Trace Co coupled and tourmaline doped g-C3N4 for visible-light synergistic persulfate system for degradation of perfluorooctanoic acid

Removal of perfluorinated compounds (PFCs) from the environment is a major challenge due to their refractory, persistent and bioaccumulative properties. In this study, trace Co coupled via Co-P coordination and tourmaline (TM) doped g-C3N4 was fabricated (marked as Co/TM/g-C3N4) and used as the catalyst for activating peroxymonosulfate (PMS) to remove emerging PFOA under visible light irradiation. Several affecting parameters were systematically investigated, inlcuding Co/TM/g-C3N4 dosage, PMS concentration, initial pH, as well as coexisting Cl-, HCO3-, H2PO4-, NO3- and humic acid. Under the conditions of 0.5 g/L Co/TM/g-C3N4, 2.5 g/L PMS and pH 3.0, the developed synergistic system had the ability for 81.11% removal of PFOA within 4 h, 67.64% removal after the fourth run, and also could be effectively applied in actual water bodies. During the degradation process, pi-pi*, N-C=N and graphite N played the vital role, with the final defluorination rate of 31.12% at 4 h. Free radical quenching and quantitative analysis, as well as electron paramagnetic resonance was used to verify the free radical and non-free radical pathways for PFOA removal, with the findings that SO4?(center dot-) (2.61 mu M at 1 h), center dot OH (0.067 mu M at 4 h), O-2(center dot-), h(+), and O-1(2) were involved with possible time-dependent. By liquid chromatography-mass spectrometry analysis, the short-chain intermediates of C3-C7 were proposed and identified. From this study, trace Co coupled and TM doped g-C3N4 demonstrated higher catalytic potential to activate PMS for visible-light synergistic PFOA removal, with the expectation of achieving a cleaner water environment for human beings.

Automated summary

In this study, a Co/TM/g-C3N4 catalyst was developed and used to activate peroxymonosulfate (PMS) for the removal of emerging perfluorooctanoic acid (PFOA) under visible light irradiation. The results showed that the developed synergistic system had the ability to effectively remove PFOA and could be applied in actual water bodies.