气泡表面油膜萃取极低浓度金属离子新方法的机理研究

The hydrometallurgical and environmental chemical processes bring a large amount of industrial waster containing various poisonous and carcinogenic heavy metal ions with extremely low concentration. For the treatment of those wastewater, new pollutes will be produced, and a large amount of heavy-metal waste concentrates occur and are hard to be recovered for reusing. The traditional techniques were only aimed to remove the heavy-metal ions, so that the water can be discharged according to the requirements of environmental protection, but the processes were extremely low efficient and economically not reasonable. In our previous works, a new large-phase-ratio solvent extraction method was suggested by covering a layer of organic extractant liquid membrane on the surface of gas bubbles to achieve the enrichment and extraction of the metal ions into the organic liquid membrane layers. In this proposed program, we want to focus on some crucial problems, 1) the conditions for the formation of stable organic liquid membrane on the surface of gas bubbles and the key factors which will bring influence on the stability of the organic membrane; 2) the kinetic rules for enrichment of metal ions into the organic liquid membrane layer of the gas bubbles, and the quantitative relationship of the extraction kinetic rate with those possible influence factors; 3) the microscopic mechanism for the mass transferring of metal ions on the surface of organic liquid membrane and essential driven-force for that process. The aim of the present work is to clarify some fundamental scientific problems that might bring crucial influences during the process of large-phase-ratio extraction of metal ions on the surface organic liquid membrane layer of the gas bubbles, so that can provide scientific support for the future of the structural design of the industrial equipments and processing enlargement.

冶金和环境化工领域产生大量含极低浓度有毒有害金属离子的工业废水。现有技术主要致力于脱除水体中的金属离子，目标在于治理废水，无法实现水体中低浓度有价重金属离子的高效回收。治理废水过程中还产生大量低品位重金属废渣，难以经济利用，成为一种新的污染物。前期工作提出一种气泡表面包覆一层有机萃取剂油膜，从而实现低浓度金属离子大相比萃取富集提取的新方法。本项目拟重点研究气泡表面油膜层的形成条件及影响其稳定性的关键因素；研究油膜萃取的动力学规律，构建气泡表面油膜萃取低浓度金属离子的萃取速率与过程影响因素间的定量表达式；研究气泡表面油膜层萃取捕集金属离子的过程微观机制及传质推动力。本项目的研究成果可为发展气泡支撑油膜萃取新方法奠定理论基础，为低浓度大相比鼓泡油膜萃取塔的结构设计及工业放大提供科学依据。

本项目采用大相比气泡支撑有机液膜萃取装置，改变有机相性质、水相性质及操作条件等因素，研究了有机相在典型亲疏水固体材质（玻璃与PVC）界面上的润湿铺展行为及其关键影响因素，建立了铺展速率与关键影响因素间的数学定量关系式。考察了化学反应驱动下有机液膜在气-水界面的铺展润湿行为及其关键影响因素。研究表明，液-液界面化学反应对有机液滴的润湿铺展具有一定的驱动作用，铺展系数与粘弹比对铺展速率具有重要影响。测定气泡表面油膜层的成膜速率、气泡生长速率及有机相在气泡表面铺展形成油膜层的成膜速率随气泡生长速率的变化，阐明了大相比气泡支撑有机液膜的生成机制。对有机气泡液膜的受力进行分析，弄清了大相比气泡支撑有机液膜的失稳机理及其关键影响因素。在气泡支撑液膜能够稳定生成的条件下，人为调控气泡表面油膜层的厚度和界面更新速率，考察了膜层厚度与界面更新速率对萃取速率的影响。结果发现，液膜越薄，萃取速率越快，液膜越不稳定，界面更新速率越快，萃取速率越快，液膜越不稳定；并建立了气泡表面油膜萃取金属离子的萃取速率与关键影响因素间的定量表达式。研究气泡表面油膜萃取金属离子的过程中，各种影响因素导致油膜层萃取剂分子与水相离子间相互作用的变化，剖析导致萃取速率变化的微观机理。研究了气泡表面油膜层厚度与油膜层动态吸附量之间定量关系，建立了油膜层界面萃取剂分子/金属离子间相互作用变化导致的界面动态吸附量随时间变化的数学定量表达式，揭示了油泡表面油膜捕集水相中低浓度金属离子的微观机制及推动力。