摘要:

A simple correlation has been observed between the extraction of cesium nitrate from nitric acid solution by several macrocyclic polyethers dissolved in any of a variety of oxygenated, aliphatic diluents and the concentration of water present in the organic phase. This correlation is attributed, in part, to the extraction of the hydrated nitrate anion and its solvation by the diluent, facilitated by the high concentrations of dissolved water. Cation solvation by the diluent is also shown to play an important role in determining the efficiency of extraction. As was the case for strontium extraction by dicyclohexano-18-crown-6 and its derivatives, the highest distribution ratios for cesium are typically obtained for C-5 and C-6 alcohols and ketones.

ISSN:0736-6299    

DOI:10.1080/07366299608918323

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Selective partitioning of uranyl from transuranic elements in a solvent extraction system which employs a neutral organophosphorus extractant and an aqueous complexant has been demonstrated in a previous report. The extractant solution combines octyl(phenyl)-N,N-diisobutylcarbamoylrnethylphosphine oxide (CMPO), diamyt(amyl)phosphonate (or tributylphosphate), and di(t-butylcyclohexano)-18-crown-6 in Isopar L, and is designed for simultaneous removal of strontium, technetium, lanthanides and actinides from radioactive wastes. The aqueous complexant is tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA). In this report, the separation of UO22+from Np(IV), Eu(III), Am(III), and Pu(IV) using the Combined Process Solvent has been optimized. Potentiometric titration and NMR spectroscopic results describe the distribution of THFTCA into the organic phase as a function of acidity and [THFTCA]. Further potentiometric titration experiments have determined the stoichiometry and stability of uranyl complexes in the aqueous phase. The thermodynamic data indicate that the uranyl complexes are anomalously weak which partially accounts for the selectivity. Ternary complexes involving, UO22+CMPO, and THFTCA in the extractant phase also appear to play a role.

ISSN:0736-6299    

DOI:10.1080/07366299608918324

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A pretreatment flowsheet was tested for separating key radionuclide components from the sludge stored in one of the high-level waste tanks (B-110) at the Hanford Site; this sludge resulted primarily from the bismuth phosphate process, which was one of the three major plutonium separation processes used at Hanford. This test involved 1) washing with water, 2) caustic leaching, 3) acid dissolution, 4) separation of transuranic elements (TRUs) by extraction with octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), 5) separation of Sr by extraction with di-t-butylcyclohexano-18-crown-6, 6) separation of Cs from the acid-dissolved sludge solution by treatment with ammonium molybdophosphate (AMP), and 7) separation of Cs from the sludge wash and caustic leach solutions by ion exchange using a phenol-formaldehyde resin (CS-100). The results of the radionuclide separation steps indicated that the proposed flowsheet is a viable approach to pretreating the sludge stored in tank B-l 10.The TRUs,90Sr, and137Cs were separated from the bulk of the sludge components, so that most of the mass of the sludge (containing Al, Bi, Fe, Na, etc.) could be disposed of as low-level waste.

ISSN:0736-6299    

DOI:10.1080/07366299608918325

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The extraction of tracer amounts of Am(III) and Eu(III) from nitrate medium with purified Cyanex 301™ in kerosene was studied. The slopes of logD/pH dependencies for Am and Eu are close to 3 and the logD/extractant concentration dependencies for Am and Eu are close to 2, respectively. The calculated extraction constants are 10−7.85for Am and 10−11.62for Eu at 25°C. Both the extraction constants and the separation factor of Am/Eu decrease with increasing extraction temperature. The extraction enthalpies of Am and Eu are 18.10 kJmol−1and 43.65 kJmol−1, respectively. This extraction system provides a high selectivity for Am(III) over Eu(III) (at 25°C, separation factor SF=5.9×l03) which arises from greater covalent bonding tendency between sulfur donor atom and Am(III) in comparison with Eu(III).

ISSN:0736-6299    

DOI:10.1080/07366299608918326

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The extraction of Pb(II) from 1.0 M KCI media by the commercial extractant Cyanex 302 dissolved in toluene has been studied as a function of the total extractant concentration, the equilibrium pH and the total metal concentration. The influence of bis(2,4,4)-trimethylpentyi)dithiophosphinic acid, one of the minor impurities of Cyanex 302 and also the major component in Cyanex 301, on the extraction of lead has also been examined by studying the extraction of the metal ion by Cyanex 301. Experimental data have been treated numerically by means of the computer program LETAGROP-DISTR, and can be explained by assuming the extraction of the species PbR2(HR), PbL2(HL) and a mixed complex of stoichiometry PbLR(HR), HL being bis(2,4,4-trimethylpentyl)-dithiophosphinic acid, the active component of Cyanex 301 and HR standing for bis(2,4,4-trimethylpentyl)monothiophosphinic acid, the active component of Cyanex 302. The stoichiometric equilibrium constants of the extraction processes are also given.

