Separation of V and Cr in alkaline aqueous solution using acidified primary amine N1923

Extraction and separation of V and Cr in alkaline aqueous solutions have attracted extensive interests in recent years due to successful development of the Sub-molten Salt Method for treating the vanadium-chromium complex magnetite ores, such as those from Pan-Zhihua in China. However, vanadium products with high purity are hard to be obtained directly by traditional chemical precipitation and crystallization separation from the alkaline leaching solutions obtained from the Sub-molten Salt Method, due to the chemical similarity between V and Cr. In present work, a new strategy by liquid-liquid solvent extraction using acidified primary amine N1923-isooctanol system is suggested to extract and separate V from Cr and Si co-existing in the strongly alkaline aqueous solutions with initial pH values even above 12. Experimental results revealed that co-extraction of V and Cr can be effectively avoided if some special inorganic salts, such as sodium sulfate, are previously added into the alkaline aqueous solutions. The influence from the added amount of sodium sulfate, initial aqueous pH value, acidification percentage of primary amine N1923, operation phase ratio, and initial concentration ratio of V to Cr, on separation behaviors of V from Cr and Si were investigated. Extraction isotherms, kinetics and extraction mechanism of V from alkaline solutions were also discussed. Stripping of V from the loaded organic phase and recycling of the organic phase were evaluated. The present work highlights a new approach to separate V from the strongly alkaline leaching solutions containing Cr and Si, and it exhibits great potential for promoting development of the Sub-molten Salt Method to treat the High Chromium Vanadium-Titanium Magnetite.