Abstract:

Methyl-4-isothiazolin-3-one （MIT） is widely used in industrial production， but its persistence and potential biological toxicity in water environment have attracted widespread attention. Therefore， based on a Venturi tube cavitation reactor， a study was conducted on the process of oxidative degradation of methyl isothiazolinone using hydraulic cavitation technology combined with H₂O₂. With the aim of improving the degradation rate of MIT， the reaction time， inlet pressure， H₂O₂ addition amount， and MIT initial concentration were optimized. Through a series of experiments， the optimal reaction conditions were determined as follows： under the conditions of reaction time of 40 min， inlet pressure of 0.5 MPa， H₂O₂ addition amount of 5 mL/L， and MIT initial concentration of 15mg/L， the degradation rate of MIT reached 69%. In order to gain a deeper understanding of the degradation mechanism of MIT， Fourier Transform Ion Cyclotron Resonance Mass Spectrometry （FT-ICR-MS） technology was used to analyze the intermediate products of MIT degradation， and to speculate on the degradation process of MIT under this process condition. MIT mainly degrades its five membered ring structure through oxidation and addition reactions. This indicates that under the current experimental conditions， the degradation rate of MIT has reached a stable level， and further improving the degradation efficiency may require adjusting other parameters. On this basis， the initial rate method was used to determine that the degradation reaction of MIT under this process condition is a zero order reaction， that is， the reaction rate is not related to the concentration of MIT， but is influenced by other factors. Using the Coast Redfern model， the apparent activation energy of MIT was estimated to be 31.127 kJ/mol， providing an important basis for further optimizing the degradation process.

Key words: Hydrodynamic cavitation, Venture tube, Degradation, Methylisothiazolinone