Alkali fusion using sodium carbonate for extraction of vanadium and tungsten for the preparation of synthetic sodium titanate from spent SCR catalyst

Alkali fusion method to extract vanadium and tungsten from spent SCR catalyst and to simultaneously prepare synthetic sodium titanate for the purpose of preparation of feedstock for TiO 2 manufacturing by hydrometallurgical processing was investigated. Based on the Na 2 O-TiO 2 phase diagram and experimentally obtained results, appropriate alkali-fusion temperature and molar ratio (MO x /Na 2 O + MO x ) were determined to prepare soluble vanadium, tungsten salts, and sodium titanate. As results, the extraction efficiency of vanadium and tungsten was >99% and sodium titanate as feedstock for making TiO 2 was obtained under the following alkali fusion conditions: Temperature, 950 °C; reaction time, 20 min; molar ratio, 0.5. When the molar ratio (MO x /Na 2 O + MO x ) was less than 0.5, complete liquidized product (eutectic melt of the feedstock and Na 2 CO 3 ) was obtained at the given conditions. This method, compared to conventional alkali roasting, is advantageous for rapid synthesis of water-soluble compounds for leaching of vanadium and tungsten, and for use as feedstock for the preparation of TiO 2 by hydrometallurgical route.