Concerns linked to highly dispersed iron anchored within graphitic carbon nitride, is it a truly promising material to drive heterogeneous photo-Fenton treatments?
Year: 2025
Type: article
Abstract: The precipitation of iron at pH > 4 is one of the main drawbacks of any Fenton-based process. Among the engineered solutions, the incorporation of iron within the wide cavities of graphitic carbon nitride (g-CN) has recently gained momentum. However, most works employing Fe-g-CN materials usually employ high H 2 O 2 concentrations (>25 mM) to observe considerable pollutant abatements (without or with UV–vis light irradiation, i.e., by heterogeneous dark- or photo-Fenton processes, respectively). To gain further insights into this issue, in this work, Fe-g-CN, with different amounts of iron, were synthesised by thermal polycondensation of melamine and FeCl 3 ·6H 2 O as precursors and compared its performance with the g-CN alone. Under UV-A light, a content of 0.2% w/w of iron in the g-CN was optimal to improve the oxidative performances of target pollutants (phenol and sulfamethoxazole 100 μM, respectively), higher Fe-loadings decreased the photocatalytic performances with respect to g-CN. Interestingly, this trend was inversed when adding H 2 O 2 1 mM, being the pollutant removal by g-CN faster than that by Fe-g-CN (for phenol, k obs = 8.02 × 10 −2 min −1 and 2.83 × 10 −2 min −1 , respectively), opposed to expectations. Furthermore, HO • , HO 2 • or 1 O 2 were barely detected by Electron Paramagnetic Resonance, indicating that the reactive species should oxidise the g-CN rather than react with the spin traps. Finally, although g-CN oxidation was not observed by typical characterisation techniques (such as FT-IR/ATR), we have observed 6 times more nitrates formation by illuminated Fe-g-CN than g-CN, indicating that iron enhances the self-oxidation of illuminated carbon nitrides. Our results demonstrate that iron incorporation in g-CN might be not as convenient as usually stated in the literature, as the stability of the photocatalyst is drastically reduced, releasing nitrates and possibly decreasing the material's lifetime. • The stability of carbon nitride is usually overlooked. • Fe-g-C 3 N 4 /H 2 O 2 releases more nitrates than g-C 3 N 4 /H 2 O 2 . • Fe-g-C 3 N 4 is less stable than g-C 3 N 4 due to the involved reactions. • Formed reactive species oxidise g-C 3 N 4 structure rather than the pollutants.
Source: Chemosphere
Authors: Simone Pellegrino, Iván Sciscenko, Fabrizio Caldera, Claudio Minero, Enzo Laurenti, Marco Minella
Institution: University of Turin
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,010
OpenAlex ID: W4408148257