Seaweed residue as a low-cost source for producing cellulose nanofibrils with ultraviolet shielding properties.

Seaweed residue (SR) is an industrial by-product produced during seaweed extraction, which is generally used in feed processing with low added value and cheap price (<0.2 $ per kg). In this study, we reported that Nano Seaweed residue fibers were extracted from seaweed residue, and SR-CNF was prepared by pretreatment of SR with oxalic acid (OA) dihydrate combined with an assisted ultrasonic disintegration method. The effects of different OA contents on the yield and physicochemical properties of SR-CNF, as well as the potential value of the application of seaweed residue-based biocomposite films were investigated in the pretreatment system. It has some reference value for the exploration of algal residue-based nanofiber preparation. Using the casting method, the SR-CNF was used as the reinforcing material, and the algal residue-based composite film was prepared with an elongation at break of 83.2% and a tensile strength of 12.9 MPa. The film has good light transmittance, and it also possesses moderate tensile strength as well as excellent UV protection. Of particular interest is that this UV shielding effect is entirely derived from the natural color-emitting groups within the material, a unique property that makes the composite film have great application prospects in the field of food packaging.