Experimental Study On Adsorption Of U(?) In Water By Manganese Dioxide/Iron Hydroxide Composite

In the process of uranium mining and metallurgy,a large amount of low concentration uranium wastewater will be produced,which poses a potential danger to human health and the surrounding ecological environment.The adsorption method has potential advantages in the treatment of uranium-containing wastewater due to its advantages such as low cost,good selectivity,convenient operation,and high treatment efficiency.The key to the adsorption method is to select an appropriate adsorbent,and it is an important point to find a cheap and effective adsorbent.In this study,MnO₂/FeOOH composites were prepared by cross-linking hydroxyl oxidize iron?FeOOH?on manganese dioxide?MnO₂?and its adsorption properties and mechanisma for U???were explored.The following results were obtained.?1??-MnO₂ was prepared by KMnO₄ oxidation of MnSO₄.The effects of pH,adsorption time and other factors on the adsorption of U???by?-MnO₂ were investigated.The results show that when the initial U???concentration is 10 mg/L,the dosage is 150 mg/L,temperature is 30?at pH=5 for 120 min,the maximum removal efficiency of?-MnO₂ for U???is up to 83.0%.The adsorption thermodynamics and adsorption kinetics studies show that the adsorption process of MnO₂/FeOOH for U???is fitted well to the Freundlich isotherm model and the quasi-secondary kinetic model,and it is spontaneous and endothermic.?2?MnO₂/FeOOH can be prepared by the chemical deposition method.The experimental results show that when the initial U???concentration is 10 mg/L,Fe/Mn molar ratio is 1/2,the dosage is 150 mg/L,temperature is 30?at pH=5 for 120 min,the maximum removal efficiency of MnO₂/FeOOH for U???is up to 97.7%,and it is 14.7%higher than MnO₂.The adsorption process of U???by MnO₂/FeOOH is spontaneous and endothermic.The kinetics conforms to the quasi-second-order kinetic model and the isotherm conforms to both the Langmuir model and the Freundlich model.At different interference ion concentrations?10¹50 mg/L?,various ions have different degrees of inhibition on the adsorption of U???on MnO₂/FeOOH.Among them,the inhibition of Ca²⁺and Cu²⁺is obvious,and the inhibitory effect increases with the increase of its concentration.However,SO₄^2-,CO₃^2-and Fe³⁺have almost no effect on the adsorption of U???by MnO₂/FeOOH.Desorption test results show that MnO₂/FeOOH has good recyclability.FTIR and XPS analysis show that the adsorption mechanisms of MnO₂/FeOOH are mainly due to the coordination of surface hydroxyl groups and Mn-O bonds with U???.