A versatile TOCN/CGG self-assembling hydrogel for integrated wastewater treatment

Water pollution caused by industrial discharges is a severe threat to our society. Thus, efficient and sustainable materials that can provide potential effective solutions are in high demand. The present work reports the development of a versatile strategy based on TEMPO-oxidized cellulose nanofibers (TOCN)/cationic guar gum (CGG) self-assembling hydrogels to remedy wastewater containing oil, heavy metal ions or organic dyes. The TOCN/CGG hydrogel-coated filter papers, prepared via a layer-by-layer deposition process, show a high oil/water separation efficiency (around 99%), with the coating amount of being as low as 0.032 g m−2 (dry mass). Through gravitational force only, the water flux can be as high as 443 L m−2 h−1. The as-prepared oil/water separation materials exhibited good recyclability. The monolithic TOCN/CGG hydrogel can also efficiently remove copper ions (Cu2+) and dyes (i.e. thioflavin T and methyl orange), based on an adsorption mechanism. The adsorption amount of Cu2+ can be as high as 498.5 mg g−1, while that of thioflavin T and methyl orange can be 430.2 mg g−1 and 134.3 mg g−1, respectively. The mass transfer driving force and the number of active binding sites are the two main factors affecting the adsorption process. This all-polysaccharide hydrogel system may be a promising potential for wastewater remedy, due to its facile/“green” preparation process and high performance, as well as the abundance and environmental-friendliness of its raw materials.