A process for treating silver reduction liquid in copper anode mud hydrometallurgy
By conducting COD testing and aeration stripping on the silver reduction liquid, combined with flocculation precipitation and evaporation crystallization, the treatment problem of high-salt and high-COD wastewater was solved, the regeneration and recycling of sodium sulfite and the reuse of condensed water were achieved, and the treatment cost and wastewater discharge were reduced.
Patent Information
- Application Number
- CN202311686552.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-08
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2043-12-08
AI Technical Summary
When treating the silver-reduced liquid in the wet smelting of copper anode mud, the existing technology produces high-salt and high-COD wastewater that cannot be effectively recycled, resulting in high treatment costs and difficulty, and the inability to use biological treatment, which increases the overall difficulty and cost of wastewater treatment.
By testing the COD source of the silver reduction liquid to determine whether it contains volatile substances, aeration and stripping are carried out followed by flocculation and precipitation, evaporation and crystallization are used to separate sodium sulfite, and condensate water is reused to achieve the regeneration and recycling of sodium sulfite and the reuse of condensate water, thereby reducing treatment costs.
The effective components of the silver reduction liquid are recovered, the treatment cost is reduced, the salt solid waste is reduced, the reuse rate of condensed water is increased, the wastewater discharge is reduced, and the difficulty of comprehensive treatment is reduced.
Smart Images
Figure CN117701902B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of copper anode mud hydrometallurgy, and in particular to a treatment process for silver-reduced liquid in copper anode mud hydrometallurgy. Background Art
[0002] During the copper smelting process, the electrolytic production of cathode copper produces a large amount of copper anode slime, which is rich in various precious metals such as gold, silver, platinum, and palladium, as well as rare earth metals such as selenium and tellurium. The hydrometallurgical treatment of copper anode slime generally includes acid leaching for copper separation, chlorination for gold separation, and sodium sulfite for silver separation. In the sodium sulfite for silver separation process, the gold separation residue obtained by chlorination is separated with sodium sulfite to produce a silver separation liquid and silver separation residue. The silver separation liquid is then reduced with the organic reducing agent formaldehyde and separated to produce silver powder and a silver-reduced liquid.
[0003] Currently, for high-salinity, high-COD wastewater such as silver reduction liquid, air / oxygen aeration, Fenton oxidation, and other methods are usually used to convert the remaining sodium sulfite into sodium sulfate, or calcium oxide is added to form an insoluble calcium sulfite precipitate. Although this can reduce the COD value in the water, a large amount of sodium sulfite is lost at the same time. The sodium or calcium salts formed form mixed salts with other impurity salts and cannot be recycled, increasing the salt index in the drainage and increasing the comprehensive treatment difficulty and treatment cost of the wastewater. Moreover, high-salinity and high-toxic wastewater such as silver reduction liquid cannot be treated using relatively low-cost biological methods. Therefore, there is an urgent need for a treatment process for silver reduction liquid that can reduce emissions and reuse. Summary of the Invention
[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a treatment process for the silver reduction liquid in the copper anode mud wet smelting process. After the silver reduction liquid is impurities removed, the effective ingredient sodium sulfite is extracted, and the sodium sulfite is regenerated and recycled, thereby reducing costs and reducing miscellaneous salt solid waste; condensed water is reused to reduce wastewater discharge.
