Capturing lithium using functional macroporous microspheres with multiple chambers from one-step double emulsion via a tailoring supramolecular route and postsynthetic interface modification

Abstract

The recovery of lithium ion (Li+) from water lithium resources is an important step in producing raw lithium for prospective use in electrochemical storage systems. In our work, functional macroporous microspheres with multiple chambers (Macro-GMA-AB12C4) were simply prepared by multiple emulsion template for selective capture Li+. Firstly, amphiphilic supramolecular emulsifiers constructed through hydrogen bonding between polystyrene-b-polyvinylpyridine (PS-b-P4VP) and trifluoroacetic acid were used to establish W/O/W double emulsion via one-step homogenization, and then Macro-GMA-AB12C4 were fabricated from droplet template UV irradiation and postsynthetic interface modification with aminoethyl benzo-12-crown-4 (AB12C4). Taking advantages of porous structure with multiple chambers and abundant immobilized AB12C4, Macro-GMA-AB12C4 displays favorable selective adsorption performance in batch mode experiments. At pH = 6.0, Li+ adsorption onto the Macro-GMA-AB12C4 follows pseudo-second-order kinetics, and the chemisorption based on “size-match” relation is the main uptake mechanism. Adsorption isotherm of Li+ onto Macro-GMA-AB12C4 is well described by Langmuir equation, homogeneous distribution of binding sites on Macro-GMA-AB12C4 surface contributes tohigh adsorption capacity of 38.13 mg g−1 at 298 K. A specific affinity towards Li+ is also measured in the presence of Na+, K+, Mg2+, and Ca2+, or in the testing solutions with high Mg2+/Li+ ratios. The adsorption capacity slightly reduces to 91.14% after five adsorption/desorption cycles. This work not only provides a concept for the synthesis of porous sorbents by one-step multiple emulsion via supramolecular interaction, but also establishes methods for selective extraction Li+.