微筛孔反应器液相沉淀法制备纳米CaCO_(3)

Preparation of Nano-CaCO_(3)by Liquid-Phase Precipitation in Micro-Sieve Reactor

采用微筛孔反应器,以Ca(NO_(3))_(2)·4H_(2)O为钙源连续相、(NH_(4))_(2)CO_(3)为碳源分散相,液相沉淀法制备纳米CaCO_(3)。利用XRD、TEM等表征手段分析研究分散相与连续相流量、浓度和停留时间等制备条件对碳酸钙的粒径、产率和形貌的影响。结果表明,使用微筛孔反应器通过液相沉淀法可制得平均粒径45~92 nm、产率达80%以上的方解石型纳米CaCO_(3)。适宜的制备条件为:连续相进料流量F_(C)=150 mL/min、分散相进料流量F_(D)=150 mL/min、连续相浓度[Ca^(2+)]=0.05 mol/L、分散相浓度[CO^(2-)_(3)]=0.2 mol/L、停留时间τ=5 s。微筛孔反应器特有的孔道结构能够均匀分散液相体系,从而避免了一般微反应器在液相沉淀反应中出现的堵塞问题,微筛孔反应器的分子扩散混合模式可大幅度强化液相体系的扰动程度并提高CaCO_(3)过饱和度,使制得样品粒径较小且分布极窄。同时,通过改变制备条件可灵活调控样品的形貌与粒径。

Nano-CaCO_(3)was prepared by liquid-phase precipitation using a micro-sieve reactor with Ca(NO_(3))_(2)·4H_(2)O as calcium source continuous phase and(NH_(4))_(2)CO_(3)as carbon source dispersed phase.The effects of the preparation conditions such as flow rate,concentration and residence time of the dispersed and continuous phases on the particle size,yield and morphology of calcium carbonate were investigated by XRD and TEM.The results show that the calcite nano-CaCO_(3)prepared by liquid-phase precipitation in micro-sieve reactor has an average particle size from 45 nm to 92 nm and a yield of more than 80%.The suitable preparation conditions are:continuous phase feed flow F_(C)=150 mL/min,dispersed phase feed flow F_(D)=150 mL/min,continuous phase concentration[Ca^(2+)]=0.05 mol/L,dispersed phase concentration[CO^(2-)_(3)]=0.2 mol/L and residence timeτ=5 s.The unique pore structure of the micro-sieve reactor can evenly disperse the liquid-phase system,thus avoiding the clogging problem occuring in liquid-phase precipitation reactions in general micro reactors.The molecular diffusion and mixing mode of the micro-sieve reactor could homogeneously enhance the perturbation of the liquid phase system and increase the supersaturation of CaCO_(3),leading to smaller particle size with a very narrow distribution.Meanwhile,the shape and size of the samples can be flexibly adjusted by changing the preparation conditions.