Thermodynamic Parameters of Solvation and Complexing of Copper(II) Nitrate and Nickel(II) Nitrate in Water + Acetamide Mixtures at 298.15 K

The heats of mixing of aqueous solutions of copper(II) or nickel(II) nitrate in water + acetamide (AA) mixtures in the existing range of amide concentrations have been studied. A rise in the amide concentration enhances solvation more strongly in copper(II) salt solutions. Data are analyzed with reference to previous results on the enthalpies of transfer of the salts studied in water + formamide (FA) and water + N,N-dimethylformamide (DMF) mixtures. Electronic absorbance spectra have been recorded at a fixed electrolyte concentration for all thermochemically studied systems, and a linear correlation has been found between the enthalpy of transfer of Cu(NO₃)₂ and the optical density of the solution. The enhanced solvation of copper(II) nitrate in aqueous acetamide is due to inner-sphere interactions between the cation and acetamide; that of nickel(II) nitrate is more due to outer-sphere interactions.     

Thermochemical characteristics of transfer of copper(II) and nickel(II) nitrates from water to water-formamide mixtures

The enthalpies of mixing of aqueous solutions of copper(II) and nickel(II) nitrates with water-formamide mixtures were measured calorimetrically at 298.15 K in the entire composition range. The standard enthalpies of transfer of the electrolytes from water to water-formamide mixtures were calculated from these data. The shape of the isotherms of transfer of the electrolytes is discussed on the basis of the calculated enthalpies of transfer of individual ions and contributions to these quantities made by universal, chemical, and electrostatic interactions of ions with the solvents.     

Individual solvation numbers around the nickel(II) ion in an N,N-dimethylformamide and N,N-dimethylacetamide mixture determined by Raman spectrophotometry.

Individual solvation numbers around the nickel(II) ion have been determined by titration Raman spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) mixtures at 298 K. The in-plane bending vibration (delta(O=C-N)) of DMF and the stretching vibration (v(N-CH3)) of DMA were used in the present analysis. These Raman bands of solvent molecules shift to higher frequencies upon coordination of the solvent molecules to the metal ion. By analyzing the band intensities of free and bound solvent molecules with increasing concentration of the metal ion, the solvation number around the metal ion can be evaluated. Because the individual solvation numbers of DMF and DMA around the nickel(II) ion in the mixture are determined independently, the total solvation number is obtained as their sum. It was found that the total solvation number remains 6 in all mixtures of the DMA mole fraction x = 0 - 1. Although DMF and DMA have practically the same electron-pair donor capacities, the nickel(II) ion prefers DMF to DMA, and an equal solvation number is attained at x = 0.75. This is ascribed to the solvation steric effect of DMA.     

Thermodynamic characteristics of the formation reactions of nickel(II) glycinates and the solvation of reagents in aqueous ethanol solutions

Enthalpies of complexation reactions between nickel(II) and the glycinate ion in mixtures of water with ethanol containing up to 0.5 mole fraction ethanol were obtained by the calorimetric titration method at 298 K. With increasing ethanol concentration exothermicity of complexation was found to increase slightly for the first coordination step. The results obtained were analyzed from the standpoint of solvation approach based on thermodynamic characteristics of all reagents. It was shown that the main cause of the increase in the exothermicity of complexation reactions is the weakening of ligand solvation with increasing ethanol concentration.     

Biosorption of nickel(II) and copper(II) ions from aqueous solution by Streptomyces coelicolor A3(2)

