【China Molybdenum Industry News Network】
The mixture obtained by either of the above methods is then heated at least to the temperature of reaction of the sodium compound, to produce sodium molybdate. I have found 7000 C. to be satisfactory in the case of NaNO3. This temperature is maintained until the formation of sodium molybdate is completed. The time required has been found to be about one hour. It is not necessary to stir or rabble the ore mixture during this step.
The sintered ore is then leached with water and filtered. It has been found to be unnecessary to remove the last traces of solid matter at this stage.
Magnesium chloride, preferably in aqueous solution, is then added to the extracted molybdenum solution which is vigorously agitated, while heating, until the sodium molybdate solution is almost neutral, and until carbon dioxide (if present) is entirely eliminated. Alternatively, the magnesium chloride may be partly replaced by some other neutralizing agent, such as nitric acid, which may be economically obtained by suitable treatment of the fumes escaping from the sintering furnace when employing sodium nitrate as decomposition agent.
It is not usually advisable, however, to dispense entirely with magnesium chloride as neutralizing agent, since one of its functions is to form insoluble magnesium compounds of arsenic and phosphorus, and thus eliminate these objectionable impurities from the molybdenum solution.
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