Preparation of CS@BAC composite aerogel with excellent flame-retardant performance, good filtration for PM2.5 and strong adsorption for formaldehyde

At present, it is still a challenge to prepare an air filtration material with high filter, low pressure drop and good environmental protection. In this study, a porous material with good filtration capacity for PM2.5 and excellent adsorption for harmful gases was developed. Chitosan (CS) was used as the frame matrix, and bamboo activated carbon (BAC) as the functional particles and methyl trimethoxylsilane (MTMS) as the hydrophobic modifier were introduced to the CS system, followed by freeze-dry to achieve the aerogel sheet with high porosity, flame retardant and hydrophobicity. The resulted CS@BAC composite aerogel showed excellent removal ability for both PM2.5 and formaldehyde in the filtration rate of 94.2% for PM2.5 and the formaldehyde adsorption amount of 61.6 mg/g, which was benefited from the dual removal system, the 3D network structure of the CS based aerogel formed during freeze-dry and the high surface area of BAC itself. In addition, the aerogel displayed outstanding flame-retardant property and its total heat release rate (THR) and maximum heat release rate (PHRR) were only 5.30 kJ/g and 28.2 W/g, respectively, the loss on ignition (LOI) value reaching 33.8%. At the same time, after the modification of MTMS, the aerogel realized the transformation from hydrophilic to hydrophobic, which could be used repeatedly.