Selective Adsorption Of Uranyl On Montmorillonite-iron Oxide@Zinc Oxide

The treatment of Uranium-containing（U（VI））wastewater in the environment has always attracted much attention,and U（VI）usually exists in the form of UO₂²⁺in aqueous solution.Therefore,the treatment of uranium-containing wastewater is a process of removing UO₂²⁺.Adsorption method has been widely used in the treatment of uranium-containing wastewater due to its advantages of economy and convenience,and a large number of adsorbents have been developed in previous studies.On the basis of obtaining new adsorption materials with high adsorption performance,it is also worthy of attention to study the influence of environmental factors on the adsorption process.In this paper,a batch test method was used to study the UO₂²⁺adsorption properties of ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT composites.The results show that the optimal adsorption pH of ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT for UO₂²⁺are 6.0,and the isoelectric points of the two are 5.7 e V and 5.6 e V,respectively,using the Zeta surface potential testing.The adsorption kinetics and isotherm adsorption experiment results show that the adsorption process between ZnO@MFe₂O₄,ZnO/MFe₂O₄-MMT and UO₂²⁺is fitted to the quasi-second-order kinetic model and Langmuir isotherm adsorption model,indicating that UO₂²⁺is mainly adsorbed on the surface of the sample monolayer,and the chemical adsorption process is the main adsorption method,therein,the maximum adsorption capacity of Langmuir is 304.88mg·g^-1 and 197.24 mg·g^-1,respectively.Competitive adsorption experiments show that ZnO@MFe₂O₄ has obvious selective adsorption to UO₂²⁺(187.90 mg·g^-1).The Langmuir maximum selective adsorption capacity of ZnO/MFe₂O₄-MMT for UO₂²⁺is 146.41 mg·g^-1,the Freundlich selective adsorption capacity for Cu²⁺is 40.56 mg·g^-1,and the Dubinin-Radushkevich（D-R）maximum selective adsorption capacity for UO₂²⁺and Mn²⁺can reach194.64 mg·g^-1 and 328.74 mg·g^-1,respectively.Under the HA-mediated state,the optimal adsorption pH=5.0,kinetic experiments and adsorption isotherms show that the adsorption of UO₂²⁺on ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT are still dominated by surface monolayer adsorption and chemical adsorption.Their Langmuir largest adsorption capacities were 418.41mg·g^-1 and 462.96 mg·g^-1,respectively,indicating that HA effectively enhanced the adsorption capacity of the sample for UO₂²⁺.In the competitive adsorption experiment with HA existing,the actual selective adsorption capacity of ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT for UO₂²⁺can reach 408.24 mg·g^-1 and 389.25 mg·g^-1,respectively.ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT composites have high UO₂²⁺adsorption capacity and selectivity.Humic acid can greatly increase the UO₂²⁺adsorption capacity of the adsorbent,which is also worthy of attention.Therefore,ZnO@MFe₂O₄ and ZnO/MFe₂O₄-MMT are promising new composite materials in the field of uranium-containing wastewater treatment.