CN1336327A - Process of producing high-purity magnetic iron oxide with ferous sulfate as by-product of titanium white production - Google Patents

Abstract

A method of producing high purity magnetic iron oxide using titanium white by product ferrous sulfate is characterized in that; the ferrous sulfate is dissolved, freezed, crystallized; the obtained ferrous sulfate crystal is dissolved again, using ferric sulfate hydrlysis method to purity, remove impurity and obtain refined ferrous sulfate solution, finally adding mixed solution of ammonia and ammonium bicarbonate to said ferrous sulfate solution to synthesize under certain temperature and pH to obtain ferrous sulfate precipitate with good magnetic performance. Advantages: good impurity eliminating effect, high yield, low cost, simple operation etc.

Description

Method for producing high-purity magnetic iron oxide by using ferrous sulfate as byproduct of titanium dioxide

The invention relates to a method for producing magnetic iron oxide, in particular to a method for producing high-purity magnetic iron oxide by using ferrous sulfate as a titanium white byproduct.

At present, the industrial production method of magnetic iron oxide is generally a sulfate method and a russian method, the sulfate method uses enamel iron sheet and sulfuric acid as raw materials, has high cost and good quality, and is suitable for preparing high-grade magnetic materials, the russian method is a product obtained by roasting, decomposing and oxidizing an iron chloride solution, the pickling waste liquor of a steel mill can be used as the raw materials, the cost is lower, but the grade of the product is not high, the method is only suitable for preparing medium and low grade magnetic materials, the preparation of high-purity magnetic iron oxide by using a titanium white by-product ferrous sulfate is a new way for controlling pollution and exploring a new production method of the high-purity magnetic iron oxide, related technologies have not been reported, but the operation is inconvenient due to the reasons of high cost, operation and the like, and no report of large-scale industrial production technology is found, because the titanium white by-product ferrous sulfate contains various impurities such as Ti, AL, Mg, Mn, Si and other trace elements, the technical difficulty of industrial production is that the purity and the operation of ① ferrous sulfate are difficult, the impurity content exceeds standard, the ③ drying time is long, the material needs to be crushed, CN, the CN patent discloses a method for industrial production of removing impurities by adding the titanium white ferrous sulfate, the industrial production method, the steps of reducing, the iron sheet iron sulfate, the method comprises the steps of:

① hydrolysis process produces a lot of titanium hydroxide precipitation, the clear-to-turbid ratio of the settled material isabout 2: 1, clear liquid is easy to filter, while turbid liquid is difficult to filter, if turbid liquid is discarded, yield of ferrous sulfate is too low, ② concentration in hydrolysis process is lower, clear-to-turbid ratio is higher, hydrolysis yield is high, but concentration in crystallization process is higher, yield is higher, hydrolysis and crystallization have opposite requirements on solution concentration, according to the proportion selected in the patent, crystallization yield is 25% -30%, total yield is only 20%₃Precipitation, the process has the disadvantage that ① forms Fe (OH)₃The water content of the precipitate is large, the precipitate is flocculent, difficult to filter and wash, much washing water, long washing time and large operation difficulty of industrial production, the impurity content, particularly the magnesium content in the ② product is easy to exceed the standard, ③ Fe (OH)₃The precipitation drying time is long, 3-5 hours are needed, the precipitate is in a block shape after being calcined, the crushing is needed, the production procedures are multiple, and the energy consumption is high.

The invention aims to provide a method for producing magnetic ferric oxide by using ferrous sulfate as a titanium white byproduct, wherein the yield of impurity removal steps is expected to reach more than 50%; meanwhile, the precipitate generated by synthesis is required to be easy to filter and wash, does not need to be crushed and is suitable for industrial operation. And the cost is low, and the product has excellent magnetic properties.

