臭氧-CNT膜改性联用工艺对PVDF中空纤维膜污染进程的缓解

Effect of Hybrid Process of Pre-ozonation and CNT Modification on Hollow Fiber Membrane Fouling Control

采用碳纳米管(carbon nanotube,CNT)对聚偏氟乙烯(polyvinylidene fluoride,PVDF)中空纤维超滤膜进行改性,结合臭氧预氧化技术,考察了臭氧-CNT膜改性联用工艺对PVDF中空纤维膜污染进程的缓解作用,研究了CNT负载量和臭氧投量对中空纤维膜组件通量变化和抗污染性能的影响.结果表明,CNT负载量为3 g·m-2、臭氧投量(以O3/DOC计)为0.22mg·mg-1时,临界通量下[144 L·(m2·h)-1],膜组件单位面积过水量达到850 L·m-2,相比原始超滤膜过水量提高了4.5倍;低通量[18 L·(m2·h)-1]下运行15d,膜组件单位面积过水量达到3000 L·m-2,相比原膜单位过水量提高近10倍.使用共聚焦激光扫描电镜观测污染膜表面,结果表明,运行压力增长最快的原膜表面污染层内活菌数量最多;臭氧氧化与CNT膜均能够减少膜表面污染层内的微生物总量和活菌数量,从而缓解了运行压力的增长.臭氧氧化后CNT层的存在,进一步减少了膜表面污染层内的活菌数量,同时截留了部分死菌,但截留的死菌与运行压力增长无明显相关性.

Polyvinylidene fluoride （PVDF） hollow fiber ultrafihration membranes were modified with carbon nanotube （CNT）. Combined with the ozonafion process, the effect of the hybrid pre-ozonation and CNT modification on fouling alleviation was investigated. The impacts of CNT loading mass and ozone dosage on the variation of flux and antifouling ability of the membrane modules were evaluated. Under a critical flux of 144 L. （ m2 ·h） -1 , CNT loading mass of 3 g·m-2, and ozone dosage（ O3/DOC） of 0. 22 mg· mg- 1 , the results revealed that the filtration volume of the hybrid process was promoted to 850 L· m -2, which was about 4.5 times higher than that of the original unmodified membrane. With a flux of 18 L. （ m2 ·h） -1 and 15 day operation, the filtration volume was promoted to 3 000 L·m-2 , which was 10 times that of the unmodified membrane. The fouling membrane surface was observed using confocal laser scanning electron microscopy （CLSM）. The results demonstrated that more living bacteria were present on the membrane surface of the unmodified membrane, which showed a rapid transmembrane pressure （TMP） increase. Both pre-ozonation and CNT modification decreased the total amount of microorganisms and the amount of the living bacteria as well, which mitigated the increase in TMP. After pre-ozonation, the presence of a CNT layer on the membrane surface further decreased the number of living bacteria. Although the CNT layer captured some dead bacteria, it had no obvious relationship with the inerease in TMP.