| Cotton fiber is the most produced natural fiber in the world and has an important position in the national economy.The surface of cotton fiber is rich in hydroxyl groups,and wastewater treatment materials with high adsorption properties can be prepared by surface modification.In this paper,degreasing cotton was used as a substrate to impart water treatment functions by introducing aromatic heterocyclic compounds on the surface of cotton fibers for the adsorption of chromate ions and anionic dyes.Specific studies of this paper are as follows:（1）Preparation and adsorption performance of polypyrrole modified cottonPolypyrrole-modified cotton（CPPy）was prepared by reactive polymerization on the surface of degreasing cotton using pyrrole as a functional monomer and taking advantage of its easy polymerization characteristics.The cotton fibers were characterized with CPPy using scanning electron microscopy（SEM）and infrared spectroscopy（FTIR）,and the formation of polypyrrole layer on the surface of cotton fibers was confirmed;the effects of p H,adsorption time and pollutant concentration on the adsorption performance were explored,and the kinetic process of adsorption and isothermal adsorption were also studied to explore the adsorption mechanism.（2）Preparation of cotton fibers modified with aromatic heterocyclic compounds and study of Cr（VI）adsorption performanceUsing 4-aminopyridine and 2-aminopyrazine as functional monomers,two modified cotton fibers（C-4-APD and C-2-APZ）were obtained by introducing 4-aminopyridine and2-aminopyrazine,respectively,on the surface of degreasing cotton to investigate the adsorption performance of the modified cotton fibers on Cr（VI）ions.The structures of the two modified cottons were analyzed by SEM,FTIR and XPS,and the results showed that amino,pyridine and pyrazine groups were successfully introduced on the surface of cotton fibers.The maximum adsorption amounts of C-4-APD and C-2-APZ were 89.66 mg/g and54.92 mg/g,respectively,at p H 2 and an initial concentration of 300 mg/g of Cr（VI）ions.Kinetic,isotherm and thermodynamic studies were carried out to investigate the adsorption behavior of the modified cottons on Cr（VI）ions.The results showed that the adsorption of Cr（VI）ions by modified cottons followed a pseudo-second-order kinetic model,the equilibrium data were in good agreement with the Langmuir isotherm model,and the thermodynamic analysis indicates that the adsorption proceeds spontaneously.The recovery and reuse of modified cotton were achieved by washing with 2 wt% thiourea-hydrochloric acid solution（0.5 mol/L concentration of HCl）,and the adsorption capacities of C-4-APD and C-2-APZ were maintained above 90% and 85%,respectively,after six cycles.（3）Preparation of pyridine-modified cotton fibers for anionic dye treatmentModified cotton fibers were prepared by introducing 4-aminopyridine on the surface of cotton fibers and used to remove anionic dyes from aqueous solutions.SEM,FTIR and XPS characterization of both modified cottons confirmed the grafting of amino and pyridine groups on the surface of the modified cotton fibers.The maximum adsorption capacities for congo red,methyl orange and orange II were 984.87 mg/g（p H=12）,489.8 mg/g（p H=8.5）and599.66 mg/g（p H=8）,respectively.Kinetic and isotherm studies were carried out to investigate the adsorption behavior of the modified cottons on the anionic dyes.The results showed that the adsorption of the anionic dyes by modified cottons followed a pseudo-second-order kinetic model,the equilibrium data was well consistent with the Langmuir isotherm model,and chemisorption and monolayer adsorption were the main adsorption mechanisms.The reuse efficiency of modified cotton was over 80% after six cycles.In addition,the presence of cationic dyes has almost no effect on the adsorption of anionic dyes,and the modified cotton exhibited highly selective adsorption of methyl orange in mixed solutions of methyl orange and methylene blue.This paper also provided a new solution for textile dyeing. |
PDF Full Text Request