Study On Adsorption Of Pb(Ⅱ) Ion By Modified Polyvinylamine Gel

With the rapid development of industry and agriculture,the problem of heavy metal pollution is becoming increasingly severe,which not only pollutes the environment but also poses a serious threat to human health.Because there are large number of primary amino groups connected to its side chains in polyvinylamine,various chemical reactions may occur for polyvinylamine.Amino groups in polyvinylamine can also complex with various metal ions,so it is one of the most promising adsorption materials.（1）In this paper,sodium lignosulfonate grafted polyacrylamide（LS-g-PAM）gel was prepared by free radical graft copolymerization using sodium lignosulfonate and acrylamide as raw materials and N,N’-methylenebisacrylamide as crosslinking agent.By Hofmann degradation reaction of LS-g-PAM,the amide group was converted into amino group,and the lignosulfonate-g-polyvinylamine（LS-g-PVAM）gel was prepared.The LS-g-PVAM gel was characterized by infrared spectrum,and the effects of different reaction conditions on Hofmann degradation ratio and Pb²⁺adsorption were explored.Examine the effects of solution p H and temperature on Pb²⁺adsorption capacity.The adsorption of Pb²⁺by LS-g-PVAM kinetic and thermodynamic models were studied.Pb²⁺can be desorbed from LS-g-PVAM and LS-g-PVAM can be regenerated.The results are as follows:The maximum adsorption capacity of LS-g-PVAM for Pb²⁺in water is 125.56mg·g^-1.Under acidic conditions,the amount of Pb²⁺adsorbed by LS-g-PVAM increases as the p H increases.Before reaching adsorption equilibrium,increasing the temperature is beneficial to increasing the diffusion rate of Pb²⁺and the adsorption rate.The adsorption of Pb²⁺by LS-g-PVAM fits with the Langmuir adsorption isotherm equation and quasi second-order kinetic equation.The adsorption of Pb²⁺by LS-g-PVAM is monolayer chemical adsorption.LS-g-PVAM can be recycled for renewable use.（2）Pyromellitic anhydride modified polyvinylamine gel（PAPVAM）was prepared by the reaction of pyromellitic anhydride and polyethylene amine,and it can be used as adsorbent for Pb²⁺.Characterizations were tested by FT-IR and solid ¹³C NMR,SEM and EDX,XPS,DSC.The kinetic and thermodynamic models of adsorption of Pb²⁺by PAPVAM were fitted.Pb²⁺can be desorbed,and PAPVAM can be regenerated.The results are as follows:PAPVAM was used as adsorbent for Pb²⁺.The adsorption capacity was 140.42 mg·g^-1.The adsorption of Pb²⁺by PAPVAM fits quasi second-order kinetic model,indicating that it is chemical adsorption.Differential scanning calorimetry showed that the adsorption of Pb²⁺by PAPVAM was an exothermic process.The adsorption process also conforms to the Freundlich isotherm equation,which indicates that it is multi-layer adsorption.Programmed temperature control was designed to improve the adsorption capacity of Pb²⁺.The results showed that at 50℃,Pb²⁺could penetrate into the gel material,while at 30℃,it was beneficial to improve the thermodynamic adsorption capacity.After adsorption of Pb²⁺by PAPVAM,it can be recycled and reused.