层状硅酸盐矿物的结构及其振动光谱特征
【试验研究】
层状硅酸盐矿物的
结构及其振动光谱特征
张姝婧，德吉卓嘎，覃 欢，刘 邯，洛桑旦增，程宏飞
(中国矿业大学(北京)地球科学与测绘工程学院，北京 100083)
【摘 要】采用近红外分析仪对层状硅酸盐矿物进行分析测试，获取了六种层状硅酸盐矿物的近红外光谱图，根据结构矿物学和近红外光谱的原理，对具有代表性的属2∶1型结构单元的滑石、叶蜡石、白云母、伊利石以及属1∶1型结构单元的高岭石和蛇纹石进行了结构与近红外光谱特征的对比分析，1∶1型结构的层状硅酸盐由于在两单元层之间有一个较长的氢键，氢键使O-H的伸缩振动谱带变宽，谱带向长波的方向移动，有时还会出现双峰现象。另外，二八面体结构和三八面体结构的层状硅酸盐矿物相比，二八面体结构的层状硅酸盐中O-H的伸缩频率导致吸收强度更大。对于同为二八面体结构的层状硅酸盐矿物，氢氧根伸缩的频率主要受到与氢氧根配位的八面体阳离子影响。
【关键词】层状硅酸盐；结构；近红外光谱
【中图分类号】TQ170.11 【文献标识码】A 【文章编号】1007-9386(2018)02-0001-07
The Structure of Layered Silicate Mineral and
Their Vibrational Spectra Characteristics
ZHANG Shu-jing, DEJI Zhuo-ga, QIN Huan, LIU Han, LUOSANG Dan-zeng, CHENG Hong-fei
(China University of Mining and Technology (Beijing), College of Geoscience and Surveying Engineering, Beijing 100083, China)
Abstract: Using near-infrared analyzer to test layered silicate minerals, accessing to six kinds of near-infrared spectra of layered silicate minerals, according to the principle of the structural mineralogy and the principle of near-infrared spectrum, analyzing representative layered silicate minerals with 2:1 type structure unit such as talc, pyrophyllite, muscovite, illite and representative layered silicate minerals with 1:1 type structure unit such as kaolinite and serpentine, 1:1 type structure of layered silicate as between two cell layers has a longer hydrogen bond, the longer hydrogen bond widen the stretching vibration spectrum band of O-H and also move it to the direction of the long wave band, sometimes could appear bimodal phenomenon. In addition, comparing layered silicate minerals having dioctahedral structure with layered silicate minerals having trioctahedral structure, the absorption intensity which is caused by the stretching vibration frequency of O-H is stronger in layered silicate minerals having dioctahedral structure. As for layered silicate minerals with dioctahedral structure, the stretching vibration frequency of O-H is mainly affected by the cations combining with hydroxyl in octahedra.
Key words: layered silicate; structure; near-infrared spectra
1 引言
国内近红外光谱法的研究与应用犹如雨后春笋，在农业、食品、制药、石化和烟草等领域的质检质控中发挥了积极的作用[1]。近红外光谱技术也已被应用于地质中的矿物鉴定、矿物的定性定量分析等，深受广大研究者重视，不仅是由于这种光谱技术可靠，而且还因为其有着用样少、分析快捷和操作简单等优点[2]。
近红外光谱(NIRS)属于分子振动光谱，所测的特性为分子振动基频尤其是伸缩和弯曲(也包括部分变形)振动的倍频和组合频的吸收带[3]。用红外光对样品进行扫描时，当样品成分的某些分子振动频率与入射
光中某些波长的频率相同时发生共振吸收(或量子跃迁)，从而在对应波谱区形成特征吸收峰。其中特征吸收的波长位置即吸收峰横坐标位置，它取决于样品中吸光分子振动的特征频率；吸收光谱中吸收强度即吸收峰纵坐标的高度，它取决于样品中相关吸光分子的数量即样品的浓度[3]。近红外光谱区的波长范围是770～2500nm，短波近红外谱区(770～1100nm)主要承载的是三、四、五倍频，即高倍频信息；中波近红外谱区(1100～1600nm)主要承载的是二倍频的信息；长波近红外谱区(1600～2500nm)主要承载的【基金项目】中国矿业大学(北京)大学生创新计划资助(编号：C201602030)。
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