The biosorption of nickel(II) and copper(II) ions from aqueous solution by dried Streptomyces coelicolor A3(2) was studied as a function of concentration, pH and temperature. The optimum pH range for nickel and copper uptake was 8.0 and 5.0, respectively. At the optimal conditions, metal ion uptake was increased as the initial metal ion concentration increased up to 250 mg l(-1). At 250 mg l(-1) copper(II) ion uptake was 21.8% whereas nickel(II) ion uptake was found to be as high as 7.3% compared to those reported earlier in the literature. Metal ion uptake experiments were carried out at different temperatures where the best ion uptake was found to be at 25 degrees C. The characteristics of the adsorption process were investigated using Scatchard analysis at 25 degrees C. Scatchard analysis of the equilibrium binding data for metal ions on S. coelicolor A3(2) gave rise to a linear plot, indicating that the Langmuir model could be applied. However, for nickel(II) ion, divergence from the Scatchard plot was evident, consistent with the participation of secondary equilibrium effects in the adsorption process. Adsorption behaviour of nickel(II) and copper(II) ions on the S. coelicolor A3(2) can be expressed by both the Langmuir and Freundlich isotherms. The adsorption data with respect to both metals provide an excellent fit to the Freundlich isotherm. However, when the Langmuir isotherm model was applied to these data, a good fit was obtained for the copper adsorption only and not for nickel(II) ion.     

Extraction of lead(II) and copper(II) from salicylate media by tributylphosphine oxide.

Tributylphosphine oxide (TBPO) is proposed as an extractant for the extraction of lead(II) and copper(II) from salicylate media. The optimum conditions were evaluated by varying the experimental parameters, such as the pH, sodium salicylate concentration, tributylphosphine oxide (TBPO) concentration, shaking period and various diluents. The probable extracted species, deduced from log-log plots were Pb(HSal)2.2TBPO and Cu(HSal)2.2TBPO. The extraction took place through a solvation mechanism. The method permits the binary separation of lead(II) and copper(II) from commonly associated elements as well as the mutual separation of lead(II) and copper(II). The method is applicable to the determination of lead(II) and copper(II) in various alloys as well as environmental and pharmaceutical samples.     

Ion paired chromatography of iron (II,III), nickel (II) and copper (II) as their 4,7-Diphenyl-1,10-phenanthroline chelates

A reversed phase ion-paired chromatographic method that can be used to determine trace amounts of iron (II,III), nickel (II) and copper (II) was developed and applied to the determination of iron (II) and iron (III) levels in natural water. The separation of these metal ions as their 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) chelates on an Inertsil ODS column was investigated by using acetonitrile-water (80/20, v/v) containing 0.06 M perchloric acid as mobile phase and diode array spectrophotometric detection at 250-650 nm. Chromatographic parameters such as composition of mobile phase and concentration of perchloric acid in mobile phase were optimized. The calibration graphs of iron (II), nickel (II) and copper (II) ions were linear (r > 0.991) in the concentration range 0-0.5, 0-2.0 and 0-4.0 mug ml(-1), respectively. The detection limit of iron (II), nickel (II) and copper (II) were 2.67, 5.42 and 18.2 ng ml(-1) with relative standard deviation (n = 5) of 3.11, 5.81 and 7.16% at a concentration level of 10 ng ml(-1) for iron (II) and nickel (II) and 25 ng ml(-1) for copper (II), respectively. The proposed method was applied to the determination of iron(II) and iron(III) in tap water and sea water samples without any interference from other common metal ions.     

Preparation of a novel polymeric ligand containing a tetraaza macrocycle supported on polystyrene,and separation of copper(II) and nickel(II)

The novel polymeric ligand containing the tetraaza macrocycle as a pendant group was prepared by the reaction of 2,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,12-tetraene with iodomethylstyrene-divinylbenzene copolymer beads. The content of the ligand in the polymer was 0.75 mmol g⁻¹ under the optimum conditions. The complexation of this polymer with copper(II) and nickel(II) in water under heterogeneous conditions in a batch system showed that it can bind copper(II) selectively by complex formation with the tetraaza macrocycle. The capacity for copper(II) was found to depend on the pH, ionic strength and ethanol content of the sample solutions. Moreover, the separation of nickel(II) and copper(II) was achieved in a column system.     

