Method for preparing polyferric aluminum chloride

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a method for preparing polyferric aluminum chloride, which comprises the following steps: S1, stirring and dissolving dust collecting slag, waste hydrochloric acid and water, and filtering and separating to obtain first filter residue and first filtrate; s2, adding waste alkali liquor into the first filtrate, carrying out neutralization reaction to obtain first mixed liquor, and filtering the first mixed liquor to obtain second filter residues and second filtrate; s3, washing the second filter residue, adding waste hydrochloric acid to obtain an acid leaching solution, concentrating the acid leaching solution to obtain a second mixed solution, and filtering and separating the second mixed solution to obtain a third filter residue and a third filtrate; s4, calcium oxide is added into the third filtrate, a prepared ferric aluminum chloride solution is obtained, the prepared ferric aluminum chloride solution is subjected to a polymerization reaction, and polyferric chloride is prepared. The method is economical and environmentally friendly, and the comprehensive utilization rate of resources can be increased.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and specifically relates to a method for preparing polyferric aluminum chloride. Background Technology

[0002] In the metallurgical industry, titanium tetrachloride production mainly relies on molten salt chlorination and fluidized bed chlorination. Both methods generate large amounts of slag during production, which contains a high proportion of soluble salts such as FeCl3, AlCl3, and NaCl. According to relevant environmental standards, the soluble salt content of this slag should not exceed 2% for landfill, but in practice, the soluble salt content of the slag is close to 80%, thus requiring resource recovery. Current treatment methods include dissolving the slag in waste hydrochloric acid, then adding waste alkali to precipitate and separate metals such as Al and Fe, and finally preparing polyaluminum ferric chloride (PAFC) as a water purification agent through non-hydrochloric acid dissolution. However, existing technologies suffer from high costs, low resource utilization, and environmental pollution when treating the slag.

[0003] Existing technologies for treating titanium dioxide slag typically employ wet processing. For example, patent CN114377860B, "Method and Process for Resource Utilization of Titanium Dioxide Slag from Chlorination Process," describes a wet leaching process for the slag. First, the soluble metal salts in the slag are dissolved. The remaining insoluble portion is pulped, and a flotation agent is added to select titanium-containing minerals for use in electric furnace smelting to produce titanium slag. The preparation method includes: sequentially pulping, solid-liquid separation, and washing the slag to obtain titanium-containing slag and a first filtrate; neutralizing the first filtrate with sodium hydroxide solution to pH 7-9; then pressure filtration and washing to obtain a second filtrate and filter cake; adding a metal precipitant to the second filtrate to precipitate heavy metal ions. However, patent CN114377860B does not provide any guidance on how to further utilize the precipitated heavy metal ions to prepare polyferric aluminum chloride (PAC) as a water purification agent.

[0004] Other existing methods for producing polyferric aluminum chloride do not provide insights into how to further utilize the dust collection residue. For example, patent document CN1463929A discloses a method for producing polyaluminum ferric chloride using a composite coagulant. This technology mainly involves adding aluminum- and iron-containing raw materials to industrial hydrochloric acid, followed by acid dissolution, chlorate oxidation, neutralization with calcium aluminate powder, and polymerization. This technology uses a large amount of industrial hydrochloric acid and does not provide insights into adding different calcium oxides to polymerize and prepare polyferric aluminum chloride (PAFC), controlling pH and reaction temperature, and ultimately preparing polyferric aluminum chloride solutions with different basicities.

[0005] In summary, existing resource utilization methods still have room for further utilization of valuable metals and other useful components in recycled slag, avoiding resource waste. Therefore, developing an efficient and environmentally friendly dust and slag treatment technology to maximize resource recovery and minimize environmental pollution, thereby improving overall economic benefits and environmental sustainability, is of great significance and has promising application prospects. Summary of the Invention

[0006] In view of this, in order to solve the problem of further utilizing the dust collection residue in the existing technology, the present invention provides a method for preparing polyferric aluminum chloride water purification agent. This method utilizes the dust collection residue, tail gas absorption waste hydrochloric acid and waste alkaline solution, and prepares high-quality polyferric aluminum chloride water purification agent through dissolution, precipitation, washing, evaporation crystallization and polymerization reaction. It is economical and environmentally friendly, and saves the preparation cost of polyferric aluminum chloride.

