A method for purifying cyanide lean solution

Abstract

The present invention discloses a method for purifying cyanide lean solution. For the cuprocyanide complex in the cyanide lean solution, firstly, a prepared cuprous solution is used to precipitate cyanide and thiocyanate, then a sulfide reagent is used to precipitate the remaining copper ions, and finally, an activated carbon catalytic oxidation method is used to adsorb and recover the residual metal ions and catalytically oxidize the residual cyanide. The present invention can not only recover various valuable substances in the wastewater to the greatest extent, but also achieve deep purification treatment of heavy metals and cyanide. The treatment process is simple, with low investment and operating costs, and has strong application value and prospects in cyanide process enterprises.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant treatment in the environmental protection field, and specifically relates to a method for purifying and treating cyanide lean solution. Background Art

[0002] In the gold industry, as the mining grade of gold ore decreases day by day, refractory polymetallic ore sources have gradually become the main objects of future development. A typical one is copper-bearing gold ore. During the mining process, in addition to the flotation process, the gold ore needs to be cyanide leached, resulting in cyanide lean solution containing copper cyanide complexes. When recycled for production, due to the presence of pollutants such as cyanide, copper, iron, and thiocyanate, it will have varying degrees of adverse effects on both the flotation process and the cyanidation process, and emissions will cause serious damage to the environment. Therefore, it is necessary to carry out targeted purification treatment on the cyanide lean solution to meet the requirements of reuse or discharge up to standard.

[0003] Currently, the commonly used treatment methods for cyanide lean solution include cyanide destruction treatment methods and recovery treatment methods. Cyanide destruction treatment methods include alkaline chlorine method, Inco method, hydrogen peroxide oxidation method, ozone oxidation method, etc., which oxidize and decompose cyanide, break copper cyanide complexes and then recover copper. However, this method consumes a large amount of reagents, and cyanide and thiocyanate are not recovered, affecting the economic benefits of treatment. Recovery treatment methods include acidification precipitation method, AVR method (acidification - volatilization - neutralization) and SART method (sulfidation - acidification - return - thickening). The first two methods require adjusting the solution to strong acid, which has very high requirements for equipment, process operation and personnel operation, and there are potential safety risks. The SART method can precipitate and recover copper by adding sodium sulfide or sodium hydrosulfide, but it also needs to adjust the pH of the lean solution to weak acid and continuous control is required, and the sulfide reagent is volatile, which has high requirements for the operating environment.

[0004] Therefore, how to develop a method for purifying and treating cyanide lean solution to effectively recover copper, gold, cyanide and thiocyanate in the lean solution, and the recycled lean solution after treatment does not cause adverse effects on the production process or meets the wastewater discharge standard is the key to the purification and treatment of cyanide lean solution. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention aims to provide a method for purifying and treating cyanide lean solution.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for purifying and treating cyanide lean solution, comprising the following steps:

[0008] S1. Preparation of cuprous solution: Add copper sulfate to sodium metabisulfite solution to obtain cuprous solution;

[0009] S2. Complexation precipitation: Add cuprous solution to the lean cyanide solution. After complete stirring reaction, cuprous cyanide and cuprous thiocyanate are formed. Then add polyaluminum chloride and polyacrylamide, and then flow into the complexation precipitation tank for precipitation. The overflow liquid of the complexation precipitation tank is transferred to step S3 for treatment, and the sediment in the complexation precipitation tank is transferred to step S5 for treatment;

[0010] S3. Sulfide precipitation: Adjust the pH value of the overflow liquid of the complexation precipitation tank to 4 - 5, then add sulfide reagent. After complete reaction, cuprous sulfide is formed. Add polyacrylamide, and then flow into the sulfide precipitation tank for precipitation;

[0011] S4. Activated carbon catalytic oxidation: The overflow liquid of the sulfide precipitation tank enters the activated carbon catalytic oxidation system. Air is introduced into the activated carbon catalytic oxidation system to adsorb and catalytically oxidize the residual heavy metals, cyanides, and thiocyanates in the overflow liquid of the sulfide precipitation tank. The treated liquid is returned to the ore dressing production system or discharged up to standard;

