Synthesis of scheelite from sodium tungstate solution by calcium hydroxide addition

Sodium tungstate solution can be prepared by decomposing wolframite with sodium hydroxide. A new technique is developed for precipitating scheelite from the sodium tungstate solution by the addition of calcium hydroxide. In this study, the effects of several variables on the conversion of sodium tungstate are investigated. Results show that the effects of temperature and sodium tungstate concentration are significant. Specifically, 96.4% WO42− was converted to scheelite in 2h at 100°C with a calcium hydroxide stoichiometric ratio of 1.4 and a stirring speed of 350rpm. The parent solution containing sodium hydroxide can be recycled as a leaching agent return to the wolframite decomposition process.