Synthesis Of Polyacrylamide Composite And Treatment Of Radioactive Wastewater

With the development and application of nuclear energy,as well as the application of nuclear technology in food,medicine,military industry,agriculture and other fields,it is inevitable that radioactive wastewater will be produced in the process.The discharge of radioactive wastewater without treatment or substandard level will cause serious pollution to the environment.Even these radionuclides in the wastewater will enter the human body through the food chain,endangering the human health and survival.Therefore,there is an urgent need for efficient and economic radioactive wastewater treatment technology to be put into use,so as to solve this problem.It is one of the common physical and chemical methods to adsorb radionuclides in radioactive wastewater with suitable adsorbents.Adsorption method has been applied to the treatment of radioactive wastewater because of its simple process,high decontamination factor and selective removal of nuclides.However,some adsorbents have a more or less high cost,complex synthesis process and poor irradiation stability,the treatment effect will be reduced.Polyacrylamide is a kind of crosslinked hydrophilic polymer which can reach swelling equilibrium after absorbing a lot of water and can be applied to adsorption research through appropriate grafting modification.In this paper,we studied the adsorption of simulated radionuclides on Attapulgite grafted with polyacrylamide（PAM/ATP）,peanut shell cellulose grafted with polyacrylamide（PAM/PHC）,and peanut shell cellulose grafted with polyacrylamide and magnetic nanoparticles（PAM/PHC/n-Fe₃O₄）.We focused on the factors affecting the adsorption properties of the modified materials,the adsorption kinetics and thermodynamics of simulated radionuclides on materials,macroscopic appearance,and microstructure,etc.There are many kinds of radionuclides in radioactive wastewater,such as ⁵⁸Co,⁶⁰Co,⁵⁹Fe,¹¹⁰Ag^m,⁵⁴Mn,⁵¹Cr,⁶⁴Cu,⁶⁵Zn,¹⁰⁷Pb,⁶³Ni,¹⁴⁴Ce,and other radionuclides.Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺,Ce⁴⁺without radioactivity are used to carry out experimental research instead of radionuclides because the radionuclides have the same chemical properties and different physical properties with their non-radioisotopes.The best performance of polyacrylamide adsorbent is expected through experimental research.And master the adsorption behavior and mechanism of this kind of adsorbent which can provide some reference for its treatment in radioactive wastewater.This thesis is divided into seven chapters.The first chapter is the introduction,which briefly introduces the methods and technologies of radioactive wastewater treatment,focusing on the research progress and the research content and significance of this paper.The second chapter is the principle and method.It briefly introduces the adsorption,its principle and experimental method.The third chapter is the synthesis of PAM/ATP composite materials.The factors that affect the adsorption properties of the synthesized PAM/ATP to ions are discussed.The fourth chapter is the study of PAM/ATP adsorption of simulated radionuclides,focusing on PAM/ATP adsorption thermodynamics and kinetics of simulated radionuclides.The fifth chapter is the study of PAM/PHC synthesis and adsorption performance.The synthesis factors that affect the adsorption performance of PAM/PHC are mainly discussed through orthogonal test,and the adsorption performance of PAM/PHC to simulated radionuclides is also discussed.In Chapter 6,the synthesis and adsorption of PAM/PHC/n-Fe₃O₄ were studied.The adsorption of simulated radionuclides by PAM/PHC/n-Fe₃O₄ was discussed.The seventh chapter is the summary and prospect,summarizes the research results of this paper.And according to the current conclusions,puts forward the corresponding prospects for the future research direction.The main conclusions are as follows:（1）Firstly,some experience was accumulated through the synthesis of polyacrylamide,and then PAM/ATP was synthesized.The properties and adsorption mechanism of PAM/ATP were studied by FTIR and SEM.FTIR results showed that polyacrylamide was successfully grafted on attapulgite,and there were three adsorption sites of the composite,namely-COO^-,-COONa and-CONH₂.The synthesis factors include the influence of the content of potassium persulfate（KPS）on the adsorption performance;the influence of the content of N,N’-Methylenebisacrylamide（MBA）on the adsorption performance;the influence of the content of acrylamide（AM）on the adsorption performance;the influence of the content of attapulgite（ATP）on the adsorption performance.Considering the adsorption properties of various ions,PAM/ATP synthesized with KPS of 45 mg,MBA of 45 mg,am of 3 g and ATP of 5 g has the best adsorption properties.