System and method for recovering valuable metals from blue sludge through high-temperature dry roasting

Abstract

The present invention provides a system and method for recovering valuable metals from blue sludge through high-temperature dry roasting. The system comprises a mixing device, a high-temperature dry roasting device, a hydrolysis device, a centrifugal filtration device, and precipitation devices. The present invention involves performing a high-temperature dry roasting reaction and a hydrolysis reaction in an alkaline environment, followed by a centrifugation and filtration process to separate the alkaline leachate containing aluminum ions and the nickel-containing residue. The alkaline leachate containing aluminum ions is then subjected to a precipitation reaction to obtain an aluminum hydroxide product. The nickel-containing residue is subsequently subjected to an acid leaching reaction and a precipitation reaction to obtain a nickel hydroxide product. This method performs effectively dissolves and separates aluminum ions and nickel ions from blue sludge, thereby enhancing the recovery rate of metals from the blue sludge.

Description

Technical Field

[0001] This invention relates to a system and method for effectively separating aluminum and nickel ions from aluminum-nickel slag and improving the metal recovery rate of aluminum-nickel slag by utilizing high-temperature dry calcination to recover valuable metals from aluminum-nickel slag. Specifically, it involves first performing a high-temperature dry calcination reaction and a hydrolysis reaction under an alkaline environment, followed by centrifugal filtration to separate an alkaline leaching solution containing aluminum ions and a nickel-containing residue. The alkaline leaching solution containing aluminum ions is then subjected to a precipitation reaction to obtain aluminum hydroxide product; furthermore, the nickel-containing residue undergoes an acid leaching reaction and a precipitation reaction to obtain nickel hydroxide product. This system and method effectively dissolves and separates aluminum and nickel ions from aluminum-nickel slag. Prior Technology

[0002] AlNi slag is a residue produced in oil refineries after recovering molybdenum and vanadium from waste hydrodesulfurization catalysts. Traditional methods of treating AlNi slag primarily involve solidification and landfill disposal or transporting it to mainland China as raw material for nickel refining. However, AlNi slag still contains approximately 3-5% by weight of nickel metal and 30-50% by weight of aluminum metal, giving it high recycling value. Nevertheless, due to the complex composition and structure of AlNi slag, metal recovery from it faces numerous challenges in terms of both process and cost.

[0003] For example, in the existing hydrodesulfurization catalyst treatment process, the calcination temperature is set above 1000℃ in order to convert vanadium and molybdenum sulfides into oxides. However, this will cause the alumina to change from γ-Al2O3 to α-Al2O3, making recovery difficult, and will also cause the aluminum-nickel slag to change into a spinel structure, increasing the difficulty of subsequent nickel metal recovery.

[0004] Alternatively, in existing aluminum-nickel slag recycling processes, to recover the more expensive nickel metal first, the aluminum-nickel slag undergoes an acid leaching reaction. This reaction dissolves both aluminum and nickel metal ions simultaneously, followed by other processing steps to separate the aluminum and nickel metals. However, this method recovers nickel metal with low purity and a low metal leaching rate, and currently, there is no process that can effectively recover aluminum metal afterward. Furthermore, existing processes often use high-pressure reactors and other reaction equipment, but scaling up such equipment will pose a significant challenge. Summary of the Invention

[0005] [The technical problem that the invention aims to solve]

[0006] Given that the complex composition and structure of aluminum-nickel slag in conventional technology leads to many process difficulties and low efficiency in recovering aluminum and nickel metals from it, the inability to effectively separate aluminum and nickel ions in aluminum-nickel slag results in difficulties in metal recovery, low metal recovery rate, low metal leaching rate, and the purity of the recovered metal still needs to be improved. [Technical means]

[0007] After conducting in-depth research to address the aforementioned issues, this invention provides a system and method for recovering valuable metals from aluminum-nickel slag using high-temperature dry calcination. This method effectively separates aluminum and nickel ions from aluminum-nickel slag without the need for a catalyst and with a simple process, thereby increasing the recovery rate of aluminum and nickel metals from the slag, and ensuring that the recovered aluminum and nickel metals are of high purity.

[0008] Specifically, the system for recovering valuable metals from aluminum-nickel slag using high-temperature dry calcination of the present invention comprises: a mixing device, a high-temperature dry calcination device, a hydrolysis device, a centrifugal filtration device, and a sedimentation device.

[0009] Specifically, the mixing device mixes aluminum-nickel slag with solid sodium hydroxide to obtain mixture one, facilitating the reaction in an alkaline environment. The high-temperature dry calcination device calcines mixture one at high temperature to obtain mixture two. The hydrolysis device hydrolyzes mixture two, separating aluminum ions from the aluminum-nickel slag and dissolving them into the liquid, resulting in mixture three. Next, mixture three is centrifuged and filtered to obtain residue and filtrate. The nickel ions in the residue and the aluminum ions in the filtrate are then treated to achieve the separation of aluminum and nickel metals.

