METHOD OF PREPARING CALCIUM TUNGSTATE, VANADATE AND MOLYBDATE AND MIXTURES OF SAME

摘要

The invention relates to a method of preparing calcium salts from the group containing calcium molybdate, calcium vanadate, calcium tungstate and mixtures of same. The inventive method is characterised in that it comprises the following steps consisting in: a) using spent catalysts comprising a metal or a combination of metals, selected from among molybdenum, vanadium, tungsten and mixtures of same; b) roasting the spent catalysts from step (a) at a temperature varying between 700 and 1100 °C in excess air in order to obtain roasted catalysts and particulate matter; c) leaching the roasted catalysts and/or particulate matter obtained in step (b) using a base solution; d) purifying the aqueous leaching solution obtained in step (c) and comprising elements from the group containing molybdenum, vanadium, tungsten and mixtures of same, by means of treatment at neutral pH at approximately 90 °C; and e) precipitating the calcium salts from the group containing calcium molybdate, calcium vanadate, calcium tungstate and mixtures of same in the purified aqueous leaching solution obtained in step (d), using calcium compounds. The invention also relates to the use of calcium salts selected from among calcium molybdate (CaMoO4), calcium vanadate (CaV2O6), calcium tungsate (CaWO4) and mixtures of same, which are obtained using one such method for producing alloy steels.