Fabrication Of Porous Adsorbents Based On Onestep Double Emulsion Droplet Reactor And Study On Its Lithium Selectivity Adsorption Performance

The reserves of lithium resources in China are among the top in the world.There are abundant lithium resources in salt-lake brine in Qinghai and Tibet,but the backward capacity of lithium production is not directly proportional to the reserves,making half of the raw materials of lithium depend on import.Therefore,in order to ensure the sustainable supply of lithium resources in China,it is of great significance to explore a green,efficient and low-cost separation technology to extract lithium from salt-lake brine.This thesis is aimed at the complex salt-lake brine,by selecting a suitable one-step emulsified double emulsion as a reactor to prepare porous polymer materials with high physical and chemical stability,high specific surface area and low mass density.Using the special"size matching"mechanism between 12C4crown ethers with Li⁺as functional sites for selective separation,chemical modification modified them on the surface of porous materials,and explored its adsorption of Li⁺on salt-lake brine through adsorption performance and mechanism of action.In this work,the selection of emulsifier,the adjustment of oil-water two-phase volume fraction and the stability conditions of emulsion in the preparation process of double emulsion droplet reactors were explored in detail,and the morphology,structure composition,surface wettability and other properties of the porous materials were characterized and analyzed.The selective recognition and separation ability of crown ether functionalized adsorbents for Li⁺were investigated by batch adsorption experiments.The main research contents are as follows:（1）An appropriate amphiphilic emulsifier was constructed through the supramolecular interaction between the pyridinyl group of block copolymer polystyrene-b-polyvinyl pyridinyl（PS-b-P4VP）and the carboxyl group of trifluoroacetic acid（CF₃COOH）,and then water-in-oil-in-water（W/O/W）double emulsion droplet reactors were emulsified in one step.Using glycidyl methacrylate（GMA）as the functional monomer,ethylene glycol dimethacrylate（EGDMA）as the crosslinker and 2-hydroxy-2-methyl-1-phenyl-1-acetone（Irgacure-1173）as the initiator,the porous microspheres（Macro-GMA）were synthesized by oil phase polymerization initiated under UV light.The porous adsorbent Macro-GMA-AB12C4 for lithium extraction with surface modification of AB12C4 was prepared by amidation.The results showed that the porous morphology of Macro-GMA is closely related to the stability of the dual emulsion droplet reactor.The results of adsorption experiments showed that the adsorption of Li⁺by Macro-GMA-AB12C4 followed the quasi-second-order kinetics,and the chemical adsorption was the main absorption process.The Langmuir equation describes the adsorption equilibrium process well.The equilibrium adsorption capacity at 298 K is 38.13 mg/g.It has excellent selectivity in the coexistence test solution of Na⁺,K⁺,Mg²⁺and Ca²⁺.After five cycles of adsorption-desorption,91.14%of the equilibrium adsorption capacity of the initial adsorption was still maintained.（2）Select block copolymer PS-b-P4VP and phenyl selenium bromide（Ph Se Br）to adjust the amphiphilicity of the emulsifier under the Se-N covalent bond reaction,and then used for one-step emulsification to generate high internal phase W/O/W double emulsion droplet reactors.Secondly,GMA as the functional monomer,EGDMA as the cross-linking agent,Irgacure-1173 as the initiator,and UV light polymerization to form porous multi-cavity microspheres（PMCB）.Then,the B12C4-NH₂ crown ethers were chemically fixed on the surface of PMCB through the interface post-modification strategy to generate porous microsphere adsorbent（PMCB-B12C4）.The experimental results showed that the double emulsion droplet reactor produced by the emulsifier controlled by the covalent effect of Se-N is more stable and the pore size distribution of the polymerized product is uniform;The adsorption law of PMCB-B12C4 for Li⁺conforms to the Langmuir and Hill equations,and the equilibrium adsorption capacities are 61.35 mg/g and 59.53 mg/g respectively;significant Li⁺recovery capacity is still retained in the actual salt-lake brine（Q_e=15.23 mg/g）.（3）Halloysite nanotubes（HNTs）were hydrophobically modified by palmitoyl chloride,and stable Pickering oil-in-water-in-oil double emulsion（O/W/O）droplet reactors were formed by one-step emulsification.Using maleic anhydride（MA）as the functional monomer,N,N-methylene bisacrylamide（MBA）as the crosslinking agent,Irgacure-1173 as the initiator,and UV polymerization to produce hard hydrogel sheet PMBA-PMA.The functionalized lithium extraction adsorbent（PMBA-PMA-CE）of crown ether（B12C4-NH₂）was constructed through the chemical reaction of amino group and acid anhydride.The experimental results showed that when the p H is greater than 7.0,it is beneficial to the adsorption;the adsorption mechanism is chemical adsorption,and the adsorption equilibrium can be reached within 100 min;at 298 K,the adsorption law for Li⁺conforms to the Langmuir equation,and the equilibrium adsorption capacity is 14.67 mg/g;In addition,it also has good selectivity and regeneration performance.The introduction of cheap halloysite can not only be used as an emulsifier in one-step emulsification double emulsion droplet reactors,but also can improve the mechanical properties of hard hydrogels,reduce costs and maintain adsorption performance,showing great application potential.