A method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy

Abstract

The present invention relates to the field of hydrometallurgy technology. In view of the serious environmental pollution problem existing in the separation and extraction of ferrochromium alloys, a method for separating ferrochromium from ferrochromium alloys by electrolytic catalytic oxidation is disclosed. The method comprises the following steps: S1 takes the ferrochromium alloy, immerses it in a sulfuric acid solution, and filters it to obtain a filter residue X and a filtrate I; S2 takes the filtrate I, adds a pH buffer to control the pH value to 3.5-5.5, and obtains a mixed solution II; S3 places a cathode material and an anode material into the mixed solution II, energizes it, and performs electrolytic catalytic oxidation treatment to obtain an electrolytic slurry III; S4 takes the electrolytic slurry III, filters it by pressure, and obtains a chromium-containing filter residue Y and an iron-containing filtrate IV. The ferrochromium separation method for ferrochromium alloys of the present invention has the advantages of less added additives and can reduce the discharge of waste; and utilizes electrolytic catalytic oxidation to avoid environmental pollution caused by roasting.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrometallurgy, and in particular to a method for separating iron and chromium from an electrolytically catalytically oxidized iron-chromium alloy. Background Art

[0002] Electrolytic iron is a high-purity iron produced by electrolyzing an iron-containing substance as the anode material in an aqueous solution of ferric sulfate. It boasts high purity, a soft and malleable texture, and strong corrosion resistance to alkaline solutions or molten alkalis. It is used in applications such as superheat-resistant steel, rare earth magnetostrictive alloys, and aviation parts. Chromium, a hard, brittle, and corrosion-resistant strategic metal, is widely used in metallurgy, chemical engineering, cast iron, refractories, and high-precision technology. Industrial chromium is typically smelted using the aluminothermic process or electrolytic methods.

[0003] In industry, when using ferrochromium alloys as raw materials to smelt chromium metal or electrolytic iron, the ferrochromium alloy or ferrochromium ore is typically directly extracted and smelted using a calcium- or calcium-free roasting method. The ferrochromium alloy is then mixed with alkali and oxidatively roasted in a rotary kiln. The mixture is then cooled, crushed, and purified by water leaching to produce a chromium-containing metal compound. However, in actual application, existing ferrochromium alloy purification and smelting methods, when used directly to smelt chromium metal or electrolytic iron, result in a large amount of iron or chromium becoming waste slag, resulting in low resource utilization. Furthermore, these methods pose significant pollution risks, resulting in low purification rates and complex processes.

[0004] Based on this, we urgently need an environmentally friendly and efficient method for separating iron and chromium from ferrochromium alloys that can be subsequently used for smelting chromium metal and electrolytic iron. Summary of the Invention

[0005] The technical problems to be solved by the present invention are:

[0006] At present, the process of using iron-chromium alloy to smelt chromium metal or electrolytic iron does not separate iron and chromium before smelting or electrolysis, which means that a large amount of iron or chromium elements will eventually become waste slag, resulting in low resource utilization. The raw materials need to be roasted at extremely high temperatures multiple times, which seriously pollutes the natural environment and also discharges a large amount of waste during the production process. In addition, the preparation process is complicated, the steps are complicated, and the cost is high.

[0007] The technical solution adopted in the present invention is:

[0008] The present invention provides a method for separating iron and chromium by electrolytic catalytic oxidation of an iron-chromium alloy, comprising the following steps:

[0009] S1: Take an iron-chromium alloy, immerse it in a sulfuric acid solution, and filter it to obtain a filter residue X and a filtrate I;

[0010] S2 takes filtrate I, adds pH buffer, controls pH value to 3.5-5.5, and obtains mixed solution II;

[0011] S3: passing the mixed solution II into the electrolytic cell, placing the cathode material and the anode material, applying power, and performing electrolytic catalytic oxidation treatment to obtain electrolytic slurry III;

[0012] S4 takes electrolytic slurry III and filters it to obtain chromium-containing filter residue Y and iron-containing filtrate IV.

[0013] Preferably, in step S1, the solid-liquid volume ratio of the ferrochromium alloy to the sulfuric acid solution is 5-10:1.

[0014] Preferably, in step S1, when the pH value is impregnated to 3.5-4.5, filtering is performed; the impregnation temperature is controlled to be 70-90° C., and the impregnation time is 150-240 min.

[0015] Preferably, in step S2, the pH buffer solution is diammonium hydrogen phosphate solution, and the amount of the pH buffer solution added is 8-12 mL / L.

[0016] Preferably, in step S3, both the cathode material and the anode material are pure iron plates, and the thickness of the pure iron plates is 4.5-5.5 mm; when the thickness of the anode material is less than 2 mm, the cathode material and the anode material are replaced.

