Novel supramolecular network of graphene quantum dots-vitamin B9-iron (III)-tannic acid complex for removal of chromium (VI) and malachite green

Abstract

The present work is devoted to synthesize graphene quantum dots (GQDs) from waste sugarcane bagasse with average particle size 4.2 nm based on the TEM analysis. The produced GQDs were then aimed to combine with vitamin B9 (folic acid = FA) and Fe3+-tannic acid complex (Fe-TA) for the formation of a novel (GQDs@FA@Fe-TA) supramolecular network with average particle size 37.57 nm and pore diameter 38.35 nm. (GQDs@FA@Fe-TA) was evaluated as a multipurpose nanosorbent for removal of inorganic anionic (Cr(VI)) and organic cationic (malachite green, MG) pollutants from water. Cr(VI) removal was optimized as 99.5% (at pH 3.0 after 5 min), while 94.8% for MG (at pH 6.0 after 30 min). Adsorptions of both pollutants were exothermic and spontaneous and well explained with the pseudo-second order and Langmuir model. (GQDs@FA@Fe-TA) exhibited higher regeneration stability after five consecutive adsorption–desorption cycles (~2.1–4.3% loss). Finally, the potential applications of (GQDs@FA@Fe-TA) for removal of inorganic anionic and organic cationic pollutants from various water samples were 91.2–99.4% and 89.8–92.1% for Cr(VI) and MG, respectively.