A comprehensive review of cellulose nanomaterials for adsorption of wastewater pollutants: focus on dye and heavy metal Cr adsorption and oil/water separation

Cellulose is widely distributed in higher plants and constitutes the most abundant natural biopolymer on Earth. Nanocellulose is a cellulose material with nanoscale dimensions, obtained through special processing and treatment. Up to now, nanocellulose has been widely investigated as a biosorbent to absorb various types of pollutants in wastewater due to its excellent properties, such as large specific surface area, antifouling behaviour, high aspect ratio, high heat resistance, excellent mechanical properties, biodegradability and biocompatibility. In addition, nanocellulose can be rationally structured by different recombination techniques such as membranes, sponges, aerogels, hydrogels and microspheres and provide specialised functionality for the adsorption of various types of pollutants from wastewater. This review introduces the basic properties, classification and modification methods of nanocellulose; discusses the preparation strategies of nanocellulose-based recombinant materials (including vacuum/pressurised filtration, sol-gel and electrospinning); reviews research progress in the adsorption of organic dyes and heavy metal Cr, as well as the separation of oil/water using nanocellulose-based recombinant materials; and explores the potential of nanocellulose in treating tannery wastewater. Finally, the problems faced by nanocellulose-based recombinant materials and future prospects are presented.