活性炭负载纳米零价铁的制备及其对难降解有机物去除性能的研究

发布时间：2019-06-26 21:07

【摘要】：本文针对纳米铁颗粒在去除污染物过程中易团聚、活性降低的问题,将纳米铁(NZVI)负载到活性炭载体上,制备出活性炭负载纳米铁(NZVI/AC)。选择三卤甲烷(THMs)和丙烯腈两种难降解有机污染物作为目标污染物,研究NZVI/AC在去除难降解有机物方面的性能,并对去除机理进行初步研究。本文主要进行了以下方面的研究：1.NZVI和NZVI/AC的制备和表征：采用液相还原法制备纳米铁(NZVI),以活性炭(AC)为载体制备负载型纳米铁NZVI/AC,并对AC、NZVI和NZVI/AC进行表征。NZVI、AC和NZVI/AC的结构形貌是用扫描电镜(SEM)和透射电镜(TEM)进行表征。通过傅里叶红外光谱仪(FT-IR).X-射线衍射仪(XRD)和X-射线光电子能谱(XPS)对样品的表面官能团、晶体结构和化学组成进行考察。比表面积测定仪和电子耦合等离子体原子发射光谱(ICP-AES)分别用来测定样品的比表面积、孔径和和铁元素含量。结果表明采用活性炭的承载作用和聚乙二醇-4000的分散作用,有效降低了纳米铁颗粒的团聚程度。SEM和TEM的结果证明了制备得到的负载纳米铁颗粒大小较为均匀,粒径在30-80 nm,铁颗粒大体呈球状形貌,部分分布在活性炭外表面上,部分进入活性炭的孔道内。NZVI的BET比表面积为25.8 m2/g,负载后NZVI/AC的比表面积为63.9 m2/g。NZVI/AC具有更大的比表面积和更高的活性。能谱EDS分析NZVI/AC颗粒表面Fe元素形态及含量,实验所得的结果与理论值(10%)相接近。XRD、FTIR和XPS的结果都证实了纳米零价铁成功地负载到了活性炭上,并且负载的纳米铁有良好的抗氧化能力,分散性更好。2.对比研究了NZVI、AC和NZVI/AC对三卤甲烷(THMs)的去除效果：并单独考察了NZVI/AC颗粒的投加量、反应时间和体系初始pH值对三卤甲烷去除效果的影响。结果表明对三卤甲烷的去除能力和去除速率大小依次为NZVI/ACNZVIAC和ACNZVI/ACNZVI。增加颗粒投加量有助于提高去除率,但当投加量增加到1.8 g/L后,去除效果的增加幅度不大。NZVI/AC的投加量为1.8 g/L, pH为中性时,对THMs的去除效果最好。实验结果证明了溴代甲烷比氯代甲烷容易去除,三卤甲烷的去除效果和去除速率遵循顺序CHBr3CHBr2ClCHBrCl2CHCl3。并且,实验结果也揭示了高溴取代数的三卤甲烷的去除率要比低溴取代数的三卤甲烷的去除率高(CHBr3CHBr2ClCHBrCl2).四种三卤甲烷的去除率均达到90%以上,其中CHBr3、CHBr2Cl、CHBrCl2和CHCl3的最高去除率分别为100%、97.8%、95%和94.5%。3.对比研究了活性炭负载纳米铁和活性炭对丙烯腈的去除效果：结果表明NZVI/AC对丙烯腈的去除效果高于AC,主要是由于活性炭本身对丙烯腈具有吸附作用,并且反应中生成的Fe2+、[H]和Fe0本身都具有很强的还原性,能够与丙烯腈发生反应。伪一级和伪二级动力学方程都不能很好地表述NZVI/AC去除丙烯腈的过程。Freundich模型能够更好的描述NZVI/AC对丙烯腈的吸附等温线,相关系数R20.998。通过紫外可见分光光度法和傅里叶红外谱图的分析可知,NZVI/AC可以分解丙烯腈分子,主要是由于反应产生的自由氢基[H]和新生成的Fe2+与丙烯腈之间的化学氧化还原作用。采用活性污泥耗氧速率的测定对活性污泥活性进行测定,结果表明经过NZVI/AC的预处理可以提高丙烯腈废水的可生化性,降低其对活性污泥的毒性。
[Abstract]:In this paper, the nano-iron (NZVI) loaded on the activated carbon carrier was prepared by loading the nano-iron (NZVI) on the activated carbon carrier, and the nano-iron (NZVI/ AC) was prepared by loading the nano-iron (NZVI) on the activated carbon carrier. The properties of non-degradable organic pollutants of trihalomethane (THMs) and acrylonitrile were selected as target pollutants, and the removal mechanism was studied. The preparation and characterization of NZVI and NZVI/ AC were studied in this paper. The nano-iron (NZVI) was prepared by a liquid-phase reduction method, and the supported nano-iron NZVI/ AC was prepared by using active carbon (AC) as a carrier, and the AC, NZVI and NZVI/ AC were characterized. The structure and morphology of NZVI, AC and NZVI/ AC were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface functional group, crystal structure and chemical composition of the sample were investigated by means of Fourier transform infrared (FT-IR), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The specific surface area, pore size and iron element content of the sample were determined by the specific surface area tester and the electron-coupled plasma atomic emission spectrometry (ICP-AES), respectively. The results show that the loading action of the activated carbon and the dispersion of the polyethylene glycol-4000 effectively reduce the degree of agglomeration of the nano-iron particles. The results of SEM and TEM show that the prepared supported nano-iron particles have a uniform size, a particle size of 30-80nm, and the iron particles are in a spherical shape, and are partially distributed on the outer surface of the active