Research On Separating Molybdenum From Tungsten By Solvent Extraction Using H₂O₂ As Complex Agent

Separation of molybdenum from tungsten by solvent extraction using the hydrogen peroxide as complex agent from ammonium tungstate solution containing high molybdenum was studied in this paper. The extracting agent is a dual mixed extractant, being made up of neutral extractant A and B having small water solubility. In ammonium tungstate solution, the concentration of WO3 is 110～160 g/L, the ratio of Mo/WO3 is about 0.1～0.15. The solution almost contains no impurities such as P, As, Si, F and so on. The research focuses on the basic properties of hydrogen peroxide complexation extraction, simulation of counter-current cascade experiments and mixer settler cascade experiments. The results indicate that, the extraction system has a good ability for molybdenum extraction, a good separation efficiency for molybdenum and tungsten and low tungsten loss. The results of the research provide a reliable basis for the industry application of the process.Experiments identified the preparation method of feed liquor by hydrogen peroxide complexation, investigated the stability of the feed liquor. Basic properties of extraction and stripping were studied. This paper selected organic phase composition,3%A+42%B+55%sulphonated kerosene. Suitable stripping agent was selected. The influence of various factors in extraction, stripping were investigated. Extraction isotherms for Mo were plotted at different pH value of the feed liquor, showing the saturated capacity of the organic phase for molybdenum. The results show that the extraction system can effectively gathers molybdenum to realize separation of molybdenum from tungsten. The equilibrium time is very short. The influence of dosage of H2O2, equilibrium pH value of water phase, temperature is the key to extraction and separation of Mo from WO3. When pH value of the feed liquor is 1.04,1.60,2.00, the saturated capacity of the organic phase for Mo, in turn, is 10.1 g/L,9.2 g/L,7.63 g/L. Loaded organic phase can be stripped easily with NH4HCO3 solution.The theoretical stage number was obtained by McCabe-Thiele graphics when pH of the feed liquor is 1.60. Counter-current extraction was completed in separating funnels. Using six stages countercurrent extraction and adjusting pH of aqueous phase in the third stage, the measures guaranteed high extraction ratio of molybdenum and reduced tungsten loss. In this case, extraction ratio of molybdenum is 98%, extraction ratio of tungsten is only 2%, and Mo/WO3 of the feed liquor was reduced from 0.1-0.15 to lower than 0.002.Six stages countercurrent extraction and two stages countercurrent stripping were completed in mixer settler, the results show the separation effect is good. The ratio of MO/WO3 can be reduced from 0.1～0.15 to 0.0025 below and the loss of tungsten is small. The organic phase after stripping was directly used for extraction. The ratio of MO/WO3 of the stripping liquid reachs more than 20. It is helpful for recovery of molybdenum.