本文選題：分散改性　切入點(diǎn)：羥乙基纖維素　出處：《昆明理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：納米零價鐵(nano zero-valent iron, NZVI)由于高反應(yīng)活性、大比表面積和環(huán)境友好性常被用來處理多種地下水和土壤中的污染物,如氯代有機(jī)物,重金屬離子,抗生素和染料廢水等。但其優(yōu)點(diǎn)同時也是限制應(yīng)用的一個因素,由于零價鐵顆粒間的磁性導(dǎo)致其易團(tuán)聚,高反應(yīng)活性也使其容易因接觸氧氣而氧化。為了使NZVI技術(shù)能更好的應(yīng)用于實際,研究者們嘗試用負(fù)載或添加分散劑的方式來改善零價鐵顆粒的團(tuán)聚和氧化。其中綠色分散劑因為簡單廉價而大受青睞,文章中的羥乙基纖維素(Hydroxyethyl cellulose, HEC)和羥丙基甲基纖維素(Hydroxypropylmethyl cellulose, HPMC)被創(chuàng)新性的作為分散劑成功應(yīng)用于納米零價鐵(NZVI)的分散改性。研究對改性和未改性的納米零價鐵進(jìn)行了系統(tǒng)表征,包括X射線衍射(XRD)、掃描電子纖維鏡(SEM)、透射電子顯微鏡(TEM)、傅里葉變換紅外光譜(FT-IR)、X射線光電子能譜(XPS)以及比表面積測定(BET)表征。表征結(jié)果說明,與未改性的納米零價鐵相比,經(jīng)纖維素改性后的納米零價鐵顆粒呈均勻的球狀,并具有更大的比表面積,更小的顆粒粒徑,且未改性顆粒易氧化,而改性后的顆粒在抗氧化方面具有優(yōu)勢。對改性和未改性的納米零價鐵顆粒進(jìn)行了比表面積的測定,BNZVI、ENZVI和PNZVI的比表面積分別為33.7 m2/g、38.2 m2/g和37.5 m2/g。其結(jié)果說明,與未改性的BNZVI相比,改性的納米零價鐵顆粒的比表面積有所增大,而粒徑尺寸有所減小。其原因是由于分散劑HEC和HPMC在納米零價鐵表面的包覆,使得鐵顆粒變得更加均勻和分散,從而使顆粒粒徑減小,比表面積增加。其中,紅外光譜分析中,HEC和HPMC改性納米零價鐵顆粒在1450 cm-1和3207 cm-1處有兩個明顯的峰值分別代表HEC和HPMC中所含的亞甲基和羥基官能團(tuán),可說明零價鐵顆粒表面HEC和HPMC的存在。而XPS表征結(jié)果不僅說明了分散劑改性納米零價鐵確實具有抗氧化效果,譜圖上的C-C、C-O峰也說明了HEC和HPMC的存在。除此之外,文中還研究了納米零價鐵降解染料過程中的幾個影響因素,包括分散劑添加量、染料類型、初始濃度,NZVI投加量、溶液初始pH以及反應(yīng)的溫度。結(jié)果表明,當(dāng)分散劑添加量為1.24%wt時改性零價鐵的性能最優(yōu),而橙黃Ⅱ也是一種易降解的有機(jī)染料。從脫色率可發(fā)現(xiàn),脫色率隨著溶液pH或溶液的初始濃度的增加而降低；隨著NZVI投加量和反應(yīng)溫度的增加而升高。在優(yōu)化條件下,NZVI投加量為0.7g/L的時候,HEC改性和HPMC改性零價鐵對橙黃II的脫色降解率可分別達(dá)到96.33%和98.62%。研究還對分散劑HEC和HPMC改性納米零價鐵的可能途徑進(jìn)行了闡述,分析了改性零價鐵顆粒對染料的脫色降解機(jī)理。整個脫色降解過程符合偽一級反應(yīng)動力學(xué)原理。研究證明HEC和HPMC可以良好的改性納米零價鐵并用于染料廢水的降解。
[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，

本文編號：1644554