Abstract
Management of ubiquitous nitrate contamination in drinking water sources is a major engineering challenge due to its negative impacts from eutrophication to immediate risk to human health. Several water treatment technologies exist to manage nitrate pollution in water sources. However, the most widely used technologies are phase separation treatments. In this context, nanoscale photocatalysis emerges as a highly promising transformative technology capable of reducing nitrate to innocuous nitrogen with noticeable selectivity. This critical review describes the photocatalytic reduction mechanisms of nitrate towards undesirable products (nitrite, ammonium) and the more desirable product (dinitrogen). The mechanisms are based on the standard reduction potential of each individual species and highlight the contribution of reducing species (e.g. CO2[rad]−) radicals formed from different hole scavengers. The strategic use of different pure, doped, and composite nanoscale photocatalysts is discussed on the basis of reduction mechanisms' overall conversion, kinetic rates, and selectivity towards N2. The choice of light source affects pathways and influences by-product selectivity because direct photolysis of N-intermediates, which has been overlooked in the literature. In addition, the re-oxidation of nitrite and ammonia as drawback process is explained. Finally, an exhaustive analysis presents the photocatalytic reduction applications for treating real water matrices and the competing effect of other species. Overall, this critical review aims to contribute to the understanding of the potential application/constraints of photocatalysis in inorganic nitrogen management, and guide researchers towards future efforts required for widespread implementation.
| Language | English (US) |
|---|---|
| Pages | 1524-1551 |
| Number of pages | 28 |
| Journal | Science of the Total Environment |
| Volume | 599-600 |
| DOIs | |
| State | Published - Dec 1 2017 |
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Keywords
- Nanoparticle
- Nanotechnology
- Nitrogen cycle
- Photocatalysis
- Titanium dioxide (TiO)
- Water treatment
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal
- Pollution
Cite this
Challenges in photocatalytic reduction of nitrate as a water treatment technology. / Tugaoen, Heather O.Neal; GARCIA SEGURA, Sergio; Hristovski, Kiril; Westerhoff, Paul.
In: Science of the Total Environment, Vol. 599-600, 01.12.2017, p. 1524-1551.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Challenges in photocatalytic reduction of nitrate as a water treatment technology
AU - Tugaoen, Heather O.Neal
AU - GARCIA SEGURA, Sergio
AU - Hristovski, Kiril
AU - Westerhoff, Paul
PY - 2017/12/1
Y1 - 2017/12/1
N2 - Management of ubiquitous nitrate contamination in drinking water sources is a major engineering challenge due to its negative impacts from eutrophication to immediate risk to human health. Several water treatment technologies exist to manage nitrate pollution in water sources. However, the most widely used technologies are phase separation treatments. In this context, nanoscale photocatalysis emerges as a highly promising transformative technology capable of reducing nitrate to innocuous nitrogen with noticeable selectivity. This critical review describes the photocatalytic reduction mechanisms of nitrate towards undesirable products (nitrite, ammonium) and the more desirable product (dinitrogen). The mechanisms are based on the standard reduction potential of each individual species and highlight the contribution of reducing species (e.g. CO2[rad]−) radicals formed from different hole scavengers. The strategic use of different pure, doped, and composite nanoscale photocatalysts is discussed on the basis of reduction mechanisms' overall conversion, kinetic rates, and selectivity towards N2. The choice of light source affects pathways and influences by-product selectivity because direct photolysis of N-intermediates, which has been overlooked in the literature. In addition, the re-oxidation of nitrite and ammonia as drawback process is explained. Finally, an exhaustive analysis presents the photocatalytic reduction applications for treating real water matrices and the competing effect of other species. Overall, this critical review aims to contribute to the understanding of the potential application/constraints of photocatalysis in inorganic nitrogen management, and guide researchers towards future efforts required for widespread implementation.
AB - Management of ubiquitous nitrate contamination in drinking water sources is a major engineering challenge due to its negative impacts from eutrophication to immediate risk to human health. Several water treatment technologies exist to manage nitrate pollution in water sources. However, the most widely used technologies are phase separation treatments. In this context, nanoscale photocatalysis emerges as a highly promising transformative technology capable of reducing nitrate to innocuous nitrogen with noticeable selectivity. This critical review describes the photocatalytic reduction mechanisms of nitrate towards undesirable products (nitrite, ammonium) and the more desirable product (dinitrogen). The mechanisms are based on the standard reduction potential of each individual species and highlight the contribution of reducing species (e.g. CO2[rad]−) radicals formed from different hole scavengers. The strategic use of different pure, doped, and composite nanoscale photocatalysts is discussed on the basis of reduction mechanisms' overall conversion, kinetic rates, and selectivity towards N2. The choice of light source affects pathways and influences by-product selectivity because direct photolysis of N-intermediates, which has been overlooked in the literature. In addition, the re-oxidation of nitrite and ammonia as drawback process is explained. Finally, an exhaustive analysis presents the photocatalytic reduction applications for treating real water matrices and the competing effect of other species. Overall, this critical review aims to contribute to the understanding of the potential application/constraints of photocatalysis in inorganic nitrogen management, and guide researchers towards future efforts required for widespread implementation.
KW - Nanoparticle
KW - Nanotechnology
KW - Nitrogen cycle
KW - Photocatalysis
KW - Titanium dioxide (TiO)
KW - Water treatment
UR - http://www.scopus.com/inward/record.url?scp=85019479536&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85019479536&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2017.04.238
DO - 10.1016/j.scitotenv.2017.04.238
M3 - Article
VL - 599-600
SP - 1524
EP - 1551
JO - Science of the Total Environment
T2 - Science of the Total Environment
JF - Science of the Total Environment
SN - 0048-9697
ER -