Ilmenite type nano-crystalline Co–Ti–O ternary oxides: sol–gel thin film on borosilicate glass, characterization and photocatalytic activity in mineralization of reactive red 198

The sol–gel preparation of cobalt titanium oxide nano-crystals using the reaction between cobalt chloride (CoCl₂·6H₂O) and tetraisopropyl orthotitanate (Ti[OCH(CH₃)₂]₄) with 1:1 molar ratio was studied. The nano-crystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDAX), fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG-DTG) analysis and UV–Vis diffuse reflectance spectra (UV–Vis DRS) spectroscopy. TG-DTG results revealed that the weight loss with peak temperatures of 189, 267 and 692 °C. The XRD results showed that the sample calcinated at 550 and 750 °C were mixtures of CoTiO₃, Co₃O₄, and TiO₂ phases while at 650 °C a single crystalline phase of CoTiO₃ was formed. FESEM results of the cobalt titanium oxide nanocrystalles demonstrate that CoTiO₃ is nano-particles with an average size of 70 nm. FTIR results showed the formation of cobalt–oxygen, titanium–oxygen, and titanium–oxygen–cobalt bonds. DRS spectroscopy results of the sample calcinated at 650 °C showed band gap of 1.734 eV (715 nm) and 2.389 eV (519 nm) well in the visible portion of sun light. The cobalt titanium oxide nano crystales thin films on borosilicate glass showed an excellent photocatalytic activity on mineralization of Reactive Red 198 textille dye as environmental pollutant of industrial wastewater. An excellent photocatalytic activity in mineralization of Reactive Red 198 is related to the efficient separation of cobalt titanium oxide nano-crystals and visible-light absorption.