Modelling the amphoteric behaviour of polyamide nanofiltration membranes

The role of the electrostatic potential existing at the adsorption surface close to the feed/membrane interface is relevant in determining the pH dependence of adsorption charge on hydrophobic groups. At high pH values, chloride adsorption is dominant with respect to sodium adsorption, whereas, at low pH's, sodium competitive adsorption remarkably affects the amphoteric behaviour.