By trunnano | 15 July 2022 | 0 Comments
How to Purify Graphite?
The premise of graphite deep processing industry is purification, which is a complex physical and chemical process. The main purification methods include flotation, alkaline acid, hydrofluoric acid, chlorination roasting and high temperature method.
Flotation method
Flotation is a commonly used and important mineral processing method, graphite has good natural floatability, basically all graphite can be purified by flotation, in order to protect graphite flakes, graphite flotation mostly uses multi-stage process. The collector for graphite flotation is kerosene, the dosage is 100~200g/t, and the foaming agent is terpineol oil or butyl ether oil, and the dosage is 50~250g/t.
The value and application of large flake graphite is much greater than that of fine flake graphite, and once destroyed, it cannot be recovered. Protecting the large flakes of graphite in graphite mineral processing is a problem that can not be ignored in the process of mineral processing. Because graphite has good natural floatability, the grade of graphite can be raised to 80%-90% by flotation, or even up to 95%. The biggest advantage of this method is that the energy consumption and reagent consumption of all purification schemes are the lowest and the cost is the lowest. However, the silicate minerals and the compounds of potassium, calcium, sodium, magnesium and aluminum contained in the graphite flake can not dissociate the monomer by grinding, and it is not conducive to the protection of large graphite flake. Therefore, flotation is only the primary means of graphite purification, if you want to obtain high-carbon graphite with more than 99% carbon content, it must be purified by other methods.
Alkali-acid method
Alkali-acid method includes two reaction processes: alkali melting process and acid leaching process. The alkali melting process is a chemical reaction between alkali and acidic impurities in graphite under the condition of high temperature, especially the impurities containing silicon (such as silicate, aluminosilicate, quartz, etc.) to form soluble salts, and then washed to remove impurities. so that the purity of graphite can be improved. The basic principle of acid leaching process is that acid reacts with metal oxide impurities, which do not react with alkali in the process of alkali melting. The metal oxide is converted into soluble salt and then separated from graphite by washing. The combination of alkali melting and acid leaching has a good effect on the purification of graphite.
A variety of alkaline substances can remove graphite impurities, and the stronger the alkalinity is, the better the purification effect is. NaOH with low melting point and strong alkalinity is often used in alkali-acid method. The acid used in the acid leaching process can be HCl, H2SO4, HNO3 or a mixture of them, among which HCl is widely used.
For some graphite with high silicon content, the comprehensive recovery and utilization of silicon can also be realized by purifying graphite by alkali melting. After alkali melting and acid leaching, the solution is acidic, and the silicon impurities in the solution are transformed into silicic acid, which can be extracted by adding a certain amount of alum, and then calcined at 900℃ to obtain pure silica.
Alkali-acid method is the most widely used method in the industrial production of graphite purification, which has the advantages of low one-time investment, high product grade, strong adaptability, simple equipment and strong versatility. The deficiency is that it needs high temperature calcination, high energy consumption, long technological process, serious equipment corrosion, large amount of graphite loss and serious waste water pollution, so it is very important to produce polyaluminum ferric chloride from graphite purification wastewater.
Hydrofluoric acid method
Hydrofluoric acid is a strong acid, which can react with almost any impurities in graphite, and graphite has good acid resistance, especially hydrofluoric acid, which determines that graphite can be purified with hydrofluoric acid. The main process of hydrofluoric acid method is the mixture of graphite and hydrofluoric acid. Hydrofluoric acid reacts with impurities for a period of time to produce soluble matter or volatile matter. After washing and removing impurities, graphite is purified by dehydration and drying.
Hydrofluoric acid reacts with Ca, Mg, Fe and other metal oxides to form precipitation. The resulting H2SiF6 dissolves in the solution and can remove impurities such as Ca, Mg, Fe and so on. Hydrofluoric acid is highly toxic and seriously pollutes the environment. The purification of graphite with other acids can effectively reduce the amount of hydrofluoric acid. The purification of graphite by hydrofluoric acid has the advantages of simple technological process, high product grade, relatively low cost and little effect on the properties of graphite products. However, hydrofluoric acid is highly toxic, so it must have safety protection measures in the process of use, and the resulting wastewater must be treated before it can be discharged, otherwise it will cause serious pollution to the environment.
Chlorination roasting method
Chlorination roasting is a process in which graphite is mixed with a certain reductant and roasted at high temperature under specific equipment and atmosphere, and the valuable metal in the material is transformed into metal chloride in gas phase or condensed phase, which is separated from other components to purify graphite.
The impurities in graphite can be decomposed into oxides with higher melting boiling point, such as SiO2, Al2O3, Fe2O3, CaO and MgO at high temperature. When these oxides are put into chlorine at a certain high temperature and atmosphere, the metal oxides react with chlorine to form chlorides with lower melting boiling point. Therefore, at a lower temperature, these chlorides can be gasified and escape, separating from graphite and purifying graphite.
