Enhanced Absorption-Ozonation Treatment Of High-Concentration VOC Gas By Microbubbles

Volatile organic compounds（VOCs）are the main contaminants influencing atmospheric environment quality.In this study,microbubble ozonation was used to treat the high concentration ethyl acetate(14640mg·m^-3)and toluene(12000mg·m^-3)gas and compared with common bubbles.The enhancement of absorption process and oxidation process after dissolving of ethyl acetate and toluene gas by microbubbles was investigated,based on removal efficiency and oxidizing-mineralization efficiency.The dynamics and mechanism of enhanced absorption process and oxidation process were also explored.The results indicated that:1)The removal efficiency of ethyl acetate was 53.9%in the absorption process using common nitrogen bubbles.The removal efficiency was 96.4%and the mineralization efficiency was 67.1%in the absorption-oxidation process using nitrogen microbubbles.The removal efficiency was 63.7%and the mineralization efficiency was 47.2%in the absorption-oxidation process using common ozone bubbles.The removal efficiency was96.9%and the mineralization efficiency was 90.2%in the absorption-oxidation process using ozone microbubbles.Therefore,microbubble ozonation showed significant effect on enhancement of absorption-oxidation removal process for ethyl acetate with strong solubility2)The removal efficiency of toluene was 39.8%in the absorption process using common nitrogen bubbles.The removal efficiency was 94.9%and the mineralization efficiency was 49.8%in the absorption-oxidation process using nitrogen microbubbles.The removal efficiency was 52.2%and the mineralization efficiency was 26.0%in the absorption-oxidation process using common ozone bubbles.The removal efficiency was96.2%and the mineralization efficiency was 88.6%in the absorption-oxidation process using ozone microbubbles.Therefore,microbubble ozonation showed significant effect on enhancement of absorption-oxidation removal process for toluene with poor solubility.When Fe OOH was used in microbubble catalytic ozonation,the mineralization efficiency could be increased from 55.8%to 92.2%at higher mass flow rate of toluene.3)The absorption process and oxidation process after dissolving of ethyl acetate and toluene gas accorded with the apparent zero order dynamics under experimental conditions.The absorption rates of ethyl acetate and toluene gas using microbubbls were1.9 and 2.5 times of these using common bubbles.The oxidation reaction rates of ethyl acetate and toluene using ozone microbubbls were2.2 and 4.3 times of these using common ozone bubbles.The maximum absorption rate and oxidation reaction rate were achieved and almost the same in microbubble ozonation.The R values（the ratio of ozone consumption to TOC removal）of ethyl acetate and toluene were 1.6 and 2.7 using common ozone bubbles,respectively.In microbubble ozonation,these R values reduced to1.09 and 1.12 respectively,indicating significant improvement of oxidation performance.The·OH oxidation was enhanced greatly in microbubble ozonation,which was the main reason for increased oxidation performance.