Chen, Ching-Lung2019-04-302019-04-302018http://udspace.udel.edu/handle/19716/24128Perchlorate and fluoride are the common impurities in groundwater in the United States. In recent years, the human activities have significantly increased the concentration of contaminants in ground water and other water bodies. These contaminations affect not only aquatic ecosystems but also human health. The ion exchange and reverse osmosis are inefficient for perchlorate and fluoride treatment, and these methods are strongly affected by source water quality. Neither can these methods solve the perchlorate and fluoride containing wastewater problem. Therefore, the demand for an efficient and sustainable technology to purify and renovate contaminated water is important. The first part of this dissertation focuses on the electrochemical reduction of perchlorate using bimetallic electrodes to convert perchlorate into harmless chloride ions under ambient condition. The second part of this dissertation proposes a novel design of composite porous adsorbents to enhance fluoride removal capacity. ☐ First, we investigate that the incorporation of second catalyst into the electrodes can influence the surface morphology as well as reaction mechanism, leading to the enhanced perchlorate conversion under ambient condition. The performance of bimetallic electrodes on perchlorate reduction was further studied by varying electrode preparation procedures including electrodeposition steps, bimetal ordering, deposition time, bimetal ratio, and bimetal composition. Rh0.8Cu0.2/SS (45% reduction) was found to be more effective than Rh0.8-Mo0.2/SS (38% reduction) and Rh0.8Cr0.2/SS (32% reduction). The optimal electrode (Rh0.25Cu0.75/SS) in this work could achieve nearly 94% perchlorate removal. The mass balance of chloride in the system reached up to 97%. The imbalance part of chloride species could be the adsorption of perchlorate by the electrode. The results of the catalytic electrochemical technique show its suitability for reduction of perchlorate. The scanning electron microscopy (SEM) images of electrodes showed the changes of bimetal deposition process enhanced surface roughness of electrode. The X-ray photoelectron spectroscopy (XPS) analysis of the bimetallic catalysts suggested the existence of metal oxide and elemental metals on electrode surface. ☐ Next, the quaternary ammonium salts (Quats) were used to modify surface of activated carbon and zirconium, respectively. Activated carbons were functionalized with single chain cationic surfactants. A series of Quats of various chain lengths were used: hecyltrimethyl ammonium bromide (HTMA), octyltrimethyl ammonium bromide (OTMA), dodecyltrimethyl ammonium bromide (DDTMA), and hexadecyltrimethyl ammonium bromide (HDTMA). The Quats loading on activated carbon surface resulted in significant increase in fluoride removal. Activated carbons functionalized with longer chain length Quats showed higher perchlorate removal than short ones. Functionalized activated carbons also exhibited a much greater positive surface charge, and the increase in the surface charge is linearly proportional to the amount of Quats loading. The increase in the surface charge was greater for longer chain length Quats. Approximately three-fold increase in the fluoride removal was achieved on activated carbon functionalized with DDTMA compared to plain one. Fluoride adsorption on functionalized activated carbons was less pH dependent than the plain activated carbon. In addition, a series of Quats with various chain lengths were applied as a template to generate unique mesoporous zirconia for fluoride removal. The zirconia synthesized with longer chain length Quats showed high surface area and enhanced fluoride removal. The optimal mesoporous zirconia exhibited ten-fold higher fluoride removal than similar adsorbents reported in the literatures. ☐ Overall, the works presented in this dissertation provide the opportunity to design porous architecture and high-efficient materials for water treatment applications.Thesis1099523390https://doi.org/10.58088/vczf-0a342019-02-14en