[0007] The technical solution adopted in this invention is as follows: This invention provides a method for preparing polyferric aluminum chloride, comprising the following steps: S1. Dust collection residue, waste hydrochloric acid and water are stirred and dissolved, and then filtered to separate the first filter residue and the first filtrate. S2. Add waste alkali solution to the first filtrate to undergo a neutralization reaction and obtain a first mixture. Filter the first mixture to obtain a second filter residue and a second filtrate. S3. Wash the second filter residue and add waste hydrochloric acid to obtain an acid leaching solution. Concentrate the acid leaching solution to obtain a second mixture. Filter to separate the second mixture and obtain a third filter residue and a third filtrate. S4. Take the third filtrate and add calcium oxide to obtain a solution for preparing ferric aluminum chloride. Wait for the solution to undergo a polymerization reaction to prepare polymerized ferric aluminum chloride.

[0008] In some embodiments, in step S1, the mass ratio of dust collection residue, waste hydrochloric acid, and water is 1:0.6~1.5:1.0~2.0.

[0009] In some embodiments, during step S2, waste alkali solution is added to adjust the pH to 4.0-5.5, and the neutralization reaction is carried out at room temperature for 0.5-24 hours.

[0010] In some embodiments, in step S3, the mass percentage of hydrochloric acid added is ≥0.96% of the mass percentage of the acid leaching solution in step S3.

[0011] In some embodiments, the concentrated acid leaching solution is an evaporative crystallization acid leaching solution, which is evaporated and crystallized until its mass is reduced to 30% to 60% of the original acid leaching solution to obtain a slurry containing metatitanic acid, while ensuring that the total mass of Fe2O3 and Al2O3 in the slurry accounts for >10% of the slurry mass.

[0012] In some embodiments, in step S4, calcium oxide is added to make the concentration of calcium oxide in the prepared ferric aluminum chloride solution 0~24 g·L. -1 .

[0013] In some embodiments, in step S4, the polymerization reaction temperature is 20~60°C and the reaction time is 30~120 min.

[0014] In some embodiments, in S1 and S3, the mass percentage of HCl in the waste hydrochloric acid is 18-35%.

[0015] In some embodiments, the pH of the waste alkaline solution in S2 is 9-10.

[0016] In some embodiments, the dust collected in S1 includes the following elements, with each element having a mass percentage (%): Na: 4~5, TFe: 10~18, Al: 3~10, Mn: 0.1~0.5, Mg: 0.8~1.2, TiO2: 20~22, Cl: 30~45, Ca: ≤0.5, SiO2: 1~2, C: 3.5~15, with the balance being impurities.

[0017] The beneficial effects of this invention include at least the following: This invention utilizes waste hydrochloric acid, waste alkaline solution, and dust collection residue to prepare a high-quality water purification agent, polyferric aluminum chloride (PAFC). Waste hydrochloric acid is used to dissolve and collect metal ions (such as iron and aluminum ions) in the dust collection residue. Then, waste alkaline solution is added to the filtrate, which precipitates iron and aluminum ions, further removing other soluble metal ions with significant impurity removal. Waste hydrochloric acid is then added again to dissolve the precipitated iron hydroxide and aluminum hydroxide, which serve as raw materials for preparing the polyferric aluminum chloride solution. Calcium oxide is then added to the raw materials to rapidly adjust the pH of the raw materials for preparing the polyferric aluminum chloride solution, causing a polymerization reaction to produce polyferric aluminum chloride. The method of this invention has significant impurity removal effects, high utilization rate of industrial waste, turning waste into treasure, and generating economically valuable polyferric aluminum chloride. It can save production costs while properly treating industrial waste, thus possessing significant economic value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for preparing polyferric aluminum chloride according to some embodiments of the present invention; Figure 2This is a flowchart illustrating a method for preparing polyferric aluminum chloride according to some embodiments of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] In this invention, "pulping and washing" refers to suspending a solid product containing impurities in a suitable solvent, utilizing the difference in solubility between the product and impurities in the solvent, and removing the impurities through stirring and washing steps. This process may include heated pulping, room temperature pulping, or low temperature pulping, and may be carried out using a single solvent or a mixture of solvents. It is important to carefully select a suitable solvent and control the appropriate temperature to ensure effective removal of impurities without loss of the target product.

