Degradation of organic pollutant through ternary metal oxides nanocomposite (MgO–CaO–CoO) photocatalyst synthesized using <i>Daucus carota</i> pomace extract

Abstract In this work, ternary nanocomposite MgO–CaO–CoO has been synthesized via a green approach using Daucus carota pomace extract as reducing and capping agent. The structure, morphology, average particle size and elemental composition of the synthesized nanocomposite were determined using different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The Fourier transform infrared spectrophotometer spectrum showed stretching vibrations of metal oxide bonds such as Co–O, Mg–O and Ca–O at 666 cm −1 , 694 cm −1 and 721 cm −1 which confirmed the synthesis of CaO–MgO–CoO nanocomposite. X-ray diffraction study validated the crystalline structure of the ternary nanocomposite, revealing an average crystallite size of 20.33 nm. The scanning electron microscopy study revealed irregular agglomerated stone-like morphology that confirmed the formation of ternary nanocomposite. Energy-dispersive X-ray spectroscopy was used to analyze the elemental composition. The presence of elements such as calcium (Ca), magnesium (Mg), cobalt (Co), and oxygen confirmed the presence of Ca–O, Mg–O, Co–O in the synthesized nanocatalyst. The photo-catalytic activity of ternary nanocomposite (CaO–MgO–CoO) was assessed for degradation of organic pollutant, specifically RhB, under sunlight exposure. Effects of various parameters such as photocatalyst dose (5–20 mg L −1 ), solution pH (3–11) and irradiation time (30–180 min) on the extent of removal of dye showed a high degradation efficiency of 97 %. It has been deduced through a scavenger experiment, utilizing DMSO and ASC as scavenger for hydroxyl radicals (•OH) and oxide (O 2 − ) radicals respectively, that hydroxide and oxide radicals are the main reactive species in the photodegradation process.