Impacts of hydrophobic, hydrophilic, superhydrophobic and superhydrophilic nanofibrous substrates on the thin film composite forward osmosis membranes

Few works focused on the effects of different wetting properties of micro-porous nanofibrous substrates on the separation performance of thin film composite (TFC) membranes. This study developed hydrophobic, hydrophilic, superhydrophobic and superhydrophilic nanofibrous substrates to conduct the same interfacial polymerization (IP). It reveals profound impacts of substrate wetting properties on the morphologies and chemical compositions of PA films, and eventually separation performance in reverse osmosis (RO) and forward osmosis (FO) operations. It is demonstrated that the hydrophobic and superhydrophobic substrates leaded to PA films with less cross-linking degrees and more leaf-liked structures, which enhanced RO water permeability. Meanwhile, the PA film developed on the hydrophilic substrate displayed a higher cross-linking degree, a higher thickness and a more nodular structure, which reduced the water permeability but enhanced salt rejection during the RO operation. However, the obvious defects could be found in the PA film developed on the superhydrophilic substrate due to the excessive hydrogen forces. In addition, the TFC membrane developed on hydrophilic substrate exhibited the highest water permeability during the FO process due to the alleviated internal concentration polarization (ICP) effects. This work could fill the investigation gap about the effects of nanofibrous substrate wettability on TFC membrane.