Simulation of Thermoresponsive Draw Solute-Driven Forward Osmosis for Enhanced Pure Water Production in Seawater Desalination

In this study, we developed a novel forward osmosis (FO) simulation method for a multicomponent system (water, NaCl, and thermoresponsive ethylene oxide–propylene oxide-based copolymer draw solute) targeted for direct seawater desalination using a hollow fiber (HF) membrane module. Box complex method was applied to numerically solve the FO simulation model of a three-component system. A good agreement between experimental and simulation results obtained in various operation conditions allowed us to estimate not only the effect of NaCl and draw solution (DS) concentration on the resulting water permeate flow rate but also the osmotic pressure inside and outside of the HF membranes. From the analysis, the HF modules were designed to decrease the dilution of the draw solution (DS) inside the module due to water permeation. We validated the suggestion by simulation of the increase of the water permeation rate in the modified HF modules, which were designed for the smooth flow of the DS to decrease the DS dilution. The simulation was further verified by reasonable results indicating that the decrease of NaCl concentration in the feed water is also effective in increasing the water permeation rate in the current HF module.