Green synthesis of MnCr2O4 nanoparticles using Vernonia amygdalina (bitter leaf) for photocatalytic crystal violet dye degradation

Various environmental concerns have emerged today as a result of the developing industrial revolution. The use of hazardous oxidizing agents and organic dyes is one of the biggest problems facing the textile industry today. This approach needs effective and affordable system to degrade such organic pollutants from the point sources. In this work, MnCr2O4 nanoparticle is synthesized using a green method for a crystal violet dye removal from wastewater. Three nanoparticle samples (CMO-A, CMO-B and CMO-C) were synthesized via green synthesis using bitter leaf extract and different concentration (0.3 M, 0.4 M, and 0.5 M) of KMnO4. The structural, morphological, optical properties, and photocatalytic activity of the synthesized MnCr2O4 spinel were studied. X-ray diffraction (XRD) was used to examine the crystal structure and the MnCr2O4 spinel exhibits cubic symmetry (Fd3m). The lattice parameters, crystallite size, microstrain, and dislocation density of the produced nanoparticles were also assessed using the diffraction data. The bandgap energy of the MnCr2O4 spinel decreased from 1.96 to 1.81 eV as the concentration of Mn ion increases from 0.3 to 0.5 M. The MnCr2O4 spinel showed good absorbance of light in visible range and also showed excellent photodegradation of crystal violet dye solution, with a record of 62.6%, 68.4%, and 74.9% degradation efficiency for CMO-A, CMO-B, and CMO-C, respectively, after 130 min of irradiation time.