[0012] S5. Sediment conversion: Place the sediment in the complexation precipitation tank in an ammonia water solution and stir to dissolve it. Adjust the pH value to 4 - 5 with sulfuric acid, then add sulfide reagent. After complete reaction, cuprous sulfide is formed. Add polyacrylamide, and then flow into the conversion precipitation tank for precipitation;

[0013] S6. Acidification and stripping: The overflow liquid of the conversion precipitation tank enters the acidification and stripping tank. Adjust the pH to 2 - 3 with sulfuric acid, add hydrogen peroxide, and then introduce air for stripping. The stripping gas enters the alkali liquid absorption tank and is absorbed with sodium hydroxide solution. After stripping, the liquid is adjusted to pH 7 - 8 with lime milk for neutralization and flows into the neutralization precipitation tank for precipitation;

[0014] S7. Ammonia water regeneration: Adjust the pH value of the overflow liquid of the neutralization precipitation tank to 10 - 11 with sodium hydroxide and return it to step S5 for sediment conversion.

[0015] Furthermore, in step S1, in a sodium metabisulfite solution with a mass concentration of 15 - 30%, copper sulfate is added at a mass ratio of 1.5 - 2.5:1 to prepare the cuprous solution.

[0016] Furthermore, in step S2, the cuprous solution is added to the lean cyanide solution according to the molar ratio of the sum of cyanide and thiocyanate in the lean cyanide solution to copper ions of 1:2 - 2.5. After stirring and reacting for 30 - 60 min, cuprous cyanide and cuprous thiocyanate are formed; the added polyaluminum chloride and polyacrylamide respectively account for 0.2 - 0.5% and 0.01 - 0.2% of the total mass of the current liquid.

[0017] Further, in step S3, a sulfide reagent is added to the overflow liquid in the complexation precipitation tank at a molar ratio of sulfide ions to the remaining copper ions in the overflow liquid of 2 - 2.5:1. After reacting for 15 - 30 minutes, cuprous sulfide is formed; the added polyacrylamide accounts for 0.01 - 0.1% of the total mass of the current liquid.

[0018] Further, in step S5, the mass concentration of the ammonia water solution is 10 - 20%; a sulfide reagent is added to the sediment in the complexation precipitation tank at a molar ratio of sulfide ions to copper ions of 2 - 2.5:1. After reacting for 15 - 30 minutes, cuprous sulfide is formed, and polyacrylamide is added at 0.05 - 0.2% of the total mass of the current liquid.

[0019] Further, in step S6, hydrogen peroxide is added to the overflow liquid in the conversion precipitation tank after adjusting the pH at a molar ratio of H2O2 to thiocyanate of 3 - 4:1. The stripping gas enters the alkali liquid absorption tank and is absorbed by a sodium hydroxide solution with a mass percentage of 10 - 25%.

[0020] Further, the cuprous sulfide sediment produced in steps S3 and S5 is transported to a filter press for pressure filtration and then sold externally, and the neutralization slag produced in step S6 is discharged into the tailings pond.

[0021] Further, the sulfide reagent in steps S3 and S5 is any one or two of sodium sulfide and sodium bisulfide, and the mass concentration is 10 - 25%.

[0022] Further, in step S4, the activated carbon catalytic oxidation system includes 1 - 3 stages of serially connected activated carbon catalytic oxidation tanks. Each stage of the activated carbon catalytic oxidation tank is provided with a cylindrical activated carbon adsorption column, and a microporous aeration disk for introducing air is arranged at the inner bottom of each stage of the activated carbon catalytic oxidation tank; the empty bed residence time of the overflow liquid in the sulfide precipitation tank in the activated carbon catalytic oxidation tank is 10 - 30 minutes, and the gas - liquid volume ratio with the introduced air is 10 - 30:1.

[0023] Further, in step S6, the stripping gas - liquid volume ratio is 100 - 200:1, the stripping time is 30 - 60 minutes, and the absorbed liquid after absorption is returned to the cyanidation leaching production system.

