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Alternative TitleResearch on Hydrothermal Synthesis of Nano-layered Materials from Coal Series Kaolin
Thesis Advisor卢旭晨
Degree Grantor中国科学院研究生院
Degree Discipline材料工程
Keyword煤系高岭土   铵伊利石   白云母   纳米片状材料   重金属离子吸附
Abstract本文以煅烧煤系高岭土为原料,通过水热合成的方式制备了纳米片状铵伊利石和白云母,并对合成的纳米片状材料进行了系统的表征,探究了煅烧煤系高岭土向纳米片状铵伊利石和白云母的转变机理,探索了合成的纳米片状材料在重金属离子吸附方面的性能。本文通过对煤系高岭土的煅烧活化,提高了煤系高岭土向铵伊利石和白云母转变的反应速率,并且在煅烧过程中除去了灰黑色的有机杂质。煤系高岭土适宜的煅烧温度为650~800 °C,在此温度下煅烧的煤系高岭土在水热反应时反应速率相对较高,且合成的产物有良好的纳米片状形貌。反应温度显著影响煅烧煤系高岭土向铵伊利石转变的反应速率。当反应温度为200 °C时,反应3天煅烧煤系高岭土仍未全部转化为铵伊利石。反应温度增加到280 °C,仅需3 h就能得到形貌良好的纳米片状铵伊利石。煅烧煤系高岭土向铵伊利石、白云母的转变过程符合溶解结晶机理。反应过程中,煅烧煤系高岭土先溶解到溶液中,然后铵伊利石或白云母直接从溶液中生成,反应过程中不产生其他中间相。通过对合成的纳米片状铵伊利石和白云母结构和形貌的表征,发现合成的纳米片状材料呈花状团聚结构,纳米片之间通过面-端结合方式相互连接。合成的纳米片状铵伊利石的比表面积可达197 m2/g,合成的纳米片状白云母的比表面积可达155 m2/g,两种纳米片状材料的比表面积相对于天然高岭土和剥片高岭土均有大幅提升。合成的纳米片状白云母含有孔径约为2~4 nm的堆积介孔,孔容约为0.91 cm3/g。合成的纳米片状铵伊利石和白云母对重金属离子有良好的吸附能力。合成的纳米片状铵伊利石对Cr6+和Cd2+等重金属离子的吸附量分别可达15.76 mg/g和14.86 mg/g,合成的纳米片状白云母对Cr6+和Cd2+的吸附量分别可达12.96 mg/g和11.36 mg/g,两种合成的纳米片状材料对Cr6+和Cd2+的吸附量比煤系高岭土、煅烧煤系高岭土及报道的纳米片状γ-Al2O3、花状Y2O3等其他纳米结构材料对Cr6+和Cd2+的吸附量均要大,可能与本研究中合成的纳米片状材料比表面积大且表面含有固定负电荷有关。
Other AbstractNano-layered amonium illite and muscovite were prepared from coal series kaolin by the hydrothermal method consisting of calcination, homogenizing with ball-milling and hydrothermal treatment. The crytal structure, morphology, specific area, pore distribution and the performance on heavy metal ions adsorption of synthetic nano-layered materials were systematically investigated. The formation mchanism of ammonium illite and muscovite from coal series kaolin was discussed as well. Calcination was used to activate coal series kaolin and remove the grey black orginaic impurity. The proper calcinatin temperature is in the range of 650~800 °C. After calcination at the temperature in this range, the reaction rate of metakaolin was improve and the products have very well nano-layered morphology. But when coal series kaolin was calcined at 1000 °C, calcined coal series kaolin will not be transformed to ammonium illite or muscivite at all. Reaction temperature influenced greatly on the raction rate of calcined coal series kaolin to ammonium illite. When metakaolin was reacted at 200 °C and 2.0 Mpa for 3 d, metakaolin will not be totally transformed to ammonium illite . While at 280 °C, ammonium illite with great well caystallinity could be obtained in only 3 hours. The results show that the transformation mechnism of metakaolin to ammonium illite and muscovite follows the dissolution-precipitation. Metakaolin was first dissolved into the medium and then ammonium illite and muscovite directly precipitate from medium without the formation of other intermediate phases. The morphology shows that synthetic ammonium illite and muscovite nanosheets aggregated to larger particles though face-to-edge manner and formed the flower-like structure. The specific surface area of synthetic nano-layered ammonium illite is up to 197 m2/g, and synthetic nano-layered muscovite up to 155 m2/g, which are a greate advance of both natual kaolin and exfoliated kaolin. Sythetic nano-layered muscovite has the mesopores with the width of ca. 2~4 nm and pore volume of ca. 0.91 cm3/g. Synthetic nano-layered ammonium illite and muscovite show great performance on the adsorption of heavy metal ions such as Cr6+、Cd2+、Pb2+、Cu2+. Due to the high specific area and negative charged surface of synthetic materials, both ammonium illite and muscovite show great adsorption capacities of removal of Cr6+ and Cd2+from water. The adsorption capacities of ammonium illite and muscovite are greater than coal series kaolin, calcined coal series kaolin and other reported synthetic nanomterials such as γ-Al2O3 nanosheets and flower-like Y2O3.
Document Type学位论文
Recommended Citation
GB/T 7714
王赟. 基于煤系高岭土水热法合成纳米片状材料的研究[D]. 中国科学院研究生院,2013.
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