Effects of Vitamin B12 on the Reductive Transformation of PFOS and F-53B by Nanoscale Zero-Valent Zinc

Perfluorooctane sulfonate (PFOS) and 6:2 chlorinated polyfluoroalkyl ether sulfonate (F-53B) are persistent per- and polyfluoroalkyl substances of concern in aquatic environments. This study compared their anaerobic reductive transformation by nanoscale zero-valent zinc (nZn0), with and without vitamin B12 (VB12). Solutions containing 1 mg/L PFOS or F-53B were treated with nZn0 (278 mg/L) and, where indicated, 0.05 mmol/L VB12 (67.8 mg/L) at pH 8.5 and 30 °C for 20 days. After correction for losses observed in reagent-free blanks, PFOS loss was negligible with nZn0 alone but reached approximately 34% with nZn0 + VB12, and the corresponding defluorination rate was 33.9%. In contrast, F-53B showed approximately 85% blank-corrected loss by day 6 with either nZn0 alone or nZn0 + VB12, while defluorination rates reached 38.0% and 30.7%, respectively, indicating no enhancing benefit of VB12 for F-53B under the studied conditions. Nominal-mass LC-MS/MS features consistent with partially defluorinated and hydrogen-substituted products were observed, and tentative transformation pathways were proposed. These results demonstrated compound-specific effects of VB12 and emphasized the distinction among loss, transformation and defluorination when evaluating PFAS destruction.