Rapid Upcycling of End-of-Life Microfiltration Membrane Mediated by the Healing of Metal–Organic Complex

Membrane separation is widely adopted in many industries, and the membranes reach their end of life (EOL) after long-term use. However, the conventional approach of replacing EOL membranes has a high carbon footprint, hindering the development of a green, low-carbon, and carbon-neutral process. In this study, we developed a cleaning–tannic acid-iron (TA-Fe)-healing–interfacial polymerization strategy with a reaction time of less than 20 min for the upcycling of an EOL microfiltration (MF) membrane. The cleaning step could remove most of the foulants from the EOL membrane. The TA-Fe healing step decreased the surface pore size and increased the hydrophilicity of the cleaned membrane, offering a more favorable platform for the storage of amine monomers required for interfacial polymerization. The upcycled NF-Healed membrane possessed a Na₂SO₄ rejection of 96.9 ± 0.7% and high pure water permeance of 23.7 ± 1.4 L m^–2 h^–1 bar^–1. An economic analysis indicated that the chemical cost for upcycling was ∼$4.9/m² membrane, which was lower than the estimated cost to replace the EOL MF membrane. This study provides a rapid and cost-effective method for the upcycling of the EOL MF membrane, which is a promising strategy to close the sustainable loop in the membrane materials.