Hydrometallurgical recovery of vanadium and calcium from electric arc furnace slag in hydrogen based steelmaking

• V and Ca are selectively recovered from electric arc furnace slag. • Ca and Mg compose >99 wt% of dissolved elements in the first-stage leachate. • (NH 4 ) 2 CO 3 medium outperforms the Na 2 CO 3 medium in aqueous V leaching. • The low solubility of NH 4 VO 3 appears to limit the dissolution of V in Ca stage. A two-stage direct leaching method has been applied to selectively recover calcium (Ca) and vanadium (V) from electric arc furnace slag obtained from pilot-scale smelting of hydrogen-reduced iron. Nitric acid-ammonium nitrate-water (HNO 3 -NH 4 NO 3 -H 2 O) medium was used in the first stage to produce leachate in which Ca and magnesium (Mg) composed over 99 wt% of the dissolved elements. Sodium carbonate-sodium hydroxide-water (Na 2 CO 3 -NaOH-H 2 O) and ammonium carbonate-water ((NH 4 ) 2 CO 3 -H 2 O) were investigated as alternative media for the V leaching stage. The effects of the medium composition, temperature, and liquid-to-solid ratio on element recoveries and selectivity were studied for both stages with the aid of experimental designs. Regression models were fitted that could adequately reproduce the general trends in the data and allowed the optimization of the process within the studied variable space. Under optimum conditions, 55 % Ca was recovered with 91 % selectivity. In the subsequent V leaching stage, (NH 4 ) 2 CO 3 -H 2 O proved to be a more promising medium, achieving V recovery of 39 % and selectivity of 90 % under the optimum conditions.