The effect of light on the Mn(II) or Fet(lll)-catalyzed oxidation of aqueous S(IV)

in absence of light, the reaction kinetics of Mn(II) and Fe(III)-atalyzed oxidation ofS(IV) in unbuffered and buffered solutions were studied. An activation energy of 77.4kJ . mol-1 forthe Mn(II)catalyzed oxidation of S(IV) is obtained. On the basis of the investigation of thecatalytic effects of Mn(II) and Fe(III) on the oxidation of S(IV), it has been elucidated that thecatalytic activity of Mn(II) is greater than that of Fet(III), and that Mn(II) and Fe(III) do not havea significant synergic effect on the catalytic oxidation of S (IV). The catalytic oxidation andautooxidation of S(IV) in unbuffered solution was also explored in the presence of light. The resultsshow that the reaction is first order with respect to S(IV) concentrations, the reaction rate increaseswith increasing light intensity and the concentrations of Fe(III) and Mn(II), and that the photoas-sisted catalytic activity of Fe(III) is greater than that of Mn(II).