纤维素改性纳米零价铁及其对水中染料的脱色降解研究

发布时间：2018-03-21 15:58

  本文选题：分散改性　切入点：羟乙基纤维素　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：纳米零价铁(nano zero-valent iron, NZVI)由于高反应活性、大比表面积和环境友好性常被用来处理多种地下水和土壤中的污染物,如氯代有机物,重金属离子,抗生素和染料废水等。但其优点同时也是限制应用的一个因素,由于零价铁颗粒间的磁性导致其易团聚,高反应活性也使其容易因接触氧气而氧化。为了使NZVI技术能更好的应用于实际,研究者们尝试用负载或添加分散剂的方式来改善零价铁颗粒的团聚和氧化。其中绿色分散剂因为简单廉价而大受青睐,文章中的羟乙基纤维素(Hydroxyethyl cellulose, HEC)和羟丙基甲基纤维素(Hydroxypropylmethyl cellulose, HPMC)被创新性的作为分散剂成功应用于纳米零价铁(NZVI)的分散改性。研究对改性和未改性的纳米零价铁进行了系统表征,包括X射线衍射(XRD)、扫描电子纤维镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)以及比表面积测定(BET)表征。表征结果说明,与未改性的纳米零价铁相比,经纤维素改性后的纳米零价铁颗粒呈均匀的球状,并具有更大的比表面积,更小的颗粒粒径,且未改性颗粒易氧化,而改性后的颗粒在抗氧化方面具有优势。对改性和未改性的纳米零价铁颗粒进行了比表面积的测定,BNZVI、ENZVI和PNZVI的比表面积分别为33.7 m2/g、38.2 m2/g和37.5 m2/g。其结果说明,与未改性的BNZVI相比,改性的纳米零价铁颗粒的比表面积有所增大,而粒径尺寸有所减小。其原因是由于分散剂HEC和HPMC在纳米零价铁表面的包覆,使得铁颗粒变得更加均匀和分散,从而使颗粒粒径减小,比表面积增加。其中,红外光谱分析中,HEC和HPMC改性纳米零价铁颗粒在1450 cm-1和3207 cm-1处有两个明显的峰值分别代表HEC和HPMC中所含的亚甲基和羟基官能团,可说明零价铁颗粒表面HEC和HPMC的存在。而XPS表征结果不仅说明了分散剂改性纳米零价铁确实具有抗氧化效果,谱图上的C-C、C-O峰也说明了HEC和HPMC的存在。除此之外,文中还研究了纳米零价铁降解染料过程中的几个影响因素,包括分散剂添加量、染料类型、初始浓度,NZVI投加量、溶液初始pH以及反应的温度。结果表明,当分散剂添加量为1.24%wt时改性零价铁的性能最优,而橙黄Ⅱ也是一种易降解的有机染料。从脱色率可发现,脱色率随着溶液pH或溶液的初始浓度的增加而降低；随着NZVI投加量和反应温度的增加而升高。在优化条件下,NZVI投加量为0.7g/L的时候,HEC改性和HPMC改性零价铁对橙黄II的脱色降解率可分别达到96.33%和98.62%。研究还对分散剂HEC和HPMC改性纳米零价铁的可能途径进行了阐述,分析了改性零价铁颗粒对染料的脱色降解机理。整个脱色降解过程符合伪一级反应动力学原理。研究证明HEC和HPMC可以良好的改性纳米零价铁并用于染料废水的降解。
[Abstract]:Nanocrystalline zero-valent irons (NZVI) are often used to treat various pollutants in groundwater and soil, such as chlorinated organic compounds, heavy metal ions, due to their high reactive activity, large specific surface area and environmental friendliness. Antibiotics and dye wastewater, etc., but their advantages are also a factor limiting their application, because of the magnetic properties between zero-valent iron particles, they are easy to reunite. High reactive activity also makes it easy to be oxidized by exposure to oxygen. In order to make the NZVI technology more practical, Researchers are trying to improve the agglomeration and oxidation of zero-valent iron particles by loading or adding dispersants, among which green dispersants are popular because they are simple and cheap. The hydroxyethyl cellulose hydroxyethyl celluloseand hydroxypropylmethyl cellulosein (HPMCs) have been innovatively used as dispersants for the dispersion modification of nanocrystalline zero-valent iron (NZVI). It includes X-ray diffraction, scanning electron fiber mirror (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPSs) and specific surface area measurement (BET). The characterization results show that compared with the unmodified nanocrystalline zero-valent iron, The nano-sized zero-valent iron particles modified by cellulose have uniform spherical shape, larger specific surface area, smaller particle size, and the unmodified particles are easy to be oxidized. The specific surface area of modified and unmodified NZVIENZVI and PNZVI were 33.7 m2 / g 38.2 m2 / g and 37.5 m2 / g / g, respectively. The results showed that compared with the unmodified BNZVI, the modified particles had a specific surface area of 33.7m-2 / g and 37.5m2grespectively. The specific surface area of the modified nano-zero-valent iron particles increased, while the particle size decreased. The reason was that the dispersants HEC and HPMC coated the nano-zero-valent iron particles, which made the iron particles more uniform and dispersed. Therefore, the particle size decreases and the specific surface area increases. Among them, in infrared spectroscopy analysis, there are two distinct peaks at 1450 cm-1 and 3207 cm-1 for HEC and HPMC, respectively, which represent the methylene and hydroxyl functional groups in HEC and HPMC, respectively. The results of XPS characterization not only show that nano-sized zero-valent iron modified by dispersant has anti-oxidation effect, but also indicate the existence of HEC and HPMC on C-CnC-O peak. Several factors affecting the degradation of dyes by nanocrystalline zero-valent iron, including the amount of dispersant, the type of dye, the initial concentration of NZVI, the initial pH of the solution and the reaction temperature, were also studied. When the amount of dispersant is 1.24wt, the property of modified zero-valent iron is the best, and orange 鈪，

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