Hafnia ceramic nanofiltration membranes: Part II. Modeling of pressure-driven transport of neutral solutes and ions

We use the hindered transport theory for neutral solutes and the macroscopic homogeneous electro-transport theory for ions to predict without any adjustable parameters the limiting rejection of, respectively, four neutral molecules and five binary electrolytes by granular porous hafnia nanofilters. Membrane parameters entering into the theory, namely the membrane effective pore size and effective charge density, are estimated from independent measurements performed on the membrane material. The theory is in reasonably good overall agreement with the rejection measurements performed on hafnia nanofilters using uncharged sucrose and PEG (400, 600, 1000) molecules and 10−3 M electrolytes (NaCl, NaNO3, CaSO4, CaCl2, and Na2SO4) at acidic, neutral, and basic pH values (3, 6, and 9).