On the relevant role of iron complexation for the performance of photo-Fenton process at mild pH: Role of ring substitution in phenolic ligand and interaction with halides
I. Vallés, Iván Sciscenko, M. Mora, Pau Micó Tormos, Ana M. Amat, Lucas Santos‐Juanes, Javier Moreno‐Andrés, Antonio Arques
Abstract
In this work, a systematic study on the effect of Fe(III) complexation by phenolic derivatives with different substitution on photo-Fenton has been carried out. Solutions containing a mixture of six pollutants (30 mg·L−1) were treated by solar simulated photo-Fenton ([Fe(II)] = 0.09 mmol·L−1, [H2O2] = 4.29 mmol·L−1, pH = 5, [Ligand] = 0.227 mmol·L−1. The efficiency of ligand increased with the presence of -OH groups (mainly in ortho- position), while the reverse was true for -COOH and -OCH3. This was correlated with the ability of the ligands to reduce Fe(III) to Fe(II). Catechol (CAT) supressed the interference of chlorides at [NaCl] = 30 mg/L−1 by complexing iron(III) thus preventing formation of FeCl2+, as 85% of Fe(III) was found as Fe(CAT)3 according to mathematical calculations. Hence, effluent matrix, including anions and organic pollutants, has a remarkable effect on iron speciation and a it should be considered when determining reaction conditions.