Separation of Inorganic Salts From Supercritical Water by Cross-Flow Microfiltration

Abstract

A cross-flow microfilter capable of operating at elevated temperatures and pressures was evaluated for its ability to remove inorganic salts from supercritical water (SCW). The separation characteristics of molten sodium nitrate were investigated. The overall performance of the cross-flow microfilter and the effects of process variables on the separation efficiency were evaluated. Separation efficiencies up to 85% were observed. An empirical model was developed for the prediction of the filtrate salt concentration and the fluidized cake resistance as a function of the salt solubility and salt flux to the filter. Physical principles governing the separation process were defined.     

Synergism and Separation Factors in Lanthanide Extraction with Mixtures of Chelating Extractant and Amine Salts in C6H6

Abstract

The solvent extraction of Pr, Gd, and Yb with 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HP) and an amine salt (AmHA) has been studied. The composition of the extracted species has been determined as (AmH)[LnP₄]. The values of the synergistic coefficients and separation factors have been calculated. The effect of the amine salt on the extraction and separation of lanthanides has been discussed.     

Reverse Osmosis Separation of Nickel from Dilute Solutions

Abstract

Cellulose acetate membranes were characterized in terms of the pure water permeability constant, the solute transport parameter, the mass transfer coefficient, and percent solute separation using a reference system of aqueous sodium chloride solution. The membranes were used in the determination of reverse osmosis characteristics such as product rates and solute separation of dilute nickel salt solutions. The effect of the chemical species present in aqueous nickel salt solution on the degree of separation of nickel has been determined. The results of this study can be used in predicting the general reverse osmosis separation behavior of metals such as Zn, Cu, Pb, Mg, and Mn encountered in acid mine-water samples     

Effect of Position of Substitution on the Separation Behavior of Deuterated Toluene

Abstract

The position and number of deuterium atoms substituted onto the toluene molecule was found to affect its separation behavior on a silver nitrate-water column. Substitution on the ring affected the capacity ratio substantially while substitution on the methyl group had no measurable effect. At the same time, the separation behaviors of benzene and perdeuterobenzene were examined using several other salt solutions and polar liquids as possible stationary phases.     

Separation of Fermentation Products by Membrane Techniques. I. Separation of Lactic Acid/Lactates by Diffusion Dialysis

Abstract

The results of the separation of lactic acid from sodium lactate by diffusion dialysis are presented in this paper. Neosepta AFN-7 and Selemion DSV membranes were used for the separation. The dialytic separation factor for lactic acid/sodium lactate was found to be ～20 for Neosepta AFN-7 and ～30 for Selemion DSV membranes. The fluxes inherent in the separation were up to ～1 mol/m²·h for the acid and only up to ～0.07 mol/m²·h for the salt. The effects that enable the separation, i.e., the differences in solubility and diffusivity of the acid and the salt, were estimated (single solute experiments). The partition coefficients for lactic acid were found close to or above unity whereas those for sodium lactate were much lower. On the contrary, the apparent diffusion coefficients of both solutes were comparable, being of the order of 10^?11 m²/s. It results that the separation of the weak acid and salt is based on differences in solubilities rather than in diffusivities, i.e., the phenomenon is different from those which enable separation of strong acids and salts. The results prove the diffusion dialysis technique is effective for separating lactic acid from lactates.     

INFLUENCE OF THE AMMONIUM SALT ANION ON THE SYNERGISTIC SOLVENT EXTRACTION OF LANTHANIDES WITH MIXTURES OF THENOYLTRDJLUOROACETONE AND TRIDECYLAMINE

ABSTRACT

The synergistic solvent extraction of Pr, Gd and Yb with mixtures of thenoyltnfluoroacetone ( HTTA) and primary ammonium salt ( tridecylammonium chloride or perchlorate, TDAH( C1, CI0) in dHhas been studied. The composition of the extracted species have been determined as Ln( TTA)₃ TDAHA( A= CI or CIO⁴ ) The values of the equilibrium constant K_{T. s} have been calculated. The influence of the ammonium salt anion on the extraction process has been discussed. The separation factors of the pairs Gd/ Pr and Yb/ Gd have been determined.     

Electroflotation Studies on Cu,Ni, Zn,and Cd with Ammonium Dodecyl Dithiocarbamate

Abstract

The concentration of Cu, Ni, Zn, and Cd ions by electroflotation using the ammonium salt of dodecyl dithiocarbamic acid as an anionic collector is examined. Quantitative studies reveal better separation efficiency by this method as compared to column flotation using dodecyl dithiocarbamic acid ligand as a chelating surfactant.     

