Preparation And Investigation Of PVDF-g-PNIPAAm/GO Composite Membrane With Photo-and Thermo-Sensitivity

With the continuous aggravation of water pollution,how to treat wastewater has become a research hotspot.Polyvinylidene fluoride(PVDF)separation membrane has many advantages in wastewater treatment,such as high mechanical strength,no secondary pollution,low energy consumption.However,the practical application scope of PVDF membrane separation is limited,due to its strong hydrophobicity,easily contaminated property,and lack of environment responsiveness.Modification of PVDF separation membrane can not only improve its hydrophilicity and anti-fouling property,but also make it has an environmentally responsive ability.In this paper,we have synthesized the Polyvinylidene fluoride-g-N-Isopropyl acrylamide(PVDF-g-PNIPAAm)by Alkali treatment grafting.Then it was mixed with graphene oxide(GO)which has the photothermal conversion ability to obtain the casting solution,and a composite membrane with thermo-and photo-sensitivity was prepared by immersion phase conversion method.In this paper,the effects of matrix types(PVDF,PVDF-g-PNIPAAm)and GO content on the structure(pore size,porosity and hydrophilicity,etc.)and the heating rate under the Near-Infrared(NIR)illumination of the composite membrane were studied.Furthermore,we studied the thermo-and photo-sensitivity of the composite membrane under different filtrate temperatures and illumination.The results showed that the hydrophilicity and anti-fouling property of the composite membranes were significantly improved after grafting.The addition of GO made the composite membrane can be warm up to exceed 32℃ rapidly(the critical temperature of PNIPAAm)under NIR light irradiation.The composite membrane showed good thermo-sensitivity when the filtrate was changed from 25℃ to 40℃.Meanwhile,the composite membrane also has good photo-sensitivity,the pure water flux of the composite membrane increased by 48%～70% under the illumination of NIR light.And the thermo-and photo-sensitivity of the composite membrane showed good stability in the cycle measurements.Based on the thermo-and photo-sensitivity of the composite membrane,we used NIR light to clean the composite membrane,and the results showed that the “lightcleaning” significantly improved the flux recovery rate of the composite membrane(99.2%).This work extends the study of the controllability and functionality of composite membranes.