摘要:

The modification of hydroxyoximes, ester and amides of pyridine carboxylic acids with various oxygen containing modifiers (alcohols, alkylphenols, ketones, esters, etc.) is reviewed. The modifiers form co-associates with the copper extractants changing, in this way, the active concentration of the monomer and blocking the active groups of the extractants. The structures of such associates predicted by molecular modeling are given.

ISSN:0736-6299    

DOI:10.1080/07366299708934503

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Predicting the effectiveness of liquid-liquid extraction of metal chelates and choosing optimal extraction reagents requires several characteristics of the components of the extraction system to be taken into consideration. This paper provides an analysis of the factors that affect the value of the partition constant of a chelate and the possibilities to predict the value of the partition constant from the nature of the metal ion, the structure of the chelating reagent, and the organogenic elements, one might have expected these techniques to be capable to predict the partition constants of chelates as well. However, the problem of determining the increments of metals turned out to be very difficult even in the case of relatively simple complexes. An analysis of the partition constants of coordinatively-saturated metal acetylacetonates has shown that the values depend on a large number of parameters, some of which are correlated. The central metal atom modifies the donor properties of the heteroatoms in the extraction reagent molecule to such a great extent that one cannot assign them the increments valid for the free reagent molecule.

ISSN:0736-6299    

DOI:10.1080/07366299708934504

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

It is demonstrated that the electronegativity of metals extracted in the form of diethyldithiocarbamates affects the extraction constants in two ways, namely, through its influence on the chelate stability and the partition constants. The corresponding interrelations can be used to predict extraction constants from any of the following three characteristics: the Klopman electronegativity of the metal, the chelate partition constant, or the chelate stability constant.

ISSN:0736-6299    

DOI:10.1080/07366299708934505

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The extraction of cesium nitrate from a high concentration of sodium nitrate by a family of 21-crown-7 ethers in 1,2-dichloroethane has been investigated. Dibenzo-21-crown-7 (DB21C7) and bis[4(5),4′(5′)-rm-butylbenzo]-21-crown-7 (BtBB21C7) ethers have higher selectivity for cesium but lower extraction efficiency than dicyclohexano-21-crown-7 (DC21C7) ether. As measured by the distribution coefficient ratio Dcs/DNa, the cesium selectivity averaged 78 and 93 for DB21C7 and BtBB21C7, respectively. However, in the case of DC21C7, the cesium selectivity was lower and decreased approximately three-fold from 10 to 3 as cesiüm loading increased. Alkyl substitution on the benzo group has only a small effect on the extraction behavior. It was shown by use of the equilibrium modeling program SXLSQI that the extraction of sodium and cesium could be adequately modeled by augmenting the previously determined cesium nitrate equilibrium model with a 1:1 Na+:crown organic-phase complex. No evidence for a mixed-metal species was found. In accord with our previous study, cesium nitrate extraction entails formation of a 1:1 Cs+:crown complex, but a minor 1:2 complex also forms in the case of DC21C7. Although the sodium and cesium made possible by the U. S. Department of Energy Postgraduate Research Program administered by the Oak Ridge Associated Universities.

ISSN:0736-6299    

DOI:10.1080/07366299708934506

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The selective liquid-liquid extraction of various alkaline, alkaline-earth and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo coupling calix[4]arenes [p-(4-n-butyl-phenylazo)calix[4]arene(Ll), p-(4-phenylazophenyl-azo)calix[4]arene(L2), p-(4-acetamlidazo)calix[4]arene(L5)], p-(N′-2-thiazol-2-ylsulphanyl-azo)calix(4]arene(L4) and p-(2-thiazolazo)calix[4]arene(L5)] and the phenol derivatives [2-((5-bromo-2-pyridylazo)-5-diethylaminophenol(L6) and (2-chloro-4-nitrophenylazo)-5-sec-butyl-2-phenol(L7)]. It was found that compounds LI - L6 showed some selectivity towards Ag+, Hg+and Hg2+, while extractability of all cations was observed with compound L2 containing double diazo groups.

