Separation Processes for Actinide Elements

Abstract

Separation processes for the actinide elements are reviewed. The difference in oxidation states for the elements Th through Am provide the basis of their separation techniques. The transplutonium elements require multiplate chromatographic or extraction processes to separate them due to the small chemical differences of the common trivalent states. Ion-exchange and solvent extraction systems useful in laboratory tracer level separations and in multigram plant separations are described.     

Separation of non-sulfonated oil from industrial petroleum sulfonate

Abstract

The non-sulfonated oil in industrial petroleum sulfonate was separated by centrifugal method and extraction method, respectively. The oil separation rates of each method were compared, and the effects of oil separation rates under different conditions on the purity of non-sulfonated oil were investigated. The purity information of non-sulfonated oil separated by different methods was analyzed by infrared spectroscopy. The experimental results showed that the oil separation rate of centrifugation was low, and the oil extraction rate was higher. The purity of non-sulfonated oil separated with alcohol–water solution as extractant was lower, while the purity of non-sulfonated oil separated by water extraction method was the highest, and the extractant was nontoxic and environmentally friendly. Water was preferred as extractant. Solvent ratio, temperature and pressure all had great influence on oil separation rate. The optimum conditions for SL petroleum sulfonate were: solvent ratio 1.5:1, 90?°C, atmospheric pressure, which the oil separation rate was 78.51%; and for DQ petroleum sulfonate, the optimum conditions were: solvent ratio 2:1, 90?°C, atmospheric pressure, which the oil separation rate was 79.86%. Non-sulfonated oil separated by water extraction had the least petroleum sulfonate, followed by ethanol single solvent extraction. Although the extraction efficiency of isopropanol aqueous solution and n-pentane was the highest, the content of petroleum sulfonate in non-sulfonated oil was the highest, which affected the product performance and should not be used.     

Solvent Extraction Equipment Design and Operation: Future Directions from an Engineering Perspective

ABSTRACT

The operation of solvent extraction plants involves optimisation of conditions to minimise loss of solvent and maximise recovery. Because of these competing goals there are a number of different geometries of contactors that have evolved for different services; in the future, lower feed concentration and higher recoveries will lead to a consideration of new ways of contacting the two phases. The potential of some of the newer devices is compared with more traditional contactors

The current methods used for design and scale up of column-type solvent extraction devices are reviewed. This covers both the hydrodynamic factors which determine column cross-section and throughput, and mass transfer performance through the influence of drop size, holdup, mass transfer coefficient, axial dispersion, and drop interactions (coalescence and breakage). The current techniques for scale up are limited and rely on extensive pilot testing before final designs can be confidently achieved. A discussion of the potential for more sophisticated models for performance evaluation is also included.     

Extraction Chromatography Versus Solvent Extraction: How Similar are They?

Abstract

Over the last decade, extraction chromatography (EXC) has emerged as a versatile and effective method for the separation and preconcentration of a number of metal ions. Frequently, EXC is described as a technique that combines the selectivity of solvent extraction (SX) with the ease of operation of chromatographic methods. Despite this, the extent to which EXC actually provides the selectivity of SX and to which solvent extraction data can be used for the quantitative prediction of the retention of metal ions on an EXC column has remained unclear. To address these questions, the extraction chromatographic and solvent extraction behavior of lanthanides using three different acidic organophosphorus extractants bis‐(2‐ethylhexyl) phosphoric acid (HDEHP), 2‐ethylhexyl 2‐ethylhexylphosphonic acid (HEH[EHP]), and bis‐(2,4,4 trimethylpentyl)phosphinic acid (H[DTMPeP])) have been compared. Specifically, the rate and extent of uptake of selected lanthanides by the three extractants have been examined. In addition, the relationship between the volume distribution ratios obtained in the chromatographic and liquid–liquid extraction modes have been compared and their utility in predicting the chromatographic parameter, k′, the number of free column volumes to peak maximum determined.     

