石灰石制备食品级球霰石碳酸钙微球及其机理研究

Preparation and Mechanism of Food-Grade Vaterite Calcium Carbonate by Limestone

以石灰石为原料,利用HNO3酸解和Ca(OH)_(2)沉淀除杂精制得到Ca(NO_(3))_(2)溶液,在氨氛围下采用CO_(2)碳化法制备食品级球霰石型碳酸钙。探讨了碳化工艺参数对碳酸钙晶型调控的影响,并利用扫描电子显微镜、X射线衍射仪以及傅里叶变换红外光谱仪对产物进行表征,提出了NH_(4)^(+)和NH_(2)COO^(-)共同作用调控球霰石晶型生成的机理。结果表明,氨氛围有助于球霰石的稳定成核。当NH_(3)·H_(2)O浓度为13%(质量分数)、CO_(2)流量为0.5 L/min、反应温度为25℃、反应时间为25 min时,制得2~5μm的单一相球霰石碳酸钙微球,产物的纯度达到99.5%(质量分数),质量符合《食品安全国家标准食品添加剂碳酸钙》要求。本研究可为石灰石的高值化利用和亚稳态球霰石型碳酸钙的制备提供理论基础。

Limestone was used as raw materials,Ca(NO_(3))_(2) solution was obtained by HNO_(3) acid hydrolysis and Ca(OH)_(2) precipitation purification,and food-grade vaterite calcium carbonate was prepared by CO_(2) carbonization in the ammonia atmosphere.The effects of carbonization process parameters on the regulation of calcium carbonate crystal form were discussed,and the products were characterized by scanning electron microscopy,X-ray powder diffractometer and Fourier transform infrared spectroscopy.The mechanism of NH_(4)^(+) and NH_(2) COO-co-regulating the formation of vaterite crystal form was proposed.The results show that the ammonia atmosphere is helpful to the stable nucleation of vaterite-type calcium carbonate.When the concentration of NH_(3)·H_(2)O is 13%(mass fraction),the flow rate of CO_(2) is 0.5 L/min,the reaction temperature is 25℃,and the reaction time is 25 min,the single phase vaterite calcium carbonate microspheres of 2~5μm are prepared.The purity of the product is 99.5%(mass fraction),and the quality meets the requirements of food safety national standard food additive calcium carbonate.The research provides a theoretical basis for the high-value utilization of limestone and the preparation of metastable vaterite calcium carbonate.