Goethite (α‐FeOOH) photocatalytic activity at natural concentrations by the addition of H2O2 at neutral pH and the simultaneous presence of fluoride and bicarbonate

• Published in: Applied Research 2024-04, Vol.3 (2), p.n/a
• Main Authors: Alvear‐Daza, John J., Sanabria, Janeth, Castaño‐Rodriguez, Victor A., Correa‐Betancourt, Alejandra, Binet, Silvia, Sánchez, Francisco H., Muñoz‐Medina, Guillermo A., Gutiérrez‐Zapata, Héctor M., Pizzio, Luis R., Rengifo‐Herrera, Julián A.
• Format: Article
• Language: English
• Subjects: 2,4‐dichlorophenoxyacetic acid; Bicarbonates; Bonding strength; Catalytic activity; Dichlorophenoxyacetic acid; Electron transfer; Fluorides; Goethite; Groundwater; heterogeneous photo‐Fenton reaction; Hydrogen peroxide; Iron; Irradiation; Oxidation; Photocatalysis; Photolysis; pollutant removal; Pollutants; Pollution control; Sunlight; Water analysis; Water sampling
• ISSN: 2702-4288; 2702-4288
• DOI: 10.1002/appl.202300015

The effect of the simultaneous presence of fluoride (0.15–1.2 mg L−1), bicarbonates (83.6–596 mg L−1), and synthesized goethite (0.3 mg L−1) at typical concentrations often found in groundwater samples was evaluated on the degradation of 2,4‐dichlorophenoxyacetic acid (2,4‐D) at pH 6.9 under simulated sunlight irradiation (300 W m−2) and H2O2 concentrations of 10 mg L−1. The 2,4‐D removal was strongly enhanced by the presence of fluoride. F− could modify the surface of iron (hydr)oxide, leading to the formation of surface Fe–F bonds benefiting the formation of free •OH, producing upward band bending, reducing the electron‐hole recombination, and enhancing the electron transfer to H2O2. On the other hand, bicarbonate may react with •OH generating CO3−• species that could participate in pollutant oxidation, while solar light‐induced H2O2 photolysis also played an important role in removing 2,4‐D. These findings suggest that tuning of iron (hydr)oxides by fluoride could take place in real groundwater, generating photocatalysts with a high activity that could participate, by adding H2O2, in the enhancement of sunlight photoinduced natural abiotic processes for pollutant abatement. Goethite and fluoride at concentrations typically found in natural waters may produce goethite fluorination leading to an increase of its photocatalytic activity, while the reaction between photoinduced •OH and bicarbonate could lead to the formation of carbonate radicals that may exhibit an interesting oxidizing power to degrade 2,4‐D as well.