Membrane-based nanopurification for plastic recycling.

Purification technologies that remove contaminants from waste plastics are critical to increasing plastic recyclability. Mechanical recycling cannot remove embedded additives, dissolution methods are limited by additive-polymer compatibility and chemical recycling requires strict control of contamination to prevent undesired reactions. This work introduces a membrane-based size-exclusion process that exploits a key property of plastics: polymer molecules typically have a molecular weight significantly higher than that of common additives. A case study using ceramic tubular ultrafiltration membranes demonstrates removal of over 90% of hexabromocyclododecane (HBCD) from both virgin and post-consumer polystyrene, while also eliminating polymer tailings originating from degraded polymer chains. By targeting the size difference between polymers and additives, this approach opens new opportunities for regeneration of plastics and offers a pathway to broader recyclability. Applied to common plastics such as PE, PP, PS, PVC, and PU, this framework could increase the fraction of recycled plastics from ~9% to over 68.5%.