Polyaniline encapsulated sulphonated graphene oxide based cation exchange membrane for electrodialytic separation of mono- and bi-valent ions

Polyaniline encapsulated sulphonated graphene oxide (SGO-PANI) was prepared by ion exchange process. The SGO-PANI was incorporated in sulphonated poly(ether ether ketone) (SPEEK) matrix to fabricate the mono-valent selective cation exchange membrane. The structural morphology of SGO-PANI was studied by FTIR, XPS, SEM and XRD spectra. Resultant SPEEK@SGO-PANI membrane exhibited excellent stabilities and physicochemical and electrochemical properties suitable for electrodialysis (ED) applications. Encapsulation of strong acid with a weak base seems to improve electrostatic repulsion between membrane surfaces and of bi-valent ions, which are responsible for significant flux reduction. Chronopotentiometric and current-voltage responses of SPEEK@SGO-PANI membrane confirmed its ion-conducting nature along with 3.32 mA cm–2 limiting current density (Ilim). Reported SPEEK@SGO-PANI membrane showed a high electrodialytic flux of Na+ compared to bi-valent ions (Mg2+, Ca2+, and Cd2+). Extremely low energy consumption and high current efficiency (81.18%) at 6.0 V applied voltage for Na+ (0.10 M) revealed the promising nature of the reported membrane. Observed mono-valent ion selectivity aroused due to improved electrostatic repulsion of bi-valent ions with the membrane surface.