GB845842A - Improvements in and relating to uranium extraction processes - Google Patents

Abstract

In the extraction of uranium values from liquors obtained by leaching uranium ores with aqueous alkali-metal carbonate solutions, the liquor is ozonised and filtered to obtain a solution which, after any necessary adjustment, has a pH of 9.5-11.5, a carbonate concentration calculated as Na2CO3 of less than 30 g.p.l., a bicarbonate concentration calculated as NaHCO3 of less than 15 g.p.l., and a sulphate concentration calculated as SO4 of less than 6 g.p.l., and this solution is contacted with an anion exchange resin. The barren solution may be recycled to the ore leaching step. The uranium adsorbed as a tetravalent uranyl carbonate is recovered by elution, for example, with sodium nitrate or chloride. The eluate thus obtained may be acidified and a salt having the same anion as the eluant added to precipitate insoluble salts. For example, a calcium salt may be added, such as calcium nitrate when sodium nitrate is the eluant. The acid employed for the acidification may also have the same anion as the eluant. The precipitated salts may be removed by filtration, the uranium salts in the resulting solution extracted by an immiscible solvent, for example, a mixture of paraffin and tributyl phosphate, and the remaining aqueous solution neutralised by the addition of a substance having the same cation as the eluant, for example sodium hydroxide. The resulting solution may be employed to elute further quantities of uranium from the anionexchange material. The uranium values may be extracted from the organic solvent as araryl nitrate or chloride for example, by means of water. A suitable rate of ozone supply in the initial ozonising step is from 1 to 6 grams of ozone per hour for a rate of solution supply of 40 litres per hour. The ozonisation is preferably carried out at room temperature for a period of 10-15 minutes, and the ozone is conveniently introduced by means of a microporous diffuser formed of fritted silica or carborundum, or of agglomerated carbon. The filtration after ozonisation is normally carried out in the presence of powdered filtering aids, such as diatomaceous earth, asbestos, or silica.