Construction Of Ionic Liquid Functional Groups Modified Cellulose-based Adsorbent And Its Properties Research

In recent years,water pollution has become increasingly serious with the continuous development of industry.A large number of pollutants such as dyes,heavy metal ions and organic substances like proteins have been discharged into water.Adsorption method is an important way to reduce water pollution due to its facile operation,whereas,many reported adsorbents are expensive and low-efficiency,impeding its practical application.Cellulose is the most abundant polymer biomaterial in nature with the advantages of a wide range of sources,low-cost,easy to obtain,biodegradable and environmental friendly.Thus,as the adsorbent substrate is one of an important development direction of cellulose based functional materials.However,weak interactions with pollutant molecules in the aqueous phase limit its application for this purpose.chemical modification is an ideal method to construct high-performance cellulose-based adsorbents via grafting functional compounds,as it could produce strong interactions between pollutants and the cellulose surface.Imidazolium ionic liquid can produce multiple interactions with guest molecules in water,resulting in enhanced adsorption capacity.Moreover,the unique structural flexibility of imidazolium ionic liquid makes it adaptable for various chemical modification reactions.In addition,as a nucleophilic reagent tertiary amine,imidazole can easily undergo alkylation reaction with halogenated hydrocarbons,and it is easy to modify materials to generate and prepare structures with cationic imidazole functional groups.Therefore,the adsorption materials modified by the imidazolium ionic liquid functional group are able to show excellent application characteristics in the field of pollutant separation and treatment.This research used cellulose material as the substrate and imidazolium ionic liquid as a modifier,designed and adjusted ionic liquid structures and modification methods to prepare several cellulose based functional adsorbents towards different pollutants in water phase.(1)Based on the strategy of utilizing the multiple interactions between the imidazolium functional group and anionic dye Congo Red,a cellulose paper-based adsorbent with imidazolium ionic liquid functional groups was prepared through traditional cellulose esterification and alkylation reactions.Besides,the modified material had significantly higher Zeta potential and porosity than the original paper,and the graft content of the imidazolium ionic liquid functional group was 1.2 mmol·g-1.In addition,adsorption experiments proved that the modified material exhibited good adsorption performance for Congo red with the adsorption capacity increased to 3.5 times than before modification,which could reach 563 ± 21 mg·g-1.By investigating the mechanism of adsorption,it can be concluded that the significant increase in the adsorption capacity is due to the multiple interactions such as the electrostatic interaction,hydrogen bonding and ?-? conjugation between the imidazolium ionic liquid functional groups and the Congo red molecules in the aqueous phase.(2)Considering the important influence of reaction conditions on the property of paper-based material during the functionalized process of cellulose,this study used the milder oxidation reaction of cellulose and Schiff base reaction as the modification method of paper-based materials.Through chemical structure characterization,it was found that the prepared adsorbent has a high ionic liquid grafting content(2.1 mmol·g-1).When it is used for the adsorption and removal of Cr(VI)in the aqueous phase,the maximum adsorption capacity can reach to 134 ± 2 mg·g-1,which is more than 5 times than the material before modification.By combining the model fitting results and characterization of surface morphology,chemical structure,and elemental changes of the materials before and after adsorption,it was found that the removal process of the Cr(?)by the imidazolium ionic liquid modified paper-based adsorbent not only includes complex adsorption,but also a reduction process that converts highly toxic Cr(?)to less toxic Cr(?).(3)In order to further enhance the separation and adsorption capability of the imidazolium ionic liquid modified cellulose material,this study increased the number of active sites and the mesh structure of the material.The cellulose aerogel with high specific surface area and porous structure was used as substrate,which reacted via Schiff base reaction to prepare the polyionic liquid modified cellulose aerogel adsorbent.In addition,the prepared functionalized aerogel was used for the removal of bovine serum albumin.Due to the multiple interactions like electrostatic interaction,?-? stacking,hydrogen bonding and hydrophobic interaction,the adsorption capacity of functionalized material can be increased to 918 ± 8 mg·g-1.In this work,the low-cost,naturally degradable cellulose was chose as the raw material with the structurally adjustable imidazolium ionic liquid as the modifier to design and construct three kinds of functionalized cellulose based adsorbent by using a series of different modification methods.The successful preparation of this material can effectively treat dyes,heavy metal ions and organic pollutants in the water phase to purify water.On the one hand,it can increase the value of cellulose utilization,on the other hand,it provides new research ideas and solutions for obtaining efficient,environmental friendly and sustainable biomass adsorbent.