ISSN:0736-6299    

DOI:10.1080/07366299608918327

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The formation constants of the adducts of tris(l-(2-thienyl) -4,4,4-trifluoro-l,3-butanedionato) lantha-noids(III) with 1- and 2-naphthalenecarboxylic or 1-and 2-naphthaleneacetic acids have been determined by the solvent extraction method at 298K. It has been found that the adducts with naphthalenecarboxylic acid are a little more stable than those with naphthalene-acetic acid irrespective of lanthanoid as similar as the formation of more stable adducts with benzoic acid than with phenylacetic acid reported before. The formation constants of the adducts of several lanthanoid chelates with these four carboxylic acids decreased from lanthanum to samarium and from terbium to lutetium with increasing atomic number, while the constants did not change much in the middle of the series. Such trend has been discussed in the relation to the difference of the coordination number between the lighter and the heavier lanthanoids(III).

ISSN:0736-6299    

DOI:10.1080/07366299608918328

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A mathematical model for recovery of silver from dilute nitrate solutions applying the Rotating Film Liquid Membrane technique was proposed. A 0.06 M solution of tri-isobutylphosphine sulfide (TIBPS) inn-octane was used as membrane liquid and ammonia as a stripping reagent. The model is based on the assumption that a fast chemical reaction between the carrier (TIBPS), dissolved in the feed, and the nitrate and silver ions takes place in a reaction zone - an aqueous layer, adjacent to the feed/membrane interface. It was found that the stripping is the slower step, although the reaction between the silver-TIBPS complex and ammonia is instantaneous. With the aid of the TUTSIM dynamic simulator it was established that at the conditions of the experiments, the mass transfer coefficients in the aqueous films are nearly 10 times higher than the membrane side coefficients, but due to the very high partition coefficient of the silver-TIBPS complex (mc= 1.45*106), mass transfer through the aqueous film is actually the rate controlling step during extraction.

ISSN:0736-6299    

DOI:10.1080/07366299608918329

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Seven different varieties of alfalfa plant tissues were tested for their ability to uptake copper ions from solution. Laboratory experiments were performed to determine the pH profiles, time dependency, capacity of copper uptake and desorption of the metal bound. Also, optimal biomass drying conditions (oven dried and lyophilized) as well as buffering effects on the copper uptake were examined. Differences in the roots and shoots were examined to determine the metal binding properties of seven alfalfa populations. Protein and crude fiber content was determined for all biomasses studied. Most of the biomasses studied showed a high affinity for copper ions as the pH increased from 2 to 6 with optimum copper binding around pH 5.0. Time dependency experiments for copper binding showed a very rapid adsorption of the copper ions by the various alfalfa species. Binding capacity experiments for copper binding showed that the capacities of the shoots are very similar, with African and Ladak germplasms being the highest. Binding capacities for the roots were similar with Malone populations being the highest. Overall, the shoots have higher binding capacity than the roots. As much as 98% of the copper bound to the various species was recovered by treatment with 0.1 M HC1. This innovative technology has great potential for the removal and recovery of heavy metal ions from contaminated waters.

ISSN:0736-6299    

DOI:10.1080/07366299608918330

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The uptake equilibrium of potassium from impure polyols was obtained experimentally on two different H-form ion exchangers: Dowex XZS-1, a homogeneous gel resin and Amberlite 252, a macroreticular ion exchange resin. The equilibrium isotherms are highly favourable for both types of resins and an acid'base neutralization reaction is proposed to explain the behaviour of the system. It was observed that these resins are not able to exchange their full potential capacity in pure potyol media. Based on the main properties of the resin matrix and the potyol, an explanation about this lack of capacity is proposed. Equilibrium isotherms of potassium from ternary mixtures polyol-methanol-water over Amberlite 252 were also obtained. A different mechanism for ion exchange of potassium was proposed for this kind of system, explaining the improvements inresin capacity.

ISSN:0736-6299    

DOI:10.1080/07366299608918331

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The isotopic exchange rate of Cs+between hydrous niobium(V) oxide in the Cs+form and aqueous solutions was determined radiochemically. The rate was controlled by the diffusion of Cs+in the exchanger particle at varying pH. The diffusion coefficients at 10°C increased with pH up to pH7; from 3.0x10−11m2s−1at pH6 to 4.0×10−11m2s−1at pH7, and became constant above pH8 (5.0x10−11m2s−1). While the diffusion coefficients of Na+monotonously decrease with increasing pH; from 7.9×l0−11m2s−1at pH6.5 to 2.8×l0−11m2s−1at pHll. The difference in the dependence of diffusion coefficients on pH between Cs+and Na+was interpreted in terms of strength of interaction between counterions and ion-exchange sites since hydrous niobium(V) oxide has selectivity higher for Cs+than for Na+.

ISSN:0736-6299    

DOI:10.1080/07366299608918332

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor