Treatment method of wastewater containing ferricyanide complex and oxalate

Abstract

A treatment method for wastewater containing a ferricyanide complex and oxalate. The method comprises: under weakly acidic to weakly alkaline conditions, firstly, adding a suitable amount of divalent

Description

[0002] With the gradual reduction of energy and mineral resources reserves, researchers from 10 all over the world are actively concerned about the research and development of new energy batteries and the recycling use of resources. In the research of new energy batteries, the sodium electrodes synthesized by raw materials such as one or more hexacyano sodium salts and one or more divalent manganese salts such as manganese chloride, manganese nitrate, manganese sulfate, manganese oxalate, manganese acetate, etc. are of particular interest. In the production 15 process of a certain sodium electrode, wastewater containing ferricyanide complex, oxalate and divalent manganese can be produced.

[0003] Cyanide in water is toxic to both human body and natural ecosystem. China stipulates in the Integrated Wastewater Discharge Standard (GB8978-1996) that in general, the concentration of total cyanide in wastewater discharged by enterprises shall not exceed 0.5mg / L. Compared 20 with other forms of cyanide, ferricyanide, ferrocyanide and cyanide complexed with metal ions are difficult to be treated to meet the requirements of discharge standards by general chemical oxidation method and biological treatment method due to their extremely strong stability, while other high-pressure hydrolysis method and membrane separation method are expensive. Therefore, it is the current focus of many scholars to seek economical and efficient treatment 25 methods of ferricyanide and ferrocyanide.

[0004] Oxalate affects the chemical oxygen demand (COD) of wastewater in a form of organic substance in wastewater. Heavy metal ions are also routine indicators in wastewater treatment. Conventional chemical oxidation method and physical adsorption method are used to treat a large 05 02 24 amount of oxalate ions and heavy metal ions in wastewater, which not only easily leads to high costs of wastewater treatment, but also leads to a waste of a large amount of oxalate and heavy metal resource. Patent application CN114180753A discloses a treatment method of wastewater containing ferricyanide, ferrocyanide and oxalate, which uses the method of producing 5 precipitation by ferrous ion and ferrocyanide and oxalate in wastewater to achieve the purpose of wastewater treatment. Although the wastewater treated by this method meets the third-level discharge requirements in the Integrated Wastewater Discharge Standard, the waste residue generated during the treatment process is treated as hazardous solid waste because it contains ferricyanide precipitation, which increases the costs of solid waste treatment in wastewater 10 treatment processes. SUMMARY

[0005] The present disclosure aims to solve at least one of the above-mentioned technical problems existing in the prior art. Therefore, the present disclosure provides a treatment method 15 of wastewater containing ferricyanide complex and oxalate, which can efficiently and quickly treat wastewater containing ferricyanide complex and oxalate, and can recover manganese resources.

[0006] According to one aspect of the present disclosure, a treatment method of a wastewater containing ferricyanide complex and oxalat is provided, comprising the following steps: 20

[0007] SI: adjusting the pH of the wastewater to 5-9, then adding divalent manganese salt A to the wastewater, stirring for reaction, and then adding flocculant A cationic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a first filtrate and a manganese(II) hexacyanoferrate(II)-based mixed residue; wherein the wastewater contains ferricyanide complex and oxalate, and the mass of the divalent manganese ions in the 25 added divalent manganese salt A is 5-30 times of the mass of the total cyanide in the wastewater;

[0008] S2: adding divalent manganese salt B to the first filtrate, stirring for reaction, and then adding flocculant A cationic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a second filtrate and a filter residue, and performing a rinsing process on the filter residue to recover manganese oxalate; wherein the mass of the 05 02 24 divalent manganese ions in the added divalent manganese salt B is 1.4-7 times of COD in the wastewater;

[0009] S3: adding alkali to the second filtrate to adjust the pH of the second filtrate to 11-13, stirring for reaction, and then adding flocculant B anionic polyacrylamide, and leaving the 5 mixture to stand for settling, and performing solid-liquid separation to obtain a third filtrate and a filter residue, and performing a rinsing process on the filter residue to recover manganese resources;

[0010] S4: adjusting the pH of the third filtrate to 5-8, then adding ferrous salt, stirring for reaction, and then adding flocculant A cationic polyacrylamide, and leaving the mixture to stand 10 for settling, and performing solid-liquid separation to obtain a fourth filtrate; wherein the addition amount of the ferrous salt is 5-30 g / L of the third filtrate;

[0011] S5: adding alkali to the fourth filtrate to adjust the pH of the fourth filtrate to 11-13, stirring for reaction, and then adding flocculant B anionic polyacrylamide, and performing solid-liquid separation to obtain a fifth filtrate. 15

[0012] In some embodiments of the present disclosure, in step SI, the content of total cyanide in the wastewater is 100-2000 mg / L, and the content of COD is 2000-10000 mg / L.

