(555a) Photocatalytic Oxidation of Rhodamine B Over P-Doped Titania Nanotubes

Pure titania nanotubes and nanotubes doped with different metals like Cu, Zn, Cr, Fe etc. and non-metals like N, S, C have gained much attention in recent years. In this work, titania nanotubes (TNTs) were first synthesized with a hydrothermal method, then doped with phosphorous using dimethyl phosphite in ethanol solution and calcined at 350oC for 1 hour. TEM image of the prepared P-TNTs synthesized at 180oC show tube formation with 25-50nm OD and 400-1500 nm length. XRD analysis revealed peaks characteristic of monoclinic sodium titanate oxide (Na2Ti3O7 and Na2Ti6O13) phases, which could correspond to the H2Ti3O7 monoclinic unit cell structure or the orthorhombic protonic lepidocrocite phase. Surface areas of TNT (@180C) and P-TNT are 100 and 105 m2/g, respectively, while TNTs (@130C) have a surface area of 306.65 m2/g. The photocatalytic activities of the P-doped TNT (P-TNT) were tested with the degradation of Rhodamine B (C28H31ClN2O3), a dye commonly used as a tracer and a fluorescence agent, in water. Liquid samples were analyzed with a CARY 50 UV-VIS spectrometer. The optimum phosphorous content was found to be 0.75 wt %. P-TNTs (synthesized at 130oC, with 0.75wt% Phosphorous) has the highest activity when compared with undoped TNTs and Degussa P-25 nanoparticles (NP). A UV filter was used to cut off the UV light below 400nm from a 9W fluorescent lamp (Philips PL-S) and the results confirm the P-doped TNTs have better visible-light activities than P-25 TiO2 NP.