Preparation of novel CeO₂-biochar nanocomposite for sonocatalytic degradation of a textile dye

The sonocatalytic performance of CeO₂ nanoparticles synthesized by a hydrothermal method (CeO₂-H) and CeO₂@biochar (CeO₂-H@BC) nanocomposite, were evaluated for the degradation of Reactive Red 84 (RR84) under ultrasonic irradiation. For comparison purposes the corresponding performance of bare biochar (BC) and commercial CeO₂ (CeO₂-C) samples were also assessed. A complementary characterization study, involving scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), N₂ adsorption at −196 °C (Brunauer–Emmett–Teller (BET) method) and Fourier transform infrared spectroscopy (FT-IR) was undertaken to gain insight into the structure-performance relationships. The effect of various parameters such as initial RR84 concentration, solution pH, catalyst amount and ultrasonic power on the sonodegradation of RR84 was studied in detail. The results indicated that the CeO₂-H@BC nanocomposite exhibited the best RR84 degradation efficiency, which is enhanced with the increase of CeO₂-H@BC amount and ultrasonic power but diminished with the increment in RR84 concentration and pH value. A 98.5% degradation was obtained with a CeO₂-H@BC amount of 1 g/L, ultrasonic power of 450 W, pH of 6.5 and initial RR84 concentration of 10 mg/L. The quenching effects of various scavengers proposed that ^[rad]OH radical plays the key role in the process. Analyses of intermediates by Gas chromatography-Mass spectroscopy (GC–MS) identified several by-products and accordingly the main pathway was proposed.