Recovery of Molybdenum from Molybdenite
Molybdenite is a naturally occurring mineral composed of molybdenum sulphide. It is the primary ore used in the production of molybdenum metal and its compounds. The recovery of molybdenum from molybdenite involves several steps. This article describes the process used to separate molybdenum from molybdenite ore.
The first step in the process is to crush the molybdenite ore into small particles. This can be done using a jaw crusher, a ball mill, or a hammer mill. The ore is then dried and placed into a furnace for roasting. During roasting, volatile and non-volatile components of the ore are converted into oxides, which can be separated from the molybdenum.
Once the roasting process is completed, the molybdenite ore is cooled and then passed through a series of screens. The ore is sorted by size to remove larger pieces that may contain more molybdenum than is desired for the product. The ore is then placed in an agitated leach tank and is typically contacted with sulfuric acid. The acid breaks down the molybdenite and releases the molybdenum.
The molybdenum-bearing solution is collected from the leach tank and transferred to a clarification tank. The solution is clarified by adding a flocculant (a chemical used to cause suspended particles to join together and settle out of solution) such as lime. The settled solids are referred to as sludge, and the clarified solution is referred to as pregnant leach liquor.
The molybdenum-bearing leach liquor is then further purified by passing it through an ion exchange column. The resin beads in the column bind to the molybdenum and other impurities, thus purifying the solution. The molybdenum-bearing resin is periodically removed from the column and is treated with sodium hydroxide. This process releases the molybdenum and is referred to as elution.
The molybdenum-bearing eluant is then passed through a series of evaporators where the water is removed from the solution. After the water is removed, the resulting molybdenum-bearing solution is passed through a drying tower and the molybdenum is crystallized. The molybdenum crystals are then separated from the solution. Finally, the molybdenum crystals are heated to over 1150°C and then cooled rapidly, forming molybdenum metal or powder.
The molybdenum metal or powder can then be used in the manufacture of molybdenum-containing alloys, and other molybdenum-containing compounds. For example, molybdenum is used in the manufacture of high-temperature alloys and stainless steel, and is also used as an additive in lubricants and other products. The recovered molybdenum from the molybdenite ore has many uses, and is an important metal for many industries.
