High efficient dye desalting mixed matrix nanofiltration membranes containing in-situ grown ZIF-L particles in polyethyleneimine(PEI)coating before interface polymerization
Zeolitic imidazolate frameworks(ZIFs)are considered to be one of the best materials for breaking through the upper limit of membrane materials due to their structure being adjustable,easy preparation and excellent stability.In this study,a high-performance dye desalination mixed matrix loose nanofiltration membrane was obtained by the in-situ growth of ZIF-L particles on a polyethyleneimine(PEI)based coating and followed by interfacial polymerization with trimesoyl chloride(TMC).Using the coordination action between PEI and Zn2+,the uniform distribution of Zn(Ⅱ)ions was ensured and also established an in-situ generation of ZIF-L nanoparticles with the polyamide interface,avoiding the formation of interface defects.The in-situ generation of ZIF-L particles increased the roughness of the membrane surface and improved the surface hydrophilicity,providing a water channel for the separation layer and shortening the water transport path.For the Congo red/salt mixed solution,compared with the PEI/TMC membrane without ZIF particle loading,the PEI(ZIF)/TMC membrane maintained the rejection rate unchanged,while the permeability was increased by nearly 17 times,reaching 68.1-71.7L/(m2·h·bar).The Congo red(CR)rejection rate was 98％.The Na2SO4 and NaCl rejection rates were 12.4％and 2.7％,and the separation selectivity coefficients were 7.8 and 36.1,respectively.
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