【作者】 李莉；

【导师】 莫尊理；

【作者基本信息】 西北师范大学 ， 无机化学， 2017， 硕士

【摘要】 分子筛是一类具有多孔结构的介孔材料,属于含水硅酸盐化合物,因其骨架结构中含有丰富的孔道使其具有较大的比表面积,孔容和孔径分布均匀等特点,使其被广泛的应用于催化、吸附分离及离子交换领域。分子筛一般是粉末状颗粒,在使用过程中达到饱和吸附后难以与作用对象分离,从而不易被重复使用。本课题应用了磁性分离技术,当分子筛与磁性材料结合后,在外部磁场下就可以将分子筛从作用体系中快速分离,解决了固液分离难的问题,为其循环利用创造了条件,因此,磁性分子筛在吸附领域成为研究热点之一。本实验利用共沉淀法和溶剂热法分别制备了不同尺寸和形貌的Fe₃O₄粒子,通过探讨溶剂热法中NaOH、PVP加入量以及反应时间等影响合成Fe₃O₄粒子的因素,找到最佳合成条件,比较发现溶剂热法制备的球形Fe₃O₄粒子形貌高度可控,粒子尺寸均匀且磁性能较好,因此,我们选择球形Fe₃O₄粒子进行下一步的应用。为了探索合成性能较好的磁性MCM-41介孔分子筛,采用水热合成法,通过在合成MCM-41介孔分子筛的过程中,在反应混合物中加入了不同质量的球形Fe₃O₄粒子,成功制备出了含不同质量Fe₃O₄粒子的磁性MCM-41介孔分子筛。通过傅里叶红外光谱（FT-IR）、X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、振动样品磁强计（VSM）、氮气吸附-脱附（BET）等手段对合成的不同样品进行性能和结构表征,用紫外-可见分光光度计测定合成的性能最佳的磁性MCM-41介孔分子筛对罗丹明B的吸附性能。实验结果表明,Fe₃O₄粒子的引入并没有破坏MCM-41介孔分子筛的骨架结构,对介孔分子筛的孔道结构影响也较小,随着Fe₃O₄粒子加入量的增加,所制备的磁性MCM-41介孔分子筛磁性能增强,最高达29.26emu/g。罗丹明B吸附实验表明与纯MCM-41介孔分子筛相比磁性MCM-41介孔分子筛的吸附性能略有下降,但磁性MCM-41介孔分子筛在磁场作用下可以快速分离。对吸附过程进行吸附模型拟合研究发现,吸附过程更接近Langmuir模型,说明吸附过程为单分子层吸附。并且吸附性能受吸附条件影响较大,在罗丹明B初始浓度为100mg/L,温度为20℃,溶液pH值为4.0的条件下,吸附剂的最佳加入量为0.5g/L,吸附进行120min时,对罗丹明B的去除率达86.7%。对吸附后的磁性MCM-41介孔分子筛重复进行3次吸附解吸操作,结果表明,磁性MCM-41介孔分子筛仍然具有很高的吸附性,并且它的吸附能力还可以保持在70%左右,重复性实验表明制备的磁性MCM-41介孔分子筛吸附剂具有良好的稳定性,可以被进行多次重复利用。更多还原

【Abstract】 Molecular sieve is a kind of mesoporous material with porous structure,which belongs to the water-containing silicate compound.Because of its rich structure in the skeleton structure,it has the characteristics of large specific surface area,uniform pore volume and pore size distribution.Molecular sieves have been widely used in the field of catalysis,adsorption separation and ion exchange.Molecular sieves are generally powdered particles,in the course of the use of saturated adsorption is difficult to separate with the role of the object,which is not easy to be reused.In this paper,magnetic separation technology is applied.When molecular sieves are combined with magnetic materials,the molecular sieves can be separated from the reaction system under the external magnetic field,which solves the problem of solid-liquid separation and creates the conditions for the recycling.Therefore,Magnetic molecular sieves become one of the hotspots in the field of adsorption.In this experiment,Fe₃O₄ particles with different sizes and morphologies were prepared by coprecipitation method and solvothermal method respectively.The optimum conditions for the synthesis of Fe₃O₄ particles were investigated by influencing the addition of NaOH,PVP and reaction time in solvothermal method.It is found that the spherical Fe₃O₄ particles prepared by solvothermal method are highly controllable,the particle size is uniform and the magnetic properties are good.Therefore,we choose spherical Fe₃O₄ particles for the next application.In order to explore the magnetic properties of MCM-41 mesoporous molecular sieves,MCM-41 mesoporous molecular sieves were prepared by hydrothermal synthesis method.In the process of synthesizing MCM-41 mesoporous molecular sieves,different kinds of spherical Fe₃O₄ particles were added to the reaction mixture.Magnetic MCM-41 mesoporous molecular sieves containing different Fe₃O₄ particles.（FT-IR）,X-ray diffraction（XRD）,transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,vibrating sample magneto-meter（VSM）,nitrogen adsorption-desorption（BET）And other means of the synthesis of different samples of performance and structural characterization.The adsorption properties of the composite MCM-41 mesoporous molecular sieve composites were measured by UV-Vis spectrophotometer.The experimental results show that the introduction of Fe₃O₄ particles does not destroy the skeletal structure of MCM-41 mesoporous molecular sieves and has little effect on the pore structure of mesoporous molecular sieves.With the increase of the addition of Fe₃O₄ particles,the magnetic properties of the prepared magnetic MCM-41 mesoporous molecular sieves were enhanced up to 29.26emu/g.The adsorption performance of magnetic MCM-41 mesoporous molecular sieves decreased slightly compared with pure MCM-41 mesoporous molecular sieves,but the magnetic MCM-41 mesoporous molecular sieves could be separated quickly under magnetic field.The adsorption model was studied by adsorption model.It was found that the adsorption process was closer to Langmuir model,indicating that the adsorption process was monomolecular adsorption.And the adsorption performance was influenced by the adsorption conditions.Under the condition of initial concentration of Rhodamine B of 100mg/L,temperature of 20℃and pH of solution 4.0,the optimum amount of adsorbent was 0.5g/L,120min,the removal rate of rhodamine B was 86.7%.The results show that the magnetic MCM-41 mesoporous molecular sieves still have high adsorption capacity and the adsorption capacity of the MCM-41 mesoporous molecular sieves can be maintained at about 70%.The reproducibility experiments showed that the prepared MCM-41 mesoporous molecular sieve adsorbents had good stability and could be reused several times.更多还原