RESUMO
The current study focuses on a prime effect of pH changes in the catalytic ozonation process (COP) by using three main classes of catalysts such as zeolites (alumina-silicates), alumina (metal oxides), and activated carbons for decolorization of Reactive Red 241 (RR-241). The role of pH changes, point of zero charges and the effect of catalyst dose on pH change was studied. The results reveal that the overall removal efficiency of RR-241 in the case of COPs was the highest compared with single ozonation process (at pH = 7 the efficiency was 80, 65 65.5 and 60% for AC/O3, Al2O3/O3, Zeolite/O3 and O3 respectively). At initial acidic pH 4, the highest pH variations in COPs and ozonation processes were observed. Moreover, the pH changes were not found to be significant near the point of zero charges of materials (pHpzc = 6.8, 8.4 and 8.8 for zeolite, activated carbons and Al2O3, respectively. The COP in the presence of activated carbon shows the highest removal efficiency (82%) at pH 7. The material dose effect indicates that increasing the amount of catalyst (from 1 gm to 2 gm) significantly leads to a change in the pH of the solution. Results reveal the prominent effect and significance of pH changes on the efficiency of COP to determine true catalytic efficiency.