硅矿物在拜耳法溶出中的行为

Behavior of silicon minerals during Bayer digestion

研究了高岭石、伊利石、叶蜡石等几种单体硅矿物在铝酸钠溶液中的溶出行为。结果表明，高岭石、伊利石、叶蜡石等单体硅矿物在铝酸钠溶液中的溶出速率受温度等反应条件的影响。采用量子化学理论计算，用CASTEP程序模块，在GGA-PW91基组水平，对高岭石、伊利石、叶蜡石及其常见完全解理面（001）slab模型进行几何优化，揭示了高岭石、伊利石、叶蜡石在铝酸钠溶液中反应活性差异的微观本质。高岭石、伊利石和叶蜡石的反应活性存在较明显的不同，其中叶蜡石的反应活性最大。伊利石的Si—O键结合力最强，Al—O键结合力相对最弱，相对最难反应脱Si：叶蜡石Si—O键结合力相对最弱，相对较容易反应脱除Si。OH^-的存在对高岭石、伊利石、叶蜡石完全解理面的微观电子结构、Si—O键的结合力等均影响显著，其中OH^-对高岭石表面性质及Si-O键结合力的降低产生的影响最大，因此高岭石在相对较低温度下较易在碱性溶液中反应脱硅。

The digestion behaviors of several mono-silicon minerals including kaolinite, illite, pyrophyllite in aluminate solution were investigated. The results show that the digestion rate of kaolinite, illite and pyrophyllite in aluminate solution is influenced by reaction conditions such as temperature. By adopting quantum chemistry theoretical calculation, and using CASTEP procedure module, the slab model of kaolinite, illite, pyrophyllite and their ordinary complete cleavage plane （001） are geometry optimized at GGA-PW91 level. The micro-essence of the differenent reaction activity among kaolinite, illite and pyrophyllite in aluminate solution is opened out. The reaction activity of kaolinite, illite and pyrophyllite is obviously different and the reaction activity of pyrophyllite is the highest. The Si-O bond strength of illite is the strongest and its Al-O bond strength is comparatively the most weak, so its Si is the most difficult to remove. The Si-O bond strength of pyrophyllite is the most weak, so its Si is relatively easier to remove. The micro-electron structure of complete cleavage plane and the Si-O bond strength of kaolinite, illite and pyrophyllite are evidently influenced by the existence of OH^-, of which the surface character and the reduction of Si-O bond strength of kaolinite are influenced most by OH^-, therefore the desilication of kaolinite in alkaline solution at relatively lower temperature is easier.