Selective capture of lithium on crown ether functionalized hybrid polymer nanosheets prepared by one-step emulsified Pickering O/W/O double emulsion droplet reactors

Hybrid polymer nanosheets are promising sorbents owing to large surface area, but their complicated synthesis procedure and high cost hinder to apply in particular field of selective separation. In this work, one step Pickering oil-in-water-in-oil (O/W/O) double emulsion (DE) stabilized by palmitic chloride modified halloysite nanotubes (HNTs) were firstly designed for preparing polymer nanosheets (PMBA-PMA) by UV irradiation. Subsequently, amino ethyl benzo-12-crown ether (B12C4-NH 2 ) was covalently immobilized onto the PMBA-PMA to achieve functional hybrid polymer nanosheets (PMBA-PMA-CE) for the effective and selective recovery of lithium ion (Li + ). External metastable W/O interface produced droplets’ coalescence, and the Pickering DE droplets with irregular morphology eventually initiated the formation of polymer nanosheets. PMBA-PMA-CE exhibited cured and nanosheet-like structure constructed by HNTs and polymer networks. The batch mode experiments demonstrated that the fast adsorption equilibrium of PMBA-PMA-CE towards Li + could be reached within 100 min, and the results well followed pseudo-second-order model, confirming the chemical adsorption based on "Size-match" effect. The maximum monolayer adsorption capacity calculated from Langmuir model was 14.67 mg g −1 at 298 K. Benefiting from specific “size-match” complexation, the obtained PMBA-PMA-CE possessed an excellent selectivity towards Li + even in the presence of competitive cations, and selectivity coefficient ( α ) and relative selectivity coefficient ( α r ) were greater than 1.43 and 8.29, respectively. In addition, PMBA-PMA-CE could be simply regenerated and maintained above 90% of the initial capacity after five consecutive adsorption-desorption cycles. Furthermore, the incorporation of cheap HNTs not only endowed one step emulsion DE droplets, but also improved the sorbents’ mechanical property.