Preparation Of Opal Based Material As Heterogeneous Fenton Catalysts And Degradation Characteristics Of Rhodamine B Dye Wastewater

Opal was used as a basic material,and it was activated by roasting and acid leaching.Then,the activated-opal was used as a supporter and three heterogeneous photo-Fenton catalysts were successfully prepared using co-precipitation method,in which Fe₂O₃,Fe₂O₃/MnO₂ and Fe₂O₃/Ag particles were loaded onto the surface of opal.The catalysts were used to degrade Rhodamine B?RhB?by UV light.The structural characteristics of catalysts were analyzed by N₂ adsorption,X-ray powder diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,energy dispersive spectrometry?EDS?and Fourier Translation Infrared spectroscopy?FT-IR?.The influencing factors of degradation effect were analyzed,such as pH,H₂O₂ dosage,initial dye concentration,catalyst dosage and reaction temperature.Then,the first-order kinetic equation was fitted to the reaction process.Furthermore,the cyclic stability and reaction mechanism were investigated.Opal was calcined in a muffle furnace at 500?for 2 hours,and then the calcined-opal and HCl?10 wt%?were mixed together under agitation at 100?for 2hours.Then,the aqueous suspension was washed,filtered and dried.Finally,the activated-opal was obtained.The BET specific surface area and total pore volume increased apparently after purification.The specific surface area of opal increased from86.110 m²/g to 99.518 m²/g,and the total pore volume increased from 0.2645 cm³/g to0.2927 cm³/g.At the same time,the mesopore ratio increased from 97.35%to 98.63%.The increased specific surface area and mesopores provide favorable conditions for loading and degradation.Opal-Fe₂O₃ heterogeneous photo-Fenton catalyst was successfully prepared using co-precipitation method,in which the Fe₂O₃ particles were loaded onto the surface of opal.The decolorization rate of RhB was 96.61%under agitation after treatment for 50minutes when the pH was 3.0,dosage of H₂O₂ was 9.0 mmol/L,initial concentration of RhB was 60.0 mg/L,dosage of catalyst was 0.15 g/L and reaction temperature was 25?.The first-order kinetic equation was fitted to the reaction process,the fitted equation was y=0.065x+0.009,the rate constant was 0.065 min^-1 and R²>0.99 under the optimal conditions.The decolorization rate of RhB was still higher than 90%after 4consecutive cycles of catalyst usage,which proved that the catalyst has a great reusability.The hydroxyl radical masking experiment was carried out with tert-butanol as a free radical masking agent,and existence and effect of·OH in the reaction system was verified.According to the change of absorbance peak position of RhB in degradation process,the possible reactions in different reaction stages were deduced and the reaction mechanism was analyzed.Opal-Fe₂O₃/MnO₂ heterogeneous photo-Fenton catalyst was successfully prepared by adding MnO₂ on the basis of the opal-Fe₂O₃.The decolorization rate of RhB was 99.14%under agitation after treatment for 50 minutes when pH was 3.0,dosage of H₂O₂ was9.0 mmol/L,initial concentration of RhB was 100.0 mg/L,dosage of catalyst was 0.10g/L and reaction temperature was 25?.The first-order kinetic equation was fitted to the reaction process,the fitted equation was y=0.093x-0.21,the rate constant was 0.093min^-1 and R²>0.97 under the optimal conditions.The decolorization rate of RhB was still higher than 90%after 5 consecutive cycles of catalyst usage,which proved that the catalyst has a great reusability.Opal-Fe₂O₃/Ag heterogeneous photo-Fenton catalyst was successfully prepared by adding Ag on the basis of the opal-Fe₂O₃.The decolorization rate of RhB was 98.44%under agitation after treatment for 50 minutes when pH was 4.0,dosage of H₂O₂ was9.0 mmol/L,initial concentration of RhB was 120.0 mg/L,dosage of catalyst was 0.10g/L and reaction temperature was 25?.The first-order kinetic equation was fitted to the reaction process,the fitted equation was y=0.093x-0.212,the rate constant was0.093 min^-1 and R²>0.97 under the optimal conditions.The decolorization rate of RhB was still higher than 87%when the catalyst was used 4 times,which proved that the catalyst has a great reusability.