针对饱和卤水直接制碱过程需要去除硫酸根、钙离子、镁离子（SO₄^2-、Ca²⁺、Mg²⁺）等杂质离子的问题,探索了利用纳滤膜分离精制饱和卤水新工艺。通过考察NF270、DL2540、ESNA1 3种类型纳滤膜的透过通量和离子截留率,确定了选用DL2540为实验用膜;分析了DL2540纳滤膜对离子的截留性能和对盐田饱和卤水的分离性能及其对饱和卤水精制的效果。结果表明,增加同离子浓度、降低压力有利于不同价态阳离子、阴离子间的分离,DL2540纳滤膜对盐田饱和卤水中SO₄^2-、Ca²⁺、Mg²⁺截留率分别达到95%以上、30%~50%、30%~70%,对Na⁺、Cl^-截留率均低于15%,进一步证明DL2540纳滤膜具有较好的稳定性和二价离子截留效果,在饱和卤水精制上展示出较好的应用前景。

Aiming at the problem that SO₄^2-,Ca²⁺,Mg²⁺ and other impurity ions need to be removed in the process of direct alkali production from saturated brine,a new process for separating and refining saturated brine with nanofiltration membrane was explored.By examining the flux and ions rejection rate of three types of NF270,DL2540 and ESNA1 nanofiltration membranes,DL2540 was chosen as the experimental membrane.The effects of DL2540 nanofiltration membrane on ions rejection rate,separation performance of saturated brine from salt field and the refining effect of saturated brine were analyzed respectively.The results showed that increasing the concentration of the ions and reducing the pressure was beneficial to the separation of cations and anions with different valences.The rejection rates of SO₄^2-,Ca²⁺ and Mg²⁺ in the saturated brine of salt field reached 95% above,30%~50% and 30%~70%,respectively.The rejection rates of DL2540 nanofiltration membrane on Na⁺ and Cl^- were both lower than 15%,which further proved that DL2540 nanofiltration membrane has better stability and divalent ions rejection effect,and showed promising application prospect in saturated brine purification.