Solvent effect on distribution ratio of Pd(II) in supercritical carbon dioxide extraction and solvent extraction using 2-methyl-8-quinolinol

The distribution ratio (D_M) of Pd(II) by the extraction with 2-methyl-8-quinolinol (HMQ) was determined using the supercritical carbon dioxide medium (SF-CO₂) and organic solvent media such as perfluoro-methylcyclohexane, heptane, cyclohexane, carbon tetrachloride and benzene. From experimental results of the slopes of log D_M versus pH plot and log D_M versus HMQ concentration plot, the extracted species both in the SF-CO₂ extraction (SFE) and the solvent extraction (SE) were determined to be Pd(MQ)₂. The distribution constant of HMQ (K_D,HMQ) in the SFE and SE systems were determined from the dependence of the distribution ratio of HMQ (D_HMQ) on the pH. A linear relationship was observed between log K_D,HMQ and the solubility parameter (δ) of the extraction medium based on the regular solution theory in both the SFE using SF-CO₂ at the pressure of 8.5–40 MPa and the SE systems. The difference in the slope of the log K_D,HMQ versus δ plot between the SFE and the SE systems is attributable to the extent of the specific interaction of the solute HMQ with the solvent molecules, i.e. CO₂ molecules and the organic solvent molecules. The D_M versus δ plot obtained under a given extraction condition using SF-CO₂ (11–40 MPa) and organic solvents showed clear linearity. The D_M obtained using SF-CO₂ at relatively low pressure range from 8.5 to 11 MPa was independent of the pressure and the δ of SF-CO₂, which coincides with the experimental fact that the solubility of Pd(MQ)₂ in the SF-CO₂ at 8.5–11 MPa was practically constant.     

Supercritical carbon dioxide extraction equilibrium of gallium(III) with 2-methyl-8-quinolinol and 2-methyl-5-butyloxymethyl-8-quinolinol

This work performed fundamental studies for the extraction of gallium(III) with 2-methyl-8-quinolinol (HMQ) and 2-methyl-5-butyloxymethyl-8-quinolinol (HMO(4)Q) into supercritical carbon dioxide (SF-CO(2)) from a weakly acidic solution. The distribution constants of HMO(4)Q between aqueous and SF-CO(2) phases were determined at 45 degrees C, 8.6-20.4 MPa and I=0.1 M (H, Na)NO(3) (M=mol dm(-3)). At 45 degrees C and 15.7 MPa, gallium(III) was hardly extracted with HMQ into SF-CO(2), but was quantitatively extracted with HMO(4)Q in the pH range of 2.20-2.84. The extraction constant, K(ex, SF-CO(2)) (=[Ga(OH)(MO(4)Q)(2)](SF-CO(2))[H(+)](3)[Ga(3+)](-1)[HMO(4)Q](SF-CO(2))(-2)), of gallium(III) with HMO(4)Q was determined to be 10(-2.6+/-0.1) at 45 degrees C, 15.7 MPa and I=0.1 M (H, Na)NO(3), which was 63 times larger than that in heptane at 45 degrees C and 0.10 MPa. It was also found that the addition of 3,5-dichlorophenol as a synergist enhanced the extractability of gallium(III) with HMO(4)Q into SF-CO(2).     

Steric effects in tin-phenyl cleavage by substituted 8-quinolinol

A series of compounds of the type Cl₂Sn(Ox′)₂ (where Ox′ is a substituted 8-quinolinolate) have been prepared by tin-phenyl cleavage of diphenyltin dichloride at 180°C. The kinetics of the reaction have been studied with 2-methyl-8-quinolinol and diphenyltin dichloride in dimethyl sulfoxide at 192° and compared with the kinetic pattern using 8-quinolinol. Kinetics with both chelating agents follow pseudo-first order rate law: rate = (k₁ + k₂[HOx′]ⁿ[(C₆H₅)₂SnCl₂]). Both show a mass-law retardive effect with added tetramethylammonium chloride. The values of n also differ; 2 for 8-quinolinol and 1 for the 2-methyl derivative. The evidence for incursion of steric effects and the significance is considered.     

Catalytic effects in solvent extraction

Catalytic phenomena in solvent extraction of metals with hydrophobic chelating extractants are reviewed. Interface modification by adsorption of additives, phase transfer catalysis, formation of micelles, reversed micelles and microemuslions are discussed and examples are given.     

The solubilities of zinc complexes of 8-quinolinol and some derivatives of 8-quinolinol

The solubilities of bis-8-quinolinolo-zinc^II, bis-2-methyl-8-quinolinolo-zinc^II and bis-5 : 7-dibromo-S-quinolinolo-zinc^II have been measured over the pH range of 4.5 to 9 at ionic strengths of 0.114 and 0.230 and at 25° and 40°. A mathematical treatment of the results gave nearly constant solubility products only when a dissolved but undissociated molecule, in addition to all of the dissociated and partly dissociated species, was considered. The relative abundance of each species of molecule in solution has been calculated.     

Effect of salts on the partition of 8-quinolinol

The effect of inert salts on the partition of 8-quinolinol between benzene and water was determined. For the salts investigated, the relation log K(D') = I + k(3),mu was demonstrated, as expected from the Setschenow equation. The salting out order observed is KCl > NaCl > KNO(3) > NaClO(4).     

7-硝基-8-羟基喹啉的合成

以8-羟基喹啉为原料,经硝化和脱磺酸基保护两步反应合成了7-硝基-8-羟基喹啉,总收率69％,纯度高于99％.其结构经1H NMR,13C NMR和HR-MS确证.     

