Methods for separating and extracting valuable metals from electroplating sludge

Abstract

This invention provides a method for separating and extracting valuable metals from electroplating sludge, belonging to the field of solid waste resource utilization technology. The electroplating sludge is copper-containing electroplating sludge. The method includes: mixing the dehydrated and dried electroplating sludge with a solid organic acid additive for gradient weak reduction pretreatment; cooling followed by magnetic separation to remove iron; adding ammonia water for reaction, and collecting the ammonia complex solution after solid waste separation; adjusting the pH to 9-10, distilling at 60-70℃ to remove ammonia, and then separating the gas and solid waste, precipitating crude copper hydroxide, with nickel dissolved in the remaining liquid; adjusting the pH of the remaining liquid to 10-11, performing two-stage distillation to remove ammonia, and precipitating crude nickel hydroxide; purifying the crude copper hydroxide and crude nickel hydroxide to obtain refined copper hydroxide and refined nickel hydroxide. This invention mixes the dried electroplating sludge with a solid organic acid and performs reduction pretreatment under different atmospheres and temperatures, combined with ammonia complexation and staged deammoniation processes, achieving efficient recovery of copper and nickel with high purity.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and specifically relates to a method for separating and extracting valuable metals from electroplating sludge. Background Technology

[0002] Electroplating sludge is a hazardous waste generated by the electroplating industry, containing various recyclable valuable metal resources. These include precious metals such as gold (Au), silver (Ag), platinum (Pt), and palladium (Pd), in relatively low amounts; heavy metals such as copper (Cu) and nickel (Ni), in relatively high amounts; and other metals such as iron (Fe) and aluminum (Al). The composition of electroplating sludge varies depending on the specific process. In the PCB and other electronics industries, copper plating sludge is the most widespread. Its main component is copper salts, with small amounts of iron and nickel salts, and trace amounts of other metals (such as zinc, lead, and chromium). Copper plating sludge is a major concern due to its high-value metals (Cu, Ni) and potential toxicity (such as cyanide).

[0003] Currently, the main methods for recovering copper and nickel metal resources from electroplating sludge include pyrometallurgy, hydrometallurgy, bioleaching, and ion exchange / adsorption. Pyrometallurgy is energy-intensive and generates waste gas pollution; hydrometallurgy is complex; bioleaching is inefficient and unsuitable for high-concentration metal sludge; ion exchange is time-consuming, costly, and can cause secondary pollution due to the adsorbent. The products of these methods are mostly mixtures of multiple metals with low purity of individual metals, making it difficult to separate and extract different valuable metals. Summary of the Invention

[0004] Therefore, the present invention aims to provide a method for separating and extracting valuable metals from electroplating sludge, in order to solve at least one of the technical problems in the background art.

[0005] This invention is implemented as follows:

[0006] A method for separating and extracting valuable metals from electroplating sludge, wherein the electroplating sludge is copper-containing electroplating sludge, comprising the following steps:

[0007] The dehydrated and dried electroplating sludge is mixed with organic acid solid additives for gradient weak reduction pretreatment, and then cooled before magnetic separation to remove iron.

[0008] Ammonia water is added to react, and after the reaction, solid waste is separated, and the solution containing ammonia complex is collected.

[0009] The pH of the ammonia complex solution is adjusted to 9-10. After distillation at 60-70℃ to remove ammonia, gas-solid waste is separated to achieve copper-nickel separation. The precipitate is crude copper hydroxide, the nickel element dissolves in the remaining liquid, and the ammonia is recovered.

[0010] Adjust the pH of the remaining liquid to 10-11, perform two-stage distillation to remove ammonia, precipitate crude nickel hydroxide, and recover ammonia gas;

[0011] Crude copper hydroxide and crude nickel hydroxide were repeatedly washed with water and alcohol, and then dried to obtain refined copper hydroxide and refined nickel hydroxide, respectively.

[0012] The organic acid solid additive is oxalic acid, citric acid, or a mixture of the two;

[0013] The gradient-based weak reduction preprocessing is performed in a closed environment and includes:

[0014] Under a nitrogen atmosphere, the temperature is raised to 200℃~250℃ and held for an immediate period of time.

[0015] Under a mixed atmosphere of nitrogen and hydrogen, the temperature is raised to 500℃~600℃ and held for a second time;

[0016] Under a nitrogen and trace air mixed atmosphere, the temperature is lowered to 400℃~450℃ and held for a third time.

[0017] Preferably, the first time is 30 min to 60 min; the second time is 1 h to 3 h; and the third time is 30 min to 60 min.

[0018] Preferably, in the nitrogen and hydrogen mixed atmosphere, the volume concentration of hydrogen is 3% to 5%;

[0019] In the nitrogen and trace air mixture atmosphere, the oxygen concentration is not higher than 3% to 5%.

