摘要
本文对煅烧高岭土改性前后样品进行了２９Ｓｉ和２７Ａｌ旋转魔角核磁共振（ＭＡＳＮＭＲ）对比研究。实验结果表明，２９Ｓｉ的－１０６×１０－６峰化学位移几乎没有变化，２７Ａｌ化学位移值变化较大。改性前２７Ａｌ化学位移位于５．４４×１０－６和６５．６９×１０－６处，改性后朝低场方向移动，分别移至３．８×１０－６～４．４×１０－６和５４．６×１０－６～５９．９×１０－６范围内。这说明煅烧高岭土的表面化学改性主要是通过与其表面的Ａｌ离子结合完成的。
The surface modification of minerals has been studied by infrared spectrum (IR) before. It is usually suggested that surface modification is completed if the organic group absorption, such as -CH 2 or -CH 3, appears in the IR spectrum of modified samples. Nevertheless, this method only tells us that the coupling agent exist in the samples, but fails to tell us whether the coupling agent molecules are really linked to the ions on the surface of the minerals or not. This paper tries to study the surface modification of fired kaolin by using MAS NMR on the basis of the following consideration: if the ions on the surface of minerals are linked with the coupling agent molecules, it can result in the change of such chemical environments around the ions as charge density, which can be detected by MAS NMR technique. The sample from the tonsteins in the coal_bearing strata where the kaolinite content is up to 90% is ground to 1250 mesh and fired in an oven at 950℃ for 12 hours. The fired kaolin is modified by silane coupling agent under a certain program. The comparative study on the 29 Si and 27 Al MAS NMR of modified and unmodified fired kaolin shows that the chemical shift of -106×10 -6 of 29 Si is unchanged between modified and unmodified samples, but 27 Al changes obviously. The chemical shift of 5.44×10 -6 and 65.69×10 -6 of 27 Al in unmodified samples are separately shifted to 3.8×10 -6 ～ 4.4×10 -6 and 54.6×10 -6 ～59.9×10 -6 after modification. This result shows that the modification is completed by linking Al on the surface of fired kaolin with the silane coupling agent molecules.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
1998年第3期266-269,274,共5页
Acta Petrologica et Mineralogica
基金
煤炭部一般项目基金
