Synthesis of Photocatalytic Nanocomposite Biomaterials for Enhanced Water Filtration Application

Abstract

Clean and drinkable water is a critical necessity for all human and economic development; unfortunately, millions of people do not have access to potable water, resulting in the death of over 2 million children every year. Over the past decade, emphasis has been placed on the synthesis and design of photocatalytic nanocomposites to enhance the chemical degradation of organic pollutants as a cost effective vehicle for clean water production. Amongst the many semiconducting nanoparticles explored in literature, TiO2has stood out for its favorable physiochemical properties, low toxicity, easy availability, high stability, and low cost. When TiO2is irradiated by ultraviolet light, there is creation an electron-hole pair which provides sites for effective reduction or oxidization of the pollutant, converting the pollutant to carbon dioxide, water, and mineral acids. One major shortcoming of TiO2 is related to the efficiency of these systems to harness the entire solar spectrum; therefore, a main focus of this work is the modification of the TiO2 nanoparticles to increase the photon capture efficiency in the visible light region. Of the various possible functionalization pathways, this work focuses on dye sensitization, noble metal deposition, and silane functionalization as well as understanding the synergy between all three. When looking at the rate of remediation of a organic dye pollutant in a simulated sunlight environment, the functionalized particles completely remediated an organic dye pollutant. These functionalized nanoparticles were then deposited into a cellulose matrix of highly absorbent beads in order to prepare a nanocomposite. Results show there is a decrease in the chemical degradation of the pollutant when in the nanocomposite, but a significant increase in a physio-absorption capacity, thus maintaining the rate of total remediation. In addition, the binding interaction between the dye and the particle is a major component in chemical degradation; an aminosilane can be covalently added to the surface of the nanoparticle, and increase the ability of various dyes to adhere to the surface of the TiO2. The incorporation of Ag-functionalized nanocomposites resulted in a synergistic antimicrobial effect, which eliminated both E. coli and S. aureus from the water sample, in addition to increasing the photochemical degradation rate. The specific aim of this work was to create functionalized TiO2 particles with silane groups, organic dyes, and Ag, for the incorporation into a photocatalytic biomimetic nanocomposite membrane which utilizes sunlight to degrade pollutants and inhibit the growth of deadly bacteria.