[0020] Preferably, the amount of the organic acid solid additive is 5 wt% to 15 wt% of the dehydrated and dried electroplating sludge.

[0021] Preferably, the moisture content of the dehydrated and dried electroplating sludge is not higher than 50%.

[0022] Preferably, the magnetic field strength in the magnetic separation for iron removal is 0.3T to 0.5T.

[0023] Preferably, the concentration of the ammonia solution is not higher than 4 mol / L.

[0024] Preferably, the concentration of the ammonia solution is 2 mol / L to 3 mol / L.

[0025] Preferably, the two-stage distillation deammoniation step specifically includes:

[0026] Adjust the pH of the remaining solution to 10-11;

[0027] Under normal pressure, the temperature is raised to 80℃~95℃ for distillation to remove ammonia. The ammonia gas that escapes is recovered by condensation. When the pH of the reaction solution drops below 8, heating is stopped and the solution is allowed to stand and age. A precipitate is formed and the solid and liquid are separated. The precipitate and the supernatant are collected separately.

[0028] Adjust the pH of the supernatant to 10-11;

[0029] Under conditions of 50℃~70℃ and vacuum degree of 5kPa-15kPa, the supernatant is subjected to negative pressure distillation to remove ammonia, and the released ammonia gas is recovered by condensation; when the pH of the reaction solution drops below 8, heating is stopped and the solution is allowed to stand for aging, precipitate is formed and solid-liquid separation is performed, and the precipitate is collected.

[0030] Combining the two precipitations yields crude nickel hydroxide.

[0031] Preferably, the solutions used to adjust the pH of the supernatant and the residual liquid are ammonia water.

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

[0033] 1. This invention mixes dried electroplating sludge with solid organic acid and performs reduction pretreatment under different atmospheres and temperatures. Combined with ammonia complexation and graded deammoniation processes, it achieves efficient recovery of copper and nickel, and the recovered metal has high purity and can be directly used in industry.

[0034] 2. The present invention sets up a gradient heat treatment before magnetic separation, which improves the magnetism of iron impurities and weakens the magnetism of nickel elements, which is beneficial to the efficient removal of iron impurities during subsequent magnetic separation, while avoiding the loss of nickel elements during magnetic separation.

[0035] 3. This invention combines organic acid solid additives and gradient heat treatment to achieve cyanide removal under low temperature conditions, decomposing cyanide in copper electroplating sludge and avoiding its negative impact on the extraction efficiency of organometals and the purity of the product.

[0036] 4. This invention combines organic acid solid additives and gradient heat treatment to remove some organic impurities.

[0037] 5. The process of this invention does not require strong acids, strong alkalis or other compounds, and has low requirements for equipment, which indirectly reduces costs.

[0038] 6. This invention employs a two-stage deammoniation process of atmospheric distillation and negative pressure distillation, which efficiently separates and extracts nickel metal with high purity.

[0039] 7. After the electroplating sludge is treated, the metal content in the waste liquid is low, which meets the emission standards for electroplating pollutants. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method for separating and extracting valuable metals from electroplating sludge according to the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0042] In this invention, electroplating sludge refers to copper-containing electroplating sludge, whose main components include metals (copper, nickel, iron, zinc, lead, chromium, etc.) and organic impurities. Among the above metals, only copper and nickel have high recovery value. The method of this invention is for the separation and extraction of copper and nickel, and is safe and environmentally friendly with less secondary pollution.

[0043] like Figure 1 As shown, the method for separating and extracting valuable metals from electroplating sludge includes steps S10-S60.

[0044] S10, the dehydrated and dried electroplating sludge is mixed with organic acid solid additives for gradient weak reduction pretreatment.

[0045] Specifically, it includes:

[0046] S11, the collected electroplating sludge is dehydrated by pressure filtration, and then dried at a low temperature (generally not exceeding 100℃) or naturally dried to ensure that the moisture content is not higher than 50%, preferably 10% to 30%. The reason for controlling the moisture content in this invention is that: on the one hand, if the moisture content is too high, the subsequently added organic acid solid additives will dissolve excessively and cannot exert their reducing function; on the other hand, if the moisture content is too low, the organic acid solid additives cannot provide sufficient H+. + The environment is affected, thus preventing the organic acid solid additives from exerting their effect in subsequent cyanide-removing additives.

[0047] S12, add 5wt% to 15wt% of organic acid solid additives (oxalic acid, citric acid or a mixture of the two) to the electroplating sludge after S11 treatment, and stir to mix evenly;

[0048] S13, in a closed environment, the mixture obtained by S12 is subjected to gradient weak reduction pretreatment, which is a chemical-thermal reduction coupling process.

