The experimental data of sonocatalytic degradation of Reactive Black 5 (RB5) as an azo dye by core–shell nanocrystals (CdS–TiO2) were applied to the proper kinetic models. In this work, two kinetic models were proposed and fitted properly to the data. In the first one, the heterogeneous reaction was considered similar to the Langmuir–Hinshelwood (L–H) mechanism and the kinetic rate parameters were determined. In this model, short time of sonication with initial concentration changes has been applied and the contribution of the reaction intermediates has been neglected in degradation. Hence, this model may not be valid for longer reaction times where the reaction intermediates effects prevail. In the second one, two first-order reactions in series provided the most convincing rate form for the sonodegradation of dyes adsorbed on the synthesized nanocomposite. In these series reactions, the first step is the conversion of colored dye to colored intermediate, and the second step is the conversion to colorless product(s). The obtained results were in good agreement with the proposed kinetic models. The rate constants of degradation of catalyzed reaction were higher than that obtained without catalyst, solar and UV irradiation.

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