Effect of pore size on the capacity of sislca-immobilized 8-quinolinol

Optimization of the pore sizes of various silica gels used as supports in the immobilization of 8-quinolinol is described. Increased capacity is observed as pore size decrease to the opt? at about 6 nm. At smaller pore sizes, steric effects appear to predominate, ? capacities decrease sharply. An explanation for these effects is proposed, it was confirmed by using molecular models.     

Spectrophotometric determination of ruthenium with 8-quinolinol

A spectrophotometric method is described for the determination of 2–80 μg of ruthenium. The method involves oxidation of ruthenium to ruthenate, addition of 8-quinolinol, adjustment of the pH to 4–6.5, digestion of the complex formed at 85° for 30 min, extraction with chloroform, and measurement of absorbance at 430 nm. Almost all other metals and excess of reagent are removed by washing the extract. About 98 % of ¹⁰⁶Ru tracer was recovered.     

Temperature effects on the synergistic solvent extraction of cobalt(II)

The extraction of Co²⁺ from a 0.1M ionic strength acetate buffer by acetylacetone, and a mixture of acetylacetone and pyridine or triethylamine was investigated at various temperatures. The enthalpy and entropy change data for the synergistic extraction support a model in which the Co²⁺ ion in the acetylacetonate complex expands its coordination number from four to six in order to accomodate the two N-base molecules. The steric hindrance caused by triethylamine is also reflected in the thermodynamic data.     

Thermal analysis of iron-8-quinolinol complexes

Thermal analysis studies were performed on the iron-8-quinolinol complexes Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(OH)₂ and Fe(Ox · HCl)₂Cl₃ (where Ox is 8-quinolinol). Mixtures of these complexes with Fe(OH)₃ and Fe₂O₃ were also investigated.

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Zusammenfassung Thermoanalytische Untersuchungen der Eisen-8-Oxy-Chinolinkomplexe wurden für Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(Ox)₂ und Fe(Ox · HCl)₂Cl₃ (Ox=8-Oxy-Chinolin) durchgeführt. Gemische dieser Komplexe mit Fe(OH)₃ und Fe₂O₃ wurden ebenfalls untersucht.

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Résumé Etude par analyse thermique de complexes du fer avec l'hydroxy-8 quinoléine: Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(Ox)₂ et Fe(Ox · HCl)₂Cl₃ (où Ox est l'hydroxy-8 quinoléine), ainsi que de leurs mélanges avec Fe(OH)₃ et Fe₂O₃.

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-8- , Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(OH)₂ u Fe(Ox · HCl)₂Cl₃, Ox — 8- . Fe(OH)₃ Fe₂O₃.

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The authors wish to thank Dr. A. Calusaru for his valuable suggestions.     

Synergistic effects in the solvent extraction of zinc with salicylaldoxime

The extraction of zinc with salicylaldoxime was studied. The adduct-forming tendency of zinc salicylaldoximate with pyridine, alpha-picoline, beta-picoline, quinohne and isoquinoline was also investigated. This tendency decreases in the order beta-picoline > pyridine > alpha-picoline > isoquinoline > quinoline.     

Rare earth chelates derived from 8-quinolinol

The composition and heat stabilities of trivalent lanthanide oxinates prepared by homogeneous precipitation (urea hydrolysis in the presence of acetic acid) have been studied. The products contain acetate ion; and the molar ratio oxinate/metal is less than three. Polymeric structures are proposed for these materials, Heat stability in an inert atmosphere, as determined by thermogravimetric, thermomanometric and differential thermal analyses, decreases with increasing atomic weight of the metal.     

Citrate complexes of tin(IV) studied by liquid-liquid extraction with 5,7-dichloro-8-quinolinol

The tin(IV)/5,7-dichloro-8-quinolinol/chloroform extraction system is used to determine the composition and the stability constants of the aqueous complexes of tin(IV) with citric acid, in the pH range 2.0–3.5. The tin(IV):citric acid ratios found are 1:1 and 1:2, depending on the concentration of the acid. The conditional stability constants are (5.5 ± 0.4) × 10³ and (1.3 ± 0.3) × 10³ for the 1:1 and 1:2 complexes, respectively. This extraction system is convenient in studies of aqueous tin(IV) complexes that cannot be extracted into chloroform.     

Recycle effects on solvent extraction through concurrent-flow parallel-plate membrane modules

The recycle effects on membrane extraction through a parallel-plate module with concurrent-flow first and then countercurrent flow, has been studied. Theoretical predictions are in agreement with the experimental results. Considerable improvement in performance is obtainable if membrane extraction is operated with recycle which provides the effect of increasing fluid velocity, resulting in decreased mass-transfer resistance. The influences of recycle type on the performance of membrane extraction, as well as on the fixed and operating costs, have been also discussed.     

Solvation effects in the phototautomerization of 7-quinolinol

Some aspects of the enol → keto phototautomerization of 7-quinolinol in methanol have been re-examined. The results show that phototautomerization only occurs in suitably solvated enol tautomers.     

Solvent effect on the intramolecular hydrogen bond in 8-quinolinol N-oxide

Solvent effect on intramolecular hydrogen bond in 8-quinolinol N-oxide has been studied by IR, UV,¹H NMR and¹³C NMR spectroscopy, dipole moment measurements and quantum-mechanical calculations. The solute-solvent interactions are of local character and they vary considerably over the range of solvent under study. The results suggest that formation complexes with solvent molecules weaken the intramolecular hydrogen bond in 8-quinolinol N-oxide.