[0049] (1) First, under a nitrogen atmosphere, the temperature is raised to 200℃~250℃ and kept at that temperature for 30min~60min;

[0050] This invention utilizes oxalic acid and citric acid, which differ from the acid leaching process in conventional wet treatments. Instead of dissolving the metal, these acids promote cyanide removal and improve the efficiency of magnetic separation for iron removal. Furthermore, the complexing effect of the organic acids selectively activates metal oxides, enhancing subsequent separation efficiency.

[0051] In this step, some organic acid solid additives dissolve in free water or water of crystallization, creating a weakly acidic environment. Combined with anaerobic and pyrolysis conditions, the metal cyanide is decomposed, achieving cyanide breakdown. Under normal conditions, temperatures of 600℃ or even above 800℃ are required for complete cyanide breakdown. Furthermore, electroplating sludge typically also contains thiourea.

[0052] The reason for controlling the temperature in this step is to avoid the reduction reaction starting too early; the reason for controlling the time is that, on the one hand, the content is small and there is no need for excessive time to increase energy consumption and cost; on the other hand, it is to avoid excessive decomposition of the organic acid solid additives and inhibit their role in subsequent reduction.

[0053] Furthermore, the organic acid solid additives generate carbon dioxide, carbon monoxide, water, or hydrogen during pyrolysis. The generated CO can partially reduce nickel compounds. Due to temperature and time control, the complete reduction of nickel can be preferentially inhibited, preserving it as weakly magnetic NiO or non-magnetic nickel carboxylates. In addition, some citric acid / oxalic acid complexes with iron ions, providing favorable conditions for subsequent thermal reduction and decomposition into nanoscale magnetic particles (such as Fe3O4).

[0054] (2) Under a mixed atmosphere of nitrogen and hydrogen, the temperature is rapidly raised to 500℃~600℃ and held for 1h~3h; the volume concentration of hydrogen in the mixed atmosphere of nitrogen and hydrogen is 3%~5%;

[0055] The main function of this step is to use H2 / CO to reduce weakly magnetic iron compounds and convert non-magnetic iron compounds into Fe3O4 / Fe;

[0056] The purpose of controlling the hydrogen concentration is to prevent the complete reduction of nickel; in addition, a certain amount of reducing gas is generated in the above step (1), which can make up for the lack of reducing agent; the organic acid solid decomposes and releases reducing gas (carbon monoxide, hydrogen), which promotes the formation of Fe3O4 or Fe; and at the same time, the nickel is incompletely reduced.

[0057] (3) Under a nitrogen and trace air mixed atmosphere, cool down to 400℃~450℃ and keep warm for 30min~60min.

[0058] The oxygen concentration in the nitrogen and trace air mixture atmosphere is not higher than 5%, preferably 3% to 5%, and the partially reduced metallic nickel in step (2) above is re-oxidized to NiO (non-magnetic): ferromagnetic materials (Fe3O4 / Fe) are not easily oxidized due to their slow oxidation kinetics, thus maintaining their magnetism.

[0059] In addition, in the gradient weak reduction pretreatment section, copper compounds are reduced to elemental copper or copper oxide (non-magnetic).

[0060] The functions of gradient weak reduction pretreatment include the following aspects: (1) Cyanide removal: Copper electroplating sludge contains a small amount of cyanide, which mainly comes from the cyanide-containing electroplating solution used in the electroplating process. Its existence form is usually [Cu(CN)3]. 2- Metal cyanide complexes, whether wet or dry, will affect the extraction efficiency and purity of organometallic products when recovering valuable metals. In addition, cyanide is highly toxic. (2) Improve the magnetic properties of iron impurities. There is a lot of iron in electroplating sludge, which has low recovery value and will interfere with the subsequent recovery of copper and nickel. Moreover, the morphology of iron impurities in electroplating sludge is relatively complex, such as elemental iron, oxides, hydroxides and others. Their magnetic properties are different. At present, only elemental iron and Fe3O4 have strong magnetic properties and can be directly separated by magnetic separation. Other iron impurities The low magnetic properties or paramagnetism of the material are not conducive to separation. In addition, the coexistence of organic matter or other heavy metals (such as Cu, Ni, etc.) shields the magnetism of iron; (3) suppress the magnetism of nickel metal and reduce magnetic separation interference; the magnetism of nickel (Ni) impurities in electroplating sludge is closely related to its chemical form. Different nickel compounds have large differences in magnetism, among which metallic nickel and iron-nickel alloys have strong magnetism; (4) thermal decomposition of organic impurities. In the electroplating process, a variety of functional organic additives need to be added, which will result in the residue of organic pollutants. High-temperature thermal decomposition can remove some organic impurities.

[0061] S20: The product from step S10 is cooled in the furnace and then subjected to magnetic separation to remove iron. The magnetic field strength is 0.3T to 0.5T.

