Catalytic ozonation technology is an efficient and deep treatment method. The hydroxyl radicals (·OH) generated in the reaction process have strong oxidation ability and no selectivity, which can effectively improve the treatment effect of wastewater. At present, the most common solid catalysts studied are metal oxides loaded on the surface of activated carbon, activated alumina and other carriers.
These catalysts have good treatment effect on wastewater, but there are problems such as serious loss of active components and large wear, so it is difficult to apply them to practical industry. In addition, most of the current research on the mechanism of catalytic ozonation is to investigate the removal rate of organic matter by adding collectors such as tert-butanol, indirectly reflecting the yield of ·OH. In this study, clay and alumina were selected as substrates, doped with active components, and prepared into catalysts with high mechanical strength and good wear resistance for experiment. The mechanism of catalytic ozonation was explored by measuring ozone decomposition, directly quantitatively measuring the concentration of ·OH, and characterizing the surface hydroxyl groups of the catalyst.
Conclusions:The compressive strength of the homemade catalyst is 1685 N, and the wear rate after 45 days is 1.67%, which is better than that of commercial granular activated carbon and alumina balls.
Using the homemade catalyst to catalyze ozonation of high salt wastewater from coal chemical industry, under the conditions of pH = 8.1, catalyst dosage of 7 g /L, and ozone dosage of 13 mg /min, the removal rates of COD and colority are 45% and 85%, respectively, which meet the subsequent requirements of salt separation and crystallization: ρ(COD) ≤200 mg /L, colority ≤15 times.
The key factor for ozone decomposition on the surface of the catalyst is the active site - surface hydroxyl group. Through Fourier infrared spectroscopy analysis, it can be seen that there are hydroxyl groups on the surface of the catalyst; the decomposition rate of ozone catalysis is higher than that of pure ozone decomposition, and in the same time, the catalyst can promote ozone decomposition to produce more ·OH. Therefore, it can be concluded that the mechanism of catalytic ozonation follows the hydroxyl radical reaction mechanism: ozone adsorbs on the active site of the catalyst surface to generate ·OH, thereby promoting the degradation of organic matter.
