Pilot-scale removal of PFAS from chromium-plating wastewater by anion exchange resin and activated carbon: Adsorption difference between PFOS and 6:2 fluorotelomer sulfonate

Chromium-plating wastewater is an important source of per- and polyfluoroalkyl substances (PFAS) contamination. Currently, adsorption is considered to be one of the main technologies for the removal of PFAS from wastewater. However, no pilot-scale studies have been conducted to investigate its application in chromium-plating wastewater and the adsorption characteristics of 6:2 fluorotelomer sulfonate (6:2 FTS), the alternative to perfluorooctane sulfonate (PFOS). In this study, we evaluated the removal of PFAS from chromium-plating wastewater by granular activated carbon (GAC) and anion exchange resin (AER) at a pilot-scale. The breakthrough curves of PFOS and 6:2 FTS were similar in GAC columns, but significantly different in AER columns, with PFOS and 6:2 FTS reaching 10% breakthrough at about 45,000 BV and 4,000 BV, respectively. The replacement of 6:2 FTS by PFOS and other coexisting organic substances resulted in the concentrations of 6:2 FTS in the AER effluent reaching up to 3.8 times the influent concentrations. Density functional theory (DFT) calculations showed that the adsorption energy of PFOS on the quaternary amine group of AER was more negative than that of 6:2 FTS, and the weak affinity of AER for 6:2 FTS was closely related to the solvent effect. According to the cost analysis, if 6:2 FTS becomes the target PFAS, AER adsorption will no longer have a cost advantage over GAC adsorption. This study can provide technical support for the adsorptive removal of PFAS from electroplating wastewater and guide the development of efficient adsorbents for PFAS alternatives.