Factors affecting the efficiency of homogeneous photo–Fenton processes in the presence of different Fe(III)-chelating ligands

BRUNO CARAM; FERNANDO GARCÍA EINSCHLAG*

Understanding Photo-Fenton Processes

NOVA

Año: 2024;

Nota: Aún no dispongo del ISBN, cargué el número de un libro anterior "978-3-662-46795-4" solamente para que el sistema me permita precargar los datos del capítulo que ya fue aceptado para su publicación el 4 de septiembre de 2023Photo-Fenton processes are of special interest due to their potential application for treating wastewater contaminated with refractory organic pollutants. An important drawback concerning the classical photo-Fenton mechanism is the catalyst precipitation above pH 3.5. One of the most widely used strategies to prevent precipitation and keep the catalytic activity at circumneutral pH is the addition of Fe(III)-chelating agents. However, the mechanisms involved are very complex, and different interrelated parameters may affect the overall process efficiency. For instance, ferric complexes of aliphatic polycarboxylates usually show higher photoactivity than aqueous Fe(III) species, while the opposite behavior is observed for ferric complexes bearing aromatic ligands such as phenolate or benzoate. On the other hand, the iron catalytic cycle can be significantly affected by the generation and accumulation of in situ-formed intermediates capable of reducing Fe(III). Consequently, aromatic ligands that yield hydroquinone-like or catechol-like structures are prone to enhance iron circulation through dark pathways.In this chapter, the degradation efficiency of the model pollutant amido black in photo-Fenton systems, modified by the presence of either aromatic (i.e., benzoic acid derivatives) or aliphatic (i.e., citrate and oxalate) carboxylates, is investigated. The contributions of several factors, including the internal filter effects, the modification of the catalyst activity due to complexation, and the in situ formation of intermediate organic species that can promote iron circulation, are comparatively analyzed. Finally, the technological potential of both ligand types for enhancing photo-Fenton systems at circumneutral pH values is discussed.