A Facile Method for Processing Durable and Sustainable Superhydrophobic Chitosan-Based Coatings Derived from Waste Crab Shell

The substitution of synthetic raw materials with renewable feedstock is fueling a lot of interest to drive new scientific and technical advancements that underpin this strategy. In this context and looking at the broad prospect of chitosan, herein, we proposed a facile, economical, and novel strategy to process high-yield (44% ± 3) chitosan from waste crab shells and apply the processed chitosan to fabricate a durable, multifunctional, ecofriendly superhydrophobic coating. The coating was developed by binding the amines of chitosan and a long-chain polymer, octadecylamine using a cross-linking agent (glutaraldehyde). Applying the coating onto intrinsically hydrophilic polyester fabric and typical surgical-grade cotton yielded superhydrophobic materials with water contact angles of 158.6 and 161.4° (± 3), respectively. A preliminary study revealed that the coating could endure multiple cycles of laundry (60×), sandpaper abrasion (55×), and tape peel test (80×) with little diminution in the superhydrophobic property. Interestingly, any decrease in the superhydrophobicity could be restored after ironing the fabrics for 2 min, indicating that the effect was reversible. Furthermore, the coating could transform an ordinary hydrophilic polyurethane sponge into an excellent superhydrophobic–superoleophilic absorbent, which can rapidly absorb and separate a variety of organic solvents and oils from oil/water mixtures.