The sorption of thiocyanate ions on complex-forming ionites

The ligand sorption of thiocyanate ions on several complex-forming ionites was studied. The ionites were preliminarily transformed into metal forms by saturation with copper(II) ions. ANKB-2 amphoteric ionite in the Cu form had the strongest affinity for thiocyanate ions. The optimum conditions for their extraction were pH ∼ 2 and solution ionic strength 1. IR spectroscopy was used to study the ligand sorption of SCN⁻ ions by ANKB-2 ionite in the Cu form. The stability constants of thiocyanate ionite copper complexes were calculated from formation function [`(n)] \bar n .     

Selective extraction and concentration of dispersed copper from dilute solutions of copper and zinc ions with weakly basic aminoanionites

The possibility of selective extraction and multiple concentration of copper in the form of ultrafine precipitate from dilute Cu²⁺-Zn²⁺ solutions by using a suitable sorbent and an effective mode of its regeneration was demonstrated. The extraction was performed in the dynamic mode in column-type reactors filled with an aminoanionite as a selective complexing sorbent, the regeneration of which was conducted by chemical reduction of Cu²⁺ in the ionite after its saturation. It was established that saturation-reduction cycles repeated many times result in the accumulation of metallic copper at the surface and in the bulk of the sorbent. The mechanism of the process includes the formation of complexes of copper and zinc with amino groups of the ionite and the subsequent displacement of Zn²⁺ ions from the anionite due to its higher affinity to Cu²⁺ ions followed by the conversion of Cu²⁺ ions to an unsorbable form (dispersed metallic copper). It was demonstrated that the presence of dispersed copper stimulates the additional sorption of Cu²⁺ ions via redox conproportionation. This method makes it possible to obtain a degree of concentration of copper ions in three cycles >300% higher than that attainable in the purely ion-exchange mode (without chemical reduction).     

The estimation of the stability of ionite complexes formed in the sorption of copper cations by weakly alkaline AM-7 anionite

The sorption of copper cations by the complex-forming AM-7 anionite was studied. It was shown that the sorption of copper ions from aqueous solutions was satisfactorily described by the Langmuir equation. The linear approximation to this equation can be used to determine the maximum sorption capacity of the complex-forming anionite. Two independent methods for the determination of the characteristics of the ionite complex (the sorption capacity, stability constant, and coordination number) were considered: the determination of the stability constant from the distribution coefficient and from the data on the destruction of ammonia copper complexes brought in contact with the deprotonated ionite form. In both cases, the calculated stability constants of ionite complexes and the coordination numbers are in satisfactory agreement.     

A microcalorimetric study of the sorption of copper(II) on KB-4 carboxyl cationite

The thermokinetics of sorption of copper(II) ions on KB-4 carboxyl cationite in the salt and hydrogen forms was studied microcalorimetrically. The total heat effect of sorption and its dependence on the degree of ionite filling were determined.     

Synthesis of new chelate ionites and some details of their metal ion interaction

The synthetic methods for chelate ionite groups with 8-quinolinol, 8-quinolinethiol and some other thiols, thioethers or thioamides were developed, their sorbing and acid-base properties being studied as well. The stability constants of complexes of metal ions with polymeric chelate groups were determined. A method to calculate the formation function of the complexes on the basis of potentiometric data was proposed. The experiments showed the synthesized sorbents to be applicable in the selective extraction of heavy metal ions from their solutions.     

Influence of Heterogeneity of Ion-Exchange Membranes on the Limiting Current and Current–Voltage Curves

A heterogeneous-membrane model is employed to demonstrate that, following a decrease in the ionite fraction in membranes, true values of limiting currents in electrolytes of different nature are not lower than in a pure ionite, while relative (measured) values drop by 2–5 times, which is explained by a decrease in the conducting surface areas of membranes. The formation of a limiting state on a heterogeneous surface is described qualitatively with allowance made for the morphology of membranes. The region of inflection in experimental and calculated current–voltage curves, which corresponds to a limiting state, is shown to degenerate with a decrease in the ionite fraction in membranes, which is due to the effect the membrane structure has on the polarization. The activation energy of the limiting state is determined.     

The enthalpies of interaction of strongly basic anionites with amino acid ions

The enthalpies of interaction of strongly basic anionites ARA-1p, AV-17-8, and AV-29-12P with glycine, glutamic acid, and tyrosine anions were determined by microcalorimetry. The interaction of ionites with amino acid anions over the selected concentration range was accompanied by heat release. The value and duration of heat release and the enthalpy of the process depended substantially on the structure of the ionite and the amount of the cross-linking agent and the structure, properties, and concentration of amino acids. An attempt was made to consider the influence of the hydrophobic properties of amino acids on the enthalpy of the process.     

