Experimental Verification of Separation of Ions Using Countercurrent Electrolysis in a Thin,Porous Membrane

Abstract

Countercurrent electrolysis in a porous membrane has been used to separate cations in systems LiCl-NaCl-H₂O, LiCl-CaCl₂-H₂O, LiCl-BaCl₂-H₂O, LiCl-KCl-H₂O, and LiCl-NaCl-KCl-H₂O. The experimental results confirm the relationship between the separation efficiency and the difference in ionic equivalent conductance. Furthermore, the dependence of the separation efficiency on the outflow of the enriched solution and on the convection through the membrane has been verified.     

Rolltruded Poly(Aryl Ether Ether Ketone) (PEEK) for Membrane Applications

Abstract

An investigation of the transport and separation of several permanent gases (CO₂, N₂, CH₄, and H₂) and vapors (H₂O and ethanol) in unprocessed and rolltruded poly(aryl ether ether ketone) (PEEK) thin films has been conducted to evaluate PEEK for membrane applications requiring thermally and chemically stable materials. Transport coefficients and separation factors have been determined at permeation temperatures ranging from 40 to ca. 180°C. The gas transport coefficients were found to increase by up to 30% depending on the processing conditions. Actual separation factors, determined for a CO₂/N₂ gas mixture (24.6 vol% CO₂), were depressed slightly in comparison to the ideal values obtained from pure component data. In contrast, water and ethanol vapor permeabilities declined between 10 and 15% as a result of processing. For a 39.1 wt% vapor mixture of H₂O in EtOH, ideal and actual separation factors, determined at 130°C, were in good agreement. In contrast, order of magnitude improvements in the actual versus ideal separation factors were found for 11.7 and 7.6 wt% mixtures of H₂O in EtOH in both unprocessed and rolltruded PEEK. A comparison with other membranes considered for high temperature vapor dehydrations suggests that PEEK may be an excellent polymer for these applications.     

The Simplified Equation of Separation for the Enrichment of Heavy Water in a Batch-Type Thermal Diffusion Column

Abstract

A simple but precise equation of separation for the enrichment of heavy water in a batch-type thermal diffusion column has been derived with the consideration of a pseudobinary mixture. The experiment has also been conducted for various initial concentrations of D₂O and the results are in agreement with the prediction of the theory.     

Separation of water–isotopes mixture in continuous-flow thermal diffusion columns for recovery of deuterium

The present study deals with the estimation of deuterium recovery from the separation of water–isotopes mixture (H₂O–HDO–D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O–HDO–D₂O system were derived by following the same procedure performed in the previous work. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O and confirmed with the experimental results.     

Experimental Studies on the Separation of Deuterium Oxide in Continuous Thermal Diffusion Column for Low Concentration Range

Abstract

Separation equations for the enrichment of heavy water in a continuous-flow thermal diffusion column have been derived for low-concentration operations. Experimentals on two feed concentrations of the H₂O-HDO-D₂O system have also been conducted, and the results quantitatively confirm the predictions of theory.     

Trace Ions in Countercurrent Electrolysis in a Thin,Porous Membrane

Abstract

The transport of trace ions added to a binary electrolyte system through a porous membrane during countercurrent electrolysis has been studied both theoretically and experimentally. Theoretical models based both on the general transport equations and on the Nernst-Planck equations are presented. Experiments and calculations for the binary system NaCl-H₂O with trace ions Li⁺ and K⁺ were performed. The theoretical model was able to predict the transport phenomena fairly well.     

Countercurrent Electrolysis in a Cell Where Porous Membranes Have Been Connected in Series with Ion-Exchange Membranes. Part 2. Experimental Verification

Abstract

Countercurrent electrolysis in a cell wehre porous membranes have been connected in series with ion-exchange membranes has been studied experimentally for the ternary system NaCl-KC1-H₂O. The number of porous membranes was varied from one to four, and the effect of cationic fluxes on separation was also studied. A comparison between three different kinds of cell arrangements was made, and the present method was found to be the most attractive for practical purposes.     

Separation of Magnesium Chloride from Sodium Chloride in Seawater by the Dense-Phase Technique

Abstract

Experimental results are reported for the solid-solid separation of a mixture of MgCl₂. 6H₂O/NaCl (to be referred to as M/S) using a dense media of such organic solvents as tetrachloromethane, iodomethane, and a combination of these two solvents. The solid M/S mixture to be separated was prepared from two different sources: by evaporating seawater in which the M/S ratio is about 0.14, and by synthesis of the pure salts in which the M/S ratio varied between 0.5 and 1.275, Good separation results are reported for the case of dense-phase separation in which the blend of the two solvents has a specific gravity of 1.9. Recovery was about 95% pure M_gCl₂. 6H₂O from a synthetic mixture having an M/S ratio of 1.0.     

