Synthesis of an environmental nano-polyoxometalate (α2P2W17CoO61)8− as catalyst for dyes degradation: A comparative study oxidation of indigoid and azo dyes

Abstract

A nanopolyoxometalate (nano-POM) compound consisting of saturated Dawson anions (α2P2W17CoO61)8− has been synthesized and characterized by various analytical methods, UV–vis spectroscopy, FT-IR spectroscopy, single crystal X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray analysis (EDX).The separately oxidative degradation of indigo carmine and methyl orange dyes in aqueous solution by KMnO4 using (α2P2W17CoO61)8− as catalyst was investigated. The full Decolorization was attained during the first minutes of oxidation process by this new homogeneous system (dye/KMnO4/α2P2W17O61Co). The experimental results showed that the catalyst greatly affected the discoloration efficiency; it was up to 75.4 % and 66.1 % respectively for IC and MO under these optimum conditions: an initial potassium permanganate concentration of 0.02 mM, a catalyst concentration of 0.2 mM and initial concentration dyes of 5 mg/L at pH 3 and room temperature (25 °C).The effect of other Dawson type polyoxometalates on the dyes oxidation under the same conditions was evaluated. After four consecutive reaction cycles, the catalyst (α2P2W17CoO61)8− exhibited a good recyclability and reusability without significant loss of activity. The precedents analytical methods indicated that this recovered catalyst has effectively a good stability. This nano-POM function as a recyclable efficient catalyst for the rapid removal of various anionic textile dyes from aqueous solutions.