Interfacial behavior of primary amine N1923 and the kinetics of thorium(IV) extraction in sulfate media

The influences of additive, diluents, temperature, acidity of the aqueous phase on the interfacial behavior of primary amine N1923 in sulfate media have been investigated using the Du Nouy ring method. In addition, the effect of concentration of thorium(IV) loaded in the organic phase on the interfacial tension has also been studied. The interfacial tension isotherms are processed by matching different adsorption equations such as the Gibbs and the Szyszkowski. The surface excess at the saturated interface (Gamma (max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C-min) under different conditions are calculated according to two adsorption equations to be presented in comprehensive tables and figures. It appears that primary amine N1923 has strong interfacial activity and behaves very differently in various diluents systems. The surface excess at saturated interface increase with the type of diluerits in the following order: chloroform < aromatic hydrocarbons < aliphatic hydrocarbons. The relationship between the interfacial activity and kinetics of thorium extraction by primary amine N1923 has been discussed by considering different factors. However, the interfacial activity of primary amine N1923 is only a qualitative parameter suggesting the interfacial mechanism for thorium extraction, it cannot give strong evidence quantitatively supporting this mechanism.

Hydrothermal synthesis of ZrW2O8 nanorods

Negative thermal expansion ZrW2O8 nanorods were synthesized by a rapid low-temperature hydrothermal route, followed with a heat treatment at 500 degrees C for 6h. Acidity of the HCl addition to the mixed solution in the hydrothermal condition strongly affects the formation of the precursor ZrW2O7(OH)(2)(H2O)(2). High acidity of HCl in the range of 5-10 N facilitates the nucleation of ZrW2O7(OH)(2)(H2O)(2), but constrains its growth. Low acidity of HCl addition (< 5 N) only obtained the products ZrO2 and WO3 by firing the precursors. FE-SEM images revealed that the shape and size of ZrW2O8 were modeled after its precursor ZrW2O7(OH)(2)(H2O)(2).

Extraction and separation of cadmium(II), iron(III), zinc(II), and europium(III) by Cyanex302 solutions using hollow fiber membrane modules

The mass transfer behaviors of Cd(II), Fe(III), Zn(II), and Eu(III) in sulfuric acid solution using microporous hollow fiber membrane (HFM) containing bis(2,4,4-trimethylpentyl)monothiophosphinic acid (commercial name Cyanex302) were investigated in this paper. The experimental results showed that the values of the mass transfer coefficients (K-w) decreased with an increase of H+ concentration and increased with an increase of extractant Cyanex302 concentration. The mass transfer resistance of Eu3+ was the largest because K-w value of Eu3+ was the smallest. The order of mass transfer rate of metal ions at low pH was Cd > Zn > Fe > Eu. Mixtures of Zn2+ and Eu3+ or of Zn2+ and Cd2+ were well separated in a counter-current circulation experiment using two modules connected in series at different initial acidity and concentration ratio. These results indicate that a hollow fiber membrane extractor is capable of separating the mixture compounds by controlling the acidity of the aqueous solution and by exploiting different mass transfer kinetics. The interfacial activity of Cyanex302 in sulfuric acid solution was measured and interfacial parameters were obtained according to Gibbs adsorption equation.

Synergistic extraction of zinc(II) and cadmium(II) with mixtures of primary amine N1923 and neutral organophosphorous derivatives

Synergistic extraction of zinc(IT) and cadmium(11) from hydrochloric acid solution with primary amine N1923 and neutral organophosphorus derivatives Cyanex 923 and Cyanex 925 is the focus of this paper. Extraction mechanisms are discussed as well as how the acidity of the aqueous phase, the composition of the organic phase, and the experimental temperature affect the rates of extraction of metal ions. Differences between synergistic efficiency of Zn(II) and Cd(II) with mixtures of primary amines N1923 and either Cyanex 923 or Cyanex 925 are observed. The equilibrium constants, the composition, and the formation constants of the extracted complexes as well as the values of the thermodynamic functions are calculated. According to the synergy coefficient formula, the synergy effect on the extraction of Zn(II) is in the following order:N1923 + Cyanex 925 > N1923 + Cyanex 923 This order is reversed in the case of cadmium(II). For the same synergistic system, the extraction rate follows the order: Zn(II) > Cd(II). Furthermore, the stereochemical structures of the various extractants and their effect on metal ion extraction rate are also investigated.

Extraction mechanism of La3+ from hydrochloric acid solution using Cyanex 302

The solvent extraction of La3+ from hydrochloric acid solutions was investigated using his (2, 4, 4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, HL) as an extractant. The effect of equilibrium of aqueous acidity on extraction of La3+ using Cyanex 302 In different diluents was discussed. The effects of extractant concentration and chloride ion on the extraction reaction were also studied. Stoichiometry of the extraction reactions and the nature of metal complexes formed were determined using slope analysis technique and IR measurement.

