The main objectives of the present study were to prepare titanium dioxide nanotubes (TNs) in large quantities by hydrothermal routes and to characterize the photocatalytic properties, fine structures, formation mechanisms of TNs, and Ag-loaded TNs for enhancing the removal efficiency of dyes, nitrate, nitrite, and three environmental hormones pollutants in wastewaters. From the experimental data of the dye wastewaters removal under UV light irradiation, the photodegradative efficiencies of four kind of dyes solutions on TNs were basic violet 10>basic green 5>methylene blue>acid blue 9. In addition, a simple Langmuir-Hinshelwood was used and calculated to describe the reactions of the dye wastewaters. Basic Violet 10 photodecomposion rate was the highest photocatalytic efficiency with a K of 0.00894/min. Ag/TNs characterized using FE-SEM and TEM showed that the diameter of silver particle was 3-4 nm. The UV/Vis spectra revealed that the maximum adsorption wavelength of TNs was 450-550 nm. By using XANES spectra, the valency and framework of Ag/TNs were Ti(VI) with anatase-type structure, and Ag-O bonding for Ag/TNs. The EXAFS data also revealed that Ag/TNs have a first shell of Ti-O (Ag-O) bonding with a bond distance of 1.95 (2.28) Å and a coordination number of 2 (1.6). From the experimental data of the nitrite/nitrate removal under UV light irradiation, two kind of hole scavengers showed that the photodegradative efficiency of formic acid was higher than the one of oxilic acid. Experimentally, Ag/TNs reacted with nitrate solutions of 60 mg/L originally. The concentrations of nitrate contaminants in solutions decreased obviously onto Ag/TNs. After the reaction of 30 min, the removal efficiency of nitrates in solutions was 70% and reached 100% after 3 h. It notably appeared that the nitrate species was partly converted to ammonia and nitrogen gases. Finally, the basic enginnering design and cost evaluation for a large-surface aligned Ag/TNs thin film/UV-Vis photocatalytic reactor system were primarily performed in order to enhance the localized decontamination abilities and technologies in Taiwan

Titania nanotube, Photocatalyst, Adsorption, Photocatalysis, Silver nanoparticle, Hydrothermal method, Dye, Nitrite, Nitrate, Environmental hormone, XANES/EXAFS