Synergistic Effect of Sono-Photocatalysis on the Degradation of Rhodamine B Dye Using BiFeO3 Nanoparticles Synthesized via a Modified Combustion Method

Water contamination has become a global concern, and the prevalence of complex substances known as emerging contaminants constitute a risk to human health and the environment. This work focused on an innovative approach of integrating sonolysis and photocatalysis to remove a standard textile dye efficiently. A highly photo-active, bismuth ferrite (BiFeO3) nanocatalyst with single particle sizes between 86 and 265 nm was obtained by a novel one-pot combustion method using a deep eutectic solvent as a precursor. The said catalyst was thoroughly characterized and evaluated for photocatalytic and sono-photocatalytic degradation of rhodamine B (RhB). Photocatalytic experiments were conducted under visible light irradiation (450–600 nm). Sono-photocatalytic (SPC) experiments were conducted, focusing on the influence of operational parameters (frequency, power, and pH) on the degradation performance. High-frequency values of 578, 866, and 1138 kHz were explored to promote cavitation dynamics and reactive species generation, improving removal efficiency. Results demonstrated that when sonolysis and photocatalysis were performed separately, the degradation efficiency ranged between 85 and 87%. Remarkably, when the combined SPC degradation was carried out, the RhB removal reached about 99.9% after 70 min. It is discussed that this behavior is due to the increased generation of OH• radicals as a product of the cavitation phenomena related to the ultrasound-assisted process. Moreover, it is argued that SPC significantly improves reaction kinetics and mass transfer rates, facilitating catalyst dispersion and contact with the RhB molecules. Finally, the stability of the catalyst was evaluated in five repeated RhB removal cycles, where the activity remained consistently strong.