Chelation and Foam Separation of Metal Ions from Solutions

Abstract

An experimental study was conducted on the chelation and foam separation of trace amounts of cadmium, zinc, and lead from their water solutions. The chelation agents ethylenediaminetetraacetate (sodium salt), sodium diethyl-dithiocarbamate, and citric acid were used with sodium dodecylsulfate (SDS) as a foam-producing agent. The chelation agents did not produce metal complexes that were very surface active. The foam-producing agent produced metal ion complexes that were surface active and resulted in appreciable separation of the metal ions. The use of 100 ppm SDS resulted in separation of 90% of the zinc ions from solution containing 2 to 20 ppm zinc. At concentrations below and above this, the removal efficiency dropped significantly     

Separation of Aromatic Carboxylic Acids Using Quaternary Ammonium Salts on Reversed‐Phase HPLC. 2. Application for the Analysis of Loy Yang Coal Oxidation Products

Abstract

In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed‐phase HPLC using eluent containing quaternary ammonium salt was optimized using the solvent gradient method. This method was applied for the analysis of Loy Yang coal oxidation products. It was confirmed that the analytical data using this method were consistent with those determined using gas chromatography.     

Removal of Cadmium from Aqueous Solution Using Adsorptive Bubble Separation Techniques

Abstract

Cadmium ion was removed from aqueous solutions using adsorptive bubble separation techniques. The effect of pH, coagulant and activator concentrations, and ionic strength on separation efficiency was studied. Adsorbing colloid flotation using ferric hydroxide and aluminum hydroxide as the coprecipitant and sodium lauryl sulfate as the collector and frother was found to be very effective provided that the ionic strength of the solution was no greater than 0.01 M. The residual cadmium concentration was less than 0.02 ppm after foaming for 10 min from a solution containing 20 ppm cadmium initially. Effective separation can be achieved from solutions containing 0.1 M NaNO₃ or 0.05 M Na₂SO₄ when zinc ion is used as the activator. The results of foam flotation were compared with the zeta potential of the floc. It was found that the zeta potential of the floc decreases with increasing ionic strength of the solution. The zeta potential of the floc is more positive when activators (aluminum and zinc ions) were added, which presumably gives the floc a stronger affinity for anionic surfactant adsorption, resulting in better separation efficiency. Adsorbing colloid flotation becomes less effective with increasing inert salt concentration of the solution; this effect can be compensated for to quite a large extent with the aid of activators, and the applicability of foam separation techniques for heavy metal removal from wastewater is thus greatly extended     

Demineralization of Protein Hydrolysates from Enzymatic Hydrolysis of Leather Shavings Using Membrane Diafiltration

ABSTRACT

Pressure-driven membrane separations operated in the diafiltration mode appear promising as an efficient demineralization method of waste protein hydrolysates from leather production. The conclusion drawn from our experimental results is that nanofiltration membranes should be used rather then ultrafiltration ones as they show complete passage of the salts with high retention of the protein hydrolysates. In addition to the classical membrane separation operating parameters, which are crossflow fluid velocity, transmembrane pressure difference, and temperature,the required residual salt concentration as well as acceptable protein losses affect the effectiveness of the process.     

Effect of Ring-Size Variation within Dibenzocrown Ether Resins upon Ion-Pair Sorption of Alkali-Metal Cations from Aqueous and Aqueous Methanol Solutions

Abstract

A batch analysis method has been developed for evaluation of metal salt sorption by crown ether polymers. Selectivity in competitive alkali-metal chloride sorption by a series of formaldehyde condensation polymers of dibenzocrown ethers is influenced by the relationship between the crown ether cavity size and metal ion diameter, as well as the degree of hydration of the metal salt. Effective and selective sorption of KCl from the other alkali-metal chlorides was obtained with a dibenzo-18-crown-6 resin. Excellent sorption selectivity for the monovalent metal chlorides was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂, and CaCl₂ by this resin. This resin was examined as a stationary phase for selective column separation of KCl from alkali-metal chlorides and of KCl and NaCl from alkali-metal and alkaline-earth chloride mixtures in 80% methanol—20% water.     

