Cr(III) exchange on zeolites obtained from kaolin and natural mordenite
Cr(III) exchange on zeolites obtained from kaolin and natural mordenite
复制标题
DOI：
10.1016/j.micromeso.2005.09.007
复制
发表时间：
2006-01
影响因子：
5.2
通讯作者：
Cristian Covarrubias;Rafael García;R. Arriagada;J. Yáñez;M. Garland
中科院分区：
文献类型：
--
作者：
Cristian Covarrubias;Rafael García;R. Arriagada;J. Yáñez;M. Garland
以高岭土和天然丝光沸石为原料合成了高Cr（III）交换容量的沸石。采用X射线衍射、红外光谱、扫描电镜、热重分析、N2吸附和铬交换容量（CrEC）对中间相和最终产物进行了表征。此外，使用基于Rietveld精修的TOPAS程序鉴定精确的沸石相。由高岭土水热合成导致形成沸石-X和A的混合物。在较高的水热处理时间，沸石-X（空间群Fd-3）出现为主导相。在由天然丝光沸石合成中，形成沸石-Y（Fd-3 m）和正交沸石-P2（Pnma 62）的混合物，随着反应时间的增加，获得更纯的沸石-P。在两个系统中的结晶/转化过程中的差异被解释为在碱性介质中的起始材料的溶解速率的差异。合成产物的CrEC取决于沸石的类型和固体产物中无定形相的分数。发现含FAU型沸石的合成产物获得最高的CrEC。FAU分子筛具有较大的孔径，有利于大分子水合铬离子扩散到内部阳离子交换位，有利于铬离子的交换。合成的沸石产品呈现出比商业沸石更高的Cr（III）交换容量。这些结果表明，使用这些合成的材料在Cr（III）从工业废水中去除可能是有前途的。
Zeolites with high Cr(III) exchange capacity were synthesized from kaolin and natural mordenite. The intermediate phases and final products were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, thermogravimetric analysis, N2-adsorption and chromium exchange capacity (CrEC). In addition, precise zeolitic phases were identified using the TOPAS program based on Rietveld refinement. Hydrothermal synthesis from kaolin leads to the formation of a mixture of zeolites-X and A. At higher hydrothermal treatment period, zeolite-X (space group Fd-3) appears as the dominant phase. In the synthesis from natural mordenite a mixture of zeolite-Y (Fd-3m) and orthorhombic zeolite-P2 (Pnma 62) is formed, obtaining a more pure zeolite-P with the increase in reaction time. The differences in the course of the crystallization/transformation process in both systems are explained in terms of the differences in the dissolution rate of the starting materials in alkaline medium. The CrEC of synthesis products was determined by the type of zeolite and the fraction of amorphous phase in the solid product. It was found that the highest CrEC is obtained for synthesis products containing FAU-type zeolites. The chromium exchange on FAU zeolites is favored due to the larger pore opening, which facilitates the diffusion of large hydrated chromium ions into the internal cation exchange sites. Synthesized zeolite products presented higher Cr(III) exchange capacity than commercial zeolites. These results suggest that the use of these synthesized materials in Cr(III) removal from industrial wastewater could be promising.