Treatment methods for wastewater from cobalt carbonate production and cobalt carbonate production methods

Abstract

This invention discloses a method for treating wastewater from cobalt carbonate production and a method for producing cobalt carbonate, solving the technical problems of high energy consumption and high impurity levels of ammonium chloride salts in existing technologies. The method for treating wastewater from cobalt carbonate production includes the following steps: Step 10, pretreating the mother liquor to reduce its suspended solids (SS) content and pH, obtaining a clear mother liquor; Step 20, pretreating the wash water to reduce its SS content and pH, obtaining washing water; Step 30, concentrating a first mixture containing washing water and condensate to obtain a first concentrated water with high TDS content and a first product water with low TDS content; Step 40, evaporating and crystallizing a second mixture containing the first concentrated water and clear mother liquor to obtain condensate and ammonium chloride salts; Step 50, concentrating the first product water to obtain a second concentrated water with high TDS content and a second product water with low TDS content; the second product water is recycled to the washing process in cobalt carbonate production; the second concentrated water is recycled.

Description

Technical Field

[0001] This invention relates to the technical field of cobalt carbonate production, and more specifically, to a method for treating wastewater from cobalt carbonate production and a method for producing cobalt carbonate. Background Technology

[0002] Cobalt carbonate (CoCO3) is a compound primarily used in industry and laboratories, with a wide range of applications. For example, it is a precursor to lithium-ion battery cathode materials (such as lithium cobalt oxide, LiCoO2), a catalyst in organic compounds such as Fischer-Tropsch synthesis and hydrocarbon hydrogenation reactions, and a raw material for manufacturing magnetic materials (such as cobalt ferrite, CoFe2O4), among others.

[0003] One production process for cobalt carbonate is as follows: precipitation reaction → solid-liquid separation → washing → drying. Cobalt chloride (CoCl2), hydrochloric acid, and ammonium bicarbonate (NH4HCO3) are mixed in a reactor and undergo a precipitation reaction to produce solid cobalt carbonate, ammonium chloride (NH4Cl), carbon dioxide, and water. The chemical reaction formula is: CoCl2 + HCl + NH4HCO3 → CoCO3(s) + NH4Cl + CO2 + H2O. After the reaction is complete, the solid-liquid mixture containing solid cobalt carbonate, ammonium chloride, and water is sent to a filter for solid-liquid separation. The solid cobalt carbonate is separated, yielding a mother liquor and solid cobalt carbonate with attached impurities. The solid cobalt carbonate is washed with pure water to remove impurities; the resulting wash water is called wash water. The washed solid cobalt carbonate is then dried to obtain the final cobalt carbonate product.

[0004] In the above process, mother liquor and washing water are generated. The existing treatment method is to mix the two and then evaporate and crystallize them to recover ammonium chloride. However, direct evaporation and crystallization has high energy consumption and the resulting ammonium chloride has high impurity content. Summary of the Invention

[0005] The main objective of this invention is to provide a method for treating wastewater from cobalt carbonate production, a method for producing cobalt carbonate, a system for treating wastewater from cobalt carbonate production, and a system for producing cobalt carbonate, in order to solve the technical problems of high energy consumption and high impurity levels of ammonium chloride salts in the prior art.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for treating wastewater from cobalt carbonate production and a method for producing cobalt carbonate are provided, the technical solution of which is as follows:

[0007] A method for treating wastewater from cobalt carbonate production, wherein cobalt carbonate production includes a precipitation reaction process, a solid-liquid separation process, and a washing process, and the production wastewater includes mother liquor and wash water, wherein the mother liquor originates from the solid-liquid separation process and the wash water originates from the washing process, and the treatment method includes the following steps:

[0008] Step 10: Pre-treat the mother liquor to reduce the SS content and pH of the mother liquor, and obtain a clear mother liquor;

[0009] Step 20: Pre-treat the wash water to reduce the SS content and pH of the wash water to obtain cleaning water;

[0010] Step 30: The first mixture containing washing water and condensate is concentrated to obtain a first concentrate with high TDS content and a first product water with low TDS content.

[0011] Step 40: The second mixture containing the first concentrated water and the clear mother liquor is subjected to evaporation and crystallization treatment to obtain condensate and ammonium chloride.

[0012] Step 50: The first product water is concentrated to obtain a second concentrate with high TDS content and a second product water with low TDS content; the second product water is returned to the washing process in the cobalt carbonate production; the second concentrate is then refluxed.