Rapid Solvent Extraction of Indium(III) and Its Separation from Gallium(III) and Aluminum(III)

Abstract

Mesityl oxide (4-methyl-3-pentene-2-one) has been used extensively for the solvent extraction separation of several transition elements (l). In the present communication, solvent extraction behavior of indium (III) toward mesityl oxide as a function of HCl or HBr concentrations has been studied and a simple and rapid method for the solvent extraction separation of gallium, indium, and aluminum has been proposed.     

Combined Ion Exchange—Solvent Extraction (CIESE): A Novel Separation Technique for Inorganic Ions

Abstract

In the present paper a novel separation technique for inorganic ions is described. This has been termed combined ion exchange—solvent extraction (CIESE), because it is assumed that both ion exchange and solvent extraction are operative simultaneously to effect the separations. This concept is illustrated with two examples: the separation of iron(III), Co(II), and Ni(II) on the ion-exchange resins Dowex 50 and Dowex 1 using acetone or tetrahydrofuran—hydrochloric acid mixtures, and the separation of uranium from numerous metal ions on Dowex 50, employing as eluent a medium consisting of tetrahydrofuran—nitric acid. Because this separation principle is superior to methods employing the conventional separation techniques of ion exchange in pure aqueous solutions and of common liquid-liquid extraction, it is expected that it will also find application for the solution of other problems encountered in inorganic analytical chemistry.     

Electric and Magnetic Separation via Contactless Suspension of Particles,Droplets, and Bubbles

Abstract

Contactless suspensions of particles, droplets, or bubbles by electric and magnetic fields are used for solid-liquid, solid-solid, liquid-liquid, and gas-liquid separations. Dielectric levitation and magnetohydrostatic separation techniques are two examples. The theoretical relationship existing between these techniques and the methods employed for free levitation of solid objects in vacuum and in midair are examined. Practical systems related to the latter methods as well as systems associated with magnetic and electric separation methods are reviewed.     

Selective Separation and Preconcentration of Total Tin Using Quercetin as Chelating Agent

Abstract

Three methods were developed for rapid and selective extraction of total tin as Sn(IV) using quercetin (H5Q) as chelating agent, prior to its determination by hydride generation atomic absorption spectrometry (HGAAS). H5Q was chemically or physically immobilized onto silica gel or polyurethane foam, respectively, and used for the separation of Sn(IV) by the solid phase extraction (SPE) technique. The SPE methods were compared with flotation technique using the oleic acid as surfactant from H5Q solution in amyl alcohol/kerosene solvent. Elemental analysis, thermogravimetry, spectroscopic measurements (IR, UV/vis and magic angle solid state C¹³‐NMR) were used to characterize the resulting modified extractors. The experimental conditions for efficient extraction of Sn(IV) such as: pH, time of stirring, interfering ions and eluent concentration, were optimized for the batchwise separation process. The tolerance limits of heavy metal ions in the sorption of Sn(IV) were reported. The methods were applied for the determination of total tin in water samples, zinc shots and canned beans after digestive oxidation. The suggested SPE and flotation techniques were found to be accurate and not subject to random error with especial preference to the SPE technique as it is cheaper and simpler.     

Separation Science—A Vital Tool of the Chemical Engineer

Abstract

Separation attempts reach back into the earliest history of mankind. Motivated by necessity, man developed methods of separation which, although crude by our standards, represented ingenious progress. Thus, food and condiment preparation had much to do with the development of processes such as leaching, solvent extraction, crystallization, evaporation, and the like.     

Cycling Zone Extraction

Abstract

Cycling zone separation techniques are extended to extraction systems using a system with discrete transfer and equilibrium steps. Experimentally, the direct thermal mode was used to separate diethylamine from water using toluene as the stationary solvent. A staged theory was developed and used to investigate the effects of the variables. The separation occurs in waves and requires proper spacing of the temperature changes to obtain optimum separation. Agreement between experiment and theory was fair.     

