Efficient sonophotocatalytic degradation of acid blue 113 dye using a hybrid nanocomposite of CoFe₂O₄ nanoparticles loaded on multi-walled carbon nanotubes

Complete degradation of acid blue 113 (AB113) dye was successfully achieved by using the sonophotocatalytic process with CoFe₂O₄ nanoparticles loaded on multi-walled carbon nanotubes (MWCNTs/CoFe₂O₄), as a novel catalyst. The catalyst used was synthesized using the solvothermal co-precipitation method. First, the characteristic parameters of the synthesized catalyst were evaluated using advanced analyses of Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy-Dispersive X-Ray Spectroscopy (EDX), Thermogravimetric (TGA), Vibrating Sample Magnetometry (VSM), and Fourier Transform Infrared Spectroscopy (FTIR). The results of the sonophotocatalytic degradation experiments showed that the optimum parameters for 100% AB113 removal were: AB113 concentration = 25 mg/L, pH = 3, MWCNTs/CoFe₂O₄ dose = 0.4 g/L, reaction time = 40 min, intensity of UV light = 36 W, and intensity of ultrasonic waves = 50 kHz. To identify the utility of using MWCNTs/CoFe₂O₄ as a catalyst, the degradation efficiencies of AB113, resulting from the sonophotocatalytic process, were compared with those determined from other similar treatment processes, that is, adsorption, photolysis, sonolysis, and sonocatalytic and photocatalytic processes, where the sonophotocatalytic process was found to be the most efficient one. Catalyst recycling was performed in eight degradation–regeneration cycles, whereas, a total reduction of 9% was observed in removal efficiency after the 8th cycle. The results showed that the AB113 dye, which was a non-biodegradable contaminant, became almost a biodegradable compound after subjection to sonophotocatalytic treatment. The results also demonstrated a high mineralization rate of the applied treatment method. In addition, a toxicity test was performed using Daphna Magna, and the results indicated a low toxicity of the AB113 dye effluent. The results of this study clarified that the sonophotocatalytic process system using MWCNTs/CoFe₂O₄ could be a feasible and cost-effective system for degrading dyes, for example, AB113.