Interaction of sorbed Ni(II) ions with amorphous zirconium hydrogen phosphate

Samples of amorphous zirconium hydrogen phosphate with different zirconium and phosphorus concentrations in hydrogen and nickel-substituted forms are studied by means of electronic, ³¹P NMR, and impedance spectroscopy. It is shown that Ni(II) → H⁺ ion exchange is accompanied by the hydrolysis of sorbed cations and the formation of complexes with the dihydro- and hydrophosphate groups of the inorganic ionite. It is found that the coordination environment of Ni(II) in the sorbent phase includes 2–4 fragments of phosphate groups, along with OH groups and water molecules.     

Gas phase hydration of organic ions

In this work, we study the hydration phenomenon on a molecular level in the gas phase where a selected number of water molecules can interact with the organic ion of interest. The stepwise binding energies (DeltaH degrees (n-1,n)) of 1-7 water molecules to the phenyl acetylene cation are determined by equilibrium measurements using an ion mobility drift cell. The stepwise hydration energies DeltaH degrees (n-1,n) are nearly constant at 39.7 +/- 6.3 kJ mol(-1) from n = 1 to 7. The entropy change is larger in the n = 7 step, suggesting cyclic or cage-like water structures. No water addition is observed on the ionized phenyl acetylene trimer consistent with cyclization of the trimer ion to form triphenyl benzene cations C(24)H(18) (+) which are expected to interact weakly with the water molecules due to steric interactions and the delocalization of the charge on the large organic ion. The work demonstrates that hydration studies of organic ions can provide structural information on the organic ions.     

Fragmentation of organic ions bearing fixed multiple charges observed in MALDI MS

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS) was used to analyze a series of synthetic organic ions bearing fixed multiple charges. Despite the multiple intrinsic charges, only singly charged ions were recorded in each case. In addition to the pseudo‐molecular ions formed by counterion adduction, deprotonation and electron capture, a number of fragment ions were also observed. Charge splitting by fragmentation was found to be a viable route for charge reduction leading to the formation of the observed singly charged fragment ions. Unlike multivalent metal ions, organic ions can rearrange and/or fragment during charge reduction. This fragmentation process will evidently complicate the interpretation of the MALDI MS spectrum. Because MALDI MS is usually considered as a soft ionization technique, the fragment ion peaks can easily be erroneously interpreted as impurities. Therefore, the awareness and understanding of the underlying MALDI‐induced fragmentation pathways is essential for a proper interpretation of the corresponding mass spectra. Due to the fragment ions generated during charge reduction, special care should be taken in the MALDI MS analysis of multiply charged ions. In this work, the possible mechanisms by which the organic ions bearing fixed multiple charges fragment are investigated. With an improved understanding of the fragmentation mechanisms, MALDI TOF MS should still be a useful technique for the characterization of organic ions with fixed multiple charges.     

Early contributions to the chemistry of organic radical ions

The correct chemical composition and the true nature of organic radical ions were not recognized until well into the 20th century. Yet, the earliest observation of such a species as a colored transient dates back at least 150 years. Some pioneering reactions involving radical ions are discussed, and contributions to their understanding are reviewed.     

Thermodynamic properties of individual ions, calculated in terms of conception of real thermodynamic properties of individual ions in solutions

Real and chemical thermodynamic characteristics for several ions in mixtures of water with organic solvents of different classes are calculated on the basis of the proposed conception of real thermodynamic properties of individual ions in solutions. This conception is an improved and generalized version of the procedure for describing thermodynamic activity of individual ions in aqueous electrolyte solutions, which was successfully exploited for many years. The offered methodology enables one to determine thermodynamic characteristics of individual ions both in aqueous and nonaqueous electrolytes. The use of the Volta potential differences for determining real and chemical thermodynamic characteristics of individual ions in solutions is validated.     

Kinetics of radiolytic oxidation of ferrous ions in some aqueous aerated systems

The oxidation of ferrous ions by organic peroxy radicals at different doses is non-linear, however, the plots of inverse of ferric ion concentration against inverse of dose are linear. This behavior is explained by a set of three general reactions. Some of the organic free radicals produced in these systems either react with O₂ forming peroxy radicals or they get oxidized by ferric ions. Other organic free radicals do not involve in the above competition and react with O₂ only.     

A study of the decomposition of field ionized doubly charged molecular ions

The dissociation of field ionized doubly charged organic molecular ions into doubly charged fragment ions and neutral fragments is discussed. The kinetic energy released during the dissociation of the singly and doubly charged molecular ions rules out the possibility of a direct correlation between their mechanisms of formation. Further, the pressure as well as the temperature dependence revealed that the singly charged molecular ions are formed by direct ionization of the neutral molecules, while the doubly charged molecular ions are formed through a second ionization process of the adsorbed molecular ions on the field anode surface.     

