Abstract
The oxidation of Rhodamine B (Rh B), a hazardous dye, was investigated under sunlight over the Keggin type heteropolysalt Ag3PMo12O40. The compound prepared by precipitation from the heteropolyacid H3PMo12O40 and silver salicylate, was characterized by single-X-ray diffraction, SEM analysis, Infrared and 31P NMR spectroscopy and diffuse reflectance. The optical properties indicated two allowed transitions, direct (1.79 eV) and indirect (1.12 eV). The Mott–Schottky characteristic plotted in Na2SO4 electrolyte (0.5 M) showed n-type behavior with a flat band potential of 0.25 VSCE. The electrochemical impedance spectroscopy showed the predominance of the bulk material with an intrinsic impedance (Rb = 247 Ω cm2). Rh B was successfully oxidized by O2· radical with an enhanced activity assigned to the conduction band (0.05 VSCE/4.80 eV) deriving from Mo: 5s orbital, more cathodic than the O2·/O2 couple. The degradation kinetic followed a first order model with a half-life of 70 min under an average solar flux of 930 mW cm−2.
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