Preparation Of Crown Ether Modified Electrode And Study On Electrochemical Extraction Of Strontium

The disposal of nuclear waste is one of the key issues in the development of nuclear energy.Among them,the radionuclide ⁹⁰Sr has high solubility,mobility and strong biological toxicity,posing a long-term threat to environmental safety and human health.During the Fukushima nuclear accident,a large amount of ⁹⁰Sr flowed into the ocean,which attracted great attention internationally.Therefore,it is very important to remove ⁹⁰Sr from nuclear waste or polluted water.In this paper,using modification strategies such as dip coating and chemical grafting,supramolecules such as 18-crown-6-ether derivatives are modified on the surface of conductive substrates to prepare supramolecular composite electrode materials with Sr（Ⅱ）ion recognition characteristics.The effects of the physical and chemical properties of supramolecular composite electrode materials and current parameters on the electrochemical adsorption of Sr（Ⅱ）were studied.The morphology and properties of supramolecular composite electrode materials are studied by various analysis and characterization methods to clarify the electrochemical adsorption mechanism.The electrochemical adsorption of supramolecular composite electrode materials is controlled at the molecular level to achieve high-efficiency and high-selectivity adsorption and desorption of Sr（Ⅱ）,which provides a theoretical and experimental basis for the process application of electrochemical adsorption and separation of low concentration Sr（Ⅱ）in solution.The main contents are as follows:1.The dibenzo-18-crown-6-ether（DB18C6）and the polymer were heated and dissolved in N,N-dimethylformamide（DMF）to prepare a colloidal homogenate.Then the homogenate was dip-coated on the surface of carbon felt（CF）to prepare the crown ether composite membrane electrode material.The cellulose acetate（CA）crown ether composite membrane-carbon felt（CA-DB18C6@CF）electrode and the polyacrylonitrile（PAN）crown ether composite membrane-carbon felt（PAN-DB18C6@CF）electrode were prepared respectively.With the auxiliary effect of an external alternating electric field,the crown ether composite membrane electrode material can effectively adsorb and separate the low concentration of Sr（Ⅱ）in the solution.The effects of electrochemical adsorption time and initial p H of the solution were carried out respectively.The PAN-DB18C6@CF electrode reached the maximum adsorption efficiency after 15 hours of electrochemical adsorption,which was only 83.0%.The adsorption efficiency of CA-DB18C6@CF electrode can reach88.4%after 15 hours of adsorption and the optimal p H was 6.0.2.CA-DB18C6@CF electrode materials with different material ratios were prepared by dip coating method.The optimal ratio of crown ether and cellulose acetate was explored in experiments,and the pulse voltage parameters were optimized.Developed an asymmetric pulse current assisted electrochemistry（AP-CE）method,using the CA-DB18C6@CF electrode as the negative electrode and the graphite rod electrode as the positive electrode,using a two-electrode system,under the condition of an alternating electric field,to study CA-DB18C6@CF electrode simulates the adsorption of Sr（Ⅱ）in seawater.Under the optimal pulse current conditions,CA-DB18C6@CCC showed good selective adsorption performance for Sr（Ⅱ）,and the maximum Sr（Ⅱ）removal efficiency was 99.3%at 10 mg L^-1.In addition,the electrochemical method has high selectivity for the extraction of Sr（Ⅱ）in simulated seawater,which shows that the CA-DB18C6@CF electrode has excellent conductivity and ion selectivity,and it is matched with asymmetric pulse current assisted electrochemistry（AP-CE）method can efficiently extract Sr（Ⅱ）from seawater.3.The 18-membered crown ether was grafted onto the surface of the carbon felt by the diazonium chemical grafting technique to prepare a crown ether-carbon felt（CE@CF）composite electrode.The CE@CF electrode is used as the negative electrode,and the platinum electrode is used as the positive electrode.The asymmetric pulse current assisted electrochemistry（AP-CE）method can efficiently adsorb Sr（Ⅱ）ions in the aqueous solution.The modification of crown ether increased the hydrophilicity of the original carbon felt and significantly improved the selective adsorption of Sr（Ⅱ）.In addition,CE@CF electrode material has good recyclability,and under the best alternating current,the Sr（Ⅱ）removal rate and capture capacity of CE@CF material can reach 99.5%and 668.9 mg L^-1,respectively.The use of CE@CF electrode combined with AP-CE method as a fast and efficient selective extraction of Sr（Ⅱ）from complex aqueous solutions or even seawater is a promising new platform.