Facile and Sustainable Polyethylenimine Modification of Polyamide Reverse Osmosis Membranes for High-Performance CO₂/N₂ Separation

This work introduces a polyethylenimine (PEI)-based modification of polyamide (PA) reverse osmosis (RO) membranes, which significantly enhances CO2 permeance and CO2/N2 selectivity. The optimized membranes achieve a CO2 permeance of 97 GPU and a selectivity of 90, representing substantial performance improvements. Crucially, this facile, green, and scalable modification is directly applicable to the regeneration and recycling of aged or discarded water treatment membranes, thereby extending the membrane lifecycle and promoting industrial resource sustainability. Moreover, controlled membrane hydration dramatically improved operational stability, extending effective membrane performance from 3 to 18 h. This work provides a practical and scalable strategy for addressing both gas separation challenges and the growing environmental burden of end-of-life membrane disposal in the water treatment sector.