The advantages of chlorination roasting method are energy saving, high purification efficiency (> 98%) and high recovery rate, but there are also some problems such as toxic chlorine, serious corrosiveness and serious environmental pollution. In the process, the purity of graphite is limited and the process stability is not good, which affects the application of chlorination method in practical production and needs to be further improved.
High-temperature purification method
The melting point of graphite is 3850℃±50 ℃, which is one of the substances with the highest melting point in nature, which is much higher than that of impurity silicate. Making use of the difference of their melting boiling point, the graphite is placed in a graphitized graphite crucible and heated to 2700℃ with specific instruments and equipment in a certain atmosphere, the impurity gasification can escape from the graphite and achieve the effect of purification. This technology can purify graphite to more than 99.99%.
There are many factors affecting the purification of graphite by high temperature method: the impurity content of graphite raw material has the greatest influence on the purification effect of high temperature method. The ash content of the product is different when the impurity content of graphite raw material is different, and the purification effect of graphite with high carbon content is better. High temperature method usually uses graphite with 99% or more carbon content after purification by flotation or alkaline acid method as raw material. The carbon content of the graphite crucible is also an important factor affecting the purification effect, and the ash content of the crucible is lower than that of graphite, which is conducive to the escape of ash from graphite; the use of high current and rapid heating up of graphite is beneficial to the purification of graphite, it is best to use the raw material of high power electrode and treated at 2800℃; the particle size of graphite also has a certain effect on the purification effect.
The high-temperature method purifies graphite with high quality and carbon content of more than 99.995%, which is the biggest feature of the high-temperature method, but at the same time, it consumes a lot of energy, has high requirements for equipment, needs special design, and has a large investment. There are also certain requirements for purified graphite raw materials. Only graphite used in national defense, aerospace, nuclear industry and other high-tech fields is purified by this method.
High Purity Graphite Powder Price
The price is influenced by many factors including the supply and demand in the market, industry trends, economic activity, market sentiment, and unexpected events.
If you are looking for the latest high-purity graphite powder price, you can send us your inquiry for a quote. (sales3@nanotrun.com)
High Purity Graphite Powder Supplier
Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) is a trusted global chemical material supplier & manufacturer with over 12-year-experience in providing super high-quality chemicals and nanomaterials, including silicon powder, nitride powder, graphite powder, zinc sulfide, calcium nitride, 3D printing powder, etc.
If you are looking for high-quality high-purity graphite powder, please feel free to contact us and send an inquiry. (sales3@nanotrun.com)
Flotation method
Flotation is a commonly used and important mineral processing method, graphite has good natural floatability, basically all graphite can be purified by flotation, in order to protect graphite flakes, graphite flotation mostly uses multi-stage process. The collector for graphite flotation is kerosene, the dosage is 100~200g/t, and the foaming agent is terpineol oil or butyl ether oil, and the dosage is 50~250g/t.
The value and application of large flake graphite is much greater than that of fine flake graphite, and once destroyed, it cannot be recovered. Protecting the large flakes of graphite in graphite mineral processing is a problem that can not be ignored in the process of mineral processing. Because graphite has good natural floatability, the grade of graphite can be raised to 80%-90% by flotation, or even up to 95%. The biggest advantage of this method is that the energy consumption and reagent consumption of all purification schemes are the lowest and the cost is the lowest. However, the silicate minerals and the compounds of potassium, calcium, sodium, magnesium and aluminum contained in the graphite flake can not dissociate the monomer by grinding, and it is not conducive to the protection of large graphite flake. Therefore, flotation is only the primary means of graphite purification, if you want to obtain high-carbon graphite with more than 99% carbon content, it must be purified by other methods.
Alkali-acid method
Alkali-acid method includes two reaction processes: alkali melting process and acid leaching process. The alkali melting process is a chemical reaction between alkali and acidic impurities in graphite under the condition of high temperature, especially the impurities containing silicon (such as silicate, aluminosilicate, quartz, etc.) to form soluble salts, and then washed to remove impurities. so that the purity of graphite can be improved. The basic principle of acid leaching process is that acid reacts with metal oxide impurities, which do not react with alkali in the process of alkali melting. The metal oxide is converted into soluble salt and then separated from graphite by washing. The combination of alkali melting and acid leaching has a good effect on the purification of graphite.
A variety of alkaline substances can remove graphite impurities, and the stronger the alkalinity is, the better the purification effect is. NaOH with low melting point and strong alkalinity is often used in alkali-acid method. The acid used in the acid leaching process can be HCl, H2SO4, HNO3 or a mixture of them, among which HCl is widely used.
For some graphite with high silicon content, the comprehensive recovery and utilization of silicon can also be realized by purifying graphite by alkali melting. After alkali melting and acid leaching, the solution is acidic, and the silicon impurities in the solution are transformed into silicic acid, which can be extracted by adding a certain amount of alum, and then calcined at 900℃ to obtain pure silica.
