二次界面聚合法制备具有高锂镁分离性能的电纳滤膜

Preparation of Electro-nanofiltration Membranes with High Li^(+)/Mg^(2+)Separation Performance via Sequential Interfacial Polymerization

通过调控界面聚合水相单体并利用二次界面聚合(SIP)构建荷正电表面,制备了高选择性电渗析分离锂镁的电纳滤膜(ENFMs).采用不同水相单体与均苯三甲酰氯进行单次界面聚合(IP),实现了对分离膜孔径及荷电性能的调控,其中以哌嗪为水相单体时膜的Li^(+)/Mg^(2+)分离性能最优(P_(Mg^(3+)^(Li^(-)))=4.75).随后,利用SIP过程在其表面聚合不同浓度的荷正电水相单体聚乙烯亚胺(PEI,M_(W)=70000),使膜表面由荷负电转为荷正电.随着PEI浓度的增加,膜表面正电荷密度显著增加,PEI质量分数为2.0%时,最优膜的Li^(+)通量为3.26×10^(-8)mol·cm^(-2)·s^(-1),选择性高达15.90,打破了传统的“Trade-off”效应,为后续盐湖卤水中Li^(+)/Mg^(2+)分离的研究和应用奠定了基础.

Highly selective electro-nanofiltration membranes(ENFMs)were prepared by regulating the aqueousphase monomers of interfacial polymerization(IP)and constructing the positively charged surface by sequential interfacial polymerization(SIP)for the separation of lithium and magnesium by selective electrodialysis processes.The IP reaction was carried out using different aqueous-phase monomers with trimesoyl chloride to achieve the regula⁃tion of the pore size and charging property of the separation membranes.The optimum Li^(+)/Mg^(2+)separation performance(4.75)of the membrane was achieved when piperazine was used as the aqueous-phase monomer.Subsequently,the SIP reaction was utilized to introduce positively charged aqueous-phase monomer polyethyleneimine(PEI,MW=70000)of different concentrations on the optimal IP membrane surface,which converted the charge of the membrane surface from negative to positive.With the increase of PEI concentration,the positive charge density on the membrane surface increased significantly;the optimal SIP membrane achieved outstanding selectivity for Li^(+)/Mg^(2+)(15.90)and high Li+flux(3.26×10^(‒8)mol⋅cm^(‒2)⋅s^(‒1)),which breaks the traditional“Trade-off”effect and lays the foun⁃dation for the subsequent research and application of Li^(+)/Mg^(2+)separation salt-lake brines.