A biological treatment method for gold smelting wastewater

Abstract

The present application relates to the technical field of wastewater treatment of gold hydrometallurgy process, and particularly discloses a biological treatment method of gold smelting wastewater.A biological treatment method of gold smelting wastewater, comprising acid-base adjustment, sulfidation reaction, first flocculation and precipitation, biological treatment, second flocculation and precipitation, and monitoring and discharge; wherein the immobilized biochar used in the biological treatment is prepared by mixing activated sludge after banana stem, cassava residue and kelp are selected as the source of biochar and then the nutrients such as urea, starch phosphate sodium, phospholipase C, cobalt chloride, zinc chloride and magnesium chloride are attached to the biochar.The present application has the effect of improving the efficiency of biological treatment of acidic wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology in gold hydrometallurgical processes, and in particular to a biological treatment method for gold smelting wastewater. Background Technology

[0002] Gold processing companies typically use hydrometallurgical processes to purify gold and obtain high-purity gold. These processes generally employ aqua regia to dissolve gold and sodium sulfite for selective reduction. Therefore, a large amount of acidic wastewater is generated during the refining process. This acidic wastewater contains high levels of pollutants such as COD, ammonia nitrogen, salts, and heavy metals. If this acidic wastewater is discharged directly without treatment, it will severely impact the natural micro-ecology of rivers and lakes, leading to water pollution.

[0003] Existing processes for treating acidic wastewater from gold hydrometallurgical processes typically employ neutralization, sulfidation, flocculation, physical filtration, or adsorption. The application of biological treatment technology in treating acidic wastewater from gold hydrometallurgical processes is not widespread. This is primarily because salts and heavy metals in the wastewater inhibit the growth of microorganisms in the activated sludge, significantly impacting the efficiency of biological treatment. Therefore, it is necessary to improve the efficiency of biological treatment of acidic wastewater. Summary of the Invention

[0004] To improve the efficiency of biological treatment of acidic wastewater, this application provides a biological treatment method for gold smelting wastewater.

[0005] The biological treatment method for gold smelting wastewater provided in this application adopts the following technical solution:

[0006] A biological treatment method for gold smelting wastewater includes the following purification steps:

[0007] Step 1, pH adjustment: Add an appropriate amount of sodium hydroxide to adjust the pH value to 8-9;

[0008] Step 2, sulfidation reaction: Sodium sulfide is added to generate sulfide precipitate;

[0009] Step 3, First Flocculation and Sedimentation: Add flocculant to precipitate hydroxides and sulfides, and separate the precipitate from the primary wastewater;

[0010] Step 4, biological treatment: Immobilized biochar is added to the primary wastewater, and after a period of degradation, the secondary wastewater is discharged.

[0011] Step 5, Second Flocculation and Sedimentation: Add flocculant again to precipitate organic impurities and separate the sediment and tertiary wastewater;

[0012] Step 6, monitoring discharge: The tertiary wastewater is monitored for water quality and discharged only after it meets the discharge standards;

[0013] Immobilized biochar is prepared through the following steps:

[0014] S1: Select banana stalks, cassava residue, and kelp as biochar sources. Mix banana stalks, cassava residue, and kelp in a mass ratio of 1:(1~1.5):(0.5~1), dry them to remove moisture, crush them, and put them into a carbonization furnace. Heat them to 750~800℃ under anaerobic conditions and process them for 3~5 hours. Then take them out to obtain pre-made biochar.

[0015] S2: Immerse the pre-made biochar completely in the nutrient solution, stir for 5-10 minutes, let stand for 10-20 minutes, filter out the liquid, and dry to obtain biochar;

[0016] S3: Mix biochar, activated sludge, and water in a mass ratio of (1.5-1.8):1:(0.5-0.7), and add a pH adjuster to adjust the pH to 8-9;

[0017] S4: The material obtained in S3 is activated and dried sequentially to obtain immobilized biochar;

[0018] The nutrient solution is a mixture of water, urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride in a mass ratio of 20:(2-5):(1-3):(1-2):(0.5-1):(0.5-1):(0.5-1).

