Heterogeneous sono-Fenton-like process using magnetic cobalt ferrite reduced graphene oxide (CoFe2O4-rGO) nanocomposite for the removal of organic dyes from aqueous solution

We report herein the synthesis of monodisperse cobalt ferrite (CoFe2O4) nanoparticles (NPs) via a surfactant assisted high temperature thermal decomposition method and then their assembly on reduced graphene oxide (rGO) to yield CoFe2O4-rGO nanocomposites, which displayed outstanding sonocatalytic activity for the removal of organic dyes from aqueous solutions under ultrasonic irradiation. As -prepared CoFe2O4-rGO nanocomposites were characterized by using transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Micro-Raman spectroscopy, Vibrating sample magnetometer (VSM) and inductively couple plasma mass spectrometer (ICP-MS). To evaluate the sonocatalytic activity of the CoFe2O4-rGO nanocomposites, the sonocatalytic removal of several organic dyes (AO7, AR17, BR46 and BY28) was studied. The reaction conditions were optimized by studying the effects of various key operating parameters such as pH, catalyst dosage, H2O2 initial concentration, initial dye concentration, ultrasonic power and reaction time on the removal of AO7 dye. The maximum removal efficiency of 90.5% was achieved at pH 3 using 0.08 g L-1 catalyst, 3 mM H2O2 and 10 mg L-1 AO7 dye under 350 W ultrasonic power in 120 min of reaction time span. Experimental results revealed that the kinetic of the removal process could be described using Langmuir-Hinshelwood (L-H) kinetic model. The trapping experiments showed that O(2)(-)radicals constitute the major reactive oxygen species (ROS) in the AO7 dye removal process. The reusability of the nanocomposites revealed about 22% drop in the removal efficiency within five consecutive runs. A possible sonocatalytic mechanism for the removal of organic dyes was also proposed. The intermediate by-products of the dye formed in the removal process were characterized by using the GC-MS technique.