Extraction of molybdenum(VI) from sulfate media by 3-pyridineketoxime and its quaternary salts

Hydrophobic complexing agents: 1-(3-pyridyl)undecan-1-one oxime and its quaternary salts (3-[1-(hydroxyimine)undecyl]-1-propylpyridinium bromide and 3-[1-(hydroxyimine)undecyl]-1-propylpyridinium chloride) were investigated as extractants of molybdenum(VI) ions from sulfate media. The extraction of Mo(VI) was studied as a function of several variables: equilibrium pH, acid, extractant and modifier concentrations, as well as phase ratio and contact time. The extraction of Mo(VI) was found near-quantitative for all studied compounds especially from solutions of pH 2.5, but 3-[1-(hydroxyimine)undecyl]-1-propylpyridinium chloride appeared to be the most efficient extractant of Mo(VI) from sulfate media. This salt was the most suitable extractant in terms of loading capacity and a fast stripping process with sodium nitrate and sodium or ammonium sulfate solutions. 1-(3-Pyridyl)undecan-1-one oxime was a slightly weaker extractant towards molybdenum(VI) ions, but in comparison to its quaternary salts this reagent formed more stable complexes and the re-extraction proceeded in 50%.