Wastewater treatment by sonocatalysis and sonophotocatalysis using Fe₃O₄/SnO₂ composite supported on nanographene platelets

In this study, we attempt to enhance the sonocatalytic performance of the Fe₃O₄/SnO₂ composites by depositing the Fe₃O₄/SnO₂ composites onto nanographene platelets (NGPs) in order to develop sonocatalysts and sonophotocatalysts. We combine the sonocatalytic process with UV light irradiation. Fe₃O₄/SnO₂ and Fe₃O₄/SnO₂/NGP composites were synthesized using co-precipitation and ultrasonic assisted methods, respectively. The structural properties and thermal stability of the samples were characterized using X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. The results show that the Fe₃O₄/SnO₂/NGP 10wt.% composite exhibits high efficiency for the sonocatalytic and sonophotocatalytic removal of methylene blue (MB), among the composites with various weight percentages (wt.%) of NGP. A comparison of the degradation efficiencies in the sonocatalytic and sonophotocatalytic processes using MB as a model organic pollutant revealed that sonophotocatalysis exhibits better degradation compared to sonocatalysis. The optimum degradation conditions were as follows: catalyst (Fe₃O₄/SnO₂/NGP 10wt.%) is 0.3 g L^-1, methylene blue (MB) solution concentration is 20 mg L^-1, and scavenger type is hole. To ensure the stability of the used catalyst, reusability tests were also carried out. The catalyst reusability tests revealed that the Fe₃O₄/SnO₂/NGP 10wt.% composite could be repeatedly used up to four times without any significant change in the sonocatalytic and sonophotocatalytic activity.