Solvent extraction of molybdenum blue from alkaline leaching solution of the Ni-Mo ore

Molybdenum in the Ni-Mo ore was leached by air oxidation in an alkaline solution. Due to the high concentrations of SO₄²⁻, S₂O₃²⁻, SO₃²⁻ and AsO₄³⁻ in the solution, it was difficult to efficiently extract Mo by chemical precipitation or ion exchange process. So the extraction of Mo from the solution with the mixture of tertiary amine (N-235) and secondary caprylic alcohol dissolved in kerosene was investigated. The effects of several process parameters such as extractant concentration, feed solution pH, O/A ratio, temperature of extraction, and contact time were studied. Results proved that the extraction efficiency of Mo was 99.4% at pH 3, time 2 min and O/A ratio 1:4 with 15 v% N-235. Stripping of Mo with a 15 m% ammonia solution was essentially completed (99.9%) in a single stage at an O/A ratio of 3. Comparison of the chemical oxygen demand (COD) concentration of the feed solution (12,400 mg/L) and raffinate (8600 mg/L) indicated that the separation of Mo and reductive substances, such as S₂O₃²⁻ and SO₃²⁻, was achieved after solvent extraction. The Mo concentration in the strip liquor obtained in a single stage can be increased by contacting a new loaded organic phase. After repeated stripping, the concentration of Mo, As, P, W and V in the strip liquor were 125.82 g/L, 15.63 g/L, 0.73 g/L, 0.09 g/L, and 0.074 g/L respectively.