TiO 2 decorated functionalized halloysite nanotubes (TiO 2 @HNTs) and photocatalytic PVC membranes synthesis, characterization and its application in water treatment

Abstract

In this study photocatalyst, TiO 2 @HNTs were prepared by synthesizing TiO 2 nanoparticles in situ on the functionalized halloysite nanotubes (HNTs) surface. Photocatalytic PVC membrane TiO 2 @HNTs M2 (2 wt.%) and TiO 2 @HNTs M3 (3 wt.%) were also prepared. Photocatalyst TiO 2 @HNTs and photocatalytic PVC membranes were used to study the photocatalytic activity against the methylene blue (MB) and rhodamine B (RB) dyes in UV batch reactor. The structure and morphology of photocatalyst and photocatalytic PVC membrane were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), UV-Vis spectrophotometer and photoluminescence (PL). The PL study showed that the oxygen vacancies and surface hydroxyl groups present on the surface of TiO 2 @HNTs act as excellent traps for charge carrier, reducing the electron-hole recombination rate.TiO 2 @HNTs 2 (2 wt.%) and TiO 2 @HNTs 3 (3 wt.%) degraded MB dye up to 83.21%, 87.47% and RB dye up to 96.84% and 96.87%, respectively. TiO 2 @HNT photocatalyst proved to be stable during the three consecutive cycle of photocatalytic degradation of the RB dye. TiO 2 @HNTs M2 and TiO 2 @HNTs M3 degraded MB dye up to 27.19%, 42.37% and RB dye up to 30.78%, 32.76%, respectively. Photocatalytic degradation of both the dyes followed the first-order kinetic model. Degradation product analysis was done using the liquid chromatography–mass spectrometry (LC-MS) and the results showed that the dye degradation was initiated by demethylation of the molecule. MB and RB dye degradation reaction were tested by TBA and IPA as OH * and H + scavengers respectively. Mechanism of photocatalytic activity of TiO 2 @HNTs and photocatalytic PVC membrane were also explained.