NOM fouling behavior during ultrafiltration: Effect of membrane hydrophilicity

Abstract

Polyethylene oxide (PEO)-modified ultrafiltration (UF) membranes were prepared using polyacrylonitrile-graft-polyethylene oxide (PAN-g-PEO) copolymers through immersion precipitation phase inversion method. Compared to PAN membrane, the PEO-modified UF membranes possessed extraordinary hydrophilic surface owing to the enrichment of PEO segments, which was confirmed by X-ray photoelectronic spectroscopy (XPS). The effects of membrane hydrophilicity on the organic fouling resistance were investigated by means of the resistance-in-series model. The results showed that the hydrophilic modification of UF membrane contributed to the fouling control in bovine serum albumin (BSA) and Escherichia coli (E. coli) bacteria filtration. The antifouling ability of the membranes increased with increasing PEO content. The pure water flux could recover completely after filtering BSA and bacteria, respectively, for the membranes with 25.2% and 8.5% PEO content. In contract, the increase of membrane hydrophilicity had a negative effect on the humic acid (HA) and sodium alginate (SA) filtration. The membrane permeability of the PAN membrane unexpectedly increased after HA or SA filtration, while the flux recovery ratio of PEO-modified membranes decreased with increasing PEO content. The differences in fouling behavior of the various organic foulants on hydrophobic or hydrophilic membrane were attributed to the nature of organic foulants and their interaction with membranes.