Preparation Of Amino Polycarboxylic Acid Modified Magnetic Chitosan And Study On Its Adsorption Properties For Heavy Metal Ions

Water resources have always been indispensable in the course of human life and development.With the progress and development of China's modern industrialization,water pollution has continued to increase,especially heavy metal pollution in water bodies.Heavy metals entering the aquatic environment will enter the human body with the accumulation of the food chain and cause serious harm to the human body.Removal of heavy metals from polluted water bodies has become a top priority,and many treatment methods have been applied to actual treatment.Among the many heavy metal treatment methods,the adsorption method is considered to be the most ideal method due to its economy,high efficiency,and pollution-free renewable use.The advantages of the adsorption method are largely attributed to the adsorbent.Among various adsorbents,chitosan is widely used for the removal of heavy metals due to its excellent chemical properties,environmental friendliness and rich adsorption sites.Chitosan has high solubility at pH lower than 5.5,and it is difficult to separate from aqueous solution,which limits its application as adsorbent in wastewater treatment.The combination of chitosan and magnetic components can effectively solve these disadvantages.In addition,in order to further improve the adsorption capacity of the magnetic chitosan adsorbent for heavy metal ions,it is necessary to modify the adsorbent to introduce functional groups that are favorable for adsorption.Amino polycarboxylic acid compounds can form stable structures with heavy metal ions and are important chelating agents.Grafting them onto adsorbents can effectively improve the adsorption performance of the adsorbents.In this article,magnetic chitosan was prepared by crosslinking of glutaraldehyde and chitosan with ferric oxide as magnetic component,chitosan as matrix and glutaraldehyde as crosslinking agent.Then,EDTA-CS/Fe₃O₄ and DTPA-CS/Fe₃O₄adsorbents were synthesized by grafting amino polycarboxylic acids?EDTA and DTPA?onto magnetic chitosan.The structure,surface morphology and composition of the adsorbent were characterized by IR,XRD,SEM and TGA.The adsorption capacity of the two adsorbents for heavy metal ions was discussed.The optimal adsorption conditions were optimized by changing the initial pH,time,solution concentration temperature and other conditions.The kinetic,thermodynamic and isotherm models were used to fit the experimental data,and the adsorption behavior of the adsorbent was analyzed.The experimental results are as follows:The saturated adsorption capacity of EDTA-CS/Fe₃O₄ for Cu²⁺is 86.32 mg/g at the conditions of pH=6,T=298 K,c₀=200 mg/L and t=2 h,while the saturated adsorption capacity of EDTA-CS/Fe₃O₄ for Cd²⁺is 176.32 mg/g at the conditions of pH=5,T=298 K,c₀=200 mg/L and t=30 min.The adsorption behavior of the EDTA-CS/Fe₃O₄ adsorbent for both Cu²⁺and Cd²⁺can be better fitted by the quasi-second-order kinetic model and the Langmuir isotherm model.Proper temperature rise is favorable for the adsorbent adsorption.The adsorbent still has good adsorption performance after five adsorption regenerations.The saturated adsorption capacity of DTPA-CS/Fe₃O₄ for Cu²⁺was 67.72 mg/g at the conditions of pH=6,T=298 K,c₀=150 mg/L and t=2h,while the saturated adsorption capacity of DTPA-CS/Fe₃O₄ for Cd²⁺is 128.28 mg/g at the conditions of pH=5,T=298 K,c₀=200 mg/L and t=30 min,The adsorption behavior of the DTPA-CS/Fe₃O₄ adsorbent for both Cu²⁺and Cd²⁺can also be better fitted by the quasi-second-order kinetic model and the Langmuir isotherm model.Proper temperature rise is favorable for the adsorbent adsorption.The adsorbent still has good adsorption performance after five adsorption regenerations.