Structure Regulation Of Interfacial Polymerization Nanofiltration Membranes And Their Application In Treatment Of Dye Containing Wastewater

Nanofiltration（NF）as a new type of membrane separation technology,has been widely used in drinking water purification,sewage treatment,food and medicine and other fields because of high separation efficiency,environmental friendly,and good economic benefits,etc.Polyamide NF membranes prepared via interfacial polymerization is the mainstream products of commercial NF membranes.However,when treating high-salinity printing and dyeing wastewater,problems often occur such as ineffective separation of dye/inorganic salt and easy fouling,limiting the practical application performance.Therefore,it is an urgent need to develop antifouling,high dye/inorganic salt selective separation polyamide NF membranes to realize the recycling of high-value dyes and inorganic salts and improve the long-term stability.To address these problems,this research aimed at regulating NF membrane structures to improve membrane performance.By delicate choosing interfacial polymerization monomers and incorporating of visible light catalytic nanoparticles,loose NF membrane suitable for dye/inorganic salt separation and visible light-driven self-cleaning NF membrane with improved antifouling ability were successful fabricated.The main research contents are as follows:（1）Design and construction of loose nanofiltration membrane with interfacial polymerizationThe hydrophilic polyetheramine（PEA）was selected as monomer,and the polyamide NF membrane（PEA-TMC NFM）was prepared by interfacial polymerization with trimesoyl chloride（TMC）.Hydrophilic PEA has a larger molecular size,which increases the mass transfer resistance of PEA molecules from the water phase to the oil phase,and forms a hydrophilic and loose polyamide membrane structure.It has the good antifouling ability and can realize efficient separation of dye/inorganic salts.The effects of PEA concentration and reaction time on the chemical composition,surface morphology,hydrophilicity,charge,and separation properties of PEA-TMC NFM were systematically studied.The results show that the water flux of the nanofiltration membrane prepared under the optimal conditions is 70.48 L m^-2h^-1,The rejection rates of Na₂SO₄、Mg SO₄、Na Cl、and Mg Cl₂are 29.4%,19.2%,15.6%,11.1%,respectively.The rejection rates of Methyl Blue,Congo Red,Victoria Blue B and Reactive Red195 dyes were 95.98%,95.65%,95.39%,and 98.3%,respectively.the membrane exhibited a high water flux of 66.4 L m^-2 h^-1 at low operating pressure（0.4 MPa）,and showed a high methyl blue rejection（95.4%）and low Na Cl rejection（16.4%）when separating 0.1g L^-1MYB and 1 g L^-1Na Cl mixture solution.It can achieve effective dye desalination.At the same time,PEA-TMC NFM showed good performance stability in the separation of dye/salt mixture for 30h continuous operation.（2）Design and construction of visible light-driven self-cleaning NF membraneFirst,carbon quantum dots（CQD）are prepared using citric acid rich in oxygen-containing functional groups as a carbon source.TiO₂/CQD composite particles（TiO₂/CQD NPs）with a visible light catalytic performance were prepared by hydrothermal method.And FTIR,XRD,TEM,and UV-vis absorption spectroscopy were adopted to systematically characterizations.TiO₂/CQD NPs were added to the PIP water phase,and a high-flux NF membrane with visible light self-cleaning ability（PA-（1-5））was prepared by the interfacial polymerization method.The effects of the introduction of TiO₂/CQD NPs on the surface chemical structure,composition,surface morphology,hydrophilicity,chargeability,selective separation and self-cleaning performance of NF membranes were systematically analyzed.The optimized concentration of TiO₂/CQD NPs amount was 0.035 wt%.Under this condition,the water flux of the self-cleaning NF membrane with TiO₂/CQD NPs reached 67.22 L m^-2 h^-1,increased by about1.8 times,and the rejection of Na₂SO₄ was 96.7%.At the same time,the rejections to congo red and methyl blue of self-cleaning NF membranes were 99.8%and 99.1%,respectively.After 72h of continuous filtration of 100 ppm MYB solution,the NF membrane was taken out and exposed to visible light for 1 h.Compared with the NF membrane without TiO₂/CQD NPs,the blue color of the self-cleaning NF membrane disappeared significantly.The results proved that the prepared NF membrane had a good visible light self-cleaning performance.During the cyclic fouling-photodegradation test,the water flux of the prepared visible light self-cleaning NF membrane could be recovered and maintained a stable MYB rejection,exhibiting excellent stability.In summary,this work focuses on improving the permeate-selectively and antifouling performance of NF membrane.By selecting the monomers and incorporating functionalized inorganic nanoparticles,the membrane structure and performance of NF membrane can be optimized,and the relationship between the membrane structure and performance was revealed.The work opens an avenue to the preparation of high performance NF membranes.