The principle utilized by the invention is as follows:

the method is characterized in that the solubility of ferrous sulfate in water is obviously reduced along with the reduction of temperature, and impurity elements such as titanium, magnesium, aluminum, calcium, manganese, chromium, nickel, copper, lead and the like in a ferrous sulfate saturated solution are far from reaching the saturation characteristic, the ferrous sulfate is prepared into a saturated solution (with the concentration of 60-73%) at about 60 ℃, and then the saturated solution is frozen and crystallized, so that most of impurities are left in mother liquor, after separation, the impurities in ferrous sulfate crystals are greatly reduced, and only a small amount of impurities such as titanium, aluminum, silicon and the like exist, and the impurities are removed by a ferric sulfate hydrolysis method in the prior art. Reacting the refined ferrous sulfate solution with ammonia-ammonium bicarbonate mixed solution to form a solution containing part of Fe (OH)₂FeCO of₃Precipitating, and controlling the pH value and reaction temperature at the end point of the reaction to make magnesium as MgCO impurity₃In a form such that it is removed during the washing process.

The reaction formula is as follows:

the method comprises the following specific steps:

preparing solution of ferrous sulfate as byproduct of titanium white, cooling for crystallization, separating to obtain ferrous sulfate crystal, dissolving the ferrous sulfate crystal again to obtain solution, adding sulfuric acid to adjust pH to 1.2-1.5, and adding iron sheet (or Fe)₂O₃Or Fe (OH)₂Ferrous salt, etc.) to adjust the PH value to 4.0-5.0, adding flocculating agent for sedimentation, and filtering clear liquid to obtain refined ferrous sulfate solution.

Adding prepared NH into the refined ferrous sulfate solution₃-NH₄HCO₃Mixing the solution, controlling the reaction temperature to be 45-60 ℃, anddetecting the pH value at any time, namely the reaction end point when the pH value reaches 6.5-7.0, preserving the temperature, filtering and separating the precipitate, and washing with deionized water.

And drying and calcining the obtained solid particles to obtain a finished product.

As a further improvement of the invention, the concentration of the ferrous sulfate solution as the titanium white byproduct is controlled to be 55-73%, and FeSO is generated in the hydrolysis process₄The specific gravity of the solution prepared by the crystal is 1.2-1.3.

As a further improvement of the invention, NH is synthesized in the synthesis step₃-NH₄HCO₃NH of mixed solution₃∶NH₄HCO₃The weight ratio is 1: 3-1: 6.

Because the impurity removal method adopts the process of crystallization first and hydrolysis second, ferrous sulfate can be prepared into saturated solution with high concentration, the material handling capacity in the whole production process is reduced, the energy consumption is reduced, most impurities are removed in the crystallization process, the load of acidolysis hydrolysis impurity removal is greatly reduced, the sulfuric acid and iron sheet consumption required by hydrolysis is reduced, precipitates in the hydrolysis process are greatly reduced, the hydrolysis yield is greatly improved, and the problem of concentration contradiction required by hydrolysis and crystallization is solved.

Because the synthesis method adopts an ammonia-ammonium bicarbonate precipitation method, the generated precipitate contains part of Fe (OH)₂FeCO of₃The precipitate is in a granular shape, which is beneficial to filtering the precipitate without crushing, improves the magnetic property of the precipitate, and neutralizes Fe (OH) generated by an oxidation method in the prior art₃The invention effectively avoids the defects that the flocculent precipitate is difficult to filter and wash in industrial production, the washing time is long and the washing water is much; the operation is effectively simplified, and the cost is reduced. By controlling the pH value of the reaction end point and the reaction temperature, the synthesis method can lead the impurity Mg to be MgCO₃The impurity Mg content in the finished product can reach below 100ppm compared with that in the form of Mg saltThe impurity Mg content in the prior art is obviously reduced by 1000 ppm.

The invention is further described below with reference to the accompanying drawings:

FIG. 1 is a process block diagram of the present invention;

the following examples further illustrate the invention

Example 1:

adding the 16t titanium white byproduct ferrous sulfate and water into 20m³The solution is sent to a freezing crystallization device for cooling and crystallizing when the concentration of the solution is increased to 55 percent, and the solution is centrifugally separated when the temperature of the material is reduced to 12 ℃ to obtain ferrous sulfate crystals 1 and 9.2t, wherein the impurity content ratio of the crystal 1 to the raw material is shown in Table 1.