[0062] S30, the product after magnetic separation to remove iron in step S20 is added to ammonia water for reaction, and solid waste is separated after the reaction, and the solution containing ammonia complex is collected.

[0063] In this process, copper and its compounds, as well as nickel and its compounds, dissolve in ammonia water. Other metallic impurities, such as zinc, lead, and chromium, only dissolve in high-concentration ammonia water. Therefore, in specific implementations, the ammonia concentration of this invention is no higher than 4 mol / L, preferably 2 mol / L to 3 mol / L. After thorough stirring, the main components of the sparingly soluble substances are zinc, lead, and chromium, while the main component of the solution is an ammonia-containing complex of copper and nickel. The next step is to separate and purify the solution after solid-liquid separation.

[0064] S40 involves adjusting the pH of the solution after solid-liquid separation in S30 to 9-10, followed by atmospheric distillation to remove ammonia at a temperature of 60-70℃. The ammonia produced during the process is recovered by condensation. Since the nickel-ammonia complex is more stable than the copper-ammonia complex, the copper-ammonia complex is the main component to undergo deamination at 60-70℃, resulting in a precipitate, which is crude copper hydroxide. The remaining liquid mainly consists of the nickel-ammonia complex.

[0065] S50, adjust the pH of the remaining liquid to 10-11, perform two-stage distillation to remove ammonia, precipitate crude nickel hydroxide, and recover ammonia; after gradual deammoniation of the nickel-ammonia complex, the NH3 in the solution decreases, the pH spontaneously decreases, and the hydrated nickel ions ([Ni(HO)6)6))... 2+ It will react with OH- to form Ni(OH) precipitate.

[0066] Specifically, it includes:

[0067] (1) First, adjust the pH of the remaining liquid to 10-11 with ammonia water; under normal pressure, heat to 80℃-95℃ for distillation to remove ammonia, and recover the ammonia gas that escapes by condensation; when the pH of the reaction solution drops below 8, stop heating and let it stand to age, precipitate out and separate solid and liquid, and collect the precipitate and supernatant respectively.

[0068] (2) Adjust the pH of the supernatant to 10-11 with ammonia water; under the conditions of 50℃-70℃ and vacuum of 5kPa-15kPa, the supernatant is subjected to negative pressure distillation to remove ammonia, and the ammonia gas that escapes is recovered by condensation; when the pH of the reaction solution drops below 8, stop heating and let it stand for aging, precipitate, and separate solid and liquid, and collect the precipitate.

[0069] (3) The two precipitates are combined to obtain crude nickel hydroxide.

[0070] S60, crude copper hydroxide and crude nickel hydroxide are repeatedly washed with water and alcohol, and then dried to obtain refined copper hydroxide and refined nickel hydroxide, respectively.

[0071] Example 1

[0072] In this embodiment, the metal weight composition of the copper electroplating sludge is as follows: copper 16.7 wt%, nickel 7.9 wt%, iron 5.3 wt%, zinc 3.6 wt%, lead 1.8 wt%, chromium 1.3 wt%, with the remainder being water, other trace metals, and organic matter.

[0073] The method for separating and extracting valuable metals from electroplating sludge comprises the following steps:

[0074] Step 1: Dehydrate the collected electroplating sludge by filter pressing, and then dry it until the dehydration rate is about 30%.

[0075] Step 2: Add 8 wt% oxalic acid solid to the electroplating sludge treated in Step 1 and stir to mix evenly;

[0076] Step 3: Place the mixture obtained in Step 2 into a pyrolysis furnace, purge the air with nitrogen to make the pyrolysis furnace in a nitrogen protective atmosphere, seal it, and heat it to 250°C at a rate of about 5°C / min, and hold it at that temperature for about 50min.

[0077] Step 4: Increase the temperature to 500°C at a rate of approximately 10°C / min, while simultaneously introducing hydrogen into the pyrolysis furnace, so that the pyrolysis furnace is filled with a mixture of nitrogen and hydrogen (hydrogen volume concentration of 5%), and maintain the temperature for approximately 3 hours.

[0078] Step 5: Expel the gas in the pyrolysis furnace through the exhaust system and treat it with alkaline solution; introduce nitrogen to remove the residual gas, and then introduce a small amount of air to fill the pyrolysis furnace with a mixture of nitrogen and air (with an oxygen volume concentration of 5%). Control the temperature of the pyrolysis furnace to about 400℃~450℃, hold it at that temperature for about 60 minutes, and then cool it with the furnace.

[0079] Step 6: The product processed in Step 5 is mechanically crushed into powder and subjected to magnetic separation under a magnetic field strength of 0.3T. The magnetically attracted solid is the iron impurity, and the remainder is the solid slag to be recovered.