Nanocomposites of Metallic Silver with Octamolybdate Amine Complexes of Nickel(II) and Copper(II)

Theoretical and Experimental Chemistry - It was shown that interaction of photoreduced octamolybdate amine complexes of nickel(II) and copper(II) with silver(I) nitrate in aqueous solutions leads...     

Behavior of chalcosine in leaching of carbonyl nickel synthesis residues with copper(II) chloride solutions

The behavior of chalcosine in leaching of carbonyl nickel synthesis residues with copper(II) chloride solutions was studied. The chalcosine leaching was examined in relation to the chloride background concentration, and kinetic features of the process were elucidated.     

Nickel(II) complexing with glycylglycine and acid-base equilibria of the ligand in aqueous ethanol solvents

The protonation and dissociation constants of glycylglycine and the stability constants of its complexes with nickel(II) in aqueous ethanol of a variable composition with the ethanol mole fraction ranging from 0.00 to 0.55 are determined potentiometrically at a 0.1 M (NaClO₄) ionic strength and temperature of 298 K. The stability of nickel(II) complexes of glycylglycine is found to grow with an increase in ethanol concentration in a solution. The solvation contributions of reagents into the displacement of complexing equilibria are analyzed. The change in the stability of nickel(II) glycylglycinate complexes is explained by the weakening of ligand solvation in aqueous ethanol.     

Stability of copper(II) complexes with cellulose complexite in water-dioxane mixtures

The complexing properties of cellulose complexite with respect to copper(II) ions in water-1,4-dioxane (DO) mixtures are determined. The stoichiometry and stability constants of copper(II) complexes with the hydroxamic groups of the polymer are determined. The equilibrium speciation diagrams for the complexes at pH 2.0–6.0 are plotted; stereochemical configurations are suggested. The effect of the solvation parameters of the complexite on complex formation is analyzed.     

Stability of copper(II) complexes with nicotinate ion in water solutions of ethanol and dimethyl sulfoxide

The stability constants of copper(II) complexes with nicotinate ion in water–ethanol and water–dimethyl sulfoxide mixtures are determined potentiometrically at 25.0 ± 0.1°C at ionic strength of 0.25 (NaClO4). The stability of the copper(II) nicotinate complex significantly increases with ethanol content in the solution, thus making it possible to control the biologically important process by varying the solvent composition. The increase in DMSO concentration causes a less noticeable rise in stability, with its maximum observed at 0.1 dimethyl sulfoxide mole fractions. A comparative analysis of the findings and stability constants of Cu²⁺ complexes with pyridine-type ligands is carried out. The results are discussed using the solvation thermodynamics approach.     

Extraction and complexing of copper(II) with benzoic acid N,N-dihexylhydrazide

The solubility and acid-base properties of benzoic acid N,N-dihexylhydrazide (BDHH) were studied. The extraction of copper(II), cobalt(II), nickel(II), zinc(II), iron(III), platinum(II), platinum(IV), chromium(III), chromium(VI), palladium(II), and molybdenum(VI) with this reagent was studied. It was shown that BDHH most efficiently extracts copper(II) from ammonia solutions and chromium(VI) from sulfuric acid solutions. In the extraction of copper(II), complexes with the [Cu(II)]: [BDHH] = 1: 1 and 1: 2 stoichiometries were found to form. The structure of the 1: 2 complex was suggested proceeding from its IR spectra. A copper(II) extraction isotherm was plotted.     

Chelating resin containing s-bonded dithizonefor the separation of copper(II), nickel(II) and zinc(II)

Analytical and physicochemical properties of a crosslinked poly (vinyl pyridine) based resin containing dithizone were examined. The resin was further used for the preconcentration of copper, nickel and zinc at batch and column level. Various conditions such as pH, equilibration time, temperature were optimised for the maximum loading of copper, nickel and zinc. The loading capacities of the resin for copper, nickel and zinc were observed to be 0.51, 0.59 and 0.65 mmol g⁻¹ of dry resin respectively. Elution of loaded copper, nickel and zinc from the resin was done by using 0.1 M HCl, 0.1 M H₂SO₄ and 0.1 M HNO₃ respectively. Separation of copper, nickel and zinc in binary and ternary mixtures was achieved without any cross contamination.     

