用于冶金酸浸液提铟的复合膜及液膜耦合过程研究

Solvent extraction is the main process applied in extraction of indium, however, it has drawbacks of complicated process, large extractant consumption and environmental pollution. Supported liquid membrane has the potential to be the substitute, whereas the loss of membrane liquid during the process limits its large scale application. To solve these problems, this project focus in improving the liquid membrane support by developping a composite membrane, which containing a hydrophilic gel layer on the lumen surface of hydrophobic PVDF hollow fiber membrane. The effect of microstructure and characteristics of the composite membrane on the interfacial mass transfer efficency will be investigated, moreover, a new way to reduce membrane liquid loss will be proposed. During the study, the mechanism of controlling membrane loss via analyzing the membrane support properties will be uncovered. In addtion, using the composite membrane as the membrane liquid support, a new hybrid system combining supported liquid membrane, oil/water ultrafiltration, and membrane degassing processes will be developed for enhancing extraction process, reducing membrane loss and shortening the process. Through theorectical and experimental studies, the mechanism of mass transfer facilitation in stripping process by organic phase dispersion will be revealed. The influence of operating parameters on ultrafiltration of oil/water mixture will be investigated and the effective method for reducing organic loss will be obtained. Furthermore, the study will clarify the mass transfer characterists of membrane degassing process for recovering of waste acid and simultaneously pricipitation of indium hydroxide. Finally, an environmental-friendly hybrid membrane system with merits in efficient extraction, performance stability, as well as process simplicity will be obtained.

针对溶剂萃取法提铟过程复杂、二次污染和支撑液膜技术瓶颈-膜液流失问题，首先进行液膜支撑体改进，在疏水性聚偏氟乙烯微孔膜内表面涂覆亲水性凝胶层构成复合膜，探索复合膜支撑体微结构与特性对界面传质的影响规律并获得缓解膜液流失新途径，从支撑体本身特性角度探讨液膜流失抑制原理与方法。其次，采用复合膜为液膜支撑体，将支撑液膜、油水超滤分离、膜脱气过程相结合，建立促进萃取与反萃进程、缓解膜液流失、缩短提取流程的新型耦合过程。通过对耦合系统的理论与实验研究，揭示有机分散相对反萃传质的促进机理、丰富和发展支撑液膜萃取基本原理；研究运行条件对超滤过程油水分离的传质影响规律，获得缓解膜液从系统流失的有效方法；明晰膜脱气过程从反萃剂中回收挥发酸、同时析出富铟沉淀的传质特性；最终获得兼具高效提取、性能稳定、简化流程、环境友好的金属离子提取耦合膜过程。

本项目针对支撑液膜运行过程中的膜液流失问题，从聚偏氟乙烯（PVDF）中空纤维支撑液膜、超滤、膜脱气过程相结合的分离工艺研究、及疏水性支撑体的表面亲水化改进两方面入手，探讨了缓解膜液流失的有效途径，实现了支撑液膜稳定性的有效增进。首先通过系统的实验研究，探明了支撑液膜-超滤耦合过程的运行工艺条件（液膜两侧流速、超滤流速、料液浓度等）、PVDF疏水性微孔支撑体壁厚及支撑液膜组件装填密度等对铟传质效率的影响规律，并利用优化后的工艺体系对铟进行了连续富集。研究结果显示在反萃剂中分散萃取有机相可大幅促进反萃传质（反萃率提升70%以上）并在一定程度上缓解膜液流失引起的通量衰减。其次，利用传质关联式对铟离子在料液相主体、料液相边界层、液膜内部、反萃相边界层、反萃相主体内的分传质系数进行了计算，确定了铟离子与载体形成的缔合物在支撑体微孔内膜液中的传质为整个传质过程的控制因素；建立了中空纤维支撑液膜系统的传质模型，并利用不同的管程线性流速、料液初始浓度、中空纤维支撑体壁厚条件下的铟的萃取与反萃效率数据对数学模型准确性进行了验证，该模型可用于从酸浸液中提取铟的传质效率预测。而后，研究了利用聚偏氟乙烯膜脱气工艺对经超滤后的反萃剂盐酸进行在线脱除与回收，研究数据显示盐酸的脱除率随脱气膜面积及料液浓度的增高而显著提升，最高盐酸脱除率达85%。最后，采用界面聚合法在PVDF疏水微孔支撑体外表面构建亲水性薄层以实现对膜液的锁闭，预防膜液流失。考察了四种界面聚合水相单体的结构、官能团性质对复合层亲水性、孔结构和荷电性、及对复合支撑液膜传质效率的影响；确定了以赖氨酸与均苯三甲酰氯分别为水、油相单体制得的复合支撑液膜在运行过程中具有良好的膜液锁闭能力和料液渗透能力，有效减缓了膜液的流失，复合支撑液膜运行30h传质通量衰减率较未经改性的原支撑体降低了71.7%，而总提取率提升了7.0%。与原支撑体相比较，表面亲水化改性的复合支撑体具备大幅增强支撑液膜运行稳定性并兼具传质促进作用的双重优势。研究成果对推动SLM过程的工业化进程，具有积极的指导意义。