Gallium solvent extraction

In some cases, a simple solvent extraction is sufficient to remove a particular impurity. For example, traces of gallium can be removed from titanous chloride in hydrochloric acid by extraction with diisopropyl ether. 

Harbuck, D. D. Judd, J. C. Behunin, D. V. Germanium solvent extraction from sulfuric acid solutions (and co-extraction of germanium and gallium). Solvent Extr. Ion Exch. 1991, 9, 383-401. 

The most widely used technique for the separation of large quantities of radioactive material is that of solvent extraction. The principle of the method is that ideally the partition coefficient of a compound between two solvents does not depend on concentration in a given set of conditions. This was shown in an early paper of Graham and Sea-borg (35) who demonstrated that the partition coefficients of gallium and cobalt chlorides between ether and aqueous hydrochloric acid were the same for concentrations of lCTli molar (i. e. no added carrier) as for 1-6xl0 s molar. 

Several other analytical procedures exist in which solvent extraction may be applied. Thus extraction has been used in a limited number of analyses with procedures such as (1) luminescence (fluorimetry), where, for example, the detection limit of rhodamine complexes of gallium or indium can be increased by extraction [28] (2) electron spin resonance using a spin-labelled extractant [29] and (3) mass spectrometry, where an organic extract of the analyte is evaporated onto pure AI2O3 before analysis [30]. 

The purification of the gallium salt solutions is carried out by solvent extraction and/or by ion exchange. The most effective extractants are dialkyl-phosphates in sulfate medium and ethers, ketones (qv), alcohols, and trialkyl-phosphates in chloride medium. Electrorefining, ie, anodic dissolution and simultaneous cathodic deposition, is also used to purify metallic gallium. 

Morie, G. P., and T. R. Sweet Analysis of Mixtures of Aluminium, Gallium and Indium by Solvent Extraction and Gas Chromatography. Anal. Chem. 37, 1552 (1965). 

The detection limit for gallium determination at 287.4 nm in an air-acetylene flame is only about 70 ng ml - and that by flame AFS is not much better, and sometimes even worse.1 The detection limit by flame AES at 403.3 nm is appreciably better, especially if a nitrous oxide-acetylene flame is used. This reflects the low excitation energy. These values are too low to make the direct determinations useful in environmental applications, and therefore solvent extraction is often used for pre-concentration.1 One method often used is the extraction of the anionic keto-chloro complex from strong hydrochloric acid solution (e.g. 5.5M) into 4-methylpentan-2-one.25,26 Co-extraction of iron may... 

T. Imasaka, T. Harada, and N. Ishibashi, Fluorimetric Determination of Gallium with Lumogallion by Flow Injection Analysis Based on Solvent Extraction. Ana/. Chim. Acta, 129 (1981) 195. 

Isotherms of Ga extraction by TVEX-TBP, TVEX-DIOMP as well as by liquid TBP andDIOMP from 3,5, and 8 mol/L HCl solutions show (Figure 8.25 and Figure 8.26) that extractant equilibrium capacity increases with aqueous phase acidity increase extractant capacity in TVEX matrix is 1.3 to 1.5 times higher as compared with solvent extractant. Enthalpy of gallium extraction from 3 mol/L HCl is -11.7 kJ/mol for TBP and -12.0 kJ/mol for TVEX-TBP. Diffusion coefficient of gallium extraction is 4.210-" mVs for TVEX-TBP (3mol/L HCl) and 5.410-" mVs for TVEX-DIOMP (6 mol/L HCl) [27]. 

Extraction and spec A = 510 nm of gallium with 4-(2-pyridylazo)resorcinol Comparison of the determination of gallium by a rhodamine B spectrophotometric method and by an AA method based on preliminary solvent extraction... 

In these complicated extraction systems containing the polymeric and/or hydroxo species, one would expect the solvent used as a diluent to exert a considerable effect on the extraction equilibrium. In the extraction of gallium (III) with decanoic acid it has been found that the less polar the solvent, the more polymerized the extracted species (150). More recently, the solvent effect on the extraction (156) and dimerization (151, 153) of copper(II) decanoate has been interpreted according to regular solution theory (141,142). 

Brzozka and Rozycki (16) stated that pH1/2 for copper(H) cyclohex-anecarboxylate and the concentration of the monomeric copper(II) species in the organic phase increased in the order carbon tetrachloride < benzene < 3-methyl-l-butanol. Yamadaef al. found that the less polar the solvent, the more polymerized is the extracted species of gallium (III) decanoate (150) (see Table 13). 

Gallium has been extracted from HCl media into chloroform in the presence of N-benzylaniline [3,4], n-octylaniline [5], and crown ethers (e.g., dicyclohexyl-18-crown-6) [6], and into o-dichlorobenzene in the presence of the tetraphenylarsonium ion [7]. Gallium has been separated from In and other metals by extraction into non-polar solvents in the form of its chelates with cupferron [8], HTTA [9], BPHA, p-diketones [10], and alkylphosphoric acids [11]. Gallium has been extracted also, from citric acid solutions of pH 2-3.5, into xylene solutions of Amberlit LA-2 [12] and Aliquat 336S [13]. 

The gallium chloride complex, GaCU", reacts with Rhodamine B (formula 4.29), to form the ion pair which can be extracted from HCl medium into benzene or other solvents. The pink extract is the basis of a sensitive and selective method for the determination of gallium [20-22]. Addition of NaCI improves the extraction efficiency very effectively [22]. A mixture of benzene and diethyl ether, and also o-dichlorobenzene [23], have been recommended as extractants. Since Rhodamine B is only slightly soluble in o-dichlorobenzene, but dissolves readily in the meta-isomer, the o-dichlorobenzene must not be contaminated with the metaisomer. 

Determination of Ga. Place in a beaker the ethereal extract obtained as above, add 50 mg of NaCl, and evaporate to dryness on a water-bath. Dissolve the residue in 5 ml of 6.5 M HCl containing TiCls, transfer the solution to a separating funnel, add 1 ml of the Rhodamine B solution, and extract gallium with two 10-ml portions of chlorobenzene and CCI4 (3-rl) solution (shake with each portion for about 1 min). Place the clear extract in a 25-ml standard flask, dilute to the mark with solvent, mix, and measure the absorbance of the solution at 560 nm vs. a reagent blank. 

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