Abstract
M.Sc. (Nanoscience)
Environmental pollution (i.e. water pollution) has been an issue of great concern across the globe. Water scarcity is reported to be a huge challenge throughout the world. The South Africa water capacity will decrease dramatically in the next 10 years due to various pollutants. Dye molecules such as Methyl Blue (MB) and Rhodamine B (RhB) and heavy metals such as Chromium (Cr(VI)) are reported to be the major cause of water pollution, which results in the scarcity of clean water for human use. These pollutants are present as harmful entities in the environment due to their carcinogenic and mutagenic nature. So, the sustainability of clean water is in greater demand for all forms of life relies upon its availability.
Thus the aim of this study was to synthesize molybdenum sulfide nanostructures and its nanocomposite and evaluate their photocatalytic properties towards water treatment. Molybdenum sulfide nanostructures were synthesized via hydrothermal methods using different capping agents namely Polyethylene Glycol (PEG-400) and Ethylenediaminetetraacetic acid (EDTA) and the samples were named PEG-MoS2 and EDTA-MoS2 respectively. The nanocomposite was synthesized from EDTA-MoS2 and manganese chloride. As synthesized nanostructures and nanocomposite were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning electron microscope (SEM) equipped with Energy dispersive X-ray spectroscopy (EDS), Transmission Electron Microscope (TEM), and UV-Vis Spectroscopy.
Rhodamine B and Methyl Blue were chosen as a model dyes for evaluation of photocatalytic degradation performance. Using PEG-MoS2, the degradation efficiency of 97.30% was achieved for RhB in 75 min and 98.05% for Methyl Blue was achieved in 90 min. EDTA-MoS2 also shows greater potential in the removal of both RhB and MB in aqueous solution; hence 85.46% and 99.78% removals of RhB and MB dyes respectively were achieved in 90 min. PEG-MoS2 nanostructure was also tested for the photocatalytic reduction of Cr(VI) and shows the reduction efficiency of 91.05% in 75 min. The nanocomposite was tested for the photocatalytic degradation of RhB, and results show the degradation efficiency of 98.78% in 75 min. All photocatalytic studies were done under visible light irradiation (Xenon lamp was used throughout).