One-step double emulsion via amphiphilic Se[sbnd]N supramolecular interactions: Towards porous multi-cavity beads for efficient recovery lithium from brine

Abstract

Efficient recovery lithium ions (Li+) from brine is a recognized challenge with potential strategic and economic implications. In this work, one-step double emulsion reactors, based on amphiphilic SeN supramolecular interactions between phenyl selenium bromide (PhSeBr) and polystyrene-b-polyvinylpyridine (PS-b-P4VP), was constructed to prepare porous multi-cavity beads (PMCB). After immobilizing aminoethyl benzo-12-crown-4 (B12C4-NH2) through post-interface modification strategy, the resultant sorbents (PMCB-B12C4) were adopted for selective separation and enrichment Li+ from brine. PMCB-B12C4 possessed surface pores, multiple interconnected chambers, and abundant crown ether receptors, and the dynamic and adjustable mechanism between structure and turning the volume fraction was also studied. Li+ adsorption in PMCB-B12C4 is best approximated by Langmuir and Hill isotherms showing the homogeneous adsorption on the heterogeneous surface, and the calculated maximum monolayer adsorption capacities are 61.35 mg g−1 and 59.53 mg g−1, respectively. Kinetic study reveals good agreement by pseudo-second order, and chemical adsorption mainly dominates the adsorption process. The mass transfer study depicts that both membrane and inter-particle diffusion are involved in a diffusion inhibition rate process. PMCB-B12C4 can selectively recovery Li+ from simulated samples with the selectivity coefficient (α) and relative selectivity coefficient (αr) as high as >5.0 and 6.0, respectively. PMCB-B12C4 still retains significant Li+ uptake capacity in brine owing to the specific “size matching” effect of crown ether. Moreover, PMCB-B12C4 is regenerated in mild acid and exhibits nearly consistent adsorption capacity after five reuse cycles. Thus, this work not only reports a new clue to fabricate porous sorbent beads via droplet reactor, but also provides a novel platform for Li+ extraction.