Permselectivity of Cation Exchange Membranes Modified by Polyaniline

Abstract

This work discusses the applicability of polyaniline-modified cation exchange membranes for the separation of monovalent/divalent cations by electrodialysis. A novel method of membrane modification directly in the electrodialysis unit is used to prepare permselective membranes. Complex characterization of the membranes before and after modification allows revealing the influence of membrane matrix on the modification efficiency. The characterization of the membranes includes determination of the diffusion permeability, specific conductivity and current–voltage curves in HCl, NaCl and CaCl2 solutions, as well as transport-structural parameters of the extended three-wire model. The characterization results are used to predict the influence of the modification on membrane permselectivity. The competitive mass transfer of singly and doubly charged cations in the electrodialysis process is investigated in underlimiting and overlimiting currents. Electrodialysis desalination of a solution containing Na+/Ca2+ or H+/Ca2+ cations shows that the modification leads to an increase in membrane permselectivity to single-charged cations due to the repulsion of Ca2+ ions from the positively charged membrane surface. The permselectivity of the polyaniline-modified perfluorinated membrane to H+ in the mixture of H+/Ca2+ cations is observed in all current regimes.

Influence of PtCu/C Catalysts Composition on Electrochemical Characteristics of Polymer Electrolyte Fuel Cell and Properties of Proton Exchange Membrane

“…The presented dependence had two linear regions and could be used to estimate the Cu 2+ content inside the membrane. It is well known that the cation exchange membranes possess high selectivity toward multi-charged ions in comparison with singly charged ones [35,36]. The joint analysis of Figures 7 and 8 shows that the saturation degree of the membrane by Cu 2+ -ions after the operation of MEA with PtCux/C catalysts did not exceed 40%.…”

“…The presented dependence had two linear regions and could be used to estimate the Cu 2+ content inside the membrane. It is well known that the cation exchange membranes possess high selectivity toward multi-charged ions in comparison with singly charged ones [35,36].…”

Use of the Microheterogeneous Model to Assess the Applicability of Ion-Exchange Membranes in the Process of Generating Electricity from a Concentration Gradient

“…In ion-exchange membranes, the gel and the electrically neutral solution phases are randomly located in space, and the fraction of the electroneutral solution is 0.1-0.2 (for heterogeneous membranes) [20,25]. For homogeneous membranes, the fraction of electroneutral solution is usually less than 0.1 [24,25,29]. As was shown in [30], there are none through macropores, even in heterogeneous membranes.…”

Cation Exchange Membranes Coated with Polyethyleneimine and Crown Ether to Improve Monovalent Cation Electrodialytic Selectivity

“…According to numerous reported studies, surface modification is considered as a facile and efficient approach to prepare monovalent cation permselective membranes (MCPMs). A series of cationic polyelectrolytes are usually utilized as functional modified materials, such as polypyrrole [ 15 , 16 ], polyaniline [ 17 , 18 ], polyethyleneimine (PEI) [ 19 , 20 ], polyquaternium-7 [ 21 ], chitosan, and its derivatives [ 22 , 23 ], which are decorated on the membrane surface through physical or chemical interaction.…”