The Preparation Of Functionalized Polyamidoxime-based Composite Materials And Their Uranium Adsorption Properties

The efficient and selective uranium extraction from seawater is essential to ensure the sustainable development of nuclear energy.In recent years,researchers have achieved many milestones in seawater uranium extraction.However,the preparation of highly efficient and selective,easily separable and recoverable adsorbents with excellent mechanical properties and low costs is still difficult.The amidoxime group（AO）adsorbent has been considered as an ideal adsorbent for industrial seawater uranium extraction,but the uranium capacity needs to be improved and the affinity of AO for vanadium present in seawater is still higher than that of uranium,which limits AO application.In this work,a new type of polyamidoxime（PAO）photothermal composite hydrogel-based uranium adsorption material was constructed.The PAO was prepared into hydrogel,and the photothermal conversion material was introduced into it.So that while ensuring the high uranium adsorption capacity of the hydrogel,the photothermal effect can also improve the selectivity for uranium and reduce the selectivity for vanadium.Moreover,the preparation of hydrogels requires no complex process and has low cost,which is expected to be mass produced.The main research results are as follows:1.A new type of photothermal polyamidoxime semi-interpenetrating network hydrogel uranium adsorbent（PAO-GO/PAM）based on polyamidoxime（PAO）,acrylamide（AM）and graphite oxide（GO）was environmentally friendly,low-energy,simply and quickly prepared by UV free radical polymerization.The adsorption results showed that the hydrogel prepared with the1.5 mg·L^-1 of GO and 50 wt.%PAO respectively had high uranium adsorption capacity and photothermal conversion efficiency.Based on the endothermic adsorption behavior of AO on uranium,it can be seen that the rapid increase in temperature of PAO₅₀-GO_1.5/PAM under light can simultaneously meet the requirements of high adsorption capacity(396.82 mg·g^-1)of the adsorbent and selectivity for uranium over vanadium(K_d（U）/K_d（V）=3.61).After three adsorption desorption cycles,the adsorbent still maintained a high adsorption capacity(293.68 mg·g^-1)under light,significantly higher than the adsorption capacity under dark(254.21 mg·g^-1),and the uranium desorption efficiency can still maintain at 90.32%（light）and 87.21%（dark）.2.A new double network gelatin-Fe₃O₄/polyamidoxime magnetic photothermal composite hydrogel adsorbent（Gel-Fe₃O₄/PAO）was prepared.The addition of Fe₃O₄ enables the hydrogel to have photothermal conversion and magnetic manipulation properties,facilitating the separation and recovery of hydrogel.Simultaneously,the double network structure（physical crosslinked gelatin and chemical crosslinked PAM network）enables hydrogel to have excellent tensile strength and self-healing ability.The adsorption results showed that the hydrogel prepared with 16 wt.%Gel and 1.5 wt.%Fe₃O₄ had high uranium adsorption capacity and photothermal conversion efficiency.The rapid rise of hydrogel temperature under simulated light can meet the requirements of high adsorption capacity of adsorbent(469.48 mg·g^-1)and selectivity of uranium over vanadium(K_d（U）/K_d（V）=2.77)simultaneously.After four adsorption desorption cycles under simulated sunlight and dark,the uranium desorption efficiency remained above 83.11%and 80.24%,respectively.Moreover,after four cycles of sunlight,the adsorbent still reached a high adsorption capacity(332.54 mg·g^-1)under light,significantly higher than the adsorption capacity under dark(255.96 mg·g^-1).