Functional Photocatalytic Surfaces for Selective Adsorption and Detection of Organic Pollutants

The dissertation focuses on using unique surface wettability properties to remove oil contamination from water. Three main ideas are explored. In Publication 1, a two-step photocatalytic reduction process creates hierarchical Au nanostructures on a TiO2 film, resulting in a stable surface with superhydrophobic properties. This surface is useful for self-cleaning and anti-icing technologies, as well as applications in cell growth and fluid microchips. Publication 2 introduces a "3-in-1" concept, combining a photocatalytic thin film, micro/nanostructuring, and a low surface energy coating. The resulting surface exhibits superhydrophobicity and photocatalytic activity, suitable for oil-water separation, self-cleaning, and water harvesting. The p-V3D3 coating's stability under UV irradiation and atomic oxygen exposure is advantageous. Publication 3 presents a 4N-in-1 hybrid substrate (AgTiO2) for enhanced Raman spectroscopy. This hybrid substrate achieves significant enhancement, high detection sensitivity, superior photocatalytic degradation performance, and long-term reusability.In summary, this dissertation explores the development of surfaces with unique wettability properties for oil-water separation, self-cleaning, water harvesting, and ultrasensitive Raman spectroscopy. The fabricated surfaces demonstrate improved hydrophilicity, superhydrophobicity, and photocatalytic activity, leading to enhanced performance in various applications

Sewage sludge heavy metal analysis and agricultural prospects for Fiji

Insoluble residues produced in Waste Water Treatment Plants (WWTP) as by products are known as sewage sludge (SS). Land application of SS, particularly in agricultural lands, is becoming an alternative disposal method in Fiji. However, currently there is no legislative framework governing its use. SS together with its high nutrient and organic matter contents, constitutes some undesired pollutants such as heavy metals, which may limit its extensive use. The focus of this study therefore was to determine the total concentrations of Pb, Zn, Cd, Cu, Cr, Ni and Mn in the SS produced at the Kinoya WWTP (Fiji) and in the non-fertile soil amended with the SS at 20, 40, 60, 80% application rates and in the control (100% Soil). The bioavailable heavy metals were also determined as it depicts the true extent of metal contamination. The treatment mixtures were then used to cultivate cabbage plants in which the total heavy metal uptake was investigated. Total Zn (695.6 mg/kg) was present in the highest amounts in the 100% SS (control), followed by Pb (370.9 mg/kg), Mn (35.0 mg/kg), Cu (65.5 mg/kg), Cr (20.5 mg/kg) and finally Cd (13.5 mg/kg) and hence a similar trend was seen in all treatment mixtures. The potential mobility of sludgeborne heavy metals can be classified as Ni > Cu > Cd > Zn > Mn > Cr > Pb. Total metal uptake in plant leaves and stems showed only the bioavailable metals Cu, Cd, Zn and Mn, with maximum uptake occurring in the leaves. Ni, despite being highly mobile was not detected, due to minute concentrations in the SS treatments. Optimum growth occurred in the 20 and 40% SS treatments. However maximum Cu and Mn uptake occurred in the 40% SS treatment thereby making the 20% treatment the most feasible. Furthermore the total and bioavailable metal concentrations observed were within the safe and permitted limits of the EEC and USEPA legislations