Experimental study on hydrochloride acid permeation across layer-by-layer self-assembled polyelectrolyte membranes

The polyelectrolyte multilayer PAH/PSS, PVA/PVS, PDADMAC/PSS membranes were prepared by alternating layer-by-layer deposition of cationic and anionic polyelectrolyte on the porous PAN/PET supporting membranes, and the transport behavior of hydrochloride acid across the prepared membranes was investigated under the different concentration gradients. It is found that the permeation flux (J) of hydrochloride acid increases with the increase of the feed concentration of hydrochloride acid, and depends on the number of dipping cycles (n) and the charge density (φ_c) of polyelectrolyte membrane material, which could be expressed respectively as follows: J=5.221+11.755 e^-n/15.279 and J=1.624+102.851 e^-φc/0.028 (where J is in the unit of 10^-10 mol·cm^-2·s^-1). Experiments show that the permeation flux of membrane decreases with the increase of the membrane thickness and the charge density of the polyelectrolyte material, which indicates that by controlling the number of dipping cycles in membrane preparation or using various polyelectrolyte materials with different charge density to prepare the membrane, the permeation rate of the membranes can be controlled. The polyelectrolyte multilayer membranes may be useful for separation of acids and control of acidity in some reaction systems.