Separation and Purification of Magnesium,Lead, and Neodymium from Dissolver Solution of Irradiated Fuel

Abstract

Magnesium and lead have been identified as tracers for the input accountability of plutonium in reprocessing plants where'as fission product ¹⁴⁸Nd is used as a burn-up monitor. Ion exchange procedures developed for the separation and purification of Mg, Pb, and Nd from the dissolver solution of irradiated fuel for their mass spectrometric analyses are presented. Distribution ratio curves of Pb, Ce, Nd, and Sm in CH₃OH-HNO₃-H₂O medium used in the development of the separation and purification procedure are also shown.     

Synthesis of poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneethynylene)s bearing oligo-ethylene glycols and their gas permeation properties

1,4-Diiodobenzenes bearing oligo-ethylene glycols [IRC₆H₂IR, R = OCH₂CH₂OCH₃ (1a), O(CH₂CH₂O)₂CH₃ (1b), O(CH₂CH₂O)₃CH₃ (1c)] were polymerized with 1,4-diethynylbenzene in the presence of Pd/Cu catalyst to afford poly(p-phenyleneethynylene)s bearing oligo-ethylene glycols (2a–c), respectively. Polymer 2a was insoluble in any solvents, but the other polymers (2b, 2c) were soluble in CHCl₃. The weight-average molecular weights of 2b and 2c were 5.4 × 10⁴ and 9.6 × 10⁴, respectively, and they gave free-standing membranes by solution-casting method. The densities of membranes of 2b and 2c were 1.26 and 1.22 g/cm³, respectively, and their carbon dioxide permeability coefficients were 12.9 and 13.5 barrers, respectively. The CO₂/N₂ separation factor of membrane of 2b was as large as 33.7. Membrane of 3b, which contains triethylene glycols, exhibited higher CO₂ permselectivity, and the CO₂/N₂ separation factor was 50.0.     

Estimation of deuterium recoveries from each component of water-isotope mixture in continuous-flow thermal diffusion columns

The present study deals with the estimation of deuterium recovery from the separation of water-isotope mixture (H₂O-HDO-D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O-HDO-D₂O system were derived. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O. The most important assumption in this work was that the concentrations of each component were at local equilibrium within the thermal diffusion column, i.e. H₂O + D₂O ? 2HDO. It was found that D₂O preferably transfers to the bottom end of the column, while HDO does the same for dilute feed concentration, but then transfers to the top of the column when the feed concentration of D₂O, C_3F, increases to 0.3. The maximum total recovery of deuterium from HDO and D₂O occurs at C_3F = 0.25.     

Phase separation and crystallization in glasses of the lithium silicate system xLi2O · (100 ? x)SiO2 (x = 23.4, 26.0, 33.5)

The phase separation in ultimately homogenized glasses of the lithium silicate system xLi₂O · (100 − x)SiO₂ (where x = 23.4, 26.0, and 33.5 mol % Li₂O) has been investigated. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which provide the maximum dehydration and the removal of bubbles from the glass melt. The parameters of nucleation and growth of phase_separated inhomogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I _st of lithium disilicate crystals in the 23.4Li₂O · 76.6SiO₂ and 26Li₂O · 74SiO₂ glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I _st for the glass of the stoichiometric lithium disilicate composition. It has been established that the crystal growth rate have a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low-temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li₂O-SiO₂ system is compared with that in the glass of the stoichiometric lithium disilicate composition. The inference has been made that the phase separation weakly affects the nucleation parameters of lithium disilicate and has a strong effect on the crystal growth.     

EXTRACTION AND SEPARATION OF HEAVY RARE EARTH(III) WITH EXTRACTION RESIN CONTAINING DI(2,4,4-TRIMETHYL PENTYL) PHOSPHINIC ACID (CYANEX 272)

ABSTRACT

Extraction resins, of the type of Levextrel, (which is a collective term for styrene/divinylbenzene based copolymers of predominantly macroporous structure that contain a selective extractant) are important for the recovery and separation of metal ions, as they combine features of solvent extraction and ion exchange resins. This paper presents the results of the adsorption of heavy rare earth ions (Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(II1)) from hydrochloric acid solutions at 0.2 mol/L ionic strength and 50°C by the extraction resin containing di (2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272) and the chromatographic separation of (Er(III), Tm(III) and Yb(III)). Technological separation products, with purity and yield of Tm₂O3 >99.97%, >80%; Er₂O₃ >99.9%, >94% and Yb₂O₃ >99.8%, >80% respectively, have been obtained from a feed having the composition Tm₂O₃ 60%, Er₂O₃ 10%, and Yb₂O₃ 3%, the others 27%.

The distribution coefficients, extraction equilibrium constants and separation factors have been determined as a function of acidity, loading of the resin and rare earths, flow rates and column ratios. The resolutions and efficiencies of separation of Er/Tm/Yb each other have been calculated. The stoichiometry of the extraction of rare earth ions has been suggested as well.     

Use of Strong Base Organic Anion Exchangers for the Removal of Suspended Alumina Particles in Light Water/Heavy Water Systems

Abstract

A method for the removal of suspended alumina particles from H₂O/D₂O systems has been developed. It is based on the modification of surface charge of the suspended hydrated alumina particles by the addition of sulfate ions and adsorbing them on conventional strong base anion exchanger. 48 ppm of added sulfate has been found to be the required concentration for treating 30 ppm Al₂O_{3 3}D₂O suspensions.     

