Continuous-flow titration of low iron doses to promote photo-Fenton and photo-Fenton-like processes at neutral pH
[Display omitted] •Continuous titration of low [Fe2+] with no additional chemicals for PF at mild pH.•S2O82− a promising alternative oxidant to H2O2 for PF-like treatment at neutral pH.•Higher residual [Fe2+] and [TDI] and lower PO43− precipitation when using S2O82−.•Short-chain perfluorinated compo...
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Published in | Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 476; p. 146655 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
15.11.2023
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Subjects | |
Online Access | Get full text |
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Summary: | [Display omitted]
•Continuous titration of low [Fe2+] with no additional chemicals for PF at mild pH.•S2O82− a promising alternative oxidant to H2O2 for PF-like treatment at neutral pH.•Higher residual [Fe2+] and [TDI] and lower PO43− precipitation when using S2O82−.•Short-chain perfluorinated compounds HFBA, PFBS, and TFMS were not oxidized.
Photo-Fenton (PF) is a promising process for degrading a wide range of contaminants of emerging concern (CECs) present in urban wastewater (UWW) after secondary treatment, mitigating their spread in aquatic systems. However, the near-neutral pH of UWW poses a challenge to PF performance. In this research, a tubular membrane photoreactor, designed for continuous “titration” of Fe2+, is explored to promote the PF process for the tertiary treatment of UWW. The application of persulfate (PF-like) as an alternative oxidant and the impact of phosphate (PO43−) content in UWW were also assessed. Process efficiency was evaluated in continuous mode, applying low residence times (RT: 6.1, 36.6, and 73.2 s) and low Fe2+ doses (1, 2, and 5 mg L−1), for the oxidation of 19 CECs (each spiked at 10 µg/L), in demineralized water (DW) and secondary-treated UWW. Despite the persistence of certain short-chain perfluoroalkyl substances (PFAS) and saccharine across all conditions tested, the PF-like process exhibited superior performance when compared with PF, attaining higher removals for most target CECs, especially for melamine. In UWW, for an RT = 73.2 s, [Fe2+] = 5 mg L−1, and [oxidant] = 1.2 mM, PF process removed 7 CECs > 60 % and PF-like 10 CECs > 60 %. Moreover, higher residual concentrations of Fe2+ and lower precipitation of PO43− were observed for PF-like treatments, evidencing its advantages for tertiary treatment. These results emphasize the importance of photoreactor design to achieve efficient PF/PF-like at neutral pH, avoiding the use of chelating agents while managing iron concentrations compatible with UWW discharge or reuse limits. |
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ISSN: | 1385-8947 1873-3212 |
DOI: | 10.1016/j.cej.2023.146655 |