Preparation Of Functionalized Composite Materials And Study On Uranium Adsorption Properties

Nuclear energy is a new type of clean energy and an important alternative energy to solve the problem of environmental pollution.Uranium is the main raw material of nuclear energy,so the recovery and extraction of uranium is of great significance to the development of nuclear energy.In response to the severe shortage of uranium stocks on land,Marine uranium resources have been developed to compensate for the increasing consumption of nuclear fuel.However,the ultra-low uranium concentration（about 3.3 ppb）and the existence of a large number of competing ions severely limit the exploitation and utilization of Marine uranium resources.In recent years,scientists have tried various methods to enrich uranium from seawater,but considering the extraction rate of uranium,the stability and selectivity of the material in the Marine environment,they believe adsorption is the most efficient way to extract uranium from seawater.In this paper,a series of adsorbents were prepared and used to simulate the adsorption of uranium in seawater,so as to study their practical application potential.1.The amidoxime functional groups were effectively grafted onto magnetic MXene and chitosan（CS）composites（M-OH/CS/Fe₃O₄-AO）,which could achieve solid-liquid separation under the action of external magnets.Batch adsorption experiments showed that at p H=4 and T=298 K,the adsorbent reached equilibrium within 2 h with a maximum adsorption capacity of 1305.7 mg·g^-1,and had good selectivity.Langmuir isothermal adsorption model proved that the adsorption process was a single molecular layer chemisorption.It is worth mentioning that M-OH/CS/Fe₃O₄-AO has excellent antibacterial performance in simulated seawater,and the adsorption capacity reaches 6.6 mg·g^-1.FT-IR and XPS analysis showed that uranyl ions in solution were mainly coordinated with amidoxime,amino and hydroxyl functional groups.2.MXene-COOH/PAM/ZIF-8 composites were prepared by cross-linking polyacrylamide（PAM）to increase the layer spacing between carboxylated MXene sheets,and then loading ZIF-8 in situ.The experimental results showed that the maximum adsorption capacity of MXene-COOH/PAM/ZIF-8 reached 909.5 mg·g^-1at p H=4 and T=298 K.The adsorption capacity and adsorption rate of MXene-COOH/PAM/ZIF-8 were not only large,but also able to selectively adsorb uranium in a variety of coexisting ion solutions.The mechanism study shows that the material can not only use PAM to coordinate with amino and Zn-O in ZIF-8 to uranyl ion,but also increase the hydrophilicity and adsorption capacity of the adsorbent after carboxylation of MXene.3.By using chitosan as the first network and acrylamide as the second network through MBA crosslinking to form polyacrylamide,three-dimensional double-network structure of hydrogel with large specific surface area was prepared.The hydrogel of CP-AO hydrogel with aminoxime has large adsorption capacity and selectivity,and the adsorption rate is fast.The equilibrium is almost reached within 2h in 100 mg·L^-1uranium solution,and the maximum adsorption capacity is 886.7mg·g^-1.The uranium adsorption process of CP-AO follows the quasi-second-order kinetic model and Langmuir isothermal adsorption model,indicating that the adsorption process belongs to spontaneous single molecular layer chemisorption.In addition,the double network structure makes the adsorbent have good mechanical properties,and can be recycled every time without causing secondary pollution.