Facile synthesis of highly active and reusable NiO/montmorillonite photocatalyst for tetracycline removal by photocatalytic oxidation

Abstract

Nanocomposite of dispersed nickel oxide nanoparticles into montmorillonite (NiO/Mt) was synthesized by using hydrothermal impregnation method. The obtained solids were characterized by x-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray fluorescence (SEM-EDX), transmission electron microscope (TEM), C-ray photoelectron spectroscopy (XPS), gas sorption analyzer using N₂ adsorption–desorption at 77 K and UV–Visible diffuse reflectance spectrophotometry (UV-DRS). The prepared material was evaluated as photocatalyst for tetracycline (TC) removal photocatalytic oxidation with activated hydrogen peroxide as the oxidizing agent. The kinetics of TC removal over varied methods, influence of the amount of H₂O₂, and study on photocatalytic mechanism by evaluating effect of scavenger were investigated. Physicochemical characterization recognized that nickel oxide nanoparticles with particles’ size ranging from 10 to 20 nm was homogeneously dispersed in the montmorillonite support as expressed by SEM, TEM and XPS analysis. Small amount of dispersed Ni (4.55 % wt.) does not show the significant improvement to the specific surface area and porosity of the montmorillonite but expresses the band gap energy of 3.5 eV which supports the activity as photocatalyst. It is found that the nanocomposite has excellent photocatalytic activity in TC removal by the removal efficiency of about 94.2 % and 75.5 % under UV and visible light exposure, respectively. The nanocomposite demonstrated recyclability and reusability with no-significant altered activity until 5th use. This work could not only provide a facile method to fabricate low-cost photocatalyst but also contribute to the design for photocatalyst application in pharmaceuticals-contaminated water.