Accelerated Solvent Extraction for Plastic Recycling: Modeling the Mass-Transfer Kinetics of the Separation of Phthalates from Poly(vinyl Chloride)

A major challenge of poly(vinyl chloride) (PVC) recycling is the prevalence of “legacy” additives, such as certain phthalate plasticizers. Deformulation seeks the separation of these additives using solvent-based technologies to obtain materials more suitable for reincorporation in the value chain. In this scope, this work explores the potential of accelerated solvent extraction (ASE) for the separation of phthalate plasticizers from PVC. Several model and real-world PVC feedstocks underwent ASE experiments, using mass balance and gas chromatography using flame ionization detection to determine how ASE and extraction profiles can be affected by factors such as temperature, solvent composition, and plastic formulation. A Fickian model was fitted to each kinetic extraction profile to estimate the diffusivity of the phthalate plasticizers across PVC and the partition coefficient across the solvent-PVC interface. Distinct kinetic profiles highlight the influence of plasticizer side-chain structure and initial concentration for ASE yield and the benefits of adding a swelling agent as cosolvent. These results benefit the knowledge of plastic-related ASE applications and demonstrate that ASE could be an asset as a part of the PVC deformulation recycling processes.