Periodate activation by plasma coupled with Fe N C for contaminant removal: Machine learning assisted catalyst optimization and electron shuttle mechanism

Emerging contaminants (ECs) pose great challenges to water treatment technology due to their complexity and high harm. In this paper, the method of dielectric barrier discharge (DBD) plasma coupled with iron-based catalyst (FeNC) activating periodate (PI) was first designed for ECs removal. The ingenious introduction of FeNC not only promotes the Fenton-like reaction of DBD system but also reduces the PI activation energy barrier and accelerates the electron shuttle between PI and pollutants. Based on the parameters evaluation of machine learning (ML), the calcination temperature of 575 ℃ and 17 % N addition were determined for best catalytic performance. XRD, Raman spectroscopy, XPS and density functional theory (DFT) analysis show that optimized catalyst has better electron shuttle characteristics and PI activation ability. Compared to DBD (78 %) and DBD/PI (94 %), DBD/FeNC/PI could achieve 100 % degradation efficiency of sulfadiazine (SDZ) in 12 min with high reaction rate. In addition to the effects of ROSs (¹O₂, OH and O₂^-), the efficient electron transfer mediated by FeNC and PI is the key to promoting the degradation of pollutants. The progressive dissociation of pyrimidine ring under the action of OH and electron transfer is the main pathway of SDZ degradation. The toxicity of intermediate products produced by the system is generally lower than that of SDZ. The system still has a high SDZ removal efficiency in actual water and has a good removal effect for other types of ECs, which also makes the system have a better practical prospect.