[0005] The object of the present invention is achieved by the following technical measures: a process for treating silver-reduced liquid in copper anode mud hydrometallurgy, wherein the silver-reduced liquid is obtained by subjecting the copper anode mud to acid leaching for copper separation, chlorination for gold separation, and sodium sulfate for silver separation, and the silver-reduced liquid is treated with formaldehyde to remove silver powder. The treatment process comprises the following steps:
[0006] Step 1, COD source detection: Perform COD source detection on the silver reduction liquid to determine whether the main source of COD includes volatile substances. If so, aerate the silver reduction liquid and then proceed to step 2; otherwise, directly proceed to step 2;
[0007] Step 2, weight removal and flocculation: adding a polymeric iron-rich salt solution, a NaOH solution and a PAM flocculant to the silver reduction solution in sequence for flocculation and precipitation, and then filtering;
[0008] Step 3, evaporation crystallization: evaporating and concentrating the filtrate obtained by filtration in step 2;
[0009] Step 4, centrifugal salt collection: the solid-liquid mixture after evaporation and concentration in step 3 is cooled and subjected to solid-liquid separation treatment, the solid obtained after centrifugal separation treatment is returned to the copper anode mud wet smelting process for reuse, the solution obtained after solid-liquid separation treatment is completely evaporated, and the solid obtained after complete evaporation is treated as solid waste;
[0010] Step 5: Reuse of condensed water: Condensate the water vapor evaporated in steps 3 and 4, and return the condensed water to the copper anode mud hydrometallurgy process for reuse.
[0011] Furthermore, the polymeric iron-rich salt solution in step 2 is a polymeric iron-rich salt solution with an iron content of 1.5% by mass, the added amount is 0.1%-0.2% of the mass proportion of the liquid after silver reduction, and the reaction time is 15-30 minutes.
[0012] Furthermore, in step 2, the mass fraction of the NaOH solution is 1%, and the NaOH solution neutralizes the silver-reduced solution to a pH of 7-8.
[0013] Furthermore, in step 2, the PAM flocculant is a PAM aqueous solution with a mass fraction of 0.1%, the added amount is 0.25%-0.5% of the mass proportion of the silver-reduced liquid, and the reaction time is 2-5 minutes.
[0014] Furthermore, in step 3, the filtrate is evaporated and concentrated to 20% of the original volume.
[0015] Furthermore, in step 4, the solid-liquid mixture after evaporation and concentration in step 3 is cooled to 5-10°C.
[0016] Furthermore, the method for detecting volatile substances comprises the following steps:
[0017] Step (1), taking the silver reduction solution to detect and record its COD value;
[0018] Step (2): evaporating the silver-reduced liquid in step (1) to dryness, then adding pure water to the volume of the silver-reduced liquid to obtain a supplemented solution, and detecting the COD value of the supplemented solution. If the reduction in the two COD values is greater than 5%, it is determined that the source of the COD in the silver-reduced liquid includes volatile organic matter; otherwise, it is determined that the source of the COD in the silver-reduced liquid does not include volatile organic matter.
[0019] Furthermore, the COD source detection in step 1 also includes sodium sulfite detection.
[0020] Furthermore, the sodium sulfite detection method comprises the following steps:
[0021] Step 1), taking the silver reduction solution to detect and record its COD value;
[0022] Step 2), adjusting the acidity of the silver reduction solution in step 1) to pH ≤ 2, aerating, and absorbing the tail gas with a NaOH solution;
[0023] Step 3) Using a moistened pH test paper to test the pH value of the tail gas in step 2) until no acidic gas escapes from the tail gas, aeration is stopped, and the aerated solution is obtained. The COD value of the aerated solution is tested. If the reduction in both COD values is greater than 80%, it is considered that the silver-reduced solution is feasible for recovering sodium sulfite salt.
[0024] Furthermore, in the step 1, air is used as an aeration source for aeration stripping, the aeration time is more than 30 minutes, and the aeration tail gas is absorbed by an absorption tower connected in series with activated carbon and VOC resin.
[0025] Compared with the prior art, the present invention has the following advantages: It proposes a method for treating silver reduction liquor separately, eliminating the need to mix it with other wastewater from the copper anode slime smelting process for comprehensive treatment. This reduces cross-effects on the water quality of other wastewaters, reduces system expansion, and reduces the difficulty and cost of comprehensive treatment. Furthermore, the present invention removes impurities from the silver reduction liquor and extracts the active ingredient, sodium sulfite, which is then recycled and reused, reducing costs and reducing solid salt waste. Condensate is reused, with a reuse rate exceeding 90%, thereby reducing wastewater discharge.
