Study On The Preparation Of Polyacrylonitrile Composite Materials And The Adsorption Properties

Traditional energy sources are not renewable.With the continuous exploitation of fossil energy,they will be exhausted one day.At present,the only form of energy that can replace traditional fossil energy on a large scale is nuclear power.As nuclear energy technology matures,access to uranium,the main raw material for nuclear power,needs to be broadened.There are far less uranium resources stored on the land than in the ocean.To separate and enrich the uranium in the sea can increase the reserves of uranium resources,promote energy security and strengthen the competitiveness of China's nuclear power industry.The main research object of this paper is polyacrylonitrile fiber materials.Three fiber adsorbent materials were prepared by cross-linking reaction,and the fiber materials's morphological structure were characterized by scanning electron microscope(SEM)and Fourier transform infrared spectroscopy(FT-IR).The effects of p H,contact time,temperature and initial uranium concentration on the uranium adsorption properties of the prepared fiber material were also studied.Gallic acid was cross-linked to polyacrylonitrile fiber,and the polyacrylonitrile fiber adsorbent material modified by gallic acid(PAN-GA)was successfully prepared.The adsorption experiments show that the PAN-GA fiber reached the optimal adsorption value when the solution p H was 7.0;the maximum adsorption value of the fiber at room temperature was366.3 mg·g^-1;the fiber material conformed to the quasi-second-order kinetic model,Chemical adsorption occupied the main part of its uranium adsorption process;PAN-GA fiber materials showed good selectivity in the ion competition experiment.The polyacrylonitrile fiber was hydrolyzed with sodium hydroxide,and then melamine was cross-linked to the polyacrylonitrile fiber,and a melamine-modified polyacrylonitrile fiber material(PAN-MA)with good recycling performance was successfully prepared.After chemical modification,the material still retained the basic shape of the fiber,indicating that it has good stability;after 5 times of absorption-desorption cycle experiments,the uranium adsorption capacity of the fiber material decreased by 30.2 mg·g^-1.It shows that the material has excellent recycling performance;under laboratory conditions,the maximum adsorption capacity of the material can reach 387 mg·g^-1;under simulated seawater conditions,the adsorption efficiency of PAN-MA fiber for low concentration uranium more than 80%.The polyacrylonitrile fiber was coated with polydopamine,and then the fiber material was modified with?-cyclodextrin to prepare the polydopamine-coated polyacrylonitrile fiber adsorbent material(PAN-PDA-?-CD).According to the results of the adsorption experiment,the maximum adsorption capacity of PAN-PDA-?-CD fiber material reached 400.4 mg·g^-1;in the ion competition experiment,the adsorption rate of PAN-PDA-?-CD fiber material to uranyl ions was close 85%,which proves that it has good selectivity;when the concentration of uranyl ions in the solution was low,the fiber material also showed good adsorption capacity,indicating that it has certain potential for practical application.