A method for the extraction and purification of heavy metal sludge leachate

Abstract

The application provides a heavy metal sludge leaching solution extraction purification method, comprising the following steps: S1, mixing and clarifying the heavy metal sludge leaching solution and an extraction carrier solvent to obtain clean leaching solution and contaminated extraction carrier solvent, and sequentially feeding the clean leaching solution into a P204 extraction system, a P507 extraction system and a Cyanex272 extraction system to extract and remove impurities, finally obtaining a nickel sulfate solution and a cobalt sulfate solution; S2, mixing and clarifying the contaminated extraction carrier solvent and pure water to obtain contaminated water and clean extraction carrier solvent, recycling the clean extraction carrier solvent in step S1, and recycling the contaminated water after oil removal treatment or activated carbon device purification treatment. The application contacts the leaching solution with an organic solvent without an extraction agent before contacting the leaching solution with an extraction organic phase, can separate potential harmful substances dissolved in the organic phase from the leaching original solution, removes the impurities in advance, and avoids the influence of the harmful substances on the subsequent extraction process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydrometallurgy, and particularly relates to a heavy metal sludge leaching solution extraction and purification method. BACKGROUND

[0002] The electroplating industry produces a large amount of industrial wastewater, which contains a large amount of heavy metal ions. If the treatment standard is not reached, it will cause serious pollution to the environment. In the electroplating wastewater treatment process, heavy metal elements are transferred to sludge. Electroplating sludge is an inevitable solid waste, which belongs to hazardous waste, but it is rich in valuable metal elements such as copper, nickel, zinc and chromium in wastewater, and the heavy metals in electroplating sludge need to be recovered according to environmental protection requirements and the best recovery technology. The methods for recovering electroplating sludge mainly include pyrometallurgical process, hydrometallurgical process, combined process of pyrometallurgical roasting-hydrometallurgical leaching and biological method. Due to the high water content, low metal grade and complex composition of electroplating sludge, the pyrometallurgical process has the disadvantages of high energy consumption, large investment and low metal recovery rate, so the pyrometallurgical process is rarely used. The hydrometallurgical process is to leach the valuable metals in the electroplating sludge into the leaching solution under suitable leaching agent and leaching conditions, so as to realize preliminary separation. After the leaching solution is purified and the valuable metals are separated, a relatively pure metal ion solution can be obtained, and then metal extraction or metal product preparation can be carried out. The common hydrometallurgical process is to obtain a leaching solution by using acid leaching method, remove impurities or enrich the solution by extraction to obtain a pure solution, and then prepare a high-purity solution or crystal product by deep extraction.

[0003] Patent CN202111173136.9 discloses a process for recovering chromium, copper, nickel, and cobalt from electroplating sludge. The process involves dissolving electroplating sludge containing chromium, iron, copper, nickel, and cobalt in a strong acid solution and filtering it to obtain a filtrate containing chromium, iron, copper, nickel, and cobalt ions. After dilution, an alkaline solution is slowly added in stages with a gradient concentration to react and form a chromium hydroxide precipitate and a filtrate containing iron, copper, nickel, and cobalt ions. An alkaline solution is then slowly added to the filtrate until the pH reaches 4.50, and air is introduced to form an iron-containing precipitate and a filtrate containing copper, nickel, and cobalt ions. NaHCO3 solution is then slowly added in stages with a gradient concentration to react and form a copper carbonate precipitate and a filtrate containing nickel, cobalt ions, and a small amount of copper. Finally, through ion extraction and oil phase back-extraction, copper-containing, nickel-containing, and cobalt-containing solutions are obtained. Patent CN201510445046.9 discloses a method for recovering valuable metals from electroplating sludge to prepare cathode copper and battery-grade nickel sulfate. This method uses electroplating sludge as raw material, involves dissolving and leaching the sludge, preparing a mixed aqueous solution, dissolving it with concentrated acid to form a solution, and controlling the leaching rate of Cu and Ni in the solution to be ≥98.5%. Patent CN201410785448.9 discloses a method for the resource utilization of multiple metals from electroplating sludge. This method involves extracting copper from the electroplating sludge leachate, precipitating chromium in the raffinate to obtain chromium phosphate precipitate, removing phosphate ions with NaOH alkaline solution, filtering to obtain chromium hydroxide, which is then re-dissolved, evaporated, and crystallized to prepare basic chromium sulfate. The alkaline solution is recycled, and copper, nickel, and zinc are separated and recovered stepwise in the process. Patent CN202210964288.9 discloses a method for recovering magnesium oxide from a nickel-cobalt intermediate leaching solution. The method involves first extracting and enriching magnesium with an acidic phosphorus-containing extractant, then back-extracting with hydrochloric acid to obtain a high-concentration magnesium chloride solution. The magnesium chloride solution is then purified to remove Ni and Co impurities. The purified magnesium chloride solution is then pyrolyzed to obtain primary magnesium oxide and hydrogen chloride tail gas. The hydrogen chloride tail gas is washed and absorbed to produce dilute hydrochloric acid, which is returned to the extraction system. The magnesium oxide product from spray pyrolysis is then crushed, hydrated with pure water, and washed to transform into magnesium hydroxide. After solid-liquid separation, the washed solid residue is dried and calcined at high temperature to produce high-purity magnesium oxide. All of these patents involve acid leaching of electroplating sludge or similar materials, followed by separation and purification of metal ions in the leaching solution using extraction lines such as P204, P507, and Cyanex 272. However, in order to ensure that the wastewater meets the standards, electroplating wastewater treatment plants usually add organic substances such as sodium thiosulfate to the wastewater. As a result, the electroplating sludge contains more or less organic substances. If these organic substances enter the leachate during the leaching process and then come into contact with the extracted organic phase, it will inevitably cause organic phase poisoning, affect the separation ability of the extracted organic phase, and lead to unqualified products, affecting normal production.

