Fumio Kawaizumi

Separation of La and Ce with PC-88A by counter-current mixer-settler extraction column

Abstract The separation of La and Ce with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (commercially known as PC-88A) from nitrate media was studied with a multistage counter-current mixer-settler extraction column of seven stages developed by the authors. The effect of flow rate ratio of the aqueous phase ( Q w ) to the organic phase ( Q o ) on the separation was studied. The maximum separation was obtained at Q w / Q o =3.2 and the separation degree was 63. Scrubbing of the organic phase was also studied in order to enhance the separation. La was scrubbed from the organic phase with nitric acid at pH 2.7 and the separation degree during scrubbing was 45. Simulations of the extraction and scrubbing processes were carried out and compared with the obtained experimental results. Stripping of Ce was achieved by using 100 mol/m 3 nitric acid. The organic phase was successfully recycled during the experiments without any effect on the extraction efficiency.

Heat-capacity measurements of aqueous solutions of mono-, di-, and tri-saccharides using an isoperibol twin calorimeter

An isoperibol twin calorimeter of dry-shield type was constructed and the specitic heat capacities of D (−)-fructose, D(+)-glucose, D(+)-galactose, D(+)-mannose, D(+)-lactose, D(+)-maltose, and D(+)-raffinose in aqueous solution have been determined at about 303K. The partial molar heat capacity at infinite dilution C ∞ p,2 = C ∞ p,ф was determined by the least-squares application of the relation: mC p,ф = bm + cm 2 . The specific heat capacities of the solutes (except raffinose) in the solid state have also been measured from 270 to 325 K using an adiabatic scanning calorimeter. C ∞ p ,2 and (Δ C ∞ p ,2 = C ∞ p ,2 − C * p ,2 ) are positive for all compounds and increase from mono- to tri-saccharides. The additivity parameters for C ∞ p ,2 of saccharides are different from those for other organic solutes. The results are discussed in relations to other properties such as hydration number and diffusion constant.

Study of drop coalescence behavior for liquid-liquid extraction operation

Abstract Using a video camera, a time course of coalescence was observed for toluene droplets formed at the top of adjacent nozzles in water. Several parameters which may control the coalescence have been investigated, such as concentration of acetone added to toluene, direction of mass transfer, time for attaining contact of the droplets, and flow rate of the continuous phase. The average coalescence times decrease with acetone concentration when acetone is transferred from the dispersed phase towards the continuous phase, and they increase with the time required for attaining contact. At high acetone concentration, oscillation of droplets appears, which restrains the coalescence. The average coalescence time increases when the acetone is transferred from the continuous phase towards the dispersed phase. An attempt has been made to predict coalescence times at low solute concentration (no oscillation) by assuming that the difference of interfacial tension causes the film drainage and leads to the drop coalescence. The agreement between the calculated and experimental values is not sufficiently quantitative but reasonable. For lower solute concentration, calculated coalescence times depend strongly on the time for attaining contact, which is in agreement with our experimental observation.

Extraction of rare earth metals with a multistage mixer-settler extraction column

Abstract Extraction behavior of rare earth metals within a mixer–settler extraction column has been analyzed with the stage efficiency calculated from mass transfer coefficients and interfacial area. The mass transfer coefficient within the dispersed drops is determined from a rigid sphere model by taking into account the residence time distribution of drops, and the coefficient around the drops is calculated by Ranz–Marshalls correlation with the terminal settling velocity of a rigid sphere. The interfacial area of dispersed drops is calculated by the use of correlations for the drop diameter and the holdup of dispersed phase in the mixer–settler extraction column. The calculated results for the separation of samarium and gadolinium with a five-stage mixer–settler extraction column are compared with the experimental results at various agitation speeds and flow ratios between two phases. The extraction behavior in the multistage column is explained by a model based on the hydrodynamics and the mass transfer within the mixer. Effects of the pH value in aqueous phase, the extractant concentration in organic phase and the number of stages on the extraction behavior in the mixer–settler column are also shown.

