High selectivity and efficient microwave-assisted reflux tin oxide synthesis controlled by acidity environments and its photocatalytic degradation toward Acid Yellow 17

Abstract

A series of tin oxide materials have been successfully synthesized under low-temperature synthesis using microwave-assisted reflux method in different acid synthesis environments. The result found that the initial synthesis environment differentiates the hydrolysis pathway and further stimulates the formation of a specific tin oxide product. At pH 2, tin (IV) oxide is mostly formed where the higher pH transforms tin (IV) to the combination of tin (IV) and tin (II) and finally tin (II) oxide. The phase transformations are confirmed by the X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), and UV–Vis Diffuse Reflectance Spectroscopy (DRS) Spectrophotometer. The material performance test as the photo-catalyst confirms the activity of tin oxide prepared at pH 3 corresponding to Sn₃O₄ indicates as performs the highest photo-catalytic degradation followed by SnO₂ prepared at pH 2 and the mixture of Sn₃O₄ and SnO at pH 4, pH 5, and finally SnO at pH 6. The optimum activity of tin oxide could degrade above 90 % of acid yellow 17 (AY17) synthetic dyes under 60 min of light irradiation where further radiation could degrade the dye up to 98 %. However, the single phase of SnO did not show good photocatalytic performance due to its narrow bandgap. The pseudo-first-order kinetic models fit the observed photocatalytic degradation where tin oxide prepared at pH 3 has 0.0462 min⁻¹ of kinetic rate. From the synthesis point of view, the result found that microwave-assisted reflux cut the long period of synthesis route of tin oxide and opened the possibilities of pilot-scale synthesis of tin oxide for downstreaming tin industries controlled by an initial acid synthesis environment. In the photocatalytic performance, several materials are promising for wastewater treatment since they possess high photocatalytic performance and provide high photo-response on a visible light wavelength which potentially utilizes sunlight energy. Furthermore, the correlation between the synthesis route and its photocatalytic performance is well discussed in the present paper.