多孔三水碳酸镁晶体可控制备及其孔结构构筑机理研究

Porous nesquehonite crystals has been one of the most prospective inorganic functional materials. However, up to now, there are no studies on it for technique hindrance. The process taking magnesite as magnesium source to obtain magnesium carbonate possess the advantages of cheap in the raw materials. But in the traditional methods, magnesite is treated by acid leaching, high temperature calcination and digestion. There are still some problems including waste of resources, environmental pollution and worse economy. In this project, porous nesquehonite crystals will be prepared by the methods of ions catalyzed phase conversion of the magnesite, carbonization and bubbles templates. The kinetics of ions catalyzed phase transformation of the magnesite will be explored, as well as the mechanism. Thus, the phase inversion process will be optimized. Furthermore, the formation and stability of bubbles in solution will be analyzed, a stable existence model of bubbles will be constructed, and the nucleation and growth mechanism of crystals under the control of bubbles will be deeply researched. This project will set up the association model between the porous morphologies and induction process of the bubbles templates, emphatically reveal the bubbles templates induced mechanism of the porous morphology formation, and elucidate the chemical crystallization mechanism of porous nequehonite. Eventually, it can realize the controlled fabrication of porous nesquehonite crystals. The research results are expected to break the conventional morphologies of nesquehonite crystals, and break through bottlenecks that the solid magnesium carbonate in magnesite can not be directly converted into magnesium hydroxide. This has great significance for enriching the research theory of porous materials and accelerating the high quality, high efficiency and energy saving utilization process of magnesite resources in China.

多孔三水碳酸镁晶体是一种极具发展前景的无机功能材料，而目前国内外关于它的研究尚属空白。以菱镁矿为镁源制备碳酸镁系化合物，具有原料廉价易得的优点，但传统制备方法需要酸浸或高温煅烧消化处理，存在资源浪费、环境污染、经济性较差等不足。本项目采用离子催化菱镁矿相转化-碳化法并结合气泡模板法制备多孔三水碳酸镁晶体。研究离子催化菱镁矿相转化反应动力学，揭示离子催化相转化机制，获得最佳相转化工艺；研究气泡的稳定性，构建气泡稳定存在模型，深入探究气泡模板调控下晶体成核和生长机理，建立多孔结构构筑与气泡模板诱导过程的关联模型，重点揭示孔结构构筑的气泡模板诱导机理，阐明多孔形貌三水碳酸镁化学结晶机制，实现多孔三水碳酸镁晶体的可控制备。研究成果有望打破三水碳酸镁的常规形貌，突破菱镁矿中固相碳酸镁不能直接转化为氢氧化镁的技术瓶颈，对于丰富多孔材料的基础研究理论以及促进我国菱镁矿资源高质高效节能利用具有重要意义。

多孔三水碳酸镁晶体因其独特的多孔结构、大比表面积、丰富的吸附活性等特点而成为一种极具发展前景的无机功能材料，但目前国内外关于它的研究尚属空白。本项目以菱镁矿为原料，采用离子催化相转化法制备多孔三水碳酸镁晶体，研究了离子催化菱镁矿相转化工艺及其机理，低受限度体系下三水碳酸镁晶体制备工艺，在此基础上研究了结构导向剂调控下多孔三水碳酸镁晶体制备技术、晶体成核和生长机理、孔结构构筑机理，确定了可控制备工艺。.通过本项目研究，获得了以MgCl2为催化剂的离子催化菱镁矿相转化工艺，将固相碳酸镁直接转化成固相氢氧化镁，揭示了MgCl2催化固相转化过程中反应速率前期受化学反应控制、后期受菱镁矿表面解吸速率控制；获得了低受限度体系下三水碳酸镁晶体适宜制备工艺，优选出葡聚糖为多孔球构筑的适宜结构导向剂，阐明了三水碳酸镁晶体结晶机制，揭示了多孔结构构筑机理。三水碳酸镁晶体生长基元为[MgO6]正八面体，Mg-O键以共顶点的方式连接，[MgO6]正八面体沿[010]方向无限连接形成长链。棒状三水碳酸镁晶体形成机制为螺型位错生长机理。葡聚糖在多孔球状三水碳酸镁晶体孔结构构筑过程中起到类似限域模板作用，其分子链上的羟基与镁离子通过静电匹配形成配位离子MgOH+，配位离子和碳酸盐形成规则的[MgO6]八面体生长基元，通过协同和加和作用形成纳米片；纳米片在交联网络结构上聚集、叠合，堆叠的纳米片通过外延生长形成多孔三水碳酸镁微球。根据多孔三水碳酸镁晶体生长模型，纳米片通过“间距成核”以及纳米片之间的“回转运动”构筑形成多孔结构。.本项目从理论上弄清了离子催化菱镁矿相转化机制，突破了菱镁矿中固相碳酸镁不能直接转化为氢氧化镁的技术瓶颈，制备了比表面积大的多孔球状三水碳酸镁晶体，打破了三水碳酸镁的常规形貌，所获得专利技术为其产业化和具体应用提供了技术条件，为我国菱镁矿资源高质高效节能利用以及多孔材料产业化应用奠定了良好的技术理论基础。