Synergistic recycling method for soot containing bromine and heavy metals

Abstract

The invention discloses a synergistic recycling method for soot containing bromine and heavy metals, and belongs to the technical field of treatment of hazardous wastes containing bromine and heavy metals. The method comprises the following steps: S1, coordination leaching: carrying out two-section countercurrent leaching on the soot by adopting an NH4Br solution; s2, reduction precipitation, wherein a reducing agent is added step by step to convert copper into CuBr precipitation; s3, oxidizing leaching is conducted, specifically, an oxidizing agent is added step by step to convert CuBr into a CuBr2 solution; s4, extraction and reverse extraction: recovering a zinc-containing ammonia solution by using an amine extraction agent; s5, transformation circulation is carried out, and lead is converted into PbCO3 slag through carbonate; and reusing the transformed liquid and the membrane concentrated water of the raffinate as the NH4Br leaching agent. The method provided by the invention realizes in-situ cyclic utilization of bromine and synergistic high-valued recovery of copper, zinc, lead and bromine, and has the advantages of mild process conditions, low medicament consumption, no secondary pollution, high product purity and the like.

Description

Technical Field

[0001] This invention relates to a method for the resource utilization of bromine-containing and heavy metal-containing flue dust, belonging to the field of hazardous waste treatment technology containing bromine and heavy metals. Background Technology

[0002] With the rapid development of electronic information technology, the annual generation of waste electronic equipment (such as waste circuit boards) continues to rise, and its incineration process inevitably produces a large amount of bromine-containing heavy metal ash. The main components of this type of ash include high concentrations of copper, zinc, lead, and bromine, with the bromine mainly originating from brominated flame retardants (BFRs) added to the circuit boards. Improper disposal of this ash not only results in a serious waste of valuable metal resources such as copper, zinc, and lead, but also causes complex pollution of soil, water bodies, and the atmosphere due to the volatility of bromine (such as the formation of HBr gas) and the biotoxicity of heavy metals, posing a significant threat to the ecological environment and human health.

[0003] Currently, the treatment technology for bromine-containing heavy metal flue dust mainly relies on traditional acid leaching or high-temperature incineration processes. Existing patents mostly focus on the recovery of single metals and have not established a synergistic recycling system for bromine and heavy metals. Bromine resources are difficult to recycle and manage in a closed loop, and there is a lack of in-situ resource utilization synergy mechanism, resulting in a disconnect between the recovery paths of bromine resources and metal resources, and making it impossible to achieve the synergistic high-value utilization of "bromine-metal".

[0004] Therefore, there is an urgent need to develop a new process that can realize the in-situ recycling of bromine (avoiding the loss of bromine resources) and the high-value recovery of heavy metals (simultaneous and efficient extraction of copper, zinc, and lead), construct a closed-loop recycling path for bromine, and solve the technical problem of the synergistic resource utilization of hazardous waste containing bromine and heavy metals. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a synergistic resource recovery method for bromine-containing and heavy metal-containing flue dust, which does not require high temperature and high pressure, has mild process conditions, no secondary pollution, low reagent consumption, and can realize in-situ recycling of bromine resources and synergistic high-value recovery of bromine and heavy metals.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for the synergistic resource utilization of bromine-containing and heavy metal-containing flue dust, comprising the following steps:

[0007] S1. Coordination leaching: The flue ash is subjected to a first-stage leaching, and the leaching solution and residue are obtained by filtration. NH4Br solution is added to the residue for a second-stage leaching, and the liquid-to-solid ratio of NH4Br solution to flue ash is controlled at 3-6:1, and the leaching pH is 4.5-5.2. The residue and residue are obtained by filtration. The second-stage leaching solution is returned to the first-stage leaching.

[0008] The purpose of coordination leaching is to achieve the separation of Cu, Zn, and Pb by selectively leaching Cu and Zn with NH4Br solution. Employing a two-stage countercurrent leaching method can effectively reduce reagent consumption and increase the leaching rates of Cu and Zn. Controlling the liquid-solid ratio of NH4Br solution to flue gas to 3–6:1 ensures high Cu and Zn leaching rates while reducing the volume of subsequent leachate treatment. Maintaining the pH at 4.5–5.2 ensures high Cu and Zn leaching rates while preventing the volatilization of NH4Br solution.

[0009] S2, Reduction Precipitation: Add reducing agent I and pure water to the first-stage leachate and stir to react. Control the addition and reaction time to 1-2 hours, the reaction temperature to 5℃-15℃, and the volume ratio of pure water to the first-stage leachate to 1-2:1. After the reaction is completed, continue to add reducing agent II and stir to react. Control the addition and reaction time to 0.5-1 hours. Filter to obtain reduction residue and reduced liquid.

