Nowadays, the fast expansion of the economy and industry results in a considerable volume of wastewater being released, severely affecting water quality and the environment. It has a significant influence on the biological environment, both terrestrial and aquatic plant and animal life, and human health. Therefore, wastewater treatment is a global issue of great concern. Nanocellulose’s hydrophilicity, easy surface modification, rich functional groups, and biocompatibility make it a candidate material for the preparation of aerogels. The third generation of aerogel is a nanocellulose-based aerogel. It has unique advantages such as a high specific surface area, a three-dimensional structure, is biodegradable, has a low density, has high porosity, and is renewable. It has the opportunity to replace traditional adsorbents (activated carbon, activated zeolite, etc.). This paper reviews the fabrication of nanocellulose-based aerogels. The preparation process is divided into four main steps: the preparation of nanocellulose, gelation of nanocellulose, solvent replacement of nanocellulose wet gel, and drying of nanocellulose wet aerogel. Furthermore, the research progress of the application of nanocellulose-based aerogels in the adsorption of dyes, heavy metal ions, antibiotics, organic solvents, and oil-water separation is reviewed. Finally, the development prospects and future challenges of nanocellulose-based aerogels are discussed.

Cellulose is one of the most abundant, widely distributed and abundant polysaccharides on earth, and is the most valuable natural renewable resource for human beings. In this study, three different particle sizes (250, 178, and 150 μm) of Neosinocalamus affinis cellulose were extracted from Neosinocalamus affinis powder using bio-enzyme digestion and prepared into nanocellulose (CNMs). The cellulose contents of 250, 178, and 150 μm particle sizes were 53.44%, 63.38%, and 74.08%, respectively; the crystallinity was 54.21%, 56.03% and 63.58%, respectively. The thermal stability of cellulose increased gradually with smaller particle sizes. The yields of CNMs for 250, 178, and 150 μm particle sizes were 14.27%, 15.44%, and 16.38%, respectively. The results showed that the Neosinocalamus affinis powder was successfully removed from lignin, hemicellulose, and impurities (pectin, resin, etc.) by the treatment of bio-enzyme A (ligninase:hemicellulose:pectinase = 1:1:1) combined with NH3·H2O and H2O2/CH3COOH. Extraction of cellulose from Neosinocalamus affinis using bio-enzyme A, the smaller the particle size of Neosinocalamus affinis powder, the more cellulose content extracted, the higher the crystallinity, the better the thermal stability, and the higher the purity. Subsequently, nanocellulose (CNMs) were prepared by using bio-enzyme B (cellulase:pectinase = 1:1). The CNMs prepared by bio-enzyme B showed a network structure and fibrous bundle shape. Therefore, the ones prepared in this study belong to cellulose nanofibrils (CNFs). This study provides a reference in the extraction of cellulose from bamboo using bio-enzymes and the preparation of nanocellulose. To a certain extent, the utilization of bamboo as a biomass material was improved.

This study explored a green and efficient method for cellulose extraction from corn bract. The cellulose extraction by the CHB (CH3COOH/H2O2/Bio-enzyme) method and the N-CHB (NH3·H2O-CH3COOH/H2O2/Bio-enzyme) method were compared and analyzed. The effect of ammonia pretreatment on cellulose extraction by bio-enzymatic methods was discussed. The results showed that ammonia promoted the subsequent bio-enzymatic reaction and had a positive effect on the extraction of cellulose. Sample microstructure images (SEM) showed that the cellulose extracted by this method was in the form of fibrous bundles with smooth surfaces. The effect of different pretreatment times of ammonia on cellulose was further explored, and cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric (TG) analysis. The results showed that the N3h-CHB (NH3·H2O 50 °C 3 h, CH3COOH/H2O2 70 °C 11 h, Bio-enzyme 50 °C 4 h) method was the best way to extract cellulose in this study. FTIR showed that most of the lignin and hemicellulose were removed. XRD showed that all the cellulose extracted in this study was type I cellulose. TG analysis showed that the cellulose was significantly more thermally stable, with a maximum degradation temperature of 338.9 °C, close to that of microcrystalline cellulose (MCC). This study provides a reference for the utilization of corn bract and offers a new technical route for cellulose extraction.

With the development of science and technology, efficient, fast and green methods are increasingly being pursued.