Effect of competition between swelling and dye adsorption on the performance and selectivity of graphene oxide membranes

-spacing from 12.1 ± 0.1 Å to 11.7 ± 0.1 Å, followed by further shrinkage to 11.4 ± 0.1 Å due to the electrostatic compression of the negatively charged GO with the positively charged dye molecules. Combined with physical blockage by dye molecules, this led to a rapid decline in membrane permeance described well by Poiseuille-based permeance trends. These results show that adsorption, particularly at low penetrant concentrations, can affect measured rejection rates and that adsorption can substantially alter the membrane permeance. Considering the roles of adsorption and electrostatic interactions, charged dyes are unsuitable for permeation tests intended to assess the intrinsic size-exclusion properties of two-dimensional lamellar membranes.