Ion Rejection in Single and Binary Mixed Electrolyte Systems by Nanofiltration: Effect of Feed Concentration

Abstract

The objectives of this work were to investigate and compare the separation behavior of ions in single and binary mixed electrolyte systems by NF70, with emphasis on the effect of feed concentration. Experimental results showed that the anion rejection is lower in the binary mixed system compared to the single salt system. Anion rejection decreases with the enhancement of feed concentration of co‐existing electrolyte. As for cation rejection, Na⁺ rejection in the mixed electrolyte system is generally greater than that in the single NaCl system; whereas the separation performance of Ca²⁺ at high feed concentrations shows the opposite trend, and cannot be explained by the Donnan theory. Several possible mechanisms have been evaluated. Finally, the Spiegler‐Kedem equation was used and parameters were calculated.     

SRS Low‐Curie Process Modeling and Experiments

Abstract

Engineers at SRS are evaluating the Low‐Curie Salt Process which is aimed at initially withdrawing the interstitial liquor followed by dissolution of the salt cake. Partitioning of the cesium is predominantly within the interstitial liquor; consequently a separation based on activity can be effected. Laboratory experiments using simulants from SRS tanks have been performed along with thermodynamic simulations. Results indicate that insoluble layers such as Al(OH)₃ and/or cancrinite may form and hinder the dissolution processes. The effectiveness of the Low‐Curie Salt Process may be reduced based on layer formation and the distribution of the interstitial liquor within the waste.     

Donnan Membrane Effect-Aided Separation of Metal Cyanide Complexes by Hyperfiltration through Cellulose Acetate Membranes

Abstract

Permeation behavior of cyanide complexes of copper, zinc, and silver through cellulose acetate membranes was investigated in the presence of “activating salt” (succinate or polyvinyl sulfate). In hyperfiltration with high-performance membranes (CA-87), both activating salts effectively enhanced the permeability of negatively charged Group Ib metal (I) cyanide complexes (Donnan membrane effect); the phenomenon was caused by selective affinity of these metal cyanide complexes to the membrane phase. However, with low-performance membranes (CA-75) such selective permeations were reduced by a contribution of increased solute-solvent flow, and all the metal cyanide-complexes showed relatively high permeabilities. The polymer-type activating salt, polyvinyl sulfate, did not permeate through the low-performance membrane but showed an effectiveness in enhancing the permeability of the cyanide complexes under low-pressurized conditions. Taking advantage of this, a new technique, a Donnan membrane effect-aided hyperfiltration-ultrafiltration, was developed for selective separation of metal cyanide complexes. A mutual separation of a mixture of silver and zinc cyanide complexes or a mixture of copper and zinc complexes was successfully achieved. The activating salt, polyvinyl sulfate, was recycled and reused in this separation system.     

Application of Extraction Chromatography to Nuclear Fuel Reprocessing

Abstract

The potentialities of applying extraction chromatography to the reprocessing of reactor fuels on an industrial scale have been investigated. The stationary phase was undiluted (100%) tri-n-butyl phosphate (TBP) and the mobile phases were nitric acid or nitrate salt solutions with or without reducing agents for plutonium.

Several extraction chromatographic processes for the recovery of nuclear grade uranium and plutonium are described. The flowsheets are based on a systematic determination of the distribution coefficients of relevant metal species (particularly those of uranium, neptunium, plutonium, americium, ruthenium, zirconium and niobium) in the chromatographic systems employed.

The Purochromex process developed for the recovery of uranium and plutonium from light-water reactor fuels and the Eurochromex process developed for the separation of highly enriched uranium from irradiated U/A1 alloy, U/Zr alloy and uranyl sulfate fuels have successfully been hot-tested on a laboratory scale and cold-tested on an “industrial scale.”

Some complementary studies related to the separation processes. such as radiation degradation of the stationary phase and the removal of tributyl phosphate from product and waste streams, are also described.     

Liquid Salt Hydrate Acid Gas Absorbents: An Unusual Desorption Of Carbon Dioxide And Hydrogen Sulfide Upon Solidification

