Reusable environmentally friendly electrospun cellulose acetate/cellulose nanocrystals nanofibers for methylene blue removal

Cellulose based nanofibers were developed by electrospinning cellulose acetate (CA) with cellulose nanocrystals (CNC) for efficient removal of methylene blue (MB) dye. The incorporation of 25% (CA-CNC 25%) and 50% CNCs (CA-CNC 50%) improved the physical and chemical properties of CA in the formed nanofibers. Adsorption at an alkaline pH of 10.5 induced deacetylation that enhanced adsorption and reusability of CA-CNC 50%, whose MB adsorption capacity was double that of neat CA. The optimum adsorption conditions using CA-CNC 50% were pH of 10.5 at 40 °C for 5 h, with an initial MB concentration of 25 mg/L. The maximum adsorption capacity of the optimized CA-CNC 50% at 1000 mg/L initial MB concentration was 316.6 mg/g. The CA-CNC 50% maintained MB removal of ≥ 80% for up to 5 cycles. Theoretical modeling and experimental data suggest that the adsorption of MB onto CA-CNC 50% can be described as endothermal chemisorption with pore diffusion being the rate-limiting of the dye mass transfer. The possible interactions that contributed to MB adsorption onto CA-CNC 50% are π-π stacking, electrostatic attraction, and hydrogen bonding, the latter of which came into effect at the onset of deacetylation.