[0013] In some embodiments of the present disclosure, in step SI, the wastewater also contains manganese ions. Further, the content of Mir m the wastewater is 30-300 mg / L.

[0014] In some embodiments of the present disclosure, in step SI, the reagent used for 20 adjusting the pH of the wastewater is at least one of sulfuric acid, hydrochloric acid or nitric acid.

[0015] In some embodiments of the present disclosure, the divalent manganese salt A and the divalent manganese salt B are independently at least one of manganese sulfate, manganese chloride or manganese nitrate.

[0016] In some embodiments of the present disclosure, the flocculant A is a cationic 25 polyacrylamide solution with a mass concentration of 0.5%o-1.5%o; the flocculant B is an anionic polyacrylamide solution with a mass concentration of 0.5%o-1.5%o. Advantages of flocculant A: cationic polyacrylamide adsorbs multiple negatively charged suspended particles in water on its chains through electrostatic effect, so as to aggregate together the dispersed and small suspended 05 02 24 particles, thereby achieving the effect of solid-liquid separation, which is suitable for flocculation of organic wastewater. Advantages of flocculant B: anionic polyacrylamide has negatively charged weakly acidic carboxylic acid groups and strongly acidic sulfonic acid groups, which generate multiple positively charged colloidal particles in wastewater to form bridging adsorption 5 so as to rapidly aggregate together the suspended particles in wastewater, which is suitable for the flocculation of metallurgical wastewater.

[0017] In some embodiments of the present disclosure, in step S2, the mass of the divalent manganese ions m the added divalent manganese salt B is 1.4-4 times of the COD in the wastewater. 10

[0018] In some embodiments of the present disclosure, in step S4, the ferrous salt is at least one of ferrous sulfate, ferrous chloride or ferrous nitrate.

[0019] In some embodiments of the present disclosure, in step S5, the content of total cyanide in the fifth filtrate is <0.5 mg / L, and the content of COD is <500 mg / L, and the content of Mir ' is <0.5 mg / L. 15

[0020] In some embodiments of the present disclosure, step S5 further comprises adjusting the pH of the fifth filtrate to 6-9.

[0021] According to a preferred embodiment of the present disclosure, it has at least the following beneficial effects:

[0022] 1. In the present disclosure, under the condition of weak acidity to weak alkalinity, 20 firstly an appropriate amount of divalent manganese ions are added to make the divalent manganese ions combined with ferrocyanide ions and part of oxalate ions in the wastewater to generate mixed slag mainly composed of manganese ferrocyanide, and solid-liquid separation is performed to achieve the purpose of removing most of the cyanide and a small amount of organic substance; then excess divalent manganese ions are added to the first filtrate to make the divalent 25 manganese ions fully combined with the oxalate in the wastewater to form a precipitate, and solid-liquid separation is performed to achieve the purpose of removing organic substance, preferably, the precipitates obtained by the separation are rinsed, and the manganese oxalate resource is recovered; then an appropriate amount of alkali is added to the second filtrate to make hydroxide act with the excess divalent manganese ions in the second filtrate to form a precipitate, 05 02 24 the precipitate obtained after the separation is rinsed to achieve the purpose of recovering manganese; then an appropriate amount of ferrous salt is added to the third filtrate under the condition of weak acidity to weak alkalinity to make the ferrous ions combined with the remaining cyanide and oxalate ions to form a precipitate, and solid-liquid separation is performed 5 to achieve the purpose of removing the remaining cyanide and organic substance; finally, an appropriate amount of alkali is added to make the hydroxide act with the remaining ferrous ions in the wastewater to generate a precipitate, and solid-liquid separation is performed to achieve the purpose of removing excess ferrous ions in the fourth filtrate.