[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a process flow chart of the present invention.
[0028] Figure 2 This is the process flow chart for COD source detection. DETAILED DESCRIPTION
[0029] like Figures 1 to 2 As shown, a process for treating silver reduction liquid from copper anode mud hydrometallurgy is described. The silver reduction liquid is obtained by subjecting the copper anode mud to acid leaching for copper separation, chlorination for gold separation, and sodium sulfate for silver separation, followed by reduction to remove silver powder. The silver reduction liquid primarily comprises sodium sulfite, and may also contain an organic reducing agent and trace metal ions. The content of the organic reducing agent is related to the amount of organic reducing agent added during the reduction of the silver reduction liquid. The COD content of the silver reduction liquid primarily comes from the sodium sulfite, the organic reducing agent, and its derivatives. The treatment process comprises the following steps:
[0030] Step 1, COD Source Detection: The silver reduction liquid is tested for COD sources to determine whether the primary source of COD includes volatile substances, such as formaldehyde. If so, the silver reduction liquid is aerated and then proceeds to Step 2. Otherwise, the process proceeds directly to Step 2. Aeration and stripping uses air as the aeration source for at least 30 minutes. The aeration exhaust is absorbed in an activated carbon and VOC resin absorption tower connected in series. Aeration and stripping removes volatile substances from the silver reduction liquid, preventing them from affecting subsequent treatment processes.
[0031] Step 2, weight removal and flocculation: a polymeric iron-rich salt solution with an iron content of 1.5% by mass and an amount of 0.1-0.2% by mass of the silver reduced liquid is added to the silver reduced liquid, and the reaction is carried out for 15-30 minutes. The silver reduced liquid is then neutralized with a 1% by mass NaOH solution to a pH of 7-8. Finally, a PAM aqueous solution with an amount of 0.25-0.5% by mass of the silver reduced liquid and a mass fraction of 0.1% is added, and the reaction is carried out for 2-5 minutes. The solution is filtered to remove trace metal ions in the silver reduced liquid by precipitation.
[0032] Step 3, evaporation crystallization: the filtrate obtained by filtration in step 2 is sent to a triple-effect evaporation system for evaporation and concentration, and the evaporation concentration is 20% of the original volume to precipitate solid salt, and the concentrate and solid salt are discharged from the triple-effect evaporation system.
[0033] Step 4, centrifugal salt collection: the solid-liquid mixture after evaporation and concentration in step 3 is cooled to about 5-10°C and centrifuged. The solid salt obtained after solid-liquid separation is sodium sulfite, which is returned to the copper anode mud wet smelting process for reuse. The liquid obtained after solid-liquid separation is transferred to a rake dryer for complete evaporation. The solid obtained after complete evaporation is miscellaneous salt solid waste, which is treated as solid waste.
[0034] Step 5: Reuse of condensed water: The water vapor evaporated in steps 3 and 4 is condensed through a condenser, and the condensed water is returned to the copper anode mud wet smelting process for reuse.
[0035] This application proposes a process for treating silver reduction liquor from copper anode slime hydrometallurgy. Prior to treatment, the silver reduction liquor is first tested for COD sources to determine whether it contains unreacted volatile organic reducing agents. If so, the silver reduction liquor is first subjected to aeration and stripping to remove the volatile organic reducing agents from the silver reduction liquor, preventing them from interfering with the subsequent evaporation and extraction of sodium sulfite and condensed water. A flocculant is then used to remove metal ions from the silver reduction liquor as a precipitate. Finally, sodium sulfite is evaporated and condensed water is obtained. This application proposes a method for treating the silver reduction liquor separately, eliminating the need to mix it with other wastewater from the copper anode slime smelting process for comprehensive treatment. This reduces cross-effects on the water quality of other wastewaters, minimizes system expansion, and reduces the difficulty and cost of comprehensive treatment. Furthermore, after impurities are removed from the silver reduction liquor, the active ingredient, sodium sulfite, is extracted and recycled, reducing costs and reducing solid salt waste. The condensed water is reused, with a reuse rate exceeding 90%, thereby reducing wastewater discharge.
