Browsing by Author "Arredondo, Jacob"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Niobium Oxide Photocatalytically Oxidizes Ammonia in Water at Ambient Conditions(SciELO, 2024) Elias, Welman; Clark, Chelsea; Heck, Kimberly; Arredondo, Jacob; Wang, Bo; Toro, Andras; Kürtib, László; Wong, Michael; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water TreatmentAmmonia contamination in water is a significant environmental issue since it is toxic and leads to eutrophication. Photocatalysis has been investigated as a strategy for ammonia degradation but can potentially form toxic nitrite (NO2–) and nitrate (NO3–) byproducts. This work reports on the ability of niobium oxide (Nb2O5) to photocatalytically oxidize aqueous-phase ammonia (NH3). Whereas as-synthesized Nb2O5 showed little catalytic activity (< 1% NH3 conversion after 6 h of UV-C irradiation, at room temperature and atmospheric pressure, and under O2 headspace), Nb2O5 treated in basic solution (OH-Nb2O5) was able to photocatalytically degrade NH3 at ca. 9% conversion after six hours, with ca. 70% selectivity to the desired N2, with a first-order rate constant of ca. 12 times higher than the as synthesize catalyst (1.6 × 10–3 min–1 vs. 2.0 × 10–2 min–1). Raman spectroscopic analysis indicated the presence of terminal Nb=O species after base treatment of Nb2O5, implicating them as catalytically active sites. These results underscore how a simple structural modification can significantly affect photocatalytic activity for aqueous ammonia oxidation.Item Titanium oxide improves boron nitride photocatalytic degradation of perfluorooctanoic acid(Elsevier, 2022) Duan, Lijie; Wang, Bo; Heck, Kimberly N.; Clark, Chelsea A.; Wei, Jinshan; Wang, Minghao; Metz, Jordin; Wu, Gang; Tsai, Ah-Lim; Guo, Sujin; Arredondo, Jacob; Mohite, Aditya D.; Senftle, Thomas P.; Westerhoff, Paul; Alvarez, Pedro; Wen, Xianghua; Song, Yonghui; Wong, Michael S.; Center for Nanotechnology Enabled Water TreatmentBoron nitride (BN) has the newly-found property of degrading recalcitrant polyfluoroalkyl substances (PFAS) under ultraviolet C (UV-C, 254 nm) irradiation. It is ineffective at longer wavelengths, though. In this study, we report the simple calcination of BN and UV-A active titanium oxide (TiO2) creates a BN/TiO2 composite that is more photocatalytically active than BN or TiO2 under UV-A for perfluorooctanoic acid (PFOA). Under UV-A, BN/TiO2 degraded PFOA ∼ 15 × faster than TiO2, while BN was inactive. Band diagram analysis and photocurrent response measurements indicated that BN/TiO2 is a type-II heterojunction semiconductor, facilitating charge carrier separation. Additional experiments confirmed the importance of photogenerated holes for degrading PFOA. Outdoor experimentation under natural sunlight found BN/TiO2 to degrade PFOA in deionized water and salt-containing water with a half-life of 1.7 h and 4.5 h, respectively. These identified photocatalytic properties of BN/TiO2 highlight the potential for the light-driven destruction of other PFAS.