| The selective separation of dye and salt has always been a difficult issue in the treatment of printing and dyeing wastewater.The development of a new type of dense ultrafiltration membrane to achieve selective separation of dyes and salts is one of the ways to effectively solve this problem.This paper proposes to modify polyethersulfone(PES)/sulfonated polysulfone(SPSf)blend membrane by UV-light grafting method to achieve selective separation of dyes and salts through regulation of membrane pore structure and surface chargeability so as to improve the antifouling performance of membrane.Dimethylaminobenzene methacrylate(DMAEMA)as positively charged monomer and sodium naphthalene sulfonate(VSA)as negatively charged monomer were employed to fabricate a layer of zwitterionic copolymer on the surface of PES/SPSf blend membrane by UV-light grafting.The effect of monomer concentration and radiation time on the properties of the modified membrane were studied.The physical and chemical properties of the membrane were characterize by XPS,ATR-FTIR and EDX analyses.The results showed that the grafting rate raised with the increase of irradiation time and monomer concentration.Meanwhile,the water contact angle of the resultant membrane decayed with the increase of irradiation time and monomer concentration,indicating the enhanced hydrophilicity of the membrane.Simultaneously,it was found that the surface of the membrane deplayed positive charge.It implied that the zwitterionic copolymer was successfully grafted on the membrane surface.Membrane charge can be adjusted by radiation time and DMAEMA concentration(negative,neutral and positive).For instance,when the radiation time is 10 min,the VSA concentration is 25wt%,and the DMAEMA concentration is 15 g/L,the resultant modified membrane(M15)the molecular weight cut-off(MWCO)of 40 kDa,the surface water contact angle of 32°and Zeta potential of +8.56 mV(p H=7).was obtained.Pure water permeability was up to 173 L/m2 h(LMH)bar-1 The retention rates of M15 for positively charged dyes including Alcian Blue(AB 8GX),Basic Blue 24(BB 24),Basic Blue 26(BB 26)and Crystal Violet(MV),were 98.2%,97%,96.3%and 93%,respectively.In addition,the rejection rates for the negatively charged dyes,Evans Blue(EB),Direct Red 23(DR 23),Congo Red(CR)and acid fuchsin(AF)were 93%,92%,97% and 85%,respectively.It suggested that the mixed charged membrane exhibits a high rejection for dyes with positively or negative charge.Conversely,the rejection rates of inorganic salts was lower than 10%.Further,Under the conditions of dye wastewater with a salt concentration of 10 g/L and pH=2-10,the rejection of modified membrane M15 for BB 26 and Na2SO4 are 97% and 6.5%,and the permeation flux still remains at 97 L m-2 h-1 bar-1,showing good operational stability.In order to further improve the selective separation performance of the membrane for negatively charged dyes/salts,GO/PES/SPSf composite membrane was fabricated through layer-by-layer self-assembly.Then,the GO functional layer was further cross-linked and immobilized on the support layer by UV-light radiation for 15 min.The impact of GO loading on the surface morphology hydrophilicity,chargeability and permeation separation performance of the composite membrane was investigated.XRD,Raman,SEM and AFM analyses were used to characterize the composite membrane.XRD analysis results showed that the 110-face diffraction peaks of GO layers disappeared before and after GO UV modification.This inferred that GO layers were chemically crosslinked with the blend membrane film chemically crosslinked.The composite membrane with 202 mg/m2 GO loading(M2)displayed a pure water permeance(53.0 L m-2 h-1bar-1)and a rejection of sodium indigo sulfonate(IC)(87.9%).In the treatment of dye wastewater with different p H values and high salt content,the rejection rate of CR is above 90% showing excellent separation performance and operational stability,and the flux recovery rate is as high as 83%.showing excellent separation performance and operational stability... |
PDF Full Text Request