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氯代烃(volatile chlorinated hydrocarbons,VCHs)已广泛应用于工业生产[1],在化工生产的过程中,氯代烃的意外泄漏以及对氯化烃的不合理存储处置和排放都会导致严重的地下水污染[2]。三氯乙烯(TCE)是地下水中最常检测到的氯化烃之一,作为一种强效致癌物质,它能够持续存在于自然降解过程中[3]。TCE具有三致效应,即致畸、致癌、致突变。人体长期暴露于TCE等氯代有机污染物中,将会对自身的健康安全造成很大的影响[4]。
目前,从水中去除TCE的方法主要包括物理吸附、生物降解和化学还原氧化[5]等方法。近年来,纳米零价铁技术对氯代烃的降解应用引起了国内外研究者广泛的关注。其中,硫化纳米零价铁(Fe/FeS)具有较大的比表面积、较强的导电能力和便捷的磁分离特性,因此,受到了更广泛的关注[6]。已有研究[7-9]表明,硫化纳米零价铁在对氯代烃的降解上取得了优于纳米零价铁的效果。但是,硫化纳米零价铁只是提高了纳米零价铁的电子选择性,使电子更多的传向污染物。然而,它并没有改善纳米零价铁的团聚问题[10]。硫化纳米零价铁在处理污染物的过程中依然会发生团聚,从而影响其去除污染物的效果[11-12]。
核壳材料通常能够改善其物理和化学性质(如抗氧化性、改进的稳定性、高分散性)[13]。自介孔氧化硅材料合成以来,由于其高比表面积、可调节的孔径和在催化、吸附和生物学方面的应用潜力,已受到越来越多的关注[14-15]。其中,具有蛋黄-蛋壳结构的材料是一种特殊的核壳材料,区别于普通的核壳材料,其核与壳之间有一个大小可调的空隙,这就使得核可与污染物充分接触反应[16]。因此,基于蛋黄-蛋壳结构材料的特殊性能,本研究以正硅酸乙酯(TEOS)为硅源合成介孔氧化硅中空壳,再通过化学反应在壳内形成大尺寸核的方法,合成介孔氧化硅包裹的硫化纳米零价铁材料(Fe/FeS@SiO2),解决硫化纳米零价铁的团聚问题,并提高其去除污染物的能力;利用SEM、XRD、TEM等分析手段进行了表征;然后利用硫化纳米零价铁的还原性质,将制备好的材料用于水体中TCE的去除并考察了其对TCE的去除效果。
基于蛋黄-蛋壳结构的Fe/FeS@SiO2材料去除水中三氯乙烯
Removal of trichloroethylene from water using yolk-shell Fe/FeS@SiO2 particles
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摘要: 针对硫化纳米零价铁(Fe/FeS)颗粒间的团聚以及环境适应性差的问题,用正硅酸乙酯(TEOS)为原料制备中空介孔氧化硅球,再通过化学反应在壳内形成大尺寸核的方法制备具有蛋黄-蛋壳结构的Fe/FeS@SiO2材料以防止Fe/FeS的团聚并提高其活性,并将该材料用于三氯乙烯(TCE)的去除中;采用SEM和TEM观察、红外线光谱分析(FTIR)、X射线衍射分析(XRD)、X射线光电子能谱分析(XPS)等分析方法对材料进行了表征。结果表明,在Fe/FeS@SiO2材料还原降解TCE的实验中,Fe/FeS@SiO2去除TCE的最佳铁与硫的摩尔比(铁硫比)为30,并且在TCE初始浓度10 mg·L−1溶液中投加含有0.1 g Fe0、铁硫比为30的Fe/FeS@SiO2材料下,反应180 min后,TCE的去除率为90.75%,与未包裹氧化硅壳时的去除率(66.06%)相比,去除效果明显提高。介孔氧化硅壳阻止了Fe/FeS的团聚,其表面上的孔道使得材料具有更大的比表面积,加强了对TCE的吸附,同时材料中的空腔使得核与污染物的接触增加,提高了TCE的去除率。表征结果表明,Fe/FeS@SiO2材料具有特殊的结构,包括中心核、空腔以及介孔壳,可以防止Fe/FeS的团聚。
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关键词:
- TCE去除 /
- 硫化纳米零价铁(Fe/FeS) /
- 团聚 /
- Fe/FeS@SiO2材料 /
- 中空介孔氧化硅球
Abstract: Aiming at the agglomeration of sulfurized nano-zero-valent iron(Fe/FeS) due to its interaction between particles and poor environmental adaptability, the hollow mesoporous silica spheres were prepared by using tetraethyl orthosilicate (TEOS) as the silicon source, and then the Fe/FeS@SiO2 material with yolk-shell structure was prepared by“ship-in-a-bottle”method to prevent the agglomeration of Fe/FeS and improve its activity, which was used to remove trichloroethylene (TCE). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to characterize above materials. The characterization results revealled that the Fe/FeS@SiO2 yolk-shell particles had special structures, including active cores, mesoporous shells and hollow cavities, which could prevent the agglomeration of Fe/FeS. The experimental results showed that the optimum mass ratio of Fe to S for Fe/FeS@SiO2 preparation was 30. At TCE initial concentration of 10 mg·L−1, Fe dosage of 0.1 g and reaction time of 180 min, the TCE removal efficiency reached 90.75%, which was significantly higher than that of Fe/FeS (66.06%). The mesoporous silica shell inhibited the agglomeration of Fe/FeS, and the pores in the shell provide a larger specific surface area for the Fe/FeS@SiO2 yolk-shell particles, which enhances the TCE adsorption. Moreover, the cavity in the material could strengthen the contact between the cores and the contaminants, which improved the TCE removal efficiency. -
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