KELEX extractants

Solubility data on the LIX and Kelex extractants indicate that these materials are poorly soluble in aqueous media. Accordingly, in plant operations at about pH 1.5, reported losses are approximately <15 ppm, which includes both soluble and entrainment losses as determined by inventory (detailed later in Table 7.6). The solubility of LIX 63, LIX 64, and LIX 64N in water at pH 4.8 has been reported at 5.8, 4.3, and 6.2 ppm, respectively [20]. 

A number of chelating cation exchangers have been used as extractants. The modes of complex formation by acylthioureas (32) are described in Section 9.17.6.3 382-385 Their use has been extended to membrane systems for the recovery of Pd 392 The use of Kelex 100297 and of hydroxy-oximes14,297 (Table 3) has been reviewed and methods for improving rates of phase transfer have been surveyed by Szymanowski.14... 

Kyuchoukov, G. Jakubiak, A. Szymanowski, J. Cote, G. Extraction of zinc(II) from highly concentrated chloride solutions by KELEX 100. Solvent Extr. Res. Dev. Jpn. 1998, 5, 172-188. 

Alam, M. S. Inoue, K. Extraction of rhodium from other platinum group metals with Kelex 100 from chloride media containing tin. Hydrometallurgy 1997, 46, 373-382. 

Al-Bazi, S. J. Freiser, H. Phase-transfer catalysts in extraction kinetics palladium extraction by dioctyl sulfide and KELEX 100. Inorg. Chem. 1989, 28, 417 120. 

The solubility of Kelex 100 has been reported to be 4.4 (pH 0.5), 1.4 (pH 1.0), and 1.6 (pH 1.5)ppm, in tests employing 0.5moldm Kelex 100 in Solvesso 150 diluent for the extraction of copper from solutions containing about 30 g dm of metals (Cu, Ni, and Co) [21]. Furthermore, over several months no change in the Kelex concentration was found in pilot plant operations with a 0.5moldm Kelex solution [21]. At higher pH values (up to 9) Kelex solubility has been determined at < 1 ppm in ammonium sulfate solutions up to 300 g dm [22]. It would be expected that the amphoteric nature of Kelex would show increasing solubility at pH values above 7, and lower than about 1, similar to the variation in solubility of... 

Hartlage, J. A. Kelex 100—a new reagent for copper solvent extraction. Paper presented at Society of Mineral Engineers, AIME Fall Meeting, Salt Lake City, September 1969. 

Another commercial reagent based on quinoline is LIX34, which is a derivative of 8-alkylarylsulfonamidoquinoline. It has good extractant and stripping performance and, unlike Kelex 100, does not protonate easily. However, the cost of production outweighed these advantages. 

Matsumoto M, Shimauchi H, Kondo K, and Nakashio F, Kinetics of copper extraction with Kelex-100 using a hollow fiber membrane extractor, Solvent Extraction and Ion Exchange 1987, 5(2), 301-323. 

Kelex 100 Selective extraction of Cu from ncidic solutions Extraction of Co, Ni, Co, and Zn from alksline ammonia solution... 

To account for nonidealities in solution ons can use activity coefficients or siioply replace activities with species concentrations in Eq. (8.3-1) to obtain an empirical mass-actiou equilibrium quotient that 1 concentration dependent. Bauer and ChaprtW treated data for copper extraction by Kelex 100 by a chemical model, holh with and without explicit activity coufficjeni lemis, and were successful in extrapolating from results with 5% Kelex to obtain an accuraie copper distribution curve for 20% Kelex. Hoh and Bautista6 used a similar approach to correlate equilibrium data Tor copper with LIX 65N and with Kelex 100. The concentration-based equilibrium constant at 25 C was fbnnd to ba on the older of 0.03 for LIX 65N in... 

The relatively large valons found for the extraction equilibrium constant of copper with Kelex 100 (3 and 90) indicate (hat shipping of copper from (his rcngenl should he difficult. It is fonnd, however, that copper does strip reedily into sulfuric acid solutions because Kalex 100 reacts with sulhiric acid in preference to copper. Fitting the extinction of sulforic acid by Kelex 100 by a chemical-reaction equilibrium constant. 

FIGURE 8.3-9 Comparison of chemical-equilibrium extraction models with stripping date for copper in Kelex 100. Curve A follows Eq. (8.3-1). Curve S is obtained by solving Eq. < 8,3- ) simultaneously with Eq. (8.3-2). From Ref, 5, with permission. 

An interesting comparative study of six different contactors is summarized in Fig. 8.5-1. An alkaline feed stream containing copper, nickel, 2inc. and emmonia was contacted with a Kelex 100 solution in each of rhe pilot-scale contactors. At a pH above 7 the reaction kinetics of Kelex are probebly fast, bet it loses some of its intrinsic selectivity for copper because of the tendency of nickel and zinc to be extracted. Although the various contactors conld be made to operate at comparable leveU with respect to specific throughput and oepper-exiraction efficiency, they exhibited quite different seleclivities. Detailed liquid-liquid reaeter models wonld help to identify and predict such variations in efficiency and selectivity. 

FIGURE 8 J-1 Comparisons of the operating characteristics of several contacting devices for the separation of copper front nickel and zinc by extraction from ammonia (pH 8) solution with Kelex. (o) Comparison of specific throughput at flooding, (b) Comparison of coppar extraction elficiency. (c) Compariaou of Cu-Zn selectivity. [Pg.493]

Cobalt and Nickel Recovery. Cobalt and nickel are relatively valuable metals often found in complex ores such as laterites or deep sea nodules. The metals can only be extracted from these ores by hydrometallurgy. A proposed recovery scheme based on coupled transport is shown in Figure 9.29. The first membrane contains LIX 54, which produces a nickel and copper concentrate and a cobalt raffinate stream. The concentrate stream is then passed to a second Kelex 100 membrane, which produces a copper and nickel stream. The cobalt III raffinate stream is neutralized and reduced to cobalt II, which can then be concentrated by a LIX 51 membrane. 

Figure 32 Comparison of germanium extraction with Kelex 100 in liquid-liquid and solid-liquid extraction systems. (From Ref. 30.)...

The complexation Co(II) and Ni(II) by 7-(4-ethyl-l-methyloctyl)-8-hydroxyquinoline (HL), the active constituent of the industrial extractant Kelex 100, proceeds through two paths linked through a protonic equilibrium. However, in contrast to the reactions discussed above, in which the kinetically important protonation involves the substituting ligand, the favored mechanism in this case involves metal ion protolysis as in Scheme 3, where for Co and Ni ", respectively, HL = 4.3 X 10 and 1.9 x 10 dm mol s" A hl[H20] = 16 and < 10" s", =... 

The use of chelating reagents (LIX and Kelex series), which are commercially available for solvent extraction, has been reviewed by Ashbrook 490). High-molecular-weight amines (Aliquat, Alamine, and Adogen series) are also in commercial use. The use of Aliquat-336 in the extraction of thorium 491) from spring waters has recently been reported 492). 

Derivatives of quinolines have been used as chelating agents for copper extraction. The most well known is 7-alkeny1-8-hydroquinoline and has the trade name KELEX 100 (see Fiure 2) (52). Substituted 8-sul-... 

Guesnet,P., Sabot,J.L. and D.Bauer. "Kinetics of cobalt oxidation in solvent extraction by 8-quinolinol and KELEX 100" (Proceedings of Int.Solvent Extraction Conf., ISEC 80, Belgium, 1980)... 

---