Low-cost method for removing arsenic and fixing arsenic from black copper sludge of regenerated copper

Abstract

The invention discloses a low-cost method for removing arsenic and fixing arsenic from regenerated copper black copper sludge, which comprises the following steps: mixing regenerated copper black copper sludge with an alkaline soluble solution, adding an oxidizing agent to convert As into arsenate to enter the solution and copper enters slag under an alkaline condition to realize arsenic-copper separation in one step, and then stirring, slurrying and wet-grinding the arsenate solution and calcium oxide to obtain the arsenic-containing copper sludge. According to the method, arsenate and calcium oxide are subjected to a chemical reaction to convert arsenate into calcium arsenate precipitate, and calcium oxide is exposed all the time through wet grinding and can be continuously subjected to a contact reaction with an arsenic-containing solution, so that arsenic is removed under the low-calcium condition, a large amount of soluble alkali is prevented from being consumed, and the reaction efficiency is greatly improved; and the recovered filtrate and cleaning liquid are used as leaching liquid (soluble alkali solution) for cyclic leaching, so that zero wastewater discharge of the process is realized, and the industrial cost is reduced. The copper recovery rate reaches 99% or above, the arsenic removal rate reaches 95% or above, and the open circuit efficiency is high. The arsenic finally exists in the form of calcium arsenate, and the arsenic-calcium ratio of the calcium arsenate is high.

Description

Technical Field

[0001] This invention relates to the field of recycled copper black sludge treatment technology, and in particular to a low-cost method for arsenic removal and fixation of recycled copper black sludge. Background Technology

[0002] At the end of the recycled copper industry, electrolytic copper is obtained through electrolysis. The electrolysis process involves further removing impurities from the anode plate (approximately 99% copper grade) to produce cathode copper with a copper grade of 99.99%. Major impurities such as arsenic and nickel enter the electrolyte, which needs to be purified to remove these impurities, ensuring that the cathode plate does not become substandard due to impurity accumulation. The electrolysis process continues with the removal of nickel sulfate through concentration and crystallization or freeze-crystallization. During the removal of copper and arsenic by electrowinning, slurry is produced at the bottom of the electrowinning cell, which, after filtration, becomes black copper sludge. Compared to black copper sludge from concentrate raw materials, the black copper sludge from recycled copper is further enriched in Cu and As, containing 35-60% copper and 20-30% As, with lower levels of antimony, bismuth, and lead (below 3%). In contrast, the black copper sludge from concentrate raw materials has higher levels of antimony, bismuth, and lead, reaching over 5%. Therefore, compared to black copper sludge from concentrate raw materials, the valuable metals in the black copper sludge from recycled copper can be considered mainly copper and arsenic.

[0003] There is a method for recovering arsenic from recycled copper black sludge. First, alkaline leaching is performed on the recycled copper black sludge using an alkaline leaching solution. Then, excess lime is added to the leaching solution, and solid-liquid separation is performed to remove the arsenic completely. The filter residue is then roasted with a reducing agent, and the roasting flue gas is cooled to obtain the arsenic. In this technical solution, the addition of excess calcium oxide results in calcium content in the solution after arsenic removal, which affects the subsequent arsenic leaching efficiency. At the same time, excess lime will carry away a large amount of alkaline solution, requiring the replenishment of highly soluble alkali, resulting in high operating costs. Moreover, the roasting process consumes a lot of energy, which is not conducive to cost reduction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a low-cost method for dearsenic removal and fixation of arsenic in recycled copper black copper mud with high copper recovery rate and high arsenic removal rate.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A low-cost method for arsenic removal and fixation in recycled copper black sludge includes the following steps: S1, the recycled copper black copper mud is stirred and mixed with an alkaline solution, and an oxidant is added at a temperature of 70-200℃ for stirring and reaction, solid-liquid separation is performed to obtain leaching residue and arsenate alkaline solution; S2, the arsenate alkaline solution and calcium oxide are stirred, slurried, and wet-milled to obtain a slurry; the mass of calcium in the calcium oxide is 0.55 to 0.75 times the mass of total arsenic in the recycled copper black sludge; the amount of calcium oxide means that during stirring and slurrying, arsenic is not completely removed, but a certain amount of arsenic is removed, so that the solution after arsenic removal is calcium-free. Only this calcium-free solution can be used again to leach the recycled copper black sludge without affecting the leaching efficiency of the recycled copper black sludge in subsequent recycling, so that the alkaline solution can be recycled and only a small amount of alkaline solution needs to be added during long-term operation.

