柠檬酸法合成介孔材料及其在Cu²⁺去除中的应用

【作者】 黄苏君；

【导师】 李溪； 潘浦敦；

【作者基本信息】 复旦大学 ， 环境工程， 2011， 硕士

【摘要】 介孔氧化硅和磁性介孔氧化硅纳米复合材料因其在化学化工、生物医药、环境和能源等领域中具有重要的潜在应用而成为当前研究的热点。介孔材料的合成一般采用表面活性剂模板路径通过超分子自组装形成,然而这种方法合成过程过于复杂,高温煅烧、有机溶剂萃取、微波脱除等手段来去除表面活性剂耗能耗时且模板剂一般难以回收利用,此外高温煅烧模板分解产生的有害物质又会带来严重的环境污染。来自于冶金、电镀、印刷、纺织、化肥和造纸工业等诸多领域中的Cu2+是废水中一种常见的重金属。较高的Cu2+浓度不但危害水生动植物的生长,阻碍水体自净,还将影响人类健康。吸附法是一种去除污水中重金属离子的有效方法,但寻找合适的吸附材料是其广泛应用的关键。为了开辟出一条简单、廉价合成介孔材料的新路径,以更好地满足环境净化应用如重金属Cu2+的有效去除,本论文做了以下几方面的探索工作。(1)基于溶胶-凝胶技术通过一种简单、廉价的非表面活性剂合成路径在水溶液体系中合成了一种具有丰富硅烷羟基的介孔氧化硅材料。此法以柠檬酸为模板,正硅酸乙酯((TEOS)为硅源,柠檬酸在合成过程中可同时作为成孔剂和TEOS水解的酸催化剂。另外通过简单水洗的方法可以很容易地将柠檬酸模板去除,从而使合成的介孔氧化硅孔道中保留了丰富的硅烷羟基,滤液干燥后可将柠檬酸回收并循环利用。对合成的介孔氧化硅材料进行了XRD、扫描电子显微镜(SEM)、透射电镜(TEM)、傅里叶红外光谱(FT-IR)和N2吸脱附等的物性表征。丰富的硅烷羟基有利于有机官能团的嫁接,因此我们对介孔氧化硅进行了氨基嫁接修饰并将其用于水溶液中重金属Cu2+离子吸附研究,结果表现出较好的吸附性能。(2)磁性介孔复合材料是当前研究的一大热点,基于上述开发的非表面活性剂柠檬酸路径合成介孔氧化硅的方法,本章中将其推广用于合成有序的磁性介孔Fe3O4@SiO2纳米复合微球。N2吸脱附表征发现此类材料具有较大的表面积和孔体积、孔径单一,SEM和TEM显示该复合材料是核-壳结构的球形形貌且氧化硅壳具有一定的介孔有序性,FTIR结果证实该磁性介孔氧化硅复合材料同样具有丰富的硅烷羟基基团。将3-APTES嫁接的磁性介孔氧化硅复合材料用于对Cu2+离子吸附研究,该材料表现出很好的吸附性能和磁性可回收能力。更多还原

【Abstract】 Mesoporous silica and magnetic mesoporous silica nanoparticles are becoming research focus due to their important potential applications in chemical industry, biomedicine, environment, energy sectors and so on. So far, mesoporous silica is a type of porous material whose synthesis procedure follows supramolecular self-assembly way generally by means of surfactant as the template. However, the mesoporous silica formation method is too complex and also the removal process of surfactant by high-temperature calcination, solvent extraction, microwave removal and else will be energy and time-consuming. The template will be hardly recycled and the harmful substances from template decomposition will result in serious environmental pollution.Cu2+is a common heavy metal in wastewater and generally from metallurgy, electroplating, printing, textile, fertilizer, paper industries and many other areas. High Cu2+concentration is not only hazardous to the aquatic plants and animals, impeding water purification, but also harmful to human health. Adsorption method for heavy metal ions removal is an effective way but the key is to find suitable absorption materials for the sake of wide applications.In order to open up a simple path for mesoporous materials’formation by means of non-surfactants, from which can remove Cu2+from wastewater well, this paper just explores the aspects as follows.1. This paper tells a simple and low-cost route for synthesizing mesoporous silica materials with high silanol groups by means of sol-gel technique under aqueous solution system. This method takes citric acid as the template, tetraethylorthosilicate (TEOS) as the silica source. In this synthesis, the citric acid can directly work as an acid catalyst for the hydrolysis of TEOS besides the function as a pore-forming agent. By using a water extraction method the citric acid template in as-prepared mesoporous silica composite can be easily removed and rich silanol groups were retained in the mesopores, then the citric acid in the filtrate can be recycled after being dried. The structural properties of the obtained mesoporous silica materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption analysis. Due to rich silanol groups are propitious to the graft of organic functional groups, we used amino groups to modify the mesoporous silica and then take it to the use of Cu2+removal from aqueous solution, which showed excellent adsorption properties.2. Magnetic mesoporous nano-composite materials become research hot spot currently. Based on the above non-surfactant citric acid way for mesoporous silica synthesis, this paper extended its application to the synthesis of ordered mesoporous Fe3O4@SiO2 nanocomposite microspheres. N2 adsorption/desorption experiment results showed the high surface area, large pore volume and single aperture of the magnetic mesoporous Fe3O4@SiO2 nanoparticles. TEM and SEM images showed that the composite material is of spherical shape with core-shell structure and meanwhile silica shell has a certain mesoporous ordering. FTIR also showed Fe3O4@SiO2 nanocomposite microspheres have rich silanol groups. After functioned with amino group, the nanocomposite microspheres presented large Cu2+removal capacity and good magnetic recoverable capacity.更多还原