硅藻土的^(29)Si魔角旋转核磁共振谱研究

^(29)Si MAS NMR SPECTROSCOPIC STUDY OF DIATOMITE

对广东、浙江、云南等不同矿床硅藻土的29SiMASNMR谱进行了讨论，谱上出现了几个不同化学位移及不同强度的信号，分别为-110．1×10－6～－112．1×10－6,-91．1×10－6～－91.6×10－6.－106．2×10-6～-107．1×10－6，－100×10－6～-102．5×10－6。这些信号分别届于硅藻硅质骨架、高岭石和石英的29Si共振。硅藻的硅质骨架与蛋白石的结构相类似，以Q4St环境为主，伴有少量Q6St环境．为非晶质的SiO2。硅质骨架的热稳定性：Q3Si在900℃以下稳定，900℃以上则转变为Q4Si结构；Q4Si在1200℃以下为非晶质．到1200℃转变为方英石。

Discussed in this paper are the 29Si MAS NMR spectra of diatomites in different diatomite deposits of Guangdong, Zhejiang and Yunnan provinces. The spectra show several signals with different chemical shifts at - 110. 1 × 10-6 to 112. 1×10-6. - 91.1×10-6t0 -91. 6 ×10-6,- 106. 2 × 10-6 to - 107. 1 ×10-6, - 100 × 10-6 to - 102. 5 × 10-6 and intensities. These signals belong t0 29Si resonance of siliceous shell of diatoms, kaolinite and quartz. The Q4Si structural environment is dominant, followed by Q3Si structural environment in the siliceous shell, similar to opal in structure. The thermal stability of the siliceous shell includes both Q3Si unit that is stable below 900℃ and is transformed into Q4Si unit above 900℃ and Q4Si unit that occurs as being amorphous below 1 200℃ and is transformed into α-cristobalite near 1 200℃ The transition metal ions(mainly Fe3+ ) exist mostly in clay minerals.