Efficient photocatalytic degradation of Malachite green dye using facilely synthesized cobalt oxide nanomaterials using citric acid and oleic acid

Citric acid and oleic acid modified cobalt oxide nanomaterials successfully fabricated by sol-gel process and used to remove malachite green (MG) by photocatalytic degradation. The synthesized nanomaterials were characterized by powder X-ray diffraction (P-XRD), Scanning electronic microscopy (SEM), Transmission electron microscopy (TEM), UV–Visible spectrophotometer, Fourier transform infrared spectroscopy (FT-IR) and Thermogravimetric Analysis (TGA) in order to investigate their structural, morphological, optical, functional and thermal properties, respectively. The PXRD gave the crystalline nature with average crystallite size of 29 and 42 nm for citric acid and oleic acid modified cobalt oxide nanomaterials, respectively. SEM images indicate layered porous aggregates morphology having higher porosity. Optimum condition for photocatalytic degradation of MG dye were found at pH 6.84, dose 0.5 gL^-1 for 1 × 10⁻⁵ M concentrated dye. Citric acid modified cobalt oxide catalyst exhibited 91.2% photocatalytic degradation of MG dye while in oleic acid modified sample exhibited 66.6% under simulated light due to greater chelating power of citric acid as compare to oleic acid. Kinetics results for MG dye degradation follow to pseudo-second-order kinetics with rate constants 0.00653, 0.084 and 0.00633 mol⁻¹L¹min⁻¹ for CoCA, CoOA and Co NPs, respectively. In addition, possible mechanism for the photodegradation of MG dye is also proposed.