Abstract:

Zinc oxyhydroxide (ZnOOH) prepared in laboratory was used as catalyst to determine rate constants of the catalyzed ozone decomposition and the catalytic ozonation of p-chloronitrobenzene (p-CNB) in water.The mechanism of catalytic ozone decomposition was discussed and then determined by electron spin resonance (ESR) test.The effect of solution pH on the catalytic activity of zinc oxyhydroxide was investigated.The results showed that the first-order rate of ozone decomposition increased by 1.87 times in the presence of zinc oxyhydroxide.At the reaction time of 20 min, the p-CNB removal efficiency of ZnOOH/O₃ was about 96.1%, one time more than that of O₃.An enhancement of hydroxyl free radicals was obtained in the ZnOOH catalyzed ozone decomposition.The addition of radical inhibitor, such as t-butanol, significantly depressed the rate constant of catalytic ozonation of p-CNB, by at least 10 times.No correlation was found between surface hydroxyl groups and the activity of catalytic ozonation of p-CNB.The state of surface charge has some relation with the catalytic activity of ZnOOH, as the nearly zero charged surface (the solution pH was close to pH_pzc) was favorable for the catalytic ozonation of p-CNB.