WO2024192575A1 - 高cod镍钴锂镁废水的资源化方法及其应用 - Google Patents

高cod镍钴锂镁废水的资源化方法及其应用 Download PDF

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Publication number
WO2024192575A1
WO2024192575A1 PCT/CN2023/082233 CN2023082233W WO2024192575A1 WO 2024192575 A1 WO2024192575 A1 WO 2024192575A1 CN 2023082233 W CN2023082233 W CN 2023082233W WO 2024192575 A1 WO2024192575 A1 WO 2024192575A1
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magnesium
nickel
cobalt
lithium
liquid
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French (fr)
Inventor
彭小聪
张荣荣
刘勇奇
李长东
巩勤学
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Priority to CN202380009013.2A priority Critical patent/CN117083243B/zh
Priority to PCT/CN2023/082233 priority patent/WO2024192575A1/zh
Publication of WO2024192575A1 publication Critical patent/WO2024192575A1/zh
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/14—Magnesium hydroxide
    • C01F5/20—Magnesium hydroxide by precipitation from solutions of magnesium salts with ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/24—Treatment of water, waste water, or sewage by flotation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention belongs to the technical field of wastewater treatment and metal resource recycling, and specifically relates to a resource recovery method of high-COD nickel-cobalt-lithium-magnesium wastewater and its application.
  • lithium-ion batteries have been widely used due to their large energy storage, fast charge and discharge, long cycle life, and environmental friendliness.
  • Positive and negative electrode materials are the core key materials in lithium-ion batteries.
  • the lower limit of the energy density of lithium-ion batteries depends on the positive and negative electrode materials, and the positive and negative electrode materials account for 60% to 70% of the cost of lithium-ion batteries. Therefore, accelerating the research and development of positive and negative electrode materials and improving production processes will not only help improve the comprehensive performance of lithium-ion batteries, but may also significantly reduce the current high battery costs.
  • the wastewater is then evaporated and concentrated to obtain sodium sulfate and lithium sulfate.
  • This process relies on chemical precipitation to remove metals, and the loss of lithium is large, and the removal capacity is limited, which makes the back-end evaporation and concentration process have a high processing load, which increases the operating cost to a certain extent.
  • the current method of treating magnesium-containing wastewater containing heavy metals, high salinity and high COD uses sodium sulfide to remove nickel and cobalt, and some magnesium will be precipitated and re-enter the system; sodium sulfide is not only easy to cause environmental pollution, but also damages the health of workers in the working environment; sodium hydroxide is used to precipitate magnesium, and the amount of sodium hydroxide is large; the precipitation method also has the problem of high lithium loss. Therefore, there is an urgent need to develop a method for treating high COD nickel-cobalt-lithium-magnesium wastewater and realize resource utilization.
  • the present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a resource recovery method and application of high COD nickel-cobalt-lithium-magnesium wastewater, and prepares Surface-modified hexagonal magnesium hydroxide flame retardant, and nickel and cobalt are recovered by precipitation in the rear concentrated liquid to achieve efficient recovery and high-value utilization of metals in wastewater and waste residues.
  • a method for recycling high COD nickel-cobalt-lithium-magnesium wastewater comprising the following steps:
  • the COD content of the high COD nickel-cobalt-lithium-magnesium wastewater is 1000-1500 mg/L, the nickel metal content is 30-100 mg/L, the cobalt metal content is 15-100 mg/L, the lithium metal content is 0.5-10 g/L, and the magnesium metal content is 50-150 mg/L.
  • step S1 the deoiling process is: firstly, a high-pressure CO2 aqueous solution or a high-pressure CO2 liquid is introduced into the high-COD nickel-cobalt-lithium-magnesium wastewater for flotation deoiling, and then the wastewater after flotation deoiling is subjected to adsorption deoiling through a filling column to obtain the deoiled liquid.
  • the high-pressure CO2 aqueous solution is a saturated CO2 pressurized aqueous solution
  • the pressurization pressure is 0.5-7Mpa
  • the dosage of the high-pressure CO2 aqueous solution is 8-12% of the volume of the high-COD nickel-cobalt-lithium-magnesium wastewater.
