Bmim[OAc]-Cu₂O/g-C₃N₄ as a multi-function catalyst for sonophotocatalytic degradation of methylene blue

In this study, ionic liquid, 1-butyl-3-methylimidazolium acetate (Bmim[OAc]) modified cuprous oxide immobilized over graphitic carbon nitride (Bmim[OAc]-Cu₂O/g-C₃N₄) as an efficient heterogeneous catalyst was successfully prepared by depositing Bmim[OAc]-Cu₂O over the surface of g-C₃N₄. The deposition of cuprous oxide over the surface of g-C₃N₄ leads to the formation of a heterojunction that promotes the charge separation. Cu₂O enhances the degradation capability owing to its dual function where it acts as a photocatalyst and Fenton like catalyst. Bmim[OAc] plays a vital role in trapping the photogenerated electrons, which in turn reduce the chances of electron-hole pairs recombination. Sonophotocatalytic degradation of methylene blue (MB) was investigated using the prepared Bmim[OAc]-Cu₂O/g-C₃N₄ at room temperature and pH = 7 in presence of ultraviolet (UV, 6 W, λ = 254 nm) and ultrasonic (US, 20 kHz) as a dual irradiation system and H₂O₂ as an oxidant. Only 30 min of dual irradiation was enough for Bmim[OAc]-Cu₂O/g-C₃N₄ (0.1 gL^-1) to achieve a complete degradation using 10 mM H₂O₂ at 25 °C and pH = 7. The value of band gap of tested catalyst plays a vital role in boosting the degradation capability of the sonophotocatalytic system through the generated reactive radicals especially the hydroxyl radicals and superoxide radicals, which play a major role in the system. The kinetics of the reaction was investigated and the activation energy was calculated from the slope of the Arrhenius plot and found to be 19.77 kJ/mol.