Sustainable superhydrophobic nanocellulose coatings derived from Gelidium amansii waste via DES extraction and one-pot functionalization.

Gelidium amansii, a red alga widely utilized for industrial agar production, generates significant residual biomass that is often discarded, leading to resource waste and environmental pollution. This research investigates the valorization of Gelidium amansii waste through the development of superhydrophobic materials. High-purity cellulose was extracted using a choline chloride-lactic acid deep eutectic solvent (DES), achieving a yield of 61.17% under optimized conditions (solid-liquid ratio 1:10, 100 °C, 4 h). The extracted cellulose was converted into TEMPO-oxidized nanocellulose (TONC) via enzymolysis and oxidation, with optimal conditions (NaClO volume ratio of 11 mL/g, pH 10.5, 24 h) ensuring high zeta potential stability. The superhydrophobic coating (SHC) with a roughened micro-nano composite structure and a water contact angle of 153.9° was successfully fabricated via a one-pot functionalization process involving TONC, octadecylamine (ODA), and dopamine (DA) hydrochloride under optimized conditions (mass ratio 1:2:2, 50 °C, 16 h). The SHC demonstrated excellent self-cleaning properties and versatility on diverse substrates, including glass, iron, paper, cotton, and filter paper. Applications in oil-water separation and liquid food residue reduction were successfully validated. This research offers a green, scalable approach to enhance the value of Gelidium amansii waste while providing sustainable superhydrophobic materials for environmental and industrial applications.