[0004] In view of this, this application proposes a method for extraction and purification of heavy metal sludge leachate, which can separate potentially harmful substances dissolved in the organic phase from the leachate, thereby achieving the purpose of pre-removal of impurities and avoiding the influence of harmful substances on the subsequent extraction process. Summary of the Invention

[0005] To overcome the problems in existing technologies where the COD of organic matter in leachate is between 1000 and 10000 mg / L, or even higher, high concentrations of organic matter can severely disrupt the equilibrium of the metal extraction and separation system, causing emulsification of the organic phase and leading to extraction failure. Furthermore, direct adsorption with activated carbon results in the adsorption loss of valuable metal ions. Therefore, this invention aims to propose a method for the extraction and purification of heavy metal sludge leachate to solve these technical problems.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] A method for extracting and purifying heavy metal sludge leachate includes the following steps:

[0008] S1. The heavy metal sludge leachate is mixed and clarified with the extraction carrier solvent to obtain a clean leachate and a contaminated extraction carrier solvent. The clean leachate is then sequentially passed through the P204 extraction system, the P507 extraction system, and the Cyanex272 extraction system for extraction and impurity removal, finally yielding a nickel sulfate solution and a cobalt sulfate solution.

[0009] S2. The contaminated extraction carrier solvent is mixed with pure water for clarification to obtain contaminated water and clean extraction carrier solvent. The clean extraction carrier solvent is returned to step S1 for recycling. The contaminated water is recycled after being treated with oil removal or purified by an activated carbon device.

[0010] Through the above technical solution, the heavy metal sludge leachate in this application comes into contact with the extraction carrier solvent before contacting the extraction organic phase. This can separate potentially harmful substances dissolved into the organic phase from the leachate, achieving the purpose of pre-removal of impurities and avoiding the influence of harmful substances on the subsequent extraction process.

[0011] In a preferred embodiment, the clean leachate is passed into a P204 system for extraction and impurity removal, including the following sub-steps:

[0012] S111. The pH value of the clean leachate is finely adjusted to perform deep iron removal, and then filtered with a precision filter to obtain an iron-removed solution with a pH value of 3.5 to 4.0.

[0013] S112 and P204 organic phases are pumped from the storage tank into the extraction tank and successively undergo alkali saponification and nickel sulfate solution conversion. They are then subjected to multi-stage countercurrent extraction with the iron-removed liquid to obtain P204 raffinate and P204 supported organic phase.

[0014] After washing and back-extraction, the manganese, zinc, and copper in the S113 and P204 loaded organic phases are sent to the manganese-zinc-copper product recovery system in the back-extraction liquid, and the regenerated P204 organic phase is obtained. The regenerated P204 organic phase is returned to the extraction system in step S112 for reuse after magnesium removal, chlorine washing, and clarification.

[0015] The above technical solution can achieve the removal of impurities from the leachate and the regeneration of the organic phase of the P204 extractant.

[0016] In a preferred embodiment, the P204 raffinate is passed into the P507 extraction system for cobalt extraction, including the following sub-steps:

[0017] S121. The P204 raffinate is transported to the P507 extraction system to separate nickel and cobalt. Cobalt enters the P507 organic phase, while nickel remains in the raffinate. The nickel-containing raffinate is then sent to the next step of deep magnesium extraction.

[0018] S122. After washing and back-extraction, the P507 organic phase is separated from the cobalt. The cobalt sulfate solution obtained by back-extraction is de-oiled and filtered to obtain the finished cobalt sulfate product, which is then sent to the cobalt or cobalt salt product system.

[0019] S123. After the P507 organic phase is subjected to magnesium washing, chlorine washing, sodium soap washing, and nickel soap washing to remove impurities, it is returned to the extraction system in step 121 for reuse.

[0020] The above technical solution enables the extraction of cobalt from the P204 raffinate, the regeneration of the organic phase from the P507 extraction, and the production of a qualified cobalt sulfate product.

[0021] In a preferred embodiment, the P507 raffinate after cobalt extraction using the P507 extraction system is passed into a Cyanex 272 extraction system for deep magnesium extraction, including the following sub-steps:

[0022] S131. The P507 raffinate is transported to the magnesium extraction section of the Cyanex272 extraction system. The P507 raffinate and the converted Cyanex272 organic phase are subjected to multi-stage countercurrent extraction to obtain nickel sulfate solution and Cyanex272 supported organic phase.

[0023] S132. After degreasing and fine filtration, nickel sulfate solution yields battery-grade nickel sulfate solution.

