Novel g-C3N4/diatomite composite catalysts loaded with cobalt and iron for efficient peroxomonosulfate activation in N-Methylpyrrolidone degradation

Background N-Methylpyrrolidone (NMP) is a prevalent organic pollutant in the wastewater generated during the lithium-battery manufacturing process. Given the ecological risks associated with its release into the environment, an efficient and environmentally friendly degradation technology is currently required to meet the demand for the degradation of NMP in water. Methods The g-C 3 N 4 /diatomite/CoFe 2 O 4 (CNDE-CF) composite catalysts prepared in this study employed a combination of impregnation-calcination and solvent-heat treatment processes. Efficient degradation of NMP was achieved using the obtained catalyst-activated persulfate (PMS), which was characterised in terms of morphology and physicochemical properties. In addition, the effects of the factors on the degradation efficacy of the CNDE-CF/PMS system were investigated by varying the catalyst dosage, initial pH, initial NMP concentration, NMP/PMS concentration ratio, and anion content in solution, respectively, under controlled variables. Significant findings Based on the results of these experiments, it was found that the degradation of NMP by the CNDE-CF/PMS system reached 99 % degradation within 60 min ( k obs = 0.0715 min -1 ). Quenching experiments and in situ electron paramagnetic resonance (EPR) spectroscopy techniques revealed the involvement of four reactive oxygen species in the degradation mechanism, with sulphate radicals (SO 4 ·- ) and singlet oxygen ( 1 O 2 ) playing a larger role. In addition, the abundant pores of diatomite, the electrons provided by graphitic phase carbon nitride and the redox cycling reaction between Co 2+ /Co 3+ and Fe 2+ /Fe 3+ are the mechanisms by which this efficient degradation reaction occurs. Finally, experiments demonstrating the stability and wide applicability of the material were carried out to provide an experimental basis for the possibilities of this material in future practical applications.