Novel Silver and Bismuth Tungstate-Based Nanostructures Synthesized by a Green Route and Their Application to Dye Photodegradation

Organic dyes constitute one of the main pollutants existing in wastewater, perturbing aquatic life and causing environmental problems. Photocatalytic oxidation represents an alternative process for effective and easy degradation of dyes. In this study, the synthesis of novel silver and bismuth tungstate-based nanostructures with high photocatalytic activity for photodegrading methylene blue (MB) dye is described. The novel, as-prepared, Ag8W4O16/AgBiW2O8/Bi2WO6 photocatalyst improved MB decomposition efficiency achieving a photodegradation of 82.50% within 40 min under UV irradiation. Herein, the holes (h+) are the main oxidative species in the MB degradation process. Moreover, the photocatalytic mechanisms of MB degradation by using the AgBiW2O8/Bi2WO6 and Ag8W4O16/AgBiW2O8/Bi2WO6 heterojunctions is postulated. The synthesis is conducted by a green and combined methodology that includes the use of a metathesis reaction (double displacement reaction)/molten salt procedure. This methodology is simple, effective, high-yield (95%), and intermediate temperature, carried out in normal atmospheric conditions and using simple equipment. The particles were obtained in NaNO3 at 350 °C (2 h) showing spherical-like shapes with sizes from 10 to 59 nm according to the Ag content in samples. SBET and Dp values obtained for samples varied from 8.1 to 10.2 m2 g−1 and 17.67 to 32.15 nm, respectively. The Ag load in samples showed an important role in the phase composition of photocatalysts obtaining AgBiW2O8/Bi2WO6 and Ag8W4O16/AgBiW2O8/Bi2WO6-type heterostructures.