[0036] The method for detecting volatile substances comprises the following steps:
[0037] Step (1), taking the silver reduction solution to detect and record its COD value;
[0038] Step (2): Evaporate the silver reduction solution in step (1) to dryness, then add pure water to the volume of the silver reduction solution to obtain a supplemented solution, and detect the COD value of the supplemented solution. If the reduction in the two COD values is greater than 5%, it is determined that the source of COD in the silver reduction solution includes volatile substances. Otherwise, it is determined that the source of COD in the silver reduction solution does not include volatile substances. Among them, the most volatile substances are derived from the volatile organic reducing agent formaldehyde reagent. Therefore, due to reasons such as the amount added, some formaldehyde may remain and not participate in the reaction. Therefore, by detecting the COD values before and after evaporation, if the difference between the COD values before and after is greater than 5%, it indicates that some unreacted organic reducing agent, such as formaldehyde, exists in the silver reduction solution. If the difference between the COD values before and after evaporation is not greater than 5%, it indicates that the organic matter in the silver reduction solution mainly exists in the form of organic salts, that is, all the formaldehyde has reacted to form organic salt derivatives such as sodium formate and sodium sulfonate, which are not easy to volatilize.
[0039] The COD source detection in step 1 also includes a sodium sulfite detection. The sodium sulfite detection can be used to determine whether the silver-reduced liquid is recyclable. If it is recyclable, the silver-reduced liquid treatment process of the present application can be used to recover the sodium sulfite. Otherwise, the silver-reduced liquid can be treated using conventional wastewater treatment methods.
[0040] The sodium sulfite detection method comprises the following steps:
[0041] Step 1), taking the silver reduction solution to detect and record its COD value;
[0042] Step 2), adjusting the acidity of the silver reduction solution in step 1) to pH ≤ 2, aerating, and absorbing the tail gas with a NaOH solution;
[0043] In step 3), the pH value of the tail gas from step 2) is tested with moistened pH test paper until no acidic gas escapes from the tail gas. Aeration is then stopped to obtain an aerated solution. The COD value of the aerated solution is then tested. If both COD values decrease by more than 80%, the silver-reduced liquid is considered feasible for sodium sulfite recovery. After acidification of the silver-reduced liquid, the sodium sulfite therein produces sulfur dioxide gas. The difference in COD values before and after acidification is primarily due to the consumption of the sodium sulfite. Therefore, a greater than 80% decrease in COD values indicates that more than 80% of the COD in the silver-reduced liquid wastewater is derived from sulfite, indicating that sodium sulfite recovery is feasible.
[0044] Example 1
[0045] A batch of silver reduction wastewater from the copper anode mud hydrometallurgy process was selected, and its main components were tested as follows:
[0046] Silver reduction solution: sodium sulfite (196.9 g / L), organic reducing agent formaldehyde and its derivatives (1.8 g / L), silver (89 mg / L), copper (150 mg / L), bismuth (<1 mg / L), lead (50 mg / L), antimony (20 mg / L), arsenic (6 mg / L), pH = 8.
[0047] The silver reduction solution is treated in the following steps:
[0048] Step 1, COD source detection: The COD source detection is performed on the silver reduction liquid. The specific detection steps are as follows:
[0049] 1. Analyze the volatile organic reducing agent components of the silver reduction solution. The specific operations are as follows:
[0050] Step (1), taking 200mL of the silver reduction solution, and detecting its COD value to be 29300mg / L.
