Application of Surface Modification of Titanium Dioxide Nanotube Photodegradation Dye Wastewater via Hydrothermal Synthesis

In this study, TNT was synthesized by a hydrothermal method from commercial Degussa P-25 TiO2 nanoparticles. Moreover, SnO2, Al2O3, FeCl2, were utilized as precursors to modify the surface of TNT. Various TNT composites were synthesized by three stages：(1)after the hydrothermal process, the sample was washed with DI water and 0.1 N, 0.5 N or 1.0 N HCl, respectively, (2)different content (5, 10, 20 wt.%) SnO2 mixed P-25 as precursors for producing SnO2/TNT composites, which HCl 0.5 N as acid washing concentration, and (3) 5 wt.% SnO2, Al2O3, FeCl2 and P-25 as precursors for synthesizing Sn-TNT, Al-TNT, and Fe-TNT respectively under 0.1 N HCl treatment. The physical and chemical properties of all prepared samples were analyzed by X-ray diffraction spectra (XRD), nitrogen adsorption-desorption isotherm, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM, HR-TEM), UV-visible spectrometry (UV-vis), electron spectroscopy for chemical analysis (ESCA), fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). The photocatalytic performance of sample was evaluated through degradation of organic dyes comprised of methylene blue (MB), Congo red (CR), crystal violet (CV). After hydrothermal treatment, the BET surface area of TNT series samples significantly grew from 55 m2/g (raw P-25) to around 300 ~ 400 m2/g, with an increase of 6 ~ 7 times. The TNT exhibited a hollow tubular shapethat both sides open with a diameter around 5 nm and length 100 ~ 200 nm. The MB photodegradation efficiencies of basic TNT samples were around 60% ~ 80% under UV irradiation. In contrast, Sn5-TNT possessed the highest photodegradation efficiency in this study, which was approximately 96% removal. PL analysis result indicated that the rate of recombination of e-/h+ pair was decreased with the presence of SnO2 as precursors. This was due to the hetero junction relation between SnO2 and TNT which was formed during hydrothermal treatment. Furthermore, the MB photodegradation conformed the first-order reactions equation.