[0080] Step 7: Continuously add approximately 3 mol / L ammonia water to the solid residue to be recovered, stir until homogeneous, and stop when the dissolved solids no longer decrease. Separate the solid and liquid, discard the solid residue, and collect the liquid - an ammonia complex solution.

[0081] Step 8: Continue to pass ammonia water into the solution containing the ammonia complex to adjust its pH to 9. Heat the solution in a water bath in a distillation apparatus and keep it at 60℃~70℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 7, stop heating and let it stand for a period of time (about 30 minutes). Then, separate the solid and liquid. The solid is crude copper hydroxide and the liquid is the remaining liquid to be recovered.

[0082] Step 9: Continue to pass ammonia water into the remaining liquid to adjust its pH to 10, continue heating in a water bath, and keep it at 80℃~95℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 minutes). Then, separate the solid and liquid, and collect the precipitate and supernatant respectively.

[0083] Step 10: Continue to pass ammonia water into the supernatant to adjust its pH to 10. Adjust the internal environment of the distillation equipment to a vacuum environment (vacuum degree of 5 kPa). Continue to heat in a water bath and keep it at 50℃~70℃. The ammonia gas that escapes during the process is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 min). Then, separate the solid and liquid and collect the precipitate.

[0084] Step 11: Wash the crude copper hydroxide from step 8 with water, then wash it twice with methanol, and finally wash it once with water and dry it to obtain refined copper hydroxide, thus realizing copper resource recovery.

[0085] Step 12: Combine the precipitates collected in Step 9 and Step 10 to obtain crude nickel hydroxide; wash with water first, then wash with methanol twice, and finally wash with water once, then dry to obtain refined nickel hydroxide, thus realizing nickel resource recovery.

[0086] Example 2

[0087] The copper-containing electroplating sludge in this embodiment is the same as in Embodiment 1.

[0088] The method for separating and extracting valuable metals from electroplating sludge comprises the following steps:

[0089] Step 1: Dehydrate the collected electroplating sludge by filter pressing, and then dry it until the dehydration rate is about 30%.

[0090] Step 2: Add 8 wt% citric acid solid to the electroplating sludge treated in Step 1 and stir to mix evenly;

[0091] Step 3: Place the mixture obtained in Step 2 into a pyrolysis furnace, purge the air with nitrogen to make the pyrolysis furnace in a nitrogen protective atmosphere, seal it, and heat it to 200°C at a rate of about 5°C / min, and hold it at that temperature for about 60min.

[0092] Step 4: Increase the temperature to 550°C at a rate of approximately 10°C / min, while simultaneously introducing hydrogen into the pyrolysis furnace, so that the pyrolysis furnace is filled with a mixture of nitrogen and hydrogen (hydrogen volume concentration of 3%), and maintain the temperature for approximately 2 hours.

[0093] Step 5: Expel the gas in the pyrolysis furnace through the exhaust system and treat it with alkaline solution; introduce nitrogen to remove the residual gas, and then introduce a small amount of air to fill the pyrolysis furnace with a mixture of nitrogen and air (with an oxygen volume concentration of 4%). Control the temperature of the pyrolysis furnace to about 400℃~450℃, hold it at that temperature for about 60 minutes, and then cool it with the furnace.

[0094] Step 6: The product processed in Step 5 is mechanically crushed into powder and subjected to magnetic separation under a magnetic field strength of 0.4T. The magnetically attracted solid is the iron impurity, and the remainder is the solid slag to be recovered.

[0095] Step 7: Continuously add approximately 3 mol / L ammonia water to the solid residue to be recovered, stir until homogeneous, and stop when the dissolved solids no longer decrease. Separate the solid and liquid, discard the solid residue, and collect the liquid - an ammonia complex solution.

[0096] Step 8: Continue to pass ammonia water into the solution containing the ammonia complex to adjust its pH to 9. Heat the solution in a water bath in a distillation apparatus and keep it at 60℃~65℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 7, stop heating and let it stand for a period of time (about 30 minutes). Then, separate the solid and liquid. The solid is crude copper hydroxide and the liquid is the remaining liquid to be recovered.

[0097] Step 9: Continue to pass ammonia water into the remaining liquid to adjust its pH to 11, continue heating in a water bath, and keep it at 80℃~95℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 minutes). Then, separate the solid and liquid, and collect the precipitate and supernatant respectively.

[0098] Step 10: Continue to pass ammonia water into the supernatant to adjust its pH to 11. Adjust the internal environment of the distillation equipment to a vacuum environment (vacuum degree of 5 kPa), continue water bath heating, and keep it at 50℃~70℃. The ammonia gas that escapes during the process is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 min). Then, separate the solid and liquid and collect the precipitate.

[0099] Step 11: Wash the crude copper hydroxide from step 8 with water, then wash it twice with methanol, and finally wash it once with water and dry it to obtain refined copper hydroxide, thus realizing copper resource recovery.

