Krystyna Prochaska

Interfacial activity of metal ion extractant

The interfacial activity of metal ion extractants is discussed. The interfacial tension isotherms are processed by matching the Szyszkowski equation, and estimation of selected parameters to discuss the interfacial activity of extractants. Results are presented in comprehensive tables and figures. The interfacial activity depends mainly on three different parameters; type of extractant, acidity of the aqueous phase and organic diluent. Strongly acidic extractants and protonated amine reagents exhibit the highest interfacial activity. The solvating reagents and non-protonated amines are on the opposite side of the scale, while the chelating reagents are somewhere in the middle. The acidity of the aqueous phase affects the interfacial activity of extractants, mainly by the ionisation (protonation and dissociation) of extractant molecules. Solvating diluents always decrease the interfacial activity of extractants.

Interfacial activity of model 2-hydroxy-5-alkylbenzophenone oximes and their intermediates

Abstract The interfacial tension at octane/water and toluene/water systems containing 2-hydroxy-5-alkylbenzophenone E and Z oximes, 2-hydroxy-5-alkylbenzophenones, 4-alkylphenols, and 4-alkylphenyl benzoates having different alkyls was determined and interpreted. At toluene/water and octane/water systems the interfacial tension increases as the alkyl length increases and decreases, respectively. Compounds having a branched alkyl exhibit lower surface activity. It was demonstrated that this opposit effect of the alkyl length can be explained by different strengths of the cohesion interactions in the organic phase, and their influence upon the compounds hydrophile lipophile balance. The depth of the hydrophilic group penetration into the aqueous layers seems to be a barrier retarding the rate of copper extraction.

The surface excess isotherms and the mechanism of copper extraction by hydroxyoximes

Abstract Different adsorption isotherms were used to determine the surface excess isotherms for model 4-alkylphenols and 2-hydroxy-5-alkylbenzophenones and their E and Z oximes in octane/water and toluene/water systems and used to discuss the kinetics and the interfacial mechanism of extracting copper from acidic sulfate solutions. The results obtained suggest that the reaction proceeds according to an interfacial mechanism with the formation of the stable 2:1 complex from the intermediate 1:1 complex and the oxime molecule near the interface as the slowest step.

Application of spline functions in calculating the surface excess isotherm according to the Gibbs isotherm

Abstract Spline functions are proposed for computing the surface excess isotherms for the adsorption of 2-hydroxy-5-alkyl-benzophenone oximes at toluene/water and octane/water interfaces. The proper choice of boundary conditions, sub-intervals and type of the functions used to compute the first derivative is discussed. The spline functions give the values of the surface excess which can then be used in describing the kinetics and mechanism of copper extraction by hydroxyoximes.

Kinetic and equilibrium studies of the removal of cadmium ions from acidic chloride solutions by hydrophobic pyridinecarboxamide extractants.

Liquid-liquid extraction of cadmium(II) from acidic chloride solutions was carried out with alkyl derivatives of pyridinecarboxamide in toluene with addition of 2-ethylhexan-1-ol as modifier. Equilibrium as well as kinetic studies was performed. The kinetic studies of a Cd(II) extraction process were carried out with a Lewis cell having a constant interfacial area. Cadmium(II) concentration in the aqueous phases was determined by atomic absorption spectroscopy (Varian SPECTR AA800). The results of equilibrium experiments showed that cadmium(II) was quantitatively extracted with N,N-dihexylpyridine-3-carboxamide whereas the derivative N,N-dihexylpyridine-2-carboxamide was not able to transfer Cd(II) ions from the aqueous phase to the organic one. Thus, the kinetics of extraction and the initial extraction rate were examined only in the systems with N,N-dihexylpyridine-3-carboxamide. The obtained experimental data as well as the calculated values of mass transfer coefficients suggest that the investigated process of extraction of Cd(II) by means of pyridinecarboxamide as extractant occurs in the mixed diffusion-kinetic region. Moreover, the results of adsorption studies indicated that the extraction of Cd(II) with a hydrophobic extractant should be considered as an interfacial process.

Interfacial behaviour of LIX 65N and surface kinetics of copper extraction

Abstract Different adsorption isotherms such as the Szyszkowski, Temkin, Frumkin, polynomial and the spline function were used to match the experimental interfacial tension isotherms for LIX 65N. In systems containing solvating diluents, agreement was observed between the surface excess isotherms computed according to different adsorption isotherms. However, in systems containing nonsolvating diluents, distinct maxima were observed in the surface excess isotherms computed according to the Gibbs isotherm and the polynomial. Those functions showing distinct maxima can be used to describe further the degree of association (3-1.5) in the organic phase. Adsorption parameters determined for systems containing Escaid 100 and the character of the surface excess isotherm are similar to those obtained in the systems containing toluene. Thus Escaid 100, which is largely aliphatic, exhibits aromatic behaviour at an interface. The surface excess isotherms were computed and used to predict reaction orders for LIX 65N reacting with copper in an interface reaction. The reaction order of 1 was obtained for the formation of the stable 2:1 complex. The adsorbed intermediate 1:3 complex reacting with a hydroxyoxime molecule from the sublayer was considered to be the slowest step. Predicted reaction orders will only be slightly affected by hydroxyoxime association.