Liquid-liquid extraction of some lanthanide metal ions by polyoxyalkylene systems

Polyoxyalkylene systems, namely, polypropylene glycol (PPG-1025), polyethylene glycol (PEG-600) and polybutadieneoxide (PBDO-700) dissolved in either nitrobenzene or 1,2-dichloroethane have been tested as prospective extractants for some lanthanide metal ions (Eu(3+), Pr(3+) and Er(3+)) from their aqueous solutions in the presence of picrate anions. The metal ions were quantified before and after extraction using the inductively coupled plasma emission spectrophotometry technique. The percent extraction and the distribution coefficients have indicated that pH of the aqueous phase, picrate concentration and the organic solvent are the major parameters that affect the extraction efficiency of the metal ions. The optimum pH range was found to be 3.5-5.5 and the picrate concentration should be as high as possible; however, a picrate concentration of about 0.05 M proved to be adequate for a near quantitative extraction. In all cases, nitrobenzene enhanced a higher percent extraction compared to 1,2-dichloroethane. The efficiency of the polyoxyalkylene systems to extract certain lanthanide metal ions was in the order PBDO-700>PPG-1025>PEG-600 when nitrobenzene was the organic solvent and in the order PPG-1025>PBDO-700 approximately PEG-600 when 1,2-dichloroethane used as the solvent in the organic phase. The extractability of PPG-1025 towards the lanthanide metal ions was in the order Pr(3+)>Eu(3+)>Er(3+) irrespective of the organic solvent used. The stoichiometry of the extracted polyoxyalkylene ion-pairs with the lanthanide metal ions has been estimated. Each mole of metal ions is associated with three moles of picrate anions and 13 to 14 moles of propyleneoxide units in the case of PPG-1025, and about 9 to 10 moles of ethyleneoxide units in the case of PEG-600 and 10 moles of butadieneoxide units in the case of PBDO-700.     

Reactive nitrogen species: Nitrosonium ions in organic synthesis

Nitrosonium ions are versatile and mild oxidants, which were successfully employed in organic transformations. The applications cover different fields, such as the functionalization of carbon-carbon and carbon-heteroatom bonds, functionalization of unsaturated bonds and the oxidative coupling of arenes, catalyzed by nitrosonium ions. Due to the ability of nitrosonium ions to modify various types of bonds with different modes of action, a variety of applications has been established, which addresses current challenges in organic chemistry research. By considering additional points, such as safety of reagents, by-product formation, employed solvents and energy consumption, several aspects of green and sustainable chemistry can be addressed. Within this review, synthetic applications of nitrosonium ions under transition metal-free reaction conditions are summarized.     

Analysis of inorganic and small organic ions by CE with amperometric detection

Capillary electrophoresis has become a widely useful analytical technology. Amperometric detection is extensively employed in capillary electrophoresis for its many inherent virtues, such as rapid response, remarkable sensitivity, and low cost of both detectors and instrumentations. Analysis of inorganic and small organic ions by capillary electrophoresis is an important research field. This review focuses on the recent developments of capillary electrophoresis coupled with amperometric detection for analysis of inorganic and small organic ions. Advancements in electrophoresis separation modes, amperometric detection modes, working electrodes, and applications of inorganic ions, amino acids, phenols, and amines are discussed.     

Use of portionwise extractant feeding for the extraction of metal ions from aqueous solutions with tributyl phosphate

A procedure involving portionwise extractant feeding was suggested for improving the characteristics of selective extraction of metal ions from aqueous solutions. This procedure enhances the extraction of metal ions into the organic phase, reduces the extractant consumption, and increases the distribution ratio of metals between the organic and aqueous phases and the metal separation factor in extraction.     

Polarization characteristics of monopolar ionite membranes

An experimental setup (a membrane rotating disk electrode) is described. Combinations ionitepolyethylene applied in the production of membranes MK-40, MK-41, and MA-40 are used as compositions modeling commercial monopolar ionite membranes. The setup design allows one to separately measure the diffusion limitations on the let-in and let-out sides of membranes. The comparison of experimental polarization characteristics and theoretical dependences (plotted earlier) shows that a polarization characteristic is a net dependence for two processes of electromasstransfer. One process is associated with the diffusion limitations from the solution side. The other is attributed to the hydrolysis of fixed ionogenic groups of the membrane’s ionite and precedes the electrochemical stage of charge transfer across the membrane/electrolyte interface.     

Salting out of hydrophobic ions at immisicble electrolyte interfaces

The increase in the polarisation window of electrified electrolyte interfaces due to salting out effects of the organic electrolyte has been studied. It is shown that the salting out theory of Kirkwood can be applied to these systems and that the changes in the transfer potentials of large hydrophobic ions with the concentration of aqueous electrolytes is in reasonable agreement with the known molecular dimensions of the ions studied.