Sublayer assisted by hydrophilic and hydrophobic ZnO nanoparticles toward engineered osmosis process

Hydrophilic and hydrophobic polyethersulfone (PES)-zinc oxide (ZnO) sublayers were prepared by loading of ZnO nanoparticles into PES matrix. Both porosity and hydrophilicity of the hydrophilic sublayer were increased upon addition of hydrophilic ZnO, while these were decreased for the hydrophobic sublayer. In addition, the results demonstrated that the hydrophilic membrane exhibited smaller structural parameter (S value or S parameter or S), which is beneficial for improving pure water permeability and decreasing mass transfer resistance. In contrast, a higher S parameter was obtained for the hydrophobic membrane. With a 2M NaCl as DS and DI water as FS, the pure water flux of hydrophilic TFN0.5 membrane was increased from 21.02 L/m² h to 30.06 L/m² h and decreased for hydrophobic TFN0.5 membrane to 14.98 L/m² h, while the salt flux of hydrophilic membrane increased from 10.12 g/m² h to 17.31 g/m² h and decreased for hydrophobic TFN0.5 membrane to 3.12 g/m² h. The increment in pure water permeability can be ascribed to reduction in S parameter, which resulted in reduced internal concentration polarization (ICP). The current study provides a feasible and low cost procedure to decrease the ICP in FO processes.