[0013] As a further improvement to the above-mentioned method for treating cobalt carbonate production wastewater, Step 10 specifically includes:

[0014] Step 11: Filter the mother liquor to obtain the first filtrate with SS content ≤0.2mg / L;

[0015] Step 12: Adjust the pH of the first filtrate to obtain a clear mother liquor with a pH of 7-8.

[0016] As a further improvement to the above-mentioned method for treating cobalt carbonate production wastewater, Step 20 specifically includes:

[0017] Step 21: Filter the wash water and the recirculated concentrated wash water to obtain a second filtrate with an SS content ≤0.2mg / L;

[0018] Step 22: Adjust the pH of the second filtrate to obtain a third filtrate with a pH of 6-7;

[0019] Step 23: The third filtrate is subjected to ultrafiltration to obtain washing water and concentrated washing water; the concentrated washing water is returned to Step 21 for filtration.

[0020] As a further improvement to the above-mentioned cobalt carbonate production wastewater treatment method, Step 30 specifically includes:

[0021] Step 31: The first mixture is subjected to reverse osmosis concentration treatment to obtain a first intermediate concentrate and a first intermediate permeate; the TDS content of the first intermediate concentrate is 3 to 6 times that of the first mixture.

[0022] Step 32: The first intermediate concentrate is subjected to reverse osmosis concentration treatment to obtain the first concentrate and the second intermediate permeate; the TDS content of the first concentrate is 2 to 5 times that of the first intermediate concentrate; the first intermediate permeate and the second intermediate permeate constitute the first permeate.

[0023] As a further improvement to the above-mentioned method for treating cobalt carbonate production wastewater, Step 40 specifically includes:

[0024] Step 41: Evaporate and crystallize the second mixture to obtain water of crystallization and crystalline salt;

[0025] Step 42: Dry the crystalline salt to obtain ammonium chloride salt;

[0026] Step 43: Heat exchange treatment is performed on the water of crystallization to obtain condensate.

[0027] As a further improvement to the above-mentioned method for treating cobalt carbonate production wastewater, Step 50 specifically includes:

[0028] Step 51: The intermediate liquid consisting of the first permeate and the refluxed second concentrate is subjected to reverse osmosis concentration treatment to obtain the second intermediate concentrate and the third intermediate permeate; the second intermediate concentrate is refluxed to Step 30 for concentration treatment; the TDS content of the second intermediate concentrate is 4 to 7 times that of the intermediate liquid.

[0029] Step 52: The third intermediate permeate is concentrated by reverse osmosis to obtain the second concentrate and the second permeate; the second concentrate is returned to Step 510 for further concentration; the TDS content of the second concentrate is 4 to 7 times that of the third intermediate permeate; the TDS content of the second permeate is ≤10 mg / L.

[0030] As a further improvement to the above-mentioned method for treating wastewater from cobalt carbonate production: the cobalt carbonate is obtained by reacting cobalt chloride, hydrochloric acid and ammonium bicarbonate, and in Step 10 and Step 20, hydrochloric acid with a mass fraction of 31% is used to adjust the pH.

[0031] As a further improvement to the above-mentioned cobalt carbonate production wastewater treatment method: the mother liquor has a TDS content of 75,000–95,000 mg / L, an SS content of 25–35 mg / L, and a pH of 8.5–9.5; the wash water has a TDS content of 500–1,500 mg / L, an SS content of 5–15 mg / L, and a pH of 7–8.

[0032] As a further improvement to the above-mentioned cobalt carbonate production wastewater treatment method: the TDS content of the first mixed solution is 1000-1300 mg / L, and the pH is 5.5-6.5; the TDS content of the second mixed solution is 70000-85000 mg / L, and the pH is 7.5-8.5.

[0033] The cobalt carbonate production method includes a precipitation reaction process, a solid-liquid separation process, and a washing process. It also includes a method for treating the cobalt carbonate production wastewater, specifically treating the mother liquor from the solid-liquid separation process and the wash water from the washing process.

[0034] To achieve the above objectives, according to a second aspect of the present invention, a wastewater treatment system for cobalt carbonate production and a cobalt carbonate production system are provided, the technical solution of which is as follows:

[0035] A wastewater treatment system for cobalt carbonate production, wherein cobalt carbonate production includes a precipitation reaction unit, a solid-liquid separation unit, and a washing unit, and the production wastewater includes mother liquor and wash water, wherein the mother liquor originates from the solid-liquid separation unit and the wash water originates from the washing unit; the treatment system includes:

[0036] The mother liquor pretreatment unit is used to pretreat the mother liquor to reduce its SS content and pH and output a clear mother liquor.

