Study on the removal of methylene blue by submerged Arc generated by titanium and iron electrodes

Abstract

Methylene blue (MB) solution was treated by the submerged arcs generated by the titanium (Ti) and iron (Fe) electrodes, with a subsequent aging process. The removal ratio of each condition was recorded by the absorbance of the treated solution. The experimental results indicated that the submerged arc with Fe electrodes is more efficient with an efficiency nearly 90% after 3.5 min of treatment. Reversible decolorization was observed in the MB solution treated by the Fe submerged arc. However, the removal ratio in the MB solution treated by the Ti submerged arc continuously increased during both the treating and aging process. Furthermore, the particles eroded from the Ti electrodes were characterized by SEM and XRD, and the titanic oxides including TiO, TiO2 and Ti3O5 were found with different diameters ranging from 1 μm to 20 μm. Moreover, complete decomposition occurred during the treatment by the submerged arc generated by the Ti electrodes. The eroded particles from the Fe electrodes were examined by XRD, and the majority of the composition was iron. Unlike the Ti electrodes, the decolorization process by the submerged arc of Fe electrodes was more likely related to the formation of colorless leuco-MB and the physical adsorption by iron hydroxides. Additionally, the pH and chemical oxygen demand (COD) of the treated solutions were also discussed.