Method for removing arsenic and recovering copper from black copper sludge

Abstract

The invention discloses a method for removing arsenic and recovering copper from black copper sludge, and belongs to the technical field of secondary resource recovery of nonferrous metals. The method comprises the steps that firstly, oxidation leaching is conducted through oxygen in a sodium hydroxide alkaline medium, arsenic enters a solution in the form of sodium arsenate, valuable metal such as copper is enriched in slag, and efficient separation of arsenic and copper is achieved; copper-containing leaching residues can be returned to a copper smelting system to recover copper; adding calcium hydroxide into the sodium arsenate leachate for precipitation conversion to generate calcium arsenate slag to remove arsenic, and returning the regenerated sodium hydroxide solution to the leaching process for cyclic utilization; the technology is simple, the arsenic removal rate is high, the valuable metal recovery effect is good, regeneration and circulation of the reagent are achieved, and environment friendliness is achieved.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal resource recycling technology, and in particular to a method for removing arsenic from black copper sludge and recovering copper. Technical Background

[0002] Black copper sludge is a copper- and arsenic-containing solid waste generated during the copper electrolyte purification and copper removal process. It has a complex composition, large output, and high copper content, and has great recycling value. However, due to its high arsenic content, it poses a risk of environmental pollution if not disposed of in a timely manner. It needs to be treated promptly and properly to separate the harmful element arsenic and efficiently recover valuable metals such as copper.

[0003] The existing processing techniques for black copper sludge are divided into pyrometallurgical and wet methods. Pyrometallurgical methods include direct roasting and roasting with added chemicals, while wet methods include alkaline leaching and acid leaching.

[0004] The direct roasting method involves mixing black copper sludge and carbon powder in a certain proportion and reacting them at a temperature of 800–1000°C to obtain arsenic trioxide condensate. Other high-boiling-point and non-volatile substances are retained in the material. CN104928501A discloses a method for recovering arsenic from black copper sludge, which uses a one-step vacuum carbon reduction separation to obtain high-purity arsenic trioxide. However, the generated As₂O₃ is highly toxic, posing significant challenges to fume collection and personnel health, and presenting certain safety hazards.

[0005] The reagent-based roasting method involves mixing black copper sludge with an alkaline refining flux (NaOH, Na2CO3, etc.), and then reacting the low-valent arsenic in the black copper sludge with the oxidizing and alkaline refining flux under high temperature conditions to produce sodium arsenate. CN108048664A discloses a method and application for removing arsenic from black copper sludge, in which black copper sludge is roasted with sodium carbonate at 550-700℃, followed by water leaching. The water leaching solution is crystallized multiple times to obtain sodium arsenate and sodium carbonate. However, this method suffers from unstable arsenic element orientation and low overall recovery rate.

[0006] Alkaline leaching has low arsenic recovery efficiency and high alkali consumption, making it difficult to comprehensively recover valuable metals such as silver, antimony, and bismuth. Selective leaching of arsenic from black copper sludge can be achieved by adding alkali or mixed alkali and introducing a strong oxidant (H₂O₂) and air for oxidative leaching. The literature "Study on the Separation of Arsenic from Black Copper Sludge by Oxidative Alkali Leaching" uses sodium hydroxide as the leaching agent and hydrogen peroxide and air as the oxidant, employing staged leaching, leaving copper, antimony, and bismuth in the leaching residue. This process is cumbersome, consumes large amounts of reagents, and has a low metal recovery rate.

[0007] Acid leaching involves oxidizing and leaching black copper sludge in a sulfuric acid medium. Copper in the leachate is mainly recovered as copper sulfate and copper arsenate, while arsenic is recovered as arsenic trioxide and copper arsenate. CN106148702A discloses a method for separating copper and arsenic from black copper sludge, using a sulfuric acid and water hydrogen peroxide leaching process, achieving copper and arsenic leaching rates of 98% and 89%, respectively. This method suffers from high acid consumption, a long process flow, and incomplete separation of arsenic and copper. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for removing arsenic and recovering copper from black copper sludge that has a short process flow, high arsenic removal efficiency, high valuable metal recovery rate, recyclable reagents, and is environmentally friendly.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for removing arsenic and recovering copper from black copper sludge includes the following steps:

[0011] (1) The black copper mud (wet base) was pulped, and oxygen was used as the oxidant and sodium hydroxide as the alkaline leaching agent. The leaching was carried out under high temperature and low pressure conditions to obtain sodium arsenate leaching solution and leaching residue respectively.