[0037] The wash water pretreatment unit is used to pretreat the wash water to reduce the SS content and pH of the wash water and output the cleaning water.

[0038] The first concentration unit is used to concentrate the first mixture containing washing water and condensate and output the first concentrated water with high TDS content and the first product water with low TDS content.

[0039] An evaporation and crystallization unit is used to perform evaporation and crystallization treatment on a second mixture containing a first concentrated water and a clear mother liquor, and output condensate and ammonium chloride.

[0040] The second concentration unit is used to concentrate the first product water and output a second concentrated water with high TDS content and a second product water with low TDS content; the second product water is returned to the washing unit in the cobalt carbonate production.

[0041] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the mother liquor pretreatment unit includes:

[0042] The raw mother liquor tank is used to store the mother liquor from the solid-liquid separation unit.

[0043] The first filtration device is used to filter the mother liquor output from the raw water tank and output a first filtrate and a first filter residue with an SS content ≤0.2mg / L; the first filtrate is stored in a first filtrate storage tank; the first filter residue is stored in a first filter residue storage tank.

[0044] The first pH adjustment tank is used to adjust the pH of the first filtrate output from the first filtrate storage tank and to input the clear mother liquor with a pH of 7 to 8 into the second mixed liquor storage tank;

[0045] The first feeding device is used to add acidic reagents to the first pH adjustment tank.

[0046] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the mother liquor pretreatment unit further includes a first filter press device for pressing the first filter residue in the first filter residue storage tank.

[0047] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the wash water pretreatment unit includes:

[0048] The wash water tank is used to store wash water from the washing unit and concentrated wash water returned from the washing unit.

[0049] The second filtration device is used to filter the wash water output from the raw wash water tank and output a second filtrate and a second filter residue with an SS content ≤0.2mg / L; the second filtrate is stored in a second filtrate storage tank; the second filter residue is stored in a second filter residue storage tank.

[0050] The second pH adjustment tank is used to adjust the pH of the second filtrate output from the second filtrate storage tank and output the third filtrate with a pH of 6 to 7.

[0051] The second feeding device is used to add acidic reagents to the second pH adjustment tank;

[0052] An ultrafiltration device is used to perform ultrafiltration treatment on the third filtrate output from the second pH adjustment tank and output cleaning water and concentrated wash water; the cleaning water is stored in the first mixed liquid storage tank; the concentrated wash water is stored in the wash water source tank.

[0053] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the washing water pretreatment unit further includes a second filter press device for pressing the second filter residue in the second filter residue storage tank.

[0054] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system: the first concentration unit includes:

[0055] The first reverse osmosis unit is used to concentrate the first mixed solution output from the first mixed solution storage tank and output the first intermediate concentrate and the first intermediate permeate.

[0056] The second reverse osmosis unit is used to concentrate the first intermediate concentrate and output the first concentrate and the second intermediate permeate; the first concentrate is stored in the second mixed liquor storage tank; the first intermediate permeate and the second intermediate permeate constitute the first permeate and are stored in the intermediate tank.

[0057] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the evaporation and crystallization unit includes:

[0058] An evaporation crystallization device is used to evaporate and crystallize the second mixture output from the second mixture storage tank and output crystal water and crystal salt.

[0059] Drying equipment is used to dry crystalline salts and output ammonium chloride salts;

[0060] A heat exchange device is used to treat the water of crystallization by heat exchange and output condensate, wherein the condensate is stored in a first mixed liquid storage tank.

[0061] As a further improvement to the aforementioned cobalt carbonate production wastewater treatment system, the second concentration unit includes:

[0062] The third reverse osmosis unit is used to perform reverse osmosis concentration treatment on the intermediate liquid composed of the first product water and the second concentrate returned, and output the second intermediate concentrate and the third intermediate product water; the second intermediate concentrate is stored in the first mixed liquid storage tank;

[0063] The fourth reverse osmosis unit is used to concentrate the third intermediate permeate by reverse osmosis and output the second concentrate and the second permeate; the second concentrate is returned to the intermediate tank and mixed with the first permeate to form an intermediate liquid.

[0064] The cobalt carbonate production system includes a precipitation reaction unit, a solid-liquid separation unit, and a washing unit, and also includes a cobalt carbonate production wastewater treatment system, which is used to treat the mother liquor from the solid-liquid separation unit and the wash water from the washing unit.