[0017] Preferably, when powered on, the current density is controlled to be 700A / m 2 —900A / m 2 , control the electrolyte flow rate according to the effective volume of the electrolytic cell so that the electrolysis time is 1-3h.

[0018] The beneficial effects of the present invention are as follows:

[0019] In the present invention, the ferrochrome alloy or ferrochrome ore is first subjected to ferrochrome separation, and then the iron and chromium elements are extracted separately, thereby realizing full utilization of the ferrochrome alloy resources. Specifically, the iron and chromium metals in the ferrochrome alloy raw material can be dissolved to a great extent in a dilute sulfuric acid solution by acid leaching, and then electrolytic catalytic oxidation is performed to adjust the pH value of the solution, so that part of the Fe in the original acid leaching solution can be dissolved. 2+ Oxidized to Fe 3+ , and is hydrolyzed into a solid precipitate of Fe(OH)3; Fe(OH)3 is an absorptive flocculent precipitate that can adsorb trivalent chromium ions in the acid leachate to form a co-precipitate of ferric chromate hydroxide. FeSO4 and high-chromium slag can then be obtained through solid-liquid separation. FeSO4 can be used as a raw material for electrolytic iron, and the high-chromium slag is used for smelting chromium metal. The iron-chromium separation process of the present invention requires minimal external additives, reducing waste emissions. Electrolytic catalytic oxidation is utilized to avoid environmental pollution caused by roasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a process flow chart of the iron-chromium separation method in Example 1. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0022] The present invention provides a method for separating iron and chromium by electrolytic catalytic oxidation of an iron-chromium alloy, comprising the following steps:

[0023] S1: Take an iron-chromium alloy, immerse it in a 150g / L sulfuric acid solution, and filter it to obtain a residue X and a filtrate I;

[0024] S2 takes filtrate I, adds pH buffer, controls pH value to 3.5-5.5, and obtains mixed solution II;

[0025] S3: passing the mixed solution II into the electrolytic cell, placing the cathode material and the anode material, applying power, and performing electrolytic catalytic oxidation treatment to obtain electrolytic slurry III;

[0026] S4 takes electrolytic slurry III and filters it to obtain chromium-containing filter residue Y and iron-containing filtrate IV.

[0027] In step S1, the solid-liquid volume ratio of the iron-chromium alloy to the sulfuric acid solution is 5-10:1. In step S1, the solution is filtered when the pH value reaches 3.5-4.5. The immersion temperature is controlled to be 70-90°C and the immersion time is 150-240 minutes.

[0028] In ferrochromium alloy, iron and chromium mainly exist in the form of single elements, wherein, by mass percentage, the iron content is about 85-90%, and the chromium content is about 2-5%. When the ferrochromium alloy is acid-leached in sulfuric acid solution, the iron and chromium react as follows to obtain ionic Fe 2+ and Cr 3+ :

[0029] Fe+H2SO4=FeSO4+H2

[0030] 2Gr+3H2SO4=Cr2(SO4)3+3H2

[0031] In step S2, considering the economic efficiency and practicality of the process, diamine hydrogen phosphate solution is used as the pH buffer to control the pH value during the electrolytic catalytic oxidation process; the amount of pH buffer added is 8-12mL / L to adjust the pH value to within the range of 3.5-5.5. In step S3, both the cathode material and the anode material are pure iron plates with a thickness of 4.5-5.5mm. When the thickness of the anode material is less than about 2mm, the cathode material and the anode material are exchanged, and the cycle is repeated to reduce the consumption of the anode and cathode iron plates. When power is turned on, the current density is controlled to 700A / m 2 —900A / m 2 The electrolyte flow rate is controlled according to the effective volume of the electrolytic cell, so that the electrolysis time is controlled to about 2 hours. The mixed solution II obtained in step S2 is directly passed into the electrolytic cell used for electrolytic catalytic oxidation in step S3. The inlet flow rate is controlled to be consistent with the slurry outlet flow rate at the bottom of the electrolytic cell to maintain the volume balance of the electrolysis system.

