对采集的PM2.5进行预处理，将滤膜浸入在含有150ml超纯水的烧杯中

The collected PM2.5 is pretreated, the filter membrane is immersed in a beaker containing 150ml ultrapure water, and ultrasonic treatment is performed on an ice bath for 1 hour until no PM2.5 remains on the filter membrane. Then put the extracted mixture into a -80° refrigerator to freeze and then put it into a vacuum freeze dryer for drying to finally obtain PM2.5 flocculent particles.

The collected PM2.5 is pre-treated, the membrane is immersed in a be cup containing 150 ml of ultra-pure water, and ultrasound is processed on the ice bath for 1 hour until there is no PM2.5 residue on the membrane. Then put the extracted mixture into the -80 degree refrigerator frozen and then put into the vacuum freezer dryer for drying and finally get PM2.5 floc-like particles.

The collected PM2.5 was pretreated, the filter membrane was immersed in a beaker containing 150ml ultra pure water, and ultrasonic treatment was conducted on the ice bath for 1 hour until there was no residual PM2.5 on the filter membrane. Finally, PM2.5 flocculent particles were obtained by freezing the mixture in - 80 ° refrigerator and drying in vacuum freeze dryer.<br>