Uranium recovering from leach liquors

Recovery of uranium from leach liquors. Uranium may be recovered from leach liquors by precipitation, ion exchange, or solvent extraction. Precipitation with sodium hydroxide was the recovery method used in the first uranium mills. When used on sodium carbonate leach liquors, the uranium precipitate is fairly free of other metallic contaminants, because sodium carbonate dissolves few other metals beside uranium. However, when used in sulfuric acid leach liquors, the uranium precipitate contains other metals, such as iron dissolved from the ore by the add, and is no longer commercially acceptable. Consequently, in the United States, uranium mills emfdoying add leaching now follow it with selective recovery by either solvent extraction or ion exchange. These processes are described in Secs. 8.5 and 8.6, respectively. 

The organic amine extractants are the most commonly used anion exchangers. Secondary amines have been used to recover uranium from leach liquors (GlO) secondary and tertiary amines to recover molybdenum from uranium mill circuits (L13) a primary amine, diethylenetriamine-penta-acetic acid (DTPA) to extract cerium group lanthanides (B6) tri-,V-butylamine-3-methyl-2-butanonc to separate yttrium and rare earth nitrates (G13) tricaprylyl amine (Alamine 336) and methyltrioctyl-ammonium salt (Aliquat 336) to recover vanadium from acidic solutions (A3) and Aliquat 336 to extract vanadium from slightly acidic or alkaline leach liquor (S36). 

Figure 5.9 Amex process for recovering uranium from leach liquor. Conditions approximately those of one circuit of Kerr-McGee mill.

Recovery of uranium from leach liquors. Processes for recovering uranium from leach... 

Another example of a cost-effective liquid-liquid extraction process is the one used for recoveiw of uranium from ore leach liquors (Fig. 15-3). In this case the solvents, alkyl phosphates in kerosine, are recovered by liquid-liquid extraclion using a strip solution, and the... 

Molybdenum can also be recovered economically from some uranium leach liquors, particularly those of the USA. When uranium is stripped from amine extractants by solutions of sodium chloride, any molybdenum present remains in the organic phase, and can be subsequently recovered by being stripped into a solution of sodium carbonate. A process has been operated in which the strip liquor is acidified to a pH value of 4.5 and the molybdenum is reextracted into a solution of quaternary amine chloride in kerosene.218 The extracted metal is stripped into a solution containing sodium hydroxide and sodium chloride to produce liquors containing 30-40 g of molybdenum per litre, from which calcium molybdate can be precipitated by the addition of calcium chloride. 

In this mill, uranium is recovered from carbonate leach liquor by precipitation with sodium... 

Processes for recovering uranium from acid leach liquors used in the United States include sdvent extraction with organic amines, sdvent extraction with organophosphorus compounds. 

Precipitation. Actually, this process is used to recover uranium from leach alkaline liquor. It consists in precipitating the insoluble yellow sodium diuranate, Na UjOj, known as yellow cake, adding sodium hydroxide (i.e., caustic soda) to the mother liquor according to the following reaction ... 

The recovery of uranium from ores uses SX to reject impurities and concentrate the uranium in solution so that it can be economically recovered (Gupta and Singh 2003 Lloyd 1983). The choice of extractant depends on the lixiviant used in the upstream leaching operation, which, in turn, depends on the type of ore in which the uranium is found. Most nranium-bearing ores are readily leached in sulfuric acid and the uraninm is recovered by SX using amines or dialkylorganophosphorus acids. Phosphate ores (snch as those in Florida) are leached in a mixture of sulfuric and phosphoric acids or in phosphoric acid alone. Hot nitric acid has also been used as a lixiviant for nraninm ores (as at Phalaborwa, South Africa). The two common extraction systems for the recovery of uranium(VI) from sulfate leach liquors are compared in Table 5.6. 

The leach liquors are then poured through ion-exchanger beds or columns. The resins employed for these processes are typically of the sulfonate variety. Uranium is removed from the resin by elution with solutions containing high concentrations of chloride or nitrate ions after which the uranium is recovered by precipitation through addition of ammonia. 

In the aluminium industry the most widely used method for the extraction of alumina (AI2O3) from bauxite is the Bayer process, in which aluminium and silica are leached from bauxite under pressure with hot caustic soda. The residue is red mud , a silt-like mixture of iron oxides, titanium dioxide, silica, caustic and many impurities. Roughly one ton of insoluble residue of red mud is produced for each ton of alumina. The liquors, following appropriate treatment to recover alumina, are recycled. In view of its high solubility in nature, it seems that most of the uranium must also be leached and possibly build up in the leach liquors. Small mills are now recovering this Uranium, but analyses of red muds show uranium contents that vary from 12 to 40ppm uranium, which suggest that it is not all leached. 

Uranium Is recovered from carbonate leach liquors by 2uilon exchange in industrial operations. Its anion exchange behavior is similar in carbonate solution to that in sulfate solution. 

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