Method for reducing amount and zinc of hazardous waste iron slag

Abstract

The invention discloses a method for reducing amount and zinc of hazardous waste iron slag, and belongs to the technical field of metallurgy. The method comprises the following steps: adding a sulfuric acid solution into the hazardous waste iron slag for size mixing and pre-activation to obtain a pre-activated material; adding a directional complexing agent solution into the pre-activated material to obtain a mixed system, and reacting the mixed system under certain conditions; and after the reaction is finished, carrying out solid-liquid separation to obtain reduced iron slag and a complex zinc solution. Through the synergistic effect of weak acid pre-activation and the directional complexing agent, selective removal of zinc, stable retention of an iron-based phase and precise control of process parameters are achieved, and the method has important metallurgical engineering significance for reducing the properties of hazardous wastes and achieving reduction and resource utilization of the iron slag.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for reducing the amount of zinc in hazardous waste iron slag. Background Technology

[0002] In the pyrometallurgical process of non-ferrous metals, flue gas purification and dust removal systems generate a large amount of iron-containing solid residue. This type of iron slag is usually enriched with volatile metal elements such as zinc and lead, with a high zinc content, mostly occurring in the form of zinc oxide, zinc ferrite, and zinc-iron spinel within the iron-based mineral phase. Due to the high leaching toxicity of zinc and associated heavy metals, this type of material is often identified as hazardous waste and must be stored and disposed of according to hazardous waste regulations. This not only occupies storage space but also brings high environmental disposal costs and environmental risks.

[0003] Existing treatment methods mainly include high-temperature volatilization recovery, strong acid leaching, and solidification landfill. High-temperature methods are energy-intensive and require large investments; although strong acid leaching can dissolve zinc, it easily leads to the dissolution of large amounts of iron, high acid consumption, large waste volume, and poor selectivity; solidification landfill does not reduce the hazardous waste's properties at the source and has low resource utilization value.

[0004] Therefore, it is essential to develop a short-process approach based on selective separation and resource utilization. Summary of the Invention

[0005] To address the problem of recycling and utilizing iron-containing solid residues, this invention provides a method for reducing the amount of hazardous waste iron slag and decreasing zinc content, specifically including the following steps: (1) Add sulfuric acid solution to hazardous waste iron slag for slurry conditioning and pre-activation to obtain pre-activated material.

[0006] (2) Add a directional complexing agent solution to the pre-activated material to obtain a mixed system. The mixed system reacts under certain conditions. After the reaction is completed, solid-liquid separation is performed to obtain iron slag and zinc complex solution.

[0007] Preferably, the concentration of the sulfuric acid solution in step (1) of the present invention is 30~50g / L.

[0008] Preferably, in step (1) of the present invention, the solid-liquid ratio of hazardous waste iron slag and sulfuric acid solution is 1 kg: (3~6) L.

[0009] Preferably, the pre-activation of the slurry in step (1) of the present invention specifically involves stirring at 25~50℃ for 30~60 min.

[0010] Preferably, the pH value of the pre-activated material in step (1) of the present invention is 1.5~2.0.

[0011] Preferably, the directional complexing agent in step (2) of the present invention is one or more of tartaric acid, citric acid, malic acid, and sodium gluconate.

[0012] Preferably, in step (2) of the present invention, the mass ratio of the directional complexing agent (based on solute) to the zinc in the pre-activated material is 10~100:1.

[0013] Preferably, the reaction conditions in step (2) of the present invention are: adjusting the pH of the mixed system to 3.0~5.5, controlling the redox potential of the mixed system to 150~350mV, and stirring the reaction for 60~90min.

[0014] Preferably, in step (2) of the present invention, the complexing agent is prepared as an aqueous solution and the concentration of the complexing agent solution is 1-20 g / L. During the addition of the directional complexing agent solution, the pH value and oxidation-reduction potential (ORP) of the system are detected in real time by an online monitoring device. If the pH and ORP need to be adjusted after all the directional complexing agent solution has been added, they can be adjusted by adding the sulfuric acid solution in step (1).

