Mechanochemical destruction of a chlorinated polyfluorinated ether sulfonate (F-53B, a PFOS alternative) assisted by sodium persulfate

A chlorinated polyfluorinated ether sulfonate (F-53B, C8ClF16O4SK) has been widely used as a mist suppressant by the chrome plating industry in China for more than 30 years. It was reported to be moderately toxic and as resistant to degradation as perfluorooctane sulfonate (PFOS). Considering the need for safe disposal of wastes containing F-53B, fast and effective methods are urgently required, of which the mechanochemical destruction (MCD) method seems to be a good alternative. In the present study, sodium persulfate (PS) was tested as a novel co-milling reagent in the MCD process for the degradation of F-53B. F-53B, PS and sodium hydroxide (NaOH) were co-ground in a planetary ball mill, and the ground samples were analyzed by liquid chromatography-mass spectrometry (LC-MS), ion chromatography (IC) and a total organic carbon (TOC) analyzer. Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and X-ray photoelectron spectrometry (XPS) analyses were conducted as assistant measures. The results revealed that after 8 h of milling with 60 g balls at the best mass ratio (PS : NaOH : F-53B = 4.17 : 1.75 : 0.05), 88% of F-53B was destroyed, the fluoride recovery efficiency was 54%, and the destruction efficiency closely related to the milling time. TOC analysis showed considerable mineralization of F-53B. Overall, MCD was suggested to be a promising method in the degradation of recalcitrant chemicals like F-53B.