Solvent extraction processes organophosphorus extractants

Deshpande, S.M. Mishra, S.L. Gajankush, R.B. Thakur, N.V. Koppikar, K.S. Recovery of high purity Y203 by solvent extraction route using organophosphorus extractants, Min. Process. Extr. Metall. Rev. 10 (1992) 267-273. 

Experimental studies were therefore directed to investigate the removal of actinides from both diluted (5000 l/t) and concentrated (about 500 l/t) HAW solutions. Three alternative processes have been selected for this purpose. They all rely upon actinide separation at low acidity conditions requiring a preliminary denitration step. Two of them (TBP and HDEHP processes) are based on solvent extraction techniques using as extractants a neutral (TBP) and an acidic (HDEHP) organophosphorus compound respectively. The third process (OXAL) applies as the first step the precipitation of actinides and lanthanides FP as oxalates. 

Ihree papers from Oak Ridge National Laboratory provide a comprehensive summary of developments in solvent extraction of uranium firom leach liquors. Coleman et al. [C2] describe studies of a number of possible amine extractants. Blake et al. [B4] describe work with organophosphorus compounds. Brown et al. [B8] describe processes based on both types of extractants. 

T. Principe and G.P. Demopoulos, "Solvent Extraction Removal of Iron from Zinc Process Solutions Using Organophosphorus Extractants", EPD Congress 1998. B. Mishra, Ed., The Minerals, Metals and Materials Society, Warrendale, PA, U.S.A., 1998, 267-287. 

Solvent extraction processes and systems using amine and organophosphorus extractants are extensively used for the initial recovery and separation of gram... 

SFE. SFE has been established as the extraction method of choice for solid samples. The usefulness of SFE for soil samples has been demonstrated for carbamate,organophosphorus and organochlorine pesticides. However, SFE is more effective in extracting nonpolar than polar residues. In order to obtain a greater extraction efficiency for the polar residues of imidacloprid, the addition of 20% methanol as modifier is required. Extraction at 276 bar and 80 °C with a solvent consisting of supercritical carbon dioxide modified with methanol (5%) for 40 min gives a recovery of 97% (RSD = 3.6%, n = 10). It is possible to use process-scale SFE to decontaminate pesticide residues from dust waste. ... 

In the Nippon Mining Company process,163 the aqueous feed consists of a solution of cobalt, nickel and other metal sulfates obtained by the high-pressure oxidative leaching of a mixed metal sulfide ore. Following the removal of iron and copper by chemical precipitation methods, and the successive extraction of zinc and cobalt by organophosphorus acid reagents (Section 63.3.2.2) under weakly acidic conditions, the pH value of the solution is adjusted to between 9 and 9.5 with ammonia, and nickel is extracted into a 25% solution of LIX 64N in an alkane solvent. 

SPME was hrst used by Pawliszyn et al. in 1990. It is a two-step process conductive to the simultaneous extraction and preconcentration of analytes form sample matrices. In the first step, a fused-silica fiber coated with a polymeric stationary phase is exposed to the sample matrix where the analyte partitions between the matrix and the polymeric stationary phase. In the second step, the fiber/analyte is transferred to the analytical instrument for desorption, separation, and quantification. SPME has a number of advantages over traditional extraction techniques for pesticides. In fact, it is fast, simple, solvent-free, and easily automated for both GC and HPLC instruments. It exhibits good linearity and sensitivity. Thus, carbamate and organophosphorus pesticides in golf course samples were successfully extracted by SPME and analyzed by HPLC by Jinno et al. ... 

The metal complexes formed by the anionic organophosphorus extractants are, on the other hand, very soluble in organic solvents. Such compounds have therefore been used for various technical processes. Most important is the monobasic diethylhexylphosphoric acid (HDEHP), but dibutylphosphoric acid (DBP) has also been widely applied [103,155]. Some data illustrating the properties of these extractants are collected in Table 21.19. 

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