Smart Engineered Nanomaterials for Water Cleaning Applications: From Adsorption to Catalysis

Abstract

Water scarcity and pollution pose a significant global challenge, demanding innovative solutions for sustainable water management and reuse. However, the presence of emerging contaminants, such as persistent organic pollutants (POPs), necessitates advanced treatment technologies for safe water reuse. This thesis explores the potential of smart nanomaterials for advanced water treatment technologies, particularly focusing on the removal of POPs. Engineered nanomaterials offer unique advantages to address these challenges due to their exceptional properties. Their high surface area-to-volume ratio compared to bulk materials translates to a significantly greater number of active sites available for interaction with pollutants. This enhanced interaction allows nanomaterials to efficiently adsorb contaminants or act as catalysts for degradation. Additionally, the ability to precisely control the size, shape, and surface chemistry of nanomaterials during synthesis enables them to be tailored for specific target pollutants or treatment processes. Furthermore, the small size of nanomaterials allows for their integration into microrobotic systems or the development of nanocomposites. For instance, porous nanomaterials like covalent organic frameworks (COFs) can be designed with specific pore sizes and functionalities to selectively capture contaminants. Chapter 1 investigates the growth mechanism of COF-300, controlling its size, structure, and consequently its processability. The successful nanoscale synthesis of COF-300 enabled its integration into a microrobotic system through biotemplating techniques. Piezocatalysis, a technique utilizing mechanical stress to activate catalysts, presents another promising avenue for water remediation using piezoelectric nanoparticles like barium titanate (BaTiO3). This research explores the ability of these nanoparticles to degrade POPs through piezocatalysis. The effectiveness of piezocatalysis against various pollutants, including methyl orange, bisphenol A (BPA), bisphenol S (BPS), and per- and polyfluoroalkyl substances (PFAS), is investigated in Chapter 2. Building on these concepts, Chapter 3 proposes a novel core-shell composite nanoparticle for enhanced water treatment. This design integrates a piezoelectric core with a highly porous metal-organic framework (MOF) to create a "concentrate-and-destroy" system for low-concentration pollutant scenarios. Finally, recognizing the importance of reliable data acquisition, Chapter 4 delves into best practices for conducting piezocatalytic experiments. It explores experimental procedures, practical considerations (mechanical energy sources, temperature control), and the influence of sonocatalysis, tribocatalysis, and adsorption on piezocatalytic processes. A case study involving transition metal dichalcogenide (TMDC) nanoflowers (NFs) is presented to illustrate how ultrasound facilitates adsorption during piezocatalysis and how to distinguish these phenomena.