Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 2, Pages 1221-1232Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c03725
Keywords
ferrate; UVA-LED; micropollutants; degradation mechanism; kinetic model
Categories
Funding
- National Natural Science Foundation of China [52100013]
- Guangdong Provincial Department of Education Youth Innovation Talents Project (Natural Science) [2020KQNCX092]
- Student Innovation and Entrepreneurship Program of Wuyi University [2020CX12]
- Research Project of High-level Talents of Wuyi University [2019AL024]
- Basic and Theoretical Scientific Research Projects of Jiangmen City [2020JC01017]
- Guangdong Basic and Applied Basic Research Foundation [2019A1515110679]
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This study investigated the use of UVA-LED in combination with Fe(VI) for degrading micropollutants, showing significant enhancement compared to Fe(VI) alone. Factors such as wavelength, light intensity, and pH were found to influence the degradation performance.
This paper investigated ultraviolet A light-emitting diode (UVA-LED) irradiation to activate Fe(VI) for the degradation of micropollutants (e. g., sulfamethoxazole (SMX), enrofloxacin, and trimethoprim). UVA-LED/Fe(VI) could significantly promote the degradation of micropollutants, with rates that were 2.6-7.2-fold faster than for Fe(VI) alone. Comparatively, UVA-LED alone hardly degraded selected micropollutants. The degradation performance was further evaluated in SMX degradation via different wavelengths (365-405 nm), light intensity, and pH. Increased wavelengths led to linearly decreased SMX degradation rates because Fe(VI) has a lower molar absorption coefficient at higher wavelengths. Higher light intensity caused faster SMX degradation, owing to the enhanced level of reactive species by stronger photolysis of Fe(VI). Significantly, SMX degradation was gradually suppressed from pH 7.0 to 9.0 due to the changing speciation of Fe(VI). Scavenging and probing experiments for identifying oxidative species indicated that high-valent iron species (Fe(V)/Fe(IV)) were responsible for the enhanced degradation. A kinetic model involving target compound (TC) degradation by Fe(VI), Fe(V), and Fe(IV) was employed to fit the TC degradation kinetics by UVA-LED/Fe(VI). The fitted results revealed that Fe(IV) and Fe(V) primarily contributed to TC degradation in this system. In addition, transformation products of SMX degradation by Fe(VI) and UVA-LED/Fe(VI) were identified and the possible pathways included hydroxylation, self-coupling, bond cleavage, and oxidation reactions. Removal of SMX in real water also showed remarkable promotion by UVA-LED/Fe(VI). Overall, these findings could shed light on the understanding and application of UVA-LED/Fe(VI) for eliminating micropollutants in water treatments.
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