[0019] In the above technical solution, this application designs a series of purification steps for acidic wastewater from the gold hydrometallurgical process, including acid-base adjustment, sulfidation reaction, first flocculation and sedimentation, biological treatment, second flocculation and sedimentation, and monitoring of discharge, to achieve a good purification effect on acidic wastewater from the gold hydrometallurgical process.

[0020] This application specifically prepares immobilized biochar suitable for the purification steps of this application. By specially selecting banana stems, cassava residue, and kelp as biochar sources, banana stems, rich in cellulose and lignin, possess good specific surface area and adsorption capacity after being converted into biochar. Cassava residue also has abundant carbon source, which can promote the growth of microorganisms after being converted into biochar. Kelp has abundant polysaccharides, which can further increase the surface functional groups of biochar after being converted into biochar, thereby improving the adsorption capacity of biochar. The biochar converted from the three has a good synergistic effect, resulting in pre-constituted biochar with better biological activity and adsorption performance, which can promote the growth and activation of microorganisms and adsorb more impurities in wastewater.

[0021] Furthermore, this application further mixes pre-prepared biochar and nutrient solution. Urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride in the nutrient solution adhere tightly to the pre-prepared biochar. Urea, sodium starch phosphate, and phospholipase C provide abundant nutrients for microorganisms, while cobalt chloride, zinc chloride, and magnesium chloride, as trace elements, further promote microbial growth. The combination of these six substances further stimulates the activity of microorganisms in activated sludge, inducing them to produce more specific metabolites and promoting interaction and co-metabolism among different microorganisms. This results in an unexpected effect of promoting microbial co-metabolism. Specifically, the immobilized biochar prepared by mixing such biochar and activated sludge can more effectively remove organic pollutants from wastewater and effectively convert cyanide, which is unavoidable in gold smelting, into harmless substances. This significantly improves wastewater treatment efficiency, effectively solves the current problem of low efficiency in biological wastewater treatment, further improves the conversion rate of factory wastewater, and is conducive to improving the purification efficiency of factory wastewater.

[0022] Preferably, in step S2 of preparing the immobilized biochar, the mass ratio of the biochar to the nutrient solution is 1:20.

[0023] In the above technical solution, by limiting the mass ratio of biochar and nutrient solution in step 2 to 1:20, the absorption of nutrients in the nutrient solution by biochar is promoted. The immobilized biochar prepared by mixing such biochar and activated sludge has a better effect on removing organic pollutants in wastewater, and further significantly improves the wastewater treatment efficiency.

[0024] Preferably, in the preparation of the immobilized biochar, the nutrient solution is a mixture of water, urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride in a mass ratio of 20:5:2.1:1.2:0.8:0.6:0.3.

[0025] In the above technical solution, by further limiting the content of each component in the nutrient solution, urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride achieve a better synergistic effect, further stimulating the activity of microorganisms in activated sludge, inducing microorganisms to produce more specific metabolites, promoting the interaction and co-metabolism between different microorganisms, and further promoting the co-metabolism of microorganisms.

[0026] Preferably, in step S4 of the preparation of immobilized biochar, the activation refers to placing the material obtained in step S3 under a temperature of 20-30°C and a ventilated condition of 70%-75% humidity for 4-5 hours.

[0027] In the above technical solution, the solidified biochar of this application, after undergoing the above activation process, has better bio-adsorption properties, can better remove organic pollutants from wastewater, and further significantly improves the wastewater treatment efficiency.

[0028] Preferably, in step S3 of the preparation of the immobilized biochar, the pH adjuster is sodium hydroxide.

[0029] Preferably, the flocculant includes polyethyleneimine, zeolite powder, and cellulose.

[0030] In the above technical solution, the selected flocculants work together to achieve rapid flocculation, laying a good foundation for subsequent biological treatment steps. At the same time, they can also quickly adsorb impurities generated in the water after biological treatment, improving the purification efficiency of wastewater.

[0031] Preferably, the amount of immobilized biochar added in step 4 is 20-30 g / L.

[0032] In the above technical solution, this application further improves the purification efficiency and the quality of the purified water by limiting the amount of immobilized biochar to 20-30 g / L.

[0033] Preferably, the immobilized biochar treatment time in step 4 is 2.5 to 3 hours.

[0034] In the above technical solution, this application can efficiently complete the biological treatment of wastewater within 2.5 to 3 hours, which significantly improves the biological treatment efficiency of wastewater.

[0035] In summary, this application includes at least one of the following beneficial technical effects:

[0036] 1. This application addresses the acidic wastewater from the gold hydrometallurgical process by designing a purification process that sequentially includes acid-base adjustment, sulfidation reaction, first flocculation and sedimentation, biological treatment, second flocculation and sedimentation, and monitoring of discharge, achieving a good purification effect on the acidic wastewater from the gold hydrometallurgical process.

[0037] 2. This application specifically prepares immobilized biochar suitable for the purification steps of this application. By specially selecting banana stems, cassava residue, and kelp as biochar sources, banana stems, rich in cellulose and lignin, possess good specific surface area and adsorption capacity after being converted into biochar, cassava residue, rich in carbon source, can promote the growth of microorganisms after being converted into biochar, and kelp, rich in polysaccharides, can further increase the surface functional groups of biochar after being converted into biochar, thereby improving the adsorption capacity of biochar. The biochar converted from the three has a good synergistic effect, resulting in pre-constituted biochar with better biological activity and adsorption performance, which can promote the growth and activity of microorganisms and adsorb more impurities in wastewater.

[0038] 3. This application further mixes pre-made biochar and nutrient solution. Urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride in the nutrient solution adhere tightly to the pre-made biochar. Urea, sodium starch phosphate, and phospholipase C provide abundant nutrients for microorganisms, while cobalt chloride, zinc chloride, and magnesium chloride, as trace elements, further promote microbial growth. The combination of these six substances further stimulates the activity of microorganisms in activated sludge, induces microorganisms to produce more specific metabolites, and promotes the interaction and co-metabolism between different microorganisms, resulting in an unexpected effect on promoting microbial co-metabolism. Specifically, the immobilized biochar prepared by mixing such biochar and activated sludge can more effectively remove organic pollutants from wastewater and can also effectively convert cyanide, which is unavoidable in gold smelting, into harmless substances, significantly improving wastewater treatment efficiency. This effectively solves the problem of low efficiency in current biological wastewater treatment, further improves the conversion rate of factory wastewater, and is conducive to improving the purification efficiency of factory wastewater. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0040] Preparation Example 1

[0041] An immobilized biochar is prepared through the following steps:

[0042] Step S1: Mix banana stalks, cassava residue, and kelp in a mass ratio of 1:1.5:0.5, dry them to remove moisture, crush them, put them into a carbonization furnace, heat them to 750°C under anaerobic conditions, process them for 3 hours, and then take them out to obtain pre-made biochar.

[0043] Step S2: Immerse the pre-made biochar completely in the nutrient solution. The mass ratio of biochar to nutrient solution is 1:20. Stir for 10 minutes, let stand for 10 minutes, filter out the liquid, and dry to obtain biochar.

[0044] Step S3: Mix biochar, activated sludge, and water in a mass ratio of 1.5:1:0.5, add sodium hydroxide to adjust the pH to 8, and obtain the initial immobilized biochar.

[0045] Step S4: Place the pre-prepared immobilized biochar at 20°C and 70% humidity for 4 hours to obtain activated immobilized biochar.

[0046] Step S5: After drying to remove the moisture from the activated and immobilized biochar, immobilized biochar is obtained.

[0047] The nutrient solution is made by mixing and stirring 20kg of water, 2kg of urea, 3kg of sodium starch phosphate, 1kg of phospholipase C, 0.5kg of cobalt chloride, 0.5kg of zinc chloride, and 0.5kg of magnesium chloride.

[0048] The activated sludge was taken from the bottom of the biological treatment tank in the gold processing plant, and its water content accounted for about 13% of the total mass.

[0049] Preparation Example 2

[0050] An immobilized biochar, unlike preparation example 1, was prepared by the following steps:

[0051] Step S1: Mix banana stalks, cassava residue, and kelp in a mass ratio of 1:1:1, dry them to remove moisture, crush them, put them into a carbonization furnace, heat them to 800°C under anaerobic conditions, process them for 5 hours, and then take them out to obtain pre-made biochar.

