Summary:The ore properties of different quartz raw materials are quite different, and the purification potential is affected by the chemical composition of the ore, the
The ore properties of different quartz raw materials are quite different, and the purification potential is affected by the chemical composition of the ore, the characteristics of embedded particle size, gangue minerals, inclusions, and lattice impurities. The processing of high-purity quartz products has the characteristics of great influence on the properties of raw ore, high purity of products and easy pollution.
The purification methods of high-purity quartz are mainly divided into physical methods and chemical methods. Different associated minerals adopt different sorting techniques. Physical purification mainly includes color separation, scrubbing, gravity separation, magnetic separation and flotation, which can remove almost all mineral impurities existing in monomers. content is at a low level. At this time, gas-liquid inclusions and isomorphous impurities inside the crystal lattice are the main sources of impurities, and these impurities are the key factors restricting the preparation of high-purity quartz products. Physical purification cannot remove these impurities, and chemical purification is required.
Chemical deep purification mainly includes acid (alkali, salt) treatment and heat treatment. Acid (alkali, salt) treatment mainly removes impurities that exist on the surface of quartz sand particles or embedded in particles in the form of inclusions. Heat treatment mainly uses high temperature to remove impurities. Similar impurities in inclusions or crystal lattices. Compared with physical purification methods, chemical purification operations are complex and costly, but chemical treatment is the most effective and essential when preparing high-purity quartz.
1. Acid Treatment
After the initial physical purification, most of the impurity minerals have been removed, but there are still a small amount of impurity minerals in the grain boundaries, micro-cracks and crystals. The acid (alkali, salt) treatment is mainly to remove these impurities. Among them, the acid leaching method is the most widely used, and the mixed solution of hydrofluoric acid, sulfuric acid, hydrochloric acid and nitric acid is often used to purify quartz sand.
Hydrofluoric acid has obvious corrosion effect on quartz, feldspar, mica, etc., and the more structural defects, the faster the dissolution rate. The crystal structure of muscovite, feldspar and other aluminosilicates must be combined with hydrofluoric acid to be effective. destroy.
Concentrated sulfuric acid has strong oxidizing properties, hot concentrated sulfuric acid can react with most metals, and convert most sulfide minerals into corresponding high-valent metal sulfates, which have a higher boiling point, and higher leaching temperatures can be used under normal pressure. Hydrochloric acid has good metal dissolving ability and good complexing ability to iron ions.
Nitric acid has strong oxidizing properties and can effectively oxidize metal elements to form soluble salts, but its leaching effect alone is not good, and it is generally mixed with hydrochloric acid to prepare highly corrosive aqua regia for leaching. Oxalic acid is an organic acid commonly used in pickling, which can form a relatively stable complex with the dissolved metal ions, thereby detaching them from the quartz surface.
(1) With Fluorine Leaching
A large number of tests have shown that single acid leaching is not effective in removing impurities from high-purity quartz, while mixed acid leaching can take advantage of the synergistic effect of different acids to effectively remove impurities. Nowadays, mixed acid leaching with hydrofluoric acid as the main leaching agent acid is the most widely used, and there are many related researches in this area. Researchers showed that the removal effect of HCl-H2C2O4-HF mixed acid on Fe is better than that of H2SO4-H2C2O4-HF mixed acid, and can effectively avoid the pollution of sulfur to quartz concentrate.
(2) Fluorine-free Leaching
As the country pays more and more attention to environmental protection, the fluorine-free and nitrate-free process in mixed acid leaching of high-purity quartz will be particularly important in future industrial practice. At this stage, the industry still uses HF-based acid leaching process, and the fluorine-free and nitrate-free process is only in the laboratory research stage, but it has achieved certain results, laying the foundation for the implementation of environmentally friendly production processes in the future.
2. Heat Treatment Method
(1) High Temperature Burst Method
The direct high-temperature burst method uses high-temperature roasting and microwave heating to create crystal defects and high-energy regions on the surface of quartz crystals, and gasifies and expands gas-liquid inclusions, and then uses water quenching to burst the expanded gas-liquid inclusions instantaneously. Between the mineral inclusions in the quartz crystal and the quartz crystal interface, due to the difference in thermal properties between the silicon-oxygen bond Si-O and the metal-oxygen bond Me-O at the interface, stress concentration will occur at the interface when heated, and the metal-oxygen bond M-O is easy to break and Surface water evaporates, forming shrinkage cracks at the interface. The cracks on the surface of quartz crystals, that is, crystal defects, are areas of excess energy and are characterized by high chemical activity, creating opportunities for improving chemical leaching efficiency. At the same time, some volatile impurities and flotation agents remaining in the concentrate can be removed through the high-temperature roasting process.
(2) Hydrogen Combustion Method
The method of burning off the interstitial space of quartz lattice, alkali metal, etc., the main method of chlorination roasting, chlorination roasting, roasting and roasting is in At a certain temperature and conditions, the components are separated. Chlorinating agents include chlorine, hydrogen chloride, and and so on, chlorination, roasting, chlorination, calcium chloride, etc. Calcium chloride, calcium chloride, calcium chloride, chlorination, roasting, and roasting can be divided into high temperature according to the product form. High-temperature roasting, electrolytic combustion-leaching method), electrolysis-separation. There are great differences in the way and effect that different electrolytes and combustion temperatures interact with crystal impurities.
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