Mugadza, FariraiFarirai, Mugadza2021-05-042021-05-042020Mugadza, Farirai (2020) Photocatalytic degradation of methyl violet using modified radially aligned nano rutile TiO2-nanodiamonds composite, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/31090>https://hdl.handle.net/10539/31090A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Chemistry, University of the Witwatersrand, 2020In this work, a hydrothermal method was used to synthesize the radially aligned nano rutile (RANR) TiO2,usingTiCl4as a precursor. The synthesis temperatures, as well as the time involved in the refluxing step of the synthesis were varied to obtain the optimum morphology of the resulting TiO2. The optimum refluxing time for RANR TiO2 synthesis was determined to be 16 hours at 180°C. The synthesized RANR TiO2 with dandelion-like shapes had diameters ranging from 300 nm to 800 nm and an average diameter of 560 nm. The RANR TiO2 had BET surface area of 68 m2/g, which is higher than that of the commercially available Degussa P25 (45 m2/g).The RANR TiO2-nanodiamond composites were all synthesized in situ using the hydrothermal method with detonation nanodiamonds ranging from 0.1 to 1% mass loading. BET surface area analysis showed an increase in the surface area of the RANR TiO2 with an increase in the amount of nanodiamonds used in its modification. Raman spectra confirmed the presence of graphitic carbon and rutileTiO2in all the composite samples. The results obtained from XPS analysis showed that oxygen, carbon and titanium were all present in the sample but there was no evidence showing bond formation between titanium and carbon. RANR TiO2 was the most effective in dye degradation due to their nano rod structure, which increases light harvesting properties due to multiple reflections of light. All the other composites did generally well with respect to dandelions in the first hour, but then the rate of degradation decreased which could be attributed to the reduction in photocatalytic active sites due to blockage by reactants. A good dispersion of the nanodiamonds and RANR TiO2(0.1% loading) helped to create strong electronic interphase interactions. This helps to separate the photogenerated electrons and positive holes, thereby increasing photocatalytic efficiency. Calcination increased photocatalytic efficiency because of the increase in crystallinity of materials which reduces electron/hole recombination, the increase in crystallinity was shown by results from Raman spectroscopy. The photocatalyst recyclability studies showed that the recovery of the catalyst after each cycle and the re-use was not effective as the degradation efficiency decreased from 80% to 60% after 3 cyclesOnline resource (86 leaves)enCatalystsNanostructured materialsThesis