Investigation of Hydroxyl Radical Yield in an Impact-Jet Hydraulic Cavitator

Hydroxyl radical (center dot OH) is a key component that leads to the cleavage of the glycosidic bond in the process of chitosan (CS) degradation by hydrodynamic cavitation (HC). In this paper, methylene blue (MB) was selected as the trapping agent of center dot OH and the yield of center dot OH in an impact-jet hydraulic cavitator was investigated. The results showed that the cavitation intensity and the number of passes (N) were the two main factors affecting the yield of center dot OH. A smaller cavitation number (C-v) or a larger N indicated that more center dot OH can be produced. Based on the dimensionless number correlation method, the yield of center dot OH was correlated with C-v , N, Euler number (Eu), Reynolds number (Re), and a dimensionless parameter (gamma), and a prediction model of center dot OH yield was established. The relative deviations between the experimental and calculated values of the center dot OH yield were basically within 10% by the prediction model. On the basis of the prediction model, the yield of center dot OH produced in the process of CS degradation by HC was obtained. The results showed that the predicted yield of center dot OH was significantly correlated with the intrinsic viscosity reduction rate of CS. It was suggested that the prediction model of center dot OH yield based on the MB solution can be used to calculate the center dot OH yield during the degradation of low concentration CS by HC.