Preparation Of Polysulfonamide Reverse Osmosis Membrane Via Layer By Layer Interface Polymerization

With the rapid development of modern industry and the country's emphasis on environmental protection,China's needs to the efficient use of water resources and deep water treatment are getting higher and higher.Membrane separation technology,especially based on the separation of aromatic polyamide reverse osmosis?RO?composite membrane technology,is a clean and development potential of great separation technology,has become the preferred method of desalination and industrial wastewater treatment.Therefore,high-performance RO membrane material is the key of achieving the breakthrough on new principle and new methods of film technology.Polysulfonamide is considered to be a new generation of membrane material which subvert polyamide RO membrane,due to its structure excellent acid resistance and chemical stability.Multilayer interface polymerization technology is considered a very promising technology in the field of composite materials research and preparation.In this work,we study the preparation of polysulfonamide reverse osmosis membrane by multilayer interface polymerization technology,expecting that the separation performance of polysulfonamide RO membrane can be improved by multilayer interface polymerization.In this paper,the polyethersulfone?PES?ultrafiltration membrane was first coated with 0.3%PVA aqueous solution,and then treated with a similar inter-facial polymer-ization method using piperazine?PIP,0.5%?and naphthalene-1,3,6-trisulfonyl chloride?NTSC,0.03%?to improve the density of the membrane surface.And then implement-ating the multi-layer interface polymerization of PIP and NTSC,achieved the molecul-ar layer-by-layer assembly preparation of polysulfonamide RO membrane separation la-yer.In order to reduce the effect of multi-layer polysulfonamide on the membrane permeability,the preparation of polysulfonamide multilayer composite film was proposed by suspension coating method.The thickness of monolayer polysulfonamide layer was controlled ultilizing the centrifugal force.The suface morphology and chemical structure of this LIP_n assembled PIP-NTSC composite membrane have been characterized through scanning electron microscope?SEM?,atomic force microscopy?AFM?,ATR-FTIR spectroscopy,X-ray photoelectron spectroscopy?XPS?,Zeta potential,optical contact angle?OCA?,ellipsometry and so on.The performance of reverse osmosis membrane was evaluated by the separation performance test of different saline solution.The experimental results show that the polysulfonamide RO membrane has a rejection rate of 98.76%and a flux of 18.96 L/?m²·h?for 2 g/L MgSO₄ aqueous solution at 5 cycles.The rejection rate of Na₂SO₄ reached 99.2%and the flux was 5.89 L/?m²·h?,which achieved the high separation performance of the classical reverse osmosis membrane.And the salt rejection of LBLIP_n assembled PIP-NTSC composite membrane follows the order of R_NaCl<RCaCl2<RMgSO4<RNa2SO4.Experiments found that there was a specific relationship in a certain range between the thickness of the polysulfonamide RO membrane and the assembling cycles.The thickness of the polysulfonamide reverse osmosis membrane increased by 2.67±0.08 nm per layer as the number of layers increased at 1-9 cycles.The results of AFM test show that the surface roughness of LIPn assembled polysulfonamide RO membrane is very low,which is much lower than that of traditional interface polymerization.In the end,this paper has also investigated the preparation of LBLIPn assembled polysulfonamide RO membrane using different amine monomers,such as ethylenediamine,triethylenetetramine and tris-?2-aminoethyl?amine.The LBLIPn assembled PIP-NTSC polysulfonamide RO membrane was post-processed by diazonium salt-induced polymerization?DIAP?,finding that the method of soaking has certain effect on the performance of composite membrane.