[0015] This invention provides a method for reducing the amount of hazardous waste iron slag and decreasing zinc content, which has the following beneficial effects: (1) This invention abandons the drawback of traditional strong acid leaching causing a large amount of iron to dissolve. Through the synergistic effect of weak acid pre-activation and directional complexing agent, and by utilizing the difference between zinc and iron in thermodynamic activity and complexing stability, a reaction system that promotes preferential zinc dissolution is constructed, thereby achieving selective dezincification without destroying the iron-based main structure.

[0016] (2) By directional dezincification, the highly toxic components in iron slag are effectively separated, the mass of solid residue is significantly reduced, and the amount of iron slag is substantially reduced, which can directly save huge amounts of hazardous waste storage and landfill costs.

[0017] (3) By introducing a weak acid environment and complexing agents (citric acid, etc.), the present invention constructs a mild chemical reaction system. At the same time, by combining real-time online monitoring of pH, conductivity and redox potential (ORP), the reaction process is precisely controlled, effectively inhibiting the secondary deposition of zinc hydrolysis and the oxidation precipitation of iron, and ensuring the repeatability and stability of the process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The zinc content in the hazardous waste iron slag treated in the embodiments and comparative examples of the present invention is 11.45% by mass.

[0021] Example 1 A method for reducing the amount of hazardous waste iron slag and lowering zinc content, the process diagram is as follows: Figure 1 As shown, the specific steps include: (1) Add 600 mL of 30 g / L sulfuric acid solution to 200 g of hazardous waste iron slag for slurry preparation and pre-activation (pH 1.8), and stir at 40 °C for 60 min to obtain the pre-activated material.

[0022] (2) Slowly add citric acid solution (the mass ratio of citric acid in the citric acid solution to zinc in the pre-activated material is 50:1) to obtain a mixed system (pH stable at 3.5). Stir the reaction for 60 min with the redox potential (ORP) of the system in the range of 200 mV. After the reaction is completed, perform solid-liquid separation to obtain iron slag and complexed zinc solution.

[0023] The reduced iron slag obtained in this embodiment has a mass of 110g, of which the zinc content is 6%.

[0024] Example 2 A method for reducing the amount of hazardous waste iron slag and lowering zinc content, the process diagram is as follows: Figure 1 As shown, the specific steps include: (1) Add 600 mL of 30 g / L sulfuric acid solution to 200 g of hazardous waste iron slag for slurry preparation and pre-activation (pH 1.8), and stir at 40 °C for 60 min to obtain the pre-activated material.

[0025] (2) Slowly add malic acid solution (the mass ratio of malic acid in the malic acid solution to zinc in the pre-activated material is 50:1) to obtain a mixed system (pH stable at 3.5). Stir the reaction for 60 min with the redox potential (ORP) of the system in the range of 200 mV. After the reaction is completed, perform solid-liquid separation to obtain iron slag and complexed zinc solution.

[0026] The reduced iron slag obtained in this embodiment has a mass of 130g, of which the zinc content is 10%.

[0027] Example 3 A method for reducing the amount of hazardous waste iron slag and lowering zinc content, the process diagram is as follows: Figure 1 As shown, the specific steps include: (1) Add 600 mL of 30 g / L sulfuric acid solution to 200 g of hazardous waste iron slag for slurry preparation and pre-activation (pH 1.8), and stir at 40 °C for 60 min to obtain the pre-activated material.

[0028] (2) Add sodium gluconate solution slowly to the pre-activated material (the mass ratio of sodium gluconate in the sodium gluconate solution to zinc in the pre-activated material is 50:1) to obtain a mixed system (pH stable at 3.5). Stir the reaction for 60 min with the redox potential (ORP) of the system in the range of 200 mV. After the reaction is completed, perform solid-liquid separation to obtain iron slag and complexed zinc solution.

[0029] The reduced iron slag obtained in this embodiment has a mass of 140g, of which the zinc content is 8%.

[0030] Example 4 A method for reducing the amount of hazardous waste iron slag and lowering zinc content specifically includes the following steps: (1) Add 1200mL of sulfuric acid solution with a concentration of 40g / L to 200g of hazardous waste iron slag for slurry pre-activation (pH 1.5), stir at 50℃ for 40min to obtain pre-activated material.