Partial molar volumes and partial molar adiabatic compressibilities of bipyridine and phenanthroline complexes with Fe(II), Co(II), Ni(II), and Cu(II) and chlorides of these metals

Densities and ultrasonic velocities were measured at 25°C for aqueous solutions of bipyridine and phenanthroline complexes [M(bpy)3]Cl2 and [M(phen)3]Cl2 (M=Fe, Co, Ni, and Cu, bpy=2,2′-bipyridine, and phen=1,10-phenanthroline), and chlorides of these metals. The partial molar volumes V2o and partial molar adiabatic compressibilities Kso were calculated. For the complex ions, [M(bpy)3]2+ and [M(phen)3]2+, electrostatic interactions with the solvent are not nearly as important as effects due to the hydrophobic ligands bpy and phen. The relationship between V2o and Kso of the complex ions and common metal ions are examined.

Partial molar volumes and partial molar adiabatic compressibilities of ethylenediamine complexes in water

Densities and ultrasonic propagating velocities of aqueous solutions of ethylenediamine complexes [Co(en)3]Cl3, [Cr(en)3]Cl3, [Ni(en)3]Cl2, and [Cu(en)2]Cl2 (en=ethylenediamine), as well as the ligand ethylenediamine were measured at 25°C. The infinite dilution values of the partial molar volume V20 and partial molar adiabatic compressibility Ks0 were evaluated. The value of Ks0 of the ligand ethylenediamine is nearly zero. The values of V20 and Ks0 are combined with other interaction parameters, such as the Stokes radii and the viscosity B-coefficients, and their dependece upon the charge number and the stereochemistry of the complex ions is discussed.

Sedimentation potential of complexes of nitroamminecobalt(III) in aqueous solution at 25°C

Sedimentation potentials (SP) were measured for a series of nitroamminecobalt(III) chlorides in aqueous solution. The magnitudes of the sedimentation potentials varied with the number of NO2− ligands in the complexes and a definite positive signal was observed for a neutral complex [Co(NO2)3(NH3)3]0. The division of the partial molar volumes of nitroamminecobalt(III) complexes based on the observed SP values resulted in comparable values of the partial molar volume for the Cl− ion, suggesting no appreciable hydrolysis nor ionic association occur for these nitroammine-cobalt(III) complexes.

Process Development for Recovery of Vanadium and Nickel from Heavy Oil Fly Ash by Leaching and Ion Exchange

A process for recovering V and Ni from oil fly ash and for making the ash harmless has been developed. More than 80% of V and Ni are recovered. This process involves two-step leaching and ion exchange. The first step is leaching with water to dissolve Ni, Mg, Al, and Zn, and acid solution is used in the second step to recover V. The metals Ni and V are separated from other metals in each leached liquor. After neutralization and oxidation of the first liquor, Fe and Al are precipitated and removed from solution. Both Ni and Zn are then loaded on CR20 resin. Nickel can be selectively desorbed from the resin due to a remarkable difference in ion exchange isotherm between Ni and Zn. By using the resin C467, V is selectively separated from the second leached liquor containing V and Fe. The advantage of this separation process is that acidic leachant can be reused, saving separation energy.

Hydration of methyl cellulose

Abstract Measurements of the sound velocity in and density of solutions of methyl cellulose have been carried out at various temperatures (15, 25, 30 and 35°C). The partial molar volume and partial molar adiabatic compressibility of methyl cellulose have been evaluated from these data as a function of degree of substitution, i.e. the average number of OCH 3 groups in a glucose unit. The partial molar volume of methyl cellulose increased with the degree of substitution but it was independent of temperature. The amount of hydration of methyl cellulose was calculated after evaluating the compressibility of the dehydrated methyl cellulose, which was estimated from the temperature dependence of the partial molar adiabatic compressibility. The hydration number of methyl cellulose decreased with the degree of substitution.

Hydration of carboxymethyl cellulose and carboxymethyl dextran

Abstract From the measurements of sound velocity and density of a solution of carboxymethyl cellulose and carboxymethyl dextran, the hydration numbers of these materials were evaluated as a function of the degree of substitution, that is, the average number of CH 2 COONa groups in a glucose unit. The hydration numbers of both carboxymethyl cellulose and carboxymethyl dextran increase with the degree of substitution. The increment of the hydration numbers for both samples is ca. 6.6 per degree of substitution and is interpreted in terms of the increase of the hydrophilic CH 2 COONa group in a glucose unit. A slight difference exists between the hydration numbers of carboxymethyl cellulose and carboxymethyl dextran.