complexation. With the introduction of phosphate, uranyl solubility is reduced at all pH s, as shown in Figure 2. Uranyl solubility is generally lowest for 0.0001 M phosphate, rising... 

Antimony In the direct y-measurement of the samples, the four strongest peaks of Sb could be observed and used for determination of the concentration. Chemical separation was also successfidly performed as follows. 2 ml of the sample solution was converted from nitrate to chloride medium by repeated evaporations with concentrated hydrochloric acid. After dissolution in 3 M HCl, antimony can be extracted into pure chloroform (or another organic solvent). It can then be back-extracted into 0.1 M HCl. The extraction step is not quantitative, and three to four extractions with fresh solvent are required to obtain an acceptable yield. The back-extraction step is quantitative. The y-spectrometric investigation showed that neither the organic nor the final aqueous phase contained anything but antimony isotopes. 

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