Radiation-induced cross-linking: a novel avenue to permanent 3D modification of polymeric membranes

Membrane fouling is always the biggest problem in the practice of membrane separation technologies, which strongly impacts their applicability, separation efficiency, cost effectiveness, and service lifespan. Herein, a simple but effective 3D modification approach was designed for permanently functionalizing polymeric membranes by directly cross-linking polyvinyl alcohol (PVA) under gamma-ray irradiation at room temperature without any additives. After the modification, a PVA layer was constructed on the membrane surface and the pore inner surface of polyvinylidene fluoride (PVDF) membranes. This endowed them with good hydrophilicity, low adsorption of protein model foulants, and easy recoverability properties. In addition, the pore size and distribution were customized by controlling the PVA concentration, which enhanced the rejection ability of the resultant membranes and converted them from microfiltration to ultrafiltration. The cross-linked PVA layer was equipped with the resultant membranes with good resistance to chemical cleaning by acidic, alkaline, and oxidative reagents, which could greatly prolong the membrane service lifetime. Furthermore, this approach was demonstrated as a universal method to modify PVDF membranes with other hydrophilic macromolecular modifiers, including polyethylene glycol, sodium alginate, and polyvinyl pyrrolidone. This modification of the membranes effectively endowed them with good hydrophilicity and antifouling properties, as expected.