[0010] The precipitation apparatus includes an Al(OH)3 precipitation device, where the filtrate is titrated to a pH of 6-6.7 to produce a precipitate, which is then centrifuged and filtered to obtain the Al(OH)3 precipitate, effectively separating aluminum metal. Additionally, the precipitation apparatus includes a Ni(OH)2 precipitation device, where sulfuric acid solution is added to the residue and stirred with a magnetic stirrer to carry out an acid leaching reaction. This process eliminates the need for high-pressure equipment or complex reactors; aluminum and nickel metal separation can be achieved simply through stirring. After the acid leaching reaction, a first centrifugal filtration is performed. The first filtrate is titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate is then titrated with sodium hydroxide solution to a pH of 10-10.5, followed by a third centrifugal filtration. The precipitate from the third centrifugal filtration is Ni(OH)2 precipitate, thus effectively separating nickel metal.

[0011] Among them, the high-temperature dry calcination device calcines the mixture at 800~1000°C for 10 minutes to 1 hour. Under these conditions, the mixture after calcination can better dissolve aluminum ions from the aluminum-nickel slag into the solution during hydrolysis, which is beneficial for the separation of aluminum and nickel metals.

[0012] The weight ratio of aluminum-nickel slag to solid sodium hydroxide is 1:0.4 to 1:2.4, which achieves a high aluminum leaching rate. Furthermore, the ideal weight ratio of aluminum-nickel slag to solid sodium hydroxide is 1:2.4, ensuring an aluminum leaching rate of over 93%.

[0013] The weight of the aluminum-nickel slag is 5-25g, which ensures a high nickel leaching rate. From the perspective of further increasing the leaching rate, the ideal weight of the aluminum-nickel slag is 5g, which ensures that the nickel leaching rate reaches more than 98%.

[0014] Furthermore, the method for recovering valuable metals from aluminum-nickel slag using high-temperature dry calcination according to the present invention includes the following steps: S1 Mixing step: Mix aluminum-nickel slag and solid sodium hydroxide to obtain mixture one, facilitating the reaction under an alkaline environment. S2 High-temperature dry calcination step: Calcinate mixture one at high temperature to obtain mixture two. S3 Hydrolysis step: Hydrolyze mixture two to separate aluminum ions from the aluminum-nickel slag and leach them into the liquid, obtaining mixture three. S4 Centrifugation and filtration step: Centrifuge and filter mixture three to obtain residue and filtrate. S5 Aluminum ion extraction step: Precipitate the filtrate to obtain Al(OH)3 precipitate, effectively separating aluminum metal ions. S6 Nickel ion extraction step: Acid leaching and precipitation of the residue to obtain Ni(OH)2 precipitate, effectively separating nickel metal ions.

[0015] Furthermore, the weight ratio of aluminum-nickel slag to solid sodium hydroxide is 1:0.4 to 1:2.4, which achieves a high aluminum leaching rate. Ideally, the weight ratio of aluminum-nickel slag to solid sodium hydroxide is 1:2.4, ensuring an aluminum leaching rate of over 93%.

[0016] Furthermore, in the hydrolysis step, 200-500 mL of deionized water is used to react at 100-120°C for 18-26 hours. This ensures that a large amount of aluminum ions are separated from the aluminum-nickel slag and dissolved into the liquid. From the viewpoint of further increasing the leaching rate, it is ideal to use 200 mL of deionized water for the reaction, which ensures that the aluminum leaching rate reaches more than 93%. [Effects of the Invention]

[0017] The system and method for recovering valuable metals from aluminum-nickel slag using high-temperature dry roasting according to the present invention can effectively separate aluminum and nickel ions from aluminum-nickel slag without the need for catalysts, and with simplified processes such as high-temperature dry roasting, hydrolysis, precipitation, and stirring reaction.