（2）Through static batch adsorption experiment,the adsorption of Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺,Ce⁴⁺by PAM/ATP synthesized under the optimum synthesis conditions was studied.The effects of time,p H,adsorbate concentration,adsorbent quality,and temperature on the adsorption of Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺,Ce⁴⁺were discussed in detail.The adsorption mechanism was explained and the corresponding kinetic and thermodynamic parameters were obtained.The results showed that the adsorption of Pb²⁺,Co²⁺,Ni²⁺,Ce⁴⁺on PAM/ATP reached equilibrium rapidly while the equilibrium time of Mn²⁺was more longer（240 min）.The influence of p H on adsorption is very large.Freundlich isothermal model can better describe the adsorption process of Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺,Ce⁴⁺on PAM/ATP.The adsorption process of PAM/ATP on Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺is a spontaneous endothermic reaction,and the temperature rise is conducive to the adsorption of Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺.However,the adsorption process of Ce⁴⁺is self-releasing thermal reaction,and the lower temperature is conducive to the adsorption of Ce⁴⁺.The adsorption mechanism of PAM/ATP to Pb²⁺and Co²⁺is physical adsorption,the adsorption mechanism of Mn²⁺such as complexation may be the main adsorption mechanism,and the adsorption mechanism of Ni²⁺and Ce⁴⁺is chemical adsorption.（3）The synthesis factors of PAM/PHC were studied by the orthogonal design test,focusing on the proportion of peanut shell cellulose and acrylamide,the mass of initiator,the mass of the crosslinker and the influence of synthesis temperature.The results showed that the degree of influence of synthesis factors on the adsorption properties of PAM/PHC was as follows:the mass of initiator>the ratio of peanut shell cellulose to acrylamide>synthesis temperature>the mass of the crosslinker.The level of the material with the largest adsorption properties was peanut shell:am=1:6,initiator 0.5 g,crosslinker 0.07 g,temperature 60℃.The adsorption of Pb²⁺,Co²⁺,Ni²⁺,Mn²⁺,Ce⁴⁺by PAM/PHC synthesized under the optimum conditions was studied by static batch adsorption experiment.The effects of time,p H,adsorbate concentration,adsorbent mass and temperature were discussed.The results showed that the adsorption of Pb²⁺,Ni²⁺,Co²⁺,Mn²⁺,Ce⁴⁺on PAM/PHC is a rapid kinetic equilibrium process,which is in accordance with the quasi second-order kinetic model.The adsorption process of Pb²⁺,Ni²⁺,Co²⁺,Mn²⁺,Ce⁴⁺on PAM/PHC is more in line with Freundlich isothermal model.The adsorption process of Pb²⁺,Ni²⁺,Co²⁺,Mn²⁺is a spontaneous endothermic reaction,and temperature rise is conducive to adsorption.While the adsorption of Ce⁴⁺is self-released thermal reaction,and low temperature is conducive to its adsorption.Under the same conditions,the adsorption capacity of PAM/PHC for Pb²⁺,Ni²⁺,Co²⁺,Mn²⁺was larger than that of the original materials.It was proved that the adsorption effect of PAM/PHC was better than that of the original materials.The adsorption mechanism of Co²⁺and Mn²⁺is physical adsorption,Pb²⁺and Ce⁴⁺are chemical adsorption,Ni²⁺is complexation or ion exchange.（4）For better solid-liquid separation of the adsorbed adsorbent,magnetic nano-Fe₃O₄ was added in the synthesis of PAM/PHC to obtain PAM/PHC/n-Fe₃O₄.The adsorption of Co²⁺and Mn²⁺on PAM/PHC/n-Fe₃O₄ was studied by static batch adsorption experiments.The effects of time,p H,adsorbate concentration,adsorbent mass and temperature on the adsorption of Co²⁺and Mn²⁺were studied.The results showed that the adsorption of Co²⁺and Mn²⁺on PAM/PHC/n-Fe₃O₄ is a rapid kinetic equilibrium process,which is more in line with the quasi second-order kinetic model.Freundlich isothermal model can better describe the adsorption process of Co²⁺and Mn²⁺on PAM/PHC/n-Fe₃O₄.The adsorption process is a spontaneous endothermic reaction,the temperature rise is conducive to the adsorption of Co²⁺and Mn²⁺.The adsorption mechanism of PAM/PHC/n-Fe₃O₄to Co²⁺and Mn²⁺is physical adsorption.Through the comparative study of the adsorption properties of n-Fe₃O₄,PHC,PAM/PHC,PAM/PHC/n-Fe₃O₄ for Co²⁺,Mn²⁺under the same conditions,tt was found that PAM/PHC/n-Fe₃O₄ has the largest adsorption capacity for Co²⁺,Mn²⁺which proved that the magnetization modification effect is more excellent and has better magnetism.After adsorption of Co²⁺and Mn²⁺,the magnetic adsorbent can be removed by magnetic field.