Treatment method of cuprous cyanide-containing solid waste
Sodium percudate was prepared by treating cuprous cyanide-containing solid waste with oxidizing reagents at different pH values, solving the treatment problems in existing technologies and realizing resource utilization and safe operation.
Patent Information
- Application Number
- CN202411437180.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-15
- Publication Date
- 2025-01-17
AI Technical Summary
Existing technologies struggle to treat solid waste containing cuprous cyanide, especially since it is insoluble in water, resulting in a lack of treatment methods and difficulty in recovering the high-purity copper element.
The solid waste containing cuprous cyanide was dissolved using sodium hydroxide solution. The copper element was converted into sodium percudate product through a two-stage oxidation reaction using oxidizing reagents at different pH values. The oxidation process included a first stage at pH 11–13 and a second stage at pH 7–9, followed by pressure filtration, washing, and drying.
This method enables the resource utilization of cuprous cyanide-containing solid waste, producing high-purity sodium percudate, thus avoiding resource waste and ensuring operational safety.
Smart Images
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Figure BDA0005085359830000071
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of hazardous waste treatment, and in particular to a method for treating solid waste containing cuprous cyanide. Background Art
[0002] Cuprous cyanide is a white or slightly green or cyan powder solid. Molecular weight: 89.56, relative density 2.92; melting point 474℃. It is easily soluble in ammonia water, sodium cyanide and concentrated hydrochloric acid, insoluble in water and cold dilute acid, and decomposes into cuprous chloride and hydrogen cyanide in boiling dilute hydrochloric acid. It forms a cyanide-copper complex when dissolved in sodium cyanide, ammonium cyanide and potassium cyanide. Cuprous cyanide cannot burn, but highly toxic hydrogen cyanide gas is generated when it encounters humid air or acids. It reacts violently with nitrates, nitrites and chlorates, and there is a risk of explosion.
[0003] Cuprous cyanide is an inorganic compound with the chemical formula CuCN. It is mainly used for electroplating copper and other alloys, synthesizing anti-tuberculosis drugs and antifouling coatings. It sometimes appears green because it is mixed with divalent copper. Cuprous cyanide can be obtained by the reaction of copper sulfate and sodium cyanide solution, and cyanide gas is released.
[0004] The current problems in the treatment of cuprous cyanide powder are as follows: (1) Cuprous cyanide is insoluble in water, so the general methods for treating cyanide-containing wastewater are not applicable to this process, and related processes are lacking; (2) The solid waste containing cuprous cyanide contains a large amount of copper elements with recycling value, making it difficult to recover non-toxic, high-purity sodium percolate products from the cuprous cyanide powder. Summary of the invention
[0005] The purpose of the present invention is to provide a method for treating solid waste containing cuprous cyanide, converting the copper element therein into a sodium percopperate product, thereby realizing resource utilization of the waste.
[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for treating solid waste containing cuprous cyanide, comprising the following steps:
[0007] (1) Solid dissolution: adding solid waste containing cuprous cyanide into a sodium hydroxide solution to obtain a dissolving solution;
[0008] (2) One-stage oxidation: adjusting the pH of the solution to 11-13, adding an oxidizing agent to the solution, and obtaining a first reaction solution after reaction;
[0009] (3) Secondary oxidation: adjust the pH of the first reaction solution to 7-9, continue to add an oxidizing agent, and obtain a second reaction solution after reaction;
[0010] (4) Product treatment: The second reaction liquid is subjected to filter pressure to obtain a filter cake, which is then soaked in a sodium hydroxide solution for 3 days and then in sodium hypochlorite for 3 days, and then washed and dried to obtain a sodium percolate solid.
[0011] Specifically, in step (1), the mass concentration of the sodium hydroxide solution is 2% to 5%. In step (2), the pH of the dissolving solution is adjusted to 12, and in step (3), the pH of the first reaction solution is adjusted to 8. In steps (2) and (3), the oxidizing agent is sodium hypochlorite. In step (4), the washing and drying are first washed with anhydrous ethanol, then washed with tetrahydrofuran, and dried at 40°C for 8 hours.
