Preparation of NH₄VO₃ by Carbonation Leaching of Calcium Vanadate

In view of the problems of high Na/V ratio and low vanadium concentration of carbonation leaching solution of calcium vanadate,a new method of preparing ammonium metavanadate by mixed leaching of sodium bicarbonate and ammonium bicarbonate was proposed.The effects of the leaching agent compositions,CO₃^2-/Ca²⁺,leaching temperature and liquid-solid ratio on the leaching effect were studied.The results show that under the conditions of Na HCO₃∶NH₄HCO₃=1∶1,CO₃^2-/Ca²⁺=1.1,leaching temperature of 90℃and liquid-solid ratio of （4～5）:1,the leaching solution with 43.87～54.57 g/L of vanadium concentration and the vanadium leaching rate of 97.80%～98.01% can be obtained.Ammonium metavanadate is precipitated by ammonium bicarbonate in the leaching solution,and the vanadium precipitation rate is 91.31%.The vanadium product meets the quality control index requirements.