从含碱硅酸钠溶液中水热合成硅灰石

以含碱硅酸钠溶液为原料,在常压下加入石灰乳,先水热合成CaO·SiO2·H2O,再将CaO·SiO2·H2O在850℃下焙烧2 h可制备硅灰石.研究了溶液中SiO2浓度、钙硅摩尔比(C/S)及反应时间对硅灰石合成的影响.热力学计算结果表明,常压下Na2O-CaO-SiO2-H2O体系中,最有可能形成CaO·SiO2·H2O及2CaO·SiO2·1.17H2O.实验结果表明:当C/S为1.0时,随着溶液中硅浓度的增加,硅酸根离子的聚合程度增加,有利于硅灰石的制备;随着时间的延长,硅灰石结晶程度越高;当C/S为0.6、0.8、1.0时,最终产物为CaSiO3;当C/S为1.5、2.0时,最终产物中含有大量的Ca2SiO4.适宜的水热合成条件为:SiO2浓度>30 g/L、C/S 0.6～1.0、温度98℃、反应时间>3 h.

Hydrothermal Synthesis of Wollastonite from Alkaline Sodium Silicate Solution

With alkaline sodium silicate solution used as raw material and lime milk been poured into at the atmospheric pressure , CaO · SiO2 · H2O was first obtained after hydrothermal treatment , and after calcinated for 2 h at 850 ℃, CaO · SiO2 · H2O was transformed to wollastonite .The effects of SiO 2 concentration , molar ratio of silicon to calcium ( C/S ) and the reaction time on synthesis of wollastonite were examined.The thermodynamics calculation results indicated that CaO · SiO2 · H2O and 2CaO· SiO2 · 1.17H2O were most likely formed in Na2O-CaO-SiO2-H2O system at atmospheric pressure .The experimental results reveal that:When C/S is 1.0, silicate anions polymerization degree increases with the increasing of the concentration of silicon in solution , which will be conducive to the preparation of wollastonite.With the extension of time, the wollastonite crystallinity is higher.When C/S is 0.6、0.8、1.0, the product is CaSiO3.When C/S is 1.5、2.0, a large number of Ca2SiO4 produced in the final product.The optimum condition for preparation of wollastonite is:SiO2 concentration is more than 30 g/L, the hydrothermal temperature is 98 ℃, C/S is 0.6-1.0 and the hydrothermal time is more than 3 h.