PDF《Al 魔角旋转核磁共振研究热处理凹凸棒石结构中 Al 配位变化》

郑权男 等:硅藻土中伴生有机质的炭化与吸附性能 ・

235 ・ 第41 卷第

2 期DOI:10.

7521/j.issn.0454C5648.2013.02.18

27 Al 魔角旋转核磁共振研究热处理凹凸棒石结构中 Al 配位变化 谢晶晶,陈天虎,陈冬,刘海波,孔德军,邢波波 (合肥工业大学资源与环境工程学院,合肥 230009) 摘要:热处理是凹凸棒石黏土活化改性的常用方法之一.认识热处理过程中凹凸棒石结构演化,特别是凹凸棒石结构中铝配位的变化规律,对于理 解凹凸棒石热活化改性的本质是十分重要的,可以为凹凸棒石黏土热化处理提供理论依据.为此,利用

27 Al 魔角旋转核磁共振(MAS-NMR)技术结合 X 射线衍射分析,研究了经 250~900 ℃热处理的凹凸棒石结构铝配位的变化.结果表明:天然凹凸棒石中铝主要是

6 配位(铝替代八面体中的镁), 有很少量的

4 配位铝存在(铝替代硅氧四面体中的硅位置),并且在凹凸棒石硅氧四面体的四重周期中存在

2 个不同的晶格位置;

煅烧温度在

500 ℃以 下时,铝配位没有发生明显变化;

煅烧温度升高到

500 ℃以上时,4 配位铝明显增加,并且存在两种不同的晶格位置,表明结构有序性并没有完全破 坏,同时还出现了少量的

5 配位铝.经600 ℃热处理后,凹凸棒石中铝

6 配位急剧降低,基本转化为

4 配位;

温度升高到

800 ℃时,6 配位以及作为 中间态出现的

5 铝配位完全消失,并且

4 配位铝峰只有一个峰,表明经过

800 ℃高温处理后

4 配位铝都处于相同的化学环境. 关键词:凹凸棒石;

铝配位;

核磁共振;

热处理;

结构 中图分类号:O76 文献标志码:A 文章编号:0454C5648(2013)02C0235C05 网络出版时间:2013C01C25 网络出版地址:http://www.cnki.net/kcms/detail/11.2310.TQ.20130125.1706.201302.235_018.html Study of Al Coordination Structure Change in Palygorskite via

27 Al MAS NMR Analysis XIE Jingjing,CHEN Tianhu,CHEN Dong,LIU Haibo,KONG Dejun,XING Bobo (School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China) Abstract: Thermal treatment is a common method to active palygorskite. It is thus important to investigate the effect of thermal treatment on palygorskite'

s structural properties, especially on the Al coordination. The coordination structure transformation of Al in the thermally-treated palygorskite samples from

250 to

900 ℃ ℃ was investigated by

27 Al magic-angle spinning nuclear magnetic resonance (MAS-NMR). The results show that Al in untreated palygorskite is chiefly Al(Ⅵ), which subsititutes Mg in octahedral, along with a minor amount of Al(Ⅳ), which subsititutes Si in tetrahedral. There exist two different lattice positions in SiCO tetrahe- dral. No significant change appears when treated at the treatment temperature of <

500 . The peak of Al( ℃ Ⅳ) is strengthened and a signal of Al(Ⅴ) is detected when treated at >

500 ℃. There are two lattice positions existed at the same time, showing that the orderly structure is not destroyed compeletly. The peak of Al(Ⅵ) decreases and Al appears as Al(Ⅳ) after treated at >

600 . ℃ At

800 , Al( ℃ Ⅵ) and Al(Ⅴ) disappear completely, and the peaks of Al(Ⅳ) turn to form one peak, indicating that all the Al(Ⅳ) exists in one chemical environment. Key words: palygorskite;

aluminum coordination;

nuclear magnetic resonance;

thermal treatment;

structural