[0024] S133. The Cyanex 272-loaded organic phase after magnesium extraction is washed with dilute sulfuric acid and back-extracted to obtain antimagnesium solution and regenerated Cyanex 272 organic phase. The regenerated Cyanex 272 organic phase is backwashed with dilute sulfuric acid and returned to step 131 of the Cyanex 272 extraction system for reuse. The antimagnesium solution is treated as wastewater.

[0025] The above technical solution enables the extraction of magnesium from the P507 raffinate, the regeneration of the organic phase extracted by Cyanex 272, and the production of a battery-grade nickel sulfate solution that meets the requirements.

[0026] In a preferred embodiment, the extraction carrier solvent does not contain an extractant, and the extraction carrier solvent is 260# kerosene or a diluent.

[0027] In the above technical solution, the use of kerosene to pre-wash out the organic matter in the heavy metal sludge leachate can effectively avoid the impact on the downstream dissolution and extraction process.

[0028] In a preferred embodiment, the heavy metal sludge leachate and the extraction carrier solvent are mixed and clarified in three to five stages in step S1, and the contaminated extraction carrier solvent and pure water are mixed and clarified in three stages in the extraction tank in step S2. Both the mixing and clarification process in step S1 and the mixing and clarification process in step S2 are carried out in a chamber-type extraction tank.

[0029] In a preferred embodiment, the P204 extraction system has a total of 40 extraction stages, specifically distributed as follows:

[0030] Saponification stage 2, soap conversion clarification stage 1, soap conversion stage 4, raffinate clarification stage 1, extraction stage 10, washing stage 12, post-reverse impurity clarification stage 1, reverse impurity stage 4, reverse iron stage 2, washing stage 2, organic clarification stage 1.

[0031] In a preferred embodiment, the P507 extraction system has a total of 56 extraction stages, specifically distributed as follows:

[0032] Saponification Grade 2, Soap Conversion Clarification Grade 1, Soap Conversion Grade 5, Raffinate Clarification Grade 1, Extraction Grade 8, Nickel Washing Grade 9, Organic Clarification Grade 1, Magnesium Washing Clarification Grade 1, Magnesium Washing Grade 15, Cobalt Removal Post-Clearing Liquid Clarification Grade 1, Cobalt Removal Grade 6, Iron Removal Post-Clearing Liquid Clarification Grade 1, Iron Removal Grade 2, Washing Grade 2, Organic Clarification Grade 1.

[0033] In a preferred embodiment, the Cyanex 272 extraction system has a total of 30 extraction stages, specifically distributed as follows:

[0034] Saponification stage 2, soap conversion clarification stage 1, soap conversion stage 4, raffinate clarification stage 1, extraction stage 6, back-extraction stage 10, anti-iron liquid clarification stage 1, anti-iron stage 2, washing stage 2, organic clarification stage 1.

[0035] The extraction and purification method for heavy metal sludge leachate provided by this invention has the following beneficial effects:

[0036] (1) The heavy metal sludge leachate first undergoes a washing process of mixing and clarification at more than 3 stages with the extraction carrier solvent (i.e., diluent or kerosene), which can fully transfer the harmful organic matter in the leachate to the extraction carrier solvent. After washing, the leachate enters the extraction system of P204, P507 and Cyanex272, which can greatly reduce the damage of organic matter in the heavy metal sludge leachate to the organic system.

[0037] (2) The extraction carrier solvent is washed with pure water to transfer impurities to pure water. The extraction carrier solvent can be recycled. The wastewater after washing is then treated by an oil remover and activated carbon adsorption and returned to the next batch of materials. Alternatively, after oil removal, it can be transferred to the electroplating park to precipitate trace heavy metals in heavy metal wastewater, which can greatly reduce costs. Attached Figure Description

[0038] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 This is a flowchart of the extraction and purification method for heavy metal sludge leachate according to the present invention;

[0040] Figure 2 This is a process flow diagram of the P204 extraction system according to the present invention;

[0041] Figure 3 This is a process flow diagram of the P507 extraction system according to the present invention;

[0042] Figure 4 This is a process flow diagram of the Cyanex 272 extraction system according to the present invention. Detailed Implementation

[0043] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] The organic matter COD in heavy metal sludge leachate ranges from 1000 to 10000 mg / L, severely disrupting the downstream dissolution and extraction system balance, leading to extraction failure, the formation of substandard products, and impacting production. Direct adsorption with activated carbon results in the loss of metal ions. Therefore, this application provides a method for the extraction and purification of heavy metal sludge leachate, employing an extraction carrier solvent to pre-wash out the organic matter in the leachate, thus avoiding impact on the downstream dissolution and extraction process.

[0046] Figure 1 A flowchart of a method for treating heavy metal sludge leachate according to the present invention is shown, as follows: Figure 1 As shown, the extraction and purification method for heavy metal sludge leachate provided in this application includes the following steps:

[0047] S1. The heavy metal sludge leachate is mixed and clarified with the extraction carrier solvent in three or more stages to obtain a clean leachate and a contaminated extraction carrier solvent. The clean leachate is then sequentially passed through a P204 extraction system, a P507 extraction system, and a Cyanex 272 extraction system for extraction and impurity removal, finally yielding a nickel sulfate solution and a cobalt sulfate solution. The extraction carrier solvent does not contain any extractant; the preferred extraction carrier solvent is 260# kerosene or a diluent.

