Investigation of the sequential ozonation process for decolourization and degradation of Reactive Red 120

Using the sequential ozonation process for removing Reactive Red 120 dye (RR 120) was investigated. All the experiments were conducted in 2 L glass reactor with dye concentration, pH, reaction time and sequencial stream with O 3 flow rate of 0.2 L.min −1 . The effects of the initial pH values (3, 5, 7, 9 and 11) and initial RR 120 concentrations (25, 50, 75 and 100 ppm) in removal of RR 120 for decolourization and degradation were experimented. The results showed that the optimal conditions at acidic pH values of pH 3 and 5 for removing RR 120 with decolourization and COD removal efficiencies were obtained. At pH 3 and 5, colour removal efficiency was very high from 69 % to 99 % in experiments with initial RR 120 concentrations from 25 to100 ppm. COD removal was not as high as decolourization efficiency, COD removal at pH 3 obtained 96.27–93.47 - 73–40 % and at pH 5, got 90.27–88.27 - 62.48–29.82 % at experiments with the initial RR120 concentrations of 25–50 - 75 −100 ppm, respectively. Moreover, in this acidic condition, BOD 5 /COD ratio in the experiments was determined from 0.30 to 0.38 that illustrated the biodegradable solution after using the sequential ozonation process for removing RR 120 dye in polluted wastewater. • The optimal condition for removing RR 120 at acidic pH 3 and 5 with high decolourization and COD removal efficiencies by the sequential ozonation process. • Direct O 3 as an important role in RR 120 removal by obtained high efficiecies of decolourization and COD removal at the acidic conditions of pH 3 and 5. • The biodegradable capacity after using ozonation process for RR 120 removal at the acidic condition.