Simultaneous optical detection and extraction of cobalt(II) from lithium ion batteries using nanocollector monoliths

This study aims to develop novel nanocollectors for potential application in cobalt [Co(II)] detection and removal from lithium ion batteries. The optical nanocollectors were fabricated through functional immobilization of 2-nitroso-1-naphthol, bis[N,N-bis(carboxymethyl) aminomethyl]fluorescein, and pyrogallol red chromophore probes into large, open, cage-pored, three-dimensional cubic mesostructures with micrometer-sized monolith particles. The monolithic nanocollectors are stable and easy to use, and they have sensitive detection capabilities for low Co(II) ion concentrations. The construction of these probes into highly ordered pore-based monoliths transform ion sensing and removal systems into smart, stable assemblies and portable laboratory assays. The experiments were conducted to determine the effects of feed solution pH, concentration, and competing ions on the selective detection and removal of Co(II) ions. Solution pH played an important role in the selective removal of Co(II) ions. The nanocollectors were able to detect Co(II) ions selectively despite high concentrations of interfering ions. The unique features of the nanocollectors allow the visual detection, removal, and extraction of ultratrace concentrations of Co(II) ions without preconcentration. The adsorbed Co(II) was eluted/extracted with stripping agents and the nanocollectors were simultaneously regenerated for subsequent removal operations after rinsing with water. The nanocollectors retained their functionality despite several chemical treatments during the removal–extraction–regeneration cycles. Therefore, large-scale pilot studies are recommended to confirm these promising results.