[0012] (2) The leaching residue obtained in step (1) above is sent to the copper smelting system as copper raw material to recover copper. The sodium arsenate leaching solution is added to the calcium hydroxide slurry and reacted to precipitate arsenic under high temperature conditions. The resulting calcium arsenate slag is treated as arsenic-containing raw material. The sodium hydroxide regeneration solution is replenished with sodium hydroxide and returned to step (1) black copper mud oxidation alkaline leaching process.

[0013] In step (1), the black copper mud contains 43-45% Cu, 23-27% As, 0.6-0.8% Sb, and 2-3% Ni.

[0014] Furthermore, step (1) high temperature and low pressure conditions refer to the liquid-solid ratio of sodium hydroxide alkaline leaching agent to black copper mud being 8-10 mL: 1 g, oxygen partial pressure being 0.2 MPa, reaction temperature being 60-80 °C, and reaction time being 3-4 h.

[0015] Furthermore, in step (1), oxygen is used as an oxidant and sodium hydroxide as an alkaline leaching agent. Preferably, the oxygen concentration is greater than 90% and the sodium hydroxide concentration is 2-3 mol / L.

[0016] In step (1), the sodium arsenate leachate has an arsenic concentration of 20-24 g / L, the arsenic content in the leachate residue is 0.5-1.5%, the copper content is 50-55%, and the arsenic removal rate reaches over 97.5%.

[0017] Furthermore, the high temperature conditions in step (2) refer to a reaction temperature of 110-120℃, a calcium hydroxide addition amount of 1.5-1.8 times that of sodium arsenate, and a reaction time of 1-2 hours.

[0018] In step (2), the calcium arsenate leaching residue contains 24-30% arsenic and 25-27% calcium. The regenerated sodium hydroxide solution has a sodium hydroxide concentration of 1.5-1.8 mol / L and an arsenic ion concentration of 0.5-1.5 g / L. The regenerated sodium hydroxide solution is replenished to 2-3 mol / L before it can be returned to step (1) as a leaching agent.

[0019] The present invention has the following beneficial effects:

[0020] 1. This invention provides a method for removing arsenic from black copper sludge and recovering copper. The method uses sodium hydroxide as a leaching agent, and oxygen is introduced to oxidize the arsenic, causing it to enter the solution as sodium arsenate, thus separating copper from arsenic. The sodium arsenate solution is then converted into calcium arsenate precipitate by adding calcium hydroxide, simultaneously regenerating the sodium hydroxide leaching agent. This achieves efficient removal of arsenic from black copper sludge and regeneration of the leaching agent, reducing production costs.

[0021] 2. Highly efficient selective arsenic removal: The process of oxygen oxidation combined with alkaline leaching achieves extremely high selective leaching efficiency for arsenic (>97.5%), while effectively inhibiting the dissolution of valuable metals such as copper, nickel, and antimony, causing them to accumulate in the slag for easy subsequent recovery.

[0022] 3. Resource recycling and environmental protection: The sodium hydroxide leaching agent is regenerated simultaneously during the arsenic precipitation process. The regenerated liquid can be recycled, which greatly reduces alkali consumption and production costs. Moreover, there is no process wastewater discharge during the entire process. The arsenic is solidified in the form of chemically stable calcium arsenate, which has low environmental risk.

[0023] 4. Simple process flow: The entire process only includes two core steps: "leaching-arsenic precipitation". It is simple to operate, does not require complicated separation or purification steps, and is easy to implement for industrial application.

[0024] 5. Significant economic benefits: While efficiently removing the harmful element arsenic, it achieves a high recovery rate (>98.5%) of valuable metals such as copper, and has a high degree of comprehensive resource utilization. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0026] The present invention can be further described through the following embodiments; however, the scope of the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] according to Figure 1 The process flow diagram shown is followed.

[0029] Two kg of wet black copper mud (Cu 45.27%, As 26.74%, Ni 3.45%, Sb 0.65%) was slurried with water and reacted for 4 h at a reaction temperature of 60℃, a sodium hydroxide concentration of 2.5 mol / L, a sodium hydroxide solution to black copper mud powder ratio of 10 mL:1 g, and an oxygen partial pressure of 0.2 MPa. After the reaction, solid-liquid separation was performed to obtain sodium arsenate leaching solution and leaching residue. The leaching residue (Cu 51.58%, As 0.62%, Sb 1.09%, Ni 4.82%) and sodium arsenate solution (As 23.6 g / L) were also obtained. The leaching residue was returned to the copper smelting system to recover copper.

