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Photo‐Assisted Immobilized Fenton Degradation up to pH 8 of Azo Dye Orange II Mediated by Fe 3+ / Nafion /Glass Fibers
Author(s) -
Dhananjeyan Mugunthu R.,
Kiwi John,
Albers Peter,
Enea Octav
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20011114)84:11<3433::aid-hlca3433>3.0.co;2-a
Subject(s) - nafion , chemistry , x ray photoelectron spectroscopy , catalysis , methyl orange , photodegradation , scanning electron microscope , nuclear chemistry , chemical engineering , inorganic chemistry , materials science , photocatalysis , organic chemistry , composite material , electrochemistry , electrode , engineering
Fe 3+ Ions have been immobilized into very thin Nafion films cast onto a glass‐fiber mat immersed in an alcoholic solution of Nafion oligomers. This immobilized Fenton catalyst was used to abate/mineralize the azo dye Orange II, taken as a model organic compound. The abatement of Orange II on the Fe 3+ / Nafion /glass fibers was observed to proceed within the same time period as when Nafion alone was used to immobilize the Fe 3+ ions during the photo‐ Fenton reaction. The amount of Nafion in the Nafion Fe 3+ /Nafion/glass fibers was ca. 15 times less per unit surface area compared to Fe 3+ ‐exchanged on conventional Nafion membranes used to immobilize Fe 3+ ions. Orange II solutions under visible‐light irradiation in the presence of H 2 O 2 were mineralized up to pH 8 with a kinetics comparable to that found during the degradation runs at pH 3. Repetitive mineralization cycles mediated by the Fe 3+ / Nafion /glass fibers under visible light did not show any decrease in the activity of the immobilized catalysts. A reaction mechanism consistent with the experimental data is suggested. The morphology of the Fe 3+ / Nafion /glass fibers was characterized by scanning electron microscopy (SEM) showing thin Nafion films cast deposited on the glass fibers. Transmission‐electron‐microscopy (TEM) micrographs reveal Fe 3+ ‐oxy‐hydroxide particles of 3 – 6 nm before and after repetitive Orange II photodegradation. X‐Ray photoelectron spectroscopy (XPS) provided the evidence for the existence of Fe clusters on the topmost layer of the catalyst mainly as Fe III . The improvements brought by the glass fibers are a ) the use of low quantities of expensive Nafion supported on glass mats to achieve dye degradation rates comparable to Nafion alone and b ) Fenton ‐mediated degradation of azo dyes at pH 8 without the costly initial acidification usually needed for this type of treatment.