[0023] In this invention, "dust collection residue" refers to molten salt chlorination dust collection residue in industrial production, "waste hydrochloric acid" refers to waste hydrochloric acid from chlorination tail gas, mainly the chlorination tail gas absorption liquid in industrial production, specifically the water washing tail gas absorption liquid, the main component of which is waste hydrochloric acid with a mass fraction of 18-35%, and "waste alkaline liquid" refers to alkaline washing absorption liquid in industrial production, which has a certain alkalinity.

[0024] In this invention, the reduction in mass by 30% to 60% means that the mass is reduced to 30% to 60% of the original mass.

[0025] like Figure 1 As shown, the present invention provides a method for preparing polyferric aluminum chloride, comprising the following steps: S1. Dust collection residue, waste hydrochloric acid and water are stirred and dissolved, and then filtered to separate the first filter residue and the first filtrate. S2. Add waste alkali solution to the first filtrate to undergo a neutralization reaction and obtain a first mixture. Filter the first mixture to obtain a second filter residue and a second filtrate. S3. Wash the second filter residue and add waste hydrochloric acid to obtain an acid leaching solution. Concentrate the acid leaching solution to obtain a second mixture. Filter to separate the second mixture and obtain a third filter residue and a third filtrate. S4. Take the third filtrate and add calcium oxide to obtain a solution for preparing ferric aluminum chloride. Wait for the solution to undergo a polymerization reaction to prepare polymerized ferric aluminum chloride.

[0026] This invention utilizes waste hydrochloric acid, waste alkali solution, and dust collection residue to prepare high-quality polyferric aluminum chloride (PAFC) water purification agent. Waste hydrochloric acid is used to dissolve and collect metal ions (such as iron and aluminum ions) in the dust collection residue. Waste alkali solution is then added to the filtrate to precipitate iron and aluminum ions, further removing other soluble metal ions with significant impurity removal. Waste hydrochloric acid is then added again to dissolve the precipitated iron hydroxide and aluminum hydroxide, which serve as raw materials for preparing the polyferric aluminum chloride solution. Calcium oxide is then added to the raw materials to rapidly adjust the pH of the raw materials for preparing the polyferric aluminum chloride solution, inducing a polymerization reaction to produce polyferric aluminum chloride. This method of the present invention has significant impurity removal effects, high utilization rate of industrial waste, and transforms waste into valuable resources, generating economically valuable polyferric aluminum chloride. It saves production costs while properly treating industrial waste, thus possessing significant economic value.

[0027] Considering both overall cost and the complete dissolution of iron and aluminum in the dust collector residue, in some embodiments, the mass ratio of dust collector residue, waste hydrochloric acid, and water in step S1 is 1:0.6~1.5:1.0~2.0. This ratio can improve filtration performance, maximizing the dissolution of iron and aluminum in the dust collector residue while minimizing cost, and preventing the introduction of other impurities.

[0028] In this invention, the pH range adjusted by adding waste alkali solution is crucial for further impurity removal. In some embodiments, during step S2, waste alkali solution is added to adjust the pH to 4.0~5.5 (including but not limited to 4.0, 4.5, 5.0, and 5.5), and the neutralization reaction is carried out at room temperature for 0.5~24 hours. Fe precipitation occurs at around 3.8, Al precipitation at around 3.5~4.0, but Mn, Ca, and Mg will precipitate after the pH exceeds 5.5.

