Atomistic Insights into the Salt Rejection and Water Permeability in Functionalized Carbon Honeycomb Membranes

To overcome the challenges faced by conventional polyamide membranes in fresh water production technology, we use classical molecular dynamics simulations to study the effects of functionalization with –CONH ₂, –OH, and –NH ₂ groups on the water desalination performance of carbon honeycomb reverse osmosis membranes. The salt rejection rate and water permeability are determined for different distributions and densities of the functional groups. Our results show that the salt rejection rate can be enhanced to 100% by functionalization with –CONH ₂ groups at a water permeability that is at least three orders of magnitude higher than in the case of conventional polyamide membranes. We evaluate the free energy profiles and mass density distributions of the Na ⁺ and Cl ⁻ ions across the membranes as well as mass density maps of the water molecules inside and outside the membranes to understand how the functionalization affects the salt rejection rate and water permeability.