Pure quartz is clear. Color variance due to impurities: purple (amethyst), white (milky quartz), black (smoky quartz), pink (rose quartz) and yellow or orange (citrine).
vitreous, waxy, dull
Quartz sand, also known as silica sand, is a common non-metallic mineral raw material and has a wide range of applications.
Low-grade quartz sand can be used in the construction, glass manufacturing, ceramics, and foundry industry.
High-purity and ultra-high-purity quartz sand made by beneficiation and purification have been widely used in aerospace, atomic energy technology, laser, optical cable communication, military, and other high-tech fields.
Quartz sand purification is a difficult separation process to remove impurities from quartz sand and obtain refined quartz sand or high-purity quartz sand (such as electronic grade quartz).
The grade of SiO2 in quartz sand decreases as the grain size of quartz sand becomes thinner, but the grades of impurity minerals such as iron and aluminum increases. This phenomenon is particularly noticeable in quartz sand containing a large amount of clay.
Washing, grading, and desliming usually as a pre-processing operation set before the beneficiation.
For example, the chemical composition of the quartz sand ore in the Suling Malingshan Mine in is SiO2 79. 38%, Fe2O3 1. 68%, AL2O3 11.28%, and its particle size composition is -0.1 mm 65%. After the pre-processing operation, the grade of SiO2 is increased to 86.36%, the Fe2O 3 is reduced to 0.49%, and the AL2O 3 is reduced to 6.79%. There is a significant purification effect.
Scrubbing process is referring to removing the thin iron layer, conglomeration, and muddy impurity minerals on the surface of the quartz sand by mechanical force and abrasive stripping force between the sand particles. The scrubbed quartz sand is further classified to achieve further purification.
The magnetic separation process can remove weak magnetic impurities such as hematite, limonite and biotite. Strong magnetic separation usually uses a wet magnetic separator or a high gradient magnetic separator.
In general, quartz sand with impurities such as limonite, hematite, biotite and other weak magnetic impurity minerals can be selected by using a wet magnetic machine above 10,000 Oersted; For the main ferromagnetic minerals, it is better to use the weak magnetic machine or the medium magnetic machine.
The finer the grain size of the quartz sand, the better the iron removal effect.
Considering the serious environmental impact of fluoride wastewater, the “fluorine-free acid floatation method” appeared in foreign countries in the 1970s.
For example, in Japan, in the separation of feldspar and quartz, the use of sulfuric acid or hydrochloric acid (PH = 2) to adjust the slurry, plus the addition of higher aliphatic amine salt and sodium petroleum sulfonate mixed collector was successful.
“Fluorine-free and acid-free flotation method” is a new process for flotation separation of quartz feldspar which has been vigorously developed in recent years. This method is based on the difference in the composition of quartz and feldspar in natural neutral medium, and rationally blends the anion-cation collector, priority flotation of feldspar, to achieve the separation of the two minerals.
However, the “Fluorine-free and acid-free flotation method” is not as mature as the HF method and the acid method, the similar isoelectric point of mica and quartz increase the sorting difficulty.
In general, after scrubbing, desliming, magnetic separation and flotation, the purity of quartz sand can reach 99.3%-99.9%, which basically meets the demand of industrial sand.
Acid leaching is the use of quartz insoluble in acid (except HF), other impurity minerals can be dissolved by acid, further purification of quartz.
Acids commonly used for acid leaching include sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid; and reducing agents include sulfurous acid and salts thereof. It has been found that the above acids have good removal effects on non-metallic impurity minerals in quartz. It is generally believed that various dilute acids have significant effects on the removal of Fe and Al, while the removal of Ti and Cr is needed more concentrated sulfuric acid, aqua regia or HF.
When the mixed acid of the above acid composition is used for the acid leaching of the impurity mineral, the HF concentration is generally not more than 10% in consideration of the dissolution of HF on the quartz.
In addition to the acid concentration, the amount of acid, acid leaching time, temperature and slurry agitation can affect the effect of quartz acid leaching.
The control of various factors of acid leaching should be based on the final grade of quartz, minimize the acid concentration, temperature, and dosage, and reduce the acid leaching time to achieve quartz purification at lower beneficiation costs.
In some European and American countries, due to the strict requirements for iron in quartz, the quartz acid leaching purification treatment was systematically studied, and the acid leaching quartz beneficiation and purification plant was established. The high-purity quartz sand having a purity of 99.99% can be obtained by the quartz sand after the acid leaching treatment.
Thin-film iron or leaching iron on the surface of quartz sand particles by microorganisms is a newly developed iron removal technology. According to foreign research results, it is indicated that aflatoxin, penicillium, pseudomonas, polymyxin, Microorganisms such as bacilli have achieved good results when leaching iron on the surface of the quartz. Among them, the effect of leaching iron with leptomycin is the best, and the removal rate of Fe2O3 is more than 75%, the concentrate has a low grade of 0. 007%.
Moreover, it has been found that the leaching of iron with a pre-cultivated culture solution of most bacteria and molds is better, just like other strains due to their soluble metabolites.
At present, microbial iron removal is in the laboratory research stage, and the production of the large-scale industry still needs further experimental research.