中空纤维分散液膜富集稀土元素

摘要

采用2-乙基己基膦酸单-2-乙基己基酯(HEHEHP)-正庚烷为萃取剂,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. 中空纤维分散液膜富集Yb3+的最佳条件为:萃取剂浓度为0.25 mol/L,反萃取剂HCl浓度为4.00 mol/L,萃取剂与反萃剂体积比为10∶40,料液相pH=2.80,稀土离子浓度为0.025 mol/L. 反萃分散相体积流量和料液相体积流量较小时, 萃取率随流量的增加呈现逐渐增大的趋势.若两相体积流量过大,反萃过程进行不完全,萃取率反而下降. 研究结果表明,中空纤维分散液膜技术可实现稀土离子的有效富集.%The hollow fiber dispersion liquid membrane technique was applied for the enrichment of rare earth using 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester(HEHEHP) as the extractant and HCl as the stripping agent.All experiments were conducted in the hollow fiber modules that were self-assembled with 20 microporous hydrophobic hollow fiber of polyvinylidene fluoride membrane(PVDF) lumens.The experiment parameters, e.g., HCl concentration, extractant concentration, initial pH in feed phase and rare earth ions concentration, and the volume ratio of the stripping dispersion phase to the feed solution, etc., were investigated.The stripping dispersion phase and the feed phase(50 mL each) were agitated continuously to provide a uniform concentration of metal ions and circulated by means of precise constant flow pumps through the shell side and lumen side of the module, respectively.A membrane pressure was applied in the lumen side to prevent the dispersion of the organic phase into the feed phase.The flow rates of both phases were maintained constant with the help of the constant-flow pump equipped with a precise flow controller.After the stable flows are achieved on both the shell side and the lumen side, aqueous samples are taken from the reservoir every ten minutes for analysis of concentrations of rare earth ions.The optimum extraction conditions of Yb3+ were obtained:the HCl concentration is 4.00 mol/L in the stripping dispersion phase, the concentration of HEHEHP is 0.25 mol/L, the volume ratio of the stripping dispersion phase to the feed solution is 10∶40, the pH value in the feed phase is 2.80, and the initial concentration of Yb3+ is 0.025 mol/L.The optimum conditions obtained may contribute to the development of new methods for the extraction of heavy rare earth ions.