Abstract

It was recently reported that certain salt hydrate melts can function as pressure swing absorbents for acid gases. The utility of these salt hydrates derives from their large and reversible acid gas absorption capacities. Typical is the salt hydrate tetramethylammonium fluoride tetrahydrate which as a melt absorbs 0.30 mol CO₂/mol salt at 50[ddot]C and 100 kPa CO₂. It has now been discovered that the reactivity of some of these salt hydrate melts with CO₂ and H₂S exhibits an unusual and unexpected temperature dependence. When certain specific salt hydrate melts containing absorbed CO₂ were cooled to temperatures which resulted in solidification, CO₂ was spontaneously desorbed. For example, a sample of tetraethylammonium acetate tetrahydrate (TEAA) containing 0.15 mol CO₂/mol salt at 50[ddot]C and 102 kPa desorbed 90% of its bound CO₂ upon cooling to 26[ddot]C. Gas absorption and desorption are completely reversible, and the absorbent can be cycled by simply raising or lowering the temperature through the point of solidification. Similarly, a sample of TEAA containing 0.30 mol H₂S/mol salt at 50[ddot]C desorbed H₂S upon cooling to 10[ddot]C. A rationale for this unusual temperature-dependent desorption of acid gases from salt hydrates is presented. The modest decrease in temperature required for an abrupt release of gas from TEAA may supply a kind of “on/off” switch for gas absorption which may be of considerable value for the separation of acid gases, particularly H₂S, from process streams.     

Studies on the Separation of Cadmium from Solutions by Foam Separation. II. Precipitate Flotation of Cadmium Hydroxide

Abstract

Foam separation of cadmium in relation to pH from solutions of different metal concentrations was carried out by means of lauryl sulfate. The effect of inert salt on the removal of cadmium hydroxide and cadmium cations by adsorbing colloid floation was also studied. The precipitate flotation results reflect the precipitation of the metal in the form of a hydroxide. The precipitation pH values calculated are approximately those at which cadmium removal over 50% is obtained. The presence of electrolyte has a negative effect on the results of precipitate flotation of cadmium hydroxide and adsorbing colloid flotation of cadmium cations with lauryl sulfate.     

Separation of Immunoglobulins by Potential Barrier Chromatography

Abstract

Potential barrier chromatography is a HPLC method of separating proteins, which is based on the high sensitivity of the interaction potential between adsorbent and adsorbate to factors such as the adsorbate size and adsorbate charge. The interaction potential is composed of van der Waals attraction, and double-layer, Born, and hydration repulsions. Controlling the double-layer repulsion, by changing the pH and the ionic strength, and the van der Waals attraction, by changing the organic content of the eluant, generates sufficiently different adsorption energy wells for the individual proteins to achieve their separation. PBC is exploited in the present paper to separate various immunoglobulins, especially IgA and IgG (which, as it is well known, are difficult to separate), from a naturally occurring mixture of human serum. A fraction more concentrated in immunoglobulins has been first obtained from this mixture by their precipitation with ammonium sulfate. The optimum conditions for the separation of various immunoglobulins from the enriched mixture, by PBC, were: pH = 7.5 and salt concentration ? 0.005 M K₂SO₄. An inexpensive ion-exchange column, conventional HPLC equipment, and an isocratic elution procedure were used. Since this method is based on relatively weak physical interactions between proteins and packing, the duration of separation is small and the likelihood of denaturation is much lower than in other methods.     

Continuous hydrothermal gasification of glycerol mixtures: Effect of glycerol and its degradation products on the continuous salt separation and the enhancing effect of K3PO4 on the glycerol degradation

At the Paul Scherrer Institut (PSI) a continuous process for the catalytic hydrothermal gasification of wet biomass to synthetic natural gas (SNG) has been developed. The catalytic reactor is operated at temperatures of 400–450 °C and pressures of 25–30 MPa. Salts contained in the biomass and released during the liquefaction step are continuously withdrawn in the supercritical salt separation step and recovered as a concentrated brine upstream of the catalytic reactor. The recovered salts may be recycled as valuable nutrients or fertilizers after a certain work-up.Salt management was identified as critical issue in many different hydrothermal processes such as supercritical water oxidation (SCWO) and in catalyzed or non-catalyzed gasification technologies in near- and supercritical water. In this article we focus on the influence of organics, in this case glycerol and its hydrothermal degradation products, on the continuous salt separation performance. In the presence of organics higher temperatures are needed in the salt separator for an efficient salt separation and recovery due to a higher overall fluid density in the presence of glycerol compared to the density of pure water at the same conditions. Increasing temperatures in the salt separator lead to an increased degradation and, in particular, gasification of the glycerol. The salt studied, i.e. K₃PO₄, catalyzed the gasification of the glycerol to CO, H₂, CO₂, and CH₄ as well as the water gas shift reaction. Due to the increased glycerol gasification at 460 °C in the salt separator, the fluid mixture density was lowered to similar values of pure water under the same conditions. Hence, at the fluid temperature of 460 °C in the salt separator the same salt separation performance was observed for water–K₃PO₄ and for an aqueous mixture of 20 wt.% glycerol with K₃PO₄.