[0010] The purpose of reduction precipitation is to remove Cu from a portion of the leachate. 2+ and CuBr4 3- The copper-bromine complex is converted into CuBr precipitate (reduction residue), thus separating Cu and Zn. A stepwise addition of reducing agent I and reducing agent II improves reduction precipitation efficiency and reduces reducing agent consumption. Adding pure water to the first-stage leachate and controlling the volume ratio of pure water to the first-stage leachate at 1–2:1 reduces the Br concentration in the solution, decreases the stability of the copper-bromine complex, and creates favorable conditions for CuBr precipitate formation. Controlling the reaction temperature at 5℃–15℃ reduces the solubility of the copper-bromine complex, promoting CuBr precipitate formation.

[0011] S3. Oxidative leaching: Oxidizing agent I is continuously added to the reducing residue and the reaction is stirred. The addition and reaction time are controlled to be 1-2 hours. After the reaction is completed, oxidizing agent II is continuously added and the reaction is stirred. The addition and reaction time are controlled to be 0.5-1 hours to obtain CuBr2 solution.

[0012] The purpose of oxidative leaching is to convert the CuBr precipitate in the reduction residue into a CuBr2 solution, thereby achieving synergistic high-value recovery of Cu and Br. By employing a stepwise, continuous addition of oxidant I and oxidant II, the oxidation efficiency is improved, oxidant decomposition is avoided, oxidant consumption is reduced, and secondary pollution is minimized.

[0013] S4. Extraction and back-extraction: Add an amine extractant to the reduced solution and stir to react, obtaining raffinate and extract. Back-extract the extract with an ammonia solution to obtain a zinc-containing ammonia solution and back-extraction solution; the back-extraction solution is recycled as an extractant.

[0014] The purpose of extraction-back-extraction is to recover Zn from the reduced solution in the form of a zinc-containing ammonia solution using amine extractants, thereby achieving the separation of Zn and Br.

[0015] S5. Transformation cycle: Add a transforming agent to the second-stage leaching residue and stir to react. Control the liquid-solid ratio of the transforming agent to the second-stage leaching residue to be 1-2:1 to obtain the transformed liquid and lead slag. The raffinate is concentrated by membrane to obtain fresh water and concentrated water. The fresh water is recycled as pure water to step S2, and the transformed liquid and concentrated water are recycled as NH4Br solution to step S1.

[0016] The purpose of the transformation cycle is to separate Pb and Br to obtain easily treatable and recyclable lead slag (PbCO3 precipitate). Controlling the liquid-solid ratio of the transforming agent to the secondary leaching residue to 1-2:1 helps to improve the utilization rate of the transforming agent and inhibit its decomposition.

[0017] The transformed liquid and concentrated water are reused as NH4Br solution, realizing the recycling of NH4Br within the system and minimizing reagent costs.

[0018] Furthermore, the mass percentage of Cu in the flue ash is 15%–30%, the mass percentage of Zn is 5%–15%, the mass percentage of Br is 22%–38%, and the mass percentage of Pb is 5%–10%. The highest Cu and Br contents in the flue ash form the basis for the synergistic high-value recovery of Cu and Br in this application.

[0019] Furthermore, in step S1, the molar concentration of NH4Br in the second leaching step is 3.6–5.2 mol / L. The key to the second leaching is to utilize the strong coordination ability between high-concentration Br and Cu to achieve efficient Cu leaching under slightly acidic pH (4.5–5.2). If the molar concentration of NH4Br is lower than 3.6 mol / L, the Cu leaching rate will be significantly reduced. If the molar concentration of NH4Br is higher than 5.2 mol / L, the coordination between Br and Cu will be too stable, which is not conducive to the formation of CuBr precipitate in the subsequent step S2.

[0020] Furthermore, in step S1, the first leaching temperature is 35–50°C, and the second leaching temperature is 10–25°C. Controlling the second leaching temperature to 10–25°C helps avoid decomposition or volatilization caused by uneven local reactions during NH4Br addition, thus improving the utilization efficiency of NH4Br. When the second-stage leachate is reused in the first-stage leaching, most of the Br in the second-stage leachate has already been converted to CuBr4. 3- When the copper-bromine complex is in its final form, the Br in the solution is relatively stable. At this point, controlling the first leaching temperature to 35–50 °C can further improve the leaching rate of Cu and Zn and prevent the decomposition or volatilization of NH4Br.

[0021] Furthermore, in step S2, reducing agent I is copper powder with a particle size of 80–250 μm, and the molar ratio of copper powder to copper in the first-stage leaching solution is 0.5–0.7:1. Step S2 first adds reducing agent I and controls the molar ratio of copper powder to copper in the first-stage leaching solution to 0.5–0.7:1 to utilize the reducing and nucleation-inducing effects of copper powder to promote the formation of CuBr crystal nuclei. Then, the adsorption and precipitation of Cu and Br on the CuBr surface lays the foundation for the function of reducing agent II. Controlling the copper powder particle size to 80–250 μm allows for a moderate reduction reaction rate, preferentially reducing Cu… + This prevents the formation of CuBr and avoids the generation of byproducts.

[0022] Furthermore, in step S2, reducing agent II is ascorbic acid, and the molar ratio of ascorbic acid to copper in the first leaching solution is 0.15–0.25:1. After adding copper powder in step S2, ascorbic acid is added next. Utilizing the surface of the already formed CuBr as a reaction interface further enhances the reduction and precipitation effect, improves the utilization rate of reducing agent I and reducing agent II, and simultaneously increases the precipitation rate of Cu.

[0023] Furthermore, in step S3, the oxidant I is one or more of HBr and Br2, and the molar ratio of Br in the oxidant I to Cu in the reduction slag is 1 to 1.1:1. Step S3 first adds oxidant I to replenish the Br required for the oxidation process and to convert the CuBr precipitate in the reduction slag into CuBr4. 3- These complexes promote the precipitation-dissolution-oxidation process, laying the foundation for oxidant II to play its role.

[0024] Furthermore, in step S3, oxidant II is one or more of H2O2 and O3, and the molar ratio of oxidant II to Cu in the reducing slag is 0.2–0.5:1. After adding oxidant I in step S3, oxidant II is added next to oxidant II, which reacts with the already formed CuBr4... 3- Further oxidation of the complex enhances the CuBr precipitation-dissolution-oxidation conversion process, improving the utilization rate of oxidant I and oxidant II and the Cu recovery rate.

[0025] Furthermore, in step S4, the amine extractant is one of a trialkyl tertiary amine or methyltrialkylammonium chloride, the extraction pH is 2.7–3.5, and the ammonia solution concentration is 0.5–1 mol / L. The reduced solution contains Zn and NH4+. + ,Br - Coexistence, using amine extractants for ZnBr4 2- Extraction with anionic complexes was used to separate and recover Zn. Controlling the extraction pH to 2.7–3.5 helps to preserve ZnBr4. 2- The stable presence of anions ensures efficient extraction of Zn and purity of the zinc-containing ammonia solution.

[0026] Furthermore, in step S5, the conversion agent is one or more of NH4HCO3 and (NH4)2CO3, and the molar ratio of C in the conversion agent to Pb in the secondary leaching residue is 1.1–1.3:1. NH4HCO3 and (NH4)2CO3 are easily decomposed. By controlling the liquid-to-solid ratio of the conversion agent to the secondary leaching residue to be 1–2:1, and the molar ratio of C in the conversion agent to Pb in the secondary leaching residue to be 1.1–1.3:1, the conversion reaction is made into a solid-liquid reaction, effectively inhibiting the decomposition of NH4HCO3 and (NH4)2CO3, improving the conversion cycle efficiency, and reducing reagent consumption.

[0027] Compared with the prior art, the present invention has at least the following advantages:

[0028] 1. Achieve in-situ recycling of bromine and synergistic recovery of bromine and heavy metals: In step S1, bromine is converted into copper bromine complexes by selective coordination leaching of copper with high concentration of NH4Br and enters the leaching solution; in steps S2 to S3, bromine is recovered in high value as CuBr2 product through stepwise reduction and stepwise oxidation; finally, NH4Br in the transformed solution and raffinate is enriched and reused in the leaching process, and bromine is recycled throughout the entire process.

[0029] 2. Mild reaction conditions, low reagent cost, and environmentally friendly: The entire process does not require high temperature and high pressure, nor concentrated acids and alkalis. Most of the added reagents enter the product or are recycled within the system, significantly reducing reagent costs and effectively avoiding the generation of secondary pollution such as HBr gas.

[0030] 3. No impurity ions are introduced, resulting in high product purity and high recovery rate: No impurity ions such as chloride ions, sulfate ions, and sodium ions are introduced. Br, Cu, Zn, and Pb in the flue ash are ultimately recovered in easily treatable forms such as high-purity CuBr2 solution, high-purity zinc-containing ammonia solution, and PbCO3 residue. The CuBr2 solution contains a CuBr2 concentration of no less than 480 g / L, a Pb concentration of no more than 20 mg / L, and a Zn concentration of no more than 50 mg / L. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a process flow diagram of the synergistic resource utilization process of bromine-containing and heavy metal-containing flue dust in Embodiment 1 of the present invention. Detailed Implementation

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0036] The soot was taken from a solid waste incinerator of a company in Honghe, Yunnan Province. The mass percentage of Cu was 25.8%, Zn was 8.3%, Br was 29.6%, and Pb was 6.1%.

[0037] During initial startup, there is no second-stage leachate. Therefore, in the following examples, a second-stage leaching is performed using soot and NH4Br solution, and the resulting second-stage leachate is then used for a first-stage leaching. For simplicity, the material recycling steps for the first-stage and second-stage leaching are not described separately in step S1.

[0038] Example 1

[0039] S1. 10 kg of flue gas was leached in two stages using 30 L of 3.6 mol / L NH4Br solution. The liquid-to-solid ratio of NH4Br solution to flue gas was 3:1. The leaching temperature for the first stage was controlled at 35℃, and the pH for the second stage was 5.2. The leaching temperature for the second stage was 10℃. 29.68 L of first-stage leachate and 1103.1 g of second-stage leaching residue (based on dry residue) were obtained.

[0040] S2. Add 1264.2g of copper powder with a particle size of 80μm and 29.68L of pure water to the first-stage leachate and stir to react. Control the addition and reaction time to 1h, the reaction temperature to 5℃, the molar ratio of copper powder to copper in the first-stage leachate to 0.5:1, and the volume ratio of pure water to the first-stage leachate to 1:1. After the reaction is completed, continue to add 1738.3g of ascorbic acid and stir to react. The molar ratio of ascorbic acid to copper in the first-stage leachate to 0.25:1, control the addition and reaction time to 0.5h, and obtain 5688.9g of reducing residue (dry residue) and 56.7L of reduced solution.

[0041] S3. 3200.1g HBr was continuously added to the reducing residue and the mixture was stirred to react. The molar ratio of Br to Cu in the reducing residue was 1:1. The addition and reaction time were controlled to be 1h. After the reaction was completed, 671.6g H2O2 was continuously added and the mixture was stirred to react. The molar ratio of H2O2 to Cu in the reducing residue was 0.5:1. The addition and reaction time were controlled to be 0.5h. 18L of solution with CuBr2 concentration of 491.6g / L was obtained.

[0042] S4. Extraction and Back-extraction: Add 56.7L of 20% trialkyl tertiary amine to the reduced solution and stir to react. Control the extraction pH to 2.7 to obtain raffinate and extract. Back-extract the extract with 0.5mol / L ammonia solution to obtain 5L of zinc-containing ammonia solution with a zinc concentration of 163g / L and back-extraction solution. The back-extraction solution is recycled as an extractant.

[0043] S5. Transformation Cycle: Add 1.1L of NH4HCO3 solution to the second-stage leaching residue and stir the reaction. Control the liquid-solid ratio of NH4HCO3 to the second-stage leaching residue to be 1:1 and the molar ratio of NH4HCO3 to Pb in the second-stage leaching residue to be 1.1:1 to obtain the transformed liquid and 778.9g of lead slag.

[0044] The raffinate was concentrated by reverse osmosis to obtain 29.68 L of fresh water and concentrated water. The fresh water was reused as pure water in step S2, and the transformed liquid and concentrated water were reused as NH4Br solution in step S1. A small amount of new NH4Br solution was added according to the loss, and steps S1 to S5 were repeated.

[0045] Testing revealed that in a 5L zinc-containing ammonia solution, the zinc concentration was 163g / L, the copper concentration was 51mg / L, and the Zn recovery rate was 98.5%; in an 18L CuBr2 solution, the CuBr2 concentration was 491.6g / L, the Pb concentration was 15mg / L, the Zn concentration was 38mg / L, and the Cu recovery rate was 98.0%; and in a 778.9g lead slag solution, the Pb recovery rate was 98.2%. The Br recovery rate in the flue ash was 97.5%.

[0046] Example 2

[0047] S1. 10 kg of flue gas was leached in two stages using 60 L of 5.2 mol / L NH4Br solution. The liquid-to-solid ratio of NH4Br solution to flue gas was 6:1. The leaching temperature for the first stage was controlled at 50℃, and the pH for the second stage was 4.5. The leaching temperature for the second stage was controlled at 25℃. 59.68 L of first-stage leachate and 1092.3 g of second-stage leachate residue (based on dry residue) were obtained.

[0048] S2. Add 1773.5g of copper powder with a particle size of 250μm and 119.35L of pure water to the first-stage leaching solution and stir to react. Control the addition and reaction time to be 2h, the reaction temperature to be 15℃, the molar ratio of copper powder to copper in the first-stage leaching solution to be 0.7:1, and the volume ratio of pure water to the first-stage leaching solution to be 2:1. After the reaction is completed, continue to add 1741.8g of ascorbic acid and stir to react. The molar ratio of ascorbic acid to copper in the first-stage leaching solution to be 0.25:1, and control the addition and reaction time to be 1h to obtain 5700.5g of reducing residue (based on dry residue) and 176.8L of reduced solution.

[0049] S3. 3483.6g of Br2 was continuously added to the reduction residue and the mixture was stirred to react. The molar ratio of Br to Cu in the reduction residue was 1.1:1. The addition and reaction time were controlled at 2h. After the reaction was completed, 665.1g of O3 was continuously added and the mixture was stirred to react. The molar ratio of O3 to Cu in the reduction residue was 0.35:1. The addition and reaction time were controlled at 1h. 18.2L of solution with a CuBr2 concentration of 487.2g / L was obtained.

[0050] S4. Extraction and Back-extraction: Add 176.8 L of 20% methyltrialkylammonium chloride to the reduced solution and stir to react. Control the extraction pH to 3.5 to obtain raffinate and extract. Back-extract the extract with 1 mol / L ammonia solution to obtain 4.9 L of zinc-containing ammonia solution with a zinc concentration of 167 g / L and back-extraction solution. The back-extraction solution is recycled as an extractant.

[0051] S5. Transformation Cycle: Add 2.2L of (NH4)2CO3 solution to the second-stage leaching residue and stir to react. Control the liquid-solid ratio of the transforming agent to the second-stage leaching residue to be 2:1, and the molar ratio of (NH4)2CO3 to Pb in the second-stage leaching residue to be 1.3:1, to obtain the transformed liquid and 771.1g of lead slag.

[0052] The raffinate was concentrated by reverse osmosis to obtain 119.35L of fresh water and concentrated water. The fresh water was reused as pure water in step S2, and the transformed liquid and concentrated water were reused as NH4Br solution in step S1. A small amount of new NH4Br solution was added according to the loss, and steps S1 to S5 were repeated.

[0053] Analysis revealed the following results: A 4.9 L zinc-containing ammonia solution had a zinc concentration of 167 g / L, a copper concentration of 55 mg / L, and a Zn recovery rate of 98.6%; an 18.2 L CuBr2 solution had a CuBr2 concentration of 487.2 g / L, a Pb concentration of 18 mg / L, a Zn concentration of 41 mg / L, and a Cu recovery rate of 98.2%; and 771.1 g of lead slag had a Pb recovery rate of 98.0%. The Br recovery rate in the flue ash was 97.6%.

[0054] Example 3

[0055] S1. 10 kg of flue gas was leached in two stages using 45 L of 4.4 mol / L NH4Br solution. The liquid-to-solid ratio of NH4Br solution to flue gas was 4.5:1. The leaching temperature for the first stage was controlled at 42℃, and the pH for the second stage was 4.8. The leaching temperature for the second stage was 18℃. 44.68 L of first-stage leachate and 1097.7 g of second-stage leaching residue (based on dry residue) were obtained.

[0056] S2. Add 1521.7g of copper powder with a particle size of 165μm and 67.01L of pure water to the first-stage leaching solution and stir to react. Control the addition and reaction time to 1h, the reaction temperature to 5℃, the molar ratio of copper powder to copper in the first-stage leaching solution to 0.6:1, and the volume ratio of pure water to the first-stage leaching solution to 1.5:1. After the reaction is completed, continue to add 1042.6g of ascorbic acid and stir to react. The molar ratio of ascorbic acid to copper in the first-stage leaching solution to 0.15:1, control the addition and reaction time to 0.5h, and obtain 5706.3g of reducing residue (based on dry residue) and 108.6L of reduced solution.

[0057] S3. 3370.3g HBr was continuously added to the reducing residue and the mixture was stirred. The molar ratio of Br to Cu in the reducing residue was 1.05:1. The addition and reaction time were controlled at 1h. After the reaction was completed, 471.6g H2O2 was continuously added and the mixture was stirred. The molar ratio of H2O2 to Cu in the reducing residue was 0.5:1. The addition and reaction time were controlled at 0.5h. 18.1L of solution with a CuBr2 concentration of 490.4g / L was obtained.

[0058] S4. Extraction and Back-extraction: Add 108.6 L of 20% trialkyl tertiary amine to the reduced solution and stir to react. Control the extraction pH to 3.1 to obtain raffinate and extract. Back-extract the extract with 0.75 mol / L ammonia solution to obtain 5.4 L of zinc-containing ammonia solution with a zinc concentration of 151 g / L and back-extraction solution. The back-extraction solution is recycled as an extractant.

[0059] S5. Transformation Cycle: Add 1.6L of NH4HCO3 solution to the secondary leaching residue and stir the reaction. Control the liquid-solid ratio of NH4HCO3 to the secondary leaching residue to be 1.5:1 and the molar ratio of NH4HCO3 to Pb in the secondary leaching residue to be 1.2:1 to obtain the transformed liquid and 771.9g of lead slag.

[0060] The raffinate was concentrated by reverse osmosis to obtain 67.01L of fresh water and concentrated water. The fresh water was reused as pure water in step S2, and the transformed liquid and concentrated water were reused as NH4Br solution in step S1. A small amount of new NH4Br solution was added according to the loss, and steps S1 to S5 were repeated.

[0061] Analysis revealed the following results: A zinc-containing ammonia solution (volume 5.4 L) had a zinc concentration of 151 g / L, a copper concentration of 48 mg / L, and a Zn recovery rate of 98.4%; a CuBr2 solution (volume 18.1 L) had a CuBr2 concentration of 490.4 g / L, a Pb concentration of 16 mg / L, a Zn concentration of 35 mg / L, and a Cu recovery rate of 98.3%; lead slag (mass 771.9 g) had a Pb recovery rate of 98.1%. The Br recovery rate in the flue ash was 97.3%.

[0062] Example 4

[0063] S1. 10 kg of flue gas was leached in two stages using 60 L of 5.2 mol / L NH4Br solution. The liquid-to-solid ratio of NH4Br solution to flue gas was 6:1. The leaching temperature for the first stage was controlled at 50℃, and the pH for the second stage was 4.5. The leaching temperature for the second stage was controlled at 25℃. 59.68 L of first-stage leachate and 1098.8 g of second-stage leachate residue (based on dry residue) were obtained.

[0064] S2. Add 1264.2 g of copper powder with a particle size of 80 μm and 59.68 L of pure water to the first-stage leaching solution and stir to react. Control the addition and reaction time to be 1.5 h, the reaction temperature to be 10 °C, the molar ratio of copper powder to copper in the first-stage leaching solution to be 0.5:1, and the volume ratio of pure water to the first-stage leaching solution to be 1:1. After the reaction is completed, continue to add 1390.6 g of ascorbic acid and stir to react. The molar ratio of ascorbic acid to copper in the first-stage leaching solution to be 0.20:1, and control the addition and reaction time to be 0.5 h, to obtain 5688.9 g of reducing residue (based on dry residue) and 116.3 L of reduced solution.

[0065] S3. 3160.5g of Br2 was continuously added to the reducing residue and the mixture was stirred to react. The molar ratio of Br to Cu in the reducing residue was 1:1. The addition and reaction time were controlled at 1.5h. After the reaction was completed, 379.3g of O3 was continuously added and the mixture was stirred to react. The molar ratio of O3 to Cu in the reducing residue was 0.2:1. The addition and reaction time were controlled at 0.5h. 18.3L of solution with a CuBr2 concentration of 483.5g / L was obtained.

[0066] S4. Extraction and Back-extraction: Add 116.3 L of 20% methyltrialkylammonium chloride to the reduced solution and stir to react. Control the extraction pH to 2.7 to obtain raffinate and extract. Back-extract the extract with 0.75 mol / L ammonia solution to obtain 5.1 L of zinc-containing ammonia solution with a zinc concentration of 160 g / L and back-extraction solution. The back-extraction solution is recycled as an extractant.

[0067] S5. Transformation Cycle: Add 1.6L of (NH4)2CO3 solution to the secondary leaching residue and stir the reaction. Control the liquid-solid ratio of the transforming agent to the secondary leaching residue to be 1.5:1, and the molar ratio of (NH4)2CO3 to Pb in the secondary leaching residue to be 1.1:1. The transformed liquid and 769.5g of lead slag are obtained.

[0068] The raffinate was concentrated by reverse osmosis to obtain 59.68 L of fresh water and concentrated water. The fresh water was reused as pure water in step S2, and the transformed liquid and concentrated water were reused as NH4Br solution in step S1. A small amount of new NH4Br solution was added according to the loss, and steps S1 to S5 were repeated.

[0069] Analysis revealed the following results: A 5.1 L zinc-containing ammonia solution had a zinc concentration of 160 g / L and a copper concentration of 50 mg / L, with a Zn recovery rate of 98.2%; a 18.3 L CuBr2 solution had a CuBr2 concentration of 483.5 g / L, a Pb concentration of 19 mg / L, and a Zn concentration of 42 mg / L, with a Cu recovery rate of 98.0%; and 769.5 g of lead slag had a Pb recovery rate of 97.8%. The Br recovery rate in the flue ash was 96.9%.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that: S1, 10 kg of soot is leached in one stage and two stages using 30 L of 6.0 mol / L NH4Br solution.

[0072] The results showed that the CuBr2 solution volume was 18L, the CuBr2 concentration was 457.5g / L, the Pb concentration was 16mg / L, the Zn concentration was 37mg / L, and the Cu recovery rate was 91.2%.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that: S1, 10 kg of soot is leached in one stage and two stages using 30 L of 3.0 mol / L NH4Br solution.

[0075] The CuBr2 solution volume was 18 L, the CuBr2 concentration was 420.4 g / L, the Pb concentration was 14 mg / L, the Zn concentration was 35 mg / L, and the Cu recovery rate was 83.8%. The mass of the copper-lead mixed slag was 1.71 kg, of which 0.42 kg contained copper.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that: S1, the second-stage leaching temperature is controlled at 50°C.

[0078] The CuBr2 solution volume was 18 L, the CuBr2 concentration was 431.9 g / L, the Pb concentration was 18 mg / L, the Zn concentration was 39 mg / L, and the Cu recovery rate was 86.1%. The mass of the copper-lead mixed slag was 1.58 kg, of which 0.36 kg contained copper.

[0079] Comparative Example 4

[0080] The difference from Example 1 is as follows: S2, reduction precipitation: reducing agent I, reducing agent II and pure water are added to the first-stage leachate at the same time and stirred to react. The addition and reaction time are controlled to be 1.5 to 3 hours, the reaction temperature is 5℃ to 15℃, and the volume ratio of pure water to the first-stage leachate is 1 to 2:1. After the reaction is completed, the residue and the reduced liquid are obtained by filtration.

[0081] The CuBr2 solution had a volume of 18 L, a CuBr2 concentration of 405.8 g / L, a Pb concentration of 20 mg / L, a Zn concentration of 41 mg / L, and a Cu recovery rate of 80.9%. The zinc-containing ammonia solution had a volume of 5 L, a zinc concentration of 163 g / L, and a copper concentration of 2.2 g / L.

[0082] Comparative Example 5

[0083] The difference from Example 1 is as follows: S3, Oxidative leaching: Oxidizing agent I and oxidizing agent II are continuously added to the reducing residue and stirred to react. The addition and reaction time are controlled to be 1.5 to 3 hours to obtain CuBr2 solution;

[0084] The analysis showed that the CuBr2 solution volume was 18L (containing 1.48kg of precipitate), the CuBr2 concentration was 373.24g / L, the Pb concentration was 19mg / L, the Zn concentration was 39mg / L, and the Cu recovery rate was 74.4%.

[0085] Comparative Example 6

[0086] The difference from Example 1 is that: S2, 1264.2g of copper powder with a particle size of 80μm and 10L of pure water are added to a section of leachate and stirred to react;

[0087] The CuBr2 solution had a volume of 18 L, a CuBr2 concentration of 416.8 g / L, a Pb concentration of 17 mg / L, a Zn concentration of 35 mg / L, and a Cu recovery rate of 83.1%. The zinc-containing ammonia solution had a volume of 5 L, a zinc concentration of 163 g / L, and a copper concentration of 1.9 g / L.

