The enhancing effect of weak magnetic field on degradation of Orange II by zero-valent iron

The effects of weak magnetic field (WMF) on degrading Orange II by zero-valent iron (ZVI) as functions of pH_ini, ZVI dosages, and Orange II concentrations were investigated. The pseudo-first-order rate constants of Orange II removal by ZVI decreased progressively from 0.0057 to 0.0006 min⁻¹ without WMF and from 0.0419 to 0.0039 min⁻¹ with WMF, respectively, as pH_ini increased from 3.3 to 5.5. The pseudo-first-order rate constants of Orange II sequestration by ZVI were increased by 2.6- to 21-folds due to the application of WMF under the reaction conditions investigated in this study. The WMF-induced improvement in Orange II removal by ZVI was attributed to the accelerated corrosion of ZVI in the presence of WMF. The application of WMF not only improved the decolorization efficiency, but also enhanced TOC removal dramatically. The influence of radical scavenger and oxygen on Orange II removal as well as the FTIR analysis revealed that Orange II was removed via reduction by ZVI as well as adsorption/co-precipitation by the corrosion products. The method of employing WMF to enhance contaminants removal by ZVI is considered to be a promising technique in future water treatment since it does not need extra energy and costly reagents.