Quartz sand, also known as silica sand, is a common non-metallic mineral raw materials, its wide range of applications. China's quartz sand beneficiation purification and deep processing development and utilization is relatively late, and is mainly used in the construction industry, glass manufacturing, ceramic industry and foundry industry. One common point in these fields is the large demand for quartz sand and low quality of raw materials. For high-quality quartz sand from some producing areas in China, it can basically meet the demand of industrial sand without undergoing beneficiation or purification. At present, the foreign country's quartz sand beneficiation and purification technology is the most advanced, characterized by large industrial output, professional equipment and high degree of production automation. Its products have been developed to the sixth generation. High-purity and ultra-high-purity quartz sand made by beneficiation and purification has 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 technique to remove small or trace impurities in quartz sand to obtain refined quartz sand or high-purity quartz sand (such as electronic grade products). In recent years, the purification process of quartz sand at home and abroad mainly revolves around the following aspects. get on. 1, washing, grading de-sludge Quartz sand as an SiO2 grade quartz sand of taper decreases, iron mineral impurities and the like made of aluminum and the quality grade is the opposite, a phenomenon in nature contains a large amount of clay mineral quartz sand is particularly evident. Therefore, before the selection, the quartz sand ore is water-selected, and the de-sludge is very necessary, and the effect is more obvious. For example, the chemical composition of quartz sand ore in the Malingshan Mine in Suqian, Jiangsu Province is: SiO279.38%, Fe2O31.68%, Al2O311.28%, and its particle size composition is -0.1mm. After pre-selected water washing and fractional de-sludge of the ore, the grade of SiO2 increased to 86.36%, Fe2O3 decreased to 0.49%, and Al2O3 decreased to 6.79%. The effect of impurity removal was more significant. Washing and grading de-sludge as a pre-treatment method before ore is selected, and it is also very common in application. However, the removal effect of thin-film iron and blocking impurity minerals existing on the surface of quartz sand is not significant. 2, scrub Scrubbing is to remove the thin film iron, the bonding and muddy impurity minerals on the surface of the quartz sand by mechanical force and the grinding and peeling force between the sand grains, and to further smash the unassembled mineral aggregates, and then further purify the quartz sand by the classification operation. At present, there are two main methods: bar friction washing and mechanical scrubbing. For mechanical scrubbing, it is generally believed that the factors affecting the scrubbing effect are mainly from the structural features and configuration forms of the scrubber, followed by process factors, including scrubbing time and scrubbing concentration. The research shows that the scrub concentration of sand mine is the best between 50% and 60%, and to a certain extent, it increases the difficulty of purifying quartz sand. In principle, the scrubbing time should be based on the initial product quality requirements. Long, because of the long time, will increase equipment wear, increase energy consumption and increase the cost of purification. Because for some quartz sand mines, mechanical scrubbing and erasing effect is not ideal, therefore, it is more common and mature in China's rod scrubbing industry. 3, magnetic separation The magnetic separation process can remove the weak magnetic impurity minerals such as hematite, limonite and biotite including the continuum particles. Strong magnetic separation usually uses a wet magnetic separator or a high gradient magnetic separator. In general, quartz sand, which is mainly composed of weak magnetic impurities such as limonite, hematite and biotite, can be selected by using a wet magnetic machine at 10,000 Oersted or more; For the main ferromagnetic minerals, the weak magnetic machine pair or medium magnetic machine is better. The experimental conditions of the Seto quartz sand were studied in Japan using strong magnetic machines. The results show that the magnetic separation number and magnetic field strength are selected. The iron removal effect has an important effect. As the number of magnetic separations increases, the iron content decreases gradually, and a certain magnetic field strength can remove most of the iron. However, even after the magnetic field strength is increased a lot, the iron removal rate does not change much. In addition, the finer the grain size of the quartz sand, the better the iron removal effect, because the fine-grained quartz sand contains a high amount of iron-containing impurities. When the quartz sand raw sand contains more impurity minerals, the scrubbing, deliming and magnetic separation can not purify the quartz sand into high-purity sand, so further purification processing is needed. 4, flotation Taking into account the serious impact of fluorine-containing wastewater on the environment, in the 1970s, there was a “fluorine-free acid-free floatation methodâ€. For example, in Japan, in the separation of feldspar and quartz, sulfuric acid or hydrochloric acid (PH=2) was used to adjust the slurry. The flotation of high-grade aliphatic amine salt and sodium petroleum sulfonate mixed collector was successful. The fluorine-free acid-free flotation method is a new flotation process for quartz feldspar flotation. At present, there is no report on the application of industrial production. The mica and quartz have similar isoelectric points, and the sorting is difficult. The anion collector under acidic conditions or the anion-cation collector under alkaline conditions floats. Choose, you can get good results. In general, after scrubbing, deliming, magnetic separation and flotation, the purity of quartz sand can reach 99.3%-99.9%, which basically meets the demand of industrial sand. 5, acid soak Acid leaching is the use of quartz insoluble in acid (except HF), and other impurity minerals can be dissolved by acid, so that further purification of quartz can be achieved. Acids commonly used in acid leaching include sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid; and reducing agents include sulfurous acid and salts thereof. Experience has shown that the above acids have good removal effects on non-metallic impurity minerals in quartz, but have significant effects on different metal impurities, acid species and their concentrations. It is generally believed that the removal of Fe and Al by various dilute acids Both have significant effects, while the removal of Ti and Cr is effected by acid leaching with more concentrated sulfuric acid, aqua regia or HF. The acid leaching of impurity minerals is usually carried out using a mixed acid of the above-mentioned acid composition, and the HF concentration is generally not more than 10% in consideration of the dissolution of HF on quartz. In addition to the acid concentration, the amount of acid, acid leaching time, temperature and ore agitation can affect the acid leaching effect of quartz. The control of various factors of acid leaching should be based on the final grade requirements of quartz, to minimize the acid concentration, temperature and dosage, and reduce the acid leaching time to achieve quartz purification at a lower beneficiation cost. In some European and American countries, due to the strict requirements on iron in quartz, the quartz acid leaching purification treatment was studied systematically, and the acid leaching quartz beneficiation and purification plant was established. After the acid leaching of quartz sand, high-purity quartz sand with a purity of 99.99% can be obtained. 6, microbial leaching The thinning iron or dip-dyed 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 quartz. Among them, the effect of leaching iron with cetomycin is the best, the removal rate of Fe2O3 is more than 75%, and the grade of concentrate Fe2O3 is low. 0.007%. At present, microbial iron removal is in the laboratory research stage, and the production of large-scale industry still needs further experimental research. summary With the advancement of science and technology, the demand for high-tech silicon will also increase greatly, and the depletion of natural crystal resources has forced people to turn their attention to the replacement of natural crystals - high purity and ultra-high purity quartz sand. Therefore, we actively explore and promote the advancement of quartz sand beneficiation and purification technology, realize the cost of refined quartz sand, high-purity and ultra-high-purity quartz sand, mass industrial production, and make up for the shortage of natural crystal resources to meet the demand for high-tech silicon. Important practical significance.
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