Preparation Of Modified Magnetic Chitosan Adsorbent And Study On Treatment Of Pb²⁺ And Cu²⁺ In Water

In recent years,with the social and industrial rapid development,the problem of heavy metal pollution has occurred.Pb²⁺ and Cu²⁺ pollution have become very representative problems.Among the treatment technologies,the adsorption method is widely used because of its simple operation,low cost,fast reaction speed and so on.However,the development of highly efficient and readily recyclable adsorbent materials is attractive.In this study,Pb²⁺ and Cu²⁺ were selected as the target contaminant.On the basis of the existing research,xanthated modified magnetic chitosan and EDTA modified chitosan were prepared by improved embedding-gel method and coprecipitation method.Synthetic polluted water and actually polluted water were used to evaluate the adsorption properties of adsorbents.The adsorption mechanism was evaluated by characterization such as FTIR,SEM,XRD and XPS.In this study,it was found that the poly?vinyl alcohol?type,crosslinking agent type,crosslinking agent concentration and carbon disulfide concentration had significantly effects on the adsorption capacity of xanthated modified magnetic chitosan.Under condition of PVA-1788,the glutaraldehyde concentration of 0.05% and carbon disulfide concentration of 1.0%,xanthated modified magnetic chitosan had great adsorption capacity.Meanwhile,the chitosan content significantly affected the adsorption performance of EDTA modified magnetic chitosan.The results showed that the adsorption performance increased with the increase of chitosan content.The characterization indicated that the specific surface area?SBET?of xanthated modified magnetic chitosan was 15.52 m2/g,the total pore volume was 0.048 cm3/g,and the pore size was at 0.5 to 5.0 nm.The results showed that the increase of chitosan content in EDTA modified magnetic chitosan would decrease the roughness,surface area,pore volume,average crystal size and magnetic separation performance,but could increase the degree of modified EDTA modified magnetic chitosan,consequently improving the adsorption of adsorbent.At the same time,through the adsorption and desorption cycle experiments showed that the developed adsorbent materials had good magnetic separation and regeneration performance.The results showed that the adsorption capacity of Pb²⁺ and Cu²⁺ for the two kinds of adsorbents was higher when the p H was neutral,and the adsorption rate and adsorption capacity increased with the increase of initial concentration.At the same time,the experimental results of actual surface water and actual groundwater showed that the two kinds of adsorbents can effectively adsorb Pb²⁺ and Cu²⁺ in the actual water,and the treatment effect is better than synthetic water.In addition,the dynamic adsorption of xanthated-modified magnetic chitosan showed that the Thomas model described its dynamic adsorption process of Pb²⁺ well.From the analysis of adsorption kinetic,adsorption isotherm and adsorotion thermodynamic,the adsorption process of Pb²⁺ and Cu²⁺ was described by pseudo-second-order kinetic model,indicating that the chemical adsorption was the main rate limiting step.The Langmuir and Freundlich models were fitted well to the equilibrium data,indicating that the adsorption process was a homogeneous and heterogeneous interaction.When the temperature is 35?,the maximum adsorption capacity of Pb²⁺ and Cu²⁺ on the xanthated modified magnetic chitosan was 57.983 and 123.725 mg/g,while the maximum adsorption capacity of EDTA modified chitosan for Pb²⁺ and Cu²⁺ was 274.266 and 98.864 mg/g.The two kinds of materials showed great adsorption capacity.The difference between Pb²⁺ and Cu²⁺ was due to the difference of the existence in the aqueous solution.FTIR,SEM,XRD and XPS characterizations showed that the adsorption of Pb²⁺ and Cu²⁺ on xanthated modified magnetic chitosan was mainly due to the chemical adsorption between N and S and the metal ions,and the physical adsorption of metal ions on the surface of the material,while the adsorption process of EDTA modified magnetic chitosan was through the role of N and O,metal ions in the form of complexation in the adsorbent surface.The results showed that the developed adsorbents can be applied to the treatment of Pb²⁺ and Cu²⁺ in water,and provided technical support for the remediation of heavy metal contaminated water.