Alkali-acid method is the most widely used method in the industrial production of graphite purification, which has the advantages of low one-time investment, high product grade, strong adaptability, simple equipment and strong versatility. The deficiency is that it needs high temperature calcination, high energy consumption, long technological process, serious equipment corrosion, large amount of graphite loss and serious waste water pollution, so it is very important to produce polyaluminum ferric chloride from graphite purification wastewater.
Hydrofluoric acid method
Hydrofluoric acid is a strong acid, which can react with almost any impurities in graphite, and graphite has good acid resistance, especially hydrofluoric acid, which determines that graphite can be purified with hydrofluoric acid. The main process of hydrofluoric acid method is the mixture of graphite and hydrofluoric acid. Hydrofluoric acid reacts with impurities for a period of time to produce soluble matter or volatile matter. After washing and removing impurities, graphite is purified by dehydration and drying.
Hydrofluoric acid reacts with Ca, Mg, Fe and other metal oxides to form precipitation. The resulting H2SiF6 dissolves in the solution and can remove impurities such as Ca, Mg, Fe and so on. Hydrofluoric acid is highly toxic and seriously pollutes the environment. The purification of graphite with other acids can effectively reduce the amount of hydrofluoric acid. The purification of graphite by hydrofluoric acid has the advantages of simple technological process, high product grade, relatively low cost and little effect on the properties of graphite products. However, hydrofluoric acid is highly toxic, so it must have safety protection measures in the process of use, and the resulting wastewater must be treated before it can be discharged, otherwise it will cause serious pollution to the environment.
Chlorination roasting method
Chlorination roasting is a process in which graphite is mixed with a certain reductant and roasted at high temperature under specific equipment and atmosphere, and the valuable metal in the material is transformed into metal chloride in gas phase or condensed phase, which is separated from other components to purify graphite.
The impurities in graphite can be decomposed into oxides with higher melting boiling point, such as SiO2, Al2O3, Fe2O3, CaO and MgO at high temperature. When these oxides are put into chlorine at a certain high temperature and atmosphere, the metal oxides react with chlorine to form chlorides with lower melting boiling point. Therefore, at a lower temperature, these chlorides can be gasified and escape, separating from graphite and purifying graphite.
The advantages of chlorination roasting method are energy saving, high purification efficiency (> 98%) and high recovery rate, but there are also some problems such as toxic chlorine, serious corrosiveness and serious environmental pollution. In the process, the purity of graphite is limited and the process stability is not good, which affects the application of chlorination method in practical production and needs to be further improved.
High-temperature purification method
The melting point of graphite is 3850℃±50 ℃, which is one of the substances with the highest melting point in nature, which is much higher than that of impurity silicate. Making use of the difference of their melting boiling point, the graphite is placed in a graphitized graphite crucible and heated to 2700℃ with specific instruments and equipment in a certain atmosphere, the impurity gasification can escape from the graphite and achieve the effect of purification. This technology can purify graphite to more than 99.99%.
There are many factors affecting the purification of graphite by high temperature method: the impurity content of graphite raw material has the greatest influence on the purification effect of high temperature method. The ash content of the product is different when the impurity content of graphite raw material is different, and the purification effect of graphite with high carbon content is better. High temperature method usually uses graphite with 99% or more carbon content after purification by flotation or alkaline acid method as raw material. The carbon content of the graphite crucible is also an important factor affecting the purification effect, and the ash content of the crucible is lower than that of graphite, which is conducive to the escape of ash from graphite; the use of high current and rapid heating up of graphite is beneficial to the purification of graphite, it is best to use the raw material of high power electrode and treated at 2800℃; the particle size of graphite also has a certain effect on the purification effect.
The high-temperature method purifies graphite with high quality and carbon content of more than 99.995%, which is the biggest feature of the high-temperature method, but at the same time, it consumes a lot of energy, has high requirements for equipment, needs special design, and has a large investment. There are also certain requirements for purified graphite raw materials. Only graphite used in national defense, aerospace, nuclear industry and other high-tech fields is purified by this method.
High Purity Graphite Powder Price
The price is influenced by many factors including the supply and demand in the market, industry trends, economic activity, market sentiment, and unexpected events.
If you are looking for the latest high-purity graphite powder price, you can send us your inquiry for a quote. (sales3@nanotrun.com)
High Purity Graphite Powder Supplier
Luoyang Tongrun Nano Technology Co. Ltd. (TRUNNANO) is a trusted global chemical material supplier & manufacturer with over 12-year-experience in providing super high-quality chemicals and nanomaterials, including silicon powder, nitride powder, graphite powder, zinc sulfide, calcium nitride, 3D printing powder, etc.
If you are looking for high-quality high-purity graphite powder, please feel free to contact us and send an inquiry. (sales3@nanotrun.com)
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