[0065] It is evident that the present invention has the following advantages:

[0066] (1) This invention fully considers the differences in water volume and composition between the mother liquor and the wash water. It first uses different pretreatment methods to treat the mother liquor and wash water separately, then combines them to obtain two mixed solutions (first mixed solution and second mixed solution) suitable for concentration and evaporation crystallization. This reduces mutual interference between the mother liquor and wash water caused by production fluctuations, allowing each processing unit to operate under optimal conditions. The processing process is more controllable and stable, reducing the impact of production fluctuations on the system and improving the overall stability, operability, and processing efficiency of the process. The processing units at each stage of this invention have clear division of labor. The modular design and segmented processing can be flexibly adjusted according to production needs, making it suitable for different production scales and conditions, thus enhancing the system's adaptability and flexibility.

[0067] (2) This invention first pre-treats the mother liquor and wash water, effectively removing larger particles and suspended impurities. On the one hand, this reduces the risk of clogging in the two-stage concentration units (first and second concentration units) and the evaporation crystallization unit, thereby reducing the system's maintenance requirements. On the other hand, it results in a lower content of ammonium chloride impurities generated during the evaporation crystallization process, improving the purity of the final by-product. Secondly, by using two-stage concentration units for further separation and purification, not only is the volume of liquid requiring evaporation crystallization reduced, thus reducing energy consumption during the evaporation process, but it also ensures that the liquid entering the evaporation crystallization unit is purer, resulting in higher purity of the final crystallized ammonium chloride. This significantly enhances the commercial value of the by-product and helps generate additional revenue.

[0068] (3) The second product water treated by the second concentration unit of the present invention can be directly reused in the washing unit, reducing the dependence of the cobalt carbonate production system on fresh water resources. Recycling the condensate not only saves water resources but also reduces wastewater discharge and lowers the negative impact on the environment.

[0069] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0070] The accompanying drawings, which form part of this invention, are used to aid in understanding the invention. The content provided in the drawings and their related descriptions can be used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0071] Figure 1 This is a schematic diagram of an embodiment of the cobalt carbonate production system of the present invention.

[0072] Figure 2 This is a schematic diagram of an embodiment of the cobalt carbonate production wastewater treatment system of the present invention.

[0073] The relevant markings in the above figures are:

[0074] 110 - Precipitation reaction unit, 120 - Solid-liquid separation unit, 130 - Washing unit, 140 - Drying unit, 210 - Mother liquor raw water tank, 220 - First filtration device, 230 - First pH adjustment tank, 240 - First feeding device, 250 - First filter press device, 310 - Wash water raw water tank, 320 - Second filtration device, 330 - Second pH adjustment tank, 340 - Second feeding device, 350 - Second filter press device, 360 - Ultrafiltration device, 410 - First reverse osmosis device, 420 - Second reverse osmosis device, 510 - Evaporation and crystallization device, 520 - Drying device, 530 - Heat exchange device, 610 - Third reverse osmosis device, 620 - Fourth reverse osmosis device, 710 - First mixed liquor storage tank, 720 - Second mixed liquor storage tank, 730 - Intermediate tank. Detailed Implementation

[0075] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0076] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0077] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0078] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0079] Figure 1 This is a schematic diagram of an embodiment of the cobalt carbonate production system of the present invention.

[0080] like Figure 1As shown, the cobalt carbonate production system includes a precipitation reaction unit 110, a solid-liquid separation unit 120, a washing unit 130, a drying unit 140, and a cobalt carbonate production wastewater treatment system. The precipitation reaction unit 110 includes a reaction vessel where cobalt chloride, hydrochloric acid, and ammonium bicarbonate are mixed and undergo a precipitation reaction to produce solid cobalt carbonate, ammonium chloride, carbon dioxide, and water. After the reaction, the solid-liquid mixture of solid cobalt carbonate, ammonium chloride, and water is fed into the solid-liquid separation unit 120, which includes a filter. The solid cobalt carbonate is separated by the filter, yielding mother liquor and solid cobalt carbonate with attached impurities. The solid cobalt carbonate with attached impurities is then fed into the washing unit 130, which uses pure water and / or secondary product water (from...). Figure 2 The wastewater treatment system for cobalt carbonate production shown washes solid cobalt carbonate to remove impurities, yielding wash water and clean solid cobalt carbonate. Drying unit 140 dries the clean solid cobalt carbonate to obtain the cobalt carbonate product. The wastewater treatment system for cobalt carbonate production is used to treat the mother liquor from solid-liquid separation unit 120 and the wash water from washing unit 130.

