Preparations Of Biodegradable Beads And Their Separation Behaviors For U（Ⅵ） And Th（Ⅳ） In Aqueous Phase

A century has passed since the discovery and application of nuclear energy,but the safe and effective disposal of radioactive waste from the nuclear industry still matained key question.Uranium and thorium are one of the core raw materials in nuclear energy and the main components of radioactive waste.It is of great significance to study the ways and methods of enrichment and separation.Additionally,the recycling method of the enriched and separated materials after the completion of the mission is also a topic that needs to pay attention.In this paper,functional carboxymethyl cellulose hydrogel-beads with a diameter of 1.0 mm to 2.5 mm were synthesized by using carboxymethyl cellulose as a biomacromolecular material,amidoxime modification and ion crosslinking method.The structure and characteristics of cellulose hydrogel beads of oximated carboxymethyl cellulose were studied by means of infrared spectroscopy,elemental analysis,X-ray photoelectron spectroscopy,scanning electron microscopy,thermogravimetric analysis and specific surface area.Firstly,the swelling experiment of the synthesized hydrogel-beads was investigated.Including the conditions like the different particle size,pH value,time,ionic strength,ion type and environmental system on the swelling degree of the hydrogel-beads.The results show that the hydrogel-beads of oximated carboxymethyl cellulose have certain swelling resistance,mechanical properties and recovery properties under extreme conditions.Biodegradation experiments show that bacteria,even better than the raw material carboxymethyl cellulose,can effectively degrade the material.The effects of functionalized materials on the adsorption process of uranyl nitrate,uranyl carbonate and thorium nitrate under the conditions of adsorbent mass,ionic strength,pH,time,initial concentration,temperature,the ions selectivity and desorption behavior of U（Ⅵ）and Th（Ⅳ）were investigated by static adsorption batch experiments.The kinetic fitting results show that the adsorption process of uranyl nitrate,uranyl carbonate and thorium nitrate by ACB correspond to the quasi-second-order kinetic model,and the adsorption energy of uranyl carbonate reaches equilibrium at 1 h.The results of adsorption isothermal fitting show that the adsorption process of uranyl nitrate,uranyl carbonate and thorium nitrate by ACB consistent with Langmuir model.The experiment and model also indicate that the maximum adsorption capacity of ACB can reach 303mg/g at 25°C.According to the thermodynamic fitting parametersΔG~0,ΔH~0 andΔS~0,the three adsorption processes are endothermic reactions.When coexisting with other metal ions at the same initial concentration,ACB has certain selective adsorption on U（Ⅵ）and Th（Ⅳ）,in which--.The four functional materials can effectively adsorb and desorb U（Ⅵ）at low acidity（0.06-0.1 mol/L HNO₃）,and the recycle time can reach seven times.