[0051] In step (2), 200 mL of the silver-reduced liquid was evaporated to dryness. Water was then added to the silver-reduced liquid after the salt precipitation until the volume of the silver-reduced liquid was restored to 200 mL, and the COD value was measured to be 28900 mg / L. The reduction in COD before and after was only 1%, and the difference was less than 5%, indicating that the components in the silver-reduced liquid were all non-volatile substances, that is, the organic reducing agent formaldehyde had all been converted into organic sodium salt solids, and the organic reducing agent formaldehyde and its derivatives were basically present in the form of non-volatile formaldehyde derivatives. Evaporation and aeration had no significant effect on reducing COD.
[0052] 2. Analysis of sodium sulfite composition in the solution after silver reduction. The specific operation is as follows:
[0053] Step 1) Take 200 mL of the silver-reduced solution and detect its COD value, which is 29300 mg / L.
[0054] Step 2) Slowly add sulfuric acid to 200 mL of the silver reduction solution to adjust the acid to pH ≤ 2, aerate with air for 5 minutes, and absorb the derived tail gas sulfur dioxide with a mass fraction of 1% NaOH alkaline solution.
[0055] In step 3, the aeration was repeated in small amounts until the acid was slightly excessive and the pH of the system no longer increased due to aeration. The exhaust gas was tested with moistened pH test paper to confirm no significant acidic gas emission. The aerated solution was obtained and the COD value of the aerated solution was 2800 mg / L. The COD reduction reached 90%, indicating that sodium sulfite is the primary source of COD in the silver reduction wastewater and is therefore recyclable.
[0056] Step 2, weight removal and flocculation: Take 200 mL of the silver reduction solution, add 0.2 mL of a 1.5% iron-containing polymeric iron-rich salt solution under stirring, stir for 20 minutes, and then add a small amount of 1% by mass NaOH solution dropwise for neutralization to a pH of about 7-8.
[0057] Add 1 drop of 0.1% PAM for flocculation while stirring, continue stirring for 2 minutes to fully precipitate the heavy metals and precious metals, filter the solution, and the heavy metal content and silver ion content in the filtrate are measured to be less than 5 mg / L. The filter residue contains precious metal silver and can be returned to the pyrometallurgical system to re-enrich silver.
[0058] Step 3: Evaporation and crystallization: The filtrate was evaporated and concentrated until the volume was 40 mL, and a large amount of white crystalline solid was visible.
[0059] Step 4: Centrifugal Salt Collection: The solid-liquid mixture is cooled to approximately 5-10°C and centrifuged. The solution is then discharged, and the resulting white solid is a relatively pure sodium sulfite salt containing water of crystallization. The water of crystallization is evaporated, and the purity of the obtained sodium sulfite is tested to be over 90%, which can be returned to the process for use. The discharged solution is a highly concentrated mixed salt solution containing sodium sulfite, sodium chloride, and organic sodium salts. This solution is evaporated to dryness to obtain a reduced amount of mixed salts, which are then treated as solid waste.
[0060] Step 5: Condensate reuse: The water vapor evaporated in steps 3 and 4 is condensed and recovered through a condensation device. The recovery rate can reach more than 90%. The collected condensed water can be returned to the process for use.
[0061] Example 2
[0062] A batch of silver reduction wastewater from the copper anode mud hydrometallurgy process was selected, and its main components were tested as follows:
[0063] Silver reduction solution: sodium sulfite (223.8 g / L), organic reducing agent formaldehyde and its derivatives (6.7 g / L), silver (108 mg / L), copper (110 mg / L), bismuth (<1 mg / L), lead (37 mg / L), antimony (43 mg / L), arsenic (8 mg / L), pH = 8.
[0064] The silver reduction solution is treated in the following steps:
[0065] Step 1, COD source detection: The COD source detection is performed on the silver reduction liquid. The specific detection steps are as follows:
[0066] 1. Analyze the volatile organic reducing agent components of the silver reduction solution. The specific operations are as follows:
[0067] Step (1), taking 200mL of the silver-reduced liquid, and detecting its COD value to be 33500mg / L.
