协同萃取-中空纤维更新液膜富集分离重稀土元素的传质性能研究

With the exploitation and utilization of the weathered crust elution-deposited rare earth (RE) ore, the efficient extraction of the valuable RE resources has become the imminent great demand of our country for the low peak concentration and complex composition of RE in the extract. The new method of enrichment and separation of heavy RE elements with synergistic extraction –hollow fiber renewal liquid membrane has been proposed in view of the difficult problems of traditional solvent extraction such as multi extraction stages and low extraction liquid yield. The method not only brought the superiority of good selectivity of the synergistic extraction system into full play, but also utilized the advantage of high mass transfer rate of renewal liquid membrane equitably. The project will centre on solving the problems of adaptability of the synergistic extraction system and the hollow fiber renewal liquid membrane. The method will be studied systematically including: (1) The effect regular of the physicochemical properties of liquid phase on the film forming process and stabilization of hollow fiber renewal liquid membrane. (2) The mass transfer performance of the synergistic extraction - hollow fiber renewal liquid membrane on the enrichment and separation of heavy RE elements. (3) Establishing the mass transfer model of the synergistic extraction - hollow fiber renewal liquid membrane. (4) Realizing the efficient enrichment and separation of heavy RE elements from the extract of the weathered crust elution-deposited rare earth ore using the difference of mass transfer rate among heavy RE elements. The project will supply the new methods for the heavy RE elements extraction, which has both academic value and good prospect of industrial application.

随着风化壳淋积型稀土矿的开采和利用，其浸出液中稀土峰值浓度很低、组成复杂，高效提取这一宝贵稀土资源已成为国家重大需求。本申请针对传统的溶剂萃取法存在萃取级数多，浸出液收液率低的难题，提出了协同萃取-中空纤维更新液膜富集、分离重稀土元素的新方法。该方法既充分发挥了协同萃取体系选择性好的优越性，又合理利用了液膜传质速率高的优势。本项目将围绕解决协同萃取体系与中空纤维更新液膜适应性的问题，对该方法进行系统研究，包括：(1)液膜相的物理化学性质对中空纤维更新液膜成膜过程及其稳定性的影响规律；(2)协同萃取-中空纤维更新液膜富集、分离重稀土元素的传质性能；(3) 建立协同萃取-中空纤维更新液膜传质模型；(4) 利用重稀土元素间传质速率的差异，实现风化壳淋积型稀土矿浸出液中重稀土元素的高效富集、分离。该项目完成后，将为重稀土元素的提取提供新的方法,不仅具有一定的学术理论价值，还具有良好的工业应用前景。

本项目以“开发风化壳淋积型稀土矿浸取液深度提取技术”为着眼点，研究了2-乙基己基膦酸单-2-乙基己基酯(HEHEHP)+二-（2，4，4-三甲基戊基）膦酸(Cyanex272)体系萃取重稀土元素Er3+、Tm3+、Yb3+和Lu3+的协同效应，计算了协萃增长因子，并利用斜率法计算了萃合物的组成及萃取机理。分别采用HEHEHP-正庚烷以及二(2-乙基己基) 磷酸(HDEHP)-正庚烷为膜溶液，盐酸为反萃取剂，中空纤维膜作支撑膜，研究中空纤维分散液膜技术富集稀土镱(Yb3+) 离子。考察了体系物性：反萃分散相中反萃剂浓度、萃取剂浓度、萃取剂与反萃剂体积比、料液相pH值、稀土离子浓度；流体流动状态：反萃分散相与料液相流速变化等因素对富集稀土离子的影响。得到中空纤维分散液膜富集Yb3+的最佳条件。在溶剂萃取的基础上，以优选的酸性磷（膦）类协同萃取体系HEHEHP+Cyanex272/庚烷作为中空纤维支撑液膜的膜溶液，采用聚偏氟乙烯(PVDF)中空纤维支撑液膜(HFSLM)研究了镱(Ⅲ)的迁移行为。得到了Yb3+在HFSLM系统中的最佳传输条件。同时基于费克定律，推导了稀土离子传质速率方程，计算得到料液相传质系数(ki) 及有机相传质系数(Km) 分别为0.11cm/s和9.52cm/s，表明重稀土离子在协同萃取-中空纤维更新液膜中的传质过程受稀土络合物在液膜相中的扩散控制。通过协同萃取-中空纤维更新液膜富集分离重稀土元素的传质性能研究，筛选得到了性能优良的分离工艺条件，寻找出其体系物性及流体流动状态对分离制备单一、高纯重稀土产品的影响，为建立选择性好，传质速率快，有机溶剂用量少，稀土浸出液收率高的重稀土元素富集、分离新方法打下基础。