[0029] In some embodiments, in step S3, the mass percentage of hydrochloric acid added is ≥0.96% of the mass percentage of the acid leaching solution in step S3. The purpose of this is to further ensure that the Fe and Al elements in the second filter residue are completely dissolved, in preparation for the next step of concentrating the acid leaching solution.

[0030] In some embodiments, the concentrated acid leaching solution is an evaporative crystallization acid leaching solution. The acid leaching solution is evaporated and crystallized until its mass is reduced to 30%~60% (including but not limited to 30%, 40%, 50% or 60%) to obtain a slurry containing metatitanic acid. At the same time, the concentrated acid leaching solution ensures that the total mass of Fe2O3 and Al2O3 in the slurry accounts for >10% of the slurry mass. After testing, the indicators of each ion in the third filtrate meet the following requirements: Zn<1000ppm, As<5ppm, Pb<20ppm, Hg≤0.5ppm, Cd<10ppm, Cr<50ppm. At this time, the concentrated acid leaching solution can ensure the preparation of polyferric aluminum chloride in the next step.

[0031] In some embodiments, in step S4, calcium oxide is added to make the concentration of calcium oxide in the prepared ferric aluminum chloride solution 0~24 g·L. -1 Compared to other substances such as calcium aluminate, the addition of calcium oxide as a strong alkaline substance in this invention can rapidly neutralize the acidic environment of the prepared ferric aluminum chloride solution, providing suitable conditions for the polymerization reaction, quickly controlling the rate and direction of the polymerization reaction, and reducing costs.

[0032] For the polymerization reaction to occur more effectively, the control of the reaction time and temperature is also very important. In some embodiments, in step S4, the reaction temperature of the polymerization reaction is 20~60°C, and the reaction time is 30~120 min.

[0033] In some embodiments, in S1 and S3, the mass percentage of HCl in the waste hydrochloric acid is 18-35%.

[0034] In some embodiments, the pH of the waste alkaline solution in S2 is 9-10.

[0035] In some embodiments, the dust collected in S1 includes the following elements, with each element having a mass percentage (%): Na: 4~5, TFe: 10~18, Al: 3~10, Mn: 0.1~0.5, Mg: 0.8~1.2, TiO2: 20~22, Cl: 30~45, Ca: ≤0.5, SiO2: 1~2, C: 3.5~15, with the balance being impurities.

[0036] The method of the present invention not only utilizes waste hydrochloric acid, waste alkali solution, and dust collection residue to prepare high-quality polyferric aluminum chloride (PAFC) water purification agent, but also recovers other industrially valuable products during the preparation of polyferric aluminum chloride (PAFC). For example, in some embodiments, it also includes adding 1 to 4 times the volume of water to the first filter residue in S1 for washing and drying to obtain filter residue containing TiO2, C, and a small amount of SiO2. The aforementioned filter residue can be directly returned to the molten salt chlorination furnace as raw material.

[0037] In addition, in some embodiments, the second filtrate in S2 can also further recover NaCl. The second filtrate includes NaCl, MgCl2, CaCl2, and MnCl2. The pH of the second filtrate is adjusted to 7-9. At this time, other metal ions in the second filtrate, such as Mg, will precipitate out in the form of Mg(OH)2, etc. The remaining NaCl can be used as a raw material brine for chlor-alkali.

[0038] In some embodiments, the pH of the second filtrate is adjusted to 7.5 to remove MgCl2, CaCl2 and MnCl2 from the second filtrate.

[0039] Meanwhile, metatitanic acid in the dust collection residue can also be further recovered. In some embodiments, when the third filter residue in S3 contains more than 95% metatitanic acid, the third filter residue can be returned to the molten salt furnace for chlorination, thereby further recycling the dust collection residue.

