Understanding phenolic transfer from NADES to PHBV for solvent recycling: role of solvation and partitioning

The recovery of extracted phenolic compounds from natural deep eutectic solvents (NADES) remains a key challenge for solvent recycling and downstream valorization. Here, the transfer of phenolic compounds from choline chloride : lactic acid containing 10 wt% H₂O (ChLA) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was investigated using catechin, ferulic acid, and naringenin as model compounds. No detectable sorption occurred from ChLA, whereas water dilution enabled partition-driven transfer. Sorption was structure-dependent, reaching 82 ± 1% for naringenin and 14 ± 1% for ferulic acid in ChLA : H₂O (1 : 3, v/v), while catechin was not transferred. Molecular dynamics simulations revealed that naringenin is stabilized in ChLA by hydrogen bonding with lactic acid and preferential associations of choline with its aromatic moiety. Radial distribution function (RDF), hydrogen-bond, and diffusion analyses showed that water progressively replaces NADES constituents in the first solvation shell of naringenin, increasing hydration and mobility while weakening preferential solvation. Naringenin sorption was linear between 5-100 mg L^-1, with a distribution coefficient of 0.0948 L g^-1. A phase-ratio model predicted the minimum PHBV loading required for efficient sorption, with theoretical and experimental thresholds of 43 and 44 g L^-1, respectively. Application to a tomato peel extract enabled 74 ± 2% naringenin recovery while maintaining 91 ± 4% extraction performance during a subsequent extraction cycle. These results establish a proof-of-concept for coupling selective phenolic recovery from NADES with PHBV sorption and solvent reuse.