膜分散法制备纳米氧化锌

发布时间：2018-10-13 17:02

【摘要】： 纳米氧化锌具有优异的性能,在各个领域都有广泛应用。膜分散技术制备纳米材料是近年来材料学研究的热点,其以微孔膜或微滤膜为分散介质,在压力差作用下,将透过膜的液体分散成膜孔尺度水平的微小液滴,达到强化相际传质过程的目的。本文提出用中空纤维膜制成浸没式膜组件的膜分散技术制备纳米颗粒,以氯化锌和氢氧化钠为原料,分别利用单膜分散法和双膜分散法制备了纳米氧化锌。用正交设计实验对单膜分散法制备氧化锌时氯化锌溶液的浓度、碱锌浓度比、是否使用膜组件等条件进行了考察,得到单膜分散法制备纳米氧化锌的优化条件是：氯化锌浓度为0.14mol/L,碱锌浓度比为2,使用膜组件,以氢氧化钠为分散相,加入表面活性剂,水浴加热陈化2h,分散速率为20mL/min。利用上述条件制得平均粒径约为60nm,且粒径分布较窄的纳米氧化锌。利用双膜分散法制备纳米氧化锌,通过控制反应物浓度比,可以制备不同形貌的氧化锌。随碱锌浓度比的增大,所得产物由颗粒状转变为花状团簇。碱锌浓度比为2时可制备颗粒状氧化锌。通过对其他操作条件进行考察,在膜丝长度为2.5cm,氯化锌浓度为0.14mol/L,碱锌浓度比2,分散速率均为15mL/min,搅拌速度为1000rpm,陈化时间为2h时,制备出了平均粒径约为40nm,分布较窄的纳米氧化锌。与单膜分散法相比,此法将两种反应物同时分散到反应器中,适用于连续操作。通过向双膜分散法反应体系中添加表面活性剂,不仅可以减小颗粒的平均粒径,而且能使颗粒的平均粒径随反应持续时间的延长基本保持不变。在分散速率为70mL/min时,能够得到平均粒径约为45nm的纳米氧化锌颗粒。若将试验体系换为纯乙醇,在分散速率为20mL/min时,将得到平均粒径约为49nm的纳米氧化锌颗粒。这说明表面活性剂和有机溶剂乙醇都能起到很好的抑制团聚的作用。
[Abstract]:Nanometer ZnO has excellent properties and is widely used in various fields. Preparation of nanomaterials by membrane dispersion technology is a hot topic in recent years. Microporous membrane or microfiltration membrane is used as dispersing medium. Under the pressure difference, the liquid through the membrane is dispersed into tiny droplets at the pore level. The purpose of enhancing interphase mass transfer is achieved. In this paper, nanocrystalline particles were prepared by membrane dispersion technique with hollow fiber membrane as submerged membrane module. Zinc chloride and sodium hydroxide were used as raw materials to prepare nanometer zinc oxide by single membrane dispersion method and double membrane dispersion method, respectively. The concentration of zinc chloride solution, the ratio of alkali and zinc concentration, and the use of membrane modules in the preparation of zinc oxide by monofilm dispersion method were investigated by orthogonal design. The optimum conditions for the preparation of nano-ZnO by monofilm dispersion are as follows: the concentration of zinc chloride is 0.14 mol / L, the ratio of alkali to zinc is 2, the dispersion rate is 20 mL / min with sodium hydroxide as dispersed phase, surfactant is added, water bath is heated for 2 h, and the dispersion rate is 20 mL / min. The average particle size is about 60 nm and the particle size distribution is narrow. Nanometer zinc oxide was prepared by double film dispersion method. Different morphologies of zinc oxide could be prepared by controlling the concentration ratio of reactants. With the increase of alkaline zinc concentration, the product changed from granular to flower-like cluster. Granular zinc oxide can be prepared when the concentration ratio of alkali to zinc is 2. When the membrane length is 2.5 cm, zinc chloride concentration is 0.14 mol / L, alkali zinc concentration ratio is 2, dispersion rate is 15 mL / min, stirring rate is 1000rpm, aging time is 2 h, nanometer zinc oxide with average particle size of 40 nm and narrow distribution is prepared. Compared with the single membrane dispersion method, the two reactants are dispersed into the reactor simultaneously, which is suitable for continuous operation. By adding surfactant to the reaction system, the average particle size can be reduced, and the average particle size will remain unchanged with the prolongation of reaction time. Nanocrystalline zinc oxide particles with an average diameter of about 45nm can be obtained at the dispersion rate of 70mL/min. If the experimental system is changed to pure ethanol, the nanometer zinc oxide particles with an average diameter of about 49nm can be obtained at the dispersion rate of 20mL/min. This shows that surfactant and organic solvent ethanol can play a good role in inhibiting agglomeration.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：TB383.1

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