Preparation Of Magnetic Chitosan And Its Adsorption Performance For Th⁴⁺ In Radioactive Waste Liquid

Radioactive materials have been widely used in many industrial sectors,such as nuclear power plants,biomedical engineering,etc.With the application of nuclear technology,more and more radioactive wastewater is generated through different channels,which poses new challenges and threats to the environment and human health.Dissolved radionuclides are mobile in the natural environment and they can enter aquatic environments without proper treatment,such as rivers and groundwater.More importantly,radionuclides dissolved in aqueous media may be absorbed by microorganisms,algae,plankton,plants or crops and further accumulate and aggregate through the food chain,posing a serious threat to animals,plants and humans.Therefore,the removal and recycling of radioactive ions in radioactive wastewater is an increasingly concerned problem.In the common processing technology,adsorption method has been widely concerned because of its advantages such as simple operation,low cost,good adsorption selectivity and reproducibility.Chitosan based adsorbent,a natural biomass material,is widely used in the treatment of heavy metal wastewater and pharmaceutical wastewater because of its green environmental protection and good adsorption effect.In view of this,the modified magnetic chitosan composite adsorption material was prepared by magnetic composite modification with chitosan as the adsorption material.The main contents and conclusions of the paper are as follows:1.In this paper,an amidated magnetic chitosan composite was prepared.Firstly,CoFe₂O₄@SiO₂ nanoparticles?CoFe₂O@SiO₂?were prepared by Stober method.Then,by optimizing the experimental conditions and using CoFe₂O₄@SiO₂ as magnetic core,the magnetic chitosan composite?CS-CoFe₂O₄@SiO₂?was prepared by inverse emulsion crosslinking method.Chitosan and CoFe₂O₄@SiO₂ were prepared.Finally,through the optimization of the experimental conditions,we carried out the amidation reaction,using1-?3-dimethylaminopropyl?-3-ethylcarbodiimide hydrochloride?EDC?and N-hydroxys-uccinimide?NHS?as the initiators,and grafted glda onto the magnetic chitosan composite.2.A series of characterization showed that CS-CoFe₂O₄,CS-CoFe₂O₄@SiO₂,CS-CoFe₂O₄-GLDA and CS-CoFe₂O₄@SiO₂-GLDA were mesoporous structures.BET specific surface areas were 24.542m²/g,19.323m²/g,14.410m²/g and 9.905m²/g,respec tively.CS-CoFe₂O₄,CS-CoFe₂O₄@SiO₂,CS-CoFe₂O₄-GLDAand CS-CoFe₂O₄@SiO₂-G LDA have good superparamagnetism,with saturation magnetization of 21.71emu/g,17.57emu/g,7.49emu/g and 6.77emu/g,respectively.GLDA was successs fully grafted onto magnetic chitosan composites.3.Through a series of single factor experiment,research the solution of the initial pH value,adsorption time,initial concentration of solution,the influence of the adsorption performance of adsorption material.When the initial pH value of the solution is 4,the adsorption equilibrium time is 360min,and the initial concentration of the solution is 100mg/L,the adsorbent has the best adsorption effect.In addition,through the analysis of the adsorption model,the adsorption of Th?IV?by CS-CoFe₂O₄-GLDA and CS-CoFe₂O₄@SiO₂-GLDA conforms to the quasi-second-order kinetic model and the Langmuir adsorption isotherm model.The adsorption rate of Th?IV?by adsorbent may be controlled mainly by chemical adsorption,and the adsorption process is self-advantageous monolayer adsorption and endothermic reaction.CS-CoFe₂O₄-GLDA and CS-CoFe₂O₄@SiO₂-GLDA have better adsorption performance for Th?IV?in both single system and mixed system,and GLDA modification promotes adsorption selectivity for Th?IV?.Moreover,after five adsorption-desorption cycle experiments,CS-CoFe₂O₄@Si O₂-GLDA still has a large adsorption capacity.At the same time,after CoFe₂O₄ coated SiO₂,the leaching rate of iron and cobalt under acidic conditions was very low,and the stability and integrity of the magnetic core were better.4.Adsorption materials to explore the actual effect of radioactive waste water treatment,the CS-CoFe₂O₄-GLDA and CS-CoFe₂O₄@SiO₂-GLDA of monazite leaching liquid adsorption treatment,the experimental results shows that CS-CoFe₂O₄-GLDA and CS-CoFe₂O₄@SiO₂-GLDA radioactive waste liquid in the still has a good adsorption performance and adsorption on Th⁴⁺selective,and for other metal ions also have certain remove effect.