Removal of perfluorinated carboxylates from washing wastewater of perfluorooctanesulfonyl fluoride using activated carbons and resins.

Perfluorooctanesulfonyl fluoride (PFOSF) washing wastewater contains high concentrations of perfluorinated carboxylates (PFCAs) including perfluorohexanoate (PFHxA, 0.10 mmol/L), perfluoroheptanoate (PFHpA, 0.11 mmol/L), and perfluorooctanoate (PFOA, 0.29 mmol/L). For the first time, we investigated the removal of these PFCAs from actual wastewater using the bamboo-derived activated carbon (BAC) and resin IRA67. Adsorption kinetics, effects of adsorbent dose, solution pH, and inorganic ions, as well as regeneration and reuse experiments were studied. The removal percents of three PFCAs by BAC and IRA67 followed the increasing order of PFHxA < PFHpA < PFOA, but the adsorption equilibrium time conformed to the reverse trend. PFCAs removal on IRA67 decreased with increasing pH, but BAC almost kept stable PFCAs removal at pH above 5.0. Among competitive adsorption of three PFCAs, PFOA was preferentially adsorbed on both BAC and IRA67. PFCAs removal from actual wastewater by BAC was higher than that in simulated solution, due to the presence of high concentration of inorganic ions in the wastewater. However, the co-existing organic compounds in wastewater significantly suppressed the adsorption of PFCAs. Both spent BAC and IRA67 were successfully regenerated by ethanol solution or NaCl/methanol mixture, and IRA67 showed the stable removal of PFCAs in five adsorption cycles.