Calcification Roasting Research Articles

Selective leaching of vanadium in calcification-roasted vanadium slag by ammonium carbonate

Calcification roasting is a clean way to extract vanadium from the vanadium slag. But the subsequent sulfuric acid leaching brings the impurity of phosphorous into the leach liquor of vanadium and thus inhibits the precipitation of vanadates for vanadium recovery. In this paper, a novel selective leaching method using ammonium carbonate ((NH4)2CO3) has been proposed for the extraction of vanadium in the calcification-roasted vanadium slag. The (NH4)2CO3 leaching can dissolve calcium vanadates with high selectivity while maintaining other impurities including phosphorous in the solid residue. Ammonium vanadate can be precipitated directly by cooling down without pH adjustment or ammonium salt addition, which makes the (NH4)2CO3 leaching cost-effective. The waste water after precipitation can be recycled back to the leaching circuit, showing the friendliness of (NH4)2CO3 leaching method to the environment. With (NH4)2CO3 leaching, 96.0% of vanadium can be dissolved while the corresponding leaching efficiency of phosphorous is 9.2% using the most suitable condition of solid/liquid ratio 1:20, particle size 45–74μm, leaching temperature 80°C, (NH4)2CO3 concentration 600g/L and leaching time 70min. This work has laid the foundation for the industrial application of ammonium carbonate leaching and provided new insights into selective leaching of valuable elements in complex minerals.

The role of CaO in the extraction of Ni and Mo from carbonaceous shale by calcification roasting, sulphation roasting and water leaching

The role of CaO in the extraction of Ni and Mo from carbonaceous shale by calcification roasting, sulphation roasting and water leaching was studied. Experimental results showed that 97.23% Mo and 93.16% Ni were extracted from the Ni–Mo ore by mixing 100 g the raw Ni–Mo ore with 36 g CaO and grinding to less than 106 μm, then oxidation roasting at 700 °C for 2 h, sulphation roasting with 70 ml 98% sulphuric acid at 240 °C for 2 h and, water leaching at 98 °C for 2 h with a liquid/solid ratio of 2:1. But only 60.67% Ni was extracted for the oxidation roasting without adding CaO. The addition of CaO in the ore is both propitious to environment protection and nickel extraction. XRD analysis showed that the nickel in the calcification roasted ore was in the form of NiO, while the nickel in the oxidation roasted ore was in the form of NiFeO 4. It was found that the NiFeO 4 formed in the oxidation roasted Ni–Mo ore was included by chemically inert iron silicates, which results in the NiFeO 4 irresolvable in sulphuric acid. Experiments confirmed that CaO can decompose not only the NiFe 2O 4 but also the iron silicates at the roasting temperature.