[0024] The beneficial effects of the present invention are as follows: For the copper - cyanide complex in the cyanidation lean liquid, the present invention first uses the prepared cuprous solution to precipitate cyanide and thiocyanate, then uses a sulfide reagent to precipitate the remaining copper ions, and finally uses the activated carbon catalytic oxidation method to adsorb and recover the residual metal ions and catalytically oxidize the residual cyanide. The present invention can not only recover various valuable substances in the wastewater to the maximum extent, but also achieve the deep purification treatment of heavy metals and cyanide. The treatment process is simple, the investment and operation costs are low, and it has strong application value and prospects in cyanidation process enterprises. Description of the Drawings

[0025] Figure 1 It is the process flow diagram of the purification treatment of cyanide lean solution in each embodiment of the present invention;

[0026] Figure 2 It is the process flow diagram of the conversion of cuprous (sulfide) cyanide slag to cuprous sulfide slag in each embodiment of the present invention. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with the drawings. It should be noted that this embodiment is based on the present technical solution and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0028] Embodiment 1

[0029] A certain gold mining enterprise uses the sulfur concentrate after copper-sulfur separation flotation for cyanide leaching. The composition of the cyanide lean solution produced is shown in Table 1. The main pollutant components are copper, cyanide, and thiocyanate, and it also contains valuable metal elements such as gold and silver.

[0030] Table 1

[0031]

[0032] Note: CN T is total cyanide, CN - is free cyanide, and pH is dimensionless.

[0033] The method for purifying and treating cyanide lean solution adopted in this embodiment is as shown in Figure 1 and Figure 2 and includes the following steps:

[0034] (1) Prepare a sodium metabisulfite solution with a mass concentration of 20%, and then add copper sulfate according to a mass ratio of 2:1 to prepare a cuprous solution;

[0035] (2) In the stirring tank, add the cuprous solution according to a molar ratio of 2.2:1 of copper ions to the sum of cyanide ions and thiocyanate ions in the cyanide lean solution. After stirring and reacting for 60 minutes, add polyaluminum chloride and polyacrylamide according to 0.5% and 0.1% of the current total liquid mass respectively, and flow into the complex precipitation tank for precipitation;

[0036] (3) Adjust the pH value of the overflow liquid in the complex precipitation tank to 5, add sodium sulfide according to a molar ratio of 2:1 of sulfide ions to the remaining copper ions, react for 20 minutes, and add polyacrylamide according to 0.05% of the current total liquid mass and enter the sulfide precipitation tank for precipitation;

[0037] (4) The overflow liquid of the sulfide precipitation tank enters the activated carbon catalytic oxidation reactor, and air is introduced for adsorption and catalytic oxidation. The filtration rate is 5 m / h, the empty bed residence time is 30 min, and the gas-liquid ratio is 20:1. The treated liquid is pumped into the return water tank for use in the return production system. The analysis of pollutant components in the liquid is shown in Table 2.

[0038] Table 2

[0039]

[0040] Note: CN T is total cyanide, CN - is free cyanide, pH is dimensionless.

[0041] (5) The sediment in the complex precipitation tank is placed in an ammonia water solution with a mass concentration of 10% and stirred to dissolve. The pH value is adjusted to 5 with sulfuric acid. Sodium sulfide is added according to the molar ratio of sulfur ion to copper ion of 2:1 and reacted for 20 min. Polyacrylamide is added at 0.1% of the total mass of the current liquid and enters the conversion precipitation tank for precipitation;

[0042] (6) The overflow liquid of the conversion precipitation tank enters the acidification stripping tank. The pH is adjusted to 2 with sulfuric acid. Hydrogen peroxide with a mass concentration of 37% is added according to the molar ratio of H2O2 to thiocyanate of 3:1. Air is introduced for stripping according to the gas-liquid ratio of 100:1. The stripped gas is absorbed with a sodium hydroxide solution with a mass concentration of 20%. The liquid after stripping is adjusted to pH 7 with lime milk with a mass concentration of 20% for neutralization and flows into the neutralization precipitation tank for precipitation. The neutralization slag is discharged into the tailings pond; the overflow liquid of the neutralization precipitation tank is adjusted to pH 10 with sodium hydroxide and returned for sediment conversion. The sediment slag produced by sulfide precipitation is analyzed for the components of gold and copper. The gold content is 89.59 g / t and the copper content is 65.38%.

