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Growing global demand for rare earths is driving suppliers to mine and process rare earth minerals. Rare earth companies continue to explore for new resources, such as heavy mineral sand deposits, while mining existing mineral deposits.
To maximize the extraction of these valuable metallic elements, four rare earth minerals are primarily mined and processed industrially: bastnasite, monazite, xenotime, and ion-absorbing deposits.
Bastnaesite and monazite ores are rich in light rare earths and are important mineral sources for the extraction of cerium and lanthanum. Xenotime, on the other hand, contains large amounts of heavy rare earths and yttrium, making it an important mineral source for yttrium extraction. Ion adsorption mineral deposits are rare earth minerals unique to my country and contain high concentrations of heavy rare earth elements terbium and dysprosium. These elements are adsorbed in clay minerals in an ionic state.
Rare earth minerals are found in carbonates, pegmatites and other igneous rocks as well as placers produced by the weathering of hard rock sediments. Carbonatite is a high carbonate rock derived from hot magmatic fluids, while pegmatite is a coarse-grained rock found near igneous rocks and at the outer edges of intrusions. To a lesser extent, rare earth elements are also recovered as by-products of other minerals and from non-ferrous mineral tailings and industrial waste.
Depending on the composition and physical and chemical properties of the ore, rare earth minerals can be concentrated and beneficiated in a variety of ways. Rare earth minerals generally have significant differences in specific gravity, magnetic susceptibility and electrical conductivity compared to gangue minerals that usually dominate in rare earth ores.
Gravity concentration beneficiation takes advantage of the high specific gravity range of rare earth minerals (2.9-7.2), while most accessory gangue minerals have a specific gravity range of 2.5-3.5. The technique, exemplified by the classic gold digger's pan, involves gently shaking a pan filled with a suspension of "valid dirt" and water to wash away worthless sand grains from heavier gold particles. There are many commercial gravity concentration devices, including some that use centrifugal force to amplify specific gravity differences.
Magnetic separation depends on applying a magnetic field to a moving stream of gangue and releasing paramagnetic or ferromagnetic minerals, either as dry powders or as suspensions in water. In effect, the magnetic particles are attracted to permanent magnets or electromagnets, usually located within the conveyor head pulley. Non-magnetic particles fly out from the end of the head pulley and are discarded, while magnetic particles stick to the conveyor belt until the space between the pulley and the moving conveyor belt reduces the influence of the magnetic field and the particles fall through the chute onto the transfer belt.
Electrostatic separation exploits differences in electrical conductivity between particles. One type of separator applies a positive electrostatic charge to a moving stream of dry particles past a rotating horizontal metal cylinder. Conductive particles quickly lose their induced charge to the grounded cylinder and leave with a high trajectory, while less conductive particles temporarily remain electrostatically attracted to the cylinder and leave with a lower trajectory. The two product streams are directed through chutes onto conveyor belts which convey them to the appropriate point in the process.
Froth flotation is a widely used technology for beneficiating most metallic sulfide minerals and many non-metallic minerals, and is also effective for beneficiating certain rare earth minerals. Flotation is performed in an aqueous suspension of ore and gangue particles, and the technology relies on several steps. The process begins with the addition of reagents that (1) act as collectors that selectively attach to specific mineral particles through electrochemical attraction or chemical adsorption; (2) act as "foaming agents" by reducing the surface tension of water ; (3) As a "modifier", used to inhibit the flotation reaction of unwanted minerals.
Rare earth elements are currently recovered commercially from hard rocks (usually bastnasite or monazite), marine placers, and ionic clays. Hard rock ores must be crushed in a closed circuit using screens or mechanical classifiers to remove free particles before over-grinding occurs.
Xinhai Mining recommends that mining companies conduct beneficiation tests before beneficiation, and formulate beneficiation processes based on the differences between different ores. If you have any needs for rare earth selection, please call us for consultation and visit the factory.
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