[0018] According to the process design of the present invention, which first performs alkali leaching of aluminum ions and then acid leaching of nickel ions, the leaching rates of aluminum and nickel metals in aluminum-nickel slag can be significantly increased to over 97% and 98%, respectively. Furthermore, the recovered aluminum and nickel metals have a purity of up to 98% or even over 99%. Here, purity is calculated by extrapolating the aluminum (nickel) ion concentration in the product back to the weight of aluminum hydroxide (nickel hydroxide) divided by the total weight of the product. The weight of the aluminum (nickel) ions is measured by microwave digestion, as described later. Simple Explanation of the Diagram

[0019] [Figure 1] Flowchart of the process of leaching aluminum ions with alkali and preparing Al(OH)3 in the method of recovering valuable metals from aluminum-nickel slag by high-temperature dry calcination in this invention. [Figure 2] Percentage of aluminum ion types at different pH values. [Figure 3] Flowchart of the acid leaching of nickel ions and the preparation of Ni(OH)2 in the method of recovering valuable metals from aluminum-nickel slag by high-temperature dry roasting in this invention. [Figure 4] Percentage of nickel ion types at different pH values. [Figure 5] Comparison of the effect of sodium hydroxide addition on the metal leaching rate of alkaline leaching reaction. [Figure 6] Comparison of the effects of sodium hydroxide addition on the metal leaching rate in alkaline leaching reaction. [Figure 7] Comparison of the effect of sodium hydroxide addition on the metal leaching rate in acid leaching reaction. [Figure 8] Comparison of the effect of aluminum-nickel slag addition on the metal leaching rate of alkaline leaching reaction. [Figure 9] Comparison of the effect of aluminum-nickel slag addition on the metal leaching rate of acid leaching reaction. [Figure 10] Comparison of the effect of the amount of hydrolysis solution added on the metal leaching rate of the alkaline leaching reaction. [Figure 11] Comparison of the effects of the amount of hydrolysis solution added on the metal leaching rate in the acid leaching reaction. [Figure 12] X-ray diffraction analysis of Al(OH)₃ powder. [Figure 13] SEM image of Al(OH)₃. [Figure 14] SEM-EDS analysis diagram of Al(OH)₃. [Figure 15] X-ray diffraction analysis of Ni(OH)2 powder. [Figure 16] SEM image of Ni(OH)2. [Figure 17] SEM-EDS analysis diagram of Ni(OH)2. Implementation

[0020] The following describes in detail the system and method for recovering valuable metals from aluminum-nickel slag according to the present invention, using embodiments, examples, and reference figures. However, the embodiments and examples are not intended to limit the scope of the present invention, and any implementation that does not depart from the intent of the present invention should also be considered within the scope of the present invention.

[0021] First, the present invention utilizes a high-temperature dry calcination method to recover valuable metals from aluminum-nickel slag, which consists of two processes: high-temperature calcination with alkali to dissolve aluminum ions and prepare Al(OH)3, and acid leaching to extract nickel ions and prepare Ni(OH)2.

[0022] [Implementation Method 1: Alkali Dissolution of Aluminum Ions and Preparation of Al(OH)3]

[0023] Figure 1 is a flowchart of the alkaline leaching of aluminum ions and the preparation of Al(OH)3 in the method for recovering valuable metals from aluminum-nickel slag according to the present invention: First, the aluminum-nickel slag is dried to remove moisture from the sample, and then the aluminum-nickel slag is mixed and ground with solid sodium hydroxide to obtain mixture one, ensuring that the subsequent reaction is carried out in an alkaline environment. Subsequently, mixture one is placed in a high-temperature furnace for calcination to obtain mixture two, and then mixture two is used for hydrolysis reaction. This step will separate aluminum ions from the aluminum-nickel slag and dissolve them in the liquid, separating them from nickel ions, to obtain mixture three. Next, mixture three is centrifuged and filtered to obtain a residue containing nickel ions and a filtrate containing aluminum ions. At this point, aluminum and nickel ions have been successfully separated. The residue will be separated into nickel ions by acid leaching as described in Embodiment 2 below.

[0024] Subsequently, as shown in Figure 1, to extract aluminum ions from the filtrate, the filtrate was titrated with 1M sulfuric acid solution. A precipitate formed when the pH reached 6-6.7. According to Figure 2 (from the literature: B. Lekhlif, L. Oudrhiri, F. Zidane, P. Drogui, JF Blais. Study of the electrocoagulation of electroplating industry wastewaters charged by nickel (II) and chromium (VI). Journal of Materials and Environmental Science, 5 (1), 111-120, 2014.), the state of aluminum ions is affected by pH. At approximately pH 6-6.7, 95% of solid aluminum can be separated, presenting as Al(OH)3. Therefore, this precipitate is clearly Al(OH)3, and aluminum metal ions have indeed been separated. The filtrate from centrifugation is then treated at a wastewater treatment plant, and the precipitate is washed with water and then centrifuged, filtered, and dried to obtain high-purity Al(OH)3.

[0025] [Implementation Method 2: Acid Leaching of Nickel Ions and Preparation of Ni(OH)2]

[0026] Figure 3 is a flowchart of the acid leaching of nickel ions and the preparation of Ni(OH)2 in the method for recovering valuable metals from aluminum-nickel slag of the present invention: First, the residue produced by the aforementioned alkaline leaching reaction is dried to remove moisture, and the residue is mixed with sulfuric acid solution and stirred by a magnetic stirrer to carry out the reaction. At this time, nickel ions are leached from the solid residue into the solution.

