Aleksandra Borowiak-Resterna

New pyridinecarboxamides for rapid extraction of palladium from acidic chloride media

Abstract The extraction of palladium(II) from hydrochloric acid solutions of various concentrations in the presence of different amounts of sodium chloride with various defined alkylpyridinecarboxamides having one or two alkyl groups in the amide substituents at positions 2, 3 or 4 was studied. The hydrophobicity of the studied reagents was characterized by various parameters, including octanol/water distribution coefficient. It was found that the extraction of palladium(II) with monoalkylpyridinecarboxamides depends upon the number, length and position of the alkylamide group. Higher extractions are observed for the derivatives with the alkylamide group at position 3. The extraction of palladium(II) from aqueous 0.1 M HCl with N -dodecylpyridine-3-carboxamide (3-C 12 ) is rapid and the equilibrium is achieved in 30–60 s. The replacement of HCl with NaCl has only a minor effect on the extraction of palladium(II). During the extraction of palladium(II) from acidic solutions, HCl is also transferred to the organic phase. High transfer of HCl is observed for N -dodecylpyridine-3-carboxamide. A spontaneous transfer of palladium(II) to the organic phase is observed. The Vosburgh and Cooper method and the Job method were used to determine the composition of the complexes formed. Complexes with the molar ratio of palladium(II) to the extractant equal to 1:2 (PdCl 2 L 2 ) and 1:1 (Pd 2 Cl 4 L 2 ) are extracted.

EXTRACTION OF COPPER FROM ACID CHLORIDE SOLUTIONS BY N-ALKYL-AND N,N-DIALKYL-3-PYRIDINECARBOXAMIDES

ABSTRACT Model individual N-alkyl-3-pyridinecarboxamidee and N,N-di-alkyl-3-pyridinecarboxamides were synthesized and used for copper(II) extraction from chloride solutions. The stoichiometry of its reaction with copper(II) in chloride media was determined. N-alkyl-3-pyridinecarboxamides are stronger extractanta than N,N-dialkyl-3-pyridinecarboxamides but N-alkyl-3-pyridinecarboxamides and their complexes are slightly dissolved in the hydrocarbon diluents.

EXTRACTION OF COPPER(II) FROM ACID CHLORIDE SOLUTIONS BY N-DODECYL- AND N.N-DIHEXYLPYRIDINECARBOXAMIDES

ABSTRACT N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized. Model individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution. It was found, that pyridine-2-carboxamide forms with copper complexes (CuCl2)x (Ext)2. Remaining amides form with copper complexes CuCl2(Ext)2. Monoalkylamides are not suitable for extraction because they and their complexes are slightly soluble in the hydrocarbon diluents. N,N-dialkylpyridinecarboxamides and their copper complexes are sufficiently soluble in the hydrocarbon phase to carry out extraction. However, they are strong extractants and extract efficiently copper already from dilute chloride solutions ([Cl] = 0.1 M). They extract also significant amounts of copper from concentrated (3-4M) nitrate solutions.

Chemistry and Analytical Characterization of the Effect of Hydroxyoxime Structure upon Metal-Complexing and Extraction Properties

Abstract Hydroxyoximes are well established copper extractants that are used in several high-scale in- dustrial installations for producing cathodic copper from oxide ores. The most economically produced copper is obtained by means of hydrometallurgical processes in which hydroxyoximes are used to separate the copper from iron and to concentrate its aqueous solution. The industrial application of hydroxyoxime extractants and their properties have been discussed in several previous papers. *-I 3 Some comprehensive reviews of the chemistry of transition metal complexes with oximes have been presented. 14 v L5 The kinetics and mechanism of metal extraction with hydroxyoximes were also reviewed. 1.11 13,16 The aim of this work is to review the chemistry of metal extraction with hydrophobic hydroxyoxime extractants, with emphasis upon: (1) the characterization of the composition and stability of hydroxyoxime complexes with metals; (2) hydroxyl group acidity; and (3) pH, values, including the effect of hydroxyo...

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.

Effect of the Alkyl Chain Length in N, N‐Dialkylpyridine‐3‐carboxamides upon their Extraction of Copper(II) from Aqueous Chloride Solutions

Abstract Three nicotinamide derivatives with two butyl, hexyl, or octyl alkyl chains at amide nitrogen were synthesized. These model individual compounds were used for copper(II) extraction from acidic chloride solutions at constant ionic strength I = 1.0. It was found that during the extraction N,N‐dialkylpyridine‐3‐carboxamides form two complexes with copper(II) and chloride ions; these can transfer into the organic phase. In these complexes the molar ratio of copper:chlorine:extractant = 1:2:2 or 1:2:3. The obtained stability constants of N,N‐dihexyl‐ and N,N‐dioctylpyridine‐3‐carboxamides complexes with copper(II) chloride in water are comparable, but N,N‐dibutylpyridine‐3‐carboxamide complexes stability constants are significantly lower. The partition constants of these complexes in toluene–water system depend on amide hydrophobicity, increasing with increasing carbon chain length in N,N‐dialkylpyridine‐3‐carboxamides.

PHOTO-DEGRADATION OF HYDROPHOBIC DERIVATIVES OF PYRIDINECARBOXYLIC ACID AS COPPER EXTRACTANTS FROM CHLORIDE MEDIA

ABSTRACT The photo-stability of 2-ethylhexyl pyridine-3-carboxylate and N,N′-di(2-ethylhexyl)pyridine-3,5-dicarboxamide as the model extractants of copper from chloride media were studied and compared with the photo-stability of di(2-ethylhexyl) pyridine-3,5-dicarboxylate, N,N,N′,N′-tetrahexylpyridine-3,5-dicarboxamide and the hydroxyoxime copper extractants. Also the resistance against the UV light the copper(II) complexes of tested extractants were done. The obtained results of photo-degradation indicate that the UV light degraded amide derivatives and esters of pyridine-3,5-dicarboxylic acid and pyridine-3-carboxylic acid. A comparison of the photo-stability of oximes and derivatives of pyridine-3,5-dicarboxylic acid and pyridine-3-carboxylic acid indicates that all tested derivatives of pyridinecarboxylic acid are more stable than hydroxyoxime copper extractants. The copper complexes of derivatives of pyridinecarboxylic acid are less stable than the copper complexes of hydroxyoxime.

Influence of solvent and counter ion on copper complexes with N -alkyl-pyridine-2-carboxamides as studied by electrospray ionization mass spectrometry

The interactions of copper(II) with N-alkyl-pyridine-2-carboxamides (M) were studied by electrospray ionization mass spectrometry. The influence of solvent and counter ion (Cl−, ClO4−) on the type of ions (complexes) observed was discussed. By cone voltage increase, the fragmentation “in source” of the ions discussed was achieved. In methanol solution containing N-alkyl-pyridine-2-carboxamide (M) and CuCl2 the singly- and doubly charged-ions [M + CuCl]+ and [M2 + Cu]+2 were detected. In acetonitrile solution containing N-alkyl-pyridine-2-carboxamide and CuCl2, the copper(I)-containing ions [M + CH3CN+Cu]+ were formed. The use of Cu(ClO4)2 instead of CuCl2 resulted in more abundant doubly-charged ions in both methanol and acetonitrlile solutions and, for the former solution, the ions containing methoxyl anion, namely [M + CuOCH3]+, were observed. When water was used as a solvent, the abundant ions corresponding to the protonated ligands were formed, while the ions corresponding to copper complexes were characterised by low abundances.