Abstract: Recently, expanded polytetrafluoroethylene (ePTFE) nanofibrous membranes have received extensive attention in the treatment of fine particulate matter (PM2.5). But until now, the influence of membrane structure on the PM2.5 filtration process is still under-investigated. And the application of ultra-thin ePTFE nanofibrous membrane in the treatment of PM2.5 of medium-high concentration has received little report yet. Therefore, three kinds of ultra-thin ePTFE nanofibrous membranes with particle/membrane size ratio (dP/dm) ranging from 0.86 to 4.46 and membrane thickness ≤1 μm were chosen to examine the PM2.5 filtration performance at medium to high concentration (200~1000 mg/m3). All the three membranes showed high PM2.5 filtration efficiencies (>99.5%) and low initial pressure drop (30~130 Pa) benefit from the ultra-thin few-layered crosslinked-network-like structures. In addition, the surfaces of ePTFE menbranes were smooth with roughness commonly less than 1 μm, which reduced the adhesion of the cake layer and hence made it prone to fall off. As a result, the membrane exhibited good regeneration performance in a 4-cycle regeneration experiment. From the comparison of the three nanofibrous ePTFE membranes, it showed the one with the lowest dP/dm ratio (0.86) provided the lowest filtration pressure drop (30 Pa) as well as excellent filtration efficiency (99.93%) and good regeneration performance. But further increasing the membrane pore size may lead to more serious pore-plugging and lower filtration efficiency which had fatal impacts on the PM2.5 filtration performance. In summary, the ultra-thin ePTFE nanofibrous membrane exhibited superior comprehensive performance in filtration of PM2.5 at medium to high concentration which showed a broad application prospects in air purification.

Key words: ePTFE, Ultra-thin, Nanofibrous membrane, PM2.5

摘要： 针对中高浓度PM2.5的高效过滤问题，选取颗粒粒径与膜孔径比值(dP/dm)范围为0.86~4.46，厚度小于等于1 μm的三种不同结构的超薄ePTFE纳米纤维膜展开应用性能研究。考察了过滤速度、PM2.5浓度和膜结构对过滤性能的影响以及膜的再生性能。得益于纳米纤维堆叠的网状结构，在过滤速度为1.2~4.8 m/min，进口浓度为200~1000 mg/m3的范围内，三种超薄ePTFE纳米纤维膜均能实现PM2.5的高效截留(>99.5%)，其稳定压降和压降增长速度均随过滤风速和进口PM2.5浓度增加而增加，但初始压降和出口浓度仅随过滤风速增加而增加，与进口浓度关系不大。超薄ePTFE纳米纤维膜层数少、过滤阻力低(≤130 Pa)且膜表面光滑(表面粗糙度小于1 μm)，降低了滤饼与膜表面附着力，使滤饼易于脱落，在4次循环实验中展现出良好的再生性能。横向对比结果显示，dP/dm为0.86，膜厚度为0.5 μm的超薄ePTFE纳米纤维膜兼具最低的过滤压降(30 Pa)、良好的过滤效率(99.93%)及再生性能好的优势，在中高浓度PM2.5空气净化领域表现出较好的应用前景。

关键词: ePTFE, 超薄, 纳米纤维膜, PM2.5