Polymerization of Cyclophosphazenes with Spriocyclic Methacrylate Containing Substituents

The radical addition polymerization and copolymerization of the cyclophosphazene monomers with spirocyclic methacrylate containing substituents, spiro(2,3-dioxypropylmethacryloyl)tetrachlorocyclotriphosphazene, N₃P₃Cl₄[OCH₂CH(OC(O)=CH₂)O] (1) and spiro((2-methyl-3-oxy-2-(oxymethyl)propyl)methacryloyl)tetrachlorocyclotriphosphazene, N₃P₃Cl₄[OCH₂CMe(CH₂OC(O)=CH₂)CH₂O] (2), has been investigated. In the case of 1, homopolymerization using AIBN as the initiator yielded only cross-linked solids. Copolymerization of 1 with methyl methacrylate was accomplished using VAZO 52 under milder initiation temperature. GPC of copolymer suggested a significant amount of chain transfer. Homopolymerization of 2 gave low isolated yields of the homopolymer but copolymerization with methyl methacrylate yielded the expected copolymers. The reactive chlorine atoms in the copolymers of 2 can be replaced by trifluoroethoxide or methyl amine. Thermal properties of the copolymers were examined by DSC, TGA and pyrolysis mass spectrometry.     

Assembly of a water-insoluble strontium metal–organic framework with luminescent properties

A new strontium metal–organic framework, [Sr₂(BTEC)(H₂O)₄]?2H₂O (1) (H₄BTEC = benzene-1,2,4,5-tetracarboxylic acid), has been successfully synthesized by mixing the starting reagents. The single-crystal structure analysis showed that compound 1 displayed three-dimensional structures containing inorganic motifs with two-dimensional layers pillar-connected through organic linkers and forming water-coordinated neutral framework. Further studies revealed that compound 1 was insoluble in water and that it emitted strong luminescence at approximately 437 nm after dehydration.     

Thermal Parametric Pumping of Air–-SO2

Abstract

The separation of air-SO₂ mixtures in a specially prepared silica gel column has been accomplished using a direct mode thermal parapump. The effect of the number of cycles, pumping cycle time, and operating temperature range and level on the extent of separation has been studied over a wide range of operating conditions. The separation factors obtained were several orders of magnitude greater than those typically reported in the literature for gas-solid systems, and compare favorably with those obtained in liquid-solid systems.     

An inorganic–organic hybrid compound built from polyoxovanadate cluster and Mn (II) complexes

A novel inorganic–organic hybrid compound [Mn(teta)][Mn(teta)(H₂O)₂]₂{V₁₈O₄₂(Cl)}·8H₂O (1) (teta: triethylenetetramine) has been hydrothermally synthesized and characterized by TGA, IR and XPS analysis. Its structure is determined by single-crystal X-ray diffraction analysis. Compound 1 exhibits a rare 2-D planar square lattice (sql net), which was constructed by the well known {V₁₈O₄₂} cluster as node and two distinct Mn (II) complexes, [Mn(teta)] and [Mn(teta)(H₂O)₂], as single/double μ₂-bridging linkers. This type sql net with two distinct Mn (II) complexes is the first example found in polyoxovanadates. The magnetic study shows that there exists antiferromagnetic interaction within 1.     

Solvent-Extraction Behavior of Cobalt(II), Nickel(II), Copper(II), and Palladium(II) with Tri-n-butylphosphate

Abstract

A systematic study of the extraction behavior of cobalt(II), nickel(II), copper(II), and palladium(II) with TBP from thiocyanate system in various ranges of acid concentrations has been performed. The thiocyanate medium leads to enhanced extractions in all these cases compared to those in the previously used chloride medium. For palladium, the chloride and nitrate systems have been critically examined. Sixty-two per cent extraction occurs from 4 M hydrochloric acid using 100% TBP in a single run and the extraction becomes quantitative (>99%) after four successive equilibrations. A simpler method has been proposed for rapid extraction of palladium(II) as the thiocyanate complex. Quantitative extraction occurs in the presence of 1.2% thiocyanate solution from 0.5 to 2 M hydrochloric acid (initial) up to pH 8.0. The extractable species of cobalt(II), nickel(II), copper(II), and palladium(II) from thiocyanate medium are probably similar and of the type [M(CNS)₄]^2? [K·TBP·3H₂O]₂ ⁺ (buffer solution) and [M(CNS)₄]^2? [H·TBP·3H₂O]⁺ ₂ (acid solution). A simple extraction scheme has been worked out for the separation of palladium(II) from iron(III), cobalt(II), nickel, manganese(II), copper(II), and platinum.     

Oxygen and Nitrogen Enrichment in Air by Cycling Zone Adsorption

Abstract

Enrichment of N₂ and O₂ in air has been obtained by cycling zone adsorption in the double zone standing wave mode. The solid adsorbent is molecular sieve type 5 A. The maximum separation factor obtained in these experiments is 10.6 for oxygen.