[0006] S3, the slurry is filtered by pressure to obtain filter residue and filtrate. After washing the filter residue, relatively pure calcium arsenate residue with a high arsenic-to-calcium ratio and washing liquid are obtained. The filtrate and washing liquid are recovered and used as raw materials for the alkaline solution in step S1. In the relatively pure calcium arsenate residue with a high arsenic-to-calcium ratio, the mass ratio of arsenic to calcium is higher than 1.2.

[0007] As a further improvement to the above technical solution: In step S1, the liquid-to-solid ratio (the ratio of liquid volume (liters) to solid mass (kg)) of the recycled copper black sludge and the alkaline solution is 2 to 10:1, and the molar concentration of the alkaline solution is 1 mol / L to 10 mol / L.

[0008] In step S1, the oxidant is one or more of hydrogen peroxide, oxygen, air, and ozone, and the stirring reaction time is 1-5 hours.

[0009] In step S2, the wet grinding time is 0.5-4 hours, and the wet grinding mill speed is 100 r / min to 600 r / min.

[0010] In step S2, the temperature of the stirring and slurrying is 0℃-100℃, and the stirring speed is 100r / min~600r / min.

[0011] In step S3, the pH of the cleaning solution is 6-7.

[0012] In step S1, the main components of the recycled copper black sludge, by weight percentage, include: Cu 30%-60%, As 20%-40%, Pb 1%-3%, Bi 1%-3%, and Sb 1%-3%.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a low-cost method for arsenic removal and fixation in recycled copper black sludge. First, the recycled copper black sludge is mixed with NaOH solution, and an oxidant is added, causing As to convert into arsenate and enter the solution. Copper, under alkaline conditions, enters the slag, achieving arsenic-copper separation in one step. Then, the arsenate solution and calcium oxide are stirred, slurried, and wet-milled, allowing the arsenate and calcium oxide to chemically react, converting the arsenate into calcium arsenate precipitate. No calcination is required. Wet milling keeps the calcium oxide exposed, allowing it to continuously react with the arsenic-containing solution, achieving arsenic removal under low calcium conditions. This avoids the large consumption of alkaline solution, significantly improving reaction efficiency. The recovered filtrate and washing liquid are used as leaching solutions (alkaline solutions) for cyclic leaching, achieving zero wastewater discharge and reducing industrial costs. This invention achieves a high copper recovery rate of over 99% and an arsenic removal rate of over 95%. The arsenic ultimately exists in the form of calcium arsenate with high purity, an arsenic-to-calcium mass ratio greater than 1.2, and good solidification effect. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0015] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0016] Example 1: like Figure 1 As shown in this embodiment, a low-cost method for arsenic removal and fixation in recycled copper black sludge is described. The main components (%) of the recycled copper black sludge in this embodiment are: Cu 40.30%, As 27.14%, Pb 2.20%, Bi 1.31%, Sb 1.13%; sodium hydroxide, potassium hydroxide, and calcium oxide are all industrial-grade reagents. The method includes the following steps: S1, at 15m 3 Add 2500.0 kg of dry copper sludge to an atmospheric pressure reactor. Prepare water according to the ratio of water volume (L) to dry weight of copper sludge (kg) of 4. Start stirring at 200 r / min. Slowly add 800 kg of 2 mol / L NaOH aqueous solution, maintaining a liquid-to-solid ratio of 4.32. Heat uniformly to 80℃, and introduce air from the bottom at a flow rate of 200 m³ / min. 3 The mixture is stirred for 3 hours, and then stirred until the reaction is complete. The mixture is then filtered to obtain copper-containing leaching residue and an arsenate alkaline solution (sodium arsenate alkaline solution in this example). The copper-containing leaching residue is then fed into a smelting furnace to recover copper.

