分散支撑液膜中四价铈的传输分离

Transport and Separation of Cerium(IV) in Dispersion Supported Liquid Membrane System

研究了以聚偏氟乙烯膜(PVDF)为液膜支撑体,煤油为膜溶剂,2-乙基己基磷酸-单-2-乙基己基酯(PC-88A)为流动载体,煤油和PC-88A的混合溶液作为膜溶液,膜溶液和HCl溶液组成分散相的分散支撑液膜(DSLM)中Ce(IV)的传输行为;考察了料液相酸度、Ce(IV)起始浓度、HCl浓度、膜溶液与HCl溶液体积比、解析剂及载体浓度对Ce(IV)传输的影响,得出其最优传输分离条件为:HCl浓度4.0mol/L,膜溶液与HCl溶液体积比2:1,载体浓度0.16mol/L,料液相中HCl浓度0.1mol/L.在最优条件下,料液相中Ce(IV)的初始浓度为0.7×10-4mol/L时,迁移75min,其迁移率达到96.3%.提出了Ce(IV)在DSLM中的传质动力学方程,得出Ce(IV)在膜中的扩散系数为6.69×10-8m2/s,料液-膜边界层厚度为19.3μm.对模拟样品Ce(IV)的分离结果表明,在一定条件下,125min内模拟煤粉灰中Ce(IV)迁移率达到92.8%;105min内模拟冶金熔渣中其迁移率可达92.6%;215min内Ce(IV)与Eu(Ⅲ)的混合液中Ce(IV)迁移率达到83%,其他元素迁移率极低.

The transport of Ce（Ⅳ） through a dispersion-supported liquid membrane consisting ofpolyvinylidene fluoride membrane as the liquid membrane support and dispersion solution including HCl solution as the stripping solution and 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester （PC-88A） dissolved in kerosene as the membrane solution was studied. The effects of HCI concentration, initial concentration of Ce（Ⅳ） in the feed phase, volume ratio of membrane solution to stripping solution, concentration of HCl solution, concentration of carrier, different stripping agents in the dispersion phase on transport of Ce（Ⅳ） were also investigated. The optimum transport conditions of Ce（Ⅳ） were obtained as that HCl concentration was 4.0mol/L, carrier concentration 0.16mol/L, volume ratio of membrane solution to stripping solution 40：20 in the dispersion phase, and HCI concentration 0.1 mol/L in the feed phase. Under the conditions, when initial concentration of Ce（Ⅳ） was 0.7×10^-4 mol/L, the transport rate of Ce（Ⅳ） was up to 96.3% in 75 min. The kinetic equation was developed. The diffusion coefficient of Ce（Ⅳ） in the membrane and the thickness of diffusion layer between feed phase and membrane phase were obtained, being 6.69×10^-8 m^2/s and 19.3μm, respectively. The separation result of Ce（Ⅳ） in simulated samples showed that under the certain conditions, transport rate of Ce（Ⅳ） of fly ash was up to 92.8% in 125 min, transport rate of Ce（Ⅳ） of molten slag up to 92.6% in 105 min and transport rate of Ce（Ⅳ） of mixed solution of Ce（Ⅳ） and Eu（Ⅲ） up to 83% in 215 min. The transport rates of other ions were extremely low.