协同萃取支撑液膜从粉煤灰中分离回收镓及其传质机理研究

Coal fly ash is the most typical industrial solid waste in China. In terms of environmental and economic consideration, the construction of new method for the fine utilization of the valuable elements in coal fly ash is of importance. The aim of this project is to recover gallium from coal fly ash. To overcome the recovery difficulty due to the low content of gallium, a novel Synergistic Carrier Supported Liquid Membrane (SCSLM) technology with the advantages of outstanding separation efficiency and mass transfer facilitating is proposed. On the basis of the fact that the interactions between oximido and active groups such as -P-OH, -P-SH and –COOH can generate different metal affinities, thus improve the gallium separation efficiency, the synergistic extraction system is synthesized by using active functional groups as the base and oximido as the synergist. The selected systems will be further employed as the carrier during the preparation of the SCSLM. To optimize the mass transfer efficiency of SCSLM, the effect of synergistic carrier composition, supported membrane type and feed/stripping solution flow rate will be adjusted and investigated. The study on the synergistic mechanism, mass transfer kinetics and the separation performance of the SCSLM is the key point of this research work. This project will provide a new route for the exploitation of gallium extraction from coal fly ash, and also support the development of the SCSLM technology with theoretical foundation.

粉煤灰是我国工业固体废弃物之首，创立粉煤灰的元素资源精细化利用新方法具有重要环保和经济意义。本项目以粉煤灰提镓为目的，集中协同萃取体系高效选择和支撑液膜促进传质的优点，构建适合粉煤灰中高效提镓的协同萃取支撑液膜，解决粉煤灰中镓组分含量低、富集分离困难的问题。拟选用-P-OH、-P-SH以及-COOH等活性官能团为基体，引入肟基构筑协同萃取体系，利用肟基与活性基团相互作用对不同金属亲和能力的差异，提高镓选择分离性，并将协萃体系用作传质载体制备协同萃取支撑液膜。通过协萃载体组分配比的选择、支撑膜的筛选、料液/反萃液流速调整优化协同萃取支撑液膜传质效率。重点研究协萃载体对镓的协萃效应和分离特性，揭示协同萃取机理，探索协同萃取支撑液膜对镓离子传递的强化机理和传质动力学规律。本课题的实施将为粉煤灰提镓工艺的开发提供新思路，同时也为协同萃取支撑液膜技术的发展提供基础理论。

本项目提出采用协同萃取支撑液膜技术，将协同萃取体系传质快、选择性高的优点和支撑液膜技术适用于低浓度物质传递、同时可以保留载体萃取性质的特点相互结合起来，用于解决粉煤灰中镓组分含量低、富集分离困难的问题。主要探索了协同萃取体系中各组分参数变化对镓离子协萃和镓/铝分离效应的影响，研究了镓在协同萃取支撑液膜中传递过程和机理。研究发现（1）Aliquat 336与三种有机磷酸类分别混合后对镓的萃取产生了拮抗效应，但是将其水洗之后得到的三种新体系（命名为R4ND2/R4NPC/R4NCy）却对镓产生了显著的协同萃取效应。其中R4NCy体系可以获得108.3的最高协同因数值。同时R4NCy体系具备非常优异的镓离子选择性，优化实验条件后，当Al(III)/Mg(II)/Cu(II)/Fe(II)离子在水相中与镓共存时，R4NCy体系可以实现镓的高选择性萃取，镓的分离因数分别为5144，15472，494以及3473。（2）通过对萃合物特征官能团进行表征，在分析萃合物结构的基础上，对比协萃体系萃取前后结构变化，发现R4NCy体系在不同酸度下以阳离子取代和离子缔合两种不同的协萃机理对镓进行萃取。（3）在研究协同萃取支撑液膜的传质性能中发现，镓的传递效率受H+迁移的影响。R4NCy体系中有机磷酸根对Cl-的取代，强化了其阻氢性能同时也提高了对GaCl4-的传递能力。通过优化实验条件，R4NCy协同萃取支撑液膜在运行8小时后，镓与铝的渗透分离因数可达2906。本项目的开展能为镓在协同萃取支撑液膜中的应用提供理论依据和实验基础，同时也为粉煤灰元素资源化的规模化和工业化奠定基础。