| Nanofiltration(NF)technology has played a important role in household tap water purification.The current research attention has been paid to develop NF membranes with high flux and salt rejection.At the present stage,NF membranes are mainly fabricated by the interfical polymerization method,where a thin and dense selective layer on top of a porous substrate is formed by an interfacial polymerization between an organic phase containing Trimesoyl chloride(TMC)and an aqueous phase having amino chemicals such as piperazine(PIP),polyethyleneimine(PEI),m-phenylenediamine(MPD),etc.Moreover,other chemicals such as polyhydroxy monomers have also been added in the water phase to enhance the membrane water flux by increasing the hydrophilicity of the interfacial polymerization(IP)layer.In this paper,some polyhydroxy compounds are used in the water phase to react with TMC in the organic phase.A serious thin film composite membranes using polyether sulfone(PES)as the substrate have been successfully prepared.By carefully adjusting the composition of the water phase and the IP condition,the separation performances of the composite nanofiltration membranes have been optimized.When a glycerol and β cyclodextrin(β-CD)mixed water solution was used as the aqueous phase,a pure water flux(PWF)of 30.21 L·m-2·h-1,and the rejection of Na2SO4 was 84.13%was obtained by tuning the compositions of the water phase and the concentration of the TMC hexane solution.In the 72 h NF test,the initial flux of the membrane was significantly reduced due to the compaction effect,and became stable at the rest of the experiment.By adding triethanolamine(TEOA)to the water phase,the Na2SO4 rejection of the NF membrane further increased to 93.88%,and the pure water flux reduced to 24.35 L·m2·h-1.The separation performance of the membrane remained stable during long-term operations.In order to further increase the flux and maintain a high rejection rate,mannitol and P-CD solution was used as the water phase in the IP reaction.The pure water flux of the composite nanofiltration membrane increased to 27.80 L·m-2·h-1,and the Na2SO4 rejection rate increased to 97.34%.During a 72 h NF test,the water flux of the NF membrane remained stable.In the oxidation resistance test,the chlorine resistance strength of the composite NF membrane synthesized using mannitol reached 12000 ppm·h. |
