Preparation Of Nanofiltration Membranes With β-Cyclodextrin As Aqueous Monomer And Their Applications In Textile Dyeing Effluent Treatment

In recent years,the discharge of printing and dyeing wastewater with high salinity has caused harmful effects on public health and ecosystem.Nanofiltration（NF）membranes are used to remove dyes from wastewater because of their good rejection properties.However,the common NF membranes not only have high rejections for dyes,but also have high rejections for salts.Therefore,the separation of salt and dye cannot be realized,and it cannot meet the requirement of"zero liquid discharge（ZLD）"of wastewater.In addition,low flux is a problem faced in the process of NF membranes research at home and abroad,which limits the application of NF membranes.In term of this,it is imperative to prepare high performance NF membranes for the efficient separation of dye and salt.The properties of NF membranes are related to the materials used to prepare them.Therefore,this paper research introduced economic environmentalβ-cyclodextrin（β-CD）as the aqueous phase monomers to fabricate composite NF membranes by interfacial polymerization（IP）.Ethylene glycol（EG）and glycerin（GI）were add materials.The resultant low-pressure high flux composite NF membranes possessed high rejection of dyes and low rejection of salts.The characterization of composite NF membranes was analyzed and the performance was studied.The NF membranes of add materials with EG and GI were researched.The specific contents of the paper are as follows:The high fluxβ-CD/TMC composite NF membranes were prepared by IP usingβ-CD and trimesoyl chloride（TMC）.Polyether sulfone ultrafiltration membrane was used to support material.Na OH was aqueous phase additive to improve the solubility ofβ-CD.The effects ofβ-CD concentrations in aqueous phase,TMC concentrations in oil phase,Na OH concentrations and heat treatment temperatures on membrane properties were studied in order to optimized the conditions of membrane preparation.FTIR,FE-SEM,XPS,contact angle measuring instrument and Zeta potential analyzer were used for analysis and characterization.The results showed that the characteristic peaks of the ester groups appeared in the FTIR spectra.Zeta potential analysis indicated that the surface charge of composite NF membrane was negative.FE-SEM image structures and contact angle values suggested that when the concentration ofβ-CD was 4.0 wt%,the membrane surface was rough with many wrinkles,and this membrane had better hydrophilicity.At the operation pressure of 0.2 MPa,the pure water flux reached up to 207.8 L·m^-2·h^-1.The rejection of dye Congo red（CR）,Rose bengal（RB）and Reactive brilliant red x-3B（RBRX-3B）were 100.0%,99.1%and 97.7%,respectively.The sequence rejection of salts was Na₂SO₄（45.1%）>Mg₂SO₄（15.6%）>Mg Cl₂（9.1%）>Na Cl（8.5%）.During 6 hours continuous test,the flux exhibited a tendency of decreasing and then stabilizing,and the rejection of CR in the mixture was always higher than 99.1%,while the rejection of Na Cl was lower than 14.7%.The composite NF membranes were prepared with adding EG and GI in aqueous phase.FTIR,XPS,FE-SEM,AFM,contact angle measuring instrument and Zeta potential analyzer were used for analysis and characterization to systematically evaluate the structure and performance of the NF membranes.The composite NF membranes with addition of small molecule alcohol have enhanced hydrophilic performance.Their membrane flux increased,which is about 1.4-1.6 times ofβ-CD4.0/TMC composite NF membrane.Moreover,the NF membranes with adding EG and GI maintained high dye rejection and lower salt rejection.The anti-pollution property of these NF membranes was improved.