Abstract Mixed metal oxides (MMO) were transformed to phyllosilicate in the presence of silicate anions under hydrothermal conditions. The product was shown to be saponite with a trioctahedral layer structure by characterization with XRD, FTIR, 27 Al and 29 Si MAS NMR, HRTEM and TG-DTG. The formation of saponite was through a rehydration-dissolution-precipitation pathway, involving the critical steps such as the reconstruction of MMO to hydrotalcite (Ht), exsolution of Al 3+ from Ht, condensation of metasilicate anions with Ht, and finally crystallization of saponite. Isomorphous substitution of Al 3+ for Si 4+ in silicate oligomers is the key for the above conversion, which generated the negative charge necessary for the condensation between the silicate oligomers and Ht surface and the formation of 2:1 saponite TOT layers. High pH value (over 14.0) favored the condensation of silicate oligomers and led to crystallization of saponite. Thus, we report a novel method for the crystallization of saponite.

中文翻译：

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混合金属氧化物和硅酸盐阴离子在强碱性条件下水热转化为页硅酸盐

摘要 混合金属氧化物 (MMO) 在水热条件下在硅酸盐阴离子存在下转化为页硅酸盐。通过 XRD、FTIR、27 Al 和 29 Si MAS NMR、HRTEM 和 TG-DTG 表征，表明产物是具有三八面体层结构的皂石。皂石的形成是通过再水化-溶解-沉淀途径形成的，包括关键步骤，如MMO重构为水滑石（Ht）、Ht中Al 3+的溶出、偏硅酸阴离子与Ht的缩合，以及最终皂石的结晶. 硅酸盐低聚物中Al 3+ 对Si 4+ 的同晶取代是上述转化的关键，它产生了硅酸盐低聚物与Ht表面之间缩合以及形成2:1皂石TOT层所必需的负电荷。高pH值（超过14。0) 有利于硅酸盐低聚物的缩合并导致皂石结晶。因此，我们报告了一种新的皂石结晶方法。