Study On Heterogeneous Catalytic Ozonation Process And Reaction Mechanism Based On Microbubble Technology

Microbubble ozonation could enhance·OH generation,and the solution environment was the important influencing factor for·OH generation in microbubble ozonation.In addition,ozone catalyst could improve·OH generation and increase ozone oxidation efficiency further in microbubble ozonation.In this study,the p-chlorobenzoic acid（p CBA）was used as·OH indicator and the activated carbon（AC）was used as ozone catalyst in microbubble ozonation and microbubble catalytic ozonation to oxidize p CBA.The performance of·OH generation was evaluated in microbubble（catalytic）ozonation based on the degradation rates of p CBA in different reaction systems.The influences of solution p H values and typical inorganic anions（not·OH scavengers）on·OH generation in microbubble（catalytic）ozonation were analyzed.The mechanism of·OH generation in microbubble（catalytic）ozonation was also discussed.The results were as follows:（1）The·OH generation in microbubble ozonation was much more efficient than that in conventional bubble ozonation and conventional bubble catalytic ozonation.The degradation rate of p CBA in microbubble ozonation was 12.6 times of conventional bubble ozonation and 6.28 times of conventional bubble catalytic ozonation,respectively.The·OH generation rate in microbubble ozonation was 15.4 times of conventional bubble ozonation and 10.2 times of conventional bubble catalytic ozonation,respectively.The sequence of both degradation rate of p CBA and·OH generation rate in microbubble ozonation at different p H values was as follows:p H=9﹥p H=7﹥p H=5﹥p H=3﹥p H=11.The inorganic anion with higher negative charge showed less negative effect on both degradation rate of p CBA and·OH generation rate in microbubble ozonation.The increased inorganic anion concentration showed more negative effect on both degradation rate of p CBA and·OH generation rate in microbubble ozonation.（2）When AC was used as ozone catalyst in microbubble ozonation,both degradation rate of p CBA and·OH generation rate were enhanced further.The higher degradation rate of p CBA was achieved at an AC dose of 1.5 g·L^-1.The degradation rate of p CBA could be enhanced more in microbubble catalytic ozonation at high p CBA concentration.In this case,the degradation rate of p CBA was 1.3～1.5 times of microbubble ozonation.Less enhancement of degradation rate of p CBA occurred in microbubble catalytic ozonation at low p CBA concentration and in this case,the degradation rate of p CBA was 1.1 times of microbubble ozonation.The sequence of·OH generation rate in microbubble catalytic ozonation at different p H values was as follows:p H=7﹥p H=9﹥p H=5﹥p H=3﹥p H=11.The influence of inorganic anions on·OH generation in microbubble catalytic ozonation was the same as microbubble ozonation.（3）The·OH was detected directly in conventional bubble ozonation,microbubble ozonation and microbubble catalytic ozonation.The·OH generation pathways in microbubble catalytic ozonation included ozone self-decomposition,microbubble collapsing and ozone catalytic decomposition,and therefore,its·OH signal was strongest.The·OH generation pathways in microbubble ozonation included ozone self-decomposition and microbubble collapsing,and therefore,its·OH signal was also strong.The·OH generation pathways in conventional bubble ozonation included ozone self-decomposition only,and therefore,its·OH signal was very weak.