Preparation Of Modified ?-Cyclodextrin Polymers And Adsorption Properties For Pollutants In Aqueous Solutions

With the widespread application of organic dyes and metal-based materials in various industrial productions,organic dyes and heavy metals coexist widely in groundwater or wastewater.These pollutants have stable components,complex structures,and are not easy to handle.Adsorption is widely used in wastewater treatment as a safe,efficient and low-cost method.Therefore,it is of far-reaching significance to study adsorption materials that can quickly and efficiently remove dyes and heavy metal ions in wastewater.?-cyclodextrin possess its own cavity structure,and meanwhile,it is a promising material for adsorption.Previously,?-cyclodextrin and tetrafluoroterephthalonitrile were substituted by nucleophilic aromatics to obtain?-cyclodextrin polymer(CDP-CN)to solve the solubility problem.In order to make?-cyclodextrin polymer exhibit better effect on the adsorption of dyes and heavy metal ions.In this paper,diethanolamine,borane-tetrahydrofuran,and hydroxylamine aqueous solution were used to modify nitrile groups to obtain diethanolamine-modified?-cyclodextrin polymer(CDP-DEA)and amine-modified?-cyclodextrin polymer(CDP-NH₂)and amidoxime modified?-cyclodextrin polymer(CDP-AM)three adsorption materials,greatly improving the adsorption capacity of pollutants.(1)The CDP-DEA polymer was prepared by modified CDP-CN.The morphology and microstructure of CDP-DEA were determined by FT-IR,¹³C NMR,XPS,SEM,TEM,BET,TG/DTG and other characterization.The electric potential of CDP-DEA at different p H values was determined by?potential.CDP-DEA was found to have selective adsorption for anionic dyes;the selective adsorption of anionic dyes was verified by using methylene blue and orange G mixed dyes,and the effects of p H and contact time on the adsorption of congo red and orange G were investigated.The best adsorption p H is 5 and the optimal adsorption p H of orange G is 3,and the adsorption equilibrium is gradually reached in about 3 hours.The adsorption kinetics,adsorption isotherm,adsorption thermodynamics,and repetition of CDP-DEA for congo red and orange G are also further studied.Utilizing capacity,adsorption composite pseudo-secondary kinetics and Langmuir linear isotherms,Experiments show that Congo Red and Orange G have excellent adsorption effects at three temperatures.Thermodynamic data show that the endothermic process of the adsorption process can be spontaneous,and it can still reach a very high adsorption efficiency of more than 97%after multiple cycles.(2)The CDP-NH₂polymer was prepared by CDP-CN.The morphology and structure of CDP-NH₂were determined by FT-IR,¹³C NMR,XPS,SEM,TEM,BET,TG/DTG and other characters.The degree of protonation of CDP-NH₂at different p H values was determined by the?potential.The selective adsorption of anionic dyes was verified,and the effects of p H and contact time on the adsorption of congo red and orange G were explored.Orange G had the best adsorption effect at p H=3,and the adsorption equilibrium was gradually reached in about 3 hours;CDP was further studied-NH2 adsorption kinetics,adsorption isotherm,adsorption thermodynamics,and reusability.The adsorption conforms to pseudo-second-order kinetics and Langmuir linear isotherms.Experiments show that the adsorption capacity of Orange Yellow G exceeds 400 mg/g at three temperatures.The thermodynamic parameters of adsorption prove that it absorbs heat spontaneously and spontaneously during the adsorption process,and can still reach a very high adsorption efficiency of more than97%after multiple cycles.However,for congo red solution,the adsorption effect is not good due to the structure.(3)The structure and morphology of the prepared CDP-AM polymer were characterized by FT-IR,¹³C NMR,XPS,TGA,BET,SEM and TEM.CDP-AM was used for the first time to remove two heavy metal ions,Pb(?)and Cu(?).The effects of p H and contact time on the adsorption of Pb(?)and Cu(?)were investigated.Pb(?)and Cu(?)The adsorption equilibrium was slowly reached in about 5 hours;before Pb(?)and Cu(?)precipitation,p H=6 was determined as the optimal adsorption condition;and the adsorption kinetics and adsorption of CDP-AM on p H=6 were further studied Isotherms,adsorption thermodynamics and reusability,adsorption conforms to pseudo-second-order kinetics and Langmuir linear isotherms.Experiments show that the adsorption capacity of Cu(?)at 303-323 K can reach273.97-284.09 mg/g.Has an adsorption capacity of 281.69-294.99 mg/g;thermodynamic results show that the adsorption process is endothermic and spontaneous,and can still reach a high adsorption efficiency of more than 65%after multiple cycles.