[0068] In step (2), 200 mL of the silver-reduced liquid was evaporated to dryness. Water was then added to the silver-reduced liquid after the salt precipitation until the volume of the silver-reduced liquid was restored to 200 mL. The COD value was measured and found to be 29,700 mg / L. The COD reduction before and after the step was 11.3%, a difference exceeding 5%. The organic reducing agent formaldehyde and its derivatives in the silver-reduced liquid included volatile formaldehyde.
[0069] 2. Analysis of sodium sulfite composition in the solution after silver reduction. The specific operation is as follows:
[0070] Step 1) Take 200 mL of the silver-reduced solution and detect its COD value, which is 33500 mg / L.
[0071] Step 2) Slowly add sulfuric acid to 200 mL of the silver reduction solution to adjust the acid to pH ≤ 2, aerate with air for 5 minutes, and absorb the derived tail gas sulfur dioxide with a mass fraction of 1% NaOH alkaline solution.
[0072] In step 3, the aeration was repeated in small amounts until the acid was slightly excessive and the pH of the system no longer increased due to aeration. The exhaust gas, tested with moistened pH test paper, showed no significant acidic gas emission. The aerated solution was obtained and the COD value of the aerated solution was 5790 mg / L. The COD reduction reached 82.7%, indicating that sodium sulfite is the primary source of COD in the silver reduction wastewater and is therefore recyclable.
[0073] The silver reduction liquid was subjected to aeration stripping treatment: 200 mL of the silver reduction liquid was taken and air stripped for 30 minutes. The tail gas was adsorbed by activated carbon, and the COD was measured to be reduced to 28750 mg / L. It can be seen that aeration stripping did not cause much oxidation of sodium sulfite, and the main cause was the further oxidation of formaldehyde derivatives. The next step of sodium sulfite recovery can be carried out.
[0074] Step 2, deweighting and flocculation: add 0.2 mL of a 1.5% iron-containing polymeric iron-rich salt solution to the silver reduction solution after aeration stripping under stirring, stir for 20 minutes, and then add a small amount of 1% by mass NaOH solution dropwise for neutralization to a pH of about 7-8.
[0075] Add 1 drop of 0.1% PAM for flocculation while stirring, continue stirring for 2 minutes to fully precipitate the heavy metals and precious metals, filter the solution, and the heavy metal content and silver ion content in the filtrate are measured to be less than 5 mg / L. The filter residue contains precious metal silver and can be returned to the pyrometallurgical system to re-enrich silver.
[0076] Step 3: Evaporation and crystallization: The filtrate was evaporated and concentrated until the volume was 40 mL, and a large amount of white crystalline solid was visible.
[0077] Step 4: Centrifugal Salt Collection: The solid-liquid mixture is cooled to approximately 5-10°C and centrifuged. The solution is then discharged, and the resulting white solid is a relatively pure sodium sulfite salt containing water of crystallization. The water of crystallization is evaporated, and the purity of the obtained sodium sulfite is tested to be over 90%, which can be returned to the process for use. The discharged solution is a highly concentrated mixed salt solution containing sodium sulfite, sodium chloride, and organic sodium salts. This solution is evaporated to dryness to obtain a reduced amount of mixed salts, which are then treated as solid waste.
[0078] Step 5: Condensate reuse: The water vapor evaporated in steps 3 and 4 is condensed and recovered through a condensation device. The recovery rate can reach more than 90%. The collected condensed water can be returned to the process for use.
