Degradation of methyl orange using iron nanoparticles with/without support at different conditions

Abstract

Abstract The degradation of methyl orange (MO) dye, in the presence of pure iron nanoparticles (Fe-NPs) and supporting them in natural zeolite-type clinoptilolite (Fe-Z), were studied. The degradation tests consisted of analyzing the dependence of pH, initial concentration of MO, contact time between systems Fe-NPs ↔ MO and Fe-Z ↔ MO, and temperature, respectively. The highest degradation percentages of MO ranging from 80 to 100% occurred at pH values between 3 and 10; below 3 and above 10, relatively low degradation percentages were measured. Whereas nearly 100% of MO degradation was obtained with pure Fe-NPs for all studied MO concentrations and from 30 °C to 50 °C, for the composite Fe-Z, the degradation of MO was both MO concentration and temperature dependent with the highest degradation percentages at 50 °C. Besides, while using pure Fe-NPs the degradation of 100% of MO was reached at a contact time of 6 h at temperatures between 20 °C and 50 °C. However, when using the composite Fe-Z, the degradation percentages of MO were from 80% to 90% which was reached in 17 h, for temperatures between 15 °C and 50 °C. The resulting kinetic degradation data of MO from pure and supported Fe-NPs was analyzed by considering several empirical models, from which the temperature dependent rate constants were obtained, with best values of ~0.2 h−1at 15 °C and ~1.86 h−1at 50 °C and establishing endothermic-degradation processes. By using these rate constants and the Arrhenius relation, an activation energy (Ea) for the degradation process was determined, being for the Fe-NPs ↔ MO system slightly higher than for the Fe-Z↔ MO system.