纳滤膜对高镁锂比盐湖卤水镁锂分离性能研究

Study on separation of magnesium and lithium from salt lake brine with high magnesium-to-lithium mass ratio by nanofiltration membrane

纳滤作为一种新兴的膜分离技术,在高镁锂比盐湖卤水镁、锂分离领域具有非常好的应用前景。研究了不同镁锂比、原料液循环流量对镁锂分离过程的影响,并对膜分离过程中的分离机理进行分析。结果表明原料液镁锂比对膜通量影响较小,镁、锂离子截留率及镁锂分离效果均随原料液镁锂比的增加而降低。当原料液循环流量为225 L/h时,镁离子截留率为95%,锂离子截留率为-66%,透过液镁锂比降低至1.2。膜分离传质机理研究表明,镁离子在分离过程中受到较强的介电排斥效应与尺寸筛分效应。纳滤技术能够有效降低高镁锂比盐湖卤水的镁锂比,为后续高纯锂盐的制备提供基础。

As an emerging membrane separation technology,nanofiltration has a potential application in separating magnesium and lithium from salt lake brine with a high magnesium-to-lithium mass ratio(Mg/Li).The separation of magnesium and lithium at different Mg/Li and cross-flow rates was evaluated and analysis on the mechanism in separation process was performed.The results showed that the membrane flux remained almost constant at different Mg/Li,the retention rates of magnesium and lithium and the separation efficiency decreased with increasing Mg/Li.When the cross-flow rate was 225 L/h,the retention rates of magnesium and lithium were 95%and-66%,respectively.In addition the Mg/Li in the permeate was reduced to 1.2.Study on the mechanism of mass transport for membrane process showed that magnesium was greatly influenced by dielectric exclusion,and steric hindrance.Nanofiltration shows considerable promise as a means to separate magnesium and lithium from salt lake brine with high magnesium-to-lithium mass ratios,which provides the basis for the subsequent preparation of high-purity lithium salt.