[0027] Next, after the acid leaching reaction, a first centrifugal filtration was performed. Since all solids dissolved into liquid, no residue was generated after the centrifugal filtration reaction. The first filtrate was titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate was then titrated with sodium hydroxide solution to a pH of 10-10.5, followed by a third centrifugal filtration. The precipitate from the third centrifugal filtration was Ni(OH)₂ precipitate, indicating that nickel metal ions had been effectively separated. The filtrate from the centrifugal filtration was then treated at a wastewater treatment plant, and the precipitate was washed with water, followed by centrifugal filtration and drying to obtain high-purity Ni(OH)₂. Furthermore, the precipitate from the second centrifugal filtration was Al(OH)₃ precipitate, which could also be obtained by washing with water, centrifugal filtration, and drying.

[0028] As shown in Figure 4 (from the reference: Ahsan Habib, Salma Serniabad, Mohammad Shamim Khan, Rokayea Islam, Mrittika Chakraborty, Aklima Nargis, Md Emran Quayum, Md Ashraful Alam, Valentina Rapozzi, Masaaki Tabata. Formation of Nickel(II)Porphyrin and Its Interaction with DNA in Aqueous Medium, Chemistry and Materials Science, 2021. DOI: 10.20944 / preprints202101.0434.v1.), the state of nickel ions is affected by pH. At a pH of approximately 10–10.5, 77% of solid nickel can be separated, presenting as Ni(OH)₂. Therefore, by adjusting the pH to 10–10.5, Ni(OH)₂ can be obtained, effectively separating nickel metal ions.

[0029] Through further experiments, the inventors discovered that by limiting the weight ratio of aluminum-nickel slag to sodium hydroxide, adjusting the weight of the aluminum-nickel slag, and adjusting the volume of the hydrolysis solution, the leaching amount of aluminum and nickel metals can be further increased, ensuring more complete metal recovery and enhancing the effectiveness of the invention. The following examples illustrate this:

[0030] First, the characteristics of the aluminum-nickel slag used in this invention are determined by measuring the metal ion concentration using microwave attenuation, and then multiplying this concentration by the volume to obtain the weight of the metal ions. The measurement results show that the aluminum-nickel slag of this invention contains 28-40% by weight of aluminum ions and 3-5.6% by weight of nickel ions. That is, 100g of aluminum-nickel slag sample contains 28-40g of aluminum ions and 3-5.6g of nickel ions.

[0031] The microwave digestion assay method is as follows: 1. Place 0.1g of sample (here, aluminum-nickel slag) in a 100℃ oven and dry for 2 hours; 2.0.1 g of dried sample was placed in a digestion flask, and 9 mL of 70% nitric acid, 3 mL of hydrofluoric acid, and 3 mL of 37% hydrochloric acid were added. Pre-digestion was carried out for 30 minutes. 3. Heat at 180℃ for 25 minutes, then hold at that temperature for 25 minutes; 4. After cooling, add 15 mL of boric acid and pre-digest for 30 minutes; 5. Repeat step 3; 6. The water sample after microwave digestion was quantified, and the concentration of metal ions was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). The analysis method of the spectrometer is as follows: a Perkin Elmer inductively coupled plasma optical emission spectrometer (ICP-OES: Avio 200) is used, with the delay time set to 10 seconds, the flush time to 30 seconds, the sample flow rate to 1.5 mL / min, the Al measurement wavelength to 369.153 nm, and the Ni measurement wavelength to 231.604 nm.

[0032] [The Influence of Sodium Hydroxide Usage]

[0033] [Example 1]

[0034] 1. Experimental Procedure: 5g of dried aluminum-nickel slag was mixed with 8g or 12g (repeated once each) of sodium hydroxide (NaOH), resulting in a weight ratio of aluminum-nickel slag to solid sodium hydroxide of 1:1.6 and 1:2.4, respectively. The mixture was then placed in a high-temperature furnace and calcined at 900°C for 20 minutes. Hydrolysis was then carried out using 500 mL of deionized water at 105°C for 24 hours. Subsequently, the mixture was centrifuged at 1500 rpm for 10 minutes to obtain the alkali-dissolved residue and filtrate. To extract aluminum ions from the filtrate, the filtrate was titrated with 1M sulfuric acid solution. When the pH reached 6-6.7, Al(OH)3 precipitate was formed. The precipitate was washed with water and then subjected to centrifugation, filtration, and drying to obtain high-purity Al(OH)3. The method for calculating the metal leaching rate of the alkaline leaching reaction is as follows: the aluminum ion concentration of the filtrate obtained from the centrifugation reaction is analyzed by ICP-OES, the obtained concentration is multiplied by the volume used for measurement to obtain the weight of aluminum ions, and finally the weight of aluminum ions is divided by the weight of aluminum-nickel slag to calculate the metal leaching amount shown in Figure 5.