[0081] Figure 2 This is a schematic diagram of an embodiment of the cobalt carbonate production wastewater treatment system of the present invention.

[0082] like Figure 2 As shown, the cobalt carbonate production wastewater treatment system includes a mother liquor pretreatment unit, a wash water pretreatment unit, a first concentration unit, an evaporation and crystallization unit, and a second concentration unit. The mother liquor pretreatment unit pretreats the mother liquor to reduce its suspended solids (SS) content and pH, and outputs a clear mother liquor. The wash water pretreatment unit pretreats the wash water to reduce its SS content and pH, and outputs washing water. The first concentration unit concentrates a first mixture containing washing water, condensate, and a second intermediate concentrate, outputting a first concentrate with high TDS content and a first product water with low TDS content. The evaporation and crystallization unit evaporates and crystallizes a second mixture containing the first concentrate and clear mother liquor, outputting condensate and ammonium chloride. The second concentration unit concentrates the first product water, outputting a second concentrate with high TDS content and a second product water with low TDS content; the second product water is recycled to... Figure 1 The washing unit 130 in the cobalt carbonate production system shown is used to wash solid cobalt carbonate.

[0083] The mother liquor pretreatment unit includes a mother liquor raw water tank 210, a first filtration device 220, a first pH adjustment tank 230, a first feeding device 240, and a first filter press 250. The mother liquor raw water tank 210 stores the mother liquor from the solid-liquid separation unit 120. The first filtration device 220 filters the mother liquor output from the mother liquor raw water tank 210 and outputs a first filtrate and a first filter residue with an SS content ≤0.2 mg / L. The first filtrate is stored in a first filtrate storage tank, and the first filter residue is stored in a first filter residue storage tank. The first pH adjustment tank 230 adjusts the pH of the first filtrate output from the first filtrate storage tank and inputs a clear mother liquor with a pH of 7-8 into a second mixed liquor storage tank 720. The first feeding device 240 adds an acidic reagent to the first pH adjustment tank 230. The first filter press 250 filters the first filter residue in the first filter residue storage tank.

[0084] The wash water pretreatment unit includes a wash water raw water tank 310, a second filtration device 320, a second pH adjustment tank 330, a second feeding device 340, a second filter press 350, and an ultrafiltration device 360. The wash water raw water tank 310 stores wash water from the washing unit 130 and recycled concentrated wash water. The second filtration device 320 filters the wash water output from the wash water raw water tank 310 and outputs a second filtrate and a second filter residue with an SS content ≤0.2 mg / L. The second filtrate is stored in a second filtrate storage tank, and the second filter residue is stored in a second filter residue storage tank. The second pH adjustment tank 330 adjusts the pH of the second filtrate output from the second filtrate storage tank and outputs a third filtrate with a pH of 6-7. The second feeding device 340 adds an acidic reagent to the second pH adjustment tank 330. The second filter press 350 filters the second filter residue in the second filter residue storage tank. The ultrafiltration device 360 ​​is used to perform ultrafiltration treatment on the third filtrate output from the second pH adjustment tank 330 and output cleaning water and concentrated washing water. The cleaning water is stored in the first mixed liquid storage tank 710; the concentrated washing water is stored in the washing water raw water tank 310.

[0085] The first concentration unit includes a first reverse osmosis unit 410 and a second reverse osmosis unit 420. The first reverse osmosis unit 410 is used to concentrate the first mixed liquor output from the first mixed liquor storage tank 710 and output a first intermediate concentrate and a first intermediate permeate. The second reverse osmosis unit 420 is used to concentrate the first intermediate concentrate and output a first concentrate and a second intermediate permeate. The first concentrate is stored in the second mixed liquor storage tank 720, and the first intermediate permeate and the second intermediate permeate constitute the first permeate and are stored in an intermediate tank 730.

[0086] The evaporation crystallization unit includes an evaporation crystallization device 510, a drying device 520, and a heat exchange device 530. The evaporation crystallization device 510 is used to evaporate and crystallize the second mixture output from the second mixed liquid storage tank 720, and output crystal water and crystal salt. The drying device 520 is used to dry the crystal salt and output ammonium chloride salt. The heat exchange device 530 is used to exchange heat with the crystal water and output condensate, which is stored in the first mixed liquid storage tank 710.

