Extraction and preparation of cellulose nanocrystals from dealginate kelp residue: structures and morphological characterization

We present the first report on the extraction and structure of cellulose nanocrystals (CNCs) from waste kelp residue after alginate extraction. CNCs were successfully prepared from this species of brown algae residue at a 9.6 % yield by a series of procedures involving swelling treatment, residual alginate isolation, ultrasonic smashing, bleaching, delignification and sulfuric acid hydrolysis. The high aspect ratio of CNCs with a crystallinity index of 74.5 % was observed by X-ray diffraction, transmission electronic microscopy and atomic force microscopy. Results clearly indicated that the selected multiple-step procedures provided the possibility of chemical cleavage of non-cellulosic components of kelp structure and then of fabrication of CNC nanowhiskers. Interestingly, stable aqueous and ethanol colloidal suspensions were determined by zeta potential measurement. In addition, porous CNC aerogels with interconnected fibrillar open networks were finally prepared using a freeze-drying process. This work mainly aimed to reuse industrial deaglinate kelp residue, giving it a useful application and preventing its role as an environmental pollutant.