Effective removal of cationic dyes using carboxylate-functionalized cellulose nanocrystals

[Display omitted] •The graft rate of maleic anhydride on cellulose nanocrystals can reach a high value of 88.8%.•CNM exhibited wide adsorption capacities to cationic dyes.•CNM displayed a rapid adsorption rate and an efficient adsorption capacity to crystal violet.•CNM could be regenerated and reused for adsorption of crystal violet at least four times. A novel carboxylate-functionalized adsorbent (CNM) based on cellulose nanocrystals (CNCs) was prepared and adsorptive removal of multiple cationic dyes (crystal violet, methylene blue, malachite green and basic fuchsin) were investigated. The maximum cationic dyes uptakes ranged from 30.0 to 348.9mgg−1 following the order of: CNM>CNCs>raw cellulose. Furthermore, the removal of crystal violet by CNM was investigated representatively where kinetics, thermodynamics and isotherm analysis were employed to explain in-depth information associated with the adsorption process. The adsorption kinetics fitted well to the pseudo-second-order model and thermodynamic analysis revealed that the adsorption process was spontaneous and exothermic. Meanwhile, isothermal study demonstrated a monolayer adsorption behavior following the Langmuir model with a calculated maximum absorption capacity of 243.9mgg−1, which is higher than those of many other reported adsorbents. These findings prefigure the promising potentials of CNM as a versatile adsorbent for the efficient removal of cationic dyes from wastewater.