| Cellulose nanocrystals(CNCs)have many excellent characteristics such as highly reactive,specific surface area,rich surface hydroxyl and highly hydrophilic,which are very beneficial as a new type of matrix material of adsorbents for the removal of pollutants in water.In this work,we prepared four adsorbents with different structure,morphology and functional characteristics in three different modification ways.And then the removal of dyes and ionic liquids by functional cellulose nanocrystals adsorbents were systematically studied.The details are as follows:(1)Removal of cationic dyes using carboxylate-functionalized cellulose nanocrystals.In this work,a low cost and effective biosorbent for cationic dyes was prepared from modifying cellulose nanocrytals(CNCs)with maleic anhydride.The as-made adsorbent was named of carboxylate-functionalized cellulose nanocrytals(CNM)with a high graft rate of maleic anhydride of 88.8%for removing cationic dyes from aqueous solutions.The removal capacity of CNM for crystal violet was investigated detailedly.Furthermore,adsorption kinetic studies indicated that the adsorption behavior of crystal violet followed the pseudo-second-order kinetic model.Thermodynamic analyses revealed that the adsorption process was spontaneous,exothermic,and adsorption isothermal could be described by the Langmuir.adsorption model with a high maximum uptake of 243.9 mg g-1 at 30?.CNM could be regenerated effectively and recycled for at least four times with good adsorption performance for crystal violet,which revealed great potential applications of CNM as a promising adsorbent for removal of cationic dyes from wastewater.(2)Removal of ionic liquids by functionalized cellulose nanocrystals.In this work,we studied the potentials of functionalized cellulose nanocrystals(CNGD and CNGS)as novel biosorbents for the removal of ionic liquids from aqueous solution.Diethylenetriaminepentaacetic acid and sulfosalicylic acid were employed to modify cellulose nanocrystals and thus to improve their adsorption of 1-Butyl-3-Methylimidazolium Chloride([Bmim]Cl),a typical hydrophilic ionic liquid.The maximum[Bmim]Cl adsorption capacities of CNGD and CNGS reached 0.474 mmol g-1 and 0.499 mmol g-1,respectively,which are higher than that of many other reported adsorbents.Monolayer adsorption of[Bmim]Cl onto the adsorbents were revealed by a better fitting of the Langmuir model.Adsorption kinetic studies indicated that the adsorption behavior of[Bmim]Cl followed the pseudo-second-order kinetic model.The Intra-particle diffusion model showed that the rate-controlled step were dominated by external mass transfer in the beginning and then followed by the intra-particle diffusion.Furthermore,the reusability performances and cycling behaviors confirmed the promising potential of the functionalized cellulose nanocrystals as cost-effective adsorbents for the removal of ILs from wastewater.(3)Removal of the ionic liquids by graphene oxide/cellulose nanocrystals composites.In tis work,we prepared one-dimensional bar-shaped CNCs and two-dimensional sheet-shaped graphene oxide composites GCs,and then characterized and studied for the adsorption of ionic liquid([Bmim]Cl).The as-made GCs has three-dimensional porous morphology characteristics and riched of oxygen-containing functional groups on the surface.The adsorption capacity of[Bmim]Cl is the largest when GO content of 30%,which is far higher than that of CNCs or GO.The maximum adsorption capacity of GCs can reach 0.455 mmol g-1.The rich functional groups and the porous structureof GCs are mainly contributing to the high adsorption capacity.Adsorption process followed the pseudo-second-order kinetic and Langmuir adsorption isotherm model. |
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