carbon and partially enter the pore canal of the active carbon. The BET specific surface area of NZVI was 25.8 m2/ g, and the specific surface area of NZVI/ AC after loading was 63.9 m2/ g. NZVI/ AC had a greater specific surface area and higher activity. The morphology and content of Fe element in the surface of NZVI/ AC particles were analyzed by energy spectrum EDS, and the experimental results were close to the theoretical value (10%). The results of XRD, FTIR and XPS all confirmed that the nano-valent iron was successfully loaded on the activated carbon, and the loaded nano-iron had good anti-oxidation ability and better dispersibility. The effect of NZVI, AC and NZVI/ AC on the removal of trihalomethane (THMs) was studied. The effects of the dosage, reaction time and initial pH of NZVI/ AC on the removal of trihalomethane were investigated. The results show that the removal and removal rate of trihalomethane are NZVI/ ACNZVIAC and ACNZVI/ ACNZVI. Increasing the dosage of the particles helps to improve the removal rate, but when the dosage is increased to 1.8 g/ L, the increase of the removal effect is not large. When the dosage of NZVI/ AC is 1.8 g/ L and the pH is neutral, the removal effect of the THMs is the best. The experimental results show that the bromomethane is easier to remove than the chloromethane, and the removal effect and the removal rate of the trihalomethane follow the order of CHBr3CHBr2ClCHBrCl2CHCl3. Furthermore, the experimental results also show that the removal rate of the trihalomethane with the high bromine number is higher than that of the low bromine number of the trihalomethane (CHBr3CHBr2ClCHBrCl2). The removal rate of the four trihalomethane was over 90%, and the highest removal rates of CHBr3, CHBr2Cl, CHBrCl2 and CHCl3 were 100%, 97.8%,95% and 94.5% respectively. The effect of activated carbon loaded iron and active carbon on the removal of acrylonitrile was studied. The results showed that the effect of NZVI/ AC on the removal of acrylonitrile was higher than that of AC, mainly due to the adsorption of the activated carbon itself on the acrylonitrile, and the Fe 2 + generated in the reaction. [H] and Fe0 itself have very strong reducibility and can react with acrylonitrile. Both the pseudo-first and the pseudo-second-order kinetic equations do not well state the process of removing the acrylonitrile from the NZVI/ AC. The Freundich model can better describe the adsorption isotherm of NZVI/ AC to acrylonitrile, and the correlation coefficient R20.98. It is known from the analysis of the UV-visible spectrophotometry and the Fourier infrared spectroscopy that the NZVI/ AC can decompose the acrylonitrile molecule, mainly due to the free hydrogen group[H] produced by the reaction and the chemical oxidation reduction effect between the newly formed Fe 2 + and the acrylonitrile. The activity of activated sludge was determined by the determination of the oxygen consumption rate of activated sludge. The results showed that the pretreatment of NZVI/ AC could improve the biodegradability of acrylonitrile wastewater and reduce its toxicity to activated sludge.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;TQ424.1

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