  • the flotation deoiling time is 2-4h.
  • the use of a high-pressure CO2 aqueous solution for flotation deoiling can utilize the process characteristics of CO2 precipitation from the solution under reduced pressure to gasify or agglomerate and float the micro-emulsified oil substances in the wastewater, and the high-pressure carbon dioxide can be reused by the air compressor after deoiling adsorption treatment, thereby reducing the consumption of auxiliary materials in the production process.
  • the present invention combines high-pressure CO2 aqueous solution for flotation oil removal and packed column adsorption oil removal, which can effectively reduce the COD content in wastewater, reduce the pollution of oil substances to adsorption resins in subsequent work stages, and enhance process stability.
  • step S1 the CO 2 after the flotation oil removal is purified by air filtration, compressed at a pressure of 0.5-1 MPa and reused in the flotation oil removal process.
  • step S1 the oil removal filler of the filling column is activated carbon or vinyl-acrylonitrile copolymer gel-type oil removal resin.
  • step S1 the COD content in the high COD nickel-cobalt-lithium-magnesium wastewater after oil removal is 50-200 mg/L.
  • the hydrogen ion type resin is a polystyrene molecular skeleton chelating resin.
  • step S2 the adsorption conditions of the hydrogen ion resin are: the resin absorption tower is filled with a height-to-diameter ratio of (2-3): 1, a flow rate of 4-5 BV/h, and the solution is controlled at a pH of 5-8.
  • step S2 further includes: desorbing and regenerating the adsorbed hydrogen ion resin with acid to obtain a nickel-cobalt desorption solution.
  • the acid used is sulfuric acid with a mass concentration of 10%-20%, and the pH value is maintained at 3 during the pickling process.
  • the sodium ion type resin is a styrene-divinylbenzene copolymer sulfonyl resin, a styrene-divinylbenzene cross-linked aminophosphonic acid chelating resin or a polystyrene copolymer type I quaternary amine functional resin.
  • step S3 the adsorption conditions of the sodium ion resin are: the resin absorption tower is filled with a height-to-diameter ratio of (2-3): 1, a flow rate of 3-5 BV/h, and the solution is controlled at a pH of 7-9.
  • step S3 sulfuric acid with a mass concentration of 10%-20% is used for desorption, and the pickling flow rate is 2-4 BV/h.
  • step S3 after desorption, the sodium ion resin is regenerated with a 20 wt % -30 wt % sodium hydroxide solution at a flow rate of 2-5 BV/h for 1-2 h.
  • step S3 further includes: performing MVR concentration on the secondary adsorption liquid to obtain sodium sulphate and concentrated liquid, and using sodium carbonate to precipitate lithium in the concentrated liquid to obtain crude lithium carbonate.
  • the secondary adsorption liquid itself has a high salt content, and sodium sulphate can be obtained by evaporating and concentrating it to 1/5-1/3 of the original volume.
  • step S4 the concentration of magnesium ions in the magnesium salt desorption solution is 0.5-2.5 mol/L.
  • step S4 the ammonia gas is introduced to maintain the solution pH at 10-12.
  • the organic phosphine chelating agent is at least one of hexamethylenediaminetetramethylenephosphonic acid (HDTMPA), ethylenediaminetetramethylenephosphonic acid, hydroxyethylidene diphosphonic acid (HEDP), aminotrimethylenephosphonic acid, hexylphosphonic acid or dodecylphosphonic acid.
  • HDTMPA hexamethylenediaminetetramethylenephosphonic acid
  • HEDP hydroxyethylidene diphosphonic acid
  • aminotrimethylenephosphonic acid hexylphosphonic acid or dodecylphosphonic acid.
  • step S4 the amount of the organic phosphine chelating agent added is 1 wt%-5 wt% of the theoretical output of magnesium hydroxide.
  • step S4 the temperature of the magnesium precipitation reaction is 40-80°C.
  • step S4 the aging time is 2-6 hours.
  • the mass concentration of the dilute acid is 1%-5%. Further, the dilute acid is dilute hydrochloric acid.
  • step S4 further includes: evaporating and concentrating the filtrate after the solid-liquid separation, recycling the evaporated ammonia gas to the magnesium precipitation operation, adding alkali to the evaporated and concentrated solution to adjust the pH value for precipitation, and obtaining nickel-cobalt slag. Furthermore, the nickel-cobalt slag is acid-dissolved and then returned to the hydrogen ion resin in step S2 for adsorption, and a nickel-cobalt desorption solution is obtained after desorption, or returned to the front-end extraction process for purification to produce a refined nickel-cobalt solution.
  • the present invention also provides application of the hexagonal magnesium hydroxide solid prepared by the resource recovery method in flame retardant materials.
  • the wastewater after COD removal of the present invention is subjected to the combined adsorption of hydrogen ion resin and sodium ion resin in two stages, which can increase the content of Mg ions in the magnesium salt desorption solution and reduce the content of nickel, cobalt and manganese metals, which is conducive to the subsequent acquisition of a higher purity hexagonal magnesium hydroxide flame retardant solid, and the nickel cobalt salt solution obtained by desorption can be directly reused in the front-end extraction process for purification and production of refined nickel cobalt salt products.
  • the best experimental process is to first adsorb nickel and cobalt, and then adsorb magnesium to achieve the separation of nickel, cobalt and magnesium.
  • nickel and cobalt Since the resin on the market that adsorbs nickel and cobalt has stronger selectivity, magnesium will only be entrained in small amounts due to the concentration difference between nickel, cobalt and magnesium, which does not affect the adsorption capacity of nickel and cobalt; if magnesium in the wastewater is adsorbed first, and then nickel and cobalt are adsorbed, on the one hand, when magnesium is adsorbed, nickel and cobalt will be adsorbed together, affecting the adsorption effect of the resin on magnesium, and on the other hand, increasing the loss of nickel and cobalt.
  • the present invention uses a special selective resin to adsorb nickel, cobalt and magnesium in stages, which can achieve short-range and efficient recycling.
  • the nickel, cobalt and lithium in the wastewater are collected, and the adsorption capacity of the two resins for Li ions is low.
  • the lithium in the liquid can be concentrated to produce sodium sulfate as a by-product, and the concentrated mother liquor is precipitated to obtain crude lithium carbonate, and the comprehensive recovery rate can reach 98%.
  • Organic phosphine chelating agents can chelate with Ni, Co, Ca, and Fe metal ions in the magnesium salt desorption solution. Under the alkaline conditions of ammonia, they will not precipitate or be sandwiched in the magnesium hydroxide precipitate.
  • the chelating agent has multiple phosphate groups, and its molecular chain can be preferentially adsorbed on the (001) and (101) crystal planes of magnesium hydroxide, and the (001) and (101) crystal planes are the main exposed surfaces of the regular hexagonal flakes. Therefore, the chelating agent has the function of regulating the growth direction of the magnesium hydroxide crystal form, and a hexagonal crystal structure suitable for flame retardants can be obtained.
  • the chelating agent can also be grafted onto the surface of the generated hexagonal magnesium hydroxide solid to modify it.
  • the carbon chain of the modified hexagonal magnesium hydroxide solid increases, and the thermal stability and flame retardant properties are improved. It can also improve the surface adhesion between magnesium hydroxide and the flame retardant matrix material and solve the problem of poor compatibility between the two, reaching the standard that can be added to the polymer for flame retardancy.
  • the precipitate obtained after the magnesium precipitation reaction is washed with dilute acid to remove the complex impurity metal ions on the surface and make the phosphate groups grafted on the surface become P(OH). If it is not washed with dilute acid, it may become P-O-M, which is not conducive to the flame retardancy of magnesium hydroxide.
  • the use of low-concentration dilute acid has less impact on the magnesium hydroxide solid.
  • FIG1 is a process flow chart of Example 1 of the present invention.
