A novel method to extract vanadium and chromium from vanadium slag using molten NaOH-NaNO3 binary system

A new method using NaOH‐NaNO3 binary melts to treat vanadium slag is proposed. Vanadium and chromium can be simultaneously extracted in the leaching processes. Under the optimum reaction conditions, the recovery of vanadium and chromium can reach 93.7% and 88.2% in 6 h, respectively. The kinetics investigation indicates that the decomposition of vanadium slag is controlled by mass transfer in product layer. During the reaction, NaOH is believed to provide basic media and facilitate the dissolution of acidic oxides. NaNO3 decomposes to produce a large amount of active oxygen species, such as O, O22−, and O2−. NaOH intensifies the decomposition of NaNO3 to NaNO2, but inhibits further decomposition of NaNO2. NaNO3 can be regenerated by oxidation of NaNO2 using oxygen at high temperature. The apparent activation energy of NaNO2 oxidation in the temperature ranging from 350 to 450°C is 105.5 kJ/mol. © 2012 American Institute of Chemical Engineers AIChE J, 59: 541–552, 2013