Selective Lithium Extraction Study On Magnetic Carbon-based Surface Li~+-imprinted Materials

With the vigorous development of lithium in the fields of batteries,nuclear fusion reactors and aerospace materials,the global demand for lithium resources is increasing.A large amount of lithium resources exist in salt lake brine as liquid lithium.To meet the growing demand for lithium,the extraction of lithium resources in salt lake brine has attracted the attention of researchers.The adsorption method has broad application prospects in the extraction of lithium resources due to its advantages of simple process,economy and environmental protection.However,the composition of salt lake brine is complex,and conventional adsorbents cannot achieve the selective identification and separation of lithium ions.To improve the selectivity of the adsorbent,the surface ion imprinting technology was used to synthesize surface ion imprinted materials with selective adsorption capability.Most of the surface lithium ion imprinted materials currently are powder or granular materials.In the subsequent adsorption separation,there are problems that the materials are easily lost and the recovery is difficult.To solve these problems,in this paper,magnetic separation technology was introduced by using magnetic carbon nanospheres(Fe₃O₄@C)and their composites with graphene oxide(GO/Fe₃O₄@C),respectively,as matrix carriers,which have high surface activity and stable mechanical properties.Finally,the magnetic carbon-based surface ion imprinted materials with selectively lithium ions extraction and easily separation recycling was obtained.The specific research content and results are as follows:1.Fe₃O₄@C surface ion imprinted material(Li⁺-IIP-Fe₃O₄@C)for selective lithium extraction.First,Fe₃O₄@C obtained by solvothermal method was modified with silane coupling agent KH-570 to obtain silanized magnetic carbon nanospheres(Si-Fe₃O₄@C).Then,Si-Fe₃O₄@C was modified with methacrylic acid(MAA)to obtain magnetic carbon nanospheres modified with MAA(PMAA-Fe₃O₄@C).Finally,Li⁺-IIP-Fe₃O₄@C with uniform particle size and regular spherical morphology was obtained,using 2-hydroxymethyl-12-crown-4 coordinated with Li⁺as functional monomer,ethylene glycol dimethacrylate(EGDMA)as cross-link agent and azobisisobutyronitrile(AIBN)as initiator.Pseudo-second-order kinetic model and Langmuir isotherm adsorption model can better describe its adsorption behavior.At 25°C,Li⁺-IIP-Fe₃O₄@C has the maximum adsorption capacity reached 22.26 mg/g and a high selective adsorption for Li⁺with the selectivity coefficients of Li⁺relative to Na⁺,K⁺,and Mg²⁺of 8.06,5.72,and 2.75,respectively.After six adsorption-desorption cycle experiments,the adsorption capacity of Li⁺-IIP-Fe₃O₄@C for Li⁺only decreased by 8.8%,and showed excellent regeneration performance.2.GO/Fe₃O₄@C surface lithium ion imprinted material(Li⁺-IIP-GO/Fe₃O₄@C)for selective lithium extractionTo further impove separation recycling and construct more adsorption sites to increase the adsorption capacity,the magnetic composite carrier GO/Fe₃O₄@C was synthesized by ultrasonically combining GO with Fe₃O₄@C.Then,it is modified by KH-570 silanization to obtain KH570-GO/Fe₃O₄@C.Further,MAA-GO/Fe₃O₄@C is obtained by grafting with MAA,followed by the preparation of Li⁺-IIP-GO/Fe₃O₄@C,using 2-hydroxymethyl-12-crown-4coordinated with Li⁺as functional monomer,EGDMA as cross-link agent and AIBN initiator.The adsorption behavior of Li⁺-IIP-GO/Fe₃O₄@C for Li⁺conforms to pseudo-second-order kinetic adsorption and Langmuir isotherm adsorption.The maximum adsorption capacity is 31.24 mg/g,and it exhibits a high adsorption selectivity for Li⁺.The selectivity coefficients of Li⁺relative to Na⁺,K⁺and Mg²⁺are 14.31,12.05 and 10.9,respectively.After six adsorption-desorption cycles,the adsorption capacity only decreased by 9%,and showed excellent regeneration performance.In summary,the introduction of Fe₃O₄@C can achieve convenient separation and recovery operation after adsorption.By combining it with GO with large specific surface area and high surface activity,GO/Fe₃O₄@C magnetic composite carrier is obtained,which achieves more adsorption sites and improves adsorption effect.This paper provides a theoretical research basis and development direction for the development of advanced lithium adsorption materials.