[0030] 20 L of sodium arsenate leachate was mixed with 839 g of calcium hydroxide (1.8 times the amount of arsenic ions in the solution), and the mixture was reacted at 120 °C for 2 hours. After the reaction, the solid and liquid phases were separated to obtain 1312 g of wet calcium arsenate slag and a sodium hydroxide regeneration solution (As 0.62 g / L, sodium hydroxide 2.33 mol / L). The sodium hydroxide regeneration solution was supplemented with 136 g of sodium hydroxide to bring the concentration to 2.5 mol / L before being returned to the black copper mud leaching process.

[0031] Example 2

[0032] according to Figure 1 The process flow diagram shown is followed.

[0033] Two kg of black copper mud balls (Cu 43%, As 22.95%, Ni 3.35%, Sb 0.67%) were slurried with water and reacted for 3 h at a reaction temperature of 80℃, a sodium hydroxide concentration of 2.5 mol / L, a sodium hydroxide solution to black copper mud powder ratio of 10 mL:1 g, and an oxygen partial pressure of 0.2 MPa. After the reaction, solid-liquid separation was performed to obtain sodium arsenate leaching solution and leaching residue. The leaching residue (Cu 45.6%, As 1.02%, Sb 1.19%, Ni 4.46%) and the sodium arsenate solution (As 21.8 g / L) were also obtained. The leaching residue was returned to the copper smelting system to recover copper.

[0034] 20 L of sodium arsenate leachate was mixed with 645 g of calcium hydroxide (1.5 times the amount of arsenic ions in the solution), and the mixture was reacted at 120 °C for 2 hours. After the reaction, the solid and liquid phases were separated to obtain 1019 g of wet calcium arsenate slag and a sodium hydroxide regeneration solution (As 0.82 g / L, sodium hydroxide 2.28 mol / L). The sodium hydroxide regeneration solution was supplemented with 176 g of sodium hydroxide to bring the concentration to 2.5 mol / L before being returned to the black copper mud leaching process.

Claims

1. A method for removing arsenic and recovering copper from black copper sludge, characterized in that, The method includes the following steps: (1) The black copper mud (wet base) was pulped, and oxidized and leached under high temperature and low pressure conditions with oxygen as the oxidant and sodium hydroxide as the alkaline leaching agent to obtain sodium arsenate leachate and leaching residue respectively; (2) The above-obtained leaching residue is sent to the copper smelting system as copper raw material to recover copper. The sodium arsenate leaching solution is added to calcium hydroxide slurry and reacted under high temperature conditions to precipitate arsenic, resulting in calcium arsenate slag and sodium hydroxide regeneration solution.

2. The method for removing arsenic and recovering copper from black copper sludge according to claim 1, characterized in that, The oxygen concentration is greater than 90%.

3. The method for removing arsenic and recovering copper from black copper sludge according to claim 1, characterized in that, In step (1), the concentration of the alkaline leaching agent is 2 to 2.5 mol / L.

4. The method for removing arsenic and recovering copper from black copper sludge according to claim 1, characterized in that, The high temperature and low pressure conditions in step (1) refer to the liquid-solid ratio of sodium hydroxide alkaline leaching agent to black copper mud being 8-10 mL: 1 g, the oxygen partial pressure being 0.2 MPa, the reaction temperature being 60-80 °C, and the reaction time being 3-4 h.

5. The method for removing arsenic and recovering copper from black copper sludge according to claim 1, characterized in that, The high-temperature conditions in step (2) refer to a reaction temperature of 110-120℃, a calcium hydroxide addition amount of 1.5-1.8 times that of sodium arsenate, and a reaction time of 1-2 hours.

6. The method for removing arsenic and recovering copper from black copper sludge according to claim 1, characterized in that, After calcium hydroxide precipitates arsenic, the resulting arsenic-precipitated liquid is a sodium hydroxide regeneration liquid. After adding 0.2 to 0.4 mol / L sodium hydroxide, it can be returned to step (1) as a leaching agent.

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