Farbrication And Adsorption Properties Of Polyethyleneimine Based Composite

Polyethyleneimine?PEI?is known as the cationic polymer with the highest charge density currently.As a new type of heavy metal ion adsorbent,PEI has strong ability to chelat and complex with metal ions due to a large number of primary,secondary and tertiary amine groups on its molecule chains.However,PEI exist as free molecules in the aqueous phase.As an adsorbent in practical application,it has some disadvantages of hard operation,difficult separation and recovery,even easy loss.PEI was immobilized on the matrix materials by using chemical cross-linking reaction,further recombinated with carbon filler.Finally,two kind of polyethyleneimine-based composite materials were synthesized to adsorb the lead ions and uranyl ions in aqueous solution,respectively.Details were as follows:?1?Using PEI as a functional group,carboxylmethyl konjac glucomannan as a matrix,graphene oxide as a nanofiller,a novel porous composite PCGt was synthesized by a facile chemical crosslinking method.The effect of the amount of each raw material,the amount of cross-linking agent,the reaction temperature,and the cross-linking time on the stucture and the adsorption capacity were explored.The optimal synthesis conditions for the material were further determined.The prepared PCGt was characterized by scanning electron microscope,fourier transform infrared spectroscopy,thermal gravimetric analysis and elemental analysis.It was found the structure of PCGt was a three-dimensional interconnected skeleton composed of irregular pores.Batch adsorption experiments were designed to exploit key factors on lead ions removal such as the pH of the solution,the amount of adsorbent,the adsorption time,the initial concentration of lead ions,and the adsorption temperature.Four kinetic models?pseudo-first-order,pseudo-second-order,Elovich and intra-particle diffusion kinetic model?and two isotherm adsorption models?Langmuir and Freundlich isotherm model?were adopted to analysis the data.The maximum adsorption capacity of PCGt on lead ions was up to 977mg·g^–1 at 308.15 K.The experimental data were more fitted to pseudo-second-order kinetic model and Freundlich isotherm model.According the thermodynamics results,the adsorption process was spontaneous and endothermic process at 308.15 K,and high temperature is favorable.Using 1 mol·L^–1 NaOH as the desorbent,the adsorption capacity of PCGt maintained above 85%after five adsorption-desorption cycles.The adsorption mechanism of PCGt on Pb²⁺may be the formation of new Pb–O substances and the complexation between–NH₂,–NH–and Pb²⁺.?2?Using PEI as a functional group,carboxylated chitosan as a matrix,oxidizing activated carbon as a nanofiller,a novel porous composite named as PCO was synthesized by a facile chemical crosslinking method.Effects of the amount of raw materials and cross-linking agent on the morphology and adsorption properties of composites were explored.The prepared PCO was characterized by scanning electron microscope,fourier transform infrared spectroscopy and elemental analysis.It was found the surface structure of PCO was uneven and had many fine pores.Batch adsorption experiments were designed to exploit key factors on uranyl ions removal such as the pH of the solution,the amount of adsorbent,the ionic strength,the adsorption time,the initial concentration of uranyl ions,the adsorption temperature,and interfering ions.Four kinetic models?pseudo-first-order,pseudo-second-order,Elovich and intra-particle diffusion kinetic model?and four isotherm adsorption models?Langmuir,Freundlich,D-R and Temkin isotherm model?were adopted to analysis the data.The maximum adsorption capacity of PCO on uranyl ions was up to 450 mg·g^–1 and the maximum adsorption efficiency was up to 98.47%at 308.15 K.The experimental data were more fitted to intra-particle diffusion kinetic model and Langmuir isotherm model.The kinetic,isotherm and thermodynamic results suggested that the adsorption of uranyl ions was a mass transferring and intraparticle diffusing,monolayer cover and homogeneous,physisorption and chemsorption dominated process.Using 0.5 mol·L^–1 NaHCO₃ as the desorbent,the adsorption capacity of PCO decreased less than 7.51%after five adsorption-desorption cycles.PCO has good adsorption selectivity for uranyl ions,with a K_d value of about 3.45×10⁴ mL·g^–1.The adsorption mechanism of PCO on UO₂²⁺may be the single-layer physical adsorption and complexation occurred on the inner surface of the particles,which controlled by the nitrogen-containing and oxygen-containing functional groups on the PCO.In this paper,PEI was successfully immobilized on environmentally friendly,low-cost biomass substrate by using a chemical cross-linking reaction.The shortcomings of PEI were overcame.Two kinds of polyethyleneimine-based composite materials,PCGt and PCO,were synthesized by optimizing and combinating the advantages of each raw material.PCGt and PCO have stable structure,excellent adsorption capacity,good reusability,and recycling favourability.These two materials showed good potential for application in the fields of wastewater treatment contained lead ions and uranyl ions,respectively.