Research On The Preparation And Mechanism Of Iron-based Catalysts

Recently,the pollution of water resources by refractory organic compounds has become a serious environmental problem that has attracted much attention.Among the available water remediation technologies,advanced oxidation processes?AOPs?are regarded as effective technologies for the degradation of hazardous organic pollutants in wastewater.However,these approaches still need to be upgraded for more cost-effective and environmental compatibility.Further studies are still required to inspect the reaction mechanisms of many remediation technologies.In this paper,magnetic metal-organic framework was fabricated as a catalyst for heterogeneous degradation in a neutral Fenton-like system.Additionally,in order to get a more energy-efficient degradation system,magnetically nanoscaled Fe₃O₄/Mn₃O₄ composite was fabricated via a simple method and applyed to degrade RhB without the aid of agents.In the presence of Fe₃O₄ particles,Fe₃O₄/MIL-101 was prepared via in situ solvothermal method using H₂BDC and DMF as precursors and employed as heterogeneous Fenton-like catalyst for the oxidation of Rhodamine B?RhB?.The Fe₃O₄/MIL-101 catalysts were characterized by XRD,N₂ adsorption/desorption,FT-IR,XPS,SEM,TEM and HRTEM methods and exhibited enhanced catalytic performance for degradation of RhB in a neutral Fenton-like system.The experimental results indicated that nanoparticles possess a uniform polyhedral morphology.Under optimized conditions,almost 100%removal of 10mg/L RhB was achieved in 30 min using 0.5 g/L Fe₃O₄/MIL-101 and 20 mM H₂O₂ at initial pH7.The reasonable stability of Fe₃O₄/MIL-101 was also confirmed after four successive runs.On the basis of the characterization of the catalyst,the results of metal leaching,the effects of radical scavengers,and hydroxyl radical?·OH?determination,a possible reaction mechanism for H₂O₂ activated by Fe₃O₄/MIL-101 under neutral conditions is proposed.Furthermore,this work aims to study a more energy-efficient material to apply in RhB degradation system.In regard to these problems,magnetically nanoscaled Fe₃O₄/Mn₃O₄composite was fabricated via a simple co-precipitation method using ferric chloride and ferrous chloride as precursors.The composite was characterized by various analytical techniques and employed as heterogeneous catalyst for direct oxidation of RhB.Moreover,the effects of pH value and various gas atmospheres on degradation performance were investigated.The experimental results indicated that the nanoparticles possess similar ellipsoid morphology and Fe₃O₄/Mn₃O₄ exhibited excellent activity for the oxidation of RhB in the absence of oxidizing agents.Under optimized conditions,almost 100%removal of 20 mg/L RhB was achieved in 30 min using 0.5 g/L Fe₃O₄/Mn₃O₄ at initial pH3.Fe₃O₄/Mn₃O₄ showed excellent stability after four successive runs.Finally,based on the analysis of metal leaching,the detection of Mn???and X-ray photoelectron spectroscopy?XPS?,a possible reaction mechanism is proposed.