An Eco-approach synthesis of undoped and Mn doped ZnO nano-photocatalyst for prompt decoloration of methylene blue dye

Abstract

The present work reports the synthesis of nano pure ZnO and Mn-doped ZnO in an Eco-approach using seed extract of Cassia angustifolia for the removal of methylene blue. The aqueous Phyto-molecules helps in the reduction of metal precursor to nano-photocatalyst zinc oxide and the changes in absorbance was noted in UV-DRS for varying the parameters to get optimized. Different concentrated dopant material manganese sulphate (0.001 M, 0.003 M, and 0.005 M) was introduced on ZnO to enhance the optical absorption and to generate a new Fermi level. The XRD data exhibit the same wurtzite pattern for pure ZnO and Mn-doped ZnO samples. The slight shift in peak positions was noted in Mn-doped ZnO samples compared to pure ZnO without additional peaks determines the incorporation of Mn2+ ions in the lattice of ZnO NPs. The peak appearance in FT-IR denotes the bond formation among functional groups and metal oxide. The structural morphology of ZnO and Mn-doped ZnO was observed in Field Emission Scanning Electron microscopy. The elemental composition of Mn in ZnO was predicted in the EDAX. The High-resolution transmission electron microscopy (HRTEM) denotes the reduced size and altered the crystallinity of ZnO when Mn was introduced as the dopant in the green route. The effective photocatalytic activity of nano ZnO, Mn-doped ZnO achieves 84 and 95% decoloration of water pollutant Methylene blue (MB) dye with H2O2 and UV radiation by changing parameters like dye concentration, amount of catalyst, and pH. Results from this study suggest that the nano- Mn-doped ZnO photocatalyst can be advantageous for dye removal compared to pure ZnO. The green synthesized Mn-doped ZnO using Cassia angustifolia seed might considerable for treating dye contaminated water and supports in water remediation.