Evidence of ammonium ion-exchange properties of natural bentonite and application to ammonium detection

• An ammonium-sensitive sensor based on polymeric membranes has been developed.
• The sensing membrane was covered with a clay mineral montmorillonite (bentonite).
• Electrochemical impedance spectroscopy was used to characterize the device.
• The Au/PVC–DNP–bentonite sensor shows a high sensitivity to ammonium detection.

Ammonium exchange with hybrid PVC–bentonite (mineral montmorillonite clay) thin film was revealed using FTIR spectroscopy, EDX, cyclic voltammetry and electrochemical impedance spectroscopy. The effect of ammonium exchange on the charge transfer resistance of PVC–bentonite hybrid thin film was attributed to a modification of the intersheet distance and hydration of bentonite crystals.The obtained impedimetric ammonium sensor shows a linear range of detection from 10− 4 M to 1 M and a detection limit around 10− 6 M.