A Feasible Strategy for Deeply Separating Low Concentrations of Molybdenum from Tungstate Solutions with a High-Efficiency Microbubble Floating-Extraction Concept

Deep separation of low concentrations of molybdenum from tungstate solution has been a technical bottleneck in tungsten metallurgy and subsequent value-added utilization of tungsten products. A feasible strategy, named microbubble floating-extraction, was proposed and employed to achieve the high-efficiency and deep separation of molybdenum from tungstate solutions in this work. It was demonstrated that reagent mineralization is crucial for the formation of MoS₄^2––N263 hydrophobic complexes, which is the rate-determining step of microbubble floating-extraction. Owing to the higher bubble and interface mass transfer rates, microbubble floating-extraction can achieve high-efficiency enrichment and deep separation of MoS₄^2––N263 complexes with a large aqueous-to-oil phase ratio. The separation mechanisms of microbubble floating-extraction include the attachment process of MoS₄^2––N263 hydrophobic complexes on the surface of rising microbubbles and the mass transfer process at the oil–water interface. Compared with solvent extraction, the flotation efficiency of molybdenum increases from 98.61 to 99.14%, while the loss rate of tungsten decreases from 3.31 to 2.12% under the optimal conditions. The microbubble floating-extraction exhibits significant advantages of high separation efficiency, a high enrichment coefficient, and low consumption of organic solvents.