Hydrophilic Modification Of Polypropylene Hollow Fiber Membrane And Its Anti-contamination In MBR

Membrane bioreactor(MBR)has received extensive attention in water pollution control.Membrane fouling and short service life are still the main reasons that restrict the large-scale popularization of MBR.The main problems are attributed to the low strength of the membrane material and the complex composition of the mixture.Therefore,this paper chooses membrane material with long service life and anti-pollution.In this paper,acrylic acid was grafted onto the surface of polypropylene hollow fiber membrane by continuous UV irradiation.The effect of surface grafting modification was investigated by controlling different grafting reaction conditions such as photosensitizer,monomer concentration,winding speed and cycle times.According to experiments:(1)The photosensitizer played a decisive role in the grafting reaction.Without adding the photosensitizer,there was no grafting reaction.(2)Grafting rate was affected by the monomer concentration significantly.With the increase of grafting monomer concentration,grafting rate increased first and then showed a tendency toward stabilization.The monomer concentration of 30 wt.%was used as the experimental condition of the grafting.(3)Winding speed of the continuous ultraviolet irradiation device had a direct effect on the grafting rate.With the increase of winding speed,the grafting rate increased first and then decreased.The best condition was 3m/min.(4)The number of cycles also had an effect on the grafting rate,and the grafted rate effected by grafting site had a tendency to increase first and then tended to slow.Fouling behaviors of the membrane surface and pores were performed to investigate the effect of different hydrophobic and hydrophilic polypropylene hollow fiber membranes applied in membrane bioreactor(MBR).Under constant flux of 11.5L/m2 h,transmembrane pressure(TMP)varied narrowly between 38 and 53 KPa.A relatively hydrophilic membrane(PP-g-AA)showed the characteristic of lower TMP in comparison with a hydrophobic membrane(PP).Flux recovery(FR)was 30%higher than those of the original PPHFMM.Structural and morphological changes on the membrane surface were characterized by attenuated total reflection-Fourier transform infrared spectroscopy(FT-IR/ATR),electronic universal testing machine,field emission scanning electron microscopy(FE-SEM),atomic force microscope(AFM).The performance of hydrophilic modified PP membrane showed good anti fouling ability.Under the operating conditions with 12 h hydraulic retention time and 2-6 g/L sludge concentration in the MBR,The removal rate of COD and ammonia nitrogen was above 93%and over 90%,and the degradation process was not affected by the modification technology.