[0052] Step S2: Immerse the pre-made biochar completely in the nutrient solution, stir for 5 minutes, let stand for 20 minutes, filter out the liquid, and dry to obtain biochar.

[0053] Step S3: Mix biochar, activated sludge, and water in a mass ratio of 1.8:1:0.7, add sodium hydroxide to adjust the pH to 9, and obtain the initial immobilized biochar.

[0054] Step S4: Place the initially prepared immobilized biochar at a temperature of 30°C and a humidity of 75% for 5 hours to obtain activated immobilized biochar.

[0055] Step S5: After drying to remove the moisture from the activated and immobilized biochar, immobilized biochar is obtained.

[0056] The nutrient solution is made by mixing and stirring 20kg of water, 5kg of urea, 1kg of sodium starch phosphate, 2kg of phospholipase C, 1kg of cobalt chloride, 1kg of zinc chloride, and 1kg of magnesium chloride.

[0057] Preparation Example 3

[0058] An immobilized biochar differs from Preparation Example 1 in that the nutrient solution is prepared by mixing and stirring 20 kg of water, 5 kg of urea, 2.1 kg of sodium starch phosphate, 1.2 kg of phospholipase C, 0.8 kg of cobalt chloride, 0.6 kg of zinc chloride, and 0.3 kg of magnesium chloride.

[0059] Comparative Preparation Example 1

[0060] An immobilized biochar, unlike preparation example 1, in which urea was not added to the nutrient solution.

[0061] Comparative Preparation Example 2

[0062] An immobilized biochar, unlike Preparation Example 1, did not have sodium starch phosphate added to the nutrient solution.

[0063] Comparative preparation example 3

[0064] An immobilized biochar, unlike preparation example 1, does not have phospholipase C added to the nutrient solution.

[0065] Comparative preparation example 4

[0066] An immobilized biochar, unlike the preparation example 1, did not have cobalt chloride, zinc chloride, or magnesium chloride added to the nutrient solution.

[0067] Comparative preparation example 5

[0068] An immobilized biochar, unlike Preparation Example 1, uses only banana stems as the biochar source in step S1.

[0069] Example 1

[0070] A biological treatment method for gold smelting wastewater, in this embodiment using acidic wastewater generated from a batch of gold hydrometallurgical refining process.

[0071] The specific purification steps for wastewater are as follows:

[0072] Step 1, pH adjustment: Add an appropriate amount of sodium hydroxide to adjust the pH value to 8.

[0073] Step 2, sulfidation reaction: Sodium sulfide is added to generate sulfide precipitate.

[0074] Step 3, first flocculation and sedimentation: Add flocculant (the flocculant is a compound of polyethyleneimine, zeolite powder and cellulose in a mass ratio of 10:3:1), stir at 200 r / min for 2 min and let stand for 30 min to precipitate hydroxides and sulfides, and separate the precipitate from the primary wastewater.

[0075] Step 4, biological treatment: Add immobilized biochar to the primary wastewater at a rate of 30 g / L, stir at a constant speed of 150 r / min, and after degradation for 3 hours, discharge the secondary wastewater.

[0076] Step 5, Second Flocculation and Sedimentation: Add flocculant again (the flocculant is a compound of polyethyleneimine, zeolite powder and cellulose in a mass ratio of 10:3:1), stir at 200r / min for 2min, and let stand for 30min to precipitate organic impurities and separate the precipitate and tertiary wastewater.

[0077] Step 6, monitoring discharge: The tertiary wastewater is monitored for water quality and discharged only after it meets the discharge standards.

[0078] The immobilized biochar was prepared in Preparation Example 1.

[0079] Example 2

[0080] A biological treatment method for gold smelting wastewater, which differs from Example 1 in that the specific purification steps are as follows:

[0081] Step 1, pH adjustment: Add an appropriate amount of sodium hydroxide to adjust the pH value to 9.

[0082] Step 2, sulfidation reaction: Sodium sulfide is added to generate sulfide precipitate.

