Abstract
The complex aerogel generated from nano-polysaccharides, chitin nanocrystals (ChiNC) and TEMPO-oxidized cellulose nanofibers (TCNF), and its derivative cationic guar gum (CGG) is successfully prepared via a facile freeze-drying method with glutaraldehyde (GA) as cross-linkers. The complexation of ChiNC, TCNF, and CGG is shown to be helpful in creating a porous structure in the three-dimensional aerogel, which creates within the aerogel with large pore volume and excellent compressive properties. The ChiNC/TCNF/CGG aerogel is then modified with methyltrichlorosilane (MTCS) to obtain superhydrophobicity/superoleophilicity and used for oil–water separation. The successful modification is demonstrated through FTIR, XPS, and surface wettability studies. A water contact angle of 155° on the aerogel surface and 150° on the surface of the inside part of aerogel are obtained for the MTCS-modified ChiNC/TCNF/CGG aerogel, resulting in its effective absorption of corn oil and organic solvents (toluene, n-hexane, and trichloromethane) from both beneath and at the surface of water with excellent absorption capacity (i.e., 21.9 g/g for trichloromethane). More importantly, the modified aerogel can be used to continuously separate oil from water with the assistance of a vacuum setup and maintains a high absorption capacity after being used for 10 cycles. The as-prepared superhydrophobic/superoleophilic ChiNC/TCNF/CGG aerogel can be used as a promising absorbent material for the removal of oil from aqueous media.
Highlights
Wastewater generated from different industrial processes, oil production, and transportation has become a worldwide problem as it creates ecological problems posing a great threat to the environment, human health, and national development [1]
One end of a tube was fixed at the center of the modified chitin nanocrystals (ChiNC)/TEMPO-oxidized cellulose nanofibers (TCNF)/cationic guar gum (CGG) aerogel, while the other end of the tube was connected to a vacuum system
Cellulose fiber was first extracted from velvetleaf, known as Abutilon theophrasti or Chinese jute, and TEMPO-oxidized to obtain TCNFs, in which the OHs at the C6 position were converted into carboxylic groups
Summary
Wastewater generated from different industrial processes, oil production, and transportation has become a worldwide problem as it creates ecological problems posing a great threat to the environment, human health, and national development [1]. Cellulose and chitin are the most abundant polysaccharide polymers in the earth, which can be found in many different plants, some animals, fungi, and bacteria [18,19] They are consisted of both crystalline and amorphous domains, though the amorphous region can be removed by using a controlled acid or enzymatic hydrolysis, or an oxidation reaction by using. We have previously reported a method to prepare complex membranes with porous structures by mixing oppositely charged polyelectrolytes generated from polysaccharide materials, which exhibited good performances in separating oil–water emulsions [46,47]. We further explore this method to fabricate porous complex aerogels using polysaccharide-based nanomaterials and study their absorption performances. A total of 5 g of the bleached fibers were suspended in water (500 mL) containing TEMPO (0.1 g) and sodium bromide (1.0 g). The yield of resultant ChiNC was determined to be approximately 66%, and the final product was stored in DI resultant ChiNC was determined to be approximately 66%, and the final product was stored in DI water until further use or characterization
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