| Ultrafiltration technology is a kind of water treatment technology commonly applied in environmental protection engineering.It has many advantages,such as:low cost,high temperature resistance,acid and alkali resistance,separation of particles and impurities in water,virus filtering,and water purification.However,in the actual production process,concentration polarization and blockage of membrane holes are unavoidable phenomena in ultrafiltration technology,which lead to membrane fouling.This will not only reduce the lifetime of the membrane,increase the cost,but also make the separation effect worse,affect the water quality.visible lightcatalytic technology is an emerging clean energy production technology,because it can directly use solar energy to achieve self-degradation,has been applied to the field of environmental pollution control.A photocatalytic ultrafiltration membrane with self-cleaning function was developed by coupling photocatalytic technology with ultrafiltration technology,which is one of the effective means to solve the membrane fouling phenomenon in ultrafiltration technology.In this paper,polyvinylidene fluoride（PVDF）,polyethylene glycol-400（PEG-400）,N,N-dimethylacetamide（DMAc）were used as membrane material,porogen and membrane solvent.Sn O2,Sn O2-g-C3N4,Sn O2-Ti O2were used as additives,using phase conversion method to prepare several Sn O2-based visible light catalytic hybrid ultrafiltration membrane.The effects of PVDF content,PEG-400 content,additive content,stirring temperature and coagulation bath temperature on the performance of ultrafiltration membrane were discussed,and the optimum process parameters of ultrafiltration membrane with high hydrophilicity and pollution resistance were determined.The structure and properties of the membranes were characterized by scanning electron microscopy（SEM）,fourier transform infrared spectroscopy（FTIR）,contact angle analyzer and atomic force microscopy（AFM）.Finally,the anti-pollution and application of the membrane were investigated.The main conclusions are as follows:（1）Sn O2was prepared by homogeneous precipitation method,Sn O2/PVDF ultrafiltration membrane were prepared using Sn O2as additive.The optimal parameters of Sn O2/PVDF ultrafiltration membrane were determined as follows:the optimal content of Sn O2was 0.6 wt%,the optimal content of PEG-400 was 11 wt%,the stirring temperature was65℃,and the coagulation bath temperature was 35℃.Under these optimal conditions,the pure water flux of Sn O2/PVDF ultrafiltration membrane is 236.84 L/（m2·h）,the rejection rate of bovine serum protein is 82.05%,the contact angle is 47.55±0.35°,the surface roughness is Ra=7.603 nm,Rq=10.147 nm,the membrane resistance increasing coefficient is 0.38.（2）Sn O2-g-C3N4was prepared by hydrothermal method,Sn O2-g-C3N4/PVDF ultrafiltration membrane were prepared using Sn O2-g-C3N4as additive.The optimal parameters of Sn O2-g-C3N4/PVDF ultrafiltration membrane were determined as follows:the optimal content of Sn O2-g-C3N4was 0.8 wt%,the optimal content of PEG-400 was 11 wt%,the stirring temperature was 65℃,and the coagulation bath temperature was 40℃.Under these optimal conditions,the pure water flux of Sn O2-g-C3N4/PVDF ultrafiltration membrane is 220.41 L/（m2·h）,the rejection rate of bovine serum protein is 83.67%,the contact angle is57.7±0.1°,the surface roughness is Ra=9.832 nm,Rq=12.384 nm,he membrane resistance increasing coefficient is 0.41.（3）Sn O2-Ti O2was prepared by the sol-gel method,Sn O2-Ti O2/PVDF ultrafiltration membrane were prepared using Sn O2-Ti O2as additive.The optimal parameters of Sn O2-Ti O2/PVDF ultrafiltration membrane were determined as follows:the optimal content of Sn O2-g-C3N4was 0.6 wt%,the optimal content of PEG-400 was 10 wt%,the stirring temperature was 65℃,and the coagulation bath temperature was 35℃.Under these optimal conditions,the pure water flux of Sn O2-Ti O2/PVDF ultrafiltration membrane is 228.69L/（m2·h）,the rejection rate of bovine serum protein is 83.42%,the contact angle is50.65±0.55°,the surface roughness is Ra=11.207 nm,Rq=14.299 nm,the membrane resistance increasing coefficient is 0.52.（4）Using fulvic acid（FA）to simulate contaminated water sources,the pollution resistance and fulvic acid removal ability of traditional PVDF ultrafiltration membrane,Sn O2/PVDF ultrafiltration membrane,Sn O2-g-C3N4/PVDF ultrafiltration membrane and Sn O2-Ti O2/PVDF ultrafiltration membrane were investigated under the condition of visible light or not.Results:under visible light,the pollution resistance of Sn O2/PVDF ultrafiltration membrane is the best,followed by Sn O2-Ti O2/PVDF ultrafiltration membrane,and the pollution resistance of Sn O2-g-C3N4/PVDF ultrafiltration membrane is worse than the first two kinds of membranes,but still better than the traditional PVDF membrane.The pollution resistance of the three hybrid membranes under visible light is better than that without visible light.The FA removal rate of Sn O2-Ti O2/PVDF ultrafiltration membrane was slightly higher than that of Sn O2/PVDF ultrafiltration membrane and Sn O2-g-C3N4/PVDF ultrafiltration membrane,and was better than that of traditional PVDF ultrafiltration membrane.The FA removal rate of Sn O2-Ti O2/PVDF ultrafiltration membrane under visible light irradiation was significantly better than that under the condition of no visible light.The FA removal rates of Sn O2/PVDF ultrafiltration membrane and Sn O2-g-C3N4/PVDF ultrafiltration membrane are slightly lower than those of traditional PVDF membrane,but the FA removal rates of these two kinds of membrane under visible light irradiation are slightly higher than that without visible light irradiation,and the FA removal rates can reach more than 82%.All three kinds of hybrid membrane show good FA removal ability. |
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