Work

Role of extract purification in iron complexation and photo-Fenton reactivity under mild pH conditions

Year: 2026

Type: article

Abstract: Photo-Fenton processes operated at circumneutral pH require iron-complexing agents able to maintain Fe(III) solubility while sustaining efficient Fe(III)/Fe(II) cycling. In this work, polyphenol-rich extracts obtained from grape-processing residues were evaluated as natural ligands for photo-Fenton degradation of a mixture of six emerging contaminants (30 mg L⁻¹ total) at pH 5–7 using 5 mg L⁻¹ Fe(III). Raw alkaline extracts and membrane-refined fractions (300 and 150 kDa) were comprehensively characterized (TOC, COD, AOS, DLS, TPC, flavonoids and EEM fluorescence) and correlated with iron stability and degradation performance through a Doehlert multivariate design. Membrane fractionation significantly modified extract functionality. The 300 kDa retentate exhibited the highest phenolic and flavonoid densities (0.181 and 0.175 mg mg C⁻¹, respectively) and maintained soluble iron at pH 7 with minimal losses over 60 min. Under optimized conditions (pH 6, 16 mg C L⁻¹, stoichiometric H₂O₂), this fraction achieved 80% pollutant removal in 60 min, approaching the performance of EDTA and NTA when compared at equivalent carbon loads. In contrast, the raw extract was penalized by non-functional organic matter, while the 150 kDa fraction showed reduced chelating efficiency due to lower coordination-site density. The novelty of this work lies in establishing a direct correlation between membrane-driven compositional tuning (AOS and fluorescence signatures), iron stability, and photo-Fenton efficiency, demonstrating that functional group density rather than total organic carbon governs performance. These results highlight the potential of agro-residue-derived polyphenolic extracts as sustainable iron-complexing agents for photo-Fenton processes at mild pH.

Source: Journal of environmental chemical engineering

DOI: 10.1016/j.jece.2026.122270

Authors: J. Arévalo, G. Mattarello, M. Cerdán, A.M. Amat, A. Arques, L. Santos-Juanes

Institutions: Universitat Politècnica de València, University of Alicante

Language: English

Topic: Advanced oxidation water treatment

Subfield: Water Science and Technology

Field: Environmental Science

Domain: Physical Sciences

SDGs: Responsible consumption and production, Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $3,350