[0043] Example 2

[0044] The cyanide lean solution used in this example is the same as that in Example 1, and the purification treatment method of the cyanide lean solution used is as Figure 1 and Figure 2 shown, including the following steps:

[0045] (1) Prepare a sodium metabisulfite solution with a mass concentration of 15%, and then add copper sulfate according to the mass ratio of 2.5:1 to prepare a cuprous solution;

[0046] (2) In the stirring tank, add the cuprous solution according to the molar ratio of copper ion to the sum of cyanide and thiocyanate in the cyanide lean solution of 2.5:1. After stirring and reacting for 60 min, add polyaluminum chloride and polyacrylamide at 0.2% and 0.2% of the total mass of the current liquid respectively, and flow into the complex precipitation tank for precipitation;

[0047] (3) Adjust the pH value of the overflow liquid of the complex precipitation tank to 5, add sodium sulfide according to the molar ratio of sulfide ion to residual copper ion of 2.5:1. After reacting for 20 min, add polyacrylamide according to 0.01% of the total current liquid mass and enter the sulfide precipitation tank for precipitation;

[0048] (4) The overflow liquid of the sulfide precipitation tank enters the activated carbon catalytic oxidation reactor, and air is introduced for adsorption and catalytic oxidation. The filtration rate is 5 m / h, the empty bed residence time is 30 min, and the gas-liquid ratio is 30:1. The treated liquid is pumped into the return water tank for use in the return production system. The analysis of pollutant components in the liquid is shown in Table 3.

[0049] Table 3

[0050]

[0051] Note: CN T is total cyanide, CN - is free cyanide, and pH is dimensionless.

[0052] (5) Place the sediment in the complex precipitation tank into an ammonia water solution with a mass concentration of 20% and stir to dissolve it. Adjust the pH value to 5 with sulfuric acid, add sodium sulfide according to the molar ratio of sulfide ion to copper ion of 2.5:1 and react for 20 min. Add polyacrylamide according to 0.05% of the total current liquid mass and enter the conversion precipitation tank for precipitation;

[0053] (6) The overflow liquid of the conversion precipitation tank enters the acidification stripping tank. Adjust the pH to 2 with sulfuric acid, add hydrogen peroxide with a mass concentration of 37% according to the molar ratio of H2O2 to thiocyanate radical of 4:1, introduce air for stripping according to the gas-liquid volume ratio of 200:1. The stripped gas is absorbed by a sodium hydroxide solution with a mass concentration of 25%. After stripping, the liquid is adjusted to pH 7 with lime milk with a mass concentration of 20% for neutralization and flows into the neutralization precipitation tank for precipitation. The neutralization slag is discharged into the tailings pond; the overflow liquid of the neutralization precipitation tank is adjusted to pH 10 with sodium hydroxide and returned for sediment conversion. Conduct component analysis of gold and copper on the precipitation slag produced by sulfide precipitation. The gold content is 87.59 g / t and the copper content is 64.42%.

[0054] For those skilled in the art, various corresponding changes and deformations can be given according to the above technical solutions and concepts, and all these changes and deformations should be included in the protection scope of the claims of the present invention.

Claims

1. A method for purifying cyanide lean solution, characterized in that, It includes the following steps: S1. Preparation of cuprous solution: Cupric sulfate is added to sodium metabisulfite solution to obtain cuprous solution; S2. Complexation precipitation: Cuprous solution is added to lean cyanide solution. After stirring and complete reaction, cuprous cyanide and cuprous thiocyanate are formed. Poly aluminum chloride and polyacrylamide are added, and then it flows into the complexation precipitation tank for precipitation. The overflow liquid of the complexation precipitation tank is transferred to step S3 for treatment, and the sediment in the complexation precipitation tank is transferred to step S5 for treatment; S3. Sulfide precipitation: The pH value of the overflow liquid of the complexation precipitation tank is adjusted to 4 - 5, and then sulfide reagent is added. After complete reaction, cuprous sulfide is formed. Polyacrylamide is added, and then it flows into the sulfide precipitation tank for precipitation; S4. Activated carbon catalytic oxidation: The overflow liquid of the sulfide precipitation tank enters the activated carbon catalytic oxidation system. Air is introduced into the activated carbon catalytic oxidation system to adsorb and catalytically oxidize the remaining heavy metals, cyanides and thiocyanates in the overflow liquid of the sulfide precipitation tank. The treated liquid is returned to the ore dressing production system or discharged up to standard; S5. Sediment conversion: The sediment in the complexation precipitation tank is placed in ammonia water solution and stirred to dissolve. The pH value is adjusted to 4 - 5 with sulfuric acid, and then sulfide reagent is added. After complete reaction, cuprous sulfide is formed. Polyacrylamide is added, and then it flows into the conversion precipitation tank for precipitation; S6. Acidification and stripping: The overflow liquid of the conversion precipitation tank enters the acidification and stripping tank. The pH is adjusted to 2 - 3 with sulfuric acid, hydrogen peroxide is added, and then air is introduced for stripping. The stripping gas enters the alkali liquor absorption tank and is absorbed with sodium hydroxide solution. After stripping, the liquid is adjusted to pH 7 - 8 with lime milk for neutralization and flows into the neutralization precipitation tank for precipitation; S7. Ammonia water regeneration: The pH value of the overflow liquid of the neutralization precipitation tank is adjusted to 10 - 11 with sodium hydroxide and returned to step S5 for sediment conversion.

