Kinetics of the self-decomposition of ozone and the ozonation of cyanide ion and dyes in aqueous solutions.

Abstract

Kinetic studies on the self-decomposition of ozone in water, the decomposition of CN- and CNO-, and the decolorization of several dyes by ozone were performed over a wide range of pH using a stopped-flow apparatus under homogeneous conditions at 298 K. The rate of selfdecomposition of ozone was measured in the pH range from 1 to 13.5, and it was found that in the pH range above 8 the rate was expressed by -d[03]/dt=314 [03] [OH-]0.88while in the acidic region the concentration dependence of the rate was complicated, and a simple rate expression could not be obtained. The rate of decomposition of CN- by ozone was expressed by -d[CN-]/dt=310 [O3]0.8 [CN-]0.55 (9.4<pH<11.6)and the rate of decomposition of CNO- was found to be much slower than that of CN-. The decolorization rates of naphthol yellow and methylene blue followed second-order kinetics. Rate constants are presented.