[0035] 2. Experimental Results: As shown in Figure 5, calcination exhibits excellent leaching effects on aluminum. In this invention, the metal leaching amount is calculated by dividing the weight of metal ions by the weight of the aluminum-nickel slag. Based on the reaction results using 12g of sodium hydroxide (NaOH) in Figure 5, the leaching rates of aluminum metal are 37.44% and 38.88%. Given that the aluminum-nickel slag used in this invention contains 28-40% aluminum ions by weight, 37.44 / 40 = 93.6% and 38.88 / 40 = 97.2%, the aluminum recovery and leaching results are 93.6% and 97.2%, respectively. This means that 93.6% and 97.2% of the aluminum ions were successfully recovered from the aluminum-nickel slag, achieving almost complete recovery.

[0036] [Example 2]

[0037] 1. Experimental Procedure: The residue from the alkaline leaching reaction with 8g of sodium hydroxide in Example 1 was dried. An acid leaching reaction was then carried out using a 1M sulfuric acid solution at a solid-liquid weight ratio of 1:33, stirred with a magnetic stirrer at 300 rpm and 80°C for 6 hours. After the acid leaching reaction, a first centrifugal filtration was performed. The first filtrate was titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate was then titrated with sodium hydroxide solution to a pH of 10-10.5, followed by a third centrifugal filtration. The precipitate from the third centrifugal filtration was Ni(OH)₂ precipitate. After washing the precipitate with water, further centrifugation, filtration, and drying yielded high-purity Ni(OH)₂. Additionally, the precipitate from the second centrifugal filtration was Al(OH)₃ precipitate, which was also washed with water, centrifuged, filtered, and dried to obtain high-purity Al(OH)₃. The method for calculating the metal leaching rate of the acid leaching reaction is the same as that for measuring the metal leaching rate of the alkaline leaching reaction: the aluminum and nickel ion concentrations of the filtrate obtained from the first centrifugation reaction are analyzed by ICP-OES, and the obtained concentrations are multiplied by the volume used for measurement to obtain the weights of aluminum and nickel ions respectively. Finally, the weights of aluminum and nickel ions are divided by the weight of aluminum-nickel slag to calculate the amount of metal leached.

[0038] 2. Experimental Results: The leaching rate of aluminum metal was 1.255%, indicating that aluminum ions were almost completely recovered in the first alkaline leaching step. Furthermore, the leaching rate of nickel metal was 5.498%, and according to the aforementioned aluminum-nickel slag used in this invention, it contains 3-5.6% by weight of nickel ions. Therefore, 5.498 / 5.6 = 98.2%, indicating that the nickel recovery and leaching result here is 98.2%, meaning that 98.2% of the nickel ions were successfully recovered from the aluminum-nickel slag, achieving a complete recovery effect.

[0039] [Example 3]

[0040] 1. Experimental Procedure: Except for drying 5g of aluminum-nickel slag and mixing it with 2g, 4g, 6g, and 8g of sodium hydroxide (NaOH) respectively, the rest of the procedure was the same as in Example 1 to obtain high-purity Al(OH)3. The metal leaching rate of the alkali leaching reaction was calculated using the same method as in Example 1, and the results are shown in Figure 6.

[0041] 2. Experimental Results: As shown in Figure 6, firstly, the aluminum leaching rate increased with the increase of sodium hydroxide content, reaching 24.78%, 35.94%, and 37.47% for 2g, 4g, and 6g, respectively. However, the effect on the leaching rate trend decreased after the addition exceeded 6g. Furthermore, the residue weights obtained after centrifugation and filtration following alkaline leaching reactions with 2g, 4g, 6g, and 8g of sodium hydroxide were 2.59g, 1.41g, 1.26g, and 1.20g, respectively. This indicates that the addition of sodium hydroxide reduces the residue weight, allowing for the extraction of more aluminum ions from the aluminum-nickel slag, hence the increasing aluminum leaching rate.

[0042] [Example 4]

[0043] 1. Experimental Procedure: The residues from the alkaline leaching reaction in Example 3 were dried, and 50 mL of 1M sulfuric acid solution was added. The mixture was stirred at 300 rpm and 80°C for 6 hours using a magnetic stirrer to carry out the acid leaching reaction. The metal leaching rate of the acid leaching reaction was calculated using the same method as in Example 2, and the results are shown in Figure 7.