[0031] (2) Slowly add citric acid solution (the mass ratio of citric acid in the citric acid solution to zinc in the pre-activated material is 100:1) to obtain a mixed system (pH stable at 4.0). Stir the reaction for 80 min with the redox potential (ORP) of the system within the range of 150 mV. After the reaction is completed, perform solid-liquid separation to obtain iron slag and complexed zinc solution.

[0032] In this embodiment, the mass of the reduced iron slag obtained is 130g, of which the zinc content is 7.6%.

[0033] Example 5 A method for reducing the amount of hazardous waste iron slag and lowering zinc content specifically includes the following steps: (1) Add 800 mL of 50 g / L sulfuric acid solution to 200 g of hazardous waste iron slag for slurry preparation and pre-activation (pH 1.8), stir at 30 °C for 30 min to obtain the pre-activated material.

[0034] (2) Slowly add citric acid solution (the mass ratio of citric acid in the citric acid solution to zinc in the pre-activated material is 10:1) to obtain a mixed system (pH stable at 5.0). Stir the reaction for 90 min with the redox potential (ORP) of the system within the range of 350 mV. After the reaction is completed, perform solid-liquid separation to obtain iron slag and complexed zinc solution.

[0035] The iron slag obtained in this embodiment weighed 145g, and its zinc content was 8.9%.

[0036] Comparative Example 1 The difference between this comparative example and Example 1 is that no directional complexing agent is added; only sulfuric acid solution is added for the reaction. The other conditions are the same as in Example 1.

[0037] The iron slag obtained in this comparative example weighed 180g and contained 10.28% zinc.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is that sulfuric acid solution is not added; instead, a complexing agent is added directly to carry out the reaction. All other conditions are the same as in Example 1.

[0039] The iron slag obtained in this comparative example weighed 170g, with a zinc content of 8.75%.

[0040] As can be seen from the effects of Examples 1-5 and Comparative Examples 1-2, the method of synergistic treatment with weak acid pre-activation and directional complexing agent of the present invention produces iron slag with stable chemical properties after the reaction. This slag can be used as a high-quality iron-containing raw material to be supplied back to steel plants for blast furnace ironmaking or sintering feedstock, achieving high-value recycling of iron components. The simultaneously obtained complexed zinc solution has high purity and low impurity content, and can be directly used as a raw material for producing high-value-added zinc chemical products such as basic zinc carbonate and active zinc oxide, broadening the comprehensive utilization pathways of zinc resources. This invention, based on a washing method using weak acid regulation and a directional complexing system, achieves the triple goals of reducing, rendering harmless, and recycling hazardous waste. It has significant metallurgical engineering implications for reducing the hazardous properties of waste and realizing the resource utilization of iron slag.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the amount of hazardous waste iron slag and decreasing zinc content, characterized in that, Specifically, the following steps are included: (1) Add sulfuric acid solution to hazardous waste iron slag for slurry conditioning and pre-activation to obtain pre-activated material; (2) Add a directional complexing agent solution to the pre-activated material to obtain a mixed system. The mixed system reacts under certain conditions. After the reaction is completed, solid-liquid separation is performed to obtain iron slag and zinc complex solution.

2. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The concentration of the sulfuric acid solution in step (1) is 30~50g / L.

3. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The solid-liquid ratio of the hazardous waste iron slag and sulfuric acid solution in step (1) is 1 kg: (3~6) L.

4. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The pre-activation of the slurry in step (1) specifically involves stirring at 25~50℃ for 30~60 minutes.

5. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The pH value of the pre-activated material in step (1) is 1.5~2.

0.

6. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The directional complexing agent mentioned in step (2) is one or more of tartaric acid, citric acid, malic acid, and sodium gluconate.

7. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The zinc mass ratio in the directional complexing agent and the pre-activated material in step (2) is 10~100:

1.

8. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The reaction conditions described in step (2) are: adjust the pH of the mixed system to 3.0~5.5, control the redox potential of the mixed system to 150~350mV, and stir the reaction for 60~90min.

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