Enhancement of Photocatalytic Removal of 4-Chlorophenol from Aqueous Solutions by Manganese Oxide Doped ZnO Nanoparticles Using RSM

Background: Phenol and its derivatives as a toxic and dangerous substance produce by many industries. This pollutant must be removed from contaminated streams or fluids before discharging. The aim of this study was to enhancement of nano-photocatalytic removal of 4-chlorophenol (4- CP) from aqueous solutions applying manganese oxide doped ZnO nanoparticle (MnO₃-doped ZnO) catalyst via experimental designing of surface-response method. Methods: In this study, MnO₃-doped ZnO NPs were fabricated using hydrothermal technique and ratio of Mn-doped ZnO NPs consisted of 0 (pure), 0.5, 1 and 1.5%. The characteristics of the synthesized NPs was studied by scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses. For determined the doped ZnO quality, variables such as pH, initial 4-CP concentration, NPs dose and contact time were probed in 4-CP removal. Results: Results demonstrate that the removal efficiency are significantly affected by the varied Mn-doped ZnO ratio. The ratio of 1% was optimal. The hexagonal shape of NPs confirmed by XRD and SEM analysis. The SEM indicated that no agglomeration of NPs observed. The sharp edges peaks in XRD indicate a proper crystallized ZnO NPs. Regression analysis showed a quadratic polynomial model was obtained for efficiency prediction. The data providing an acceptable model assumption for analyzing the variance. It was also realized that increasing the nanoparticles dose and the contact time led to reduce the removal rat. Conclusion: Comparing the 4-CP removal efficiency of bare ZnO and Mn-doped ZnO showed that the Mn-doped ZnO have larger efficiency and improve up to 84%.