[0048] S2. The extraction carrier solvent is mixed with pure water and clarified to obtain polluted water and clean extraction carrier solvent. The clean extraction carrier solvent is returned to step S1 for recycling. The polluted water is recycled after being treated with oil removal or purified by an activated carbon device.

[0049] This application uses heavy metal sludge leachate as raw material, with a pH of 3.5 to 4.0. It first undergoes 3 to 5 stages of washing with a clean extraction carrier solvent, and then is extracted and purified using a P204 extraction system, a P507 extraction system, and a Cyanex 272 extraction system to finally obtain nickel sulfate solution and cobalt sulfate solution that meet the requirements.

[0050] The single-stage mixing time for solvent washing of the extraction carrier, P204 extraction, P507 extraction, and Cyanex 272 extraction is 3-5 minutes, and the single-stage clarification time is 15-25 minutes.

[0051] Specifically, the treatment of this clean leachate includes the following:

[0052] first, Figure 2 The process flow diagram of the P204 extraction system of the present invention is shown below. Figure 2 As shown, the clean leachate is introduced into the P204 system for extraction and impurity removal, including the following sub-steps:

[0053] S111. The pH of the clean leachate is finely adjusted to 4.0 using liquid alkali, and then filtered through a precision filter to obtain the iron-removed solution.

[0054] S112. The P204 organic phase is saponified using a 30-32% NaOH solution with a saponification rate of 55-65%. After the saponified P204 organic phase is converted to soap with nickel sulfate solution, it is subjected to multi-stage countercurrent extraction with the iron-removed liquid to obtain P204 raffinate and P204-loaded organic phase.

[0055] S113. The P2O4-supported organic phase is washed with a 4N dilute sulfuric acid solution, and the solution and regenerated P2O4 organic phase are back-extracted. The back-extraction solution also contains the impurity Mn. 2+ Cu 2+ Zn 2+ Mg 2+ Ca 2+ The wastewater is then sent to the wastewater treatment plant for processing. The regenerated P204 extract organic phase is washed with pure water and then returned to step S112 for recycling.

[0056] The P204 extraction system has a total of 40 extraction stages, specifically distributed as follows:

[0057] Saponification stage 2, soap conversion clarification stage 1, soap conversion stage 4, raffinate clarification stage 1, extraction stage 10, washing stage 12, post-reverse impurity clarification stage 1, reverse impurity stage 4, reverse iron stage 2, washing stage 2, organic clarification stage 1.

[0058] Secondly Figure 3 The process flow diagram of the P507 extraction system of the present invention is shown, as follows: Figure 3 As shown, the P204 raffinate after impurity removal by the P204 extraction system is passed into the P507 extraction system for cobalt extraction, including the following sub-steps:

[0059] The S121 and P204 raffinates are transported to the cobalt extraction section of the P507 extraction system. The P204 raffinate and the converted P507 organic phase undergo multi-stage countercurrent extraction to obtain the P507 raffinate and the P507-loaded organic phase. Specifically, liquid alkali is added to the P507 organic phase for saponification, with a saponification rate of 55-65%. The saponified P507 extracted organic phase is then converted to soap again using a nickel sulfate solution.

[0060] S122. The P507-supported organic phase after cobalt extraction is back-extracted with 4N dilute sulfuric acid to obtain a cobalt sulfate solution and a regenerated P507 organic phase. The back-extracted cobalt sulfate solution is then subjected to degreasing, filtration, and demagnetization treatments to obtain the finished cobalt sulfate product.

[0061] S123. The regenerated P507 organic phase enters the extractant storage tank, and is then transported back to the extraction tank for saponification. New P507 organic phase is periodically added to the extraction tank.

[0062] The P507 extraction system has a total of 56 extraction stages, specifically distributed as follows:

[0063] Saponification Grade 2, Soap Conversion Clarification Grade 1, Soap Conversion Grade 5, Raffinate Clarification Grade 1, Extraction Grade 8, Nickel Washing Grade 9, Organic Clarification Grade 1, Magnesium Washing Clarification Grade 1, Magnesium Washing Grade 15, Cobalt Removal Post-Clearing Liquid Clarification Grade 1, Cobalt Removal Grade 6, Iron Removal Post-Clearing Liquid Clarification Grade 1, Iron Removal Grade 2, Washing Grade 2, Organic Clarification Grade 1.

[0064] at last, Figure 4 The process flow diagram of the Cyanex 272 extraction system of the present invention is shown below. Figure 4 As shown, the P507 raffinate after cobalt extraction using the P507 extraction system is passed into a Cyanex 272 extraction system for magnesium extraction, including the following sub-steps:

[0065] S131. The P507 raffinate is fed into the magnesium extraction section of the Cyanex 272 extraction system. The P507 raffinate and the saponified Cyanex 272 organic phase undergo multi-stage countercurrent extraction to obtain a nickel sulfate solution and a Cyanex 272-supported organic phase. Specifically, liquid alkali is added to the Cyanex 272 organic phase for saponification. The saponified Cyanex 272 organic phase is then subjected to a nickel sulfate solution for further saponification.

[0066] S132. After degreasing, fine filtration and demagnetization, nickel sulfate solution is used to obtain battery-grade nickel sulfate solution.

[0067] S133. The Cyanex 272-loaded organic phase after magnesium extraction is washed with dilute sulfuric acid and back-extracted to obtain antimagnesium solution and regenerated Cyanex 272 organic phase. The regenerated Cyanex 272 extractant is backwashed with sulfuric acid and reused in the saponification process of the Cyanex 272 extraction system. The antimagnesium solution enters the wastewater treatment system.

[0068] The Cyanex 272 extraction system has a total of 30 extraction stages, specifically distributed as follows:

[0069] Saponification stage 2, soap conversion clarification stage 1, soap conversion stage 4, raffinate clarification stage 1, extraction stage 6, back-extraction stage 10, anti-iron liquid clarification stage 1, anti-iron stage 2, washing stage 2, organic clarification stage 1.

[0070] Through the above technical solution, the heavy metal sludge leachate in this application comes into contact with the extraction carrier solvent before contacting the extraction organic phase. This allows for the separation of potentially harmful substances dissolved into the organic phase from the leachate, achieving pre-purification and preventing the harmful substances from affecting the subsequent extraction process. This enables the stable production of battery-grade nickel sulfate and battery-grade cobalt sulfate directly from heavy metal sludge leachate.

[0071] Example 1

[0072] The leachate was a sulfuric acid leachate of high-nickel electroplating sludge from a certain area in Fujian Province. It had a pH of 3.5, a COD of 1264 mg / L, and other main components as follows:

[0073] Table 1. Main components of the leachate (g / L)

[0074] Element Ni Co Mn Cu Zn Fe Ca Mg Pb Si Al Cd Cr Value 118 3.6 1.6 0.05 0.5 0.01 0.6 3.5 0.005 0.2 0.05 0.005 0.005

[0075] The single-stage extraction tank is selected with a mixing chamber volume of 0.37 m³. 3 The clarification chamber has a volume of 1.85 m³. 3 The mixing time in the mixing chamber is 4.5 minutes, and the residence time in the clarification chamber is 22.5 minutes.

[0076] During the washing process of the leachate, the extraction carrier solvent is 260# sulfonated kerosene. The total number of washing stages for the extraction carrier solvent is 6, including: 3 stages of extraction carrier solvent washing and 3 stages of pure water regeneration. Harmful organic matter in the leachate is sequentially transferred from the leachate to the extraction carrier solvent, pure water, and activated carbon adsorption column. The extraction carrier solvent and pure water are recycled in the system to achieve the purification effect.

[0077] The pH was finely adjusted to 4.0 using 32% liquid alkali, and the solution was filtered through a 5-micron filter to obtain the pre-extraction solution for later use.

[0078] During the P204 extraction process of the pre-extraction liquor, the total number of extraction and impurity removal stages is 40, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 10 stages of extraction, 12 stages of washing, 1 stage of post-reverse impurity clarification, 4 stages of reverse impurity removal, 2 stages of anti-iron removal, 2 stages of washing, and 1 stage of organic clarification. High-nickel P204 raffinate and reverse impurity liquor are obtained. The reverse impurity liquor enters the wastewater treatment system.

[0079] In the P507 extraction process of the high-nickel P204 raffinate, the total number of extraction stages for cobalt extraction is 56, including: 2 stages of saponification, 1 stage of soap conversion clarification, 5 stages of soap conversion, 1 stage of raffinate clarification, 8 stages of extraction, 9 stages of nickel washing, 1 stage of organic clarification, 1 stage of magnesium washing clarification, 15 stages of magnesium washing, 1 stage of cobalt-removed liquid clarification, 6 stages of cobalt-removed liquid clarification, 1 stage of iron-removed liquid clarification, 2 stages of iron-removed liquid clarification, 2 stages of washing, and 1 stage of organic clarification. High-nickel P507 raffinate and cobalt sulfate solution are obtained. The cobalt sulfate solution is further deoiled to obtain the cobalt sulfate product.

[0080] The high-nickel P507 raffinate was subjected to Cyanex 272 deep extraction for magnesium removal, with a total of 30 stages, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 6 stages of extraction, 10 stages of back-extraction, 1 stage of anti-iron solution clarification, 2 stages of anti-iron, 2 stages of washing, and 1 stage of organic clarification. The resulting raffinate was then subjected to coconut shell activated carbon for oil removal, 0.5-micron precision filtration, and pipeline demagnetization to obtain battery-grade nickel sulfate. The impurity solution was then sent to the wastewater treatment system.

[0081] In this embodiment, the yield of cobalt sulfate obtained by the heavy metal sludge leachate extraction and purification method provided in this application is 99.5%. The finished cobalt sulfate contains 0.003 g / l of Ni, 115 ± 5 g / l of Co, 0.002 g / l of Mn, 0.0005 g / l of Cu, 0.0005 g / l of Zn, 0.0038 g / l of Fe, 0.001 g / l of Ca, 0.001 g / l of Mg, 0.0005 g / l of Pb, 0.0005 g / l of Na, 0.001 g / l of Cd, 0.001 g / l of Cr, 0.005 g / l of F, 0.005 g / l of Cl, and 0.001 g / l of Si.

