Effect of Ion Beam Irradiation on Two Nanofiltration Water Treatment Membranes

Abstract

Ion beam irradiation has long been recognized as an effective method for the synthesis and modification of diverse materials, including polymers. Ion beam irradiation is the bombardment of a substance with energetic ions. When the ions penetrate through the surface of a membrane, they may eliminate tall peaks and deep valleys, resulting in an overall reduction in surface roughness. Two nanofiltration membranes, one with a sulfonated polysulfone selective layer and the other with an aromatic polyamide selective layer, were used to study the effects of ion beam irradiation on surface morphology, microstructure, and performance. A beam of 25 keV H⁺ ions with four irradiation fluences (1 × 10¹³ ions/cm², 5 × 10¹³ ions/cm², 1 × 10¹⁴ ions/cm² and 5 × 10¹⁴ ions/cm²) was used for ion beam irradiation of the membrane. Atomic face microscopy (AFM) analysis show that the roughness of the membranes decreased after irradiation. An increase in flux after ion beam irradiation was also observed. Hydrophobicity, pore size distribution, and selectivity of the membrane were not affected by ion beam irradiation.

Keywords:

• Ion fluence
• irradiation
• membrane surface modifications
• surface properties
• transport properties

ACKNOWLEDGMENTS

This project was funded by the National Science Foundation grant CTS 03-31778. The authors acknowledge Dr. Peter Simpson (University of Western Ontario) and the Michigan Ion Beam Laboratory (University of Michigan) where irradiation was performed and Dr. Mark Wilf provided the membrane samples.