Ultra-thin covering to modify membranes

Although the material has an important role in determining the characteristics of a membrane, modification of its surface alone can bring new properties as well.

A group of researchers, including Nidal Hilal from the University of Nottingham, used the interfacial polymerization technique to produce modified polyethersulphone membranes. Interfacial polymerization is a reaction that forms an extremely thin layer over the membrane, which can change its efficiency considerably. The study explored the effects of different concentrations of the monomer used to form the layer, and different periods of time for the reaction, to determine the influence of these variables on the antifouling properties of the membrane.

Contrary to the unmodified membranes, the researchers found that the modified ones showed no irreversible fouling from humic acid in a neutral environment. In fact, some of them performed better after being subjected to humic acid, becoming more permeable to water. Using a higher concentration of the monomer or a longer reaction time led to a decrease in the water permeance of the modified membranes under these conditions, due to the formation of a denser surface.

However, in acidic media, all the modified membranes were found to be more susceptible to irreversible fouling than the unmodified ones. Under these conditions, the membranes with the highest monomer concentration showed less irreversible fouling than the others.

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