[0012] In the above scheme, cuprous cyanide in solid waste is partially dissolved with alkali solution, and then cuprous cyanide is oxidized with an oxidizing agent under different pH conditions to prepare sodium percolate, which is then separated to obtain a sodium percolate product. The scheme of the present invention is not only simple to operate and safe to dispose of, but also turns recyclable resources in waste into treasure, thus avoiding waste of resources.
[0013] The reaction principle utilized in the present invention is:
[0014] Stage 1: 2CuCN+4NaClO+2H2O=2Cu(OH)2↓+2NaCNO+2NaCl(pH=12)
[0015] 2Cu(OH)2+2NaOH+NaClO=2NaCuO2↓+NaCl+3H2O (pH=12)
[0016] The second stage: 2NaCNO+3NaClO+H2O=2CO2↑+N2↑+2NaOH+5NaCl (pH=8)
[0017] Experimental principle: 2CuCN+7NaClO+3H2O=2Cu(OH)2↓+2CO2↑+N2↑+2NaOH+7NaCl DETAILED DESCRIPTION
[0018] The technical solution of the present invention is further described below.
[0019] A method for treating solid waste containing cuprous cyanide comprises the following steps:
[0020] (1) Solid dissolution: solid waste containing cuprous cyanide is added to a sodium hydroxide solution and dissolved to obtain a partially dissolved cuprous cyanide solution;
[0021] (2) One-stage oxidation: adjusting the solution to be alkaline, adding an oxidant to the solution, completely oxidizing cuprous ions and cyanide ions, obtaining a first reaction solution, and preparing sodium percuprate solid;
[0022] (3) Secondary oxidation: Add dilute acid to the first reaction solution to adjust the pH of the solution to about 8, continue to add oxidant, and perform secondary oxidation on the first reaction solution to obtain a mixed solution;
[0023] (4) Product treatment: The mixed solution is filtered by filter press to obtain a filter cake, which is soaked in a sodium hydroxide solution for 3 days and then in sodium hypochlorite for 3 days, and then washed with anhydrous ethanol and then with tetrahydrofuran, and dried at low temperature to obtain a sodium percolate solid.
[0024] The invention adds cuprous cyanide solid into a sodium hydroxide solution to dissolve it, and obtains a partial dissolved liquid after sufficient stirring; adjusts the dissolved liquid to be alkaline (pH 11-13, preferably 12), adds an oxidizing solution, and stirs to make cuprous ions and cyanide ions in the solution fully react to obtain a first reaction liquid, and after oxidation by the oxidizing liquid, the cuprous ions in the solution are first oxidized to cupric ions, and further oxidized to high cupric ions; then, acid is added to adjust the pH of the first reaction liquid to 7-9, preferably about 8, and the oxidizing liquid is continuously added for oxidation to completely oxidize the cyanate ions in the solution to carbon dioxide and nitrogen, thereby completing the cyanide breaking treatment of the cyanide ions; and filter presses the mixed liquid to obtain a filter cake, and the filter cake is soaked in a sodium hydroxide solution for 3 days, and then soaked in sodium hypochlorite for 3 days, and then washed with anhydrous ethanol, and then washed once with tetrahydrofuran, and dried at a low temperature to obtain a sodium high cuprate solid.
[0025] Preferably, the sodium hydroxide solution has a content of 2% to 5%.
[0026] Further preferably, the sodium hydroxide solution dissolves cuprous cyanide at 30° C., which can accelerate the dissolution of cuprous cyanide, but about 25% of cuprous cyanide powder can be dissolved. Under alkaline conditions, the solution changes from cyan to blue-green. Since cuprous cyanide contains some copper ions, copper hydroxide is generated.
[0027] Preferably, before adding an oxidizing liquid to the first oxidation step to fully oxidize the cuprous ions and cyanide ions, it is necessary to adjust the solution pH to 12 to provide reaction conditions for preparing sodium percuprate; the oxidizing liquid is a sodium hypochlorite liquid, and the sodium hypochlorite oxidizes the cuprous ions into sodium percuprate and sodium percuprate precipitation, and the cyanide ions are oxidized into cyanate, thereby obtaining a first reaction solution. To ensure that the cuprous ions and cyanide ions are oxidized by sodium hypochlorite, the ORP value is simultaneously controlled to be stable at 300mV-350mV, and if there is any fluctuation, sodium hypochlorite needs to be added.
