Understanding the efficient seawater desalination performance of carbon honeycomb via reverse osmosis

This work investigates the performance of the carbon honeycomb (CHC) nanostructure in seawater desalination via reverse osmosis by molecular dynamics simulations. An ultrahigh water permeation rate is observed with a complete ion rejection. Increasing the pore size of CHC can further increase the permeation rate but slightly reduces the rejection rate. The transport resistance of water across the membrane is found to be dominated by the resistance at the pore entrance. The interior resistance of the membrane is low and only becomes significant when its thickness is large. With the aid of the enhanced ordering and retarded dynamics of the water molecules in the membrane, the low interior transport resistance results in the high water permeation rate. In addition, when salt ions penetrate into the CHC membrane under a higher driving pressure, the fast water permeation is not severely disturbed and the high salt rejection rate is retained because the water molecules and those of the ions are spatially segregative from each other. This work is helpful in deepening the understanding water and ion transportations in CHC and provides guidance for studying the applications of CHC in other ion-filtration pro-cesses, such as forward osmosis and capacitive deionization.