In various applications of quartz sand, iron is the most harmful impurity, and the purification of quartz sand is generally the main purpose of removing iron.
First, the state of iron in quartz sand
The state of occurrence of iron impurities in quartz sand determines the extent to which it can be removed and removed. The iron content in quartz sand increases with decreasing particle size because particles with small particle size contain more heavy minerals and feldspars , which are less weather resistant than quartz. According to the specific situation of quartz sand, the occurrence state of iron can be divided into five forms:
(1) Among clay minerals
In general, the exposed deposits contain more weathered clay. This clay is weathered from limestone , feldspar, shale, etc. The main component of clay contains natural water-formed vanadium silicates of quartz, mica , limonite, calcite and chlorite. Small (10um or less).
(2) Heavy minerals and magnetic minerals
Heavy minerals are minerals whose relative density is greater than 2.9. Most of these minerals are magnetic or weakly magnetic, and iron is an essential element in these minerals.
(3) Light minerals
Light minerals mainly refer to feldspar. Al in feldspar is sometimes replaced by Fe, which can be as high as 0.5% to 0.7%. In addition, there are muscovite, kaolinite, dolomite, calcite, etc. Among these minerals, Fe exists in the crystal lattice in the form of isomorphism, and since its density is similar to that of quartz, separation is quite difficult.
(4) Thin film iron
The particles in quartz sand are white under pure conditions and are brown, gray, yellow or even red after being contaminated. The pollution of quartz particles is mainly iron pollution and muddy pollution. In the process of mineralization, a certain mineral is produced in the form of thin film or particulates inside or on the surface of quartz minerals. The iron pollution caused by this mineralization process is more difficult to eliminate. In fact, the so-called thin film iron mostly refers to this situation.
(5) in the living body or in the lattice
The different minerals in quartz sand are basically in the state of dissociation of the monomer, but the condition of the particles in the quartz sand and other iron-bearing minerals still exist. This continuum is mostly dark mineral, and some are wrapped in it. The inside of the particles, some embedded in the edge of the particles, becomes a mineral aggregate, which is called wrapped iron.
Method for removing iron from quartz sand
For several states of iron, the wrapped iron cannot be separated. If it is to be removed, the particle size needs to be further reduced to dissociate the monomer, which is inconsistent with the grain size requirements of the quartz sand application. There are many ways to remove iron from quartz sand, but some are currently only successful in the laboratory and have not been used in industrial production. At present, quartz sand removal methods can be divided into three categories: physical-mechanical methods, chemical methods and microbial beneficiation methods.
2.1 Physical-mechanical methods
The physical-mechanical methods mainly include scrubbing, re-election, flotation, ultrasonic beneficiation, magnetic separation and water washing, etc. These methods mainly deal with coarse impurities.
(1) Washing and grading de-sludge
Because the grain size of quartz sand is generally much larger than the particle size of clay minerals, simple water washing can remove clay minerals from quartz sand. Meanwhile, as the fine silica particles becomes larger, heavy mineral particles and feldspar content, they are not as resistant to weathering grade silica impurities, aluminum, iron and the like but increased mass, SiO2 grade decreases, so The water selection and grading desilting of quartz sand not only removes clay minerals, but also removes fine minerals below 0.1 mm. However, the film iron on the surface of the quartz sand is difficult to remove.
(2) Magnetic separation
Quartz sand magnetic separation process
The magnetic separation method has the advantage of high selectivity and high quartz sand production while maintaining effective removal of impurities. The impurities removed mainly include magnetite-based ferromagnetic minerals and weak magnetic impurity minerals mainly composed of hematite, limonite and biotite. For minerals with strong magnetic impurities, magnetic weakening or medium magnetic machines are used for magnetic separation; for weak magnetic impurity minerals, strong magnetic machines above 10 6 e are often used. However, the content of ferromagnetic minerals in quartz sand is very small, and very few sand mines can use weak magnetic machines to reduce the amount of iron. Therefore, it is the main strong magnetic machine for quartz sand beneficiation.
(3) Scrub
At present, scrubbing mainly includes agitation scrubbing and rod scrubbing. Stirring scrubbing relies primarily on the intense agitation of the blades to cause friction between the particles. The main factors affecting the scrubbing effect are the structure and configuration of the mixing equipment and the scrubbing concentration and scrubbing time in the process. Because of its many influencing factors, and the strong grinding of sand, it puts high demands on the wear resistance of the equipment. Therefore, the purification effect of the stirring scrub is not ideal. However, compared with the agitation scrubbing, the rod scrub can not only remove the impurities on the surface of the quartz sand, but also remove the impurities at the unevenness and the small gap, almost twice the friction scrub, but the thin film iron on the quartz sand surface is difficult to remove. Therefore, it is only a method of quartz sand pretreatment.
2.2 Chemical methods
The chemical treatment is mainly treated with a mineral acid or a reducing agent, and is suitable for obtaining a high purification effect. Acid leaching and pickling are common chemical treatment methods. Pickling process can be divided into cold and hot acid leaching acid leaching, there is used hydrochloric acid, sulfuric acid and hydrofluoric acid, the removal of mineral impurities have better effects of these acids on metal in quartz sand, especially for Fe The removal effect of Al and Al is obvious. The main factors affecting the acid leaching purification effect are the composition of the acid, the concentration and amount of the acid, the temperature, and the time. After acid leaching, high-purity quartz sand or even ultra-high-purity quartz sand with a purity of 99.99% can be obtained.
The complex law is to use quartz sand in the acid leaching process, the acid can form a complex with the impurity ions and dissolve in water, thereby achieving the purification effect. The acids commonly used in complexation are mainly oxalic acid and acetic acid. It has been reported in foreign countries that F. Viglio et al. used oxalic acid as a leaching agent to remove iron impurities in quartz sand. The content of Fe 2 O 3 in quartz sand decreased from 110 ppm to 10 ppm, and the iron removal rate reached 80-90. More than %, but it has certain requirements on the grain size of quartz sand (average particle size 20um).
2.3 Microbial law
Microbiological iron removal is a newly developed technology and is currently in the research stage of laboratories and small trials. According to a report by Bulgarian SNGrudev et al., they tested that microorganisms such as bacteria and molds have achieved good results in removing iron from quartz sand. Aspergillus niger has the best iron removal effect, mainly producing a main component of citric acid and oxalic acid. The bacterial culture solution, in the second-stage beneficiation, the quartz sand is immersed in the culture solution at a temperature of 90 ° C, so that the content of Fe 2 O 3 in the quartz sand can be reduced to 0.012%, which is very suitable for producing high-quality glass.
In addition to the common ones, quartz sand purification technology includes electrostatic purification technology and radiation purification technology. Electrostatic purification technology is based on the different conductivity of minerals, mainly for the separation of feldspar and quartz. Radiation purification technology is a new method based on the special properties of some elements in minerals, especially for the sorting of blocks.
In practical applications, it is rare to use only one method to produce qualified quartz sand. It is often a combination of physical methods and chemical methods to achieve purification standards.
Chinese car radiator;Radiator for Chinese Car;Chinese car oem radiator
JIANGSU KALLER AUTO PARTS THCHNOLOGY CO.,LTD , https://www.jskaller.com