磁性Mn0.6Zn0.4Fe2O4@SiO2催化H2O2降解亚甲基蓝效能及机制

为制备易固液分离和稳定性好的高效非均相类Fenton催化剂,利用正硅酸乙酯水解对Mn_0.6Zn_0.4Fe₂O₄磁性纳米颗粒（SF-MNPs）进行功能化修饰,制备得到Mn_0.6Zn_0.4Fe₂O₄@SiO₂（MZF@SiO₂）磁性纳米复合物催化剂,采用透射电镜、 X射线光电子能谱和振动样品磁强计等对MZF@SiO₂进行了表征,以难生物降解偶氮染料亚甲基蓝（MB）为目标污染物,考察了不同初始pH对MZF@SiO₂催化效能的影响,在近中性条件下（pH=6.5）研究了H₂O₂用量、 MZF@SiO₂投加量和温度等对MB去除率的影响,及MZF@SiO₂的稳定性和循环使用性能,推测了催化反应机制.结果表明,无定形SiO₂将SF-M...

Efficiency and Mechanism of Degradation of Methylene Blue with H2O2 Catalyzed by Magnetic Mn0.6Zn0.4Fe2O4@SiO2

To prepare high-efficiency heterogeneous Fenton catalysts with easy solid-liquid separation and good stability, Mn_0.6Zn_0.4Fe₂O₄ magnetic nanoparticles (SF-MNPs) were functionally modified through hydrolysis of tetraethylorthosilicate, and Mn_0.6Zn_0.4Fe₂O₄@SiO₂ (MZF@SiO₂) magnetic nanocomposite (MNC) catalysts were prepared. MZF@SiO₂ was characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and a vibrating sample magnetometer. The effect of different initial pH on the catalytic performance of MZF@SiO₂ was investigated using methylene blue (MB) refractory azo dye as the target pollutant. Under the initial near-neutral pH condition (pH=6.5), the effects of H₂O₂dosage, MZF@SiO₂ dosage, and temperature on the removal efficiency of MB were investigated. The stability and recycling performance of MZF@SiO₂ were studied, and the catalytic reaction mechanism was speculated. The results showed that SF-MNPs were completely encapsulated by amorphous SiO₂, and MZF@SiO₂ had a "core-shell" structure. Magnetic core SF-MNPs had good crystallinity with a spinel structure. The saturation magnetization of MZF@SiO₂ was 18.6 emu·g^-1, and the remanence and coercivity were low. The dispersibility and solid-liquid separation performance of MZF@SiO₂ were excellent in water. Under the condition of neutral pH, the utilization rate of H₂O₂ was 74.50%, and the removal rate of MB reached 94.76%. When the reaction time was 120 min, the temperature was 303 K, and the dosage of MZF@SiO₂ was 1.0 g·L^-1. The first-order reaction rate constant was 0.0466 min^-1, and MZF@SiO₂ had good stability and recycling performance. The solid-liquid interface reaction was the rate control step of the process. The reactive oxygen species in the MZF@SiO₂+H₂O₂ system were·OH radicles. The coating layer SiO₂ could accelerate the electron transfer rate, and there was a positive synergistic effect between SiO₂ and SF-MNPs. The existence of oxygen vacancies in SF-MNPs was also conducive to the electron transfer in the heterogeneous Fenton-like reaction. The as-prepared MZF@SiO₂ MNC catalysts had a superior catalytic activity with good stability, and they had the advantages of easy magnetic separation and reusability. Thus, MZF@SiO₂ MNC catalysts have a wider range of potential applications in actual printing and dyeing wastewater treatment.