Lanthanide-ion-induced paramagnetic shifts in NMR spectra in aqueous solutions

Theoretical and Experimental Chemistry -     

Specific features of the absorption of divalent manganese ions from aqueous solutions by zeolites

Sorption properties of natural zeolites from various Russia’s deposits for the Mn²⁺ ion were studied in comparison with various industrial adsorbents and some minerals. It was demonstrated that the equilibrium sorption capacity of these materials can be raised by their Na⁺-modification. The natural zeolites are advantageous at low Mn²⁺ ion concentrations over synthetic cation exchangers and activated carbons. The sorption capacity of the natural zeolites grows with increasing temperature.     

Water exchange dynamics of manganese(II), cobalt(II), and nickel(II) ions in aqueous solution

The first row transition metal ions Mn(2+), Co(2+), and Ni(2+) have been studied by classical umbrella sampling molecular dynamics simulations. The water exchange mechanisms, estimates of reaction rates, as well as structural changes during the activation process are discussed. Mn(2+) was found to react via an I(A) mechanism, whereas Co(2+) and Ni(2+) both proceed via I(D). Reaction rate constants are generally higher than those obtained by experiment but the simply constructed metal(II) ion-water potential reproduces the relative order quite well.     

Ion exchange recovery of chromium (VI) and manganese (II) from aqueous solutions

Sorption recovery of toxic ions – chromium (VI) and manganese (II) – from aqueous solutions with different acidity (0.001–0.5 M HCl) was investigated on cation and anion exchangers synthesized with long-chained cross-linking agents (LCA). The initial concentrations of Cr(VI) and Mn(II) were 1 g/L and 5 g/L, respectively. It was shown that the resins with LCA possess high ionic permeability due to the elasticity of polymeric skeleton. High selectivity and good kinetic properties of these sorbents allowed to achieve quantitative (∼100%) recovery and separation of manganese (II) and chromium (VI) in counter-current columns, which results in the complete purification of solutions from toxicants (below the maximum permissible limits), whereas the valuable components (chromium and manganese) can be returned back to industrial process.     

ESR spectra of Cu(II) N-alkyldithiocarbamates

ESR spectra are reported for polycrystals, solutions, and glasses. In every case the -bonds are found to be substantially covalent. The identical spectra point to structural identity; the substituents affect only the spectra of polycrystals via differences in packing. The spectra are examined by MOLCAO methods and with allowance for the mixing of other d orbitals with the ground-state orbital. Both methods give similar results.