China extracts vanadium from vanadium ore and stone coal, and the process flow of sodium salt roasting-leaching-acid precipitation-alkali dissolution-ammonium salt precipitation-ammonium metavanadate pyrolysis is mostly used. The main disadvantages of this process exposed in production are that a large amount of toxic gases such as hydrogen chloride and chlorine are produced during the roasting process, the wastewater contains a large amount of salt, which seriously pollutes the environment, and the conversion rate of vanadium is also low. To solve these problems, many experts have done a lot of research and proposed processes such as oxidation roasting of raw ore-alkali leaching, calcium salt roasting-ammonium carbonate leaching, acid leaching of raw ore or decarbonation leaching in a boiling furnace, bacterial leaching, sodium salt roasting-leaching of the residue with water and then acid leaching, which have achieved good results.
In foreign countries, vanadium is generally extracted using the acid leaching or sodium salt roasting-acid leaching-solvent extraction process. For example, the US Bureau of Mines uses the process of sodium salt roasting-solvent extraction-ammonium salt precipitation to extract vanadium from differentiated rocks in the state of Wyoming; the British company Mansfield uses the process of roasting with salt and sulphuric acid at high temperatures in a rotary furnace-leaching-precipitation to extract vanadium from the slag of copper smelting; and Poland uses the process of roasting with sulphuric acid-leaching process.
