Study On Reactor For Photocatalytic Wastewater Treatment With TiO₂-Coated Side-Glowing Optical Fibers

To expand the application of optical fiber photocatalytic reactors (OFR) in wastewater treatment, this dissertation aims to construct a novel OFR. A quite simple route was developed to prepare anatase TiO₂ sols at low temperature. Furthermore, depositing directly photocatalytic TiO₂ thin films on polymer substrates from anatase TiO₂ sols was studied. A novel optical fiber photocatalytic reactor was constructed using a bundle of side-glowing optical fibers, which can provide side UV radiation along the whole fiber length, with attachment of light sources at both fiber ends. The photocatalytic experiments were carried out in the reactor using reactive brilliant red dye X-3B as a model compound. The main works and achievements are presented as follows: Anatase TiO₂ sols were synthesized under mild conditions (i.e. 75°C and ambient pressure) by hydrolysis of titanium-n-butoxide (Ti(OBu)4) in abundant acidic aqueous solution and subsequent reflux to enhance crystallization. The preparation process was quite simple and a low-temperature route. The influences of various acidities, reflux time, and molar ratios of water to Ti(OBu)4 on size, micro-morphology, and crystal structure of the obtained TiO₂ sol particles were investigated. At low temperature TiO₂ thin films were deposited on quartz glass slides from the anatase TiO₂ sol by a dip-coating method. The TiO₂ thin films exhibited good photocatalytic activities in the degradation of X-3B in aqueous solution under aerated conditions.At room temperature and in ambient atmosphere, TiO₂ thin films were deposited on polymethylmethacrylate (PMMA), SiO₂-coated PMMA and SiO₂-coated silicone rubber substrates from the anatase TiO₂ sol by a dip-coating process. The surface property of the substrates affects the adhesion of the TiO₂ thin films. SiO₂ layers prior to TiO₂ thin films on the polymer substrates could not only protect the substrates from the photocatalytic decomposition of the TiO₂ thin films, but also enhance the adhesion of the TiO₂ thin films to the substrates due to its comparatively hydrophilic surface and thus favors the deposition of TiO₂ thin films. All the TiO₂ thin films showed good photocatalytic activities, which indicates anatase TiO₂ sols can be used to deposit directly photocatalytic TiO₂ thin films on polymer sustrates such as silicone rubber at room temperature. Mixing a certain quantity of microspheres into the silicone buffer cladding, single-cladding side-glowing optical fibers with core diameter of 200μm and external diameter of 360μm were fabricated. Mixing a certain quantity of SiO₂ nanoparticles into the fluoroplastic cladding, double-cladding side-glowing optical fibers with core diameter of 200μm, inner fluoroplastic cladding diameter of 250μm and outer silicone buffer cladding diameter of 380μm were fabricated. Anatase TiO₂ nanoparticles were deposited on side-glowing optical fibers by means of TiO₂-layer-on-SiO₂-layer. FE-SEM images show that the double layers adhered well to the side-glowing optical fiber, and the TiO₂ coating was homogeneous and smooth. The decomposition...