High performance of magnetically separable and recyclable photocatalyst of green-synthesized CoFe2O4/TiO2 nanocomposites for degradation of methylene blue

Abstract

In this study, combination of ferromagnetic and semiconductor CoFe2O4/TiO2 nanocomposites was synthesised using a green synthesis method with Moringa oleifera leaf extract to easily obtain a magnetically separated nanomaterial exhibiting high photocatalytic activity. Nanocomposites with different CoFe2O4/TiO2 molar ratios were identified using x-ray diffraction (XRD), transmission electron microscopy, X-ray fluorescence, Fourier transform infrared spectroscopy, UV–visible spectroscopy, and vibration sample magnetometer. The XRD spectrum confirmed the structure of the cubic spinel ferrite and anatase phases of CoFe2O4 and TiO2, respectively. The crystallite sizes of CoFe2O4, CoFe2O4/TiO2, and CoFe2O4/3TiO2 are 7.2 nm, 8.6 nm, and 11.1 nm, respectively. The magnetic hysteresis curve showed that CoFe2O4/TiO2 had a high saturation magnetisation of 27 emu g−1 and a coercivity of 200 Oe. The optical bandgap energy for CoFe2O4/TiO2 was in the range 3.6–3.8 eV. Photocatalytic investigations were carried out using methylene blue (MB) under UV irradiation. Our results showed an increase in MB degradation with increasing TiO2 concentration. The maximum photodegradations using nanocomposites are 60.8%, 97.7%, 98.4%, 98.5%, and 98.7% at molar ratios of 1:0, 1:1, 1:2, 1:3, and 1:4, respectively, after 20 min. The increase in MB degradation was related to the formation of internal structures between CoFe2O4 and TiO2. The magnetic nanocomposites enabled separation between the photocatalyst and final degraded solution using a permanent magnet. When the degradation was above 90%, the nanocomposites could be recycled three times.