ISSN:0736-6299    

DOI:10.1080/07366299708934507

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The synergistic extraction of cadmium and zinc, from 1M NaN03 aqueous solutions, with the acidic chelating extractant 3-phenyl-4-benzoylisoxazol-5-one (HPBI), in the presence of the nitrate salt of aliquat 336 (methyl-tri-n-octylammonium nitrate named TOMA.NO3), has been studied in chloroform and toluene. The extracted species are TOMA.M(PBI)3 with M = Cd, zn. The synergistic extraction is described by the following equilibria:

ISSN:0736-6299    

DOI:10.1080/07366299708934508

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The distribution of chromium( VI ) between aqueous solutions and the kerosene solutions of tri-n-octyl-phosphine oxide (TOPO) have been studied at 25 °C and pH 2-4, in which range the predominant forms of Cr(VI) are HCrO4and Cr2O72−. The extraction equilibrium is influenced by the total chromium(VI) concentration, aqueous pH value, and total extractant concentration. The thermodynamic equilibria among all species in the aqueous phase were used for the analysis of distribution data, and the activity coefficients of ionic species were estimated according to Debye-Hiickel or Bromley equation. By numerical method, the complexes of Cr(VI ) with TOPO formed in the organic phase were found to be H2CrO4(TOPO) and H2Cr2O7(TOPO)3. The corresponding extraction constants were 2019 and 3.69× 108, respectively.

ISSN:0736-6299    

DOI:10.1080/07366299708934509

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The distribution of n- and iso-butyraldehydes between tri-n-butyl phosphate(TBP) n-dodecane(nDD) and HNO3were measured. The distribution ratio of n-butyraldehyde in the TBP/nDD and HNO3system was nearly the same as that of iso-butyraldehyde. The distribution ratios of n- and iso-butyraldehydes increased with TBP concentration in the organic phase. The equilibrium constant of the extraction reaction was about 2. In a uranium, neptunium and plutonium separation process, most of the n- and iso-butyra1dehydes fed into theNp separation stepor into thePu/U partition will be left with the TBP solvent. The two compounds will be partly back-extracted to the aqueous phase in the U purification and in the solvent washing steps of the PUREX process.

ISSN:0736-6299    

DOI:10.1080/07366299708934510

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Flat-sheet membranes from poly(vinylidenefluoride) (PVDF) were prepared by the phase inversion process. LiCl was used as a modifying agent. The porosity, maximum pore size and LEPW(liquid entry pressure of water) were determined. Three types of these membranes were tested as a support forn-decanol supported liquid membranes (SLM). Transport of eight amino acids, selected to cover a wide variety of side chains, and of phenylalanine methyl ester through n-decanol SLM were studied. The ability of amino acids to permeates through these membranes depends on the type of flat-sheet PVDF used as a support. An increase in porosity and pore size of the microporous matrix resulted in an increase of amino acids hydrochlorides flux. Strong dependence of amino acids transport on their structure was observed. Fluxes of amino acids with hydrophobic side chains were ˜100 times higher than those found for hydrophilic amino acids. The stability for three SLMs prepared withn-decanol immobilized in PVDF flat-sheet polymers was examined. The life time varied with the type of membrane support Membrane with small pores tends to have a longer life time than those with greater pore size.

ISSN:0736-6299    

DOI:10.1080/07366299708934511

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two synthetic methods for the preparation of spherically granulated titanium phosphates (TiP), as cesium selective exchangers, have been carried out. The first method uses the “ion memory” effect for the formation of specific adsorption sites in the matrix of TiP, whereas the second method results in the preparation of granular titanium phosphate - ammonium molybdophosphate (TiP-AMP) composites by a gel technique. The efficiency of the new materials has been studied in complex systems. The cesium distribution coefficients for some of the sorbents prepared are higher than 40,000 mL/g. It was found that, due to high exchange capacity, regenerability and high selectivity for cesium, TiP materials with “ion memory” effect can be used for radiocesium recovery from ground and surface waters, whereas granular composite TiP-AMP exchangers are useful for the treatment of cesium containing acid nuclear wastes with a high content of background electrolytes.

ISSN:0736-6299    

DOI:10.1080/07366299708934512

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor