Method for comprehensively recovering valuable elements from nonferrous smelting waste acid

Abstract

The invention belongs to the technical field of metallurgy, and relates to a method for comprehensively recovering valuable elements from nonferrous smelting waste acid, which comprises the following steps: S1, mixing the waste acid with pyrrhotite, reacting in a sulfur dioxide atmosphere, and after the reaction, carrying out solid-liquid separation to obtain copper slag and copper removal liquid; and S2, H2S gas is introduced into the copper removal liquid obtained in the step S1, and after reaction, arsenic sulfide slag and arsenic removal liquid are obtained through solid-liquid separation. According to the method, FeS in the pyrrhotite selectively reacts with CuSO4 in the waste acid to generate indissolvable copper sulphide precipitates, meanwhile, under the protection of the sulfur dioxide atmosphere, the arsenic element in the waste acid is kept in a dissolved state and does not precipitate, the copper and arsenic elements in the waste acid can be effectively separated through the synergistic effect of the FeS and the CuSO4, and the separation steps are simple and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for comprehensively recovering valuable elements from non-ferrous smelting waste acid. Background Art

[0002] Non-ferrous metals refer to all metals other than iron, chromium, manganese, and their alloys. They typically possess distinctive colors, excellent electrical and thermal conductivity, ductility, and corrosion resistance, and are widely used in industry and daily life. Non-ferrous metal smelting involves the extraction and refining of non-ferrous metals from ores or secondary resources (such as waste) through physical, chemical, or electrochemical methods. The flue gas generated during non-ferrous metal smelting must first undergo a purification process to remove impurities before being fed to the acid production process. To prevent excessive impurity concentrations in the wash water, the purification process must discharge some of the waste acid, known as "sloped acid." For example, the acid production process using pyrite as raw material generates approximately 50 kilograms of "sloped acid" for every ton of sulfuric acid produced. The flue gas contains large amounts of fine dust particles, as well as metallic contaminants such as arsenic, mercury, lead, zinc, and cadmium, and gases such as SO₂ and SO₃. These substances enter the "sloped acid" during the scrubbing process, resulting in a highly complex composition that cannot be directly utilized. This not only wastes precious sulfuric acid resources but also poses a threat to the environment. Therefore, the "sloped acid" must be treated and rendered harmless. Traditional methods for treating waste acid include "chemical precipitation" and "lime neutralization", but these methods will produce a large amount of neutralization slag, which requires a lot of storage space, and will also produce a large amount of reclaimed water after the treatment meets the standards, thereby increasing the company's wastewater discharge.

[0003] Currently, the main methods for treating waste acid in China include lime neutralization, neutralization-iron salt co-precipitation, and sulfidation. Lime neutralization involves directly adding lime to the waste acid for neutralization; neutralization-iron salt co-precipitation involves adding iron salts after adjusting the pH of the waste acid; and sulfidation involves adding a sulfiding agent, such as sodium sulfide or hydrogen sulfide, to the waste acid. All three methods effectively remove arsenic and heavy metals. However, during the purification process, valuable metals in the waste acid precipitate with the waste residue, resulting in large waste residue volumes and low valuable metal grades. This makes recovery difficult and wastes resources.

[0004] The sulfide precipitation method has been widely used in industrial production due to its simple operation and low production cost. However, this method has challenges in achieving effective separation and recovery of copper and arsenic. At present, the separation of copper and arsenic in waste acid mainly adopts the following methods: (1) Using arsenic sulfide or arsenic sulfide slag to replace copper in waste acid, which is the most widely used method. However, there is a problem, that is, the concentration of copper and arsenic in waste acid must be strictly controlled. Arsenic sulfide or arsenic sulfide slag undergoes a replacement reaction with copper in waste acid, and copper is precipitated in the form of copper sulfide, while arsenic exists in the waste acid in the form of arsenous acid. Since the solubility of arsenous acid in waste acid is low (usually less than 20g / L), when the concentration of copper and arsenic in waste acid is high, the arsenous acid produced will be supersaturated and precipitate in the form of solid arsenic trioxide, mixing with copper sulfide, resulting in a high arsenic content in copper sulfide, which is not conducive to subsequent treatment. (2) Directly sulfiding the waste acid to produce copper sulfide arsenic slag, which is then added to alkaline solution. Arsenic sulfide dissolves in the alkaline solution, while copper sulfide remains in the slag. However, the high-arsenic alkaline wastewater produced by this method is more difficult to treat and requires acid neutralization. The operation is cumbersome during the sulfidation and arsenic removal process, the wastewater volume is large, and the cost is high. (3) Using slow-release sulfiding waste acid to precipitate copper sulfide first and then precipitate arsenic sulfide; although this method is better, the preparation cost of the slow-release sulfiding agent is high, the sulfidation control conditions are harsh, and there are problems such as low copper and arsenic separation efficiency and the generation of a large amount of H2S gas. (4) Using oxalic acid selective precipitation method, copper is precipitated in the form of copper oxalate, and arsenic remains in the waste acid. On the one hand, this method is greatly affected by pH, and the separation effect is poor when the acidity is high. On the other hand, oxalic acid is introduced into the waste acid, and further removal of oxalic acid is required, resulting in high production costs. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for comprehensively recovering valuable elements from non-ferrous smelting waste acid.

[0006] The specific technical solutions are as follows:

[0007] A method for comprehensively recovering valuable elements from non-ferrous smelting waste acid comprises the following steps:

[0008] S1: mixing the waste acid with pyrrhotite, reacting them in a sulfur dioxide atmosphere, and then obtaining copper slag and decoppering liquid through solid-liquid separation;

[0009] S2: introducing H2S gas into the copper removal solution obtained in step S1; after the reaction, performing solid-liquid separation to obtain arsenic sulfide slag and arsenic removal solution;

[0010] Wherein, in step S1, sulfur dioxide is continuously introduced during the reaction process.

[0011] Among them, non-ferrous smelting waste acid comes from the acidic wastewater produced by washing sulfur-containing flue gas from non-ferrous smelting. Its main components are: As content 0.5~20g / L, Cu content 0.1~5g / L, and acidity (pH) 0.5~1.5.

[0012] The reaction mechanism of the present invention is as follows:

[0013] The present invention utilizes FeS in pyrrhotite to selectively react with CuSO4 in the waste acid to generate insoluble copper sulfide precipitate. At the same time, under the protection of a sulfur dioxide atmosphere, the arsenic element in the waste acid remains dissolved and does not precipitate. After the copper element is removed, the arsenic element in the solution reacts with hydrogen sulfide to generate arsenic sulfide, thereby achieving efficient separation of arsenic and copper in the waste acid.

[0014] In step S1, pyrrhotite reacts in an acidic solution environment to release hydrogen sulfide, and sulfur dioxide gas reacts with hydrogen sulfide in the acidic solution environment to generate elemental sulfur. This process effectively prevents the possibility of hydrogen sulfide reacting with arsenic to generate arsenic sulfide precipitate; and, during the reaction, sulfur dioxide gas is continuously introduced into the solution, which can reduce the small amount of pentavalent arsenic in the solution to trivalent arsenic, avoiding the combination of pentavalent arsenic and iron ions to generate insoluble iron arsenate precipitate, thereby ensuring the thoroughness and selectivity of the copper-arsenic separation process. The above two key mechanisms work synergistically to ensure the high efficiency and selectivity of copper-arsenic separation in contaminated acid. The main reactions are:

[0015] FeS+CuSO4→CuS↓+FeSO4;

[0016] FeS+H2SO4→H2S+FeSO4;

[0017] SO2+H2O→H2SO3;

[0018] 2H2S+H2SO3→3S↓+3H2O;

[0019] H3AsO4+H2SO3→H3AsO3+H2SO4.

[0020] Among them, the copper content in the copper removal solution is ≤0.1 mg / L, and the arsenic content in the copper slag is ≤0.10wt%.

[0021] Furthermore, in step S1, the mesh size of the pyrrhotite is less than 200 meshes.

[0022] Furthermore, in step S1, the reaction temperature is 5-25° C., and the reaction time is 2-6 h.

[0023] Furthermore, in step S1, the molar ratio of sulfur in pyrrhotite to the total amount of copper in the waste acid is (1.1-1.5):1.

[0024] Furthermore, in step S1, sulfur dioxide is introduced to replace the air in the reaction vessel so that the reaction is carried out under a sulfur dioxide atmosphere. At the same time, during the reaction process, sulfur dioxide is continuously introduced to maintain the reaction pressure at a slightly positive pressure. The slightly positive pressure ensures that part of the sulfur dioxide dissolves in water to form sulfurous acid. Too much pressure will cause more dissolved sulfur dioxide to generate a large amount of sulfurous acid. A large amount of sulfurous acid reacts with dissolved hydrogen sulfide in the solution to generate elemental sulfur, which promotes ferrous sulfide to react with sulfuric acid to generate hydrogen sulfide, thereby reducing the utilization rate of ferrous sulfide. Preferably, the slightly positive pressure is 0.01 to 0.03 MPa.

[0025] Preferably, in step S1, the copper slag is returned to the copper smelting system to recover copper.

[0026] In step S2, after the copper is removed, hydrogen sulfide reacts with the arsenic in the copper removal solution to form arsenic sulfide precipitate. The main reactions are:

[0027] 2H3AsO3+3H2S→As2S3↓+6H2O.

[0028] Among them, the iron content in the arsenic sulfide slag is ≤0.30wt%, the copper content is ≤0.10wt%, and the arsenic content in the arsenic removal liquid is ≤0.1mg / L.

[0029] Furthermore, in step S2, the molar ratio of sulfur in the H2S gas to the total amount of arsenic in the copper removal solution is (1.5-1.8):1.

[0030] Furthermore, in step S2, the reaction temperature is 5-25° C., and the reaction time is 0.5-2 h.

[0031] Preferably, in step S2, the arsenic sulfide slag is returned to the arsenic smelting system to recover arsenic, the arsenic removal liquid is passed through a neutralization system to obtain ferrocalcium slag and neutralization water, the ferrocalcium slag is returned to the copper smelting system, and the neutralization water is reused industrially.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention utilizes pyrrhotite to selectively remove copper elements in the waste acid, and avoids the formation of arsenic sulfide and ferric arsenate precipitation by arsenic elements under the action of sulfur dioxide. The synergistic effect of the two can effectively separate copper and arsenic elements in the waste acid, and the separation steps are simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a process flow chart of a method for comprehensive recovery of valuable elements from non-ferrous smelting waste acid in a specific embodiment. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples. The following examples are intended to illustrate the present invention but are not intended to limit the scope of the invention. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0036] Example 1

[0037] A method for comprehensive recovery of valuable elements from non-ferrous smelting waste acid, wherein:

[0038] Non-ferrous smelting waste acid comes from the acidic wastewater produced by washing sulfur-containing flue gas in non-ferrous smelting. Its main components are: As content 19.52g / L, Cu content 4.68g / L, and acidity (pH) 0.5.

[0039] The steps are as follows:

[0040] S1: Adding waste acid and pyrrhotite with a mesh size of less than 200 mesh into a reactor, then introducing sulfur dioxide gas into the reactor to replace the air in the reactor, so that the reactor is in a sulfur dioxide protective atmosphere, and reacting at 5°C for 6 hours. During the reaction, sulfur dioxide is continuously introduced to maintain the reaction pressure in the reactor at 0.03 MPa. After the reaction is completed, copper slag and decoppering liquid are obtained through solid-liquid separation, and the copper slag is returned to the copper smelting system to recover cathode copper; wherein, the molar ratio of sulfur in the pyrrhotite to the total amount of copper in the waste acid is 1.5:1;

[0041] S2: H2S gas is introduced into the decoppering liquid obtained in step S1, and the reaction is carried out at 25°C for 2 hours. After the reaction is completed, arsenic sulfide slag and decoppering liquid are obtained through solid-liquid separation. The arsenic sulfide slag is returned to the arsenic smelting system to recover arsenic trioxide. The decoppering liquid is passed through a neutralization system to obtain ferric calcium slag and neutralization water. The ferric calcium slag is returned to the copper smelting system, and the neutralization water is reused industrially. The molar ratio of sulfur in the H2S gas to the total amount of arsenic in the decoppering liquid is 1.5:1.

[0042] Example 2

[0043] A method for comprehensive recovery of valuable elements from non-ferrous smelting waste acid, wherein:

[0044] Non-ferrous smelting waste acid comes from the acidic wastewater produced by washing sulfur-containing flue gas in non-ferrous smelting. Its main components are: As content 0.52g / L, Cu content 0.14g / L, and acidity (pH) 1.5.

[0045] The steps are as follows:

[0046] S1: Adding waste acid and pyrrhotite with a mesh size of less than 200 mesh into a reactor, then introducing sulfur dioxide gas into the reactor to replace the air in the reactor, so that the reactor is in a sulfur dioxide protective atmosphere, and reacting at 15°C for 4 hours. During the reaction, sulfur dioxide is continuously introduced to maintain the reaction pressure in the reactor at 0.02 MPa. After the reaction is completed, copper slag and decoppering liquid are obtained through solid-liquid separation, and the copper slag is returned to the copper smelting system to recover cathode copper; wherein, the molar ratio of sulfur in the pyrrhotite to the total amount of copper in the waste acid is 1.3:1;

[0047] S2: H2S gas is introduced into the decoppering solution obtained in step S1, and the reaction is carried out at 5°C for 1 hour. After the reaction is completed, arsenic sulfide slag and decoppering solution are obtained through solid-liquid separation. The arsenic sulfide slag is returned to the arsenic smelting system to recover arsenic trioxide. The decoppering solution is passed through a neutralization system to obtain ferric calcium slag and neutralization water. The ferric calcium slag is returned to the copper smelting system, and the neutralization water is reused industrially. The molar ratio of sulfur in the H2S gas to the total amount of arsenic in the decoppering solution is 1.7:1.

[0048] Example 3

[0049] A method for comprehensive recovery of valuable elements from non-ferrous smelting waste acid, wherein:

[0050] Non-ferrous smelting waste acid comes from the acidic wastewater produced by washing sulfur-containing flue gas in non-ferrous smelting. Its main components are: As content 10.57g / L, Cu content 2.39g / L, and acidity (pH) 1.2.

[0051] The steps are as follows:

[0052] S1: Adding waste acid and pyrrhotite with a mesh size of less than 200 mesh into a reactor, then introducing sulfur dioxide gas into the reactor to displace the air in the reactor, so that the reactor is in a sulfur dioxide protective atmosphere, and reacting at 25°C for 2 hours. During the reaction, sulfur dioxide is continuously introduced to maintain the reaction pressure in the reactor at 0.01 MPa. After the reaction is completed, copper slag and decoppering liquid are obtained through solid-liquid separation, and the copper slag is returned to the copper smelting system to recover cathode copper; wherein, the molar ratio of sulfur in the pyrrhotite to the total amount of copper in the waste acid is 1.1:1;

[0053] S2: H2S gas is introduced into the decoppering solution obtained in step S1, and the reaction is carried out at 10°C for 0.5h. After the reaction is completed, arsenic sulfide slag and decoppering solution are obtained through solid-liquid separation. The arsenic sulfide slag is returned to the arsenic smelting system to recover arsenic trioxide. The decoppering solution is passed through a neutralization system to obtain ferric calcium slag and neutralization water. The ferric calcium slag is returned to the copper smelting system, and the neutralization water is reused industrially. The molar ratio of sulfur in the H2S gas to the total amount of arsenic in the decoppering solution is 1.8:1.

