The influence of morphology, hydrophobicity and charge upon the long-term performance of ultrafiltration membranes fouled with spent sulphite liquor

A membranes hydrophobicity, surface roughness and charge can all affect its tendency to foul and its subsequent cleanability. In this study polysulphone (PSf), polyethersulphone (PES) and regenerated cellulose (RC) ultrafiltration (UF) membranes were fouled with spent sulphite liquor (SSL) and cleaned with sodium hydroxide and Ultrasil 11 (Henkel Ecolab) over several operational cycles until a steady-state was reached. Fouling and cleaning mechanisms were evaluated using Fourier Transform Infira Red (FTIR) spectral peak heights, zeta potential and contact angle measurements. Polysulphone (PSf) membranes displayed a much large flux decline than polyethersulphone (PES) membranes that are smoother and of a similar hydrophobicity. The greater the available surface area (due to the roughness) the stronger the interaction between membrane material, foulants and cleaning agents is likely to be. Regenerated cellulose (RC), has a similar roughness to PSf but is much more hydrophilic. RC membranes displayed the smaller flux decline of the two membranes examined, demonstrating the importance of hydrophilicity in reducing fouling by the SSL feed.