[0023] 2. The treatment method of the present disclosure can treat ferricyanide complex and 10 oxalate ions simultaneously, efficiently and fast. The content of the total cyanide of the wastewater after treatment is less than 0.5mg / L, and the COD is less than 500mg / L, and the Mn2+ content is less than 0.5mg / L, which meets the third-level standard discharge requirements stipulated in the "Integrated Wastewater Discharge Standard "(GB8978-1996).

[0024] 3. The reagents used in the present disclosure are conventional and easy to obtain, and 15 expensive equipment investment is not necessary, for which the present disclosure has low cost and is easy to be promoted.

[0025] 4. The content of manganese ions in the wastewater of the present disclosure is relatively small, and the manganese ions are in a state of relative equilibrium with the ferrocyanide and oxalate in the wastewater. Although there is a reaction between them at this time, 20 the process is slow. The addition of manganese ions in this process can accelerate the reaction process, and most of the ferrocyanide can be removed first by controlling the addition amount of manganese ions and adjusting the pH. Therefore, using divalent manganese salt for precipitation first can reuse the manganese ions in the wastewater and reduce the treatment cost.

[0026] 5. The manganese oxalate containing a small amount of cyanide generated by the 25 present disclosure can be used for the synthesis of sodium electrode materials, and the excess manganese after treatment can also be recovered for reuse.

[0027] 6. In the present disclosure, the remaining cyanide and oxalate are finally removed by ferrous salt, so that the total cyanide content of the wastewater is as low as 0.5mg / L, and the COD is as low as 500mg / L, which avoids the excessive use of divalent manganese salts and 05 02 24 reduces treatment costs.

[0028] 7. The present disclosure performs resource utilization on both oxalate and manganese ions in the wastewater, which reduces the output of hazardous solid waste in the wastewater treatment process, and reduces the treatment cost of the solid waste residue in the wastewater 5 treatment process. BRIEF DESCRIPTION OF DRAWINGS

[0029] The present disclosure will be further described below in conjunction with the drawings and embodiments, wherein: 10

[0030] FIG. 1 is a process flow chart of the present disclosure. DETAILED DESCRIPTION

[0031] The concept of the present disclosure and the technical effects produced by the present disclosure will be clearly and completely described below with reference to the embodiments, so 15 as to make the purpose, characteristics and effects of the present disclosure fully understood. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments of the present disclosure, other embodiments obtained by those skilled in the art without creative efforts are all within the protection scope of the present disclosure. 20   

[0032] Example 1

[0033] A treatment method of wastewater containing ferricyanide complex and oxalate, with reference to FIG. 1, the specific process is:

[0034] (1) 400 rnL of wastewater containing ferricyanide complex and oxalate was taken and added with 30% dilute sulfuric acid to adjust the pH of the wastewater to 7-8; 25

[0035] (2) Then 7g of manganese sulfate monohydrate was taken and stirred to react for 60min, and then added with 3mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, left to stand for settling, and solid-liquid separated to obtain a 05 02 24 first filtrate;

[0036] (3) 12g manganese sulfate monohydrate was added to the first filtrate and stirred to react for 60min, then added with 2mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, left to stand for settling, and solid-liquid 5 separated to obtain a second filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese oxalate resource;

[0037] (4) 10 mL of 30% sodium hydroxide solution was added to the second filtrate to stabilize the pH of the second filtrate at 12-13 and stirred to react for 30 min, and then added with 2 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was 10 stirred for 5min, and solid-liquid separated to obtain a third filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese resource;

[0038] (5) 30% dilute sulfuric acid was added to the third filtrate to adjust the pH of the wastewater to 6-7, and 350 mL of the third filtrate after the value adjustment was taken and added with 7g ferrous sulfate heptahydrate, stirred to react for 60min, and then added with 1mL of 15 cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 minutes, left to stand for settling, and solid-liquid separated to obtain a fourth filtrate;

[0039] (6) 3.5 mL of 30% sodium hydroxide solution was added to the fourth filtrate to stabilize the pH of the fourth filtrate at 12-13, stirred to react for 30 minutes, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was 20 stirred for 5min, and solid-liquid separated to obtain a fifth filtrate. 30% dilute sulfuric acid was added to the fifth filtrate to adjust the pH of the wastewater to 7.5, and then the wastewater could be discharged. The main components of the wastewater before and after treatment are shown in Table 1.