  • FIG2 is a schematic diagram of the principle of magnesium hydroxide surface modified by hexamethylenediaminetetramethylenephosphonic acid (HDTMPA) of the present invention
  • FIG3 is a SEM image of surface-modified hexagonal magnesium hydroxide with different addition amounts (1%, 3%, 5%) of hexamethylenediaminetetramethylenephosphonic acid (HDTMPA) of the present invention
  • FIG4 is a SEM image of magnesium hydroxide prepared by direct precipitation without using a chelating agent in Comparative Example 2 of the present invention.
  • FIG5 is the DSC curves of magnesium hydroxide before (a) and after (b) modification.
  • a resource recovery method for high COD nickel-cobalt-lithium-magnesium wastewater referring to FIG1, the specific process is as follows:
  • Step (1) after the high COD nickel-cobalt-lithium-magnesium wastewater is allowed to stand, a 0.5MPa CO2 aqueous solution is introduced to perform flotation oil removal operation for 4 hours, wherein the amount of the high-pressure CO2 aqueous solution is 10% of the volume of the high COD nickel-cobalt-lithium-magnesium wastewater, and the COD content of the high COD nickel-cobalt-lithium-magnesium wastewater is 1500mg/L, the nickel metal content is 100mg/L, the cobalt metal content is 35mg/L, the lithium metal content is 10g/L, and the magnesium metal content is 150mg/L;
  • Step (2) the wastewater after flotation oil removal is passed through an activated carbon column for adsorption oil removal again, and the COD of the solution can be reduced to 150 mg/L;
  • Step (3) using a polystyrene molecular skeleton chelating resin (hydrogen ion resin D463 resin of Xi'an Lanxiao Technology Co., Ltd.) to adsorb Ni and Co metal ions on the wastewater obtained in step (2); the resin absorption tower is filled with a height-to-diameter ratio of 2:1, the flow rate is 4BV/h, the solution is controlled to have a pH of 5, and a post-adsorption liquid is obtained after the adsorption operation; using 10% sulfuric acid to desorb and regenerate the polystyrene molecular skeleton chelating resin, and the pH is maintained at 3 during the pickling process to obtain a nickel-cobalt sulfate desorption solution containing 2.4 g/L nickel, 0.9 g/L cobalt, and 0.1 g/L magnesium;
  • a polystyrene molecular skeleton chelating resin hydrogen ion resin D463 resin of Xi'an Lanxiao Technology
  • Step (4) passing the primary adsorption liquid obtained in step (3) into a styrene-divinylbenzene cross-linked aminophosphonic acid chelating resin (Xi'an Lanxiao Technology Co., Ltd. aminophosphonic acid chelating resin LSC-850) for Mg metal ion adsorption, wherein the operating conditions are a resin absorption tower filling height-to-diameter ratio of 3:1, a flow rate of 5 BV/h, and a solution pH controlled at 9, to obtain a secondary adsorption liquid after the operation; the secondary adsorption liquid is subjected to MVR concentration and crystallization to obtain sodium sulfate, and the concentrated mother liquor is subjected to lithium precipitation operation using sodium carbonate to obtain crude lithium carbonate;
  • Step (5) using 10% sulfuric acid at a flow rate of 2 BV/h to desorb the saturated styrene-divinylbenzene copolymer sulfonyl resin in step (4) to obtain a magnesium sulfate desorption solution; then using a 20% sodium hydroxide solution at a flow rate of 5 BV/h to regenerate the styrene-divinylbenzene copolymer sulfonyl resin for 2 hours;
  • Step (6) adding a chelating agent HDTMPA, introducing ammonia gas to the magnesium salt desorption solution to carry out a magnesium precipitation reaction, wherein the concentration of the magnesium salt desorption solution is 0.5 mol/L, and ammonia gas is introduced to maintain the solution pH at 10.
