Atomic force microscopy study of ultrafiltration membranes: solute interactions and fouling in pulp and paper processing

Atomic force microscopy (AFM) has been used to quantify directly the interaction (adhesion) of cellubiose and cellulose with two polymeric ultrafiltration membranes of similar molecular weight cut-off (MWCO) but different materials (ES404 and EM006, PCI Membranes, UK). Membrane ES404 is made from polyethersulphone alone and EM006 is made of a polyethersulphone-polyacrylate blend chosen specifically to increase the hydrophilic properties and decrease the fouling properties of the membrane. Cellubiose-modified silica probes were used to quantify the interaction of cellubiose with the clean membranes. Pure cellulose probes were used to quantify the interaction of cellulose with both clean and cellubiose-fouled membranes. All measurements were made in 10(-2) m NaCl solution. It was found that the cellubiose-modified probes had three times greater adhesion with the ES404 than with the EM006 membrane. The pure cellulose probe also had greater adhesion with the ES404 membrane. Cellubiose fouling of both membranes gave close to an order of magnitude increase in the adhesion of the cellulose probe. The results show how AFM in conjunction with the colloid probe technique can elucidate surface interactions in solution, in particular how macromolecular adsorption can modify the subsequent adhesion of particulates. Copyright (C) 2002 John Wiley Sons, Ltd.