Separation Properties Of Nanofiltration Membranes Based On Halloysite Nanotubes

In the modern industries such as biochemistry,pharmaceutical,printing and dyeing,the practical problems of salt-containing organic wastewater treatment often appear.Nanofiltration membrane technology has been widely used in this field as a new separation technology.The halloysite nanotube is a natural silicate mineral with a hollow tubular structure and a large amount of-OH functional groups on the surface,which has better dispersibility and suitable for water treatment than conventional nanoparticles such as carbon nanotubes and montmorillonite.In this paper,nanofiltration membranes for salt-containing dye wastewater were prepared by using halloysite nanotubes as a material and polyacrylonitrile?PAN?membrane as a base membrane by evaporation self-assembly and interfacial polymerization.The main research contents of the thesis are as follows:?1?Preparation and properties of evaporative self-assembled m-Ag/HNTs/PAN nanofiltration membranesThe nano-functional materials of halloysite nanotubes?Ag/HNTs?loaded with silver nanoparticles?Ag NPs?were prepared by repeated vacuum impregnation and high-temperature calcination.The material was then modified with poly?styrene sulfonate??PSS?and blended with polyvinyl alcohol?PVA?solution to prepare m-Ag/HNTs/PAN nanofiltration membranes by evaporation self-assembly.The results show that Ag NPs can be uniformly loaded in the inner and outer of HNTs,and m-Ag/HNTs can be oriented regularly on the surface of the hydrophilic PAN membranes.The addition of m-Ag/HNTs can control the thickness of the selected layer.The obtained m-Ag/HNTs membranes has good dye/salt separation performance and antibacterial property,and the m-Ag/HNTs-8 membranes has the best comprehensive performance,and the water permeability is 66.6 L?m^-2?h^-1,the rejection of chrome black T and methyl blue is 99.7%and 96.8%,respectively,and the antibacterial performance is 100%.?2?Preparation and properties of interfacial polymerization m-HNTs/PAN TFN nanofiltration membranesThe HNTs was modified by PSS to obtain m-HNTs and were mixed with the monomer piperazine?PIP?and the polymer PVA to prepare an aqueous phase solution.In order to avoid the loss of the nanoparticles during the removal of the aqueous liquid,a cushion layer was first obtained by vacuum filtration,and a HNTs-incorporated polyamide selective layer was constructed by interfacial polymerization between PIP and 1,3,5-benzenetricarbonyl trichloride?TMC?.Thus,Thus,m-HNTs/PAN TFN nanofiltration membranes were obtained.The results indicated that the modification of m-HNTs with PSS have good dispersibility and do not affect the intrinsic nanostructure of HNTs.The obtained m-HNTs/PAN TFN nanofiltration membranes has a negative charge?pH=7,?=-83.8 mV?in a wide pH range of 4-10.The surface hydrophilicity and water permeability of the TFN membranes increased significantly and the rejection of Na₂SO₄ was above 97.5%.Among them,the TFN-0.05 membrane has a superior separation performance:water permeability of 34.5 L?m^-2?h^-1?bar^-11 and Na₂SO₄rejection of 97.8%at 4 bar.Compared with TFC membrane,the water permeability of the membrane increased by 78.6%,the salt rejection was not affected,and show an excellent operational stability and antifouling performance.