A Data Base for Separations Chemistry

Abstract

Computer retrieval of information related to hydrometallurgical separations from most data bases is limited and is also complicated because the terms solvent extraction, ion exchange, chromatography, etc. have widespread use in a variety of disciplines and widely varying meanings in each. A data base called Separations Science Data Base, designed specifically for retrieval of information needed in chemical separations problems, has been assembled. The indexing is structured in such a way as to allow accommodation of a variety of separations methods (distillation, precipitation, flotation, etc.), but liquid-liquid (solvent) extraction and solid-liquid ion exchange are being emphasized initially. The reference material can be retrieved not only in terms of the standard author, title, source, and date-of-publication entries, but also in terms of the substance separated (both those recovered and those rejected), the separations system and the separation agent used, the matrix from which the separation is effected, and the type of information in the reference.     

Membrane-Based Ethanol Extraction with Hollow-Fiber Module

Abstract

The high energy requirements of the traditional separation of ethanol from fermentation liquors by distillation led us to seek a new energy-efficient separation method. Several alternatives, including absorption, molecular sieves, membrane separation processes, and liquid-liquid extraction processes, have been proposed and investigated (I). One of the most investigated separation techniques during the past few years has been membrane-aided solvent extraction (2–5). This dispersion-free solvent extraction process, which uses microporous membranes, overcomes such shortcomings of conventional liquid extraction as flooding and loadings. On the other hand, a technique with microporous hollow fibers may provide high mass transfer per unit volume since hollow-fiber modules contain an enormous surface area.     

THERMODYNAMICS OF SOLVENT EXTRACTION

ABSTRACT

The fundamental thermodynamic characteristics of aqueous electrolyte solutions and organic solutions which affect solvent extraction are summarized and the influence of metal complexation and hydration on the distribution ratios is discussed. The thermodynamics of extraction systems, including synergistic systems, is reviewed. The influence of structural aspects of the complexing extractant agents on these thermodynamic parameters is also reviewed.     

Rapid Preparation of Environmental Samples by Accelerated Solvent Extraction (ASE)

Abstract

Accelerated solvent extraction (ASE) is suitable for the extraction of PAHs from solid samples, as a sample preparation technique for subsequent analytical techniques. Due to the elevated temperatures and pressures used for ASE considerable time and solvent savings are achieved. The time required is less than 15 min. per sample, and solvent usage is reduced significantly (15 mL per 10 g sample) compared to conventional solvent extraction techniques like Soxhlet extraction. Equivalency of the extraction results are shown by the cornparision of ASE to conventional extraction techniques. ASE has already been accepted by the U.S. EPA, and meets the requirement of SW-846 method 3545.     

Coalescence Extraction: A Novel,Rapid Means of Performing Solvent Extractions

Abstract

We report the development of a novel solvent extraction technique which exploits the coalescence properties exhibited by some solvent combinations at elevated temperatures. The technique allows for instantaneous mixing which approaches the theoretical extraction limit. In the extraction of Pb²⁺ from aqueous solution into either 2,4-pentanedione or glutaronitrile containing dicyclohexano-18-crown-6 (DC18C6), extraction times were reduced from 2 hours to less than 1 minute. The K _ex value for extracting Pb²⁺ into glutaronitrile with DC18C6 as the extractant was determined to be 260. The novel coalescence extraction technique is compared to traditional systems in terms of extraction efficiency, speed of extraction, and feasibility of practical applications.     

UNIVERSAL SOLVENT EXTRACTION (UNEX) FLOWSHEET TESTING FOR THE REMOVAL OF CESIUM,STRONTIUM, AND ACTINIDE ELEMENTS FROM RADIOACTIVE,ACIDIC DISSOLVED CALCINE WASTE

