The purification of quartz sand is very difficult, mainly because it contains some impurity minerals, some of which containing iron elements, such as goethite, hematite, limonite, ilmenite, pyrrhotite, tourmaline, amphibole, biotite and so on.
These impurities greatly reduced the use-value of quartz sand, so the removal of iron from quartz sand is very important. The following introduces 7 methods and equipment for removing iron from quartz sand.
Gravity separation can usually be used effectively for the entire particle size range of quartz sand. When the iron in quartz sand is mainly in the form of heavy minerals (relative density > 2.9), gravity selection should be considered firstly. But gravity separation is difficult for mixed particles, flaky particles, light mineral particles and medium-density minerals.
Spiral chute gravity separation can be used when the material contains a particularly small amount of heavy mineral impurities (such as zircon). The greater the specific gravity difference of minerals, the higher the degree of separation.
When the spiral chute is used for beneficiation, the quartz mortar can be divided into three parts: granular heavy mineral area, granular quartz sand area, flaky and light quartz sand area. In this way, not only the heavy minerals in quartz sand can be removed by the spiral chute, but the mica minerals can also be removed partially.
Quartz, the main mineral in quartz sand, is a diamagnetic substance that cannot be magnetized in a magnetic field. The iron-containing impurity minerals in quartz sand, such as hematite, limonite, magnetite, goethite, etc., are mostly magnetic.
The quartz sand flotation method mainly removes iron-containing mineral impurities such as mica, feldspar, garnet and amphibole. A three-stage flotation process is used to remove iron-containing argillaceous, mica and feldspar minerals from quartz sand respectively.
If the finished quartz sand is reddish, and the iron and titanium content does not meet the product quality requirements, the acid leaching method can be used. Wash the quartz sand with water to remove powder and impurities, then carry out acid leaching before drying it.
Quartz sand acid leaching method (chemical treatment) has good iron removal effect, but the cost is higher, the technical requirements are stricter, and it is harmful to the environment. However, in order to obtain higher purity quartz sand, this chemical method will inevitably be used in the future.
Stirring and scrubbing are accomplished by friction between particles caused by violent agitation of the blades. However, since iron oxide films are thin and strong, this method is unlikely to remove them. If necessary, chemical reagents can be added.
Ultrasonic iron removal is mainly to remove the secondary iron film on the surface of the particles. When treated with ultrasonic technology for 10 min, its iron removal rate can generally reach 46% to 70%. In order to improve the effect of ultrasonic cleaning, a small number of reagents (such as sodium carbonate) and surfactants (such as water glass) can be added.
Ultrasonic iron removal is currently relatively expensive for the beneficiation of quartz sand, and it is still difficult to apply in large-scale concentrators, but for those who require high purity, low production is possible.
Microbial leaching of thin-film iron or immersion iron on the surface of quartz sand particles is a new technology for iron removal, which is currently in the research stage of laboratory and small-scale experiments.
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This chapter introduces the principle of how low-grade iron ores are upgraded to high-quality iron ore concentrates by magnetic separation. Magnetite is the most magnetic of all the naturally occurring minerals on earth, so low-intensity magnetic separators are used to upgrade magnetite ores. On the other hand, because oxidized iron ores like martite, hematite, specularite, limonite, and siderite are weakly magnetic, high-intensity magnetic separators and high-gradient magnetic separators are required to upgrade oxidized iron ores. Therefore, it is important to develop and optimize processing flow sheets according to the nature of iron ore to achieve both high recovery and high grade at a low cost. Three flow sheets for magnetite ores and seven flow sheets for oxidized iron ores separation are discussed.
Investigations were carried out, on a low grade siliceous iron ore sample by magnetic separation, to establish its amenability for physical beneficiation. Mineralogical studies revealed that the sample consists of magnetite, hematite and goethite as major opaque oxide minerals where as silicates as well as carbonates form the gangue minerals in the sample. Processes involving combination of classification, dry magnetic separation and wet magnetic separation were carried out to upgrade the low grade siliceous iron ore sample to make it suitable as a marketable product. The sample was first ground and each closed size sieve fractions were subjected to dry magnetic separation and it was observed that limited upgradation is possible. The ground sample was subjected to different finer sizes and separated by wet low intensity magnetic separator. It was possible to obtain a magnetic concentrate of 67% Fe by recovering 90% of iron values at below 200m size.
Dry beneficiation of magnetite ore using pneumatic planar magnetic separator (PMS).PMS performance was compared with that of wet magnetite beneficiation technologies.The outcomes showed PMS efficiency compared favourably with that of DTR.PMS showed superior performance than that of wet drum magnetic separator.The benefits of PMS as a unit operation in magnetite concentrators were discussed.
A novel low-intensity pneumatic planar magnetic separator designed to recover and concentrate fine-grained magnetite minerals is investigated and the performance compared with those of conventional wet magnetic separators, i.e., Davis tube tester and drum magnetic separator. The results of the studies show that the magnetite recoveries and grades achieved by the novel planar magnetic separator compare favourably with that of the Davis tube tester. Moreover, the outcomes of the studies show that the magnetite concentrates recovered by the planar magnetic separator showed higher magnetite grades with fewer impurities than that of the wet drum magnetic separator. The findings from the study show that the planar magnetic separator could be a potential laboratory-scale substitute for the Davis tube tester, as well as replace wet magnetite beneficiation technologies in drought-ridden and remote regions where the paucity of water could be a potential economic challenge to wet processes.