Photocatalytic activity of graphene lanthanide orthovanadate nano hybrids for water purification

Abstract

newline xix newlineABSTRACT newlineThe present research work has been focused onfabricating fluorine doped graphene LnVO4 nanocomposites for environmental application. EV, GV, and SV nanoparticles were successfully dispersed over few layered fluorine doped graphene sheets to synthesize EV/FG24, GV/FG24, and SV/FG24 nanocomposite using simple hydrothermal method. Few layered fluorine doped graphene sheets were prepared by sonochemical exfoliation method using NaF as fluorine source. The synthesized nanocomposites were successfully characterized by modern highly sophisticated instrumental techniques such as scanning electron microscopy (SEM) which gathers the structural and morphological evidences of the nanoparticles, transmission electron microscopy (TEM) which provide the useful information about the size, shape, crystallinity, and morphological nature of the nanoparticles, Fourier transform infrared spectroscopy (FTIR) which is used to ascertain chemical composition of a nanostructure, X-ray diffraction (XRD) to study crystalline nature and size of the nanocomposites, Atomic force microscopy (AFM) to estimate thickness and lateral size of nanocomposites,X-ray photoelectron spectroscopy (XPS) to inquires the elemental composition of nanocomposites, Thermogravimetric analysis (TGA) to assess the thermal stability of nanocomposites, Brunauer, Emmett, and Teller (BET) to analyse specific surface area, Photoluminescence spectroscopy (PL) was prefer using fluorescence spectrometer, High performance liquid chromatography analysis (HPLC) was performed to analyse the degradation products. newlineThe atomic force microscope analysis depicted that thickness of FG24, EV/FG24, GV/FG24, and SV/FG24 was less than 2.0 nm. The band gap of EV/FG24, GV/FG24, and SV/FG24 was 2.19 eV, 2.10 eV and 2.28 eV, respectively. The high dispersion of synthesized nanocomposites in water was ascertained by zeta potential measurement and Tyndall scattering experiment. Photocatalytic properties of EV/FG24, GV/FG24, and SV/FG24 were tested for the degradation of phenolic compounds and bacterial disinfection under visible light. Contrary to conventional slurry type photo-reactors, no magnetic stirring was used during photocatalytic reactions. The photodegradation process followed pseudo first order kinetics as confirmed by kinetic studies. The photodegradation rate was substantially influenced by adsorption of DMP, phenol, DCP, and DNP onto EV/FG24, GV/FG24, and SV/FG24 surface. The simultaneous adsorption and photocatalysis was most efficient newlinexx newlineprocess for degradation of selected phenolic compounds under visible light. The selected phenolic compounds were completely mineralized in 10 h. The photocatalytic activity of EV/FG24, GV/FG24, and SV/FG24 was also tested for bacterial disinfection using Escherichia coli, Bacillus subtilis,Pseudomonas fluorescence, Staphylococcus aureus and Streptococcus enterica bacteria. The selected bacteria were deactivated within 3 h under LED light. The effect of various radical scavengers revealed the pivotal role of hydroxyl radicals and superoxide radical during disinfection mechanism. High performance liquid chromatography and mass spectrometry confirmed the formation of intermediate formed during degradation process which ultimately mineralized into CO2 and H2O. EV/FG24, GV/FG24, and SV/FG24 exhibited significant recycle efficiency upto 10 catalytic cycles during photocatalytic process and was used as a stable photocatalyst to depollute contaminated water. Further, due to high dispersion and recyclability, EV/FG24, GV/FG24, and SV/FG24 could be used as an efficient photocatalyst for removal of both biotic and abiotic pollutants present in water. newlineKeywords: Fluorine doped graphene sheets, EuVO4, SmVO4, GdVO4, Photocatalysis, Phenolic compounds degradation, Bacterial disinfection.