OXIDATION OF AQUEOUS SULFIDE SOLUTIONS BY DIOXYGEN - PART II - CATALYSIS BY SOLUBLE AND IMMOBILIZED COBALT(II) PHTHALOCYANINES

The oxidation of sulfide in oxygen-saturated aqueous solutions is acce lerated by dissolved or silica-bonded cobalt phthalocyanines. On the b asis of thermodynamical considerations it is postulated that the catal yst enhances the formation of disulfide as the initial elementary reac tion step. The following reaction steps are largely unaffected by the catalyst, as indicated by a product ratio sulfate/thiosulfate = 0.86, comparable to that of the uncatalyzed autoxidation. A Langmuir-Hinshel wood formalism is developed for the catalytic reaction step and is dem onstrated to fit best with the kinetics. In addition, from the kinetic data free enthalpies for the adsorption of HS- (i) at the dissolved p hthalocyanine (Delta G=-17.6 kJ/mole) and (ii) at the immobilized comp lex (Delta G=-20.0 kJ/mole) are calculated.