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 (E-QCMD) 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 SO4
2–. 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.