A method for recovering iron from iron slag

Abstract

This invention discloses a method for recovering iron from iron ore slag. The method involves adding FeSO4∙7H2O to the electrolyte to promote the leaching of iron from the ore slag. The added H2SO4 stabilizes the pH of the electrolysis system within the range of 1.5-3, preventing Fe... 3+ Precipitation occurs, which helps Fe 3+ Iron is deposited at the cathode. This invention utilizes a slurry electrolysis method to recover iron from vanadium slag, achieving a recovery rate of up to 87%; the resulting cathode iron has a purity of up to 99.81%; and the electrolyte contains Fe... 3+ The high concentration allows for recycling; the leaching residue is washed with water and then disposed of in a harmless manner, which solves the technical problems of complex processes, long time consumption and high energy consumption in the existing methods for recovering iron from iron ore slag.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for recovering iron from iron slag. Background Technology

[0002] Currently, the main method for hydrometallurgical zinc production in China is the potassium ferrous sulfate leaching process, which includes neutral leaching, high-temperature high-acid leaching, pre-neutralization, alum precipitation, and solid-liquid separation at each stage. Ferrous sulfate slag primarily originates from the residue generated during the alum and iron precipitation process.

[0003] Large-scale untreated stockpiling of iron vanadium slag not only occupies significant land resources but also poses serious threats to the ecological environment. To address the environmental problems caused by iron vanadium slag stockpiling, the revised "National Hazardous Waste Inventory" of 2016 classified iron vanadium slag as hazardous waste, and the revised "Administrative Measures for Hazardous Waste Operation Licenses" of 2017 also imposed strict regulations on the treatment and disposal of iron vanadium slag, aiming to minimize its environmental pollution. Iron vanadium slag should only be disposed of in acidic environments (pH value approximately...). It only possesses a certain degree of stability under certain conditions. However, it easily decomposes and releases heavy metals and toxic elements such as Pb, Zn, As, Cu, and Ag when heated or when the pH value is changed. These substances cannot be biodegraded. Accumulation in the human body can damage bodily functions and cause poisoning, and its pollution of soil is also irreversible.

[0004] In the hydrometallurgical zinc smelting process, zinc roasted ore is used as a neutralizing agent to neutralize the free acid produced by alum precipitation. This inevitably leaves undissolved Zn in the iron vanadium slag, resulting in zinc metal loss. Currently, iron vanadium slag is generally treated and utilized for harmless disposal through leaching followed by sedimentation. CN105039712A describes adding large amounts of reducing agents, hydrophobic agents, and flotation agents to iron vanadium slag, followed by solid-liquid separation to obtain iron oxide and calcium sulfate. This process generates a large amount of wastewater, creating new environmental problems. CN109852803B describes using dilute sulfuric acid solution to prepare a slurry, followed by high-temperature conversion (160-250℃) liquid-solid separation to obtain conversion slag and conversion liquid. Valuable metals exist in ionic form in the conversion liquid, requiring further processing to obtain the corresponding iron products. Summary of the Invention

[0005] To address the aforementioned problems, the main objective of this invention is to provide a method for extracting iron from iron slag, which is rich in iron.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for recovering iron from iron slag, the specific steps of which are as follows:

[0007] (1) At room temperature (25℃), add water and FeSO4·7H2O powder in a certain proportion to prepare FeSO4 solution;

[0008] (2) Divide the FeSO4 solution into two equal volumes and place them in the cathode chamber and anode chamber of the electrolytic cell, respectively;

[0009] (3) A certain amount of sieved iron slag powder is placed in the anode chamber of the above electrolytic cell (the iron slag is leached in the anode chamber and Fe is deposited in the cathode chamber);

[0010] (4) Adjust the pH value of the anode chamber and the cathode chamber. After energizing, control the current density and electrolyze at a constant current for a certain period of time, and the iron sheet will grow on the cathode.

[0011] Furthermore, the electrolytic cell is divided into a cathode chamber and an anode chamber using a double-layered acid and alkali resistant filter cloth diaphragm.

[0012] Furthermore, the iron slag raw material is crushed into powder, and the crushed powder is dried in a constant temperature oven at 60℃ for 24 hours, and then ground until it passes through a 100-mesh sieve.

[0013] Furthermore, the concentration of the FeSO4 solution is 0.75-1.25 mol / L, preferably 1.0 mol / L.

[0014] Furthermore, the ratio of the sieved iron alum slag powder to the FeSO4 solution is 50-80 g / L, preferably 60-70 g / L.

[0015] Furthermore, the pH value of the anode chamber and the cathode chamber is adjusted to 1.5-2.5, preferably 2.0.

[0016] Furthermore, the current density is 20-40 mA / cm². 2 30-40 mA / cm is preferred 2 The electrolysis time is 6 hours or more, preferably 8-12 hours.

[0017] Furthermore, the anode and cathode are made of stainless steel plates and DSA ruthenium-plated titanium plates, respectively.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) This invention extracts iron from iron slag and prepares it into widely used electrolytic iron, realizing the resource utilization of iron slag.

[0020] (2) This invention only requires adding inexpensive FeSO4·7H2O to the slurry and then electrolyzing it to obtain high-purity electrolytic iron. The electrolyte can be recycled multiple times, and heavy metals such as Cd, Pb, and As are enriched in the electrolyte. Moreover, the above process is convenient, simple, environmentally friendly, and safe.

[0021] (3) This invention can fully exploit the utilization value of iron ore slag and enrich the heavy metals in the iron ore slag to a certain extent, which has considerable economic and environmental benefits. Attached Figure Description

[0022] Appendix Figure 1 This is a process flow diagram of a method for recovering iron from iron slag according to the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] The slurry electrolysis method involves simultaneous anodic leaching and cathodic deposition, resulting in a simpler process and making it a feasible way to utilize resources.

