INVESTIGATION OF REACTION STOICHIOMETRY OF LEACHING OF SYNTHETIC CaWO4 IN H2C2O4 SOLUTIONS

Abstract

In this study, leaching characteristics of CaWO4 in H2C2O4 solutions and reaction stoichiometry were investigated. Solutions were taken from the reactor and dissolved Ca and W were analyzed quantitatively by ICP-OES instrument. Leach residues and solid products obtained by evaporation of leach solutions were characterized by XRD, TGA-DTA-MS and FT-IR analyses. It was found that leaching reaction took place via decomposition of Ca[WO3(C2O4)H2O] intermediate chelate compound formed in the first step to H-2[WO3(C2O4)H2O] final chelate compound formed in the second step. It was also seen that H-2[WO3(C2O4)H2O] chelate compound was not stable and it began to decompose by forming H2WO4 precipitate after a certain time. Overall leach reaction was determined as CaWO4 ((s)) + 2 H2C2O4 ((aq))+ H2O ((l)) - H-2[WO3(C2O4)H2O] ((aq)) + CaC2O4H2O ((s)).