[0044] 2. Experimental Results: As shown in Figure 7, with the increase of sodium hydroxide addition, the leaching amount of nickel metal increased, while the leaching amount of aluminum metal showed a decreasing trend. The gradual decrease in aluminum metal leaching rate indicates that aluminum ions were more completely recovered in the first alkaline leaching step. Furthermore, the gradual increase in nickel metal leaching rate indicates that nickel metal recovery became more complete with the increase of sodium hydroxide addition.

[0045] Based on the above, Examples 1-4 confirm that the amount of sodium hydroxide added will affect the leaching rate of aluminum and nickel metals.

[0046] [Impact of Aluminum-Nickel Slag Usage]

[0047] [Example 5]

[0048] 1. Experimental Procedure: 5g, 15g, and 25g of aluminum-nickel slag were dried and then mixed with 8g, 24g, and 40g of sodium hydroxide (NaOH), respectively. The remaining procedures were the same as in Example 1, yielding high-purity Al(OH)3. Furthermore, the metal leaching rate of the alkali leaching reaction was calculated using the same method as in Example 1, and the results are shown in Figure 8.

[0049] 2. Experimental Results: As shown in Figure 8, with the increase of the amount of added aluminum-nickel slag, even with a fixed weight ratio of aluminum-nickel slag to sodium hydroxide, the amount of aluminum metal leaching still showed a slight decreasing trend. That is, the scale of the reactants affects the metal leaching rate and recovery rate. Furthermore, the weights of the residues obtained after centrifugation and filtration after adding 5g, 15g, and 25g of aluminum-nickel slag for alkaline leaching were 1.20g, 4.39g, and 7.53g, respectively. This indicates that even if the weight ratio of aluminum-nickel slag to sodium hydroxide is kept constant, the amount of residue does not increase proportionally with the increase of the amount of added aluminum-nickel slag, but rather increases even more, indicating a decrease in the proportion of aluminum metal extracted from the aluminum-nickel slag and a decreasing trend in aluminum leaching.

[0050] [Example 6]

[0051] 1. Experimental Procedure: The residues from the alkaline leaching reaction in Example 5 were dried, and 50 mL of 1M sulfuric acid solution was added. The mixture was stirred at 300 rpm and 80°C for 6 hours using a magnetic stirrer to carry out the acid leaching reaction. The metal leaching rate of the acid leaching reaction was calculated using the same method as in Example 2, and the results are shown in Figure 9.

[0052] 2. Experimental Results: As shown in Figure 9, with the increase of the amount of aluminum-nickel slag added, the leaching amount of nickel metal decreased, while the leaching amount of aluminum metal remained relatively constant. The gradual decrease in the leaching rate of nickel metal indicates that the recovery rate of nickel metal decreases with the increase of the amount of aluminum-nickel slag added. The leaching rate of aluminum metal with 5g of aluminum-nickel slag added was 1.255%, indicating that aluminum ions were indeed almost completely recovered in the first alkaline leaching step. Furthermore, the leaching rate of nickel metal was 5.498%, and according to the aforementioned aluminum-nickel slag used in this invention, it has 3-5.6% by weight of nickel ions. Therefore, 5.498 / 5.6 = 98.2%, indicating that the nickel recovery and leaching result here is 98.2%, meaning that 98.2% of nickel ions were successfully recovered from the aluminum-nickel slag, achieving the effect of full recovery.

[0053] Based on the above, Examples 5 and 6 confirm that the amount of aluminum-nickel slag added will affect the leaching rate of aluminum and nickel metals.

[0054] [Effect of the amount of hydrolysis solution used]

[0055] [Example 7]

[0056] Experimental procedure: Except for drying 5g of aluminum-nickel slag and mixing it with 8g of sodium hydroxide (NaOH), then placing it in a high-temperature furnace and holding it at 900°C for 20 minutes for calcination, and then hydrolyzing it by reacting it with 200 mL, 300 mL, 400 mL, and 500 mL of deionized water at 105°C for 24 hours respectively, the rest of the procedure was the same as in Example 1, yielding high-purity Al(OH)3. Furthermore, using the same method as in Example 1, the metal leaching rate of the alkali leaching reaction was calculated, and the results are shown in Figure 10.

[0057] 2. Experimental Results: As shown in Figure 10, the leaching amount of aluminum metal changes relatively with the increase of deionized water in the hydrolysis solution. That is, the volume of deionized water can be adjusted according to requirements to achieve full recovery of valuable metals from the aluminum-nickel slag. The leaching rate of aluminum metal in the reaction with 200 mL of deionized water was 37.54%. Since the aluminum-nickel slag used in this invention has 28-40% by weight of aluminum ions, 37.54 / 40 = 93.9%, the aluminum recovery and leaching result is 93.9%, meaning that 93.9% of the aluminum ions were successfully recovered from the aluminum-nickel slag, achieving almost complete recovery.

