Enhancement of heavy metals removal efficiency from liquid wastes by using potential-triggered proton self-exchange effects

• A mechanism of potential-triggered proton self-exchange effect was proposed.
• An electroactive film was fabricated using a facile and controllable method.
• The electroactive film showed a high selectivity to Cu2+ ion removal.
• The electroactive film exhibited an excellent cycling stability.

A concept of electrochemically switched ion exchange (ESIX) film with potential-triggered proton self-exchange effect (PTPS) for removal of Cu2+ ions was proposed. Based on this concept, a novel ESIX film made of poly (2,6- pyridinedicarboxylic acid) (PPDA) was successfully fabricated, and applied to remove Cu2+ ions from aqueous solution. It is found that Cu2+ ions were rapidly removed with a high selectivity and this film was reproducible by simple changing the applied potential. Herein, the mechanism of the potential-triggered proton self-exchange (PTPS) effect on the ion-exchange process using this kind of film was proposed. Electrochemical quartz crystal microbalance, IR spectroscopy and X-ray photoelectron spectra methods were used to characterize and attest the proposed mechanism. This PPDA film showed high potential for the Cu2+ detection and the treatment of wastewater containing heavy metal ions in various industrial processes.