Solvent extraction of scandium(III), yttrium(III), lanthanum(III) and gadolinium(III) using Cyanex 302 in heptane from hydrochloric acid solutions

The extractions of the selected rare earths (Sc, Y, La and Gd) from hydrochloric acid solutions have been investigated using bis(2,4,4-trimethylpentyl)-mono thiophosphinic acid (Cyanex 302, HL) in heptane as an extractant. The results demonstrate that the extractions of rare earths occur via the following reaction: Sc(OH)(2+) + 2[(HL)(2)]((O)) double left right arrow [Sc(OH)L-2 (.) 2(HL)]((O)) + 2H(+) Y3+ + 3[(HL)(2)]((O)) double left right arrow [Y(HL2)(3)]((O)) + 3H(+) La(OH)(2)(+) + 3[(HL)(2)](O) double left right arrow [La(OH)(2)L (.) 5(HL)]((O)) + H+ Gd(OH)(2+) + 3[(HL)(2)]((O)) double left right arrow [Gd(OH)L-2 (.) 4(HL)]((O)) + 2H(+) The pH(1/2) values and equilibrium constants of the extracted complexes have been deduced by taking into account the aqueous phase complexation of the metal ion with hydroxyl ligands and plausible complexes extracted into the organic phase. According to the pH(1/2) values, it is possible to realize mutual separation among Sc(III), Y(III), La(III) and Gd(III) with Cyanex 302 by controlling aqueous acidity.

Adsorption of heavy rare earth(III) with extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid

In the present paper, the adsorption of thulium(Ill) from chloride medium on an extraction resin containing bis(2,4,4-trimethylpentyl) monothiophosphinic acid (CL302, HL) has been studied. The results show that 1.5 h is enough for the adsorption equilibrium. The distribution coefficients are determined as a function of the acidity of the aqueous phase and the data are analyzed both graphically and numerically. The plots of log D versus pH give a straight line with a slope of about 3, indicating that 3 protons are released in the adsorption reaction of thulium(III). The content of Cyanex302 in the resin is determined to be 48.21%. The total amount of Tm3+ adsorbed up to resin saturation is determined to be 82.46 mg Tm3+/g resin. Therefore, the sorption reactions of Tm3+ from chloride medium with CL302 can be described as: Tm3+ + 3HL((r)) <----> TmL3(r) + 3H(+) The Freundlich's isothermal adsorption equation is also determined as: log Q = 0.73 log C + 3.05 The amounts (Q) of Tm3+ adsorbed with the resin have been studied at different temperatures (15-40degreesC) at fixed concentrations of Tm3+, amounts of extraction resin, ion strength and acidities in the aqueous phase.

Effect of different VOPO4 phase catalysts on oxidative dehydrogenation of cyclohexane to cyclohexene in acetic acid

alpha(1)-VOPO4, alpha(II)-VOPO4 and beta-VOPO4 have been investigated as catalysts for the gas phase oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene with the addition of acetic acid (HOAc) in the feeds in a fixed bed reactor. Different VOPO4 phases showed different acidity and reducibility. beta-VOPO4 phase is more active than alpha(I)-VOPO4 and alpha(II)-VOPO4 in the ODH without acetic acid addition. In the presence of acetic acid, the acidity of the catalyst may play an important role in the ODH process. Due to higher acidity, alpha(I)-VOPO4 phase catalyst gives better catalytic performances than alpha(I)-VOPO4 and beta-VOPO4 for the ODH of cyclohexane by adding of acetic acid in the reactants.

Interfacial behavior of DEHEHP and the kinetics of cerium(IV) extraction in nitrate media

The effects of diluents, temperature, acidity, and ionic strength of the aqueous phase on the interfacial properties of DEHEHP have been extensively investigated using the Du Nouy ring method. In addition, the effect of cerium(IV) concentration loaded in the organic phase on the interfacial tension has also been studied. With the increase of DEHEHP concentration, the value of interfacial tension (gamma) decreases in the studied system, which shows that DEHEHP has interfacial activity as a kind of surfactant. The surface excess at the saturated interface (Gamma(max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C-min) under the different conditions are calculated according to two adsorption equations such as the Gibbs and Szyszkowski functions to be presented in comprehensive tables and figures. The relationship between the interfacial activity of DEHEHP and cerium(IV) extraction kinetics by DEHEHP has been discussed by considering different factors such as the effects of diluents and temperature. However, the interfacial activity parameter of extractant only is a qualitative parameter, but cannot provide strong enough evidence to quantitatively explain the relationship between extraction kinetics and interfacial properties of an extractant.

