Polymer supported metal complexes as catalysts for oxidation of thiosalts by molecular oxygen IV. Quaternised poly(4-vinyl pyridine) complexes with Cu 2+ as template

Abstract

Copper(II) complexes of quaternised poly(4-vinylpyridine) (PVP) of different degrees of quaternisation and copper content have been prepared by crosslinking the polymer with 1,2-dibromoethane in the presence of Cu 2+ ion as template. The stability constant of the PVPCu(II) complexes is found to increase with the degree of crosslinking quaternisation of the resin, but the rate at which Cu 2+ is adsorbed by the resin decreases. An optimum combination of both stability and rate can be achieved with a moderate degree (31%) of crosslinking. A kinetic study reveals that quaternisation increases significantly the catalytic activity of the complex for the oxidation of S 2O 2− 3 by O 2 compared with PVP-Cu(II) without quaternisation, but it deactivates the complex for the oxidation of both S 3O 2− 6 and S 4O 2− 6. The batch reactor oxidation kinetics at pH 2.16, where the rate is observed to be maximum, is well explained by the Langmuir—Hinshelwood model assuming the coordination of both O 2 and thioanion to Cu(II) as a precursor to the oxidation reaction.