Plasmon-Enhanced Catalytic Ozonation for Water Treatment and Reuse

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1606117WuThe stress of rapid population growth, shortage of fresh water sources, a changing climate, and impaired water sources due to industrialization and urbanization presents a major challenge to water treatment technologies. To better insure high quality drinking water, new, innovative, and cost effective processes are needed. This project is potentially a transformative step to enhance catalytic ozonation for the destruction of emerging contaminants of concern. Advanced oxidation processes usually involve generation of hydroxyl radicals and can be used to remove recalcitrant organic contaminants in water and wastewater. However, the current advanced oxidation processes are usually energy intensive and may form undesired byproducts. This project will examine an enhanced advanced oxidation process as an alternative solution. This project seeks to investigate an innovative advanced water treatment process involving plasmon-enhanced catalytic ozonation to circumvent the limitations of current advanced oxidation processes which fall short of high energy efficiency and low by-product formation. When the frequency of photons (i.e. wavelength of the irradiating light) matches the natural frequency of surface electrons, localized surface plasmon resonance occurs, resulting in strong oscillations of the surface electrons against the positive nuclei background. Plasmonic metals (e.g. Ag, Au, and Cu) support surface plasmon polariton where electromagnetic waves couple to the collective oscillations of valance electrons. It improves solar energy conversion efficiency by enhancing the light absorption in the semiconductor (e.g. TiO2) and directly transferring the plasmonic energy from the metal to the metal oxide support to induce the charge separation. The proposed multidisciplinary research represents one of the first attempts to systematically investigate and utilize the plasmonic effect in advanced water/wastewater treatment. The underlying hypothesis is that the catalytic ozonation of recalcitrant organic compounds can be achieved at a much higher efficiency with minimum by-products formation by using plasmonic effects of copper-based catalysts (earth abundant metal) on metal oxide supports. Irradiating plasmonic nanoparticles with targeted geometric and plasmonic properties with light at their plasmon frequency will facilitate the generation of radical species via ozone decomposition and lead to more complete oxidation of organic contaminants (low organic byproducts formation). The results of the proposed work will provide insights into the novel treatment technology, data for process performance, guidelines for catalyst design and synthesis, and information of fate and transformation of representative emerging contaminants through advanced treatment processes. With LEDs (light emitting diodes) as the light source, this innovative process can be easily implemented in water treatment especially where ozone is used for disinfection. It can also be used in advanced treatment of wastewater for direct/indirect potable reuse. The overarching hypothesis is, that the catalytic ozonation of recalcitrant organic compounds can be achieved at a much higher efficiency with minimum byproducts formation by using plasmonic effects of copper-based catalysts (earth abundant metal) on metal oxide supports. To test this hypothesis the PIs will: (1) Design and synthesize Cu-based catalysts with targeted geometric structure and plasmonic properties using colloidal chemical synthesis as well as atomic layer deposition; (2) Test the catalysts in laboratory plasmon-enhanced catalytic ozonation process focusing on the degree of mineralization, inhibition of bromate formation, and catalyst reusability and stability; (3) Identify the active sites of the catalysts investigate the reaction mechanisms; and, (4) Apply plasmon-enhanced catalytic ozonation in various water matrices including surface water, secondary effluent and reverse osmosis (RO) concentrate produced during water reuse. The PIs have also developed a detailed and comprehensive educational plan that involves graduate and undergraduate students, and high school students working in their laboratories.