High performance of magnetically separable and recyclable photocatalyst of green-synthesized CoFe ₂ O ₄ /TiO ₂ nanocomposites for degradation of methylene blue

Abstract

Abstract In this study, combination of ferromagnetic and semiconductor CoFe 2 O 4 /TiO 2 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 CoFe 2 O 4 /TiO 2 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 CoFe 2 O 4 and TiO 2 , respectively. The crystallite sizes of CoFe 2 O 4 , CoFe 2 O 4 /TiO 2 , and CoFe 2 O 4 /3TiO 2 are 7.2 nm, 8.6 nm, and 11.1 nm, respectively. The magnetic hysteresis curve showed that CoFe 2 O 4 /TiO 2 had a high saturation magnetisation of 27 emu g −1 and a coercivity of 200 Oe. The optical bandgap energy for CoFe 2 O 4 /TiO 2 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 TiO 2 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 CoFe 2 O 4 and TiO 2 . 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.