Immobilized Fe(III)-HY: an efficient and stable photo-Fenton catalyst

Abstract

This article presents preparation, characterization and evaluation of an efficient heterogeneous Fe(III)-HY catalyst for photo-assisted Fenton reaction. Fe(III) ions are immobilized on HY zeolite using different loadings by impregnation, calcination and the activity of the catalyst is evaluated by the degradation of phenol. To initiate a photo-Fenton reaction, suspended Fe(III)-HY in solution is irradiated using UV light to form Fe(II)-HY necessary for the reaction to go. The effect of Fe loadings, H2O2 concentration, pH and quenching on photo-Fenton reaction are studied. The results obtained clearly show that 0.25wt.% Fe(III)-HY is efficient in the degradation of phenol at pH=6. Further the efficiency of Fe(III)-HY is compared with that of a homogeneous photo-Fenton reaction and the increased rate of reaction on Fe(III)-HY highlights the synergistic role of zeolite. Heterogeneous Fe(III)-HY in photo-Fenton reaction allows a wide range of pH for reaction against the narrow pH range in homogeneous system. The system is further subjected to evaluate its stability in solid state. Firstly the reaction solution containing Fe(III)-HY catalyst on irradiation is analyzed for Fe ions with atomic absorption spectroscopy (AAS) and also by calorimetry using 1,10-phenanthroline (o-phen) to find out any Fe leaching from the catalyst and the results show insignificant leaching of Fe (<0.3ppm) at maximum loading of Fe under experimental conditions. Secondly, the irradiated Fe(III)-HY is complexed with o-phen and it is subjected to Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and electron spectroscopy for chemical analysis (ESCA) studies to detect and confirm the oxidation state of Fe in solid state. Critical analysis of these studies clearly show that Fe(III)-HY on irradiation changed to Fe(II)-HY and it is intact with the surface during the course of the reaction. The DRS spectra further evidences complexation of Fe(II) with o-phen. The stability of the catalyst is established by recycling studies.