Preparation And Fenton-like Reaction Mechanism Of Fe₃O₄/HNTs Composites

Heterogeneous Fenton-like technology overcome many shortcomings of traditional Fenton reaction effectively,and has good practical application potential.In this study,a vacuum impregnation method was used to in-situ construct Fe₃O₄nanoparticles on the internal wall of natural halloysite nanotubes?HNTs?,and a new type of heterogeneous Fenton-like catalytic material was obtained.The phase,morphology and magnetic properties of Fe₃O₄/HNTs composites were analyzed by means of X-ray diffraction?XRD?,Fourier infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,pore structure and pore size analysis,specific surface area?BET?,vibration sample magnetometer?VSM?.Using methyl orange?MO?as the target pollutant,the effect of the synthesis conditions of Fe₃O₄/HNTs composite and reaction conditions on Fenton-like reaction efficiency were studied.The kinetic study analyzed the influence of different experimental conditions on the reaction rate constant k.Combined with ultraviolet absorption spectroscopy?UV-vis?,the internal relations among the degradation efficiency of MO,the dissolution of iron ions,the decomposition efficiency of H₂O₂ and·OH production in different reaction processes were systematically studied,and the heterogeneous Fenton-like reaction mechanism of Fe₃O₄/HNTs was proposed.The characterization results showed that the pretreatment did not destroy the natural crystal structure of HNTs.While maintaining the natural nano-tubular structure of HNTs,Fe₃O₄ nanoparticles were uniformly loaded in lumen,and Fe₃O₄had uniform particle sizes and good crystallizations.Fe₃O₄/HNTs have good magnetic properties and can be recycled and reused by using the external magnetic field.The results show that Fe₃O₄/HNTs composite have optimum catalytic oxidation activities when HNTs content is 80%,synthesis temperature is 95°C and synthesis time is 3 hours.When the initial p H=2.0,MO concentration is10 mg/L,H₂O₂ concentration is 29.38 m M and catalyst dosage is 0.5 g/L,the decolorization rate of MO is 99.8%.The results of single-factor experiments showed that with the increase of H₂O₂ concentration,initial p H and catalyst dosage,the decolorization rate of MO increased first and then decreased.As the initial MO concentration increases,the decolorization rate gradually decreases.Fe₃O₄/HNTs heterogeneous Fenton-like reaction system can significantly improve the degradation rate of MO.The reaction mechanism of Fe₃O₄/HNTs heterogeneous Fenton-like system mainly includes two aspects:one is the adsorption of HNTs,the other is the Fenton oxidation initiated by Fe₃O₄ nanoparticles.The cooperation of the two can further improve the efficiency of MO degradation.The study of the reaction mechanism shows that the decolorization of MO is the result of the combined action of Fe₃O₄/HNTs composites and H₂O₂.Under acidic conditions,it is more beneficial for Fe ions to dissolve from the catalysts.Too low or high concentration of H₂O₂is not conducive to the output of·OH.When the concentration of H₂O₂ is29.38 m M,the maximum amount of·OH catalyzed by H₂O₂ is formed,and the decolorization effect of MO is the best.