Phosphoric leach liquors

Ryon, Daley, and Lowrie [Chem. Eng. Ftog., 55(10), 70, (1959), U.S. AFC ORNL-2951, I960]. Continuous extraction of uranium from sulfate-ore-leach liquors and kerosine -t- trihiityl phosphate and di(2-ethylhexyl)-phosphoric acid baffled vessels, turbine agitated. There is strong evidence of the influence of a slow chemical reaction. 

Vanadium usually is recovered from its ores by one of two processes, (1) leaching raw mineral with hot dilute sulfuric acid, and (2) roasting ore with common salt to convert vanadium into water soluble sodium vanadates. In the sulfuric acid leaching process, vanadium is extracted from acid leach liquors by solvent extraction with an aliphatic amine or an alkyl phosphoric acid in kerosene. The organic solvent extract then is treated with an aqueous solution of ammonia in the presence of ammonium chloride to convert vanadium into ammonium metavanadate. Alternatively, the organic extract is treated with dilute sulfuric acid or an aqueous solution of soda ash under controlled conditions of pH. Vanadium is precipitated from this solution as a red cake of sodium polyvanadate. 

Nickel and cobalt often occur with copper, and must be separated in pure form from hydrometallurgical leach liquors. Organic acid extractants can quite readily separate copper from cobalt and nickel, but the separation of cobalt from nickel is rather difficult. In one Ni/Co separation process, di-2-ethyl hexyl phosphoric acid (D2EHPA) is used as extractant, with strict control of the pH of the aqueous phase to take full advantage of the slightly different equilibrium constants for the Co and Ni reactions. Pulsed column contactors are used rather than mixer-settlers, and nickel impurity is removed from the loaded organic phase by scrubbing it with a cobalt-rich phase. 

For extraction of uranium from sulfate leach liquors, alkyl phosphoric acids, alkyl phosphates, and secondary and tertiary alkyl amines are used in an inert diluent such as kerosene. The formation of a third phase is suppressed by addition of modifiers such as long-chain alcohols or neutral phosphate esters. Such compounds also increase the solubility of the amine salt in the diluent and improve phase separation. 

Di(2-ethylhexyl) phosphoric acid (CsHnOljPCXOH) Extract uranium from leach liquors Dapex... 

Although the Dapex process is no longer being widely used to extract uranium from sulfuric acid leach liquors, organic phosphoric acids are favored for extracting by-product uranium from commercial phosphoric acid. Organic amines are impractical for this application because they are too fully saturated by the strong acid. 

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. 

C to precipitate lithium carbonate. The end-liquor was next treated with a small amount of phosphoric acid and evaporated to nearly sodium sulfate s crystallization point, precipitating trisodium phosphate that was recycled to the licons leach step. The final solution then only contained <0.07% Li instead of its original 0.28% Li, and it was sent to the soda products plant. The operation produced about 900 mt/yr of lithium carbonate, with an overall recovery from the lithium in the brine entering the evaporators of about 30% (Rykken, 1976 Williams, 1976). The operation was terminated in 1978 after 40 years of production when the soda products plant was closed. 

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