An electrically switched ion exchange film with molecular coupling synergistically-driven ability for recovery of Ag+ ions from wastewater

An electrically switched ion exchange film with molecular coupling synergistically-driven ability for the selective recovery of Ag+ ions is developed by coupling a conducting polypyrrole (PPy) with a 2, 2'-dithiosalicylic acid (DTSA) at molecular scale. The rapid and selective uptake/release of Ag+ ions by this hybrid film was found to be realized by the electrochemical circulation of the PPy <-> PPyn+ as well as the disulfide <-> dithiolate and the recognition ability of the carboxyl groups and disulfide bonds of DTSA. As a result, the recovery of Ag+ ions can be handily achieved by adjusting the operating potential applied on the hybrid film coated electrode. The electrochemical quartz crystal microbalance measurements combined with the cyclic voltammetric technique, X-ray photoelectron spectroscopy and density functional theory computations were performed to identify the uptake/release mechanism of the hybrid film. Furthermore, the uptake capacity of the hybrid film maintained almost invariable after 10 consecutive uptake/release cycles, and the regeneration rate of Ag+ ions remained over 80% in each cycle. It is expected that such an electroactive hybrid film can be applied for the recovery of Ag+ ions from various industrial discharges.