The FeSO is added₄Preparing crystal into solution with specific gravity of 1.2, adding sulfuric acid to regulate pH value to 1.2, adding proper quantity of enamel sheet iron to make Ti react⁴⁺Conversion to Ti³⁺Then 150kgFeCO is added₃The pH value increases as the reaction proceeds, Ti³⁺Hydrolysis to more compact Ti (OH)₃↓, when PH value reaches 4.0, aluminum silicon is hydrolyzed completely, adding appropriate amount of gelatin, standing to obtain solution with the ratio of clear to turbid being 9: 1, filtering to obtain filtrate 1, and converting into FeSO₄.7H₂O8.1 ton, for synthesis, and the impurity content in the obtained filtrate 1 is shown in table 1.

Refining the above (FeSO)₄.7H₂O content of 325g/L) ferrous sulfate solution 6m³Adding into a synthesis reaction kettle, heating to 50 ℃, and adding NH with concentration₄HCO₃Is 252g/L, NH₃∶NH₄HCO₃NH 1: 3 (weight ratio)₃-NH₄HCO₃Mixing the solution with the material ratio of 1-2% of excessive ferrous sulfate, controlling the reaction temperature at 45 ℃, the reaction time at 2 hours, keeping the pH value at the end of the reaction at 6.6, preserving the temperature for 30-60 minutes after the reaction is finished, filtering, and washing with deionized water for 8 hours to obtain wet FeCO₃(ii) a Drying and calcining to obtain a finished product 1.

The comparison of the product quality and the soft magnetic ferrite iron oxide industry standard SJ/T10383-98 YHT1 index of the department of electronic industry is shown in Table 2.

Example 2:

adding the 16t titanium white byproduct ferrous sulfate and water into 20m³The solution is sent to a freezing crystallization device for cooling and crystallizing when the concentration of the solution is increased to 73 percent, and the solution is centrifugally separated when the temperature of the material is reduced to 15 ℃ to obtain 2 and 9.1tferrous sulfate crystals, wherein the impurity content ratio of the 2 crystals to the raw material is shown in Table 1.

Preparing the FeSO4 crystal into a solution with a specific gravity of 1.3, adding sulfuric acid to adjust the pH value to 1.5, adding a proper amount of enamel sheet iron to react to obtain Ti⁴⁺Conversion to Ti³⁺100kg of Fe (OH) is added₂As the reaction proceeds, the pH increases, Ti³⁺Hydrolysis to more compact Ti (OH)₃↓, when PH value reaches 4.5, aluminum silicon is hydrolyzed completely, adding appropriate amount of gelatin, standing to obtain solution with the ratio of clear to turbid being 9: 1, filtering to obtain filtrate 2, and converting into FeSO₄.7H₂O7.9 tons for synthesis, the impurity content in the obtained filtrate 2 is shown in table 1.

Refining the above (FeSO)₄.7H₂O content of 325g/L) ferrous sulfate solution 6m³Adding into a synthesis reaction kettle, heating to 50 ℃, and adding NH with concentration₄HCO₃Is 252g/L, NH₃∶NH₄HCO₃1: 5 (requantized) NH₃-NH₄HCO₃Mixing the solution with the material ratio of 1-2% of excessive ferrous sulfate, controlling the reaction temperature at 55 ℃, the reaction time at 2 hours, keeping the pH value at the end of the reaction at 7.0, preserving the temperature for 30-60 minutes after the reaction is finished, filtering, and washing with deionized water for 8 hours to obtain wet FeCO₃(ii) a Drying and calcining to obtain a finished product 2.

The comparison of the product quality and the soft magnetic ferrite iron oxide industry standard SJ/T10383-98 YHT1 index of the department of electronic industry is shown in Table 2.

Example 3:

adding the 16t titanium white byproduct ferrous sulfate and water into 20m³The solution is sent to a freezing crystallization device to be cooled and crystallized when the concentration of the solution is increased to 60 percent, and is centrifugally separated when the temperature of the material is reduced to 13 ℃ to obtain ferrous sulfate crystals of 3 and 8.9t, wherein the impurity content ratio of the crystals 3 to the raw material is shown in Table 1.

