Badreldin, Ahmed Sherif (2019-07). Optimized Design and Synthesis of Photocatalytic Modified Black Titania for Water Treatment. Master's Thesis.
Thesis
Organic contaminants in water sources are perhaps amongst the most damaging presences in untreated waters due to their effects in fouling membranes and significantly increasing operational costs of water treatment facilities. Conventional treatment processes such as adsorption do not eliminate the contaminants from the environment, but simply transform them from the water phase to another phase. Heterogenous photocatalysis is a rather an attractive method for effectively mineralizing/degrading those organic contaminants via the illumination of solar light. Titania (TiOv2) is amongst the largest used and sought after photocatalysts due to its relatively high photoactivity. However, crippled by a fast electron-hole recombination rate and their activation is limited to the UV light which represents only about 5% of solar energy available, titania based photocatalysts have found a towering hinderance in entering commercial employment. The design, development and performance evaluation of photoactive titania nanostructures that employ both UV and visible segments of the solar energy spectrum have been successfully carried out in this research work. The incorporation of multiwalled carbon nanotubes (MWCNTs) whilst maintaining a highly heterojunctioned and low aggregated structure was achieved via the investigation of factors that affect this nanocomposite. Furthermore, in order to increase the commercial appeal of the developed photocatalyst, a silica-coated paramagnetic iron oxide core was used to mount the photoactive black titania nanowires with incorporated MWCNTs (bTNW/MWCNT@SiOv2@Fev3Ov4). In this way, a small magnetic field can easily collect all the solid photocatalysts in solution upon complete treatment of the water and recycle them to treat additional water volumes. Photodegradation experiments were conducted in batch, using methylene orange (MO) as a mimicking agent organic contaminant. For each photodegradation experiment, 50 mL of 10 ppm MO contaminated synthetic waters were used, with a catalyst load of 1 g/L, an artificial solar intensity of 700 W/m^2 , and a maintained pH value of 7 were used. Aliquots were collected with respect to time and the concentration of contaminant remaining was determined using a liquid UV-Vis-NIR technique. The final developed stand-alone black titania nanowires with incorporated MWCNTs (bTNW/MWCNTs) were found to yield a photodegradation efficiency of 97.4% in 20 minutes of solar irradiation, whilst the composite bTNW/MWCNT@SiOv2@Fev3Ov4 yielded a photodegradation efficiency of 90.68%. The developed materials were thoroughly characterized via XRD, XPS, SEM, TEM, solid-state UV-Vis-NIR, elemental mapping, and FTIR. This allowed for the progressive monitoring of the different changes in design parameters that were undergoing from each successive synthesis step in order to better depict a clearer understanding of the importance and physical contributions these design parameters have on apparent photodegradation efficiency.