[0083] Step 3, First flocculation and sedimentation: Add flocculant (the flocculant is a compound of polyethyleneimine, zeolite powder and cellulose in a mass ratio of 10:5:0.5), stir at 200 r / min for 2 min and let stand for 30 min to precipitate hydroxides and sulfides, and separate the precipitate from the primary wastewater.

[0084] Step 4, biological treatment: Add immobilized biochar to the primary wastewater at a dosage of 20 g / L, stir at a uniform speed of 150 r / min, and after degradation for 2.5 h, discharge the secondary wastewater.

[0085] Step 5, Second Flocculation and Sedimentation: Add flocculant again (the flocculant is a compound of polyethyleneimine, zeolite powder and cellulose in a mass ratio of 10:5:0.5), stir at 200 r / min for 2 min and let stand for 30 min to precipitate organic impurities and separate the precipitate and tertiary wastewater.

[0086] Step 6, monitoring discharge: The tertiary wastewater is monitored for water quality and discharged only after it meets the discharge standards.

[0087] The immobilized biochar was prepared in Preparation Example 2.

[0088] Example 3

[0089] A biological treatment method for gold smelting wastewater, which differs from Example 1 in that the immobilized biochar is prepared by Preparation Example 3.

[0090] verify

[0091] Verification 1:

[0092] Verification samples: Immobilized biochar from the above preparation examples and comparative preparation examples.

[0093] Verification method: Eight test tanks of the same specifications were selected, and 10L of wastewater was added to each test tank. The COD in the wastewater was about 130mg / L, ammonia nitrogen was about 40mg / L, total copper was about 6mg / L, and total cyanide was about 0.13mg / L.

[0094] Immobilized biochar from each of the above preparation examples and the comparative preparation examples was added to the test tank at a rate of 200g. After addition, the mixture was stirred at a constant speed of 150r / min. After 2.5h, samples were taken, the immobilized biochar was filtered out, and the COD content, ammonia nitrogen content, total copper content, and total cyanide content were tested.

[0095] The test results are shown in Table 1.

[0096] Table 1:

[0097]

[0098] By combining the preparation examples 1-3, the comparative preparation examples 1-5, and Table 1, it is easy to see that the immobilized biochar of preparation examples 1-3 has a good effect on removing organic pollutants from wastewater.

[0099] Specifically, by combining the analysis of Preparation Example 1 and Comparative Preparation Example 5, it is easy to see that Preparation Example 1 has a better effect on removing organic pollutants from wastewater. This analysis shows that by specifically selecting banana stalks, cassava residue, and kelp as biochar sources, the biochar converted from these three materials has a good synergistic effect, resulting in pre-made biochar with better biological activity and adsorption performance. This pre-made biochar can promote the growth and activity of microorganisms and adsorb more impurities in wastewater.

[0100] Specifically, combining the analysis of Preparation Example 1 and Comparative Preparation Examples 1-4, it is clear that Preparation Example 1 demonstrates a superior effect in removing organic pollutants from wastewater. This analysis shows that urea, sodium starch phosphate, and phospholipase C in the nutrient solution provide abundant nutrients for microorganisms, while cobalt chloride, zinc chloride, and magnesium chloride, as trace elements, further promote microbial growth. The combination of these six substances further stimulates the activity of microorganisms in activated sludge, inducing them to produce more specific metabolites and promoting interactions and co-metabolism among different microorganisms. This results in an unexpected effect of promoting microbial co-metabolism. Specifically, the immobilized biochar prepared by mixing such biochar with activated sludge can more effectively remove organic pollutants from wastewater and can also effectively convert cyanide, which is unavoidable in gold smelting, into harmless substances. This significantly improves wastewater treatment efficiency, effectively solves the current problem of low efficiency in biological wastewater treatment, further improves the conversion rate of factory wastewater, and is conducive to improving the purification efficiency of factory wastewater.

[0101] Verification 2:

[0102] The acidic wastewater generated by the gold hydrometallurgical process was purified according to the steps in Examples 1-3, and the indicators of the purified wastewater were tested to see if they met the standards in accordance with GB8978-1996 "Integrated Wastewater Discharge Standard".

