Applications of reversed-phase partition chromatography of uranium

Abstract

Keversed-phase partition Chromatography is shown to be a convenient and simple method for the quantitative separation and recovery of uranium either from impure solutions of unknown origin or from solutions of uranium alloys.The separation process has been studied and shown to obey a Freundlichtype isotherm from both nitric acid and hydrochloric acid media.Applications of the technique to specific problems in the analysis of uranium are briefly outlined.THE analysis of alloys of uranium with zircoiii~m, titanium, molybdenum, vanadium, etc., can often be simplified by an initial separation of the uranium, and the determination of trace impurities in such alloys can also be improved by a similar separation.Hamlin et aZ.l have applied the technique of reversed-phase partition chromatography, with the selective reagent tri-n-butyl phosphate, to the extraction of uranium from wastes and residues of unknown origin. This technique has the advantage of simplicity compared with continuous or counter-current extraction with the same reagent. After the sample solution has been adjusted to optimum acidity with nitric acid, it is passed through a column of inert lyophobic microporous particles impregnated with tri-n-butyl phosphate and previously conditioned with nitric acid solution. The uranium is retained as a band a t the top of the column and the impurities are removed by washing with nitric acid solution. The uranium itself is then eluted with water. The separation is affected only by the few elements that partition strongly into the selective reagent tri-n-butyl phosphate.This chromatographic technique has now been applied to the precise determination of uranium in complex alloys. By providing a simple means of removing uranium with the minimum number of transfers and analytical operations, high accuracy is easily achieved. Alloying constituents and impurities can also be determined in the column effluent if so required. EXPEKIMENTAL PREPARATION OF TRI-n-BUTYL PHOSPHATE-One volume of commercial-grade tri-n-Butyl phosphate was steam-distilled with 1.5 volumes of 0.5 M sodium hydroxide until the distillate was free from the odour of butanol. The tri-n-butyl phosphate was then separated from the aqueous alkaline phase, and washed with water and nitric acid.PREPARATION OF URANIUM SOLUTIONSreagent grade salt, and adjusted to the required molarity with nitric acid. when cool, the required amount was weighed and then dissolved in nitric acid.followed by repeated evaporations with distilled water to remove the excess of acid. APPARATUS-Preliminary experiments established the approximate size of the column required. Experiments with solutions containing 10 to 50 mg of uranium were carried out with a chromatographic tube of the same dimensions as that used by Hamlin et aZ.l Uranyl nitrate solutions for column experiments were prepared from the analytical-For precise work, spectrographically pure U,O, was ignited at 920" C for 1+ hours; Uranyl chloride solutions were prepared by dissolving pure UO, in hydrochloric acid * Presente...

Separation of Phenols by Reversed-Phase Chromatography.

“…Experiments were carried out in both nitric and perchloric acid solutions, and the effect of acid and nitrate concentrations on the observed "instability" constants was examined. Quadrivalent cerium ion forms adducts with many anions such as sulfate (2), chromate (8), nitrate (9), oxalate (S), and hydroxyl (6) in aqueous solution. Highly colored complexes are also formed with aliphatic alcohols, and analytical procedures have been developed for the determination of methanol, ethanol, and ethylene glycol by absorbtion spectrometry (8,4).…”

Chromatography

“…For partition columns, reversed-phase systems are now generally preferred; stationary phases such as 2-octanone (490), tri-n-octvlphosphine oxide (248,250,878), bis(2-ethylhexyl)orthophosphoric acid (1224,1720), and tributyl phosphate (323,437,468,652,1050,1434) give excellent resolution. When tributyl phosphate is used as the mobile phase, the rare earth elements are eluted in the order of decreasing atomic number (284) In TLC (1399), the migration of cations on silica gel is determined by the ion exchange properties of the adsorbent and the coordination tendencies of the solvent, e.g.…”

Separation of Various Cations by Reversed-Phase Partition Chromatography Using Neutral Organophosphorous Compounds

“…Almost all the cations could be detected either by their fluorescence under ultraviolet light or as dark spots on a faintly fluorescent background. A 0.1% aqueous solution of Arsenazo (13) was somewhat more convenient for the detection of the heavy metals such as thorium, uranium, and the lanthanides. These elements are readily detected as blue zones on a pink background after spraying with Arsenazo and treating with ammonia.…”