Preparation And Characterization Of PES Antibacterial Ultrafiltration Membrane Containing HNTs Loaded With Silver Nanoparticles

At present, most ultrafiltration membranes have poor antibacterial activities, and they are easy to be polluted by bacteria, which might lead to worse permeability performance of the membranes and will have a bad effect on the efficiency and service life of the membranes. To solve these problems, halloysite nanotubes(HNTs) were chosen as carrier to load nano-silver through some method, which was then blended with polyethersulfone(PES) to prepare hybrid antibacterial ultrafiltration membranes and improve the membrane anti-biofouling performance. The main contents are as follows:(1) Preparation and characterization of PES/HNTs hybrid ultrafiltration membranes:Membranes with different HNTs contents were prepared using PES as membrane material, HNTs as hydrophilic additives, and the effects of adding HNTs on the separation performance, hydrophilicity, microstructure and surface morphology of membranes were characterized. The results showed that the hydrophilicity of membranes were enhanced through adding HNTs, and higher HNTs content resulted in increase of membrane flux, but the rejection against PEG20000slightly changed, which indicated that the membranes had a better rejection effect. As can be seen from the results of scanning electron microscopy (SEM) and atomic force microscope (AFM) that it improved the interconnectivity of the finger-like pore in the membranes by adding HNTs, and the cortex on the top surface of the membranes were thinner, what’s more, it also resulted in decrease of roughness on the membrane surface, which would be hopeful to improve the membrane anti-biofouling performance. Therefore, HNTs can be used as hydrophilic material and it could play an important role in improving the membrane flux.(2) Preparation and characterization of CS-HNTs-Ag/PES hybrid antibacterial ultrafiltration membranes:Modification on the surface of HNTs was carried out using chitosan(CS), then the modified HNTs were loaded with nano-silver, finally, CS-HNTs-Ag/PES hybrid antibacterial ultrafiltration membranes with different additives contents were obtained, and the effects of adding CS-HNTs-Ag on the properties of the membranes were characterized. HNTs before and after modification were characterized using Fourier Transform infrared spectroscopy(FTIR), thermogravimetry(TG) and Transmission Electron Microscope(TEM), and the results showed that the modification was carried out successfully, furthermore, nano-silver could be seen cleraly on the surface of HNTs. As can be seen from the results of ultrafiltration experiment, the pure water flux of the membranes increased doubly through adding CS-HNTs-Ag, meanwhile, the rejection only decreased a little, so the membranes still had good rejection performance. As can be seen from the results of SEM and AFM, the membranes after adding CS-HNTs-Ag had the similar microstructure and surface morphology with membranes after adding HNTs. The results of antibacterial experiment showed that membranes after modification had good antibacterial activity against E. coli and S. aureus, and the antibacterial rates of the membranes against the two bacteria were94.0%and92.6%, respetively.(3) Preparation and characterization of P4VP-HNTs-Ag/PES hybrid antibacterial ultrafiltration membranes:Firstly, poly(4-vinylpyridine)(P4VP) was grafted onto the surface of HNTs through a series of reactions, then, the modified HNTs were loaded with nano-silver, finally, P4VP-HNTs-Ag/PES hybrid antibacterial ultrafiltration membranes with different additives contents were obtained, and the effects of adding P4VP-HNTs-Ag on the properties of the membranes were characterized. HNTs before and after modification were characterized using FTIR, TG and TEM, and the results showed that the modification was carried out successfully, furthermore, nano-silver could be seen cleraly on the surface of HNTs. The results of the membranes showed that the membranes prepared using this method had the similar microstructure and surface morphology with CS-HNTs-Ag/PES membranes, meanwhile, they had the similar change law of the separation performance, but P4VP-HNTs-Ag/PES membranes had better antibacterial activity against E. coli and S. aureus, and the antibacterial rates of the membranes against the two bacteria were both almost100%.The above research was hopeful to combine the special properties of HNTs with the advantages of membrane separation technique and expand their application in water treatment field.