[0100] Step 12: Combine the precipitates collected in Step 9 and Step 10 to obtain crude nickel hydroxide; wash with water first, then wash with methanol twice, and finally wash with water once, then dry to obtain refined nickel hydroxide, thus realizing nickel resource recovery.

[0101] Example 3

[0102] The copper-containing electroplating sludge in this embodiment is the same as in Embodiment 1.

[0103] The method for separating and extracting valuable metals from electroplating sludge comprises the following steps:

[0104] Step 1: Dehydrate the collected electroplating sludge by filter pressing, and then dry it until the dehydration rate is about 30%.

[0105] Step 2: Add 3wt% citric acid solid and 5wt% oxalic acid solid to the electroplating sludge treated in Step 1, and stir to mix evenly;

[0106] Step 3: Place the mixture obtained in Step 2 into a pyrolysis furnace, purge the air with nitrogen to make the pyrolysis furnace in a nitrogen protective atmosphere, seal it, and heat it to 230°C at a rate of about 5°C / min, and hold it at that temperature for about 40 minutes.

[0107] Step 4: Increase the temperature to 600°C at a rate of approximately 10°C / min, while simultaneously introducing hydrogen into the pyrolysis furnace, so that the pyrolysis furnace is filled with a mixture of nitrogen and hydrogen (hydrogen volume concentration of 4%), and maintain the temperature for approximately 1.5 hours.

[0108] Step 5: Expel the gas in the pyrolysis furnace through the exhaust system and treat it with alkaline solution; introduce nitrogen to remove the residual gas, and then introduce a small amount of air to fill the pyrolysis furnace with a mixture of nitrogen and air (with an oxygen volume concentration of 3%). Control the temperature of the pyrolysis furnace to about 400℃~450℃, hold it at that temperature for about 60 minutes, and then cool it with the furnace.

[0109] Step 6: The product processed in Step 5 is mechanically crushed into powder and subjected to magnetic separation under a magnetic field strength of 0.5T. The magnetically attracted solid is the iron impurity, and the remainder is the solid slag to be recovered.

[0110] Step 7: Continuously add approximately 2 mol / L ammonia water to the solid residue to be recovered, stir until homogeneous, and stop when the dissolved solids no longer decrease. Separate the solid and liquid, discard the solid residue, and collect the liquid - an ammonia complex solution.

[0111] Step 8: Continue to pass ammonia water into the solution containing the ammonia complex to adjust its pH to 10. Heat the solution in a water bath in a distillation apparatus and keep it at 60℃~70℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 7, stop heating and let it stand for a period of time (about 50 minutes). Then, separate the solid and liquid. The solid is crude copper hydroxide and the liquid is the remaining liquid to be recovered.

[0112] Step 9: Continue to pass ammonia water into the remaining liquid to adjust its pH to 11, continue heating in a water bath, and keep it at 80℃~95℃. During the process, the ammonia gas that escapes is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 minutes). Then, separate the solid and liquid, and collect the precipitate and supernatant respectively.

[0113] Step 10: Continue to pass ammonia water into the supernatant to adjust its pH to 11. Adjust the internal environment of the distillation equipment to a vacuum environment (vacuum degree of 5 kPa), continue water bath heating, and keep it at a temperature between 50℃ and 70℃. The ammonia gas that escapes during the process is discharged and recovered by condensation. When the pH of the reaction system drops to 8, stop heating and let it stand for aging (about 30 minutes). Then, separate the solid and liquid and collect the precipitate.

[0114] Step 11: Wash the crude copper hydroxide from step 8 with water, then wash it twice with methanol, and finally wash it once with water and dry it to obtain refined copper hydroxide, thus realizing copper resource recovery.

[0115] Step 12: Combine the precipitates collected in Step 9 and Step 10 to obtain crude nickel hydroxide; wash with water first, then wash with methanol twice, and finally wash with water once, then dry to obtain refined nickel hydroxide, thus realizing nickel resource recovery.

[0116] Example 4

[0117] This embodiment is based on Example 1, except that the amount of solid oxalic acid in step 2 is adjusted to 5 wt%, while the other reaction conditions and steps are the same as in Example 1.

[0118] Example 6

[0119] This embodiment is based on Example 1, except that the amount of solid oxalic acid in step 2 is adjusted to 10 wt%, while the other reaction conditions and steps are the same as in Example 1.

[0120] Example 7

[0121] This embodiment is based on Example 1, except that the amount of solid oxalic acid in step 2 is adjusted to 13 wt%, while the other reaction conditions and steps are the same as in Example 1.

[0122] Example 8

[0123] This embodiment is based on Example 1, except that the amount of solid oxalic acid in step 2 is adjusted to 15 wt%, while the other reaction conditions and steps are the same as in Example 1.

