This research investigated the kinetics of cyanide oxidation by ozone in cassava starch production process. An acrylic column, equipped with a gas sparger located at the bottom of the column, were used as a reactor. Cassava starch solutions with the cyanide concentrations of 10, 20, 30, 40 mg/l were prepared from fresh cassava roots. The experiments were performed at the ozone generation rates of 7.4, 15.0, 22.6, and 30.0 g O-3/h. The results showed that the cyanide concentration sharply decreased during the first 30 s of the reaction time, and after that the concentration slightly decreased. Moreover, cyanohydrin, which could not be oxidized by ozone, was not completely converted to hydrogen cyanide. The kinetics of cyanide oxidation was first order with respect to cyanide and zero order with respect to ozone. The rate constant obtained from the first order equation of cyanide oxidation with ozone was 2.76 min(-1). (c) 2007 Elsevier Ltd. All rights reserved.