Magnetic separation method of quartz sand
Mechanical scrubbing is the purpose of removing iron by removing the film iron from the surface of quartz sand and the iron containing minerals on the surface of quartz sand with the aid of the mechanical force and the collision and friction between the sand particles. At present, the scrubbing technology is mainly grinding, scrubbing and mechanical scrubbing. For mechanical scrubbing, it is generally believed that the factors that affect the scrubbing effect mainly come from the structural features and configuration forms of the scrubbing machine, followed by the technological factors, including the scrubbing time and the scrubbing concentration.
Quartz, the main mineral in quartz sand, is a diamagnetic substance which cannot be magnetized in a magnetic field. The impurity minerals of iron in quartz sand are hematite, limonite, magnetite, goethite and so on. Most of them are magnetic materials which can be magnetized in magnetic field. In magnetic separation process, the iron impurity minerals in quartz sand can be removed by magnetic separation by using the difference of this property.
Ultrasonic iron removal
Ultrasonic is a kind of high frequency (frequency more than 20000Hz) sound wave, which is transmitted by medium. It has mechanical energy. It can interact with medium in the process of propagation, which produces mechanical effect, thermal effect and cavitation effect. When ultrasonic waves are emitted in water (or solution), many regions of compression and expansion are produced, resulting in the formation and rupture of numerous microbubbles (cavitation bubbles), which are called cavitation. In the process of cavitation, the pressure inside the liquid changes abrupt, and is accompanied by shock waves. The pressure can reach several thousand to tens of thousands of atmospheric pressure. Under the action of this shock wave, the iron impurity adhered to the surface of the particle will fall off the particle surface and enter the liquid phase, thereby achieving the purpose of removing iron. The removal of iron by ultrasonic is mainly the removal of secondary iron thin films (i.e. "thin film iron") on the surface of particles. The iron thin film is firmly bonded and the mechanical scrubbing method used in mineral processing can not be separated. Using ultrasonic technology to treat natural silica sand containing "thin film iron" has the characteristics of short time and high efficiency.
Flotation removal of iron
Flotation is mainly used to separate feldspar from quartz sand, but it can also be used to remove mica and other clay minerals and secondary iron in quartz sand. The most typical process is using hydrofluoric acid as an activator and flotation with amine cation collectors under strong acidic conditions (pH2 to 3).
There are three kinds of flotation methods: the first is fluorine and acid. This method is widely used because of its good flotation effect, easy control and stable index. However, the erosion of fluorine ions to the land and the damage to the surrounding ecological environment are great. The second is fluorine free acid method. The greatest advantage of this method is to avoid the use of fluorine ions that have destructive effects on the environment, and the production index is stable, but the corrosion effect of strong acid on mineral processing equipment can not be ignored. There is a high requirement for floatation equipment. The third is fluorine free and acid free method. Under the natural pH condition, a unique high concentration mineral slurry flotation environment is created by rational distribution of the ion collector of yin and Yang, so as to achieve the priority of flotation of impurities in the mineral. However, because this method has strict requirements for raw sand treatment and pulp environment, it is not easy to control production, and it is not widely used at present.
Microbial iron removal
The film iron or impregnated iron on the surface of quartz sand particles by microorganism is a newly developed iron removal technology, which is currently in the laboratory and small test stage. According to the overseas research results, Aspergillus niger, Penicillium, phaffiform fungus and other microorganisms have achieved good results in removing iron oxide from quartz surface. The study also found that the effect of bacteria and mold on the leaching of iron was better. The rate of iron decomposition by anaerobic bacteria is slower than that of aerobic bacteria. The sensitivity of different iron oxide minerals to bacterial leaching is different. The dissolution of iron from limonite is slower than that from goethite, but it is much faster than that from hematite.