Synthesis Of Novel Layered Vanadates And Study Of Strontium And Cesium Adsorption Behavior And Mechanism

The development and utilization of nuclear energy can promote the development of science and technology and alleviate the energy shortage,but a large amount of radioactive wastewater is generated during the use of nuclear energy and technology,which contains the radionuclides strontium and cesium with long half-lives and high risks to human health and environmental safety.Therefore,designing efficient adsorbents to separate the nuclides strontium and cesium from contaminated water has attracted the attention of a large number of researchers.Layered metal oxides,as a class of anionic layered materials,consist of negatively charged host layers and flexible interlayer charge-compensating cations.It has excellent cation exchange capacity and flexible interlayer space,and has been widely used to remove nuclides in radioactive water.Compared with other transition metal oxides,layered vanadates are more stable under acidic conditions and can still maintain high adsorption capacity at p H=2.This research mainly investigates the synthesis and preparation of layered NH₄V₄O₁₀ and Mg_0.17V₂O₅·0.83H₂O,and studies their adsorption properties and principles for strontium and cesium in complex water.The details are as follows:（1）Different morphologies of NH₄V₄O₁₀ were synthesized by varying the ratio of dipropylamine to ammonium metavanadate using a one-step hydrothermal synthesis method.The results showed that the maximum adsorption capacities of NH₄V₄O₁₀ for Sr²⁺and Cs⁺were 192.52 mg/g and251.09 mg/g,respectively,at room temperature,and the adsorption equilibrium times were 3 h and 1 h,respectively.The adsorbent can maintain good adsorption capacity in a wide p H range.In the presence of other competing ions,NH₄V₄O₁₀ exhibited high selectivity for both Sr²⁺and Cs⁺,indicating that the adsorbent can be used in various complex water environments.Using first-principles calculations based on density functional theory,the results show that the adsorption energy of Cs⁺is-6.35 e V,which is the lowest energy after the adsorbent is exchanged with coexisting ions.Finally,by means of EDS,XRD,FT-IR,XPS and potential,it is clarified that the adsorption mechanism of Sr²⁺and Cs⁺by NH₄V₄O₁₀ is mainly electrostatic interaction and ion exchange.（2）The Mg²⁺intercalated Mg_0.17V₂O₅·0.83H₂O adsorbent was synthesized by a one-step hydrothermal synthesis method.The research results show that the maximum interlayer spacing corresponding to Mg_0.17V₂O₅·0.83H₂O is 13.6?,and its adsorption equilibrium time for Sr²⁺and Cs⁺is 1 h and 2 min,respectively.Compared with other layered adsorbents,its adsorption speed is greatly improved.The adsorption capacities of Mg_0.17V₂O₅·0.83H₂O for Sr²⁺and Cs⁺were 315.68 mg/g and 215.31 mg/g,respectively.In addition,the cyclic regeneration experiment of adsorbing Cs⁺showed that the capacity of the adsorbent remained basically unchanged after being reused for 5 times,and the adsorbent showed excellent removal capacity for Sr and Cs in a variety of complex water environments.By means of EDS,XRD,FT-IR,XPS and potential analysis,it is clarified that the adsorption mechanism of Sr²⁺by Mg_0.17V₂O₅·0.83H₂O is mainly electrostatic interaction and ion exchange,while the adsorption of Cs⁺is electrostatic attraction.