Study on Calcified Alkali Leaching of Vanadium-Extracted Tailings and Preparation of Barium Orthovanadate

While vanadium-extracted tailings contain valuable components, their utilization is difficult due to their high sodium content. In this work, a new oxygen-pressure calcification and alkaline leaching strategy to achieve barium orthovanadate vanadium precipitation is developed to realize the resourceful recycling and utilization of vanadium-extracted tailings. First, the preparation of barium orthovanadate via calcified alkaline leaching and vanadium precipitation was studied, and the effects of CaO addition, NaOH concentration, leaching temperature, and liquid–solid ratio on the leaching rates of sodium and vanadium were evaluated in single-factor experiments. Under the optimum leaching conditions (CaO addition of 20%, alkali concentration of 150 g·L⁻¹, leaching temperature of 180 °C, and liquid–solid ratio of 10:1), the leaching rates of vanadium and sodium reached 85.25% and 82.36%, respectively. Subsequently, the vanadium-containing leaching solution was subjected to a vanadium precipitation test, and the effects of pH, Ba(OH)₂ addition (expressed as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">n</mi><mrow><mi>Ba</mi></mrow></msub><mo>/</mo><msub><mi mathvariant="normal">n</mi><mi mathvariant="normal">V</mi></msub></mrow></semantics></math></inline-formula>), vanadium precipitation temperature, and vanadium precipitation time on the vanadium precipitation rate were investigated. Under the optimum vanadium precipitation conditions (pH 14, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">n</mi><mrow><mi>Ba</mi></mrow></msub><mo>/</mo><msub><mi mathvariant="normal">n</mi><mi mathvariant="normal">V</mi></msub></mrow></semantics></math></inline-formula> = 1.5:1, temperature of 30 °C, reaction time of 60 min), a vanadium precipitation rate of more than 99% was achieved. The precipitated vanadium product of this reaction was confirmed to be Ba₃(VO₄)₂ with a purity of more than 99%. Notably, the wastewater generated during the test process can be mixed with an alkali and returned to the leaching process for reuse, and the dealkalized residue can be used as a raw material for ore reduction in iron smelting processes.