[0040] Table 1 Main components of wastewater before and after treatment in Example 1 Water sample CNt (mg / L) COD (mg / L) Mn2+ (mg / L) pH Before treatment 499.93 5118.00 80.55 9.7 The first filtrate 6.30 4620.00 2886.00 7.6 The second filtrate 5.46 1804.00 1938.50 7.3 After treatment 0.20 251.50 0.0075 7.5 05 02 24

[0041] Table 1 shows that the cyanide of the first filtrate has been mostly removed, while the COD content is still high, indicating that at a specific pH, with addition of an appropriate amount of divalent manganese salt, the ferrocyanide in the system precipitates first, but only a small amount of oxalate precipitates. In addition, the content of COD in the second filtrate is also 5 related to the content of Mn in the solution.

[0042] Example 2

[0043] A treatment method of wastewater containing ferricyanide complex and oxalate, the specific process is:

[0044] (1) 400 mL of wastewater containing ferricyanide complex and oxalate was taken and 10 added with 30% dilute sulfuric acid to adjust the pH of the wastewater to 6-7;

[0045] (2) Then 8 g of manganese sulfate monohydrate was taken and stirred to react for 60min, and then added with 2mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, left to stand for settling, and solid-liquid separated to obtain a first filtrate; 15

[0046] (3) 12g manganese sulfate monohydrate was added to the first filtrate and stirred to react for 60min, then added with 2mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, left to stand for settling, and solid-liquid separated to obtain a second filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese oxalate resource; 20

[0047] (4) 10 mL of 30% sodium hydroxide solution was added to the second filtrate to stabilize the pH of the second filtrate at 12-13 and stirred to react for 30 min, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, and solid-liquid separated to obtain a third filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese resource; 25

[0048] (5) 30% dilute sulfuric acid was added to the third filtrate to adjust the pH of the wastewater to 6-7, and 350 mL of the third filtrate after the value adjustment was taken and added with 1.75 g ferrous sulfate heptahydrate, stirred to react for 60min, and then added with 1mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 minutes, left to stand for settling, and solid-liquid separated to obtain a fourth filtrate;

[0049] (6) 3.5 rnL of 30% sodium hydroxide solution was added to the fourth filtrate to 5 stabilize the pH of the fourth filtrate at 12-13, stirred to react for 30 minutes, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5min, and solid-liquid separated to obtain a fifth filtrate. 30% dilute sulfuric acid was added to the fifth filtrate to adjust the pH of the wastewater to 7.3, and then the wastewater could be discharged. The main components of the wastewater before and after treatment are shown in 10 Table 2. 05 02 24

[0050] Table 2 Main components of wastewater before and after treatment in Example 2 Water sample CNt (mg / L) COD (mg / L) Mn2+ (mg / L) PH Before treatment 1055.00 5940.00 237.90 9.0 The first filtrate 7.20 5020.00 2369.00 6.5 The second filtrate 6.44 1544.00 1732.25 6.3 After treatment 0.40 452.90 0.0070 7.3

[0051] Example 3

[0052] A treatment method of wastewater containing ferricyanide complex and oxalate, the specific process is: 15

[0053] (1) 400 mL of wastewater containing ferricyanide complex and oxalate was taken and added with 30% dilute sulfuric acid to adjust the pH of the wastewater to 7-8;

[0054] (2) Then 8 g of manganese sulfate monohydrate was taken and stirred to react for 60min, and then added with 3 mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a 20 first filtrate;

[0055] (3) 13 g manganese sulfate monohydrate was added to the first filtrate and stirred to react for 60 min, then added with 2 mL of cationic polyacrylamide solution with a mass 05 02 24 concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a second filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese oxalate resource;

[0056] (4) 10 mL of 30% sodium hydroxide solution was added to the second filtrate to 5 stabilize the pH of the second filtrate at 12-13 and stirred to react for 30 min, and then added with 2 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, and solid-liquid separated to obtain a third filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese resource;

[0057] (5) 30% dilute sulfuric acid was added to the third filtrate to adjust the pH of the 10 wastewater to 6-7, and 350 mL of the third filtrate after the value adjustment was taken and added with 3.5 g ferrous sulfate heptahydrate, stirred to react for 60 min, and then added with 1 mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a fourth filtrate;

[0058] (6) 3.5 mL of 30% sodium hydroxide solution was added to the fourth filtrate to 15 stabilize the pH of the fourth filtrate at 12-13, stirred to react for 30 min, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, and solid-liquid separated to obtain a fifth filtrate. 30% dilute sulfuric acid was added to the fifth filtrate to adjust the pH of the wastewater to 7.0, and then the wastewater could be discharged. The main components of the wastewater before and after treatment are shown in 20 Table 3.

[0059] Table 3 Main components of wastewater before and after treatment in Example 3 Water sample CNt (mg / L) COD (mg / L) Mn2+ (mg / L) pH Before treatment 266.63 4088.00 77.43 8.8 The first filtrate 6.50 3528.00 2579.00 7.2 The second filtrate 4.95 2144.10 2332.50 7.1 After treatment 0.1 163.20 0.0054 7.0

[0060] Comparative example 1 05 02 24

[0061] A treatment method of wastewater containing ferricyanide complex and oxalate, which is different from Example 1 in that the addition amount of ferrous salt was less than 5 g / L. The specific process is:

[0062] (1) 400 mL of wastewater containing ferricyanide complex and oxalate was taken and 5 added with 30% dilute sulfuric acid to adjust the pH of the wastewater to 7-8;

[0063] (2) Then 7 g of manganese sulfate monohydrate was taken and stirred to react for 60 min, and then added with 3 mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a first filtrate; 10

[0064] (3) 12 g manganese sulfate monohydrate was added to the first filtrate and stirred to react for 60 min, then added with 2 mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a second filtrate. The precipitate obtained by separation was rinsed five times to recover the manganese oxalate resource; 15

[0065] (4) 10 mL of 30% sodium hydroxide solution was added to the second filtrate to stabilize the pH of the second filtrate at 12-13 and stirred to react for 30 min, and then added with 2 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, and solid-liquid separated to obtain a third filtrate;

[0066] (5) 30% dilute sulfuric acid was added to the third filtrate to adjust the pH of the 20 wastewater to 6-7, and 350 mL of the third filtrate after the value adjustment was taken and added with 0.7 g ferrous sulfate heptahydrate, stirred to react for 60 min, and then added with 1mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a fourth filtrate;

[0067] (6) 3.5 mL of 30% sodium hydroxide solution was added to the fourth filtrate to 25 stabilize the pH of the fourth filtrate at 12-13, stirred to react for 30 min, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, and solid-liquid separated to obtain a fifth filtrate. 30% dilute sulfuric acid was added to the fifth filtrate to adjust the pH of the wastewater to 7.3, and then the wastewater could be discharged. The main components of the wastewater before and after treatment are shown in Table 4.

[0068] Table 4 Mam components of wastewater before and after treatment in Comparative example 1 Water sample CNt (mg / L) COD (mg / L) Mn2+ (mg / L) pH Before treatment 499.93 5118.00 80.55 9.7 The first filtrate 6.30 4620.00 2886.00 7.6 The second filtrate 5.46 1804.00 1938.50 7.3 After treatment 1.44 273.50 0.0072 7.3

[0069] In Comparative example 1, the addition amount of ferrous salt was less than 5 g / L, and 05 02 24 5 the total cyanide concentration in the wastewater could not be treated to meet the third-level standard discharge requirements stipulated in the "Integrated Wastewater Discharge Standard" (GB8978-1996).

[0070] Comparative example 2

[0071] A treatment method of wastewater containing ferricyanide complex and oxalate, which 10 is different from Example 2 in that there was no step (3). The specific process is:

[0072] (1) 400 mL of wastewater containing ferricyanide complex and oxalate was taken and added with 30% dilute sulfuric acid to adjust the pH of the wastewater to 6-7;

[0073] (2) Then 8 g of manganese sulfate monohydrate was taken and stirred to react for 60 min, and then added with 3 mL of cationic polyacrylamide solution with a mass concentration of 15 l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a first filtrate;

[0074] (3) 10 mL of 30% sodium hydroxide solution was added to the first filtrate to stabilize the pH of the first filtrate at 12-13 and stirred to react for 30 min, and then added with 2 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 20 5min, and solid-liquid separated to obtain a second filtrate;

