Extraction of Molybdenum from Low-Grade Molybdenum Concentrates

Using roasting,ammonia leaching and alkaline leaching,the extraction of molybdenum from low-grade molybdenum concentrates was studied.The experimental results showed that the addition of the sodium carbonate increases the leaching rate of molybdenum by accelerating the decomposition of calcium molybdate.The optimum conditions for the molybdenum extraction are as follows: the roasting temperature is 600 ℃,the roasting time 2 h,the ammonia leaching temperature 80 ℃, the excess coefficient of aqueous ammonia 1.4,the dosage of the sodium carbonate 467 kg/t and the ratio of liquid to solid 4∶1.The leaching residue was treated by hydrochloric acid leaching(HCl) method and alkaline leaching(Na2CO3+NaOH) method separately to further leach molybdenum.The recovery rate of molybdenum in the residue is only 34.92% by the former method and,meanwhile,the leaching process by this method is difficult to control,showing that the method is not practicable.In the latter method,the dosages of the sodium carbonate and sodium hydroxide are 533 and 433 kg/t,respectively.The scale-up experiment showed that the total recovery rate of molybdenum is up to 96.8%.