[0087] The second concentration unit includes a third reverse osmosis unit 610 and a fourth reverse osmosis unit 620. The third reverse osmosis unit 610 is used to perform reverse osmosis concentration treatment on the intermediate liquid composed of the first permeate and the returned second concentrate, and outputs a second intermediate concentrate and a third intermediate permeate. The second intermediate concentrate is returned to the first mixed liquid storage tank 710 to mix with cleaning water and condensate to form a first mixed liquid. The fourth reverse osmosis unit 620 is used to perform reverse osmosis concentration treatment on the third intermediate permeate and outputs a second concentrate and a second permeate. The second concentrate is returned to the intermediate tank 730 to mix with the first permeate to form an intermediate liquid, and the second permeate is returned to the intermediate tank 730. Figure 1 The washing unit 130 in the cobalt carbonate production system shown is used to wash solid cobalt carbonate.

[0088] An embodiment of the cobalt carbonate production wastewater treatment method of the present invention uses the above-mentioned cobalt carbonate production wastewater treatment system. The mother liquor has a TDS content of 75,000–95,000 mg / L, an SS content of 25–35 mg / L, and a pH of 8.5–9.5. The wash water has a TDS content of 500–1,500 mg / L, an SS content of 5–15 mg / L, and a pH of 7–8. The treatment system specifically includes steps Step 10–Step 50, as follows:

[0089] Step 10 involves pretreating the mother liquor using a mother liquor pretreatment unit to reduce its suspended solids (SS) content and pH, resulting in a clear mother liquor. Step 10 specifically includes steps 11 and 12, as follows:

[0090] Step 11: The mother liquor is filtered using the first filtration device 220 to obtain the first filtrate with an SS content ≤ 0.2 mg / L;

[0091] Step 12: In the first pH adjustment tank 230, the pH of the first filtrate is adjusted using hydrochloric acid with a mass fraction of 31% to obtain a clear mother liquor with a pH of 7-8.

[0092] Step 20 involves pretreating the wash water using a pretreatment unit to reduce the suspended solids (SS) content and pH, resulting in clean water. Step 20 specifically includes steps 21-23, as follows:

[0093] Step 21: The washing water and the recirculated concentrated washing water are filtered using the second filtration device 320 to obtain a second filtrate with an SS content ≤0.2mg / L;

[0094] Step 22: In the second pH adjustment tank 330, the pH of the second filtrate is adjusted by using hydrochloric acid with a mass fraction of 31% to obtain a third filtrate with a pH of 6-7.

[0095] Step 23: The third filtrate is subjected to ultrafiltration using an ultrafiltration device 360 ​​to obtain washing water and concentrated washing water; the concentrated washing water is returned to Step 21 for pretreatment.

[0096] Step 30 involves concentrating the first mixture containing washing water, condensate, and a second intermediate concentrate using a first concentration unit to obtain a first concentrate with high TDS content and a first product water with low TDS content. The TDS content of the first mixture is 1000–1300 mg / L, and the pH is 5.5–6.5. Step 30 specifically includes steps Step 31 and Step 32, as follows:

[0097] Step 31: The first mixed solution is concentrated by reverse osmosis using the first reverse osmosis equipment 410 to obtain the first intermediate concentrate and the first intermediate permeate; the TDS content of the first intermediate concentrate is 3 to 6 times that of the first mixed solution.

[0098] Step 33: The first intermediate concentrate is concentrated by reverse osmosis using the second reverse osmosis equipment 420 to obtain the first concentrate and the second intermediate permeate; the TDS content of the first concentrate is 2 to 5 times that of the first intermediate concentrate; the first intermediate permeate and the second intermediate permeate constitute the first permeate.

[0099] Step 40 involves evaporating and crystallizing the second mixture containing the first concentrated water and the clear mother liquor using an evaporation crystallization unit to obtain condensate and ammonium chloride. The TDS content of the second mixture is 70,000–85,000 mg / L, and the pH is 7.5–8.5. Step 400 specifically includes steps 41–43, as follows:

[0100] Step 41: The second mixture is evaporated and crystallized using an evaporation crystallization device 510 to obtain water of crystallization and salt of crystallization.

[0101] Step 42: The crystalline salt is dried using a drying device 520 to obtain ammonium chloride salt;

[0102] Step 43: Heat exchange equipment 530 is used to treat the crystallization water to obtain condensate.

[0103] Step 50 involves concentrating the first product water using a second concentration unit to obtain a second concentrated water with high TDS content and a second product water with low TDS content. The second product water is then recycled to the washing process in cobalt carbonate production. Step 50 specifically includes steps Step 51 and Step 52, as follows:

[0104] Step 51: The intermediate liquid consisting of the first product water and the returned second concentrate is concentrated by reverse osmosis using the third reverse osmosis equipment 610 to obtain the second intermediate concentrate and the third intermediate product water; the second intermediate concentrate is returned to Step 30 for concentration treatment; the TDS content of the second intermediate concentrate is 4 to 7 times that of the intermediate liquid.

[0105] Step 52: The third intermediate permeate is concentrated using the fourth reverse osmosis unit 620 to obtain the second concentrate and the second permeate. The second concentrate is returned to Step 51 for further concentration. The TDS content of the second concentrate is 4 to 7 times that of the third intermediate permeate. The TDS content of the second permeate is ≤10 mg / L.

[0106] The following application examples illustrate the beneficial effects of the present invention.

[0107] A cobalt carbonate manufacturer produced mother liquor and wash water with the following concentrations: Mother liquor had a TDS of 84070 mg / L, SS of 30 mg / L, and a pH of 9; Wash water had a TDS of 1034.5 mg / L, SS of 10 mg / L, and a pH of 7.8. TDS (Total Dissolved Solids) refers to the total amount of solid matter dissolved in water, including inorganic salts (such as calcium, magnesium, sodium, potassium, bicarbonates, chlorides, sulfates, etc.) and small amounts of organic matter, usually expressed in milligrams per liter (mg / L). SS (Suspended Solids) refers to solid particles suspended in water, including organic matter, inorganic matter, microorganisms, etc., usually expressed in milligrams per liter (mg / L). In addition, both the mother liquor and wash water contained significant amounts of NH4+. + Mg 2+ and Cl - .

[0108] The mother liquor was pretreated using a mother liquor pretreatment unit, and the water quality parameters of each water sample are shown in Table 1.

[0109] As can be seen from Table 1, after pretreatment, the SS content of the obtained mother liquor was only 0.1 mg / L.

[0110] Table 1

[0111]

[0112] The wash water was treated using a pretreatment unit, and the water quality parameters of each water sample are shown in Table 2.

[0113] As can be seen from Table 2, after pretreatment, the SS content of the obtained cleaning water is only 0.1 mg / L.

[0114] Table 2

[0115]

[0116] The first concentration unit was used to concentrate the first mixture containing washing water, condensate (obtained by cooling the crystal water to 35°C through a heat exchanger), and the second intermediate concentrate. The water quality parameters of each water sample are shown in Table 3.

[0117] As shown in Table 3, by controlling the concentration ratios of the first reverse osmosis unit 410 and the second reverse osmosis unit 420, the TDS content of the first intermediate concentrate is 3 to 6 times that of the first mixed liquor, and the TDS content of the first concentrate is 2 to 5 times that of the first intermediate concentrate. Ultimately, TDS is enriched in the first concentrate, reaching a TDS content as high as 22157.7 mg / L, which is 18.2 times that of the first mixed liquor, while the flow rate is as low as 29.6 m³ / L. 3 / day, thus significantly reducing the energy consumption of the subsequent evaporation and crystallization equipment 510.

[0118] Table 3

[0119]

[0120] Then, the second mixture consisting of the first concentrated water and the clear mother liquor was treated using an evaporation crystallization unit. The water quality parameters of each water sample are shown in Table 4.

[0121] Table 4

[0122]

[0123] Then, the intermediate liquid consisting of the first product water (including the first intermediate product water and the second intermediate product water) and the refluxed second concentrate water is treated by the second concentration unit. The water quality parameters of each water sample are shown in Table 5.

[0124] As shown in Table 5, by controlling the concentration ratios of the third reverse osmosis unit 610 and the fourth reverse osmosis unit 620, the TDS content of the second intermediate concentrate is 4 to 7 times that of the intermediate liquid, and the TDS content of the second concentrate is 4 to 7 times that of the third intermediate permeate. Ultimately, the TDS content of the second permeate is reduced to as low as 3.4 mg / L, and the daily permeate flow rate is 466 m³.3 When used in the washing process of cobalt carbonate production, the water used per day not only significantly saves on new water resources but also does not introduce impurities that affect the purity of cobalt carbonate.

