Development of hydrophobic nanocellulose-based aerogel via chemical vapor deposition for oil separation for water treatment

In this study, low density and high porosity aerogels were produced through freeze drying of cellulose nanofiber (CNF) dispersions with 0.6, 0.9 and 1.2 wt% concentration and modified via chemical vapor deposition (CVD) of hexadecyltrimethoxylan (HDTMS) to absorb and remove oil and organic pollutants from the water. Aergels were evaluated by density and porosity measurement, BET analysis, scanning electron microscopy, contact angle, oil absorption capacity and mechanical tests. The densities of unmodified and modified aerogels were in the range of 8.0–13.8 and 11–17.5 mg cm⁻³, respectively. The porosities of aerogels, before and after modification, were 99.1–99.5 and 98.8–99.3%, respectively. The porous structure formation via successful self assembling of CNF was also evidenced by the scanning electron microscopy images. All of the modified aerogels, regardless of the initial CNF concentration, had contact angle values greater than 90° and were classified as hydrophobic materials. The 0.6% sample revealed the highest adsorption capacities of 78.8 and 162.4 g g⁻¹ for motor and cooking oils, respectively and the 1.2% aerogel exhibited the maximum values of stress and Young’s modulus in compression test. The results of this investigation indicated that ultra-light, hydrophob and superabsorbent materials based on chemically modified cellulosic aerogels with this type of silanated material were successfully produced.