Preparation of a novel and highly stable Al-Fe loaded sepiolite catalyst for the CWPO of methyl orange: Optimization of physicochemical parameters, kinetics and thermodynamics studies

Abstract

Al-Fe loaded sepiolite catalysts with different active metal ratio have been synthesized using a Turkish sepiolite sample from Eskişehir region. Liquid phase catalytic oxidation of methyl orange azo dye has been carried out over Al-Fe/sepiolite catalysts using hydrogen peroxide as oxidant. The catalytic studies are performed in a glass reactor under atmospheric pressure by semi-batch operation. The effects of several parameters such as catalyst amount, metal loading, calcination temperature, pH, H2O2 concentration, reaction temperature and time on the methyl orange elimination have been examined. The elimination rate of 90.68% was achieved when studied with the catalyst with 8% active metal ratio (SepAlFe8) at pH 3.7 and 25°C. Kinetics studies show the degradation of methyl orange over the SepAlFe8 catalyst could be expressed by the pseudo-first-order reaction kinetics (k1 = 0.0049 min-1 at 25°C). The activation energy (Ea) of the reaction over this catalyst is foundas 29.48 kJ mol-1. It was also found that the catalytic oxidation process is endothermic (ΔH = 26.99 kJ mol-1) and nonspontaneous (ΔG = 96.72 kJ mol-1 at 25°C). The catalyst is chemically stable and reusable with low release of iron.