Green synthesis and characterisation of ZnMn2O4 nanoparticles for photocatalytic degradation of Congo red dye and kinetic study

In this work, ZnMn2O4 spinel nanoparticles were successfully synthesised by tragacanth gel through the easy and inexpensive novel sol-gel method. This technique has many strong points such as facile, economical, non-toxic and quickness in comparison with other methods. The zinc manganite nanoparticles were characterised by X-ray powder diffraction (XRD), transmission electron microscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy. The XRD pattern confirmed the formation of spinel tetragonal structure of ZnMn2O4 nanoparticles with a crystallite size of 14 nm. The degradation of Congo red dye by synthesised nanoparticles was studied using employing UV-Vis spectroscopy. The ZnMn2O4 NPs expressed high photocatalytic activity for degradation of Congo red dye at room temperature in aqueous solution so that 96% of Congo red was degraded in 15 min. The spinel ZnMn2O4 photocatalyst provided total organic carbon removal as 45.2% in 15 min. The spinel ZnMn2O4 NPs reusability was examined by administering the degradation of Congo red dye with the spent catalyst and it was considered that the photocatalyst did not exhibit any significant reduction in its activity even after three cycles.