高炉渣同时制备类水滑石和沸石过程机理及其微量元素行为研究

In order to derive high added-value products based on blast furnace slag (BFS), a novel method regarding the synthesis of hydrotalcite-like compounds (HTLcs) together with zeolite was successfully established in this project. Considering the prerequisite for the obtainment of HTLcs that the molar ratio of divalent cation to trivalent cation in should be in the range of 2 to 5, BFS is chemically suitable for assuming the manufacture of HTLcs since among the four major components of BFS (CaO, SiO2, Al2O3, and MgO), (Ca2++Mg2+)/(Al3+) is generally about 3. On the other hand, the hydrated silica gel after acid leaching process provides the silicon source for zeolite products. It is proved that the philosophy developed in this project not only creates a new possibility for the reuse of BFS, but presents a fresh method for the synthesis of HTLcs and zeolite. With an attempt to reduce the aging time and optimize the processing parameters, this project first analyzed the problems concerning the synthesis of BFS HTLcs via the conventional coprecipitation method. Then in our improved method, the nucleation and crystallization process were performed separately, and the relevant reaction mechanism and kinetics were also discussed. Furthermore, some trace elements inevitably being present in BFS HTLcs were studied so as to figure out the effect of these elements on the layer structure as well as electronic structure of HTLcs and the interaction mechanism of anions between and within the HTLcs layers. Finally, the influence of these trace elements on the preparation of zeolite membrane was investigated on the basis of the current research state of the production of zeolite membrane by employing industrial chemicals.

针对当前高炉渣利用附加值不高的问题，结合高炉渣的实际特点及类水滑石和沸石制备的研究现状，本项目提出了一种利用高炉渣同时制备类水滑石和沸石的方法。该方法巧妙利用了类水滑石要求二价和三价阳离子比值在2~5之间，而高炉渣主四元系CaO、SiO2、Al2O3和MgO中二价和三价阳离子比值约为3的特点，利用高炉渣制备得到类水滑石；其残渣硅凝胶恰为沸石的制备原料，故而也同时制得沸石。该法不仅是高炉渣利用的新方法，也是类水滑石和沸石制备的新方法。本项目首先针对常规共沉淀法制备类水滑石耗时长、过程调控参数有待优化的问题，进行方法改进，将形核与晶化过程分离，并研究其制备过程的反应机制和动力学控制；然后针对所得到的类水滑石中特有的微量元素，研究其对类水滑石层板几何构型、电子结构以及层板与层间阴离子相互作用等的影响机理；最后研究沸石分子筛的形成机理以及高炉渣中的微量元素对沸石分子筛形成的影响和作用行为。

本项目针对高炉渣制备类水滑石、沸石分子筛及高炉渣中微量元素对高炉渣制备类水滑石及沸石的影响等方面内容开展了相应的研究工作，同时补充研究了高炉渣制备介孔二氧化硅，及吸附材料在吸附有害、有毒物质以及CO2方面的影响效果。通过研究得出，在影响高炉渣类水滑石合成的诸多因素中以pH的影响最显著，pH的高低直接影响合成产物的晶相，当pH过低和过高时都不利于类水滑石的生成。温度和时间对类水滑石的合成的影响主要体现在对合成体系的热力学及动力学的影响；合成的高炉渣类水滑石在350 ℃以上焙烧温度下将发生彻底的相变，未焙烧高炉渣类水滑石与焙烧后类水滑石对含P阴离子吸附效果差别较小，高炉渣类水滑石可将P含量降低至痕量水平；n(SiO2)/n(Al2O3)是影响合成沸石类型的关键因素，n(SiO2)/n(Al2O3)=2是合成沸石类型的转变点，小于2合成的沸石为A型沸石，大于2后X型沸石开始生成；温度和时间分别从热力学和动力学的角度影响沸石晶粒的尺寸，合成体系的碱性越强则合成沸石晶粒越细小；低合成nSiO2/nAl2O3和nH2O/nNaOH有利于提高高炉渣合成沸石吸附水体氨氮的效果；沸石用量的增加能提高吸附效果，但会降低沸石吸附效率；沸石吸附氨氮在实验条件下为自发过程；利用盐酸酸浸能够有效将高炉渣中的钙、镁、铝元素进行提取，进而合成Ca-Mg-Al系类水滑石，而余下的滤渣中含有大量的二氧化硅凝胶可以合成介孔二氧化硅MCM-41；两种固体吸附剂在吸脱附循环测试中，表现出优异的性能，经多次循环后，吸附量仍维持在较高的水平。. 本项目针对高炉渣资源化利用的要求，探究了将其制备成类水滑石、沸石、介孔二氧化碳等吸附材料的技术可行性，重点分析了相关参数的选择及优化规律，为高炉渣高效、高值利用提供有效的途径；其制备的产品具有高效的吸附性能，在环境治理等方面将具有很大的应用空间。