Determination of chemical stability of zinc stannate (Zn2SnO4) powders

In this study, the effects of material properties (particle surface area, particle size and morphology) and pH on the chemical stability of zinc stannate (Zn2SnO4) in aqueous media were investigated. Zn2SnO4 powders with different surface area and particle size were synthesized by high temperature solid state reaction and hydrothermal method. Subsequently, Zn2SnO4 suspensions were prepared by adding HCl acid, NH4OH base and 10% NaCl solutions in deionized water at pH 3, 7 and 9 in aqueous media. The supernatant from the suspensions were collected for 30 days at 24-hour intervals and concentrations of Zn2+ and Sn4+ ions were determined by ICP-OES analysis. According to ICP-OES results, the cations of Zn2SnO4 were more affected than the acidic medium, although it has neutral pH and very low solubility in basic media. In addition, the surface area of the Zn2SnO4 powder synthesized by the hydrothermal method (18,053 m2/g) was higher than the Zn2SnO4 powder (1.99 m2/g) synthesized by the solid state, which results in a higher dissolution rate at pH 3. The presence of Zn2SnO4 particles in the aqueous medium was investigated by means of TEM analysis and it was determined that no interaction layer was formed around the particles which were kept in water. These results clearly show that the structure of Zn2SnO4 particles has not changed in the acidic environment for 30 days under the current test conditions.