Synergy Effects Of External Electric Field On Modification Ultrafiltration Membrane By Plasma

This paper studies the synergistic effect of an external electric field on the ultrafiltration membrane modified by low temperature nitrogen plasma.The polysulfone?PSF?ultrafiltration membrane was selected as the experimental object,modified under different electric field positions,voltage,discharge power,and processing time,and the pro-ultrasonic membrane was characterized by measuring the contact angle before and after the modification of the PSF ultrafiltration membrane.Water properties,determination of parameters such as pure water flux and BSA flux,etc.The separation and anti-contamination capabilities of the PSF ultrafiltration membrane were investigated;the surface morphology of the membrane was observed using a scanning electron microscope?SEM?;the emission spectrum method and the Langmuir probe method were used.The real-time diagnosis of the low-temperature nitrogen plasma modification process was performed,and characteristic parameters such as electron temperature and electron density of the nitrogen plasma were obtained.Research indicates:?1?The optimal conditions for applying PSF ultrafiltration membrane with an external electric field in combination with low temperature nitrogen plasma are:electric field position 30cm,voltage 70V,discharge power 80W,processing time 90s,system pressure20Pa.The contact angle of the PSF ultrafiltration membrane located 30 cm from the discharge center was reduced from 80°of the original membrane to 24°,which is lower than the 44°of the contact angle of the plasma-modified PSF membrane with respect to the non-added electric field.Improve the hydrophilicity of PSF ultrafiltration membrane,and the effect of applying an electric field in conjunction with plasma-modified PSF ultrafiltration membrane is better.?2?Pure water flux and bovine serum albumin?BSA?flux of PSF ultrafiltration membrane modified by an external electric field combined with low-temperature nitrogen plasma are 19 L/?m²·min?and 7 L/?m²·min?of PSF original membrane flux increased to31 L/?m²·min?and 22 L/?m²·min?,respectively;flux decay rate and pollution rate were reduced from the original film by 66%?54%to 31%?22%,respectively;The rejection rate for BSA increased from 72%of the original membrane to 95%.After the application of an external electric field in combination with a nitrogen plasma treatment,the separation ability and anti-pollution ability of the PSF ultrafiltration membrane are significantly enhanced.The SEM photographs show that the etching of the surface of the PSF film is weakened by the low-temperature nitrogen plasma under the combined action of the external electric field.?3?The nitrogen plasma emission spectrum consists of N-ion lines(N_II,N_III,N_IV,N_V,etc.)with different valence states.The peak positions are concentrated in the range of330-440 nm,and the highest peak occurs at 355.9 nm.The plasma electron temperature and electron density were 2.1×10⁴K and 5.3×10¹⁵m^-3,respectively,during the application of an external electric field in combination with a low-temperature nitrogen plasma to modify the PSF ultrafiltration membrane.The ultrafiltration membrane was treated under the optimal modification conditions,and the plasma electron density was measured.Appropriately increased,moderate particle activity,complete free radical reaction on the surface of the membrane,and the ability to generate more polar groups to improve the hydrophilicity of the ultrafiltration membrane.