[0103] The test results showed that the COD content of Example 1 was 32 mg / L, the ammonia nitrogen content was 1.75 mg / L, the total copper content was 0.001 mg / L, and the total cyanide content was 0.001 mg / L, which met the Class I discharge standard of the "Integrated Wastewater Discharge Standard".

[0104] The COD content of Example 2 was 37 mg / L, the ammonia nitrogen content was 2.13 mg / L, the total copper content was 0.001 mg / L, and the total cyanide content was 0.001 mg / L, which met the Class I discharge standard of the "Integrated Wastewater Discharge Standard".

[0105] The COD content of Example 3 was 29 mg / L, the ammonia nitrogen content was 1.64 mg / L, the total copper content was 0.001 mg / L, and the total cyanide compound content was 0.001 mg / L, which met the Class I discharge standard of the "Integrated Wastewater Discharge Standard".

[0106] The test results of the purified wastewater in Examples 1-3 show that this application has a good purification effect on the acidic wastewater generated by the gold hydrometallurgical process. The biological treatment method of this application is reasonable and reliable and has a good wastewater treatment effect.

[0107] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A biological treatment method for gold smelting wastewater, characterized in that, The purification process includes the following steps: Step 1, pH adjustment: Add an appropriate amount of sodium hydroxide to adjust the pH value to 8-9; Step 2, sulfidation reaction: Sodium sulfide is added to generate sulfide precipitate; Step 3, First Flocculation and Sedimentation: Add flocculant to precipitate hydroxides and sulfides, and separate the precipitate from the primary wastewater; Step 4, biological treatment: Immobilized biochar is added to the primary wastewater, and after a period of degradation, the secondary wastewater is discharged. Step 5, Second Flocculation and Sedimentation: Add flocculant again to precipitate organic impurities and separate the sediment and tertiary wastewater; Step 6, monitoring discharge: The tertiary wastewater is monitored for water quality and discharged only after it meets the discharge standards; Immobilized biochar is prepared through the following steps: S1: Select banana stalks, cassava residue, and kelp as biochar sources. Mix banana stalks, cassava residue, and kelp in a mass ratio of 1:(1~1.5):(0.5~1), dry them to remove moisture, crush them, and then put them into a carbonization furnace. Heat them to 750~800℃ under anaerobic conditions and process them for 3~5 hours. Then take them out to obtain pre-made biochar. S2: Immerse the pre-made biochar completely in the nutrient solution, stir for 5-10 minutes, let stand for 10-20 minutes, filter out the liquid, and dry to obtain biochar; S3: Mix biochar, activated sludge, and water in a mass ratio of (1.5~1.8):1:(0.5~0.7), and add a pH adjuster to adjust the pH to 8~9; S4: The material obtained in S3 is activated and dried sequentially to obtain immobilized biochar; The nutrient solution is a mixture of water, urea, sodium starch phosphate, phospholipase C, cobalt chloride, zinc chloride, and magnesium chloride in a mass ratio of 20:(2~5):(1~3):(1~2):(0.5~1):(0.5~1):(0.5~1). In step S2 of the preparation of immobilized biochar, the mass ratio of biochar to nutrient solution is 1:

20.

2. The biological treatment method for gold smelting wastewater according to claim 1, characterized in that, In step S4 of the preparation of immobilized biochar, activation refers to placing the material from step S3 at a temperature of 20-30°C and a humidity of 70-75% under ventilation conditions for 4-5 hours.

3. The biological treatment method for gold smelting wastewater according to claim 1, characterized in that, In step S3 of the preparation of the immobilized biochar, the pH adjuster is sodium hydroxide.

4. The biological treatment method for gold smelting wastewater according to claim 1, characterized in that, The flocculant includes polyethyleneimine, zeolite powder, and cellulose.

5. The biological treatment method for gold smelting wastewater according to claim 1, characterized in that, The amount of immobilized biochar added in step 4 is 20~30g / L.

6. The biological treatment method for gold smelting wastewater according to claim 5, characterized in that, The immobilized biochar treatment time in step 4 is 2.5~3 hours.

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