Preparation of electrospun nanofibrous poly(vinyl alcohol)/cellulose nanocrystals air filter for efficient particulate matter removal with repetitive usage capability via facile heat treatment

Air pollution has become a global concern, and numerous studies have focused on developing filters for particulate matter (PM) removal. However, the reusability of air filters, which could lower resources consumption and waste discharge, is also necessary to be investigated. In this study, a water washable electrospun poly (vinyl alcohol) (PVA)/cellulose nanocrystals (CNCs) nanofibrous air filter for PM removal was prepared. The watersoluble polymer composite was converted to be completely water-resistant via a facile heat treatment without adding any crosslinking agent. Our results indicate the increased crystallinity is the key factor to improve the aqueous stability of PVA/CNCs fibers. The CNCs provided additional nucleation sites for PVA crystallization during electrospinning and heating process. By loading 20% CNCs and heating at 140 degrees C for 5 min, the crystallinity degree and crystal size of PVA were increased from 54.7% and 3.3 nm to 85.4% and 6.3 nm, respectively. The reusability of fabricated filters was tested by water washing over 5 cycles. The results show the heavily fouled filters (pressure drop 1000 Pa) were regenerated effectively: the PM2.5 removal efficiency was maintained at above 95%, meanwhile the pressure drop remained less than 100 Pa after repetitive usage (PM2.5 mass concentration > 500 mu g m(-3)). Considering the raw materials are nontoxic and biodegradable, the heating temperature is relatively low, and the process is short, it is a promising green method to manufacture long lifetime air filter.