利用水合硅酸钠钙渣回收碱并用于制备硅灰石纳米粉体的实验研究

An Experimental Study on Preparation of Nanocrystalline Wollastonite Powders from Sodium-Calcium Siliceous Hydration Residue

从高硅含铝原料霓辉正长岩中提取氧化铝时,硅以水合硅酸钠钙的形式排出。实验研究了水合硅酸钠钙渣的高效利用技术。利用水合硅酸钠钙自身的水解作用和在NaOH溶液中使之分解两种方法来回收其中的Na2O,所得NaOH溶液经蒸发浓缩后可循环利用。回收碱后剩余的固体渣用来制备硅灰石粉体。实验得出回收碱的优化条件为温度180℃,起始溶液的Na2O浓度为20 g/L,液固比为4∶1,洗涤6~7次。在此条件下,碱回收率可达90%以上。对回收碱后所得固体渣进行差热-热重分析,确定制备硅灰石粉体的煅烧温度。在820℃下煅烧2 h,制得颗粒尺寸为50~100 nm的α-CaS iO3纳米粉体,对其反应机理进行了初步的探讨。

This study is focused on the efficient utilization technique of sodium-calcium siliceous hydration residue,which is remained after treating the high silicon aluminum-containing materials aegirine-augite syenite.The alkali of sodium-calcium siliceous hydration was recycled by its self-hydrolysis and decomposition in NaOH solution.The obtained diluted NaOH solution can be recycled after being concentrated.The influences of temperature,L/S ratio,initial Na2O concentration and washing times were experimentally investigated.The alkali recovery proportion is up to 90% at the conditions of 180 ℃,L/S ratio 4∶1,initial Na2O concentration 20 gram per litre and washing six to seven times.According to the differential thermal analysis and thermogravimetry of the solid residue remained after alkali recovery,the calcination temperature of preparing wollastonite is 820 ℃.Nano-crystalline wollastonite-2M was prepared,with particle size range from 50 to 100 nm,and its reaction mechanism was discussed.