Synthesis Of 14C4 Derivatives And Study On The Mechanism Of Selective Lithium Extraction

In this paper,three 14C4 derivatives with methyl and benzene ring functional groups,namely BC₄H₁₂-14C4（containing one benzene ring and four methyl groups）,DB14C4（containing two benzene rings）and C₈H₂₄-14C4（containing eight methyl groups）,were designed and 14C4（crown ether main ring without functional groups）and these three 14C4 derivatives were investigated.The 14C4 derivatives were synthesized,the adsorption properties of the derivatives on lithium ions were analysed,and the complexation behaviour of the crown ether derivatives with the metal ions Li⁺,Na⁺was studied by quantum chemical methods with simulations and calculations.Geometric optimisation and Single site energy calculations of crown ether derivatives and their complexes with metal ions were carried out at the M062X/def2SVP and def2TZVP levels using Gaussian16 software based on Density Function Theory.A Condensed Local Softness,a Condensed Fukui Functions and a Condensed Dual Descriptors were used to analyse the molecular reactivity and to predict the metal ion complexation sites.The complex stability was analysed in terms of the Binding energies and Gibbs free energy of formation in aqueous solution.The results show that the metal ion complexation site of crown ether is mainly on the oxygen atom of the main ring.Moreover,the complexation site of BC₄H₁₂-14C4 is on the oxygen atom of the main ring on the side of the neighbouring benzene ring.the reactivity of DB14C4 and BC₄H₁₂-14C4 is higher than that of 14C4 and C₈H₂₄-14C4.the stability of CE-Li⁺complexes is better than that of CE-Na⁺complexes under aqueous solution conditions.The conformation of dihydroxy BC₄H₁₂-14C4 at room temperature was studied using Gromocs software and the complexes of dihydroxy BC₄H₁₂-14C4 with Li⁺and Na⁺were constructed.The lowest electrostatic potential on the vd W surface of the dihydroxy BC₄H₁₂-14C4 is-74.81 kcal/mol,to which both the lone pair andp-electron clouds contribute.The hydroxyl and benzene rings can reduce the surface potential and increase the reactivity.The results of the Symmetry Adapted Perturbation Theory（SAPT）energy decomposition,Mayer bond order and RDG analysis indicate that the stability of metal ion complexes is mainly driven by electrostatics and induction.The Binding energy analysis results show that the interaction strength of crown ether with Li⁺is higher than that with Na⁺in most conformations of the dihydroxy BC₄H₁₂-14C4.The addition of butyric acid improves the stability of the complexes in the organic phase,but reduces the selective effect of crown ether on lithium ions.Dihydroxy BC₄H₁₂-14C4,as well as its methyl benzoate arm derivatives and chain polymers,were synthesised.In the Li OH solution,with an O/A ratio(V_{organic phase}/V_{aqueous phase})of 1:1 and a CE/Li of 1（CE refers to crown ether in this thesis）,the extraction of Li⁺by the dihydroxy BC₄H₁₂-14C4 was 3.93%.Under the same conditions,the extraction of Li⁺by the 14C4 arm derivative was 8.07%.In the same system,the extraction of Li⁺by the chain polymer（0.1 g,10 m L of Li OH solution）was 12.77%.The addition of butyrate as a coextractant for the lithium extraction of the lithium-sodium mixed salt system with an O/A ratio of 1:1 and a CE/Li of 1increased the extraction of dihydroxy BC₄H₁₂-14C4 from 6.08%to 20.93%for lithium and from 0.60%to 16.37%for sodium,and the Li⁺/Na⁺separation coefficient decreased from 33.25 to 1.32.Thus,the addition of butyrate Although it improved the extraction rate of Li⁺,it was not conducive to the separation of lithium and sodium.