[0058] Furthermore, the weights of the residues obtained after centrifugation and filtration after adding 200 mL, 300 mL, 400 mL, and 500 mL of deionized water for hydrolysis were 1.05 g, 1.43 g, 0.81 g, and 1.20 g, respectively. This indicates that the reaction for extracting aluminum metal from aluminum-nickel slag can achieve high leaching rates and high recovery rates under the conditions of adding 200 mL, 300 mL, 400 mL, and 500 mL of deionized water.

[0059] [Example 8]

[0060] 1. Experimental Procedure: The residues from the alkaline leaching reaction in Example 7 were dried, and 50 mL of 1M sulfuric acid solution was added. The mixture was stirred at 300 rpm and 80°C for 6 hours using a magnetic stirrer to carry out the acid leaching reaction. The metal leaching rate of the acid leaching reaction was calculated using the same method as in Example 2, and the results are shown in Figure 11.

[0061] 2. Experimental results: As shown in Figure 11, the amount of nickel metal leaching varied with the increase of deionized water in the added hydrolysis solution. It is estimated that this was due to the uneven distribution of nickel metal in the aluminum-nickel slag, and the change in the volume of the hydrolysis solution was not the main reason.

[0062] Based on the above, Examples 7-8 confirm that high leaching rate and high recovery rate can be achieved under the conditions of using 200 mL, 300 mL, 400 mL, and 500 mL of deionized water as the hydrolysis solution.

[0063] [Qualitative Analysis of the Properties of Al(OH)3 and Ni(OH)2 Obtained from the Recovery of Valuable Metals from Aluminum-Nickel Slag Using High-Temperature Dry Calcination]

[0064] [Example 9]

[0065] 1. Experimental Procedure: 25g of dried aluminum-nickel slag was mixed with 40g of sodium hydroxide (NaOH). The mixture was then placed in a high-temperature furnace and calcined at 900°C for 20 minutes. Hydrolysis was then carried out using 1000 mL of deionized water at 105°C for 24 hours. Subsequently, the mixture was centrifuged at 1500 rpm for 10 minutes to obtain the alkali-dissolved residue and filtrate. To extract aluminum ions from the filtrate, 500 mL of the filtrate was titrated with 10M sulfuric acid solution. When the pH reached 6.64, Al(OH)3 precipitate formed. The precipitate was washed with water and then subjected to centrifugation, filtration, and drying to obtain high-purity Al(OH)3. Finally, the high-purity Al(OH)3 was analyzed using powder X-ray diffraction analysis and scanning electron microscopy.

[0066] The X-ray diffraction analyzer parameters were as follows: a powder X-ray diffraction analyzer (XRD: Bruker-D2 Phaser) was used; the X-ray source was an anode copper target (Cu Kαλ = 0.154060 nm) and a 300W high-voltage power supply. The goniometer system was a vertical θ-θ architecture.

[0067] The analytical parameters for the scanning electron microscope were as follows: a scanning electron microscope (SEM: Hitachi S-3400N) was used, the electron gun was a tungsten filament, and the accelerating voltage was 15.0 kV.

[0068] 2. Experimental Results: First, Figure 12 shows the analysis results from the powder X-ray diffraction analyzer, indicating that the obtained precipitate conforms to the crystal structure of Al(OH)₃-bayerite. Figure 13 is a SEM image taken by a scanning electron microscope, and Figure 14 is a further SEM-EDS analysis of Figure 13. As shown in Figure 14, aluminum constitutes the majority of the recovered material, confirming the successful recovery of Al(OH)₃.

[0069] [Example 10]

[0070] 1. Experimental Procedure: The residue from Example 9 was dried and subjected to acid leaching using 1M sulfuric acid solution and a magnetic stirrer at 300 rpm and 80°C for 6 hours. After the acid leaching reaction, a first centrifugal filtration was performed. The first filtrate was titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate was then titrated with sodium hydroxide solution to a pH of 10-10.5, followed by a third centrifugal filtration. The precipitate from the third centrifugal filtration was Ni(OH)₂ precipitate. After washing the precipitate with water, high-purity Ni(OH)₂ was obtained through centrifugal filtration and drying. Finally, the high-purity Ni(OH)₂ was analyzed using a powder X-ray diffraction analyzer and a scanning electron microscope.

[0071] 2. Experimental Results: First, Figure 15 shows the analysis results from the powder X-ray diffraction analyzer. It can be seen that the peak shape of the obtained precipitate matches the crystal structure of Ni(OH)₂ corresponding to the red line. Figure 16 is a SEM image taken by a scanning electron microscope, and Figure 17 is a further SEM-EDS analysis of Figure 16. As shown in Figure 17, nickel constitutes the majority of the recovered material, confirming the successful recovery of Ni(OH)₂.