Protolytic dissociation of copper(II) and nickel(II) dipyrrolylmethenates in benzene solutions of acetic acid

Protolytic dissociation of copper(II) and nickel(II) dipyrrolylmethenates in benzene solutions of acetic acid has been studied. The results have completed the knowledge of kinetics of dipyrrolylmethene complexes dissociation in acidic medium. The effect of the nature of complex forming atom, ligand, and other factors on the complexes kinetic stability has been analyzed.     

Extraction of lead(II) from chloride solutions of nickel with mixtures based on tertiary amines

Extraction of lead(II) from chloride solutions of nickel with mixtures of tertiary amines with additions of 2-octanone and bis(2,4,4-trimethylpentyl)phosphinodithioic acid (Cyanex 301) in a diluent was studied. The influence exerted on the degree of the lead(II) extraction by the concentration of chloride ions and ratio of organic phase components was examined. Lead(II) can be virtually quantitatively extracted from concentrated chloride solutions with a mixture of 15% trialkylamine + 15% Cyanex 301, with the subsequent regeneration of the organic phase by its treatment with a concentrated HCl solution. The conditions of almost quantitative and selective extraction of lead from nickel raffinates of the cobalt production at the Kola Mining and Metallurgical Company were found.     

Selective extraction of iron(III) from aqueous nitrate solution in the presence of cobalt(II), copper(II) and nickel(II) ions using bis(delta2-2-imidazolinyl)-5,5'-dioxime.

The feasibility of using bis(delta2-2-imidazolinyl)-5,5'-dioxime (H2L) for the selective extraction of iron(III) from aqueous solutions was investigated by employing an solvent-extraction technique. The extraction of iron(III) from an aqueous nitrate solution in the presence of metal ions, such as cobalt(II), copper(II) and nickel(II), was carried out using H2L in binary and multicomponent mixtures. Iron(III) extraction has been studied as a function of the pH, equilibrium time and extractant concentration. From the extracted complex species in the organic phase, iron(III) was stripped with 2 M HNO3, and later determined using atomic-absorption spectrometry. The extraction was found to significantly depend on the aqueous solution pH. The extraction of iron(III) with H2L increases with the pH value, reaching a maximum in the zone of pH 2.0, remaining constant between 2 and 3.5 and subsequently decreasing. The quantitative extraction of iron(III) with 5 x 10(-30 M H2L in toluene is observed at pH 2.0. H2L was found to react with iron(III) to form ligand complex having a composition of 1:2 (Fe:H2L).     

Spectrophotometric estimation of cobalt(II) with nitrilotriacetic acid

A convenient and efficient method for the estimation of cobalt(II) ions in the presence of other metal ions is described. Interference of metal ions such as iron(II), iron(III), nickel(II), manganese(II), and copper(II) have been investigated. Only iron(III) ions seriously affect this determination. Copper(II) and nickel(II) ions do not interfere if present in a molar-ratio less than 1:2 in the cobalt(II) ion solution. Cobalt(II)-nickel(II) and cobalt(II)-copper(II) binary mixtures can be efficiently analyzed at selective wavelengths.     

Sorption selectivity of cobalt(II), nickel(II), and copper(II) ions by KB-2E macroreticular carboxylic cation exchanger from aqueous-salt solutions of alkali metals

Sorption selectivity of copper(II), nickel(II), and cobalt(II) ions by KB-2E macroreticular carboxylic cation exchanger in the Na-form from dilute solutions was studied in the target concentration range (0.52.6) 103 M. The equilibrium distribution coefficients of Co²⁺, Ni²⁺, and Cu²⁺ were calculated. The role played by hydration of ions in their sorption by KB-2E cation exchangers is analyzed with consideration for IR spectroscopic, thermal analysis, and scanning electron microscopic data.