Kinetics of surface-catalyzed autoxidation of aqueous sulfur dioxide in cobalt(III) oxide suspensions

Government College, Jhalawar; L.B.S. College, Jaipur; Gyanjyoti College, Srikaranpur; Government College, Kota; eoovernment College, Sawai Madhopur; Maharshi Arvind College of Engineering, Jaipur; Department of Chemistry, University of Rajasthan, Jaipur-302 004, India

Manuscript received 1 October 2002

The surface-catalyzed autoxidation of sulfur(IV) in acetate buffered suspensions of Co₂O₃ obeys the kinetic rate law (A),

                           \(-d[S(IV)] \over dt\)  = (k₃ + k₄) [H⁺]^-1 [S(IV)] [Co₂O₃]                     (A)

In unbuffered suspensions, the rate law (B), at constant pH, is obeyed,

                                   \(-d[S(IV)]\over dt\)= (k₇ [Co₂O₃] [S(IV)]                                 (B)

The reaction is not inhibited by ethanol, and this ruts out the operation of a radical mechanism. The suggested mechanism implicates the absorption of both O₂ and sulfur(IV) on Co₂O₃ particle surface. The electron transfer within the surficial complex is responsible for the oxidation of sulfur(tIV).