Work

Iron minerals as catalysts in photo-assisted NO3– reduction in aqueous phase

Year: 2025

Type: article

Abstract: Presence of nitrogenous compounds in drinking water cannot exceed 50 mg/L for NO 3 − , 0.1 for NO 2 − , and 0.5 mg/L for NH 4 + . In order to address this issue, this study tackles the use of iron-rich minerals (hematite, ilmenite , goethite and magnetite) as catalysts in photo-assisted nitrate reduction employing oxalate as reducing agent. Firstly, the catalytic activity of the different minerals was tested at different pH levels, finding an outstanding performance of magnetite at pH 0 5, with a 50 % NO 3 − reduction in 60 min. After selecting magnetite as catalyst, a parametric study was performed evaluating initial pollutant concentration, catalyst load and reducing agent dosage. Best operating conditions were found to be [NO 3 − ]: 75 mg/L, [Fe 3 O 4 ]: 100 mg/L, [C 2 O 4 2− ]: 370 mg/L and pH 0 5, for which complete NO 3 − reduction and selectivity towards N 2(g) was reached after 150 min. Furthermore, magnetite maintained its activity in 5 consecutive cycles without any treatment between runs, showing its great stability. Reaction mechanism follows two pathways: i) direct electron transfer and ii) CO 2 • − mediated reduction. This mechanism was validated using methyl viologen as CO 2 • − scavenger showing that both pathways contribute equally in NO 3 − reduction. Finally, process feasibility was tested employing real groundwater samples naturally containing NO 3 − , showing promising results towards the implementation of photo-assisted catalytic reduction for drinking water treatment. Thus, a highly efficient technology has been developed, overcoming the limitations of photo-assisted nitrate removal processes by utilizing a cost-effective, stable, and highly active catalyst. This approach achieves the legislation for drinking water while generating negligible [NH 4 + ].

Source: Catalysis Today

DOI: 10.1016/j.cattod.2025.115307

Authors: Vanesa A. Hahn, Alicia L. Garcia-Costa, Jose A. Casas

Institution: Universidad Autónoma de Madrid

Language: English

Topic: Advanced Photocatalysis Techniques

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

SDGs: Clean water and sanitation, Responsible consumption and production

Open Access status: hybrid

Estimated APC paid: $3,930