磁性流体固定床萃取分离重金属的理论分析与实验研究

The low-concentration heavy metals discharged from industries are harmful to living species. Therefore, they must be removed from polluted streams in order to meet increasingly stringent environmental quality standards. However, there are some disadvantages for separating and recovering low-concentration heavy metals by conventional methods included solvent extraction and fixed-bed adsorption..The focus of this project is a novel, simple and rapid model of extraction process. The original so-called "magnetic-fluids fixed bed" (MFFB), which bridges solvent extraction and fixed-bed adsorption by the theory of the high gradient magnetic separation, has been explained. The MFFB integrates the advantages of the two above mentioned classical extraction methods and overcomes their drawbacks..In the high gradient magnetic separator filled with ferromagnetic steel wires, the magnetic fluids containing extractant are immobilized well-distributed as stationary phase in form of liquid-droplet on the surface of wires under nonhomogeneous magnetic field. The aqueous solution of heavy metal ions, as mobile phase, flow through controlled-porosity high gradient magnetic separator and is extracted by magnetic extractant. This method is similar to fixed-bed adsorption in form, but its extraction mechanism is solvent extraction because heavy metal ions are extracted by liquid magnetic fluids containing extractant..The Au(III) and Cr(VI) are selected as models of heavy metal ion in our research. The theoretical model of the extraction process is established, and the effects of various factors on the extraction efficiency of magnetic fluids containing extractant are investigated in details. The purpose of this project is to verify the feasibility of this method by the experiments and explore a new separation process to be suitable for extraction of low concentration heavy metal ions aqueous solution,.

低浓度重金属废液的工业排放造成严重的资源浪费和环境污染，急需回收和治理，"十二五"规划把《重金属污染综合防治》提高到前所未有的高度。.针对液-液溶剂萃取、固-液固定床吸附分离技术在回收处理重金属离子废液过程中存在的问题，本项目将溶剂萃取和固定床两种分离模式的优点集成于一体，同时克服了两者各自的缺点，提出了一个全新的集成创新分离模式-磁性流体固定床萃取分离方法。.该方法利用高梯度磁性分离原理，将含萃取剂磁性流体以液滴的形式固定在分离柱金属丝表面，构建一个磁性流体液滴在分离柱内均匀分布、具有一定孔隙率的磁性流体固定床。它在形式上类似于固定床，但其"吸附剂"是被高梯度磁场控制的含萃取剂磁性流体液滴，而非固体颗粒，它的分离机理与液-液萃取相同。.在前期工作基础上，以重金属实际分离体系为对象，本项目拟系统开展磁性流体固定床萃取分离模式的理论分析和实验研究，为工业化处理解决关键科学问题和技术难题。

资源与环境问题成为制约我国经济和社会可持续发展的关键瓶颈。本项目以低浓度重金属废水为对象，提出了一个全新的磁性流体固定床萃取分离技术方法。在此基础上，系统地开展了磁性流体固定床萃取分离模式的理论分析和实验研究，构建了磁性流体固定床萃取分离平台，实现了重金属高效萃取分离过程。.合成出了平均粒径为8.0 nm的Fe3O4颗粒，粒径分布较窄，分散性好；将油酸在Fe3O4表面包裹形成一个具有双分子层结构的疏水外壳，与萃取剂磷酸三丁酯分散在稀释剂煤油中，制成了磁性流体萃取剂，比饱和磁化强度为12.85 emu/g。.通过模拟计算，设计了磁性流体固定床磁路部分最佳尺寸，其中，磁性分离室有效磁场空间为37mm×37mm×300mm。制造了C型和H型两套钕铁硼永磁体磁路系统，测量其工作气隙中的磁场强度为3500高斯。.研究了磁性流体萃取剂在单根丝高梯度磁场中静力学聚积理论和在多根丝高梯度磁场中的分布状态，推导出了聚集半径、轮廓面积和孔隙率的数学表达式。实验测量了磁性流体分布状态参数、孔隙分布状态参数与其控制参数之间关系。.实验研究了铁磁性材料填充介质的类型和排列方式对磁性流体分布和孔隙分布状态的影响。构建了两套1L/h和5L/h规模的磁性流体固定床萃取分离装置。.以模拟含金水溶液和模拟含铬水溶液为萃取分离对象，研究了磁性流体固定床对金和铬离子的萃取效果，结果显示，（1）稀释剂种类对萃取效果的影响不是很明显；（2）pH值越低，萃取效果越好；（3）40%的TBP含量是理想的萃取剂含量；（4）流动相流速越低萃取效果越好；（5）Cr(VI)起始浓度越高萃取效果越好。.利用构建的5L/h规模的磁性流体萃取分离装置，开展了含Cr制革废水、含Cu电镀废水以及含Au冶金废水等实际体系的重金属废水处理和资源回收技术开发工作。以含Cr制革废水为例，Cr含量从50-100ppm降低到3ppm，达到了国家含铬废水的排放标准。