Electrically Controlled Anion Exchange Based on a Polypyrrole/Carbon Cloth Composite for the Removal of Perfluorooctanoic Acid

A simple and effective process for perfluorooctanoic acid (PFOA) removal using electrically switched ion exchange was developed by depositing polypyrrole (PPy) on the conductive material. As a conducting polymer, PPy can switch between the oxidized state (with positive surface charges) and the reduced state (without surface charges), which results in anion exchange upon application of an oxidation or reduction potential, making it a suitable adsorbent for PFOA, a challenging anionic organic contaminant in the natural aqueous environment. Adsorption mechanisms and the regeneration ability of the PPy were explored through adsorption and desorption tests in an electrochemical quartz crystal microbalance with dissipation monitoring (EQCMD) system and via batch experiments. In the batch experiments, carbon cloths coated with PPy were used as adsorbents, showing excellent selectivity of PFOA over common inorganic anionic species, such as Cl-, NO3-, and SO42-. More than 90% of adsorbed PFOA can be quickly released within 30 min via the electrically controlled desorption method. The results of X-ray photoelectron spectroscopy analysis provide direct evidence for the anion-exchange process, which happens between Cl- and PFOA during the redox switching of PPy. The results of this study show the possibility of a novel process for the removal of PFOA from contaminated water.

Automated summary

A novel process for PFOA removal from contaminated water was developed using electrically switched ion exchange with PPy deposited on conductive materials. The PPy showed excellent selectivity and regeneration ability in batch experiments, providing a promising method for addressing PFOA contamination in natural aqueous environments.