Direct solvent extraction of molybdenum(VI) from sulfuric acid leach solutions using PC-88A

• Mo(VI) was highly selectively extracted by PC-88A directly from high acidity leach solutions.
• The saturation extraction capacity of Mo(VI) on the organic solution reached 60 g/L.
• The concentration of Mo(VI) in strip liquors reached as high as 146 g/L.
• The extracted Mo(VI) species of Mo2O5 (HA2)2 was identified.

The extractant 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) was used to directly extract molybdenum(VI) from high sulfuric acid leach solutions containing 3 mol/L H+. The effects of extractant concentration, solution acidity and type of stripping reagent on the recovery of molybdenum(VI) were investigated. The saturated loading capacity of molybdenum(VI) with 40% PC-88A in sulfonated kerosene was 60 g/L. More than 98.7% of the molybdenum(VI) was extracted in a four-stage counter current extraction using an organic system consisting of 40% PC-88A and 60% sulfonated kerosene and a feed containing 17.3 g/L Mo(VI) and 157.3 g/L H2SO4 with an A/O ratio of 3/1 at 20 °C for 5 min. The extracted molybdenum(VI) species of Mo2O5(HA2)2 in loaded organic solutions were identified by the combination of slope and saturation methods, and further proved by FTIR spectral analysis. The stripping of molybdenum(VI) was completed in a two-stage counter current stripping using 6 mol/L of NH3 with an A/O ratio of 1/1.5 at 30 °C for 5 min. The concentration of molybdenum(VI) in the strip liquor reached as high as 146 g/L.