Studies on the kinetics and equilibrium of the solvent extraction of chromium(III) from alkaline aqueous solutions of different composition in the system with Aliquat 336

The kinetics and equilibrium of Cr(III) extraction with Aliquat 336 from the alkaline aqueous solutions containing anions of various complexing abilities and solvating properties, as: nitrates, or perchlorates, or sulphates, were studied and interpreted. Stoichiometry of Cr(III) complexes formed in the organic phases was also discussed. It was found that under the same conditions the yield and the rate of Cr(III) extraction as well as values of mass transfer coefficient increase in the following order of anions: perchlorates<nitrates<sulphates. The equilibrium of extraction of Cr(III) in the systems with nitrates and/or perchlorates differs significantly from that one established for the extraction of Cr(III) from the alkaline aqueous solutions of sulphates. Experiments with the modified Lewis cell and analysis of the experimental data by mathematic models appeared that the studied extraction of Cr(III) occurs in the mixed diffusion-kinetic regime, irrespective of the kind of anions present in the aqueous phase.

Physicochemical properties of cross-linked and acetylated starches and products of their hydrolysis in continuous recycle membrane reactor

The aim of the present work was to study the physicochemical properties of doubly modified, by cross-linking and acetylating, starches as well as the products of their enzymatic hydrolysis. A two step procedure of hydrolysis, including the batch and membrane reactors, were investigated. The second step of enzymatic processes were carried out in a continuous recycle membrane reactor (CRMR). Three kinds of commercial starches--two preparations of acetylated distarch adipate E1422 of different degrees of cross-linking, as well as one preparation of acetylated distarch phosphate E1414 were examined. It was found that the degree of substitution of acetyl groups in the macromolecules of starch did not influence the effectiveness of hydrolysis. However, the degree of cross-linking with adipate groups slightly decreased the efficiency of processing in the CRMR. Additionally, the relationship between the type of hydrocolloid and its adsorption activity in the air/water and oil/water systems was considered. All obtained derivatives revealed adsorption properties and reduced the surface/interface tension in the air/water and oil/water systems. The efficiency and effectiveness of adsorption of the investigated hydrocolloids were affected by the type of modification as well as the degree of substitution of acetyl groups in the macromolecules of starch. Particle size distributions formed in aqueous solutions for all investigated hydrolyses were determined and compared with results obtained for commercial products.

ADSORPTION OF EXTRACTANTS AND MODIFIERS IN MIXED BINARY MODEL SYSTEMS

ABSTRACT The interfacial activity of 2-hydroxy-5-l-butylbenzophenone (E)-oxime (HBBO), two model a-acyloin oximes: 9-hydroxy-8-hexadecanone oxime (HHO) and 13-hydroxy-12-tetracosanone oxime (HTO), and a model modifier such as p-tertbutylphenol (BPh) is investigated at toluene/ water interface, at 21°C. Interfacial tension isotherms for individual compounds as well as for binary mixed solutions are obtained. In particular, it is shown that in all mixed systems co-adsorption is observed. Composition of mixed adsorption monolayer is affected mainly by mutual efficiency of adsorption of surface active components and composition of the bulk solution phase.

Nanofiltration, bipolar electrodialysis and reactive extraction hybrid system for separation of fumaric acid from fermentation broth.

A novel approach based on a hybrid system allowing nanofiltration, bipolar electrodialysis and reactive extraction, was proposed to remove fumaric acid from fermentation broth left after bioconversion of glycerol. The fumaric salts can be concentrated in the nanofiltration process to a high yield (80-95% depending on pressure), fumaric acid can be selectively separated from other fermentation components, as well as sodium fumarate can be conversed into the acid form in bipolar electrodialysis process (stack consists of bipolar and anion-exchange membranes). Reactive extraction with quaternary ammonium chloride (Aliquat 336) or alkylphosphine oxides (Cyanex 923) solutions (yield between 60% and 98%) was applied as the final step for fumaric acid recovery from aqueous streams after the membrane techniques. The hybrid system permitting nanofiltration, bipolar electrodialysis and reactive extraction was found effective for recovery of fumaric acid from the fermentation broth.