[0124] Comparative Example 1

[0125] This comparative example omits step 2 from Example 1, i.e., does not add organic acid solid additives, while other reaction conditions and steps are the same as in Example 1.

[0126] Comparative Example 2

[0127] This comparative example is based on Example 1, except that the organic acid solid auxiliary agent (oxalic acid) in step 2 is replaced with hydrochloric acid, while the other reaction conditions and steps are the same as in Example 1.

[0128] Comparative Example 3

[0129] This comparative example omits step 3 from Example 1. That is, in the gradient weak reduction pretreatment, only the intermediate high-temperature heat treatment and the final medium-temperature heat treatment are used, and the initial low-temperature heat treatment is omitted. Other reaction conditions and steps are the same as in Example 1.

[0130] Comparative Example 4

[0131] This comparative example omits step 5 from Example 1. That is, in the gradient weak reduction pretreatment, only the initial low-temperature heat treatment + the intermediate high-temperature heat treatment are used, and the final medium-low temperature heat treatment is omitted. Other reaction conditions and steps are the same as in Example 1.

[0132] Comparative Example 5

[0133] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 3 is adjusted to 180°C, while the other reaction conditions and steps are the same as in Example 1.

[0134] Comparative Example 6

[0135] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 3 is adjusted to 280°C, while the other reaction conditions and steps are the same as in Example 1.

[0136] Comparative Example 7

[0137] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 4 is adjusted to 480°C, while the other reaction conditions and steps are the same as in Example 1.

[0138] Comparative Example 8

[0139] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 4 is adjusted to 620°C, while the other reaction conditions and steps are the same as in Example 1.

[0140] Comparative Example 9

[0141] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 5 is adjusted to 380°C, while the other reaction conditions and steps are the same as in Example 1.

[0142] Comparative Example 10

[0143] This comparative example is based on Example 1, except that the temperature of the pyrolysis furnace in step 5 is adjusted to 480°C, while the other reaction conditions and steps are the same as in Example 1.

[0144] Comparative Example 11

[0145] This comparative example omits step 9 from Example 1, i.e., the two-stage distillation deamination only uses the single-stage negative pressure distillation deamination, while the other reaction conditions and steps are the same as in Example 1.

[0146] Comparative Example 12

[0147] This comparative example omits step 10 from Example 1, i.e., the two-stage distillation deamination only uses one stage of atmospheric pressure distillation for deamination, while the other reaction conditions and steps are the same as in Example 1.

[0148] The yields and purity of the products obtained in Examples 1 to 8 and Comparative Examples 1 to 12 were tested, and the results are shown in Table 1 below. The yield is the ratio of the molar amount of refined copper hydroxide or nickel hydroxide to the corresponding molar amounts of copper and nickel in the copper-containing electroplating sludge. The purity of the refined copper hydroxide or nickel hydroxide was determined by atomic absorption spectrometry (AAS).

[0149] Table 1

[0150]

[0151] As shown in Table 1, the copper and nickel recovery rates of the embodiments of the present invention are both higher than 90%, and the purity is not lower than 99%, which meets industrial requirements.

[0152] Comparing Comparative Example 1 with Example 1, it can be seen that without the addition of organic acid solid additives before gradient weak reduction pretreatment, the recovery rates of copper and nickel both decreased significantly, and the purity also decreased.

[0153] Comparing Comparative Example 2 with Example 1, it can be seen that when conventional inorganic acid-hydrochloric acid was added before the gradient weak reduction pretreatment, the recovery rates of copper and nickel decreased significantly, and the purity also decreased; however, the effect was better than that of Comparative Example 1.

[0154] Comparing Comparative Example 3 with Example 1, it can be seen that when the three-stage gradient weak reduction pretreatment is replaced by removing the two-stage heat treatment at low temperature at the beginning, the copper recovery rate and purity both decrease, while the nickel recovery rate increases but the purity decreases significantly.

[0155] Comparing Comparative Example 4 with Example 1, it can be seen that when the three-stage gradient weak reduction pretreatment is replaced with two-stage heat treatment at medium temperature after the latter stage is removed, the copper recovery rate and purity remain almost unchanged, but the nickel recovery rate decreases significantly.

[0156] Comparing Comparative Examples 5 and 6 with Example 1, it can be seen that when the temperature of the initial low-temperature heat treatment in the gradient weak reduction pretreatment is too high or too low, the recovery rates of copper and nickel decrease slightly, and the purity also decreases.

[0157] Comparing Comparative Examples 7 and 8 with Example 1, it can be seen that when the temperature of the high-temperature heat treatment in the middle stage of the gradient weak reduction pretreatment is too high or too low, the copper recovery rate and purity remain almost unchanged, but the nickel recovery rate drops significantly.

