Extraction and Characterization of Cellulose from Kelp (Laminaria japonica) Residue

Abstract Kelp residue is the byproduct of industrial production of sodium alginate from kelp. An in-depth utilization of kelp residue not only creates higher economic value but also opens up a new pathway for comprehensive utilization of kelp. In this study, a method of first removing acid-soluble ash and then depleting protein was employed to extract cellulose components from kelp residue. Single-factor experiments demonstrated that treating kelp residue with 1.2 mol/L hydrochloric acid at a solid-liquid ratio of 1:5 effectively removed acid-soluble ash. Subsequently, further treatment with 3% NaOH at a solid-liquid ratio of 1:10, conducted at 100 °C for 140 minutes, reduced the protein content in the extract to below 1%, with a cellulose yield of 33.5%. Fourier transform infrared spectroscopy analysis revealed that characteristic peaks attributed to cellulose existed in the extractive, while electron microscopy observations indicated that the extracted kelp residue cellulose exhibited irregular thin-sheet structures. The cellulose obtained in this study lays the foundation for its further utilization and processing into cellulose-derived products.