[0032] Iron plates are used as cathode and anode plates, and a continuous electrolysis process is used to electrolyze and catalytically oxidize the acid leaching solution. By controlling the current density, electrolyte flow rate and electrolysis time, part of the Fe in the solution is reduced. 2+ After catalytic oxidation, Fe 3+ , the oxidized part of Fe 2+ Finally, it is used to adsorb chromium ions to achieve solid-liquid separation of iron and chromium. During the electrolysis process, the chemical reactions at the anode and cathode are as follows:

[0033] Fe 2+ -e - =Fe 3+

[0034] 2H + +2e - =H2

[0035] Fe obtained after oxidation 3+ In an acidic environment with a pH value of 3.5-5.5, it can be hydrolyzed into a fixed precipitate of iron hydroxide. The hydrolysis reaction is as follows:

[0036] Fe 3+ + 3H2O=Fe(OH)3+3H +

[0037] The Fe(OH)3 obtained after hydrolysis can adsorb the chromate anions in the acid leaching solution to form chromate iron hydroxide co-precipitation. The chemical reaction of this process is as follows:

[0038] Cr 3+ +3H2O+Fe(OH)3=Cr2O3·Fe(OH)3+6H +

[0039] FeSO4 and high chromium slag can be obtained through solid-liquid separation. FeSO4 can be used as raw material for electrolytic iron, and high chromium slag is used for smelting chromium metal.

[0040] <Example>

[0041] like Figure 1 As shown, this embodiment provides a method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy, comprising the following steps:

[0042] The ferrochromium alloy is added to a reaction tank, and a dilute sulfuric acid solution is added, with the initial acid content controlled at 150 g / L and the liquid-to-solid ratio controlled at 5:1. The reaction is carried out at 80°C for 4 hours, and the end point pH is controlled to be approximately 4. The acid-dissolved slurry is then filtered using a filter press, and the filtrate is a mixed solution of ferrous sulfate and chromium sulfate. The main components of the filter residue are undissolved silicon dioxide and insoluble substances such as silicates.

[0043] Add diammonium hydrogen phosphate solution to the first stage of dissolution and leaching filtrate at a rate of 10 ml / L and stir to mix evenly;

[0044] The above solution is pumped into the pre-electrolysis tank for pre-electrolysis catalytic oxidation treatment, and the current density is controlled at 800A / m 2 The electrolysis time is controlled at about 2h (the electrolysis time refers to the time from the solution entering the electrolytic cell to the solution flowing out of the electrolytic cell);

[0045] The slurry is extracted from the bottom of the electrolytic cell and filtered to obtain a filtrate which is a ferrous sulfate solution and a filter residue which is a high-chromium residue.

[0046] The components of the separated liquid obtained in this example were analyzed, and the test results are shown in the following table:

[0047]

[0048] According to the test results in the above table, in this embodiment:

[0049] (1) After the ferrochromium alloy is subjected to processes such as dissolution, electrolytic pretreatment, catalytic oxidation, and filtration, the average chromium content in the acid leaching solution is 1.384 g / L. After electrolytic pretreatment and catalytic oxidation, the chromium content of the iron-containing filtrate is 0.013 g / L, and the chromium separation rate reaches 99.1%, indicating an excellent chromium-iron separation effect.

[0050] (2) The chromium alloy was subjected to dissolution, electrolytic pretreatment, catalytic oxidation, and filtration processes. The ferrous content in the acid leaching solution was 61.53 g / L, the ferrous content in the final filtrate was 58.47 g / L, and the ferrous loss rate was 4.98%.

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for separating iron and chromium from an electrolytically catalytically oxidized iron-chromium alloy, characterized in that: The steps include: S1: Take the iron-chromium alloy, immerse it in sulfuric acid solution, filter it, and obtain the residue X and filtrate I; S2: Take filtrate I, add 8-12 mL / L diammonium hydrogen phosphate solution, and control the pH value to 3.5-5.5 to obtain mixed solution II; S3: passing the mixed solution II into the electrolytic cell, placing the cathode material and the anode material, applying electricity, and performing electrolytic catalytic oxidation treatment to obtain electrolytic slurry III; Among them, the cathode material and the anode material are both pure iron plates with a thickness of 4.5-5.5mm. When the thickness of the anode material is less than 2mm, the cathode material and the anode material are replaced; S4: Take electrolytic slurry III, filter press, and obtain chromium-containing filter residue Y and iron-containing filtrate IV.

2. The method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy according to claim 1, characterized in that: In step S1, the solid-liquid volume ratio of the ferrochromium alloy to the sulfuric acid solution is 5-10:

1.

3. The method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy according to claim 1, characterized in that: In step S1, the mixture is immersed until the pH value reaches 3.5-4.5, and then filtered.

4. The method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy according to claim 3, characterized in that: The immersion temperature is controlled at 70-90°C and the immersion time is 150-240 minutes.

5. The method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy according to claim 1, characterized in that: When powered on, the current density is controlled to be 700A / m 2 —900 A / m 2 .

6. The method for separating iron and chromium by electrolytic catalytic oxidation of iron-chromium alloy according to claim 5, characterized in that: The electrolyte flow rate is controlled according to the effective volume of the electrolytic cell so that the electrolysis time is controlled within 1-3 hours.

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