Determination of conversion reaction mechanism of celestite to acidic strontium oxalate hydrate in aqueous solution of H 2 C 2 O 4

Abstract One of the most important steps to obtain high-temperature superconductive and self-activated luminescence strontium compounds is the production of strontium oxalate as precursor. The aim of this study is to determine the conversion reaction mechanism of celestite to acidic strontium oxalate hydrate in solutions obtained by dissolving H 2 C 2 O 4 in distilled water. The effect of temperature on the conversion reaction mechanism using excess amounts of H 2 C 2 O 4 with respect to the conversion reaction stoichiometry was determined. The conversion of celestite to acidic strontium oxalate in H 2 C 2 O 4 solutions proceeds in two consecutive reaction steps. In the first step, SrC 2 O 4 ·H 2 O is formed and in the second, H[Sr(C 2 O 4 ) 1.5 (H 2 O)] is formed. The conversion reaction ends by the formation of SrC 2 O 4 ·H 2 O on the surfaces of the celestite particles. The saturation concentration of H[Sr(C 2 O 4 ) 1.5 (H 2 O)] chelate compound decreases during cooling of the solution and the excess amount of Sr(HC 2 O 4 )(C 2 O 4 ) 0.5 ·H 2 O crystallizes. XRD, ICP - OES and simultaneous TG/DTA – MS analytical techniques were used to explain the conversion reaction mechanism.