[0040] In summary, the flowchart of the method for preparing polyferric aluminum chloride provided by some more detailed embodiments of the present invention is as follows: Figure 2 As shown.

[0041] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are based on techniques or conditions described in the literature in the field.

[0042] Example 1 The composition of molten salt dust collection residue is shown in Table 1; the composition of waste hydrochloric acid from molten salt chlorination tail gas washing absorption is shown in Table 2; and the composition of waste alkaline solution from molten salt chlorination tail gas alkaline washing absorption is shown in Table 3. S1: S1-1. Take 1000g of molten salt dust collection residue, add 600g of chlorinated tail gas water washing and absorption waste hydrochloric acid, then add 1400g of water and stir to dissolve for 30min. Filter to separate and obtain the first filter residue and the first filtrate. S1-2. The first filter residue is washed three times with twice the amount of water to remove soluble metal chlorides. The composition of the dried first filter residue is shown in Table 4. The content of TiO2 is 60.57%, the content of C is 27.17%, and the content of SiO2 is 4.60%. It can be directly used as raw material in the molten salt chlorination furnace.

[0043] S2. Take the filtrate obtained in step S1-1 and use chlorination tail gas to wash and absorb the waste alkaline liquid to adjust the pH of the filtrate to 5.0. Stir the reaction at room temperature for 4 hours to obtain a precipitate solution of iron hydroxide and aluminum hydroxide (to obtain the second filter residue and the second filtrate).

[0044] S3: S3-1, the precipitate solution from step S2 is filtered and separated (i.e., the second filter cake and the second filtrate are filtered and separated), yielding a filter cake of ferric hydroxide and aluminum hydroxide (the second filter cake) and a mixed solution of NaCl, MgCl2, CaCl2, and MnCl2 (the second filtrate). Waste alkali solution can be added to the second filtrate to adjust the pH to 7.5, the purpose of which is to precipitate the Mg. 2+ Ca 2+ Mn 2+ NaCl brine prepared from the second filtrate is obtained. This brine can be used as a raw material brine for chlor-alkali production. The chemical properties of the second filtrate are shown in Table 5.

[0045] S3-2. Wash and desalinate the second filter residue after filtration in S3-1 with 4 times the amount of water, then add waste hydrochloric acid to dissolve it, and obtain an acid leaching solution with an acid addition coefficient of 0.96%. Evaporate and crystallize. After evaporating about 40% of the solution by mass of water, a second mixture is obtained. Filter and separate the second mixture to obtain a third filter residue and a third filtrate (at this time, the third filtrate contains FeCl2 and AlCl3). The third filter residue contains metatitanic acid. After filtration and separation, the filter cake base of the third filter residue contains more than 95% metatitanic acid and can be returned to the molten salt furnace for chlorination. The composition of the second mixture is shown in Table 6.

[0046] S4. Take the third filtrate from step S3-2 and add it to polymerize with different calcium oxides to prepare polyferric aluminum chloride (PAFC). Control the reaction temperature at 30℃ and maintain the reaction time at 60 min. Finally, polyferric aluminum chloride solutions with different basicities are prepared. The analysis results of the polyferric aluminum chloride solutions are shown in Table 7.

[0047] Table 1. Composition of collected dust (mass percentage %)

[0048] Table 2 Composition of waste hydrochloric acid (g / L)

[0049] Table 3 Composition of waste alkaline solution

[0050] Table 4. Composition of leaching filter residue from dust collection (mass percentage %)

[0051] Table 5 Chemical composition of purified brine (second filtrate)

[0052] Table 6. Composition (g / L) of ferric aluminum chloride solution prepared from waste hydrochloric acid (third filtrate)

[0053] Table 7 Results of the polymerization test of aluminum ferric chloride solution (Analysis results of the polymerized aluminum ferric chloride solution)

