Gibbs energies of formation of hydroxides of lanthanides and yttrium

The pH values of the formation of hydrates in solutions of yttrium(III), cerium(III), samarium(III), europium(III), erbium(III), and ytterbium(III) were determined by conductometric titration. The solubility products and Gibbs energies of formation for hydroxides for the elements listed were calculated. The average Gibbs energy of dissolution for lanthanide hydroxides was found to be approximately 149.83 ± 0.90 kJ/mol. The Gibbs energies of formation for hydroxides of the remaining lanthanides were assessed on this basis.     

Solvent sublation of cerium ions from dilute aqueous solutions

The possibilities of using the adsorptive bubble process of separation (solvent sublation) for the removal of trace amounts of cerium were studied. The optimal conditions and kinetic regularities of the process in solutions containing cerium ions and a surfactant (sodium dodecyl sulfate) used as a collector were determined. The structure of the sublates extracted into the organic phase changes depending on the pH of the medium.     

Thermodynamics of formation of lanthanide hydroxo complexes in aqueous solutions

Gibbs energies of formation have been determined by conductometric titration for hydroxo complexes of cerium, samarium, europium, erbium, ytterbium, and yttrium. All these elements form monohydroxo complexes; yttrium, erbium, and terbium also form dihydroxo complexes. The Gibbs energies of formation of lanthanide hydroxo complexes from ions have virtually equal values of −47.3 ± 0.6 kJ/mol monohydroxo complexes and −44.5 ± 0.5 kJ/mol for dihydroxo complexes, respectively. These values were used to estimate the Gibbs energies of formation of hydroxo complexes for the entire lanthanide series.     

Kinetics of the ion exchange of lead and sodium cations on the surface of iron-manganese concretions

Kinetic characteristics (rate constants and activation energy) of the sorption of lead cations by iron-manganese concretions were studied.     

Isotherm of strontium and sodium cation exchange on iron-manganese nodules

The isotherm of ion exchange of Sr²⁺ and Na⁺ ions on iron-manganese nodules was obtained. It was suggested to describe the ion exchange by an equation analogous to the Langmuir isotherm equation. The limiting sorption and apparent ion exchange constant were calculated. The effective radius of sorbed strontium ions was determined.     

Isotherm of Strontium Sorption on Clay

Sorption of strontium(II) with soil components from model solutions was studied. Limiting sorption of strontium ions, their landing site area, and Langmuir constants were determined.     

Isotherm of exchange of sodium and copper cations on ferrimanganese concretions

Isotherm of ion exchange of Cu²⁺ and Na⁺ cations on ferrimanganese concretions was studied. The ion exchange is described by an equation similar to that of the Langmuir isotherm. The limiting sorption and apparent ion-exchange constant were calculated.