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粉煤灰制备13X分子筛及VOCs吸附性能研究

Preparation of 13X zeolite by coal fly ash for adsorption of volatile organic compounds

  • 摘要: 粉煤灰属于大宗工业固废,极大地危害着自然环境和人类的身心健康,如何高效高值化利用粉煤灰是目前面临的科学和技术问题。挥发性有机物(VOCs)是具有挥发性的有机污染物,对人体有“三致”作用。分子筛因其独特的孔结构,具有优良的离子交换、催化和吸附性能,在众多领域得到广泛应用。采用碱熔活化结合水热合成法利用粉煤灰制备13X分子筛,分析了硅铝比、碱度、晶化时间因素对制备分子筛的影响,考察了VOCs吸附性能并与活性炭对比分析。利用XRD、SEM和BET手段对分子筛晶型、比表大面积和孔径等结构进行表征,结果表明:13X分子筛结晶度好且纯度高,粒径为1~3 μm分布基本均匀,BET比表面积达到990.3 m2/g,总孔容约为0.72 cm3/g,平均孔径为1.1 nm;母液硅铝比影响分子筛合成类型;提高碱度可以加快晶化速率,缩短晶化时间,促进硅酸盐离子与铝酸盐离子的缩聚反应;分子筛在晶化阶段生长较快。通过13X分子筛和煤基颗粒活性炭对VOCs吸附性能对比试验发现,13X分子筛VOCs吸附容量高于活性炭,且VOCs分子极性越大,吸附容量越高。研究不仅可达到固废和废气之间“以废治废,变废为宝”的目的,同时还为低成本高效合成沸石分子筛提供思路,提高大宗固废的利用率,探究的分子筛合成条件又为分子筛的工业应用提供技术和理论支撑。

     

    Abstract: Coal fly ash is a large amount of industrial solid waste,which greatly harms the natural environment and human physical and mental health. How to use it efficiently and at a high value is a scientific and technical problem facing us.Volatile organic compouads are a type of volatile organic pollutants that have a "three effects" effect on the human body. Molecular sieve is widely used in many fields because of its unique pore structure,excellent ion exchange,catalysis and adsorption performance. The 13X zeolite was prepared by alkali fusion activation combined hydrothermal synthesis by the coal fly ash in the experiment. The factors of Si/Al ratio,alkalinity and crystallization time were analyzed in the preparation of 13X zeolite. The VOCs adsorption properties of 13X zeolite and activated carbon were investigated. XRD,SEM and BET are used to characterize the structure of molecular sieve crystal form,larger surface area and pore size. It was found that 13X zeolite is of good crystallinity and high purity by XRD,SEM,EDX and chemical composition analysis. The particle size ranges from 1 to 3 μm which is almost uniform. The BET specific surface area reaches 990.3 m2/g and the total pore volume is about 0.72 cm2/g. The average pore diameter is 1.1 nm. The type of zeolite was influenced by the Si/Al ratio. The crystallization rate is accelerated and the crystallization time is shortened by increasing the alkalinity,which promote the polycondensation reaction of silicate with aluminate ions. Zeolite are generated quickly during the crystallization stage. It was found that the VOCs adsorption capacity of 13X zeolite is higher than that of activated carbon. JP3The greater the polarity of VOCs molecules,the higher the adsorption capacity. Through the research in this paper,it not only achieves the purpose JP3of "treating waste with waste,turning waste into treasure" between solid waste and waste gas,but also provides ideas for low-cost and efficient synthesis of zeolite molecular sieve. At the same time,it improves the utilization of bulk solid waste,and explores the synthesis of molecular sieve. The conditions in turn provide technical and theoretical support for the industrial application of molecular sieves.

     

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