[0054] Example 2 The steps are the same as in Example 1, except that the composition (mass percentage%) of the collected dust is different, as shown in Table 8: Table 8. Composition of collected dust (mass percentage %)

[0055] Example 3 The steps are the same as in Example 1, except that the composition (mass percentage) of the collected dust is different, as shown in Table 9: Table 9. Composition of collected dust (mass percentage)

[0056] in conclusion As shown in Table 6, taking Example 1 as an example, the polyferric aluminum chloride prepared by the method of the present invention has a filtrate (i.e., the third filtrate) that meets the value specified in the standard "HGT 4672-2014 Water Treatment Agent Polyferric Chloride" and can be used to prepare PAFC. As shown in Table 7, it can be found that polyferric aluminum chloride with different basicity / % can be obtained by controlling the amount of CaO added, and can be adjusted as needed.

[0057] Furthermore, the filtrates (i.e., the third filtrate) of the polyferric aluminum chloride prepared in Examples 2 and 3 also met the values ​​specified in the standard "HGT 4672-2014 Water Treatment Agents Polyferric Chloride", and can be used to prepare PAFC. In addition, practical application shows that the polyferric aluminum chloride prepared by the method of this invention has good performance and is suitable for the treatment of weakly alkaline wastewater, achieving a suspended solids (SS) removal rate of over 99%. This method can save production costs while effectively treating industrial waste, and has significant economic value.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing polyaluminium ferric chloride, characterized in that: The following steps are involved: S1, dust collection residue, waste hydrochloric acid and water are stirred and dissolved, and filtered and separated to obtain a first filter residue and a first filtrate; S2, adding waste alkali solution to the first filtrate to cause a neutralization reaction to obtain a first mixed solution, and filtering the first mixed solution to obtain a second filter residue and a second filtrate; S3, washing the second filter residue and adding waste hydrochloric acid to obtain an acid leaching solution, concentrating the acid leaching solution to obtain a second mixed solution, filtering and separating the second mixed solution to obtain a third filter residue and a third filtrate; S4, taking the third filtrate and adding calcium oxide to obtain a ferric aluminum chloride solution, and subjecting the ferric aluminum chloride solution to polymerization reaction to prepare polyferric aluminum chloride.

2. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In S1, the mass ratio of dust collection residue, waste hydrochloric acid and water is 1:0.6~1.5:1.0~2.

0.

3. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In the S2, waste alkali solution is added to adjust the pH to 4.0-5.5, and the neutralization reaction is carried out at room temperature for 0.5-24 hours.

4. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In S3, it is ensured that the mass percentage of the added hydrochloric acid in the acid leaching solution in S3 is ≥ 0.96%.

5. The method for preparing polyaluminium ferric chloride according to claim 4, characterized in that: The concentrated acid leaching solution is an evaporative crystallization acid leaching solution, and the acid leaching solution is evaporated and crystallized until the mass is reduced by 30% to 60% to obtain a slurry containing titanic acid, while ensuring that the total mass of Fe2O3 and Al2O3 in the slurry accounts for >10% of the mass of the slurry.

6. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In S4, calcium oxide is added to make the concentration of calcium oxide in the ferric aluminum chloride solution prepared to be 0-24 / g·L -1 .

7. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In S4, the polymerization reaction has a reaction temperature of 20-60° C. and a reaction time of 30-120 min.

8. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: In S1 and S3, the mass percentage of HCl in the waste hydrochloric acid is 18-35%.

9. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: The pH of the waste alkali solution in S2 is 9-10.

10. The method for preparing polyaluminium ferric chloride according to claim 1, characterized in that: The dust collected in S1 includes the following elements, and the mass percentage of each element is (%): Na: 4~5, TFe: 10~18, Al: 3~10, Mn: 0.1~0.5, Mg: 0.8~1.2, TiO2: 20~22, Cl: 30~45, Ca: ≤0.5, SiO2: 1~2, C: 3.5~15, and the remainder is impurities.

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