Indirect catalytic oxidation of multi-pollutants in diesel exhaust by ozone/micro-nano bubbles system

Wet oxidation absorption is an efficient and promising method of exhaust gas treatment. When the micro-nano bubbles collapse, they can generate hydroxyl radicals with strong oxidising ability, which can oxidise a variety of pollutants in diesel exhaust. Ozone has strong oxidising properties, and the coupling of ozone and micro-nano bubbles can improve the oxidation and removal effects of polluted gases. In this study, the ozone micro-nano bubbles system was used to oxidise NOx, SO2, and CO to gases that were more readily dissolved in water, such as NO2, SO3, and CO2, and the gases were removed through the absorbent solution. The effects of surfactant, catalyst, urea, pH value, and salinity on the removal efficiency of NOx, SO2, and CO from diesel exhaust were investigated. Through experiments, it was found that the removal efficiency of pollutants was enhanced and then weakened with the increasing concentrations of surfactants, catalysts, and salinity, and continued to decrease with increasing concentrations of urea. When the pH value was < 7, the removal efficiency increased first and then weakened with the increase of the pH value. When the pH value was > 7, it mainly depended on the absorption of acid gas by the alkali solution. Under optimal conditions, the removal efficiencies were 86.3% for NO, 92.1% for SO2, and 65.4% for CO. This study could provide important theoretical support for the industrial application of this technology.