[0017] The dried copper-containing leaching residue weighed 1523.5 kg. Analysis revealed that it contained 66.13% copper, 0.96% arsenic, 3.45% lead, 1.89% bismuth, and 1.63% antimony. The arsenic leaching rate was 97.84%. Almost all the copper was recovered through smelting in the residue.

[0018] S2, pump the arsenate alkaline solution into the slurry tank. The arsenic content of the arsenate solution is 66.80 g / L. Add calcium oxide at 49 g Ca / L (49 g calcium per liter of arsenate solution) and stir at 100 r / min to slurry. Then transfer it to a wet mill at 300 r / min for a residence time of 1 h to obtain the slurry.

[0019] Wet milling keeps calcium oxide exposed, allowing it to continuously react with the arsenic-containing solution, thus achieving arsenic removal under low calcium conditions. This avoids the large consumption of soluble alkali and significantly improves reaction efficiency. Wet milling is key to achieving low calcium oxide usage, and the two have a synergistic effect.

[0020] S3, the slurry is filtered by pressure to obtain 9.0 ml of filtrate. 3 The calcium arsenate slag was washed with water in a filter press until the pH of the wash water was 7, yielding 0.65 ml of wash water. 3 The filtrate and wash water are returned to the arsenic immersion kettle made of black copper mud.

[0021] The calcium arsenate slag, weighing 1820 kg after drying, has the following composition: As 38.56%, Ca 29.08%, Bi 0.25%, Pb 0.16%, Sb 0.56%, and has a high arsenic-to-calcium ratio of 1.33, indicating that the main component of the calcium arsenate slag is calcium arsenate.

[0022] Example 2: This embodiment presents a low-cost method for arsenic removal and fixation in recycled copper black sludge. The main components of the recycled copper black sludge in this embodiment, by weight percentage (%), are: Cu 35.32%, As 27.48%, Pb 2.52%, Bi 1.15%, Sb 2.67%; sodium hydroxide and calcium oxide are industrial-grade reagents. The method includes the following steps: S1. Prepare 600 ml of a 1.5 mol / L NaOH solution in a 1 L pressure reactor using water and sodium hydroxide. Add 120 g of dry black copper sludge, maintaining a liquid-to-solid ratio of 5. After sealing, start stirring at 400 rpm, maintain an oxygen pressure of 2 MPa, raise the temperature to 150°C, and stir for 2 hours. After the reaction is complete, stop stirring, turn off the oxygen pressure, cool to 90°C, and filter to obtain copper-containing leaching residue and an arsenate alkaline solution (sodium arsenate alkaline solution in this example). Smelt the copper-containing leaching residue to recover copper.

[0023] The copper-containing leaching residue weighed 78.47g after drying. Analysis showed it contained 54.20% copper, 0.32% arsenic, 2.96% lead, 1.50% bismuth, and 2.45% antimony, with an arsenic leaching rate of 99.24%. This indicates that almost all the copper was smelted and recovered.

[0024] S2, the arsenate alkaline solution is transferred to a 1L slurry reaction vessel. The arsenate solution contains 54.08g / L of arsenic. 38.0g / L of calcium oxide is added and the mixture is stirred at 100r / min for slurrying. Then, it is transferred to a wet mill at 400r / min for wet milling with a residence time of 2h to obtain the slurry. S3, the slurry is filtered by pressure to obtain 502 ml of filtrate and calcium arsenate residue. The calcium arsenate residue is washed with water until the pH of the wash water is 7, and 50 ml of wash water is obtained. The filtrate and wash water are returned to the black copper mud arsenic immersion kettle.

[0025] The calcium arsenate slag, after drying, weighed 85.0g. Its composition was As 38.18%, Ca 26.80%, Bi 0.83%, Pb 0.46%, Sb 0.05%, and the arsenic-to-calcium ratio was 1.42, indicating that the main component of the calcium arsenate slag was calcium arsenate.

