纳米CaCO_3合成及原位改性的研究

Investigation of Synthesis and in-situ Modification of Nano-sized Calcium Carbonate

在旋转填充床反应器中合成了纳米CaCO3悬浮液,利用pH计跟踪Ca(OH)2碳化反应过程, 研究了碳化反应过程原理。结果表明:旋转填充床能极大地强化相间传质与微观混合,提高体系中CaCO3的过饱和度,增大其成核及生长速率。加入适当的添加剂对纳米CaCO3进行原位改性; 利用TEM照片研究了原位改性过程中纳米CaCO3的成核生长机理,并考察了添加剂的作用机理。

The nano-sized CaCO3 dispersion is formed in the rotating packed-bed reactor (RPBR). The mechanism of carbonation reaction of Ca(OH)2 slurry with CO2 is studied by tracking the carbonation process with pH meter. The result indicates that RPBR can greatly intensify the process in terms of mass transfer and micromixing, generate the higher super-saturation of the system and increase significantly the nucleation rate and growth rate of CaCO3. In-situ modification of CaCO3 is carried out with suitable additive. The mechanism of the nucleation and growth of CaCO3 nano-particles during the in-situ modification process is studied by means of TEM, and the effect of the additive is discussed. The result shows that wirelike substance is generated in the process of nucleation of CaCO3 particles, then the wire gets thick, at last the wire breaks off and turns into CaCO3 nano-particles. Cubic CaCO3 nano-particles with the size of 30nm are formed if no additive is added into the system. When additive A is added into Ca(OH)2 slurry before CO2 is blowed, the anions dissociated from additive A will absorb on the surface of CaCO3 nucleus, and inhibit the growth of the nucleus, as a result catenarian CaCO3 nano-particles with the size of 30nm120nm are formed.