AQUEOUS S(IV) OXIDATION .2. SYNERGISTIC EFFECTS OF SOME METAL-IONS

The reaction kinetics of S(IV) oxidation catalysed by mixtures of Mn(II) and Fe(III), and Mn(II), Fe(III) and Pb(II) in aqueous solutions over the pH range 3-6 were studied at concentrations of metal ions and S(IV) as found in an urban atmosphere. The catalytic synergism between the Mn(II) and Fe(III) was confirmed. Experimental evidence for the synergistic catalysis of S(IV) oxidation in the presence of Mn(II), Fe(III) and Pb(II) is also presented. For the combined system Mn(II)-Fe(III) the following rate expression was obtained: -r(S(IV)) = +r(S(VI)) = k{[Mn(II)] + [Fe(III)]}[S(IV)]0.85, k = 1.0 x 10(3) mol-0.85 l 0.85 s-1, pH = 4.0, T = 25 +/- 1-degrees-C. The pH and temperature dependencies of the reaction rate were determined. In addition, the effect of an electrostatic precipitator fly ash (EFA) on the aqueous S(IV) oxidation was studied. It was found that its effect depends upon water soluble fraction of metal ions.