Characteristics of cellulose aerogel prepared by using aqueous sodium hydroxide-urea

The highly porous cellulosic aerogels were prepared by freeze-drying method using sodium hydroxide-urea aqueous solution in the process of dissolution, gelation, regeneration and organic solvent substitution. The structural characteristics of porous aerogel were analyzed using scanning electron microscopy and nitrogen adsorption apparatus. As a result, the dissolving pulp was completely dissolved, but filter papers and holocellulose were divided into two layers (dissolved and undissolved parts) in the process of centrifugation. The structure of aerogel from dissolved pulp showed porous pores in the surface and net-shaped network in the inner part. Aerogels from filter paper and holocellulose had the condensed porous network surface and the open-pore nano-fibril network inner structure. Undissolved form of fibers was observed in the aqueous solution of aerogel from holocellulose. The BET value (SBET) of aerogel from dissolved pulp was ranged in 260∼326 m2/g, and it was decreased with the increase of concentration. Whereas, the SBET value of aerogel from filter paper (198∼418 m2/g) was increased with the increase of concentration. The SBET value of aerogel from holocellulose were 137 m2/g at 2% (w/w) of cellulose, and it was increased to maximum 401 m2/g at 4% (w/w) of cellulose. Then, it was decreased at 5% (w/w) of cellulose.