粘土矿物选择性絮凝法强化煤泥浮选的理论研究

Enhancing fine coal flotation remains a major challenge worldwide to effective utilization of limited coal resources. Slime coating of clays on fine coal under colloidal forces has been identified as a key reason, which further reduces floatability of fine coal and leads to severe contamination of fine coal product. To resolve this challenge and enhance fine coal flotation, it is necessary to further understand the nature of colloidal interactions between various types of clays and fine coal so that they can be controlled as desired. In this project, QCM-D will be used for the first time to study clay deposition on coal surfaces under controlled water chemistry environment, such as pH, calcium and magnesium ion concentration, determining the nature of clay slime coating on fine coal. .A key contribution from this study is to prepare clay basal plane and edge surfaces on QCM-D silica and alumina sensors, monitored by QCM-D signals and characterized by SEM. The success of this approach allows us to determine anisotropic characteristics of clay surfaces and its interactions with polymer flocculants. From this fundamental study, a novel idea of enhancing fine coal flotation by selective flocculation of fine clays to avoid slime coating will be proposed and tested by determining flocculant adsorption on coal and various clay surfaces as well as deposition of clays on coal with and without adsorbed polymers.This study will lay foundation for a completely new process concept of enhancing fine coal flotation by selective flocculation of fine clays, which will be explored by laboratory scale flotation tests. Main research topics include: 1) mechanism of clay deposition on coal as a function of water chemistry; 2) polymer flocculant adsorption on coal and clay surfaces; 3) correlation between flocculant adsorption and selective flocculation; and 4) novel process of enhanced fine coal flotation by selective flocculation of fine clays.

强化煤泥浮选仍是煤资源有效利用的世界难题。其中原因之一是粘土颗粒与煤泥之间的胶体作用力导致粘土在煤泥表面罩盖，使煤泥浮选效率进一步降低和粘土在煤精矿中的严重夹带。为提高煤泥浮选效率，有必要进一步揭示粘土与煤泥相互作用的实质并加以调控。本课题采用具有耗散因子功能的石英晶体微天平（QCM-D）研究粘土与煤泥相互作用机理。.同时提出一个通过粘土选择性絮凝强化煤泥浮选的原型技术思路。为证实这一技术思路，有必要对高分子絮凝剂在粘土表面选择性吸附热力学、动力学及吸附形貌进行研究，建立粘土选择性絮凝强化煤泥浮选的理论，并实验证实此原型技术思路的可行性与优越性。为实现这一目标，我们将首次制备模拟煤和粘土传感器并进行下列有关研究：1) 煤与粘土微粒相互作用；2)高分子絮凝剂在粘土与煤表面吸附行为与机理；3)选择性絮凝；和 4)粘土选择性絮凝强化煤泥浮选原型技术。

目前，絮凝是一种实现固-液分离的有效方法，而研发高性能絮凝剂是提高固-液分离效率最直接的途径。根据这一前提，开展了新型高分子絮凝剂的制备及其絮凝机理的相关研究，主要成果如下：.首先，通过自由基聚合法及物理共混法制备了一系列聚N-异丙基丙烯酰胺基温敏型高分子絮凝剂，并对其结构和性能进行了表征。利用带耗散因子功能的石英晶体微天平（QCM-D）研究了温度诱导无机-有机混合温敏型高分子A-PN-D在固-液界面上的吸附及构型变化的动态过程，并详细研究了电解质类型及其浓度对无机-有机混合温敏型高分子絮凝剂A-PN-D絮凝行为的影响。.研究表明阳离子聚合物和阴离子聚合物两种絮凝剂在高岭石基面的吸附是由静电吸引和氢键驱动的。阴离子聚合物更易于通过弱静电吸引和氢键作用吸附在高岭石的八面体基面；而通过较强的静电吸引力和氢键作用吸附在高岭石的四面体基面。提出了加入混合絮凝剂（阳离子聚合物和阴离子聚合物）可提高细颗粒悬浮液的固液分离过程。.为研究絮凝剂分子在不同基面和边（断）面吸附作用机理，首次利用超薄切片技术制备了非常光滑的滑石边面，基于这一前提，我们利用经典DLVO理论对AFM探针与滑石边面与基面间的相互作用力曲线进行了拟合，从而获得了不同pH溶液中滑石各项异性的表面电荷特性。研究发现滑石基面带永久性的负电荷，而滑石边面电荷大小则与体系pH相关，当pH小于8时带正电荷；pH大于9时带负电荷。.利用超薄切片技术制备超平云母边面，通过原子力显微镜测量了探针与云母边面和基面在低电解质溶液中相互作用力曲线。基于经典DLVO理论，对力曲线进行拟合分析，最终获得了云母边面电荷特性。同时测量了二价离子钙离子和镁离子对于云母边面Stern电势的影响。研究发现钙离子和镁离子的加入会导致云母Stern电势更负，但是即使提高离子浓度至5mM，Stern电势也不会变为正值。钙离子的加入对Stern电势的减小量要大于镁离子。这些电性质变化都会影响絮凝剂在其表面吸附特性和絮凝行，为从而改进煤泥浮选。

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