【作者】 程珍；

【导师】 宁桂玲；

【作者基本信息】 大连理工大学 ， 化学工艺， 2012， 硕士

【摘要】 我国是镁资源大国,储量居世界第一位,其中水镁石探明储量已超过2000万吨。目前我国水镁石的开发利用还处于原矿的出口及烟气脱硫等低附加值产品的初级阶段。纳米氢氧化镁由于其特有的光学性质、电磁性质、化学催化性等优异特性,引起人们的高度关注。从提高水镁石矿综合利用率的角度出发,本课题组开发出有机分子诱导水镁石转晶制备氢氧化镁纳米晶的新技术。在对甲苯磺酸和氨基酸这两类有机物的诱导作用下,水镁石颗粒越过固→固尺寸效应的阈值一步转变为纳米氢氧化镁。与传统方法相比,此过程无需酸解液、沉淀剂,无副产物。本论文选择有机酸及有机胺两类有机分子作诱导剂,探索水镁石转晶的规律及机理,为其它难溶矿物的诱导转晶提供研究思路及途径。本文主要研究内容和结果如下：(1)水镁石的有机酸类诱导转晶及规律探索。通过选择不同结构的有机酸进行水热反应,并对产物进行SEM、TEM、XRD、FT-IR、TG/TGA等表征。研究结果表明,带苯环的有机酸能够实现水镁石的诱导转晶,而稠环酸及链状酸未能实现转晶；有机分子并未进入最终的产品。对水镁石转晶的规律进行研究发现,随着有机酸的酸度增大,其转晶作用增强；控制适宜的反应温度及有机物添加量有利于得到良好的转晶产品。(2)水镁石的有机胺类诱导转晶及规律研究。通过选择不同结构的有机胺类进行转晶反应,并对产物进行SEM、TEM、XRD、FT-IR、TG/TGA等表征。研究发现具有相邻氮配位点的有机胺类其转晶效果最佳；有机胺并未进入最终产品。调节适宜的反应温度及有机胺添加量有利于达到良好的转晶效果。(3)诱导转晶机理研究。通过跟踪转晶反应中间过程并结合反应规律,针对这两类有机分子提出了不同的转晶机理。酸类诱导转晶得以实现的关键在于有机酸根能够插入水镁石层间与OH-进行离子交换,因此要求有机酸具有较强的酸度并满足一定的结构要求。该过程是可逆的,转晶后的母液可以回收利用。胺类诱导转晶是基于有机胺中N与Mg2+的配位作用,因此有机胺的诱导转晶效果取决于分子结构。(4)纳米氢氧化镁杂质分析。通过ICP对转晶后所得纳米氢氧化镁进行分析,发现产品纯度有一定提高。其中采用有机酸诱导法铁杂质含量降低了91%,有机胺诱导法铁杂质含量降低了76%,其可能原因是有机酸的离子交换作用相对于有机胺的配位作用具有较强的选择性。更多还原

【Abstract】 The magnesium resource is quite abundant in China. Brucite is a kind of mineral with the highest content of magnesium, and the reserve has been proved more than20million. However, the application of brucite is in the initial stage of development in our country. It is mainly used for export and low-value-added productions such as flue gas desulfurization. Thus, it is of great significance to research how to employ it to produce and process high-value-added and high-tech functional materials. Nano-structured magnesium hydroxide is a sort of fine and high-functional inorganic material. Great importance has been attached to it owing to its excellent characteristics such as optical properties, electromagnetic properties. From the point of comprehensive utilization, our group has developed a new technology to synthesize magnesium hydroxide nano-crystals, based on trans-crystallization of brucite directed by organic molecules. Superior to the traditional methods, our approach uses no acid or precipitant and no by-product resulting.p-toluenesulfonic acid and amino acid were applied as directing agents in our preliminary work. Direct transformation from irregular brucite to uniform magnesium hydroxide nanoplates was achieved in one step. On the basis, this paper selected organic acid and amine as directing agents. Research on the rule of brucite trans-crystallization was done in the aim of clarifying the control mechanism of organic molecules over brucite. The main contents and results are as follows:(1) Trans-crystallization of brucite with the aid of organic acid. Organic acids with different structures were employed in the hydrothermal process for the sake of exploring the discipline. It is found that the acid with phenyl could direct the transformation, while acid with naphthalene and chain organic acid have no effect. The solid product was analyzed by X-ray diffraction (XRD), infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TG/TGA). It is revealed that organic acid does not enter the final product. The law of transformation was investigated with the aid of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that trans-crystallization results are enhanced with the increase of acidity of organic acid.(2) Trans-crystallization of brucite in the presence of organic amine. Various kinds of amine with different structures were employed as directing agents with the aim of rule research. XRD, SEM, TEM, TG/TGA, FT-IR were used to analyze the product. As is indicated, amine with adjacent nitrogen displays best trans-crystallization effect. And organic amine did not combine into the final product through the above characterization. Control over reaction temperature and additive amount of organic amine are conductive to the realization of trans-crystallization.(3) Mechanism research. For organic acid, the key point lies on insertion of organic acid into brucite, and ion exchange process between organic acid and OH". Thus, those acids with stronger acidity present high transformation efficiency. The process is reversible, and mother liquor can be reused to trans-crystallization. For organic amine, the reason is attributed to the coordination between organic amine and Mg2+. As a result, amine with chelating binding sides presents higher transformation efficiency for a flexible chelating ligand generating.(4) Purity test of magnesium hydroxide nanoplates. Fe content of samples were analyzed by inductively coupled plasma emission spectral (ICP). It is revealed that purity is improved after the transformation process. For product induced by organic acid. Fe reduce91%. For organic amine, Fe reduce76%. The possible cause may be owing to the higher selectivity for ion exchange than coordination.更多还原