合成皂石结构中Al的占位与制约机制

Saponite is a 2:1 type trioctahedral clay mineral. Due to higher acidity and thermal stability comparing with montmorillonite, saponite enjoys wider range of applications and higher economic value in industry. The structure and properties of saponite are closely related with the unequaivalent isomorphism in its structure. With the isomorphism of Al for Mg and Si atoms as breakthrough points, this proposal will take an investigation on the relationship and the constraints between the microstructure and the physicochemical properties of saponite synthesized with the different contents of Mg, Al and Si, systematically. By using micro-beam and micro-area analysis techniques, we also attempts to reveal the occupancy selectivity and constraints of the isomorphous substitution of Al3+, the influence and mechanism of the ratio of Al(IV)/Al(VI) on the crystallinity and the cation exchange capacity (CEC) of saponite, and the end members of Al3+→Mg2+ isomorphous series in smectites. The study will disclose the relationship between structure and physicochemical properties of clay minerals in atomic scales, make a contribution to the diversity of crystal chemistry, and provide a scientific guidance to the mineral resources utilization.

皂石是一类2:1型三八面体粘土矿物，具有比蒙脱石更高的酸性和热稳定性，因而具有更广泛的应用领域和更高的工业经济价值。皂石的结构和性质与其结构中不等价离子的类质同像置换有着密切关系。本项目拟以铝与硅、镁的类质同像置换为切入点，利用微区、微束等技术为主要手段，系统研究不同Si、Mg、Al摩尔比的合成皂石的微结构特征及其与皂石物理化学性质间的制约机制，揭示皂石合成过程中Al3+发生类质同像置换的占位选择性及其制约因素，阐明Al3+在四面体和八面体中的占位对皂石结晶度、阳离子交换容量（CEC）等的影响及其机制，确定蒙皂石族矿物结构中，八面体位置Al3+→Mg2+类质同像置换的端员组成。本项目将从原子尺度建立粘土矿物的结构与物理化学性质间的内在联系，丰富粘土矿物晶体化学理论，同时对粘土矿物的高效利用也有重要指导意义。

皂石是一类2:1型三八面体粘土矿物，具有比蒙脱石更高的酸性和热稳定性，因而具有更广泛的应用领域和更高的工业经济价值。皂石的结构和性质与其结构中不等价离子的类质同像置换有着密切关系。本项目以铝与硅、镁的类质同像置换为切入点，利用微区、微束等技术为主要手段，系统研究了Si、Mg、Al摩尔比对合成皂石的微结构特征及其与物理化学性质间的制约机制，揭示了：皂石合成过程中Al3+优先占据四面体位；皂石结晶度、阳离子交换容量（CEC）等理化性能受到Si/Al和AlIV/AlVI的制约。当Si/Al比介于5.43～7.89时，AlIV/AlVI比值最大，皂石结晶度最高，CEC值最大。确定蒙皂石族矿物结构中，八面体位置Al3+→Mg2+类质同像置换系列存在组分的不连续性。项目采用有机硅烷探针方法，在Si MAS NMR谱的–86.7 ppm处探测到一明显信号，归属于皂石端面断键产生的Q2信号与四面体网面中Q3信号的叠加。本项目的相关结论丰富了粘土矿物晶体化学理论，同时对粘土矿物的高效利用也有重要指导意义。