[0028] Preferably, the pH of the solution is first reduced to about 8, and then an oxidizing liquid sodium hypochlorite is added to the first reaction solution to fully oxidize the cyanate ions. Sodium hypochlorite completely oxidizes the cyanate into carbon dioxide and nitrogen, thereby achieving safe treatment of cuprous cyanide. To ensure that the cyanate ions are oxidized by sodium hypochlorite, the ORP value is simultaneously controlled to be stable at 600mV-650mV. If there is any fluctuation, sodium hypochlorite needs to be added.
[0029] Preferably, the product processing process is as follows: soaking the sodium percopperate solid in a 5% sodium hydroxide solution for 3 days, then testing the cyanide content of the sodium hydroxide solution; if the cyanide content in the solution is greater than 0.5 mg / L, continuing to react the solution with sodium hypochlorite and soaking it in sodium hypochlorite for one week and stirring and sampling for testing until the cyanide content is less than 0.5 mg / L; if the cyanide content in the sodium hydroxide solution is less than 0.5 mg / L, soaking the solid in sodium hypochlorite for 3 days and then washing it with anhydrous ethanol, and drying the filter residue.
[0030] Preferably, the sodium percopperate solid is dried at 40° C. for 8 hours to prepare sodium percopperate.
[0031] The invention utilizes that cuprous cyanide is insoluble in water but can be dissolved in a sodium hydroxide solution. Cuprous cyanide powder is added to the sodium hydroxide solution. After stirring, about 25% of the cuprous cyanide can be dissolved to obtain a suspension, which can provide a suitable pH for further cyanide breaking reaction. Then, a sodium hypochlorite solution is pumped in to oxidize cuprous ions and cyanide ions in the suspension. After oxidation by sodium hypochlorite, cuprous ions in the solution are oxidized into percuprate ions, and cyanide ions are completely oxidized into carbon dioxide and nitrogen, completing the cyanide breaking treatment of cyanide ions. Cuprous ions are oxidized by excess sodium hypochlorite under alkaline conditions to generate sodium percuprate solid. Sodium percuprate is rinsed with sodium hypochlorite and then rinsed with anhydrous ethanol, and then rinsed with tetrahydrofuran, and dried at low temperature to obtain sodium percuprate solid.
[0032] In summary, the present invention has the following beneficial effects:
[0033] Firstly, the process flow of the invention is simple and the operation is safe, which solves the problem of treating solid cuprous cyanide, enables the solid waste containing cuprous cyanide to be effectively treated as a resource, and prevents environmental pollution.
[0034] Secondly, the present invention recovers copper elements with recycling value in solid wastes, prepares non-toxic, high-purity sodium percopperate products, and achieves the purpose of turning waste into treasure.
[0035] Thirdly, the present invention prevents the generation of highly toxic gases by maintaining the pH of the solution at 12 in a first oxidation step, ensures complete oxidation of cyanide, and ensures the safety of the entire process.
[0036] Fourthly, the present invention does not use ammonium salt to dissolve cuprous cyanide, thereby reducing the usage of sodium hypochlorite and lowering the difficulty of disposing cuprous cyanide solids.
[0037] Example 1
[0038] (1) Solid dissolution: Add 100 L of 5% sodium hydroxide solution to a dissolution tank, and slowly add 10 kg of cuprous cyanide powder while stirring to allow it to react and dissolve fully. Approximately 25% of the solid is dissolved to obtain a cuprous cyanide suspension with a solution pH of 12.
