Effect of the chloride ion on advanced oxidation processes catalyzed by Fe-based metallic glass for wastewater treatment

Fe-based metallic glasses (Fe–MGs) are potential candidate catalysts for advanced oxidation processes (AOPs) for recalcitrant organic pollutant degradation. However, industrial wastewater and natural contaminated sites usually contain abundant inorganic ions, like the chloride ion (Cl−), which significantly affect AOPs, but their influence on MG-activated AOPs still remains unclear. Through the study of three commonly used oxidants, hydrogen peroxide (H2O2), peroxydisulfate (PDS), and peroxymonosulfate (PMS), the effect of Cl− on the FeSiB-catalyzed process of degradation of the typical azo dye Orange II was investigated. Evidence indicates that the addition of Cl− resulted in the monotonous inhibition of the degradation process when the H2O2/FeSiB and PDS/FeSiB systems were employed, but promoted effect was detected with the PMS/FeSiB system, which is different from the previously observed dual effect of Cl−. It is closely relative with FeSiB induced unique variety of degradation pathways, including radicals, non-radicals (1O2), and direct reduction degradation. Moreover, the presence of Cl− significantly affected the systems’ absorbable organic halogen content and the amount of Fe leached into the solution. The results of this work will provide essential references for Fe-based MG used as AOP catalysts in field applications and the development of advanced MGs with excellent adaptability to complex environments.