Inorganic salts mediated manipulation of physicochemical properties of cellulose aerogels

Cellulose aerogels with high surface area and better pore characteristics have attracted considerable attention due to their interesting properties such as biodegradability, biocompatibility, etc. By virtue of these important properties, cellulose aerogels have found applications in various important areas including dye adsorption. In this study, alkali and alkaline metal chloride salts with different cationic radii (LiCl, NaCl, KCl, MgCl₂, and CaCl₂) were used to manipulate the specific surface area and pore characteristics of cellulose aerogels. The effect of salt addition on the sol-gel transition of cellulose solutions and the physicochemical properties of aerogels developed thereof were studied. The results showed that the salts with lower cationic radii (LiCl and MgCl₂) significantly reduced the sol-gel transition time thereby inducing faster gelation of cellulose solutions compared to those with larger cationic radii (KCl). Moreover, salts with lower cationic radii led to aerogels with higher specific surface area and lower porosity whereas salts with higher cationic radii led to lower specific surface area and high porosity. The aerogels with higher specific surface area were cationized to introduce positively charged sites and used for dye adsorption study. The dye adsorption study showed that cationic functionalization of aerogels with higher specific surface area adsorbed anionic dye faster than those with lower specific surface area which could be attributed to the higher number of available adsorption sites in the aerogels. This study is important as it sheds light on the effect of salts’ cationic radii on the surface area and porosity characteristics of cellulose aerogels, which could be used as a means to tailor these characteristics for specific applications.