Controlled architecture of macrocyclic ligand functionalized polymer brushes from glass fibers using surface-initiated ICAR ATRP technique for adsorptive separation of lithium isotopes

Abstract

By combining surface-initiated atom transfer radical polymerization (SI-ATRP) with mussel-inspired polydopamine (PDA) chemistry, controlled growth of macrocyclic ligands decorated polymer brushes from surfaces of glass fibers was achieved for effective separation of lithium isotopes. Homogenous PDA layer were firstly deposited onto glass fiber mats (GFMs), facilitating the anchoring of ATRP initiators. Propagation of poly(glycidyl methacrylate) (PGMA) brushes from the GFMs were then initiated by using the initiators for continuous activator regeneration (ICAR) ATRP method. The abundant reactive epoxy groups in the PGMA brushes provided an ideal platform for post functionalization of the obtained composites PCGFMs. Benzo-15-crown-5 (B15C5) macrocyclic ligands, with selective binding ability to lithium ions due to the host–guest interaction, were readily introduced to PCGFMs. Adsorption behavior of the functionalized composites PCGFMs-B15C5 toward lithium isotopes was fully investigated. The adsorption of lithium onto PCGFMs-B15C5 fitted Freundlich isotherm model best, and it was a combination of chemisorption and physical adsorption for Li(I) uptake. Kinetics data for Li(I) adsorption was in good agreement with pseudo-second-order rate equation and showed a hybrid rate-limiting process including both film and inter-particle diffusion. The maximum separation factor was 1.037 ± 0.002 and it was independent of both the counter ions and solvents. Softer counter anions and lower polarity solvents in systems were beneficial for higher Li(I) removal but counterintuitive for separation factor. The synthetic strategy established in this work provided an opportunity for broadening functional chromatography extraction substrates for lithium isotopes separation.