Rapid and efficient mechanosynthesis of alkali and alkaline earth molybdates

Abstract

Complex molybdates are traditionally prepared via solid-state synthesis and aqueous chemistry methods, which generally require long reaction times and large solvent volumes or high sintering temperatures. However, these techniques often result in undesired secondary species, incomplete reactions, and relatively low yields. Mechanochemistry has proven effective for the synthesis of complex molybdates. This work expands on the development of the mechanochemical synthesis of various heptamolybdates (i.e., sodium, rubidium, and cesium), and trimolybdates (i.e., sodium, rubidium, cesium, strontium, and barium). The obtained materials were characterized via powder X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis, and scanning electron microscopy to assess the purity, morphology, and quality of the sample. High purity samples of the various trimolybdates and heptamolybdates were obtained in less than three hours of reaction time, with minimal energy input and by-products. Mechanochemistry provides a fast, more sustainable, and simple procedure for the synthesis of a wide variety of both trimolybdates and heptamolybdates including the monohydrate form of sodium trimolybdate instead of the trihydrate variant commonly obtained from aqueous reactions.