Full metadata
Title
Environmentally responsible use of nanomaterials for the photocatalytic reduction of nitrate in water
Description
Nitrate is the most prevalent water pollutant limiting the use of groundwater as a potable water source. The overarching goal of this dissertation was to leverage advances in nanotechnology to improve nitrate photocatalysis and transition treatment to the full-scale. The research objectives were to (1) examine commercial and synthesized photocatalysts, (2) determine the effect of water quality parameters (e.g., pH), (3) conduct responsible engineering by ensuring detection methods were in place for novel materials, and (4) develop a conceptual framework for designing nitrate-specific photocatalysts. The key issues for implementing photocatalysis for nitrate drinking water treatment were efficient nitrate removal at neutral pH and by-product selectivity toward nitrogen gases, rather than by-products that pose a human health concern (e.g., nitrite). Photocatalytic nitrate reduction was found to follow a series of proton-coupled electron transfers. The nitrate reduction rate was limited by the electron-hole recombination rate, and the addition of an electron donor (e.g., formate) was necessary to reduce the recombination rate and achieve efficient nitrate removal. Nano-sized photocatalysts with high surface areas mitigated the negative effects of competing aqueous anions. The key water quality parameter impacting by-product selectivity was pH. For pH < 4, the by-product selectivity was mostly N-gas with some NH4+, but this shifted to NO2- above pH = 4, which suggests the need for proton localization to move beyond NO2-. Co-catalysts that form a Schottky barrier, allowing for localization of electrons, were best for nitrate reduction. Silver was optimal in heterogeneous systems because of its ability to improve nitrate reduction activity and N-gas by-product selectivity, and graphene was optimal in two-electrode systems because of its ability to shuttle electrons to the working electrode. "Environmentally responsible use of nanomaterials" is to ensure that detection methods are in place for the nanomaterials tested. While methods exist for the metals and metal oxides examined, there are currently none for carbon nanotubes (CNTs) and graphene. Acknowledging that risk assessment encompasses dose-response and exposure, new analytical methods were developed for extracting and detecting CNTs and graphene in complex organic environmental (e.g., urban air) and biological matrices (e.g. rat lungs).
Date Created
2013
Contributors
- Doudrick, Kyle (Author)
- Westerhoff, Paul (Thesis advisor)
- Halden, Rolf (Committee member)
- Hristovski, Kiril (Committee member)
- Arizona State University (Publisher)
Topical Subject
- Environmental engineering
- Materials Science
- Carbon nanotubes
- nanotechnology
- Nitrates
- Photocatalysis
- Titanium Dioxide
- Water--Purification--Nitrogen removal--Environmental aspects.
- Water
- Water--Purification--Photocatalysis--Environmental aspects.
- Water
- Carbon nanotubes--Environmental aspects.
- Carbon nanotubes
Resource Type
Extent
xxiii, 266 p. : ill. (some col.)
Language
eng
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.I.18086
Statement of Responsibility
by Kyle Doudrick
Description Source
Viewed on Oct. 4, 2013
Level of coding
full
Note
thesis
Partial requirement for: Ph. D., Arizona State University, 2013
bibliography
Includes bibliographical references (p. 223-266)
Field of study: Civil and environmental engineering
System Created
- 2013-07-12 06:29:12
System Modified
- 2021-08-30 01:39:25
- 3 years 2 months ago
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