Aerosol loading behavior of PVDF nanofiber electret filters using neutrally charged nano- and submicron aerosols was investigated experimentally for the first time. The loading behavior include variations of filtration efficiency and pressure drop and distribution of deposited aerosols in the filters all having the same fiber basis weight (3.060 gsm). Through the filtration efficiency variations of uncharged/charged, single-/multi-layer filters with aerosol loading, it was observed that mechanical PVDF filters had continuously increasing filtration efficiency, while PVDF electret filters had initially decreasing and subsequently increasing filtration efficiency until reaching 100% due to diminishing electrostatic effect and enhancing mechanical effect.

By combining the pressure drop evolution of different filters during aerosol loading and detailed SEM images of the loaded filters, we have demonstrated that multilayer PVDF filters, especially the electret ones, could significantly slow down the pace of filter clogging (skin effect) and elevate the aerosol holding capacity during depth filtration. Generally, the multilayer filters received the most aerosol deposit during depth filtration, whereas the single-layer filters received the most deposit during cake filtration. The multilayer nanofiber filters had approximately 70% aerosol deposit in the filter during depth filtration fully utilizing the full filter thickness, especially for the electret filters that had charged fibers, and only 30% deposit in the cake. On the contrary, the single-layer uncharged/charged nanofiber filters were exactly the reverse due to persistency of the skin effect with only 30% deposit in the filter mostly located in the upstream layer, yet 70% deposit in the cake. During depth filtration, the pressure drop per added mass deposit for the multilayer electret filter was very low at 11 Pa gsm^-1, which was at least twice below any other nanofiber filters. This was all attributed to the uniform capture of aerosols by electrostatic effect across the entire filter depth from the upstream to downstream layers of the multilayer electret filter. The above conclusion was confirmed by the detailed SEM images taken across the different filter layers for the multilayer filter configuration. The 4-layer electret nanofiber filter with a 3.060-gsm basis weight has 4 times more aerosol holding capacity than the single uncharged/charged nanofiber filter with the same fiber basis weight in depth filtration. Based on the standpoint of highest efficiency and capacity with maximum pressure drop 800 Pa imposed on the filtration operation, the 4-layer electret was the best among all 4 filters. It had 52% more aerosol holding capacity than the single layer uncharged filter and 38% more capacity than the charged single-layer and the uncharged multilayer nanofiber filters. The multilayer PVDF electret filters have excellent filtration performance for long-term aerosol filtration and also great potential applications in the fields of personal health care and environmental protection.

首次通过实验研究了使用中性电荷的纳米和亚微米气溶胶的PVDF纳米纤维驻极体过滤器的气溶胶负载行为。加载行为包括过滤效率和压降的变化以及在过滤器中沉积的气溶胶的分布，所有这些都具有相同的纤维基重（3.060 gsm）。通过带气溶胶负载的不带电/带电单层/多层过滤器的过滤效率变化，可以观察到机械PVDF过滤器的过滤效率不断提高，而PVDF驻极体过滤器的过滤效率开始下降，随后逐渐提高，直至达到100％由于减少了静电作用并增强了机械作用。

通过结合气溶胶加载过程中不同过滤器的压降变化和加载的过滤器的详细SEM图像，我们证明了多层PVDF过滤器，尤其是驻极体过滤器，可以大大减慢过滤器堵塞的速度（皮肤效应）并提高过滤速度。深度过滤过程中的气溶胶保持能力。通常，多层过滤器在深层过滤过程中收到的气溶胶沉积最多，而单层过滤器在滤饼过滤过程中收到的灰尘最多。多层纳米纤维过滤器在深度过滤期间充分利用了整个过滤器的厚度，在过滤器中约有70％的气溶胶沉积，特别是对于带有带电纤维的驻极体过滤器而言，仅在滤饼中有30％的沉积。反之，由于皮肤效应的持久性，单层不带电/带电纳米纤维过滤器正好相反，过滤器中只有30％的沉积物大部分位于上游层，而饼中却有70％的沉积物。在深度过滤过程中，多层驻极体过滤器每增加一个质量沉积物的压降非常低，为11 Pa gsm^-1，比其他任何纳米纤维过滤器低至少两倍。这全部归因于通过静电作用从多层驻极体过滤器的上游层到下游层在整个过滤器深度上均匀捕获气溶胶。以上结论由多层过滤器配置在不同过滤器层上拍摄的详细SEM图像证实。具有3.060-gsm单位重量的4层驻极体纳米纤维过滤器的气溶胶保持能力是深度过滤中具有相同纤维单位重量的单个不带电/带电纳米纤维过滤器的4倍。基于最高效率和容量的观点，对过滤操作施加最大压降800 Pa，四层驻极体在所有四个过滤器中是最好的。它的气溶胶保持能力比单层不带电滤嘴高52％，比带电单层和不带电多层纳米纤维滤嘴高38％。多层PVDF驻极体过滤器具有出色的过滤性能，可长期进行气溶胶过滤，并且在个人保健和环境保护领域也具有巨大的潜在应用。