Naphthalene degradation dominated by homogeneous reaction in Fenton-like process catalyzed by pyrite: Mechanism and application

Fe-containing natural minerals, such as pyrite, have been conducted an extensive study in Fenton-like processes, however, answers for the role of homogeneous and heterogeneous reactions and their application potentials need to be theoretically demonstrated. In this study, the performance and mechanism of Fenton-like process catalyzed by pyrite were investigated by surface characterizations and degradation experiments using naphthalene as a target contaminant. First, the major role of homogeneous reaction in the naphthalene degradation in H2O2/ pyrite system was confirmed by iron determination and iron quenching tests, where 2,2 '-bipyridine was used as the iron quencher. Second, it was clarified that sulfur species including polysulfides, elemental sulfur, and thiosulfate facilitated the Iron redox cycle and the yield of reactive oxygen species, thus enhanced the degradation of naphthalene. Moreover, compared with sulfidated nanoscale zero valent iron and ferrous sulfide, pyrite exhibited superiority in naphthalene degradation due to higher reaction stoichiometry efficiency (0.31) and lower running cost (77 RMB (kg naphthalene)(-1)). Finally, pyrite showed excellent performance for various pollutants removal and in multiple water environments. This work provides the underlying mechanisms of H2O2/ pyrite process and a solid step forward to pyrite application in the remediation of naphthalene contaminated water.