A new hydrometallurgical process for extracting rare earths from apatite using solvent extraction with P-350

In this paper, a new process is proposed to recover rare earths from nitric acid leaching of apatite without interfering with the normal route for fertilizer production using solvent extraction with dimethyl heptyl methyl phosphonate CH3P(O)(OC8H17)(2) (P-350, B). In the present work, the leaching conditions are studied. In selected condition, apatite was dissolved in 20% (v/v) nitric acid solution at 60-70 degrees C while agitating. The most suitable acidity for extraction is 0.4 M HNO3. More than 98% of rare earths in apatite can be recovered using countercurrent extraction process with six stages when phase ratio = 0.5, and defluorination is unnecessary. The influences of phase ratio, stage number, acidity and salting-out agent on extractabilities Of P-350 are studied. The results show that rare earths can be separated with P-350 from Ca, P, Fe and other impurities. Mixed rare earth oxides (REO) of which purity is more than 95% with yield over 98% can be obtained.

Mass transfer kinetics of yttrium(III) using a constant interfacial cell with laminar flow. Part II. Extraction with Cyanex 272

The yttrium(III) extraction kinetics and mechanism with bis-(2,4,4-trimethyl-pentyl) phosphinic acid (Cyanex 272, HA) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The data has been analyzed in terms of pseudo-first order constants. Studies on the effects of stirring rate, temperature, acidity in aqueous phase, and extractant concentration on the extraction rate show that the extraction regime is dependent on the extraction conditions. The plot of interfacial area on the rate has shown a linear relationship. This fact together with the strong surface activity of Cyanex 272 at heptane-water interfaces has made the interface the most probable location for the chemical reactions. The forward, reverse rate equations and extraction rate constant for the yttrium extraction with Cyanex 272 have been obtained under the experimental conditions. The rate-determining step has been also predicted from interfacial reaction models. The predictions have been found to be in good agreement with the rate equations obtained from experimental data, confirming the basic assumption that the chemical reaction is located at the liquid-liquid interface.

Extraction and stripping of ytterbium (III) from H2SO4 medium by Cyanex 923

The extraction and stripping of ytterbium (III) from sulfuric acid medium using Cyanex 923 in heptane solution was investigated. The effects of extractant concentration, pH and sulfate ion as well as stripping agents, acidity and temperature on the extraction and stripping were studied. The equilibrium constants and thermodynamic parameters, such as Delta H (10.76 kJ(.)mol(-1)), Delta G (-79.26 kJ(.)mol(-1)) and Delta S (292.41 J(.)K(-1.)mol(-1)), were calculated. The extraction mechanism and the complex species extracted were determined by slope analysis and FrIR spectra. Furthermore, it was found that the extraction of Yb (III) from sulfuric acid medium by Cyanex 923 increased with pH, concentration of SO42-, HSO4-, and extractant concentration, and approximately a quantitative extraction of Yb (III) was achieved at an equilibrium pH near 3.0, and the extracted complex was YbSO4(HSO4)(.)2Cyanex923((o)).

Interfacial activity of sec-nonylphenoxy acetic acid and kinetics of yttrium extraction

The interfacial behavior of sec-nonylphenoxy acetic acid (CA-100) at various diluents/(H, Na)Cl interfaces was examined using the Du Nouy ring method. Different adsorption isotherms such as the Gibbs and Szyszkowski were in good agreement with the experimental data. The values of interfacial excess at saturated interface increase in the following order: n-heptane > kerosene > cyclohexane > CCl4 > toluene > benzene > chloroform. The effects of temperature, acidity, and ionic strength of the aqueous phase on the interfacial activity of CA- 100 were also examined. The interfacial-activity data were used to discuss the mechanism and kinetics of yttrium (Y) extraction.

Separation of scandium, yttrium and lanthanum in high-performance centrifugal partition chromatography with S-octyl phenyloxy acetic acid

Separation of scandium(III), yttrium(III) and lanthanum(III) was performed by high-performance centrifugal partition chromatography (HPCPC) employing the stationary phase of S-octyl phenyloxy acetic acid (CA-12). The liquid-liquid extraction behavior of CA-12 for Sc(III), Y(III) and La(III), the acidity of aqueous phase, and the operation conditions of HPCPC were examined. The retention volume (V-R) increased with the order of Y(III), La(III) and Sc(III) accompanied with the elution of the mobile phase in different pH, which is lowered from 4.6 to 2.1.

Determination of mercury with a flow injection quartz tube atomic absorption spectrometry

A method was developed for the determination of micro mercury in the soil, plants and the traditional Chinese medicine using flow injection quartz tube-atomic absorption spectrometry. The effect of the factors such as acidity,. the carrier solution, the flow rate of reductive solution and argon gas, etc. on the determination was studied. When vanadic oxide, nitric acid and sulfuric acid were used to decompose the sample reliable result could be obtained. The characteristic mass of the method is 59 pg, the detection limit is 0.028 mug/L, RSD is < 3.9% and the recovery is in the range of 94% &SIM; 102%.