[0025] The main phases of the iron alum slag are hexagonal crystal system iron alum, potassium ferroalloy, or lead-zinc ferroalloy mixed iron alum, Fe2O3, ZnFe2O4, and ZnSO4. The iron alum slag used in the embodiments of this invention comes from a zinc smelter, and its specific composition is shown in Table 1.

[0026] Table 1. Percentage of elements in iron oxide slag

[0027]

[0028] Example 1

[0029] Combination Figure 1 The method for recovering iron from iron ore slag according to the present invention includes the following steps:

[0030] The electrolytic cell is divided into anode and cathode chambers by a double-layered acid and alkali resistant filter cloth diaphragm. 28g of dried and sieved iron oxide slag powder is placed in the anode chamber. 111.2g of FeSO4·7H2O powder is placed in a beaker, and approximately 300mL of water is added to prepare a 400mL FeSO4·7H2O solution. 200mL of FeSO4·7H2O solution is then added to each of the anode and cathode chambers. The pH of both chambers is adjusted to 2 using 98% concentrated sulfuric acid. A ruthenium-plated titanium plate (DSA) is used as the anode plate, and a stainless steel plate as the cathode plate. The power supply is connected, and a constant current density of 30mA / cm² is maintained. 2After electrolysis at 25℃ for 8 hours, silver iron flakes grew on the cathode plate. After drying, the mass of the precipitated electrolytic iron powder was measured to be 7.0620 g. The dried cathode product and anode slag were completely digested, and the Fe concentration in the digestion solution and electrolyte of the cathode product and anode slag was measured. The iron recovery rate was calculated to be 87%, and the purity of the cathode product was 99.8%.

[0031] Example 2

[0032] Other conditions are the same as in Example 1. Considering the effect of different current densities on iron recovery rate, the experimental results are shown in Table 2:

[0033] Table 2. Effect of different current densities on iron recovery rate

[0034]

[0035] The results above indicate that a current density of 30 mA / cm² is preferred. 2 (Example 1)

[0036] Example 3

[0037] Other conditions are the same as in Example 1. Considering the effect of different electrolysis times on iron recovery rate, the experimental results are shown in Table 3:

[0038] Table 3 Effect of different electrolysis times on iron recovery rate

[0039]

[0040] The results above indicate that the preferred electrolysis time is 8 hours (Example 1).

[0041] Example 4

[0042] Other conditions were the same as in Example 1. Considering the effect of different pH values ​​on iron recovery, the experimental results are shown in Table 4:

[0043] Table 4. Effect of different pH values ​​on iron recovery rate

[0044]

[0045]

[0046] The results above indicate that pH 2.0 is preferred (Example 1).

[0047] Example 5

[0048] Other conditions are the same as in Example 1. Considering the effect of different electrolysis times on iron recovery, the experimental results are shown in Table 5:

[0049] Table 5. Effect of different solid-liquid ratios on iron recovery rate

[0050]

[0051] The results above indicate that the preferred solid-liquid ratio is 70 g / L (Example 1).

[0052] Example 6

[0053] Other conditions are the same as in Example 1, considering different Fe... 2+ The effect of concentration on iron recovery rate is shown in Table 6:

[0054] Table 6 Different Fe 2+ Effect of concentration on iron recovery

[0055]

[0056] The results above show that Fe 2+ The preferred concentration is 1 mol / L (Example 1).

[0057] Specific examples show that the iron recovery rate can reach over 87%, the current efficiency exceeds 90% according to Faraday's law, and the iron purity can reach up to 99.81%.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for recovering iron from iron ore slag, characterized in that, The specific steps are as follows: (1) Divide the FeSO4 solution into two equal volumes and place them in the cathode chamber and anode chamber of the electrolytic cell, respectively; (2) Place a certain amount of sieved iron slag powder into the anode chamber of the above-mentioned electrolytic cell; (3) Adjust the pH value of the anode chamber and the cathode chamber, and after energizing, control the current density. After electrolysis with constant current for a certain period of time, the iron sheet grows on the cathode. The concentration of the FeSO4 solution was 0.75-1.25 mol / L. The ratio of sieved iron alum slag powder to FeSO4 solution is 50-80 g / L; Adjust the pH of the anode and cathode chambers to 1.5-2.5; Current density is 20-40 mA / cm 2 .

2. The method as described in claim 1, characterized in that, The electrolytic cell is divided into a cathode chamber and an anode chamber by a double-layer acid and alkali resistant filter cloth diaphragm.

3. The method as described in claim 1, characterized in that, The iron slag raw material was crushed into powder, and the crushed powder was dried in a constant temperature oven at 60℃ for 24 hours, and then ground until it passed through a 100-mesh sieve.

4. The method as described in claim 1, characterized in that, The concentration of the FeSO4 solution is 1.0 mol / L.

5. The method as described in claim 1, characterized in that, The ratio of sieved iron alum slag powder to FeSO4 solution is 60-70 g / L.

6. The method as described in claim 1, characterized in that, Adjust the pH of the anode and cathode chambers to 2.

0.

7. The method as described in claim 1, characterized in that, Current density is 30-40 mA / cm 2 .

8. The method as described in claim 1, characterized in that, The electrolysis time is more than 6 hours.

9. The method as described in claim 1, characterized in that, The electrolysis time is 8-12 hours.

10. The method as described in claim 1, characterized in that, The anode and cathode are made of stainless steel plate and DSA ruthenium-plated titanium plate, respectively.

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