[0072] [Example 11]

[0073] The metal element content in the Al(OH)3 and Ni(OH)2 samples obtained in Examples 9 and 10 was measured using microwave attenuation. The measurement results are shown in Table 1. Based on the results in Table 1, the purity of Al(OH)3 was calculated to be (34.3 / 27) x (27 + 17 x 3) = 99%; and the purity of Ni(OH)2 was calculated to be (63.38 / 59) x (59 + 17 x 2) = 99.9%. Therefore, even considering the error in microwave attenuation detection, it can be conservatively deduced that the purity of Al(OH)3 and Ni(OH)2 obtained by the system and method for high-temperature dry calcination recovery of valuable metals from aluminum-nickel slag of the present invention can be as high as 98% or even above 99%.

[0074] Table 1 Metal element content (%) Al(OH)3 Ni(OH)2 V 0.11 0.015 Mo 0.13 0.016 Ni 0 63.38 Al 34.3 0.001 Co 0 0 P 0 0.031 Fe 0 0.047 Si 0.11 0.025

[0075] none

Claims

1. A method for recovering valuable metals from aluminum-nickel slag using high-temperature dry calcination, comprising the following steps: S1 mixing step, mixing the aluminum-nickel slag with solid sodium hydroxide to obtain mixture one; S2 high-temperature dry calcination step, subjecting mixture one to high-temperature calcination to obtain mixture two; S3 hydrolysis step, subjecting mixture two to a hydrolysis reaction to obtain mixture three; S4 centrifugation and filtration step, subjecting mixture three to centrifugation and filtration to obtain residue and filtrate; S5 aluminum ion extraction step, subjecting the filtrate to a precipitation reaction to obtain Al(OH)3 precipitate; S6 nickel ion extraction step, subjecting the residue to an acid leaching reaction and further processing to obtain Ni(OH)2 precipitate; wherein, The S6 nickel ion extraction step involves adding the residue to a sulfuric acid solution and stirring with a magnetic stirrer to carry out the acid leaching reaction. After the reaction, a first centrifugal filtration is performed. The first filtrate is titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate is then titrated with sodium hydroxide solution to a pH of 10-10.5 and subjected to a third centrifugal filtration to obtain the Ni(OH)2 precipitate.

2. The method as described in claim 1, wherein, The weight ratio of the aluminum-nickel slag to the sodium hydroxide solid is 1:0.4 to 1:2.

4.

3. The method as described in claim 1, wherein, The hydrolysis step involves reacting 200-500 mL of deionized water at 100-120°C for 18-26 hours.

4. A system for recovering valuable metals from aluminum-nickel slag using high-temperature dry calcination, comprising: a mixing device for mixing the aluminum-nickel slag with solid sodium hydroxide to obtain mixture one; a high-temperature dry calcination device for calcining mixture one at high temperature to obtain mixture two; a hydrolysis device for hydrolyzing mixture two to obtain mixture three; a centrifugal filtration device for centrifuging and filtering mixture three to obtain residue and filtrate; an Al(OH)3 precipitation device for precipitating the filtrate to obtain Al(OH)3 precipitate; and a Ni(OH)2 precipitation device for acid leaching and further treatment of the residue to obtain Ni(OH)2 precipitate; wherein... The Ni(OH)2 precipitation apparatus involves adding the residue to a sulfuric acid solution and stirring with a magnetic stirrer to carry out the acid leaching reaction. After the reaction, a first centrifugal filtration is performed. The first filtrate is titrated with sodium hydroxide solution to a pH of 6-6.7, followed by a second centrifugal filtration. The second filtrate is then titrated with sodium hydroxide solution to a pH of 10-10.5 and subjected to a third centrifugal filtration to obtain the Ni(OH)2 precipitate.

5. The system as described in claim 4, wherein, The hydrolysis device uses the hydrolysis reaction to dissolve aluminum ions from the solid of mixture two into the liquid of mixture three.

6. The system as described in claim 4, wherein, The Al(OH)3 precipitation device is used to titrate the filtrate to a pH of 6-6.7 to produce a precipitate, and then centrifuge and filter it to obtain the Al(OH)3 precipitate.

7. The system as described in claim 4, wherein, The high-temperature dry roasting device roasts the mixture at 800~1000°C for 10 minutes to 1 hour.

8. The system as described in claim 4, wherein, The weight ratio of the aluminum-nickel slag to the sodium hydroxide solid is 1:0.4 to 1:2.

4.

9. The system as described in claim 4, wherein, The weight of the aluminum-nickel slag is 5~25g.

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