[0026] Example 3: This embodiment presents a low-cost method for arsenic removal and fixation in recycled copper black sludge. The main components of the recycled copper black sludge in this embodiment, by weight percentage (%), are: Cu 35.32%, As 27.48%, Pb 2.52%, Bi 1.15%, Sb 2.67%; sodium hydroxide and calcium oxide are industrial-grade reagents. The method includes the following steps: S1. Prepare 660 ml of a 2 mol / L NaOH solution in a beaker using water and sodium hydroxide. Add 120 g of dry black copper sludge, and then add hydrogen peroxide at a rate of 1 ml / min, maintaining a total liquid-to-solid ratio of 7:1. Stir at 400 rpm, heat to 80°C, and react for 2 hours. After the reaction is complete, stop stirring and adding hydrogen peroxide. Filter to obtain copper-containing leaching residue and an arsenate alkaline solution. Smelt the copper-containing leaching residue to recover copper.

[0027] The copper-containing leaching residue weighed 77.11g after drying. Testing revealed it contained 54.90% copper and 1.72% arsenic. The arsenic leaching rate was 95.98%, and almost all the copper was recovered through smelting. S2, the arsenate alkaline solution is transferred to a 1L slurry reaction vessel. The arsenate solution contains 45.2g / L of arsenic. 32.0g / L of calcium oxide is added and the mixture is stirred at 100r / min for slurrying. Then, it is transferred to a wet mill at 400r / min for wet milling with a residence time of 3h to obtain the slurry. S3, the slurry is filtered by pressure to obtain 640ml of filtrate and calcium arsenate residue. The calcium arsenate residue is washed with water until the pH of the wash water is 7, and 60ml of wash water is obtained. The filtrate and wash water are returned to the black copper mud leaching.

[0028] The calcium arsenate slag, after drying, weighed 82.5g. Its composition was As 35.08%, Ca 26.85%, and the arsenic-to-calcium ratio was 1.31, indicating that the main component of the calcium arsenate slag was calcium arsenate.

[0029] Comparative Example 1: This comparative example is a conventional method for removing and fixing arsenic from recycled copper black sludge, which is largely the same as that in Example 3, except that wet grinding is not performed in step S2.

[0030] Testing revealed that the arsenic content in the filtrate was 10.23 g / L, and the solid phase was calcium arsenate slag. The total amount of calcium arsenate slag was 87.2 g, with the following composition: As 27.66%, Ca 28.82%. The arsenic-to-calcium ratio was only 0.96, indicating that the calcium arsenate slag was a mixture of calcium arsenate and calcium hydroxide. Existing conventional methods for arsenic removal and fixation are ineffective in fixing arsenic.

[0031] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A low-cost method for arsenic removal and fixation in recycled copper black sludge, characterized in that: Includes the following steps: S1, the recycled copper black copper mud is stirred and mixed with an alkaline solution, and an oxidant is added at a temperature of 70-200℃ for stirring and reaction, solid-liquid separation is performed to obtain leaching residue and arsenate alkaline solution; S2, the arsenate alkaline solution and calcium oxide are stirred and pulped, and then wet-milled to obtain a pulp liquid; the mass of calcium in the calcium oxide is 0.55 to 0.75 times the mass of total arsenic in the recycled copper black copper mud; S3, the slurry is filtered by pressure to obtain filter residue and filtrate. After washing the filter residue, calcium arsenate residue and washing liquid are obtained. The filtrate and washing liquid are recovered and used as raw materials for the alkaline solution in step S1.

2. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S1, the liquid-to-solid ratio of the recycled copper black sludge to the alkaline solution is 2~10:1, and the molar concentration of the alkaline solution is 1mol / L~10mol / L.

3. The method for low-cost arsenic removal and fixation of recycled copper black copper sludge according to claim 1, characterized in that: In step S1, the oxidant is one or more of hydrogen peroxide, oxygen, air, and ozone, and the stirring reaction time is 1-5 hours.

4. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S2, the wet grinding time is 0.5-4 hours, and the wet grinding mill speed is 100 r / min to 600 r / min.

5. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S2, the temperature of the stirring and slurrying is 0℃-100℃, and the stirring speed is 100r / min~600r / min.

6. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S3, the pH of the cleaning solution is 6-7.

7. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S1, the main components of the recycled copper black sludge, by weight percentage, include: Cu 30%-60%, As 20%-40%, Pb 1%-3%, Bi 1%-3%, and Sb 1%-3%.

8. The low-cost method for arsenic removal and fixation in recycled copper black sludge according to claim 1, characterized in that: In step S1, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

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