Degradation of Methylene Blue with Layered Ni-Fe/WO3 Nanostructured, Composite Films Electrodeposited Onto Graphite

Abstract

Dyes from textile companies, such as methylene blue (MB), stain water bodies and result in harmful environmental effects. They can also change the color of water bodies, which inhibits aquatic photosynthesis and lowers oxygen levels, compromising aquatic health. In order to treat dye contamination in water, several methodologies exist, including electrochemical oxidation with boron-doped diamond, TiRuO2 1 and Ti/Pt2 anodes. In the search for a lower cost anode material and thus a more cost-effective electrochemical oxidation process, a composite photoelectrocatalyst composed of tungsten trioxide, nickel-iron, and graphite was fabricated. Both decolorization and degradation of MB were examined in a chloride mediated electrolyte.Ni-Fe clusters were electrochemically deposited onto a graphite surface using recurrent galvanic pulses. WO3 was then electrochemically deposited through the generation of base method, potentiostatically. Cyclic voltammetry (CV) using an electrolyte containing 10 mM MB in 10 mM phosphate buffer saline and 100 mM potassium chloride at room temperature on screen-printed electrodes identified the region where the Ni-Fe/WO3 graphite composite catalyst resulted in a large anodic current, which included the oxidation of water, chlorine and organic. Electrolysis by chronoamperometry was implemented with and without light, in a single compartment electrochemical cell. The color change was measured using absorbance spectrophotometry. In order to confirm oxidation of total organic, COD measurements provided insight on whether the observed color change was caused by decomposition of MB at the working electrode or conversion to leucomethylene blue, at the counter electrode. Since Ni-Fe can oxidize under electrolysis conditions for MB degradation, the survivability of Ni-Fe underneath WO3 was inspected. Both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) verified the presence of discrete Ni-Fe islands surrounded by WO3; after 16 hrs of electrolysis at 1.9 V vs Ag changes in the composition as well as the WO3 morphology was observed.Overall, with an increase in the electrolysis time there was a clear change in the electrolyte color. After 2 hours, the coloration of the MB solution dropped by 78% and after 16 hours, 89%. COD analysis confirmed the degradation of methylene blue by the Ni-Fe/WO3 graphite catalyst, and it was enhanced by 100 W/m2 UV light, with less conversion of methylene blue to leucomethylene blue, and an overall more efficient degradation. Acknowledgments: The authors thank The Center for Advanced Materials Processing at Clarkson University for use of their equipment and guidance provided by Hubert Bilan. This work was funded in part by NSF #20-508484 REU Site: Aquatic Sciences, Engineering, and Technology (ASET). Panizza, A. Barbucci, R. Ricotti, G. Cerisola, Separation and Purification Technology, 54 (2007) 382–387.Rodrigues de Oliveira, N. S. Fernandes, J. Vieira de Melo, D. Ribeiro da Silva, C. Urgeghe, C. A. Martínez-Huitle, Chemical Engineering Journal, 168 (2011) 208–214.