The FeSO is added₄Preparing crystal into solution with specific gravity of 1.2, adding sulfuric acid to regulate pH value to 1.3, adding proper quantity of enamel sheet iron to make Ti react⁴⁺Conversion to Ti³⁺100kg of Fe (OH) is added₂As the reaction proceeds, the pH increases, Ti³⁺Hydrolysis to more compact Ti (OH)₃↓, when PH value reaches 5.0, aluminum silicon is hydrolyzed completely, adding appropriate amount of gelatin, standing to obtain solution with the ratio of clear to turbid being 9: 1, filtering to obtain filtrate 3, and converting into FeSO₄.7H₂O7.8 tons for synthesis, the impurity content in the obtained filtrate 3 is shown in table 1.

Refining the above (FeSO)₄.7H₂O content of 325g/L) ferrous sulfate solution 6m³Adding into a synthesis reaction kettle, heating to 50 ℃, and adding NH with concentration₄HCO₃Is 252g/L, NH₃∶NH₄HCO₃NH 1: 6 (weight ratio)₃-NH₄HCO₃Mixing the solution with the material ratio of 1-2% of excessive ferrous sulfate, controlling the reaction temperature at 50 ℃, the reaction time at 2 hours, keeping the pH value at the end of the reaction at 6.6, preserving the temperature for 30-60 minutes after the reaction is finished, filtering, and washing with deionized water for 4 hours to obtain wet FeCO₃(ii) a Drying and calcining to obtain a finished product 3.

The comparison of the product quality and the soft magnetic ferrite iron oxide industry standard SJ/T10383-98 YHT1 index of the department of electronic industry is shown in Table 2.

Example 4:

adding the 16t titanium white byproduct ferrous sulfate and water into 20m³Dissolving in a dissolving pool, heating, stirring, controlling the temperature to be 45-60 ℃, sending the solution to a freezing crystallization device for cooling crystallization when the concentration of the solution is increased to 65%, and cooling the solution to crystallize when the temperature of the material is reduced toAt 13 ℃, centrifugal separation is carried out to obtain ferrous sulfate crystals 4 and 9.0t, and the impurity content ratio of the crystals 4 to the raw material is shown in table 1.

The FeSO is added₄Preparing crystal into solution with specific gravity of 1.2, adding sulfuric acid to regulate pH value to 1.3, adding proper quantity of enamel sheet iron to make Ti react⁴⁺Conversion to Ti³⁺100kg of Fe (OH) is added₂As the reaction proceeds, the pH increases, Ti³⁺Hydrolysis to more compact Ti (OH)₃↓, when PH value reaches 5.0, aluminum silicon is hydrolyzed completely, adding appropriate amount of gelatin, standing to obtain solution with the ratio of clear to turbid being 9: 1, filtering to obtain filtrate 4, and converting into FeSO₄.7H₂O7.9 tons for synthesis, the impurity content in the obtained filtrate 4 is shown in table 1.

Refining the above (FeSO)₄.7H₂O content of 325g/L) ferrous sulfate solution 6m³Adding into a synthesis reaction kettle, heating to 50 ℃, and adding NH with concentration₄HCO₃Is 252g/L, NH₃∶NH₄HCO₃NH 1: 6 (weight ratio)₃-NH₄HCO₃Mixing the solution, wherein the material ratio is that the ferrous sulfate is excessive by 1-2%, the reaction temperature is controlled at 60 ℃, the reaction time is 2 hours, the pH value at the end point of the reaction is 6.6, the temperature is kept for 30-60 minutes after the reaction is finished, filtering is carried out, and deionized water is used for washing for 8 hours to obtain wet FeCO₃(ii) a Drying and calcining to obtain a finished product 4.

The comparison of the product quality and the soft magnetic ferrite iron oxide industry standard SJ/T10383-98 YHT1 index of the department of electronic industry is shown in Table 2.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof, and therefore, the above-described embodiments of the invention are to be considered in all respects as illustrative and not restrictive: the scope of the invention is indicated by the claims, and it is within the scope of the invention to employ the impurity removal process of crystallization followed by hydrolysis and the ammonia-ammonium bicarbonate mixed solution to complete the synthesis reaction.

The attached drawing is a production process route diagram of the invention.

