Loaded strip liquor

Element Feed Raffinate Loaded Organic Loaded Strip Liquor... 

A tertiary amine (Alamine 336) is used as a selective extractant of Cr(VI). The extraction mechanism involves ion pairing between the amine and the dichromate anion, HCr04. After extraction, the Cr(VI)-loaded extractant is stripped with alkali to produce a strip liquor, containing 2% Cr(VI). This solution can be recycled. 

It can be seen from Figure 11 that, by the appropriate choice of the equilibrium concentration of chloride ion in the aqueous phase, separations between certain pairs of metals can be made, for example between copper(II) and manganese(II) at a chloride concentration of 3.0 M, and between cobalt(II) and nickel(II) at a chloride concentration of 6 to 8 M. Furthermore, the metals can be stripped from the loaded organic phase by being contacted with an appropriate volume of water so that the equilibrium concentration of chloride ion in the strip liquor lies on the lower portion of the extraction curve, where substantial aquation of the extracted chlorometallate occurs... 

The back-extraction (stripping) of palladium is achieved in the hydroxyoxime process by contacting the loaded organic phase with a concentrated solution of hydrochloric acid (about 6 M), thus causing the reversal of reaction (76). Palladium can be recovered from the strip liquor by the addition of ammonia, and the precipitated Pd(NH3)2Cl2 can be calcined to yield pure palladium metal. In the dialkyl sulfide process, however, the extraction reaction (75) is independent of acidity, and is therefore reversed by the use of aqueous ammonia, which forms a stable cationic complex with palladium(II) ... 

The solvent extraction of rare-earth nitrates into solutions of TBP has been used commercially for the production of high-purity oxides of yttrium, lanthanum, praseodymium and neodymium from various mineral concentrates,39 as well as for the recovery of mixed rare-earth oxides as a byproduct in the manufacture of phosphoric acid from apatite ores.272 273 In both instances, extraction is carried out from concentrated nitrate solutions, and the loaded organic phases are stripped with water. The rare-earth metals are precipitated from the strip liquors in the form of hydroxides or oxalates, both of which can be calcined to the oxides. Since the distribution coefficients (D) for adjacent rare earths are closely similar, mixer—settler assemblies with 50 or more stages operated under conditions of total reflux are necessary to yield products of adequate purity.39... 

The leach liquor is first treated with a DEHPA solution to extract the heavy lanthanides, leaving the light elements in the raffinate. The loaded reagent is then stripped first with l.Smoldm nitric acid to remove the elements from neodymium to terbium, followed by 6moldm acid to separate yttrium and remaining heavy elements. Ytterbium and lutetium are only partially removed hence, a final strip with stronger acid, as mentioned earlier, or with 10% alkali is required before organic phase recycle. The main product from this flow sheet was yttrium, and the yttrium nitrate product was further extracted with a quaternary amine to produce a 99.999% product. 

Acidification of the leach liquor with sulfuric acid produces solutions containing Mog0264-, which is extracted into a solution of tertiary amine hydrogen sulfate as described previously. Loaded organic phases are stripped with aqueous ammonia to give solutions from which ammonium paramolybdate can subsequently be crystallized ... 

The improved capabilities of LIX 64 N reagent for recovery, purification, and concentration of copper values from acidic leach liquors were described by DeMent and Merigold (DlO). The leaching of copper sulfide flotation concentrates with subsequent recovery of copper by LIX 64 N was shown to be technically feasible. This extractant loads and strips faster, is more effective in extracting copper from a lower pH solution, has considerably less secondary entrainment, has better iron rejection, and may be used at levels up to 30 vol. % in kerosene without aqueous entrainment. Use of the reagent in operating pilot and commercial plants is also discussed. 

Among U.S. mills, the moving bed system is used in the mill of the Lucky Me Uranium Company at Gas Hills, Wyoming [D2a]. The moving-bed process is a modified batch-operated, fixed-bed ion-exchange system. Adsorption of uranium from leach liquor is carried out in two parallel sets of three columns in series. Each set is operated cyclically as in the fixed-bed system described earlier, with the feed point moved progressively around the cycle as the last bed in flow sequence becomes saturated. The novelty of the moving-bed system is in the diysical transfer of loaded resin from an adsorption cdumn to one of three elution columns, also operated cyclically in series. After elution is complete, the stripped resin is transfened back to one of the two adsorption sets, vdiere it is placed last in flow sequence. 

In some flow sheets, a scrub circuit is introduced between the extraction and stripping circuits. A scrub liquor is introduced to scrub off unwanted coextracted species from the loaded organic phase by displacing the impurities with the more strongly complexed main element. This produces a scrubbed organic phase. For systems in which the extractant is completely selective for the species of interest or when high selectivity of extraction is not required (such as for bulk extractions), a scrub circuit is not necessary. Usually, however, some coextraction of other species occurs and a scrub circuit is anployed to reduce the transfer of these species to the LSL. 

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