Experimental and CFD investigation of phase inversion kinetics and morphology development in polysulfone membranes modified with amphiphilic polymeric deep eutectic solvent

The current study investigates the influence of a polymeric deep eutectic solvent (DES) with amphiphilic characteristics on the structural properties of polysulfone membranes, focusing on the kinetics of the phase inversion process. Both experimental investigation and modeling were conducted to better understand the role of this additive during membrane formation. The experimental findings indicate that even a minimal addition of DES significantly enhances both the porosity and flux of the membrane. Specifically, at an optimal concentration of 0.5 wt.%, the porosity reached 71.5%, accompanied by an increase in finger-like pore structures, and the pure water flux increased to 94.3 L/m2.h. However, exceeding this optimal concentration led to a reduction in porosity due to the suppression of macro pore formation. Additionally, a simplified unsteady computational fluid dynamics (CFD) model was developed to simulate the phase inversion process, using experimental kinetic data. The simulation was developed based on Fick's diffusion law for components that permeate in the non-solvent bath. The model can be used to better understand the mass transfer behavior during membrane formation and to predict its influence on the final membrane morphology. The model's predictions regarding the relative concentration of organic substances in the coagulation bath were compared with experimental results. The simulation results demonstrated a strong correlation with the experimental data, allowing for preliminary predictions about the final membrane structure.