Nitrate removal using metal-acid light induced (MALI) cycle
The homogeneous Fe3+/oxalate system was examined as a Metal-Acid Light Induced (MALI) cycle for the photo-assisted reduction of nitrate (NO3). A linear correlation between NO3 concentration removal and C2O4 2 consumption, at stoichiometric conditions, was obtained. This confirmed that CO2•- radicals...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Universidad Autónoma de Madrid |
| Repositorio: | Biblos-e Archivo. Repositorio Institucional de la UAM |
| Idioma: | inglés |
| OAI Identifier: | oai:dnet:biblosearchi::fb536cbab62144986445b35de0a3e669 |
| Acceso en línea: | https://hdl.handle.net/10486/756700 https://dx.doi.org/10.1016/j.seppur.2026.137539 |
| Access Level: | acceso abierto |
| Palabra clave: | Nitrate removal Photo-assisted process MALI cycle iron/oxalate cycle Nitrate reduction kinetics and mechanism Química |
| Sumario: | The homogeneous Fe3+/oxalate system was examined as a Metal-Acid Light Induced (MALI) cycle for the photo-assisted reduction of nitrate (NO3). A linear correlation between NO3 concentration removal and C2O4 2 consumption, at stoichiometric conditions, was obtained. This confirmed that CO2•- radicals generated through ferrioxalate photolysis are the primary reductive species, enabling complete NO3 conversion with no detectable accumulation of NH4+ or gaseous NOX and only minor transient NO2 formation. Time-resolved kinetic experiments demonstrated that NO3 undergo pseudo-first order, whereas oxalate decomposition follows zero-order behavior governed exclusively by the photon flux. A study has been conducted on the influence of the different variables affecting the Fe-Oxalate-UV cycle. A photonic operational window was identified in Fe–oxalate systems, delineating the transition from reagent-controlled to photon-limited regimes. Outside this window, excess oxalate activated competing oxidative pathways that re-oxidized nitrogenated byproduct and decreased NO3 removal rate, thereby elucidating inconsistencies previously reported in the literature. Application to a real groundwater matrix revealed that Ca2+ induced CaC2O4 precipitation, markedly lowering UV transmittance and slowing the reaction. Mild acidification effectively suppressed precipitation restored photon utilization and produced NO3 reduction rates comparable to, and initially exceeding, those obtained in ultrapure water. These results close critical mechanistic and operational gaps in homogeneous photo-assisted NO3 reduction. The integrated kinetic, photonic and matrix-dependence framework developed here provides quantitative design guidelines for reagent dosing, light delivery and water-quality conditioning. Collectively, these insights advance the rational scale-up of the MALI cycle as a selective and practical technology for NO3 remediation |
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