Cation solvation in mixed solvents

Pritam Singh

This thesis is a study of the solution chemistry of copper compared with that of sodium and silver cations in aqueous solvent mixtures, particularly in acetonitrile/water. The results have potential applications in improving the efficiencies of various hydrometallurgical processes and energy storage batteries. The conductivities of copper(I), copper(II), silver and sodium cations in organic/water mixtures change on transfer from water to organic/water mixtures in a way which shows that the ions undergo heteroselective salvation. The salvation shell compositions of these ions are estimated from their conductivity values in acetonitrile/water mixtures. The ionic thermodynamic functions (free energy, enthalpy, entropy and partial molal volumes) of transfer from water to various solvent mixtures reflect specific ion-solvent interactions which have been interpreted in terms of various salvation models. This information explains the nature of some leaching reactions of hydrometallurgical importance. The kinetics of the electroreduction of copper(II) to copper(I) and copper(I) to copper(O) in acetonitrile/water mixtures show that both of these reductions are fast and reversible on platinum, glassy carbon and mercury electrodes. The standard heterogeneous rates of electron transfer depend on the concentration of acetonitrile, the nature of the electrode material and the chemisorption of acetonitrile on the electrode surface. The knowledge of the solution chemistry of copper ions in acetonitrile/water is used to design and investigate an energy storage battery based on the copper(II)/copper(I) and copper(I)/copper(O) couples.

Cation solvation in mixed solvents

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