[0125] Table 5

[0126]

[0127] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for treating wastewater from cobalt carbonate production, wherein cobalt carbonate production includes a precipitation reaction process, a solid-liquid separation process, and a washing process, and the production wastewater includes mother liquor and wash water, wherein the mother liquor originates from the solid-liquid separation process, and the wash water originates from the washing process, characterized in that: The processing method includes the following steps: Step 10: Pre-treat the mother liquor to reduce the SS content and pH of the mother liquor, and obtain a clear mother liquor; Step 20: Pre-treat the wash water to reduce the SS content and pH of the wash water to obtain cleaning water; Step 30: The first mixture containing washing water and condensate is concentrated to obtain a first concentrate with high TDS content and a first product water with low TDS content. Step 40: The second mixture containing the first concentrated water and the clear mother liquor is subjected to evaporation and crystallization treatment to obtain condensate and ammonium chloride. Step 50: The first product water is concentrated to obtain a second concentrated water with high TDS content and a second product water with low TDS content; the second product water is returned to the washing process in the cobalt carbonate production. The second concentrate reflux treatment; Step 30 specifically includes: Step 31: The first mixture is subjected to reverse osmosis concentration treatment to obtain a first intermediate concentrate and a first intermediate permeate; the TDS content of the first intermediate concentrate is 3 to 6 times that of the first mixture. Step 32: The first intermediate concentrate is concentrated by reverse osmosis to obtain the first concentrate and the second intermediate permeate; the TDS content of the first concentrate is 2 to 5 times that of the first intermediate concentrate; the first intermediate permeate and the second intermediate permeate constitute the first permeate. Step 50 specifically includes: Step 51: The intermediate liquid consisting of the first permeate and the refluxed second concentrate is subjected to reverse osmosis concentration treatment to obtain the second intermediate concentrate and the third intermediate permeate; the second intermediate concentrate is refluxed to Step 30 for concentration treatment; the TDS content of the second intermediate concentrate is 4 to 7 times that of the intermediate liquid. Step 52: The third intermediate permeate is concentrated by reverse osmosis to obtain the second concentrate and the second permeate; the second concentrate is returned to Step 51 for further concentration; the TDS content of the second concentrate is 4 to 7 times that of the third intermediate permeate; the TDS content of the second permeate is ≤10 mg / L.

2. The method for treating cobalt carbonate production wastewater as described in claim 1, characterized in that: Step 10 specifically includes: Step 11: Filter the mother liquor to obtain the first filtrate with SS content ≤0.2mg / L; Step 12: Adjust the pH of the first filtrate to obtain a clear mother liquor with a pH of 7-8.

3. The method for treating cobalt carbonate production wastewater as described in claim 1, characterized in that: Step 20 specifically includes: Step 21: Filter the wash water and the recirculated concentrated wash water to obtain a second filtrate with an SS content ≤0.2mg / L; Step 22: Adjust the pH of the second filtrate to obtain a third filtrate with a pH of 6-7; Step 23: The third filtrate is subjected to ultrafiltration to obtain washing water and concentrated washing water; the concentrated washing water is returned to Step 21 for filtration.

4. The method for treating cobalt carbonate production wastewater as described in claim 1, characterized in that: Step 40 specifically includes: Step 41: Evaporate and crystallize the second mixture to obtain water of crystallization and crystalline salt; Step 42: Dry the crystalline salt to obtain ammonium chloride salt; Step 43: Heat exchange treatment is performed on the water of crystallization to obtain condensate.

5. The method for treating cobalt carbonate production wastewater as described in claim 1, characterized in that: The cobalt carbonate is obtained by reacting cobalt chloride, hydrochloric acid and ammonium bicarbonate. In Step 10 and Step 20, the pH is adjusted using hydrochloric acid with a mass fraction of 31%.

6. The method for treating cobalt carbonate production wastewater as described in claim 5, characterized in that: The mother liquor has a TDS content of 75,000–95,000 mg / L, an SS content of 25–35 mg / L, and a pH of 8.5–9.5; the wash water has a TDS content of 500–1,500 mg / L, an SS content of 5–15 mg / L, and a pH of 7–8.

7. The method for treating cobalt carbonate production wastewater as described in claim 6, characterized in that: The first mixture has a TDS content of 1000-1300 mg / L and a pH of 5.5-6.5; the second mixture has a TDS content of 70000-85000 mg / L and a pH of 7.5-8.

5.

8. A method for producing cobalt carbonate, comprising a precipitation reaction step, a solid-liquid separation step, and a washing step, characterized in that: It also includes the treatment of mother liquor from the solid-liquid separation process and wash water from the washing process using the cobalt carbonate production wastewater treatment method according to any one of claims 1-7.

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