A multifunctional superhydrophobic coating prepared by extracting chitosan from waste shrimp shells

Facing the challenge of global environmental degradation, developing green, pollution-free, and sustainable renewable raw materials has become an urgent priority. In this study, discarded shrimp shells were used as raw materials. Chitosan (CS) was prepared through chemical extraction, and it was employed as a green basic material to construct multifunctional superhydrophobic coatings. Firstly, graphene oxide (GO) was synthesized via the improved Hummer's method. The composite material of graphene oxide and zinc oxide was prepared by hydrothermal synthesis and was named as GO-ZnO. We successfully transformed the hydrophilic graphene oxide into a hydrophobic material. Finally, a superhydrophobic coating was prepared by using the Schiff base reaction of the GO-ZnO/chitosan mixture with octadecylamine (ODA), and it was named CS-GO-ZnO-ODA., which demonstrated excellent and diverse functionalities. Its water contact angle(WCA) reached as high as 160.4°, with a sliding angle(SA) of 7.2°, exhibiting typical superhydrophobic characteristics. Particularly noteworthy is the coating's significant photothermal effect, with the surface temperature rapidly rising to 59.4 °C under simulated sunlight. The modified cotton fabric exhibited excellent durability, capable of withstanding extreme conditions such as abrasion, washing, and high temperatures. Additionally, the coating also possesses strong antibacterial and dye degradation capabilities, with antibacterial rates exceeding 95% against both E coli and S aureus. Our experiments applied chitosan to a multifunctional superhydrophobic coating, endowing it with capabilities such as self-cleaning, antibacterial activity, photodegradation, de-icing, and oil-water separation. This expands the application of chitosan in the field of superhydrophobicity and provides new insights for preparing outdoor superhydrophobic coatings.