Simulation of GO-PAMAM-Modified Polysulfone Substrate-Based Thin-Film Composite Reverse-Osmosis Membranes for Desalination.

Freshwater scarcity driven by population growth and industrial demand has increased reliance on desalination, where reverse osmosis (RO) is widely applied due to its high separation efficiency. Membrane performance is governed by the balance between water permeability and solute rejection, and attempts to improve this relationship have focused on incorporating nanomaterials to modify membrane structure and transport behavior. In this study, a computational investigation was carried out for thin-film composite (TFC) membranes incorporating graphene oxide-poly(amidoamine) (GO-PAMAM) within the polysulfone substrate to examine its influence on transport under RO conditions. A two-dimensional model was implemented in COMSOL Multiphysics by coupling the Laminar Flow and Transport of Diluted Species interfaces, while permeation across the membrane was described using a solution-diffusion framework parameterized by experimentally determined salt permeability coefficient. Variation in GO-PAMAM loading (0-0.10 wt%) was introduced through intrinsic permeability parameters, enabling direct comparison with experimental data. The simulations reproduced the observed trends, with the membrane containing 0.06 wt% GO-PAMAM showing higher salt rejection, increasing from 78.16% to 90.08% relative to the pristine membrane. The model predicted lower permeate-side solute concentration and a decrease in salt rejection along the membrane length. Model predictions agreed with experiments, with mean relative errors of 1.23% for salt rejection and 7.41% for water flux, demonstrating the ability of the model to capture transport behavior in GO-PAMAM-modified TFC membranes.