Schiff base crosslinked graphene/oxidized nanofibrillated cellulose/chitosan foam: An efficient strategy for selective removal of anionic dyes

A versatile foam based on Schiff base crosslinking of oxidized nanofibrillated cellulose (ONFC) with amino modified graphene oxide (NGO) and chitosan (CS) was prepared for the efficacious selective removal of anionic dyes. (3-aminopropyl) triethoxysilane (APTES) was employed as a surface modifier to yield an amino modified graphene oxide (NGO). Meanwhile, ONFC was obtained via a periodate oxidation process to produce dialdehyde groups. Thus, the Schiff base crosslinking of ONFC with NGO and CS enabled to be readily accomplished, producing a versatile NGO/ONFC/CS foam. Systematical characterizations confirmed the successful covalent crosslinking and formation of NGO/ONFC/CS foams. Selective adsorption of Allura Red (AR) and orange G (OG) over cationic dye methylene blue (MB) by NGO/ONFC/CS was confirmed. It was found the maximum adsorption capacities of AR and OG at 303 K were 416.7 and 300.5 mg g-1, while it was 14.60 mg g-1 for MB. Thus, the new Schiff base crosslinked NGO/ONFC/CS paves the way for developing versatile graphene based foams in the applications of water treatment.