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MCM-22分子筛的合成、改性及其在处理染料废水中的应用研究

Study on the Synthesis, Modification of MCM-22 Zeolite and Its Application in Dye Wastewater Treatment

【作者】 苏晓渊

【导师】 成岳;

【作者基本信息】 景德镇陶瓷学院 , 环境工程, 2011, 硕士

【摘要】 MCM-22分子筛兼具十元环和十二元环的孔道特征,具有特殊的物化性质,已显示良好的应用前景。本论文旨在缩短MCM-22分子筛合成时间,降低合成成本,并通过掺杂改性优化其吸附方面的性能。本论文以硅溶胶为硅源、六亚甲基亚胺(HMI)为模板剂,按照SiO2∶0.3HMI∶0.035Al2O3∶0.2NaOH∶20H2O的摩尔配比,对常规合成MCM-22法和变温静态水热晶化法进行了比较,结果表明,变温静态水热晶化法缩短了合成的时间,降低了合成的温度,并合成出具有MWW层状结构的MCM-22分子筛。然后利用粉末X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、傅立叶红外(FT-IR)、热重-差热(TG-DTA)、N2吸附脱附等方法对其进行了表征。结果表明合成的MCM-22分子筛结晶度良好,孔径均匀,比表面积达到了388 m2/g,属于良好的吸附和催化材料。因杂原子的引入可以有效地调节分子筛的性质,还可以引入其它活性中心,使分子筛具有特殊的催化性能。本论文通过掺杂引入金属铈(Ce),按照0.0025Ce:SiO2∶0.3HMI∶0.035Al2O3∶0.2NaOH∶20H2O的摩尔配比合成了Ce-MCM-22,经XRD、TEM等表征表明,仍保持层状晶相结构特征,分子筛的有序结构性并没有被破坏,是一种较为新型的吸附材料。在Ce-MCM-22分子筛对模拟废水亚甲基蓝溶液的吸附性能研究中,结果表明在Ce-MCM-22分子筛的投加量为0.6g/L,亚甲基蓝浓度为2.0mg/L,pH为7,震荡吸附60分钟时,吸附效果最好,脱色率达到90.5%。Ce-MCM-22吸附动力方程拟二级方程y=0.4657x +1.2005,R2=0.9995,相对拟一级反应模型,这个结果相关性更好,更能真实地反映分子筛吸附亚甲蓝溶液的反应机理。然后通过掺杂钛(Ti)和非金属氮(N)元素,按照0.008N:SiO2∶0.03TiO2∶0.3HMI∶0.035Al2O3∶0.2NaOH∶20H2O的摩尔配比合成了N-Ti-MCM-22分子筛,并研究了它光催化降解模拟废水亚甲基蓝溶液的效果和溶液pH、亚甲基蓝浓度、分子筛投加量等因素对其效果的影响。结果表明,采用含氮量为0.008 mol的Ti-MCM-22分子筛光催化剂加入量为1g/L,亚甲基蓝溶液浓度4.0mg/L,pH值为中性左右,光催化时间40分钟,对亚甲基蓝脱色率和降解率分别达到95.9%和97.8%,是良好的复合催化材料。

【Abstract】 Owing to its unique structure comprising both 10 member-ring (MR) and 12MR channel system and special physiochemical properties, MCM-22 zeolite has shown many promising applications. This paper aims to reduce the synthesis of MCM-22 molecular sieve time, and low-cost synthesis, and optimize its absorption performance by doped.In this paper, silica sol was used as silicon source, hexamethylene imine (HMI) as template agent, with the molar ratio of SiO2: 0.3HMI: 0.035Al2O3: 0.2NaOH: 20H2O, and compared the method of conventional synthesis of MCM-22 and the temperature change static hydrothermal method, The results showed that the static temperature change hydrothermal method reduce the synthesis time, reducing the synthesis temperature, and MCM-22 molecular sieve with MWW of layer structure was synthesized. Molecular sieve of MCM-22 was characterizated by power X-ray diffraction(XRD), scanning electron microscope(SEM)、transmission electron microscopy (TEM),fourier transform infrared spectroscopy (FT-IR), TG-DTA,N2 adsorption and desorption and so on. The results showed that the synthesis of MCM-22 molecular sieve pore size was very uniformity, specific surface area was reached 388 m2/g, and it is a good adsorption and catalytic materials.Due to the introduction of heteroatoms can effectively regulate the nature of zeolite, but also the introduction of other active center, so zeolite has a special catalytic property. In this paper, synthesized Ce-MCM-22 zeolite with the molar ratio of 0.0025Ce:SiO2∶0.3HMI∶0.035Al2O3∶0.2NaOH∶20H2O,and characterizated it by XRD, TEM. The results show it maintains crystalline layered structure, the ordered zeolite structure has not been destroyed, it is a new type of adsorbent material. In the study of Ce-MCM-22 molecular sieve adsorption methylene blue, the results showed that Ce-MCM-22 zeolite dosage was 0.6g / L, methylene blue concentration was 2.0mg / L, pH was 7, the shock absorption time xas 60 minutes, the adsorption effect was best, and decolorization rate reached 90.5%. Ce-MCM-22 adsorption dynamic second equation was y = 0.4657x + 1.2005, R2 = 0.9995, relative to be a equation model, the results related to be better, more truly reflect the response of molecular sieve adsorption of methylene blue solution mechanism.Then synthesized N-Ti-MCM-22 molecular sieves by doped titanium (Ti) and non-metallic nitrogen (N), synthesized N-Ti-MCM-22 zeolite with the molar ratio of 0.008N:SiO2∶0.03TiO2∶0.3HMI∶0.035Al2O3∶0.2NaOH∶20H2O and study of its photocatalytic degradation of methylene blue solution effects, and study of the solution pH, methylene blue concentration, zeolite dosage factors that influence their effect. The results showed that the nitrogen content was 0.008 mol of Ti-MCM-22 zeolite , and zeolite dosage was 1g / L, the concentration of methylene blue solution was 4.0mg / L, pH was neutral, the photocatalytic time was 40 minutes, the methylene blue decoloration rate and the degradation rate reached 95.9% and 97.8%, was a good composite catalytic materials.

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