Separation of molybdenum from peroxotungstic acid solution by solvent extraction with TBP and TRPO

An increasing problem facing the tungsten industry is developing an effective separation of molybdenum from peroxotungstic acid solutions due to the similarities of these two metals. This study herein separates molybde-num from peroxotungstic acid solution for the selective production of tungsten from scheelite acid decomposition residue using hydrogen peroxide. Solvent extraction was the main method employed, and the feed was perox-otungstic acid solution containing peroxomolybdic acid. The concentration of tungsten and molybdenum in the feed and the raffinate were measured by Inductively Coupled Plasma (ICP) to characterize the separation effi-ciency. The results showed that in the peroxide solution, an organic phase of tributyl phosphate (80 %), trialkyl phosphine oxide (2 %), and sulfonated kerosene (18 %) was used effectively to separate molybdenum from tungsten in acid leach solutions. A maximum single-stage separation coefficient of 400 was reached under the following extraction conditions: temperature, 25 degrees C; contact time 4-6 min; separation time 4 min; and organic to aqueous ratio, 1.2. Using ammonium bicarbonate as the stripping agent, the stripping ratio of molybdenum and tungsten were 83 % and 33 %, respectively, and the corresponding separation coefficient was 10.