[0039] (2) One-stage oxidation: The cuprous cyanide suspension is introduced into the oxidation precipitation reactor, and a theoretical amount of 1.0 times sodium hypochlorite solution is slowly pumped into the cuprous cyanide suspension (the so-called theoretical amount, according to the chemical reaction equation 2CuCN+4NaClO+2H2O=2Cu(OH)2↓+2NaCNO+2NaCl (pH=12), the ratio of the cuprous cyanide content to the amount of sodium hypochlorite added is 1:2, which is the theoretical amount), and the cuprous ions and cyanide ions in the cuprous cyanide suspension are stirred to fully react to obtain the first reaction solution. In order to ensure that the cuprous ions and cyanide ions are oxidized by sodium hypochlorite, the ORP value is simultaneously controlled to be stable at 300mV-350mV. If there is any fluctuation, sodium hypochlorite needs to be added. During the reaction, the cuprous ions are oxidized by sodium hypochlorite under strong alkaline conditions to form black solid sodium percuprate. After the first-order oxidation, the pH of the solution will be reduced to 8.
[0040] (3) Second stage oxidation: Sodium hypochlorite, an oxidizing liquid, is slowly pumped into the first reaction solution to fully oxidize the cyanate ions. The amount of sodium hypochlorite is 1.0 times the theoretical amount. Sodium hypochlorite completely oxidizes the cyanate into carbon dioxide and nitrogen, thereby achieving safe treatment of cuprous cyanide. To ensure that the cyanate ions are oxidized by sodium hypochlorite, the ORP value is simultaneously controlled to be stable at 600mV-650mV. If there is any fluctuation, sodium hypochlorite needs to be added.
[0041] (4) Product treatment: The mixed solution is filtered by filter press to obtain a filter cake, which is soaked in a sodium hydroxide solution for 3 days and then in sodium hypochlorite for 3 days, and then washed with anhydrous ethanol and then with tetrahydrofuran, and dried in a vacuum at 40° C. for 2 hours to obtain a sodium percolate product with strong oxidizing properties.
[0042] Example 2
[0043] The difference between this embodiment and embodiment 1 is that in step (2), the amount of sodium hypochlorite added is 1.5 times the theoretical amount.
[0044] Example 3
[0045] The difference between this embodiment and embodiment 1 is that in step (2), the amount of sodium hypochlorite added is 2.0 times the theoretical amount.
[0046] The comparison of cyanide content of the liquid and solid for treating cuprous cyanide in Examples 1-3 of the present invention is shown in the following table:
[0047]
[0048]
[0049] It can be seen from the above data that when the amount of sodium hypochlorite added is more than 1.5 times the theoretical amount, the cyanide in the solid waste is oxidized, and the cyanide content in the remaining slag drops below the detection limit. It can also be seen that the use of the technical solution of the present invention to treat solid waste containing cuprous cyanide can not only achieve safe disposal of cyanide, but also produce sodium percolate products during the treatment process, realizing resource utilization.
Claims
1. A method for treating solid waste containing cuprous cyanide, comprising the following steps: (1) Solid dissolution: adding solid waste containing cuprous cyanide into a sodium hydroxide solution to obtain a dissolving solution; (2) One-stage oxidation: adjusting the pH of the solution to 11-13, adding an oxidizing agent to the solution, and obtaining a first reaction solution after reaction; (3) Secondary oxidation: adjust the pH of the first reaction solution to 7-9, continue to add an oxidizing agent, and obtain a second reaction solution after reaction; (4) Product treatment: The second reaction liquid is subjected to filter pressure to obtain a filter cake, which is then soaked in a sodium hydroxide solution for 3 days and then in sodium hypochlorite for 3 days, and then washed and dried to obtain a sodium percolate solid.
2. The method for treating cuprous cyanide-containing solid waste according to claim 1, wherein: In the step (1), the mass concentration of the sodium hydroxide solution is 2% to 5%.
3. The method for treating cuprous cyanide-containing solid waste according to claim 1, characterized in that: In the step (2), the pH of the dissolving solution is adjusted to 12, and in the step (3), the pH of the first reaction solution is adjusted to 8.
4. The method for treating cuprous cyanide-containing solid waste according to claim 1, characterized in that: In steps (2) and (3), the oxidizing agent is sodium hypochlorite.
5. The method for treating cuprous cyanide-containing solid waste according to claim 1, characterized in that: In the step (4), the washing and drying are firstly washing with anhydrous ethanol, then washing with tetrahydrofuran, and drying at 40° C. for 8 hours.