[0158] Comparing Comparative Examples 9 and 10 with Example 1, it can be seen that when the temperature of the intermediate-temperature heat treatment in the later stage of the gradient weak reduction pretreatment is too low, the copper recovery rate and purity are almost unchanged, but the nickel recovery rate drops significantly; when the temperature is too high, the purity of both nickel and copper decreases, and the impurities are mainly iron.

[0159] Comparing Comparative Examples 11 and 12 with Example 1, it can be seen that when only one stage of distillation is used for ammonia removal in two-stage distillation, the copper recovery rate and purity remain almost unchanged, but the nickel recovery rate decreases significantly.

[0160] In addition, the waste liquids after two-stage distillation and ammonia removal in Examples 1 to 8 and Comparative Examples 1 to 12 were tested to determine their pollutant content, and the results are shown in Table 2 below.

[0161] Table 2

[0162]

[0163]

[0164] As can be seen from the data in Table 2, the waste liquid generated after treating the electroplating sludge in this embodiment of the invention complies with GB21900-2008 "Electroplating Pollutant Discharge Standard".

[0165] In Comparative Examples 1 to 12, the contents of various substances in the wastewater generated after treating electroplating sludge deteriorated to varying degrees.

[0166] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for separating and extracting valuable metals from electroplating sludge, wherein the electroplating sludge is copper-containing electroplating sludge, characterized in that... The method includes the following steps: The dehydrated and dried electroplating sludge is mixed with organic acid solid additives for gradient weak reduction pretreatment, and then cooled before magnetic separation to remove iron. Ammonia water is added to react, and after the reaction, solid waste is separated, and the solution containing ammonia complex is collected. The pH of the ammonia complex solution is adjusted to 9-10. After distillation at 60-70℃ to remove ammonia, gas-solid waste is separated to achieve copper-nickel separation. The precipitate is crude copper hydroxide, the nickel element dissolves in the remaining liquid, and the ammonia is recovered. Adjust the pH of the remaining liquid to 10-11, perform two-stage distillation to remove ammonia, precipitate crude nickel hydroxide, and recover ammonia gas; Crude copper hydroxide and crude nickel hydroxide were repeatedly washed with water and alcohol, and then dried to obtain refined copper hydroxide and refined nickel hydroxide, respectively. The organic acid solid additive is oxalic acid, citric acid, or a mixture of the two; The gradient-based weak reduction preprocessing is performed in a closed environment and includes: Under a nitrogen atmosphere, the temperature is raised to 200℃~250℃ and held for an immediate period of time. Under a mixed atmosphere of nitrogen and hydrogen, the temperature is raised to 500℃~600℃ and held for a second time; Under a nitrogen and trace air mixed atmosphere, the temperature is lowered to 400℃~450℃ and held for a third time.

2. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The first time period is 30 min to 60 min; the second time period is 1 h to 3 h; and the third time period is 30 min to 60 min.

3. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, In the nitrogen and hydrogen mixed atmosphere, the volume concentration of hydrogen is 3% to 5%. In the nitrogen and trace air mixture atmosphere, the oxygen concentration is not higher than 3% to 5%.

4. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The amount of the organic acid solid additive is 5 wt% to 15 wt% of the dehydrated and dried electroplating sludge.

5. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The moisture content of the dehydrated and dried electroplating sludge is not higher than 50%.

6. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The magnetic field strength in the magnetic separation for iron removal is 0.3T to 0.5T.

7. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The concentration of ammonia water is not higher than 4 mol / L.

8. The method for separating and extracting valuable metals from electroplating sludge according to claim 7, characterized in that, The concentration of the ammonia water is 2 mol / L to 3 mol / L.

9. The method for separating and extracting valuable metals from electroplating sludge according to claim 1, characterized in that, The two-stage distillation deammoniation step specifically includes: Adjust the pH of the remaining solution to 10-11; Under normal pressure, the temperature is raised to 80℃~95℃ for distillation to remove ammonia. The ammonia gas that escapes is recovered by condensation. When the pH of the reaction solution drops below 8, heating is stopped and the solution is allowed to stand and age. A precipitate is formed and the solid and liquid are separated. The precipitate and the supernatant are collected separately. Adjust the pH of the supernatant to 10-11; Under conditions of 50℃~70℃ and vacuum degree of 5kPa-15kPa, the supernatant is subjected to negative pressure distillation to remove ammonia, and the released ammonia gas is recovered by condensation; when the pH of the reaction solution drops below 8, heating is stopped and the solution is allowed to stand for aging, precipitate is formed and solid-liquid separation is performed, and the precipitate is collected. Combining the two precipitations yields crude nickel hydroxide.

10. The method for separating and extracting valuable metals from electroplating sludge according to claim 9, characterized in that, The solutions used to adjust the pH of the supernatant and the residual liquid were ammonia water.

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