Biomass-Mediated Metastable Zinc(II) Oxide Nanoparticles and Its Nanocomposites for Sustainable Water Treatment

Water is undeniably the most crucial resource that allows all living entities to thrive and survive. Due to a continuously growing population and the expansion of industrial sectors, water pollution has emerged as a global issue. Consequently, people face challenges in obtaining the required quantity and quality of water for their daily activities such as drinking, cooking, hygiene, and agriculture. Hence, there is a compelling need to develop an effective and environmentally friendly approach to eliminate harmful pollutants in water, promoting the establishment of a sustainable society with widespread access to clean and safe water resources. Although there are a lot of existing available water treatment facilities to ensure the provision of potable water, the establishment and maintenance of such facilities come at a significant cost with advanced instrumentation and labor-intensive techniques. To effectively address these issues, the integration of advanced functional nanomaterials, coupled with the application of nanotechnology could facilitate the potential solutions for the wastewater treatment processes. This approach can contribute to the advancement of water treatment technologies and the development of sustainable water management strategies. This dissertation primarily focuses on a sustainable method of synthesizing, characterizing, and evaluating the properties of nanomaterials, specifically metal oxide nanoparticles and their nanocomposites to contribute to the water treatment processes. Chapter 2 presents a sustainable and reproducible approach for preparing zinc oxide nanoparticles (ZnO) using sawdust as a sacrificial template. The synthesized ZnO nanoparticles exhibit a porous morphology, which enhances their effectiveness in the photocatalytic degradation of the organic pollutant Methyl Orange (MO). The study reveals that the ZnO nanoparticles demonstrate nearly equal activity in both deionized water (DIW) and simulated fresh drinking water (FDW) under UV-B light irradiation. Chapter 3 reports a facile and fast synthesis method of ZnO through the aerobic combustion of saccharides such as glucose, fructose, starch, and dextrin. This synthesis approach results in the formation of ZnO nanoparticles with high surface area and surface energy, contributing to their enhanced photocatalytic activity in MO degradation under UV-B light and sunlight irradiation. Chapter 4 introduces a modified method for synthesizing ZnO nanoparticles, aiming to improve their photocatalytic performance in degrading MO under both UV light and sunlight. The modified synthesis approach resulted in ZnO nanoparticles that exhibited higher efficiency by increasing the surface area and crystallinity of nanoparticles in degrading MO compared to the ZnO synthesized in the previous chapter. Chapter 5 presents, a novel and facile method for synthesizing a regenerable adsorbent, Zinc Oxide, and Carbon Nanocomposite (ZnO@C) by the combustion method. This composite is designed for the efficient removal of anionic and cationic organic pollutants Methyl Orange (MO), Methylene Blue (MB), Congo Red (CR), and Bisphenol A (BPA) from water through adsorption. The maximum adsorption capacity of the ZnO@C composite was determined to be 345 mg/g for MO, 286 mg/g for MB, 244 mg/g for CR, and 345 mg/g for BPA, respectively. With its high adsorption potential for organic pollutants, these nanocomposites hold great promise for water purification applications