Montmorillonite/TiO2 nanotubes could enhance the photocatalytic activity of rhodamine B degradation in the UVC region

Abstract

MMT/TiO2-NTs nanocomposite materials were prepared by a simple wet agitation method at room temperature from TiO2 nanotubes and montmorillonite (MMT). The synthesized MMT/TiO2-NTs samples were used as a catalyst for the photocatalytic degradation of rhodamine B (RhB) under a UVC light source (15 W, 254 nm). MMT was purified from bentonite clay (Lam Dong, Vietnam). MMT after purification possessed a characteristic lattice surface (001) at an angle of 2 = 6.1°. The adsorption capacity and the basal spacing of MMT were 70 mg/g and 14.48 Å, respectively. The TiO2 nanotubes (TiO2-NTs) were synthesized by the hydrothermal method. TiO2-NTs possessed a polycrystalline structure consisting of two phases, anatase and rutile. The average diameter and the length of the TiO2-NTs were 5 nm and 110 nm, respectively. The results on the composition, surface morphology, crystal structure, bonding vibration and photocatalytic efficiency characteristics showed that after modification into MMT, TiO2-NTs were immobilized and randomly distributed on the surface or incorporated in the clay sheets of MMT to form a pillared interlayer clay (PILC) structure. Because MMT possessed good adsorption properties, MMT would act as an adsorption center to capture RhB molecules in clay layers. MMT also prevented the recombination of TiO2 by trapping the photogenerated e into the vacant d orbitals of the metallic elements present in the MMT. Then, the •OH or •O2 radicals generated from the TiO2 photocatalytic reaction would easily react with the RhB molecules and decomposed them. The photocatalytic efficiency of 10 ppm RhB degradation of MMT/TiO2-NTs was 82% when excited by a UVC source for 210 min.