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Development and Application of a Reductive Titanium Dioxide Catalyst

Abstract

A large population in the United States relies on groundwater as the drinking water source. One typical pollutant of groundwater is nitrate (NO3-). Individuals that have consumed water with high levels of nitrate are at the risk of methemoglobonemia. Due to the prevalence of nitrate contamination in groundwater, various methods have been developed to remove nitrate. These methods include ion exchange, reverse osmosis, and biological denitrification. Photocatalysts have been used for water treatment but are conventionally used for oxidative treatment of pollutants in water. Usage of TiO2 for reductive treatment requires the addition of organic solvent for use as an external hole scavenger. Organic solvent addition to water makes the water undrinkable. The objective of this study was to develop a reductive TiO2 photocatalyst and apply it to treat nitrate-contaminated groundwater. One type of synthesized TiO2 was capped with diethylene glycol (DEG) solvent and also doped with barium (Ba). The second type of TiO2 catalyst was also synthesized with a DEG cap but did not have barium doping.

Doping of barium to the catalyst when DEG was present did not lead to increased nitrate reduction. DEG provided sufficient electrons to block photo-generated holes. There existed an optimum combination of precursor concentration and heating time during hydrolysis.

A catalyst dosage of 50 mg/L was determined to be the optimum dosage. Increasing the level of nitrate had a negative impact upon the performance of the catalyst as a result of increased hydroxyl radical generation and resulting consumption of photo-generated electrons. Other anions found in groundwater including sulfate, phosphate, carbonate, and chloride were shown to not produce a negative effect upon the performance of the catalyst.

Synthesized TiO2 can also be applied to water sources that may be unsuitable for biological treatment due to the fragile nature of bacteria. The relatively little wasted generated from synthesized TiO2 allows synthesized TiO2 to be used for water sources in areas where there are limited options for wasted disposal.

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