Modelling the amphoteric behaviour of polyamide nanofiltration membranes Original Research Article

The “adsorption-amphoteric” model is studied with the aim of predicting the amphoteric behaviour of polyamide Desal DK membranes, in the simple case of NaCl-water solutions. The membrane is schematized through a site-representation as the sum of hydrophobic as well as of hydrophilic groups which can support charges derived from various chemical-physical mechanisms. The pseudo-chemical reactions approach is applied to describe separately acid/base ionization, ions adsorption and counter-ions site-binding. In the case in which site-binding is negligible with respect to competitive adsorption on hydrophobic sites, the model contains five adjustable parameters which are calculated through a fitting procedure.