膜萃取处理水溶液中镉、锌离子的工艺

以P204+正庚烷为萃取剂,将中空纤维膜萃取技术用于处理水溶液中镉离子、锌离子.研究了两相流速、初始浓度及溶液pH等因素对传质系数和萃取率的影响,计算了膜萃取器的传质单元高度(HTU)_w,同时还研究了萃取剂的再生问题.实验结果表明,在低浓度下(＜500 mg/L),平衡分配系数较大,传质阻力主要是在水相;在初始浓度较高时(＜2000mg/L),由于分配系数较小,三项传质阻力均不可忽略;在初始浓度很高时(＞2000mg/L),传质由有机相和膜相阻力控制.实验还表明通过膜器串联可以实现萃取剂的再生.对于稀溶液(＜200mg/L),中空纤维膜萃取可以使水溶液中金属离子浓度减小2个数量级,通过计算,中空纤维膜萃取器(HTU)_w在15～30cm之间,大大低于传统的萃取塔.

Recovery of Zinc Ion and Cadmium Ion with Hollow Fiber Membrane Extraction

The efficiency of hollow fiber membrane solvent extraction for the system of Me_aq/bis(2-ethylhexyl) phosphate in heptane(Me=Cd²⁺,Zn²⁺) was studied for wastewater treatment and hydrometallurgy.It was found that the two phases velocity,the initial concentration and the pH value of the aqueous phase greatly influenced the extraction ratio.For very dilute solution with concentration lower than 500mg/L,the mass transfer resistance was mainly in aqueous phase.When the aqueous phase concentration was relative higher than that of dilute solution,all the individual mass transfer resistances would not be ignored.For the concentrated solution,the mass transfer in the organic phase and the diffusion in membrane pores controlled the transport process.In the back extraction,the mass transfer resistance lied in the organic phase and the diffusion in membrane pores.The experimental results showed that it was possible that the extraction percentage achieved 90% when the metal ion concentration was lower than 400 mg/L.When the cadmium concentration was lower than 200mg/L,its concentration can decrease 2 orders by extraction in a single-pass flow mode.The values of (HTU)_w were between 15cm and 30cm,which was much lower than those of traditional extraction columns.The results indicated that membrane extraction with hollow fiber modules could efficiently remove or recover metal ions in the aqueous phases.