Tunali, Feyza; (2018) Synthesis of different photocatalytic or superhydrophobic materials for environmental applications. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis details the development of different novel systems for environmental applications. Firstly, the synthesis of TiO2 photocatalyst thin films was achieved on glass slides, glass frit and glass wool by immersed into a Ti-containing sol followed by annealing processes to obtain potent photo-active surfaces. Secondly, Silicalite-1 (S1) coatings were prepared on the glass slide and glass wool by hydrothermal synthesis and subsequently immersed into a Ti-containing sol to create a silica fibre core surrounded by concentric layers of S1 and TiO2 to increase their specific surface area and roughness which led to an improved photocatalytic activity. Thirdly, highly efficacious UV-light activated photocatalytic surfaces were prepared by mixing commercial P25 TiO2 nanopowder and polydimethylsiloxane (PDMS). The resulting samples were characterized by standard characterization techniques such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area measurement. The samples were evaluated using different photocatalytic tests including the intelligent ink test, degradation of stearic acid, removal of heavy metal, adsorption and degradation of 4-chlorophenol (4- CP) and cinnamic acid under UVA light (l = 365 nm) for photocatalytic applications. The observed results showed that the modified samples have potential use in water cleaning applications. Lastly, an optimized superhydrophobic material was generated by the S1 roughening and subsequent hydrophobic surface treatment of silica filter membranes for water-oil separation systems. The material is both highly rough and intrinsically hydrophobic, resulting in superhydrophobic membranes which show a substantial affinity for hydrophobic solvents and oils. The membranes are syringe-mounted, suction pressure is applied and the selective collection of oil is achieved. The membranes are extremely robust, which is a result of the zeolitic roughening process, they possess small pores (0.7 μm), thus these devices can perform complete separation and operate at a range of suction pressures. The devices could be readily used in a range of real-world applications, including oil spill clean-up and industrial filters.

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