Plasma-induced physicochemical effects on a poly(amide) thin-film composite membrane

Abstract

Helium and water gas plasma were used to modify the surface morphology and chemistry of commercial thin film composite membranes. Such surface treatment is a convenient tool to alter performance of the membranes and subsequently reduce interactions with contaminants in solution. Plasma reactions such as etching and re-deposition resulted in surface functionalization and texturation which were correlated with membrane flux and salt rejection changes. Investigations conducted using atomic force microscopy revealed morphology alterations which were apparent as either smoother surfaces or rougher surfaces. While the smoothing was attributed to a re-deposition of polymer material, which originated most likely from vaporization of surface polymer, the roughening was a result from balanced plasma surface reactions. The beneficial etching can occur under certain conditions when helium is used in conjunction with low excitation power, which resulted in flux enhancements up to 66% (i.e. from 30L.m−2.h−1 to 50L.m−2.h−1) with 98% rejection. The hydrophilicity was dramatically increased from 46.6° to as low as 8.9° after 5min of helium plasma duration. The impact that plasma treatments have on the nascent structure was discussed in order to highlight its application as a convenient tool to functionalize the surface of thin film composite membranes.