[0054] Comparative Example 1

[0055] Refer to Example 1, except that, in step S1, the reactor is in an inert gas protective atmosphere and sulfur dioxide is not introduced during the reaction. During the reaction, the inert gas is used to make the reaction pressure in the reactor 0.03 MPa.

[0056] test

[0057] The copper content in the copper removal solution obtained in step S1 of Examples 1 to 3 and Comparative Example 1, the arsenic content in the copper slag, the arsenic content in the arsenic removal solution obtained in step S2, and the copper and iron content in the arsenic sulfide slag were detected, and the results are shown in Table 1. The recovery rate of each valuable element in Examples 1 to 3 and Comparative Example 1 was calculated, and the results are shown in Table 2.

[0058] The copper and arsenic contents in the solution were tested with reference to the national standard "Determination of 32 elements in water quality by inductively coupled plasma optical emission spectrometry (HJ 776-2015)", and the copper, arsenic and iron contents in the slag were tested with reference to the "Determination of copper, iron, arsenic, zinc, cadmium, mercury and silver in mixture by inductively coupled plasma optical emission spectrometry (SN / T 5266-2020)".

[0059] Table 1 Element contents in copper removal solution, copper slag, arsenic removal solution and arsenic sulfide slag

[0060] Table 2 Recovery rate of valuable elements

[0061] As shown in Tables 1 and 2, by adopting the technical scheme of the present invention (Examples 1 to 3), Cu in the copper removal solution is ≤0.10 mg / L, As in the copper slag is ≤0.10 wt%, and Cu in the arsenic sulfide slag is ≤0.05 wt%, and the Cu recovery rate is more than 97%, and the As recovery rate is more than 90%; in Comparative Example 1, the Cu content in the copper removal solution is 652.36 mg / L, the As content in the copper slag is 2.54 wt%, and the Cu content in the arsenic sulfide slag is 1.95 wt%, and the Cu recovery rate is only 83.91%, and the As recovery rate is only 88.91%; this indicates that the introduction of sulfur dioxide during copper precipitation can effectively inhibit the reaction between sulfur and arsenic in pyrrhotite, thereby realizing the separation of copper and arsenic in waste acid.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for comprehensive recovery of valuable elements from non-ferrous smelting waste acid, characterized in that: The steps include: S1: Mixing the waste acid with pyrrhotite, reacting them in a sulfur dioxide atmosphere, and then obtaining copper slag and decoppering liquid through solid-liquid separation; S2: introducing H2S gas into the copper removal solution obtained in step S1; after the reaction, performing solid-liquid separation to obtain arsenic sulfide slag and arsenic removal solution.

2. The method according to claim 1, characterized in that In step S1, the mesh size of the pyrrhotite is less than 200 meshes.

3. The method according to claim 1, characterized in that In step S1, the reaction temperature is 5-25° C., and the reaction time is 2-6 h.

4. The method according to claim 1, wherein In step S1, the molar ratio of sulfur in pyrrhotite to the total amount of copper in the waste acid is (1.1-1.5):

1.

5. The method according to claim 1, characterized in that In step S1, during the reaction, sulfur dioxide is continuously introduced to maintain the reaction pressure at a slightly positive pressure, wherein the slightly positive pressure is 0.01-0.03 MPa.

6. The method according to claim 1, characterized in that In step S1, the copper slag is returned to the copper smelting system to recover copper.

7. The method according to claim 1, characterized in that In step S2, the molar ratio of sulfur in the H2S gas to the total amount of arsenic in the copper removal solution is (1.5-1.8):

1.

8. The method according to claim 1, characterized in that In step S2, the reaction temperature is 5-25° C., and the reaction time is 0.5-2 h.

9. The method according to claim 1, characterized in that In step S2, the arsenic sulfide slag is returned to the arsenic smelting system to recover arsenic.

10. The method according to claim 1, characterized in that In step S2, the arsenic removal liquid is passed through a neutralization system to obtain ferro-calcium slag and neutralization water. The ferro-calcium slag is returned to the copper smelting system, and the neutralization water is reused industrially.

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