[0082] The yield of the obtained nickel sulfate product is greater than or equal to 99.5%. The content of the finished nickel sulfate product is 125±5 g / L Ni, 0.01 g / L Co, 0.005 g / L Mn, 0.00015 g / L Cu, 0.00015 g / L Zn, 0.0004 g / L Fe, 0.001 g / L Ca, 0.001 g / L Mg, 0.00015 g / L Pb, 0.2 g / L Li, 0.1 g / L Na, 0.0005 g / L Cd, 0.00015 g / L Cr, 0.005 g / L F, 0.0045 g / L Cl, and 0.0009 g / L Si.

[0083] Industrial implementation has shown that this method can maintain continuous production for more than 6 months by simply replacing the activated carbon in the coconut shell activated carbon column periodically, followed by periodic cleaning and regeneration of organic phase impurities in the tank.

[0084] Without pretreatment, severe emulsification of the organic phase extracted by P204 will occur within one week, leading to the failure of impurity removal.

[0085] Example 2:

[0086] A nickel-cobalt hydrometallurgical intermediate (MHP) from Indonesia was mixed with electroplating sludge from an electroplating industrial park in Zhangzhou using sulfuric acid leaching solution. The pH value was 3.7 and the COD was 900 mg / L.

[0087] Table 2. Main components of the leachate (g / L)

[0088] Element Ni Co Mn Cu Zn Fe Ca Mg Pb Si Al Cd Cr Value 118 6.7 11 0.05 0.4 0.009 0.8 3.9 0.005 0.5 0.05 0.005 0.005

[0089] The single-stage extraction tank is configured with a mixing chamber volume of 1.5 m³, a clarification chamber volume of 7.5 m³, a mixing time of 3 minutes in the mixing chamber, and a residence time of 15 minutes in the clarification chamber.

[0090] During the washing process of the leachate, the extraction carrier solvent is the environmentally friendly diluent GV-18A (Shanghai Youta Chemical Technology Co., Ltd.). The total number of washing stages for the extraction carrier solvent is 8, including: 5 stages of extraction carrier solvent washing and 3 stages of pure water regeneration. Harmful organic matter in the leachate is sequentially transferred from the leachate to the extraction carrier solvent, pure water, and activated carbon adsorption column. The extraction carrier solvent and pure water are recycled in the system to achieve the purification effect.

[0091] The pH was finely adjusted to 4.0 using 32% liquid alkali, and then filtered through a 5-micron filter to obtain the pre-extraction solution for later use.

[0092] During the P204 extraction process of the pre-extraction liquor, the total number of extraction and impurity removal stages is 40, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 10 stages of extraction, 12 stages of washing, 1 stage of post-reverse impurity clarification, 4 stages of reverse impurity removal, 2 stages of anti-iron removal, 2 stages of washing, and 1 stage of organic clarification. High-nickel P204 raffinate and reverse impurity liquor are obtained. The reverse impurity liquor enters the wastewater treatment system.

[0093] In the P507 extraction process of the high-nickel P204 raffinate, the total number of extraction stages for cobalt extraction is 56, including: 2 stages of saponification, 1 stage of soap conversion clarification, 5 stages of soap conversion, 1 stage of raffinate clarification, 8 stages of extraction, 9 stages of nickel washing, 1 stage of organic clarification, 1 stage of magnesium washing clarification, 15 stages of magnesium washing, 1 stage of cobalt-removed liquid clarification, 6 stages of cobalt-removed liquid clarification, 1 stage of iron-removed liquid clarification, 2 stages of iron-removed liquid clarification, 2 stages of washing, and 1 stage of organic clarification. High-nickel P507 raffinate and cobalt sulfate solution are obtained. The cobalt sulfate solution is further deoiled to obtain the cobalt sulfate product.

[0094] The high-nickel P507 raffinate was subjected to Cyanex 272 deep extraction for magnesium removal, with a total of 30 stages, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 6 stages of extraction, 10 stages of back-extraction, 1 stage of anti-iron solution clarification, 2 stages of anti-iron, 2 stages of washing, and 1 stage of organic clarification. The resulting raffinate was then subjected to coconut shell activated carbon for oil removal, 0.5-micron precision filtration, and pipeline demagnetization to obtain battery-grade nickel sulfate. The impurity solution was then sent to the wastewater treatment system.

[0095] In this embodiment, the yield of cobalt sulfate obtained by the heavy metal sludge leachate extraction and purification method provided in this application is 99.7%. The finished cobalt sulfate contains 0.003 g / l of Ni, 122 ± 5 g / l of Co, 0.004 g / l of Mn, 0.0005 g / l of Cu, 0.0004 g / l of Zn, 0.0034 g / l of Fe, 0.002 g / l of Ca, 0.001 g / l of Mg, 0.0005 g / l of Pb, 0.005 g / l of Na, 0.001 g / l of Cd, 0.001 g / l of Cr, 0.005 g / l of F, 0.005 g / l of Cl, and 0.001 g / l of Si.

[0096] The yield of nickel sulfate obtained was 99.5%. The finished nickel sulfate contained 125±5 g / L Ni, 0.02 g / L Co, 0.006 g / L Mn, 0.00013 g / L Cu, 0.00012 g / L Zn, 0.0003 g / L Fe, 0.002 g / L Ca, 0.002 g / L Mg, 0.00015 g / L Pb, 0.2 g / L Li, 0.1 g / L Na, 0.0005 g / L Cd, 0.00014 g / L Cr, 0.005 g / L F, 0.0045 g / L Cl, and 0.0007 g / L Si.

