Selective Adsorption and Separation of Organic Dyes Using Functionalized Cellulose Nanocrystals
writer：N. Mohammed, H. Lian, M.S. Islam, M. Strong, Z. Shi, R.M. Berry, H-Y. Yu, K.C. Tam
keywords：cellulose
source：期刊
Issue time：2021年
In this study, cellulose nanocrystals (CNCs) were evaluated as potential adsorbents for the selective adsorption and separation of organic dyes mixtures (methylene blue (MB), with either methyl orange (MO) or rhodamine b (RB) or crystal violet (CV)).The role of surface functional groups on the dye-CNC interaction was examined using pristine and surface-functionalized CNCs, such polydopamine (PD) and melamine-formaldehyde (MF) coated CNCs (PD-CNCs and MF-CNCs respectively). Batch adsorption studies on MB/MO dye mixture showed that pristine CNCs bearing anionic sulfate ester groups exhibited preferential adsorption for MB, with a 93.67% separation efficiency. This was further enhanced by PD-CNC, with up to 100% of adsorption efficiency for MB. Additional studies on MB/RB and MB/CV dye mixtures confirmed that the improved selectivity of PD-CNCs towards MB is associated with the synergistic binding interactions, such as electrostatic attraction, π-π stacking, and hydrogen bonding. MF-CNCs with cationic amine groups displayed selective binding towards MO , an anionic dye. Both PD-CNCs and MF-CNCs were found to completely separate MB and MO from a diluted binary dye mixture. Isothermal titration calorimetry and dye flocculatio experiments confirmed that the selective binding is associated with the surface-functionality of CNCs.