Preparation Of O-MoS₂-based Membrane Modified Composite Nanofiltration Membrane And Study On Treatment Of Dyestuff Wastewater

Nanofiltration technology is widely used in the treatment of various wastewaters.Ideally,the nanofiltration membrane should have high flux,high salt rejection（divalent salt）,high antifouling and oxidant resistance as much as possible.In order to more targetedly remove special pollutants in sewage,it is necessary to independently develop and prepare membranes with better performance.The treatment of wastewater containing dye molecules has received much attention in recent years.In order to better deal with this kind of sewage,in this paper,the two-dimensional sheet material O-MoS₂ was modified as a new filler to prepare the ultrafiltration membrane substrate and the base membrane modified nanofiltration membrane.The morphology,structure,physicochemical properties and separation performance of the prepared modified composite membrane were systematically studied through membrane characterization analysis,separation performance evaluation,treatment application in simulated dye wastewater and stability performance test.Research indicates:（1）The composite O-MoS₂ ultrafiltration membrane substrate was prepared by phase inversion method.The results showed that the appropriate nanomaterial loading was beneficial to improve the pore structure of the membrane and to adjust the pore size of the membrane substrate and the morphology of the membrane pores.When the O-MoS₂ content was 0.06wt%,the pore size of the ultrafiltration membrane changed from irregular bubble-like pores to long finger-like pores running through the membrane matrix.At the same time,the performance study of the ultrafiltration membrane showed that the pure water flux of the PSf/O-MoS₂-6wt%membrane reached 356.5 L m^-2 h^-1,the MWCO was 73,276Da,and the BSA rejection rate was92.3%,all higher than Control membrane PSf-0 membrane(water flux:156.6 L m^-2 h^-1,BSA rejection:87.21%,MWCO:113,450 Da).（2）The nanofiltration membrane with asymmetric structure was prepared by interfacial polymerization on the prepared ultrafiltration membrane substrate.Through the characterization of TEM,SEM,AFM,etc.,the results showed that in addition to the change in the pore size of the substrate membrane,which affected the filtration performance of the nanofiltration membrane,the change in the properties of the nanofiltration membrane was also related to the exposed O-MoS₂ particles on the surface of the membrane,which improved to a certain extent.The roughness,hydrophilicity and electronegativity of the films were determined.The best pure water flux obtained by the nanofiltration membrane F6 with the best performance was 64.81L m^-2 h^-1,which was 76.05%higher than that of the control PSf membrane;the rejection capacity of salt was also improved.On the other hand,the change of the pore morphology of the substrate membrane endows the nanofiltration membrane with stronger mechanical properties.In the filtration performance test of simulated dye wastewater for 120 hours,the performance of membrane F6 changed little,the water flux attenuated by 10%,and the retention performance did not change significantly.Compared with membrane F0（water flux attenuated by 27%）,the filtration performance significantly more stable.（3）The modified nanofiltration membrane was used to simulate the treatment of dye wastewater.Through the test,the best performance of the composite membrane F6in the treatment of simulated dye wastewater（CB and RB）,the water flux reached 43.2L m^-2 h^-1 and 43.7 L m^-2 h^-1,respectively,an increase of 32%and 37%,and the dye rejection was increased to 99.41%and 99.99%,respectively,compared with the control membrane.For more complex simulated dye wastewater conditions,that is,salt/dye mixed solution,with the increase of salt ion concentration,the change in the performance of modified membrane F6 had little effect.The O-MoS₂ modified composite nanofiltration membrane had better adaptability and superior performance in the treatment of wastewater under complex conditions.It provided a broader prospect for the actual sewage treatment in the future.