Performance of Fouling-Resistant Ultrafiltration (UF) Membranes Based On Self-Organizing Comb Copolymers

Fouling is one of the most critical issues that limit the use of membrane technologies in a wide range of applications. Ultrafiltration (UF) membranes cast from blends of polyacrylonitrile (PAN) and polyacrylonitrile-graft-poly(ethylene oxide) (PAN-g-PEO) have been shown to display exceptional resistance to fouling. During the immersion precipitation process, PAN-g-PEO, a comb copolymer with a hydrophobic backbone and hydrophilic side-chains, segregates to the polymer/water interface, creating a dense PEO brush on all membrane surfaces.  These membranes show no irreversible fouling when tested with a range of foulants, and recover their initial water flux completely when cleaned with only water. The technology is applicable to both flat sheet and hollow fiber membrane geometries, without post-processing or additional manufacturing equipment. This study demonstrates the fouling resistance and overall performance of these membranes with feed streams relevant to various applications, including the treatment of wastewaters from the oil and gas industry, and as a pretreatment step for seawater desalination. UF membranes in these applications effectively retain particulates, emulsified and free oil, macromolecules and other contaminants, producing high quality effluent. However, typical UF membranes experience severe flux loss, impacting their productivity. In each case, PAN-g-PEO containing membranes exhibit high fluxes, retain their permeability better, and show complete recovery of their permeability with only physical cleaning methods such as water flush or backwash, or air scouring. No chemical cleanings are needed. This degree of fouling resistance is exceptional. This membrane technology promises lower cost and improved reliability in many high fouling membrane applications.