Watch 1

Item of impurities	TiO2	AL2O3	SiO2	CaO	MgO	Cr2O3
							Raw materials	2.1	0.04	0.07	0.02	0.85	0.03
Crystal 1	0.43	0.01	0.01	0.005	0.33	0.005
							Filtrate 1	0.03	0.005	0.003	0.005	0.33	0.005
Crystal 2	0.38	0.01	0.01	0.004	0.35	0.005
							Filtrate 2	0.003	0.008	0.006	0.004	0.35	0.005
Crystal 3	0.47	0.012	0.012	0.006	0.38	0.006
							Filtrate 3	0.003	0.005	0.006	0.006	0.38	0.006
Crystal 4	0.45	0.010	0.012	0.006	0.35	0.006
							Filtrate 4	0.003	0.006	0.006	0.006	0.35	0.006

Note: the values in the table are: weight of impurities/Fe₂O₃Weight × 100% is expressed in two units: (%)

Item	Fe2O3	SiO3	CaO	AL2O3	TiO2	SO4 2-	Na2O＋k2O	MgO
									YHT1 Standard value	≥99.2	≤0.01	≤0.014	≤0.01	≤0.01	≤0.01	≤0.02	≤0.015
Finished product 1	99.5	0.005	0.007	0.005	0.004	0.01	0.005	0.004
									Finished product 2	99.4	0.005	0.005	0.008	0.003	0.01	0.005	0.004
Finished product 3	99.5	0.005	0.005	0.008	0.004	0.01	0.005	0.03
									Finished product 4	99.4	0.005	0.006	0.007	0.004	0.01	0.005	0.07

Claims (6)

1. A method for producing high-purity magnetic ferric oxide by using a titanium dioxide byproduct ferrous sulfate comprises the steps of impurity removal, synthesis, drying, calcination and the like, and is characterized in that: the ferrous sulfate solution is cooled and crystallized to guide ferrous sulfate crystalsThen, refining ferrous sulfate crystals by using a ferric sulfate hydrolysis method; finally, the mixed solution of ammonia-ammonium bicarbonate is subjected to synthetic reaction with the refined solution to obtain the solution containing part of Fe (OH)₂FeCO of₃Precipitating; and washing, drying and calcining to obtain the high-purity magnetic iron oxide.

2. The method for producing high-purity magnetic iron oxide from ferrous sulfate as a byproduct of titanium dioxide according to claim 1, which comprises the following steps:

A. the impurity removing step comprises the following steps:

preparing a solution from a titanium white byproduct ferrous sulfate, cooling and crystallizing the solution, separating to obtain ferrous sulfate crystals, preparing the crystals into a solution, adding sulfuric acid to adjust the pH value to be 1.2-1.5, adding iron sheet to reduce, adjusting the pH value to be 4.0-5.0 by using a ferrous compound, adding a flocculating agent to settle, and filtering the obtained clear solution to obtain a refined ferrous sulfate solution after impurity removal.

B. The synthesis steps are as follows:

adding prepared NH into refined ferrous sulfate solution₃-NH₄HCO₃And mixing the solution, controlling the reaction temperature to be 45-60 ℃, detecting the pH value at any time, keeping the temperature, filtering and washing when the pH value reaches 6.5-7, namely the reaction end point.

3. The method for producing high-purity magnetic iron oxide by using ferrous sulfate as a byproduct of titanium dioxide according to claims 1 and 2, wherein the step of removing impurities comprises FeSO in a solution prepared from ferrous sulfate as a byproduct of titanium dioxide₄.7H₂The concentration of O is 55-73%, and the specific gravity of a solution prepared from the ferrous sulfate crystal is 1.2-1.3 after the ferrous sulfate crystal is frozen and crystallized.

4. The method for producing high-purity magnetic iron oxide with ferrous sulfate as a byproduct of titanium dioxide according to claims 1 and 2, wherein the synthesis step is performed using NH₃-NH₄HCO₃NH of mixed solution₃∶NH₄HCO₃The weight ratio is 1: 3-1: 6.

5. The method for producing high purity magnetic iron oxide with ferrous sulfate as byproduct of titanium dioxide according to claims 1 and 2, wherein the step of removing impurities comprises using FeCO as ferrous salt for adjusting pH of the solution₃Or Fe (OH)₂。

6. The method for producing high-purity magnetic iron oxide from ferrous sulfate as a byproduct of titanium dioxide according to claims 1 and 2, wherein the synthesis reaction is controlled at a temperature of 50 ℃ to 55 ℃.

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