Photoassisted Fenton Degradation of Nonbiodegradable Azo Dye (Orange II) in Fe-Free Solutions Mediated by Cation Transfer Membranes
Year: 1998
Type: article
Abstract: Photoassisted degradation of nonbiodegradable Orange II is shown to be catalyzed by Nafion cation-transfer membranes exchanged with Fe ions in the presence of H 2 O 2 . The Nafion membranes in the oxidative media used degraded Orange II with similar kinetics as found in the homogeneous Fe 3+ /H 2 O 2 photoassisted catalysis, avoiding the drawbacks of the homogeneous treatment. The treatment of this model textile dye is shown to proceed via a Fenton-like process without sludge production because of the selective H 2 O 2 decomposition on the Fe ions exchanged on the membrane. The effect of the concentration of H 2 O 2, solution pH, azo dye concentration, and light intensity (visible light) on the degradation of Orange is reported in detail. The activity of the membranes during the Orange II decomposition was tested for 1500 h and was observed to remain fairly stable within this period. The Fe/Nafion membranes consisted mainly of Fe 2 O 3 (78%) before reaction and Fe 2 O 3 (14%) after light irradiation during Orange II oxidation, as found by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The size of the Fe particles in the Nafion was investigated by transmission electron microscopy (TEM) and turned out to be 37 ± 4 Å. These Q-sized Fe particles on the Nafion absorbed directly the light energy, avoiding the losses due to absorption by the contaminants as it is the case in homogeneous photoassisted Fenton processes. A simplified reaction mechanism for Orange II decomposition is suggested that is consistent with the experimental findings for solutions up to pH 4.8. The Fe redox reactions in the membranes under light were studied via XPS and spectrophotometric techniques. The effect of pretreatment of the azo dye making possible subsequent biological degradation was tested by BOD 5 . A drastic increase of the BOD 5 values for the pretreated solutions was found with respect to the zero BOD 5 value observed for nonpretreated Orange II.
Source: Langmuir
DOI: 10.1021/la980382a
Authors: J. Fernandez, J. Bandara, A. Lopez, Ph. Buffat, J. Kiwi
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1980393681