CEJ 191-2012-112

Photodecolorization of methyl orange over -Fe2O3-supported HY catalysts:
The effects of catalyst preparation and dealumination

An -Fe2O3-supported HY zeolite (-Fe2O3/HY) was prepared by introducing nanosized -Fe2O3 into an
HY zeolite support through in situ (-Fe2O3/HYIS) and ion-exchange (-Fe2O3/HYIE) methods. The effect
of the preparation methods on the physicochemical properties of the catalyst were studied via XRD,
FESEM-EDX, TEM, UV–vis DRS, FTIR, XPS, 29Si and 27Al MAS NMR, ESR and BET surface area analysis.
In this study, dealumination was accomplished by using a facile electrolysis system without any strong
acids, reactive compounds and/or hydrothermal treatment. Dealumination accompanied by ion exchange
of Al with Fe3+ ions in the HY zeolite framework resulted in the formation of an active species that had
a higher photoactivity towards the decolorization of methyl orange (MO). A 5 wt% -Fe2O3/HYIS was
found to produce an 80% photodecolorization of 30 mg L−1 of MO at pH 2 with 0.375 g L−1 catalyst, while
5 wt% -Fe2O3/HYIE only produced 23% photodecolorization under similar conditions (2 h reaction time).
This study showed that the kinetics follow a pseudo-first order Langmuir–Hinshelwood model with an
activation energy (Ea) calculated for both 5 wt% -Fe2O3/HYIS and 5 wt% -Fe2O3/HYIE to be 45.8 kJ mol−1
and 70.2 kJ mol−1, respectively. Measurements of the mineralization of MO by COD, BOD5 and TOC analysis
were 27.0%, 69.6% and 16.9%, respectively, after 2 h of contact time. The Fe dissolution from the catalyst
showed insignificant leaching of Fe (<1%) when subjected to AAS. A reusability study demonstrated that
-Fe2O3/HYIS could be a promising photocatalyst for the degradation of various dyes in wastewater.