[0097] Example 3:

[0098] The sulfuric acid leaching solution of nickel-containing sludge discharged by a high-end bathroom electroplating company in Xiamen has a pH value of 2.5, a COD of 2500 mg / L, and other main components as follows:

[0099] Table 3. Main components of the leachate (g / L)

[0100] Element Ni Co Mn Cu Zn Fe Ca Mg Pb Si Al Cd Cr Value 118 5.2 7.8 0.05 0.6 0.008 0.7 3.7 0.005 0.3 0.05 0.005 0.005

[0101] The single-stage extraction tank is selected with a mixing chamber volume of 0.95m³. 3 The clarification chamber has a volume of 5.5 m³. 3 The mixing time in the mixing chamber is 4 minutes, and the residence time in the clarification chamber is 18 minutes.

[0102] During the washing process of the leachate, the extraction carrier solvent is 260# sulfonated kerosene. The total number of washing stages for the extraction carrier solvent is 7, including: 4 stages of extraction carrier solvent washing and 3 stages of pure water regeneration. Harmful organic matter in the leachate is sequentially transferred from the leachate to the extraction carrier solvent, pure water, and activated carbon adsorption column. The extraction carrier solvent and pure water are recycled in the system to achieve the purification effect.

[0103] The pH was finely adjusted to 4.0 using 32% liquid alkali, and then filtered through a 5-micron filter to obtain the pre-extraction solution for later use.

[0104] During the P204 extraction process of the pre-extraction liquor, the total number of extraction and impurity removal stages is 40, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 10 stages of extraction, 12 stages of washing, 1 stage of post-reverse impurity clarification, 4 stages of reverse impurity removal, 2 stages of anti-iron removal, 2 stages of washing, and 1 stage of organic clarification. High-nickel P204 raffinate and reverse impurity liquor are obtained. The reverse impurity liquor enters the wastewater treatment system.

[0105] In the P507 extraction process of the high-nickel P204 raffinate, the total number of extraction stages for cobalt extraction is 56, including: 2 stages of saponification, 1 stage of soap conversion clarification, 5 stages of soap conversion, 1 stage of raffinate clarification, 8 stages of extraction, 9 stages of nickel washing, 1 stage of organic clarification, 1 stage of magnesium washing clarification, 15 stages of magnesium washing, 1 stage of cobalt-removed liquid clarification, 6 stages of cobalt-removed liquid clarification, 1 stage of iron-removed liquid clarification, 2 stages of iron-removed liquid clarification, 2 stages of washing, and 1 stage of organic clarification. High-nickel P507 raffinate and cobalt sulfate solution are obtained. The cobalt sulfate solution is further deoiled to obtain the cobalt sulfate product.

[0106] The high-nickel P507 raffinate was subjected to Cyanex 272 deep extraction for magnesium removal, with a total of 30 stages, including: 2 stages of saponification, 1 stage of soap conversion clarification, 4 stages of soap conversion, 1 stage of raffinate clarification, 6 stages of extraction, 10 stages of back-extraction, 1 stage of anti-iron solution clarification, 2 stages of anti-iron, 2 stages of washing, and 1 stage of organic clarification. The resulting raffinate was then subjected to coconut shell activated carbon for oil removal, 0.5-micron precision filtration, and pipeline demagnetization to obtain battery-grade nickel sulfate. The impurity solution was then sent to the wastewater treatment system.

[0107] In this embodiment, the yield of cobalt sulfate obtained by the heavy metal sludge leachate extraction and purification method provided in this application is 99.5%. The cobalt sulfate contains 0.003 g / l of Ni, 119 ± 5 g / l of Co, 0.003 g / l of Mn, 0.0005 g / l of Cu, 0.0005 g / l of Zn, 0.0033 g / l of Fe, 0.0015 g / l of Ca, 0.0012 g / l of Mg, 0.0005 g / l of Pb, 0.005 g / l of Na, 0.001 g / l of Cd, 0.001 g / l of Cr, 0.005 g / l of F, 0.006 g / l of Cl, and 0.001 g / l of Si.

[0108] The yield of the obtained nickel sulfate product was 99.5%. The content of the finished nickel sulfate product was 125±5 g / l of Ni, 0.015 g / l of Co, 0.004 g / l of Mn, 0.0002 g / l of Cu, 0.0002 g / l of Zn, 0.0005 g / l of Fe, 0.0015 g / l of Ca, 0.0015 g / l of Mg, 0.00015 g / l of Pb, 0.2 g / l of Li, 0.1 g / l of Na, 0.0005 g / l of Cd, 0.00015 g / l of Cr, 0.005 g / l of F, 0.005 g / l of Cl, and 0.0009 g / l of Si.

