Chemical Process Equipment Preparation And Characterization Of Nanomaterials Modified Composite Nanofiltration Membranes

Nanofiltration（NF） membrane technology is a kind of separation technology whose separation performance is between ultrafiltration membrane and reverse osmosis membrane process.Due to its unique structure and separation characteristics,NF technology has been widely used in many fields such as seawater desalination,drinking water treatment,food processing,medicine and health,desalination and concentration,etc.,and has become a research hotspot of membrane technology.At present,low water flux and poor anti-pollution ability exist in NF all over the world,which limit the application of NF technology.As we all know,the core of NF technology is NF materials,so it is particularly important to prepare good performance NF materials.The research of this thesis is based on the overview of NF,the polyamide active layer were successfully fabricated via interfacial polymerization technique on PES substrates,which were formed by the reaction of piperazine（PIP）with different kinds of nano-materials and trimesoyl chloride（TMC）.The corresponding results were obtained as follows:Using PIP and TMC as aqueous and oil-phase monomers respectively,sulfonate modified graphene oxide（SGO）was uniformly dispersed in aqueous solution.The composite NF membrane modified by SGO was prepared by interfacial polymerization on the PES support.The optimum condition for membrane preparation was determined by investigating the effects of different concentrations of SGO on the membrane structure and properties.The properties of the composite NF membrane were systematically evaluated by FTIR,XPS,SEM,AFM,contact angle,zeta potential and so on.The prepared polyamide composite membrane has enhance the hydrophilicity,pure water flux,anti-fouling ability,and had an effective separation of monovalent and divalent salts-the rejection of Na Cl was 21.96% and the rejection of Na₂SO₄ was 98.99%.In order to make the nano-materials exist in the membrane stably,amine modified graphene oxide（NGO） was used as the additive material in the aqueous to make the amino in NGO and PIP react with the acyl chloride group at the same time to prepare the NGO modified composite NF membrane（PA-NGO）.The membrane structure and properties were evaluated by FTIR,Raman,TEM,contact angle and separation test systematically.The crosslinking degree,hydrophilicity and water flux of the composite membrane has increased,and the thickness has decreased.In order to make the composite NF membrane has a self-cleaning ability,carbon nitride（C₃N₄）with photocatalytic function was selected as the aqueous phase additive material to prepare C₃N₄ modified composite NF membrane（PA-C₃N₄）by interfacial polymerization.The optimum conditions for membrane preparation were gained by adjusting diffusion coefficient and adding quantity.The PA-C₃N₄ membrane had excellent performance for divalent salt rejection,and the pure water flux was 6 times that of the original NF membrane.Methylene blue solution was used to carry out experiments on dye interception and photocatalytic self-cleaning ability of PA-C₃N₄ membrane.The composite NF membrane showed great interception performance（>97%） and photocatalytic self-cleaning ability.