MCM-41介孔分子筛的制备及其重金属离子吸附研究

【作者】 朱文杰；

【导师】 马文会； 周阳；

【作者基本信息】 昆明理工大学 ， 冶金物理化学， 2013， 博士

【摘要】 自1992年Mobil公司的科研人员成功合成了以MCM-41为代表的M41S系列介孔分子筛以来,介孔材料以其高的比表面积和孔体积、均匀的孔径分布、丰富的表面基团等引起了广大科研工作者的兴趣。但到目前为止,MCM-41介孔分子筛仍未在工业上得到大规模的应用,除与其较低的水热稳定性有关外,另外非常重要的原因是受硅源的性质、模板体系、合成方法等的限制而导致其合成成本高以及不能大批量生产。本文的主要研究目的是以工业固体废弃物微硅粉和稻壳灰代替传统的有机硅源,利用硅源的特异宏观形貌低成本合成具有特殊形貌的MCM-41介孔分子筛,研究杂质存在情况下的最佳工艺条件和合成机理,并对该介孔分子筛的结构和重金属离子吸附性能进行表征和研究。主要包括以下几方面的内容：1.微硅粉的预处理及纯化研究对微硅粉的结构和性质进行测试分析,提出先预处理后再两步酸浸的纯化工艺路线。考察了酸浓度、酸浸温度和反应时间对微硅粉纯化的影响,并分析了杂质的去除机理。其最优纯化实验条件为：H2SO4和HCl的浓度为6mol/L,液固比为50：1,反应温度为60℃,反应时间为2h,搅拌速率为600r/min。2.微硅粉合成MCM-41介孔分子筛及其重金属吸附性能研究以酸浸微硅粉为硅源成功合成了MCM-41介孔分子筛,其孔径范围为2-5nm,研究了不同的硅源、CTAB/SiO2摩尔比、NaOH/SiO02摩尔比、晶化时问、晶化温度、模板剂的种类以及后处理工艺等因素对合成的MCM-41介孔分子筛结构和性能的影响,并探讨了该介孔分子筛的合成机理。MCM-41介孔分子筛最优化合成工艺条件条件是：CTAB/SiO2摩尔比为0.15,NaOH/SiO2摩尔比为0.2-0.3,晶化时间为48小时,晶化温度为90℃,采用CTAB和PEG6000混合模板剂。研究了MCM-41介孔分子筛对重金属离子Cu(Ⅱ)、Pb(Ⅱ)(?)口Cd(Ⅱ)的吸附性能并与硅藻土、沸石的吸附性能进行比较,探讨了介孔分子筛的用量、溶液pH值、吸附时间和重金属离子初始浓度对吸附的影响,并研究了吸附等温线、吸附动力学以及该介孔材料的重金属离子吸附机理。3.稻壳灰合成MCM-41介孔分子筛对稻壳灰的结构和性质进行了测试分析,并提出了预处理工艺。以预处理后的稻壳灰为硅源合成MCM-41介孔分子筛,考察了CTAB/SiO2摩尔比、NaOH/SiO2摩尔比、晶化温度和晶化时间对MCM-41结构和性能的影响,并初步探讨了MCM-41介孔分子筛的合成机理。其较佳的合成工艺条件为：pH为12、CTAB/SiO2摩尔比为0.05、晶化时间为72小时。4.MCM-41介孔分子筛的修饰及其重金属离子吸附研究对合成的MCM-41介孔分子筛进行了有机功能化表面修饰,研究了该复合介孔分子筛对重金属离子Cu(Ⅱ)、Pb(Ⅱ)和Cd(Ⅱ)的吸附性能并与修饰前的介孔分子筛的吸附性能进行比较。对吸附等温线、吸附动力学和吸附热力学作了全面的研究,并探讨了介孔分子筛功能化后的重金属离子吸附机理。更多还原

【Abstract】 Due to their excellent performances such as large specific surface area, uniform pore size distribution and rich surface functional groups, the M41s mesoporous molecular sieves have attracted great interest of scientists, since they had successfully synthesized by Mobil researchers in1992. On account of the properties of silica source, template system, synthesis methods etc, the MCM-41mesoporous molecular sieve has not been widely utilized so far.In this work, industrial solid waste, rice husk ash and silica fume were chosen to be silica resources instead of traditional organic silica resource. The main purpose of this work is to synthesis the MCM-41mesoporous molecular sieve with special morphology from particular macroscopic morphology of silica sources, studying the synthesis mechanism in condition of impurities, moreover characterizing the structure of mesoporous molecular sieve and the absorptive property of heavy metal ionic. This dissertation mainly was consisted by the following several aspects.1. Pretreatment and acid leaching purification of silica fumesBased on the characterization upon the structure and properties of silica fume, the purification process of silica fume had been determined. Firstly silica fume had been pretreated and then was leached by acids using two-steps method. The influence of concentration of acids, reaction temperature, reaction time, have been discussed. The mechanisms of cleaning impurities have also been studied. The best purification experiment conditions were as fellows:concentration of H2SO4and HC1was6mol/L, liquid-solid ratio was50:1, reaction temperature was60℃, reaction time was2h, and stirring speed was600r/min.2. MCM-41mesoporous molecular sieve synthesized from silica fumesMCM-41mesoporous molecular sieve were synthesized by hydrothermal method using acid leached silica fumes as silica source.The factors to influence the structure and performances of MCM-41were studied, such as properties of silica source, CTAB/SiO2molar ratio, NaOH/SiO2molar ratio, crystallization time, crystallization temperature, the type of template and the post-treatment technology. The mechanisms of synthesizing this MCM-41material were also discussed. The proper parameters under this trial condition were selected:CTAB/SiO2molar ratio was0.15, NaOH/SiO2molar ratio was0.2-0.3, Crystallization time was48h; Crystallization temperature was90℃; Template system was the mixture of CTAB and PEG6000.The MCM-41has been used for the adsorption of Cu(Ⅱ), Pb(Ⅱ) and Cd(Ⅱ) from aqueous solutions. The influence of the dosage of mesoporous molecular sieve, pH value of solution, adsorption time and initial concentration of heavy metal ions has been discussed. The adsorption isotherm, adsorption kinetics and the adsorption mechanism of heavy metal ionic of MCM-41have also been analyzed.3. MCM-41mesoporous molecular sieve synthesized from rice husk ashBased on the characterization upon the structure and properties of rice hull ash, the pretreatment technologies have been determined. MCM-41mesoporous molecular sieve was synthesized by hydrothermal method with rice husk ash as silica source. The factors such as CTAB/SiO2molar ratio, NaOH/SiO2molar ratio, crystallization temperature and time crystallizing were studied. The mechanism of synthesizing this MCM-41material was also discussed. The optimal parameters of synthesis for this silica source were listed in following:pH value was12, CTAB/SiO2molar ratio was0.05, and Crystallization time was72h.4. The study of MCM-41organic functionalization and heavy metal ionic adsorption performanceOrganic ligands containing fuctional groups (-NH2and-SH) were grafed to the surface and inner pore of a mesoporous molecular sieve MCM-41prepared from silica fume as silica source. The organic-inorganic composites were used for the adsorption of Cu(Ⅱ), Pb(Ⅱ) and Cd(Ⅱ) from aqueous solutions. The adsorption isotherm, adsorption kinetics and thermodynamics are exmined. The adsorption mechanisms of heavy metal ionic were also analyzed after the functionalization of MCM-41.更多还原