[0075] (4) 30% dilute sulfuric acid was added to the second filtrate to adjust the pH of the wastewater to 6-7, and 350 mL of the second filtrate after the value adjustment was taken and added with 1.75 g ferrous sulfate heptahydrate, stirred to react for 60 min, and then added with 1 mL of cationic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, left to stand for settling, and solid-liquid separated to obtain a third filtrate;

[0076] (5) 3.5 mL of 30% sodium hydroxide solution was added to the third filtrate to stabilize 5 the pH of the third filtrate at 12-13, stirred to react for 30 min, and then added with 1 mL of anionic polyacrylamide solution with a mass concentration of l%o. The mixture was stirred for 5 min, and solid-liquid separated to obtain a fourth filtrate. 30% dilute sulfuric acid was added to the fourth filtrate to adjust the pH of the wastewater to 7.3, and then the wastewater could be discharged. The main components of the wastewater before and after treatment are shown in 10 Table 5. 05 02 24

[0077] Table 5 Main components of wastewater before and after treatment in Comparative example 2 Water sample CNt (mg / L) COD (mg / L) Mn2+ (mg / L) pH Before treatment 1055.00 5940 111.9 9.0 The first filtrate 7.20 5020.00 2369.00 6.5 After treatment 4.75 3515 0.0065 7.3

[0078] In Comparative example 2, manganese sulfate monohydrate was not added for the second time, and the concentration of total cyanide and COD in the wastewater could not be 15 treated to meet the third-level standard discharge requirements stipulated in the "Integrated Wastewater Discharge Standard" (GB8978-1996). The embodiments of the present disclosure have been described in detail above in conjunction with the drawings, but the present disclosure is not limited to the above-mentioned embodiments, Within the scope of knowledge possessed by those of ordinary skill in the art, 20 various changes can also be made without departing from the spirit of the present disclosure. Furthermore, the embodiments and the features in the embodiments of the present disclosure may be combined with each other without conflict. 05 02 24

Claims

1. A treatment method of wastewater containing ferricyanide complex and oxalate, comprising the following stepsSI: adjusting the pH of the wastewater to 5-9, then adding divalent manganese salt A to the 5 wastewater, stirring for reaction, and then adding flocculant A cationic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a first filtrate and a manganese(II) hexacyanoferrate(II)-based mixed residue; wherein the wastewater contains ferricyanide complex and oxalate, and the mass of the divalent manganese ions in the added divalent manganese salt A is 5-30 times of the mass of the total cyanide in the wastewater;10 S2: adding divalent manganese salt B to the first filtrate, stirring for reaction, and thenadding flocculant A cationic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a second filtrate and a filter residue, and performing a rinsing process on the filter residue to recover manganese oxalate; wherein the mass of the divalent manganese ions in the added divalent manganese salt B is 1.4-7 times of COD in the 15 wastewater;S3: adding alkali to the second filtrate to adjust the pH of the second filtrate to 11-13, stirring for reaction, and then adding flocculant B anionic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a third filtrate and a filter residue, and performing a rinsing process on the filter residue to recover manganese 20 resources;S4: adjusting the pH of the third filtrate to 5-8, then adding ferrous salt, stirring for reaction, and then adding flocculant A cationic polyacrylamide, and leaving the mixture to stand for settling, and performing solid-liquid separation to obtain a fourth filtrate; wherein the addition amount of the ferrous salt is 5-30 g / L of the third filtrate;25 S5: adding alkali to the fourth filtrate to adjust the pH of the fourth filtrate to 11-13, stirringfor reaction, and then adding flocculant B anionic polyacrylamide, and performing solid-liquid separation to obtain a fifth filtrate.

2. The treatment method according to claim 1, wherein in step SI, the content of total cyanide in the wastewater is 100-2000mg / L, and the content of COD is 2000-1 OOOOmg / L.

3. The treatment method according to claim 1, wherein the divalent manganese salt A and the divalent manganese salt B are independently at least one of manganese sulfate, manganese chloride or manganese nitrate.

4. The treatment method according to claim 1, wherein the flocculant A is a cationic 5 polyacrylamide solution with a mass concentration of 0.5%o-1.5%o; the flocculant B is an anionic polyacrylamide solution with a mass concentration of 0.5%o-1.5%o.

5. The treatment method according to claim 1, wherein in step S5, the content of total cyanide in the fifth filtrate is <0.5 mg / L, the content of COD is <500 mg / L, and the content of Mn2+<0.5 mg / L.10xt CMCMLO

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