Direct effects of interlayer on organic micropollutants removal by thin-film nanocomposite membranes

Abstract

The enhanced rejection of organic micropollutants (OMPs) by the interlayered thin-film nanocomposite (TFNi) membranes is commonly attributed to the polyamide layer, which is better formed under the influence of an interlayer. However, the role of the interlayer in directly serving as a barrier layer to OMPs is seldom reported. To investigate such direct effects, we adopted iron-tannic acid (Fe-TA) complex as a model interlayer targeting OMPs removal, and prepared identical polyamide nanofilms for both the control and TFNi membranes at a support-free interface to minimize the impact of interlayer on the polyamide formation. The experimental result shows that, although at the expense of sacrificing water permeance, the interlayer can directly serve as a barrier layer to some OMPs, especially those that cannot be easily removed by the polyamide layer alone, due to the inherent hotspot of polyamide material. A theoretical analysis further suggests that, to enhance the OMPs removal by exerting such direct effects, an ideal interlayer should be more intrinsically selective to OMPs and meanwhile impose moderate resistance to water compared with the polyamide layer. This work may provide insight into the role of interlayers in removing OMPs by TFNi membranes and enlighten the fit-for-purpose design of high-performance membranes toward environmental applications.