2. The method according to claim 1, characterized in that In step S1, cupric sulfate is added to sodium metabisulfite solution with a mass concentration of 15 - 30% according to the mass ratio of 1.5 - 2.5:1 to obtain cuprous solution.

3. The method according to claim 1, wherein In step S2, cuprous solution is added to lean cyanide solution according to the molar ratio of the sum of cyanide and thiocyanate in the lean cyanide solution to cuprous ion of 1:2 - 2.

5. After stirring and reacting for 30 - 60 min, cuprous cyanide and cuprous thiocyanate are formed; the added poly aluminum chloride and polyacrylamide respectively account for 0.2 - 0.5% and 0.01 - 0.2% of the total mass of the current liquid.

4. The method according to claim 1, wherein In step S3, sulfide reagent is added to the overflow liquid of the complexation precipitation tank according to the molar ratio of sulfide ion to the remaining cuprous ion in the overflow liquid of the complexation precipitation tank of 2 - 2.5:

1. After reacting for 15 - 30 min, cuprous sulfide is formed; the added polyacrylamide accounts for 0.01 - 0.1% of the total mass of the current liquid.

5. The method according to claim 1, characterized in that, In step S5, the mass concentration of ammonia water solution is 10 - 20%; sulfide reagent is added to the sediment in the complexation precipitation tank according to the molar ratio of sulfide ion to cuprous ion of 2 - 2.5:

1. After reacting for 15 - 30 min, cuprous sulfide is formed, and polyacrylamide is added according to 0.05 - 0.2% of the total mass of the current liquid.

6. The method according to claim 1, wherein In step S6, hydrogen peroxide is added to the overflow liquid of the conversion precipitation tank with adjusted pH according to the molar ratio of H2O2 to thiocyanate of 3 - 4:1, and the stripping gas enters the alkali solution absorption tank and is absorbed by a sodium hydroxide solution with a mass percentage of 10 - 25%.

7. The method according to claim 1, characterized in that The cuprous sulfide sediment produced in step S3 and step S5 is transported to a filter press for pressure filtration and then sold externally, and the neutralization residue produced in step S6 is discharged into the tailings pond.

8. The method according to claim 1, wherein The sulfiding reagent in step S3 and step S5 is any one or both of sodium sulfide and sodium hydrosulfide, and the mass concentration is 10 - 25%.

9. The method according to claim 1, wherein In step S4, the activated carbon catalytic oxidation system includes 1 - 3 stages of serially connected activated carbon catalytic oxidation tanks. Each stage of the activated carbon catalytic oxidation tank is provided with a cylindrical activated carbon adsorption column, and a microporous aeration disc for introducing air is arranged at the inner bottom of each stage of the activated carbon catalytic oxidation tank; the empty bed residence time of the overflow liquid of the sulfide precipitation tank in the activated carbon catalytic oxidation tank is 10 - 30 min, and the gas - liquid volume ratio with the introduced air is 10 - 30:

1.

10. The method according to claim 1, wherein In step S6, the stripping gas - liquid volume ratio is 100 - 200:1, the stripping time is 30 - 60 min, and the absorbed absorption liquid is returned to the cyanidation leaching production system.

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