Probing the influence of shape and loading of CeO2 nanoparticles on the separation performance of thin-film nanocomposite membranes with an interlayer

Abstract

Constructing an interlayer in the thin-film nanocomposite (TFN) membranes has been proved to be an effective strategy to break the trade-off between permeability and selectivity. The interlayer plays an important role in the formation of polyamide (PA) layer. In this study, cerium oxide (CeO2) nanoparticles with three shapes, including sphere, rod and flake were used to fabricate the interlayers of TFN membranes. The effects of nanoparticle shape and loading on the morphologies and properties of the interlayers and resultant TFN membranes were systematically investigated. The results showed the morphologies and physicochemical properties of the PA layers could be regulated well by the shape and loading of CeO2 nanoparticles. The surface morphologies of the TFN membranes exhibited the transformation from nodule structure to ridge-valley structure. At the same time, the introduction of interlayer made PA layer coarser, the pore size smaller and the pore distribution more uniform. Under the same loading conditions, the rodlike CeO2 nanoparticles tended to form a homogeneous network-like interlayer due to the large specific surface area and good dispersion. The interlayer reduced the transport path of water molecules in the PA layer based on the “gutter” effect, thus improving the permeability of TFN membrane. The water permeability of the TFN membrane with rodlike CeO2 interlayer could be 124% higher than that of the control, while the rejection of salts did not significantly change. This study deepens our understanding on the role of nanoparticle in regulating the morphologies and properties of interlayer and TFN membrane, and provides an effective method to enhance separation performance of nanofiltration membrane.