[0079] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A process for treating the reduced silver solution in copper anode mud hydrometallurgy, characterized in that: The silver reduction liquid is a silver reduction liquid obtained by subjecting copper anode mud to acid leaching for copper separation, chlorination for gold separation, and sodium sulfate for silver separation, and the silver reduction liquid is a silver reduction liquid obtained by subjecting the silver reduction liquid to formaldehyde reduction to remove silver powder. The treatment process comprises the following steps: Step 1, COD source detection: Perform COD source detection on the silver reduction liquid to determine whether the main source of COD includes volatile substances. If so, aerate the silver reduction liquid and then proceed to step 2; otherwise, directly proceed to step 2; Step 2, weight removal and flocculation: adding a polymeric iron-rich salt solution, a NaOH solution and a PAM flocculant to the silver reduction solution in sequence for flocculation and precipitation, and then filtering; Step 3, evaporation crystallization: evaporating and concentrating the filtrate obtained by filtration in step 2; Step 4, centrifugal salt collection: the solid-liquid mixture after evaporation and concentration in step 3 is cooled and subjected to solid-liquid separation treatment, the solid obtained after centrifugal separation treatment is returned to the copper anode mud wet smelting process for reuse, the solution obtained after solid-liquid separation treatment is completely evaporated, and the solid obtained after complete evaporation is treated as solid waste; Step 5, condensed water reuse: condense the water vapor evaporated in step 3 and step 4, and return the condensed water to the copper anode mud hydrometallurgy process for reuse; The method for detecting volatile substances comprises the following steps: Step (1), taking the silver reduction solution to detect and record its COD value; Step (2): evaporating the silver-reduced liquid in step (1) to dryness, then adding pure water to the volume of the silver-reduced liquid to obtain a supplemented solution, and detecting the COD value of the supplemented solution. If the reduction in the two COD values is greater than 5%, it is determined that the source of the COD in the silver-reduced liquid includes volatile organic matter; otherwise, it is determined that the source of the COD in the silver-reduced liquid does not include volatile organic matter.
2. The process for treating the reduced silver solution in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: In step 2, the polymeric iron-rich salt solution is a polymeric iron-rich salt solution with an iron content of 1.5% by mass, the added amount is 0.1%-0.2% of the mass of the liquid after silver reduction, and the reaction time is 15-30 minutes.
3. The process for treating the reduced silver solution in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: The mass fraction of the NaOH solution in step 2 is 1%, and the NaOH solution neutralizes the silver-reduced solution to a pH of 7-8.
4. The process for treating the reduced silver solution in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: In step 2, the PAM flocculant is a PAM aqueous solution with a mass fraction of 0.1%, the added amount is 0.25%-0.5% of the mass proportion of the silver-reduced liquid, and the reaction time is 2-5 minutes.
5. The process for treating the reduced silver liquid in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: In step 3, the filtrate is evaporated and concentrated to 20% of the original volume.
6. The process for treating the reduced silver solution in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: In step 4, the solid-liquid mixture after evaporation and concentration in step 3 is cooled to 5-10°C.
7. The process for treating the reduced silver solution in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: The COD source detection in step 1 also includes sodium sulfite detection.
8. The process for treating the reduced silver liquid in the copper anode mud hydrometallurgy according to claim 7, characterized in that: The sodium sulfite detection method comprises the following steps: Step 1), take the silver reduction solution to test and record its COD value; Step 2), adjusting the acidity of the silver reduction solution in step 1) to pH ≤ 2, aerating, and absorbing the tail gas with NaOH solution; In step 3), the pH value of the tail gas in step 2) is tested with a moistened pH test paper until no acidic gas escapes from the tail gas. Aeration is then stopped to obtain an aerated solution. The COD value of the aerated solution is tested. If the reduction in both COD values is greater than 80%, the silver-reduced solution is considered feasible for recovering sodium sulfite salt.
9. The process for treating the reduced silver liquid in the hydrometallurgy of copper anode mud according to claim 1, characterized in that: In step 1, air is used as the aeration source for aeration stripping, the aeration time is more than 30 minutes, and the aeration tail gas is absorbed by an activated carbon and VOC resin series absorption tower.