[0109] Example 4:

[0110] The sulfuric acid leachate from the sludge discharged by an electroplating company in Quanzhou has a pH of 2.8, a COD of 4100 mg / L, and other major components as follows:

[0111] Table 4. Main components of the leachate (g / L)

[0112] Element Ni Co Mn Cu Zn Fe Ca Mg Pb Si Al Cd Cr Value Element Ni Co Mn Cu Zn Fe Ca Mg Pb Si Cd Value 118 7.1 9.3 0.05 0.6 0.01 0.7 3.8 0.005 0.1 0.05 0.005 0.005

[0113] The single-stage extraction tank is selected with a mixing chamber volume of 1.13 m³. 3 The clarification chamber has a volume of 4.21 m³. 3 The mixing time in the mixing chamber is 4 minutes, and the residence time in the clarification chamber is 20 minutes.

[0114] During the washing process of the leachate, the organic phase composition of the P204 extractant is: 15% P204 extractant and 85% 200# solvent gasoline (volume ratio). The P204 extractant organic phase undergoes five-stage soap making (including two-stage clarification), eight-stage impurity removal (including one-stage clarification), four-stage back-extraction of nickel (including one-stage clarification), three-stage back-extraction of Cu and Zn, and then five-stage back-extraction to finally obtain nickel sulfate and the extract residue.

[0115] The yield of the obtained nickel sulfate product was only 99%, and the Ni content in the nickel sulfate was only 21.50-21.90%, which is classified as a secondary product. In the implementation example, using a conventional P204 extraction system, severe emulsification of the organic phase in the P204 extraction occurred within 3 days, the impurity removal capacity was significantly reduced, and the raffinate did not meet the standards.

[0116] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for extracting and purifying heavy metal sludge leachate, characterized in that, Includes the following steps: S1. The heavy metal electroplating sludge leachate and the extraction carrier solvent are mixed and clarified in a chamber extraction tank in 3 to 5 stages to obtain a clean leachate and a contaminated extraction carrier solvent. The extraction carrier solvent is 260# sulfonated kerosene. The clean leachate is sequentially passed through the P204 extraction system, the P507 extraction system and the Cyanex272 extraction system for extraction and impurity removal. Finally, battery-grade nickel sulfate solution and cobalt sulfate solution are obtained. The clean leachate is passed into the P204 system for extraction and impurity removal, including the following sub-steps: S111. The pH value of the clean leachate is finely adjusted to perform deep iron removal, and then filtered with a precision filter to obtain an iron-removed solution with a pH value of 3.5 to 4.

0. S112 and P204 organic phases are pumped from the storage tank into the extraction tank and successively undergo alkali saponification and nickel sulfate solution conversion. They are then subjected to multi-stage countercurrent extraction with the iron-removed liquid to obtain P204 raffinate and P204 supported organic phase. After washing and back-extraction, the manganese, zinc and copper in the S113 and P204 loaded organic phases are sent to the manganese-zinc-copper product recovery system in the back-extraction liquid, and the regenerated P204 organic phase is obtained. The regenerated P204 organic phase is returned to the extraction system in step S112 for reuse after magnesium removal, chlorine washing and clarification. The P204 raffinate is fed into the P507 extraction system. The P204 raffinate and the converted P507 organic phase undergo multi-stage countercurrent cobalt extraction, including the following sub-steps: S121. The P204 raffinate is transported to the P507 extraction system to separate nickel and cobalt. Cobalt enters the P507 organic phase, while nickel remains in the raffinate. The nickel-containing raffinate is then sent to the next step of deep magnesium extraction. S122. After washing and back-extraction, the P507 organic phase is separated from the cobalt. The cobalt sulfate solution obtained by back-extraction is de-oiled and filtered to obtain the finished cobalt sulfate product, which is then sent to the cobalt or cobalt salt product system. S123. After the P507 organic phase is subjected to magnesium washing, chlorine washing, sodium soap washing, and nickel soap washing to remove impurities, it is returned to the extraction system in step S121 for reuse. The P507 raffinate after cobalt extraction by the P507 extraction system is passed into the Cyanex 272 extraction system for deep magnesium extraction, including the following sub-steps: S131. The P507 raffinate is transported to the magnesium extraction section of the Cyanex272 extraction system. The P507 raffinate and the converted Cyanex272 organic phase are subjected to multi-stage countercurrent extraction to obtain a nickel sulfate solution and a Cyanex272 supported organic phase. S132. After the nickel sulfate solution is subjected to oil removal and fine filtration treatment, a battery-grade nickel sulfate solution is obtained. S133. The Cyanex 272 supported organic phase after magnesium extraction is washed with dilute sulfuric acid and back-extracted to obtain antimagnesium solution and regenerated Cyanex 272 organic phase. The regenerated Cyanex 272 organic phase is backwashed with dilute sulfuric acid and returned to the Cyanex 272 extraction system step S131 for reuse. The antimagnesium solution is treated as wastewater. S2. The contaminated extraction carrier solvent and pure water are mixed and clarified in three stages in the extraction tank of the chamber extraction box to obtain contaminated water and clean carrier solvent. The clean carrier solvent is returned to step S1 for recycling. The contaminated water is purified by an activated carbon device and then recycled. The single-stage mixing time for solvent washing of the extraction carrier, P204 extraction, P507 extraction, and Cyanex 272 extraction is 3-5 minutes, and the single-stage clarification time is 15-25 minutes.

2. The method for extraction and purification of heavy metal sludge leachate according to claim 1, characterized in that, The mixing and clarification process in step S1 and step S2 is completely consistent with the single-stage extraction process.

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