ABSTRACT

The presence of long-lived radionuclides presents a challenge to the management of radioactive wastes. Separation of the radionuclides from the waste solutions has the potential of significantly decreasing the costs associated with the immobilization and disposal of the radioactive waste by minimizing waste volumes. Typically, several separate processes are required for the separation of cesium, strontium, and actinides from radioactive wastes. A novel solvent extraction process, the Universal Extraction (UNEX) process, has been developed for the simultaneous separation of cesium, strontium, and the actinides from radioactive acidic waste solutions. The UNEX process solvent consists of chlorinated cobalt dicarbollide for the extraction of ¹³⁷Cs, polyethylene glycol for the extraction of ⁹⁰Sr, and diphenyl-N,N-di-n-butylcarbamoylmethyl phosphine oxide for the extraction of the actinides and lanthanides. A non-nitroaromatic polar diluent, phenyltrifluoromethyl sulfone, is used for this process. A UNEX flowsheet consisting of a single solvent extraction cycle has been developed as a part of a collaborative effort between the Khlopin Radium Institute (KRI) and the Idaho National Engineering and Environmental Laboratory (INEEL). This flowsheet has been demonstrated with actual dissolved radioactive calcine waste at the INEEL using 24 stages of 2-cm diameter centrifugal contactors installed in a shielded hot cell facility. For the major radionuclides, 99.99% of the ¹³⁷Cs, 99.73% of the ⁹⁰Sr, and >99.9% of the actinides in the initial dissolved calcine feed were extracted and recovered in the high activity fraction. For the stable matrix elements, 12% of the Mo, 0.7% of the Zr, and 2% of the Fe were extracted and recovered in the strip product. The minor components Ba and Pb were quantitatively extracted and recovered in the strip product; 23% of the Mn was also present in this fraction. Very little Al, Ca, Cr, Na, and Ni were extracted into the UNEX solvent.     

General Survey of Adsorptive Bubble Separation Processes

Abstract

In this article we present a general survey of adsorptive bubble separation processes. These separation methods involve the use of selective adsorption at gas-liquid interfaces, the interfaces being generated by gas bubbles in aqueous media. A variety of processes based on this mechanism have been developed, and these methods are described in this review. The underlying concepts in this field are then explored so that the similarities between the methods can be seen. Engineering applications, as well as our own work on analytical applications, are presented. Suggestions are also made as to future potentialities for these adsorptive bubble separation processes. Finally, to place these methods in proper perspective, the techniques are compared to such widely used processes as ion exchange and liquid-liquid extraction.     

KINETICS AND INTERFACIAL PHENOMENA

ABSTRACT

Kinetics and interfacial phenomena in solvent extraction of metal ions are reviewed. The importance of interfacial reactions is discussed. The use of new modern techniques to study extraction is also presented.     

Restoring Solvent for Nuclear Separation Processes

Abstract

Solvent extraction separation processes are used to recover usable nuclear materials from spent fuels. These processes involve the use of an extractant/diluent (solvent) for separation of the reusable actinides from unwanted fission products. The most widely used processes employ tributyl phosphate as an extractant diluted with a normal-paraffin hydrocarbon. During use, the solvent is altered due to hydrolysis and radiolysis, forming materials that influence product losses, product decontamination, and separation efficiencies. In most processes, the solvent is recycled after cleaning. Solvent cleaning generally involves scrubbing with a sodium carbonate solution. Studies at the Savannah River Laboratory have shown that carbonate washing, although removing residual solvent activity, does not remove more solvent-soluble binding ligands (formed by solvent degradation), which hold fission products in the solvent. Treatment of the solvent with a solid adsorbent after carbonate washing removes binding ligands and significantly improves recycled solvent performance. Laboratory work to establish the advantage of adsorbent cleaning and the development of a full-scale adsorption process will be described The application of this process for cleaning the first cycle solvent of a Savannah River Plant production process will be discussed.     

Solvent Extraction and Related Studies on Silver Recovery from Aqueous Solutions

Abstract

The main research in the solvent extraction of silver is exhaustively reviewed, together with relevant data on the metal ion complexation properties in one phase. Such features as the transport of competitive cations through liquid membranes and selectivity in silver extraction are also reviewed. The behavior of organic ligands interacting with silver is analyzed on the basis of the atom type or types directly responsible for extraction/complexation processes.