[0088] Based on Examples 1-4 and Comparative Examples 1-6, it is evident that a decrease in the separation efficiency of copper in steps S1, S2, or S3 leads to a reduction in copper (bromine) recovery and affects further recovery of lead and zinc. Based on Examples 1 and Comparative Example 1, it is evident that if the NH4Br solution concentration is higher than 5.2 mol / L, it affects the formation of CuBr, reducing the copper (bromine) recovery rate. Based on Examples 1 and Comparative Example 2, it is evident that if the NH4Br solution concentration is lower than 3.6 mol / L, it affects the copper leaching efficiency, with some copper entering the lead slag, reducing the copper (bromine) recovery rate. Based on Examples 1 and Comparative Example 3, it is evident that failure to control the second-stage leaching temperature leads to the decomposition and loss of NH4Br, reducing the copper (bromine) recovery rate. Based on Examples 1 and Comparative Example 4, it is evident that failure to control the order of adding reducing agent I and reducing agent II leads to incomplete reduction and precipitation, with some copper entering the zinc-containing ammonia solution, reducing the copper (bromine) recovery rate. Based on Examples 1 and 5, it can be seen that if the order of adding oxidant I and oxidant II is not controlled, incomplete oxidation leaching will occur, reducing the recovery rate of copper (bromine). Based on Examples 1 and 6, it can be seen that if the amount of pure water added in step S2 is not controlled, the concentration of NH4Br will be too high, resulting in incomplete reduction precipitation and reducing the recovery rate of copper (bromine).

[0089] The above description of the disclosed embodiments enables those skilled in the art to experiment with or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for the synergistic resource utilization of bromine-containing and heavy metal-containing flue dust, characterized in that, Includes the following steps: S1. Coordination leaching: The flue ash is leached in one stage, and filtered to obtain a leachate and a leaching residue. NH4Br solution is added to the first-stage leaching residue for second-stage leaching, controlling the liquid-solid ratio of NH4Br solution to flue ash to be 3-6:1, and the leaching pH to be 4.5-5.

2. The residue is then filtered to obtain the second-stage leachate and the second-stage leaching residue. The second-stage leachate is then returned to the first-stage leaching. S2, Reduction Precipitation: Add reducing agent I and pure water to the first-stage leachate and stir to react. Control the addition and reaction time to be 1-2 hours, the reaction temperature to be 5-15℃, and the volume ratio of pure water to the first-stage leachate to be 1-2:

1. After the reaction is completed, continue to add reducing agent II and stir to react. Control the addition and reaction time to be 0.5-1 hours. Filter to obtain reduction residue and reduction liquid. S3. Oxidative leaching: Oxidizing agent I is continuously added to the reducing residue and the reaction is stirred. The addition and reaction time are controlled to be 1-2 hours. After the reaction is completed, oxidizing agent II is continuously added and the reaction is stirred. The addition and reaction time are controlled to be 0.5-1 hours to obtain CuBr2 solution. S4. Extraction and back-extraction: Add an amine extractant to the reduced solution and stir to react, obtaining raffinate and extract. Back-extract the extract with an ammonia solution to obtain a zinc-containing ammonia solution and back-extraction solution; the back-extraction solution is recycled as an extractant. S5. Transformation cycle: Add a transforming agent to the second-stage leaching residue and stir to react. Control the liquid-solid ratio of the transforming agent to the second-stage leaching residue to be 1-2:1 to obtain the transformed liquid and lead slag. The raffinate is concentrated by membrane to obtain fresh water and concentrated water. The fresh water is recycled as pure water to step S2, and the transformed liquid and concentrated water are recycled as NH4Br solution to step S1.

2. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, The mass percentage of Cu in the flue ash is 15%–30%, the mass percentage of Zn is 5%–15%, the mass percentage of Br is 22%–38%, and the mass percentage of Pb is 5%–10%.

3. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S1, the molar concentration of the second leached NH4Br is 3.6–5.2 mol / L.

4. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S1, the first leaching temperature is 35-50°C, and the second leaching temperature is 10-25°C.

5. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S2, the reducing agent I is copper powder with a particle size of 80-250 μm, and the molar ratio of the copper powder to copper in the first leaching solution is 0.5-0.7:

1.

6. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S2, the reducing agent II is ascorbic acid, and the molar ratio of ascorbic acid to copper in the first leaching solution is 0.15 to 0.25:

1.

7. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S3, the oxidant I is one or more of HBr and Br2, and the molar ratio of Br in the oxidant I to Cu in the reducing slag is 1 to 1.1:

1.

8. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S3, the oxidant II is one or more of H2O2 and O3, and the molar ratio of the oxidant II to Cu in the reducing slag is 0.2 to 0.5:

1.

9. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S4, the amine extractant is one of trialkyl tertiary amine or methyltrialkylammonium chloride, the extraction pH is 2.7-3.5, and the concentration of the ammonia solution is 0.5-1 mol / L.

10. The method for synergistic resource utilization of bromine-containing and heavy metal-containing flue dust according to claim 1, characterized in that, In step S5, the transforming agent is one or more of NH4HCO3 and (NH4)2CO3, and the molar ratio of C to Pb in the second-stage leaching residue is 1.1 to 1.3:1.

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