过饱和铝酸钠溶液的分解机制

Decomposition mechanism of supersaturated sodium aluminate solution

将高过饱和度的铝酸钠溶液进行水解，并将水解产物快速干燥后进行红外（IR）、X射线衍射、^27Al魔角旋转．核磁共振（^27Al MAS-NMR）研究。实验发现，高过饱和度的铝酸钠溶液在一定条件下迅速水解得到白色固体。IR及XRD谱显示，水解产物的主要成分为α-Al（OH）3，并有少量杂相存在。^27Al MAS-NMR分析结果表明，固体中的Al全部为六配位体，杂相中不包含未转化的四面体或其它过渡态中间体。实验结果表明，氢氧化铝结晶过程中，铝酸根离子的分解所伴随的构型转化可能是在溶液中而不是在固相中完成的。

High supersaturated sodium aluminate solution was hydrolyzed, and the product of hydrolysis was characterized with IR, XRD and ^27Al MAS-NMR, respectively. The results show that high supersaturated sodium aluminate solution is rapidly hydrolyzed into a white sedimentation under certain condition. The spectra of IR and XRD indicate that the main component of sedimentation is α-Al（OH）3, accompanied with minor impurity phase. Further investigation of the sedimentation with ^27Al MAS-NMR suggests that all Al atoms are hexacoordinated, and no tetracoordinate Al or intermediate is detected. It is proposed that the inversion of aluminate ion is completed in solution instead of solid phase.