A new effective way to degrade methylene blue by introducing negative ions powder into FeO/HO system to accelerate Fe(III)/Fe(II) transformation.

Negative ions powders (NIP) have been widely applied in many fields because of their natural electric field and far infrared radiation, especially in wastewater treatment. In this study, the NIP was first introduced into FeO/HO system to degrade methylene blue (MB). The MB removal was completely achieved at 5 h via a non-photochemical pathway and the degradation rate constant of this system is about 0.565 h, which is about 16 times higher than in FeO/HO Fenton-like system (0.035 h). In addition, the results of quenching experiments indicate that the electron (e) and negative oxygen ion (•O) are the main reactive species. It was determined that FeO@NIP is the effective component that leads to the activation of HO to produce •OH, which derive from the pathway: NIP acts as an electron donor to reduce Fe(III) into Fe(II). Moreover, NIP can produce negative ions, which is also conductive to degradation. This study suggests a promising direction for the practical application of NIP based catalysis by integrating it with the Fe(III)/Fe(II) transformation process.