Reusability and regeneration of antibacterial filter immobilized zinc oxide nanoparticles on white silica gel beads coated with chitosan

•After we had published the efficacy of ZnO nanoparticles immobilized on white silica beads as an air filter, then we studied further for the reusability and the regeneration which have been not much known in air filter design.•The reusability of ZnO NPs air filter is confirmed by comparing the antibacterial properties with the fresh one.•A simple regeneration of the ZnO NPs air filter is applicable and the air filter is reusable until reaches the exhaustion point.•This article also introduced the methodology of studying particles’ cluster releases from the support. Most antibacterial air filters show good performance for single-use. However, reusable ones are also essential for reducing cost, emergency use, and environmental reduction waste, which are still less attention by researchers. This study investigated the reusability and regeneration capabilities of air filters containing zinc oxide nanoparticles immobilized on white silica gel beads coated with chitosan (ZnOChSi). TEM confirmed nanoparticle size of 11.5 ± 2 nm and dispersed particles. Bacteria-containing spore (Bacillus subtilis) was used to investigate the antibacterial properties of the air filter. The reusable ZnOChSi air filter showed antibacterial properties up to the fourth cycle (4 × 48 h) with >20% efficacy and was no longer practical for the fifth cycle. The regenerated ZnOChSi air filter still performed relatively high antibacterial properties until the third cycle (3 × 48 h) with >50% efficacy and was slowly decreased for continued use. This regeneration test confirmed that the cleansing (heating) method carried out once after 2 × 48 h re-activated the antibacterial properties of the filter. The zinc content release was 1.186 mg/L (0.012% from 10.245 g of the zinc oxide filter).