  • the amount of chelating agent added is 1% of the theoretical yield of magnesium hydroxide, the reaction temperature is 40° C., and the precipitation aging reaction time is 2 h; after aging and filtering, washing with water and then washing with 1% dilute hydrochloric acid, and finally washing with water, and drying to obtain a hexagonal magnesium hydroxide solid;
  • Step (7) after filtering the magnesium precipitate in step (6), the filtrate obtained is evaporated and concentrated, the evaporated ammonia is recycled to step (6), and soda ash is added to the concentrated mother liquor for value adjustment and precipitation to obtain nickel-cobalt slag; the nickel-cobalt slag is dissolved with low acid to obtain an acid solution which is returned to step (3) for nickel-cobalt metal adsorption and desorption operations for recovery.
  • a resource recovery method for high COD nickel-cobalt-lithium-magnesium wastewater, the specific process is:
  • Step (1) after the high COD nickel-cobalt-lithium-magnesium wastewater is allowed to stand, a 3MPa CO2 aqueous solution is introduced to perform flotation oil removal operation for 3 hours, wherein the amount of the high-pressure CO2 aqueous solution is 8% of the volume of the high COD nickel-cobalt-lithium-magnesium wastewater, and the COD content of the high COD nickel-cobalt-lithium-magnesium wastewater is 1300 mg/L, the nickel metal content is 50 mg/L, the cobalt metal content is 25 mg/L, the lithium metal content is 5 g/L, and the magnesium metal content is 100 mg/L;
  • Step (2) the wastewater after flotation oil removal is passed through an activated carbon column for adsorption oil removal again, and the COD of the solution can be reduced to 100 mg/L;
  • Step (3) using a polystyrene molecular skeleton chelating resin to adsorb Ni and Co metal ions on the wastewater obtained in step (2); the resin absorption tower is filled with a height-to-diameter ratio of 2.5:1, the flow rate is 4.5 BV/h, the solution pH is controlled at 7, and a primary adsorption liquid is obtained after the adsorption operation; using 15% sulfuric acid to desorb and regenerate the polystyrene molecular skeleton chelating resin, and the pH is maintained at 3 during the pickling process to obtain a nickel-cobalt sulfate desorption solution containing 2.6 g/L nickel, 1.2 g/L cobalt, and 0.15 g/L magnesium;
  • Step (4) passing the primary adsorption liquid obtained in step (3) into a styrene-divinylbenzene copolymer sulfonyl resin for Mg metal ion adsorption, the operating conditions being that the resin absorption tower is filled with a height-to-diameter ratio of 2.5:1, the flow rate is 4BV/h, and the solution is controlled at pH 8, and a secondary adsorption liquid is obtained after the operation; the secondary adsorption liquid is subjected to MVR concentration and crystallization to obtain sodium sulfate, and the concentrated mother liquor is subjected to lithium precipitation operation using sodium carbonate to obtain crude lithium carbonate;
  • Step (5) using 10% sulfuric acid at a flow rate of 2 BV/h to desorb the saturated styrene-divinylbenzene copolymer sulfonyl resin in step (4) to obtain a magnesium sulfate desorption solution; then using a 20% sodium hydroxide solution at a flow rate of 5 BV/h to regenerate the styrene-divinylbenzene copolymer sulfonyl resin for 2 hours;
  • Step (6) adding a chelating agent HDTMPA, introducing ammonia gas to the magnesium salt desorption solution to carry out a magnesium precipitation reaction, wherein the concentration of the magnesium salt desorption solution is 1.5 mol/L, and ammonia gas is introduced to maintain the solution pH at 11.
  • the amount of chelating agent added is 3% of the theoretical yield of magnesium hydroxide, the reaction temperature is 60° C., and the precipitation aging reaction time is 4 h; after aging and filtering, washing with water and then washing with 3% dilute hydrochloric acid, and finally washing with water, and drying to obtain a hexagonal magnesium hydroxide solid;
  • Step (7) after filtering the magnesium precipitate in step (6), the filtrate obtained is evaporated and concentrated, the evaporated ammonia is recycled to step (6), and soda ash is added to the concentrated mother liquor for value adjustment and precipitation to obtain nickel-cobalt slag; the nickel-cobalt slag is dissolved with low acid to obtain an acid solution which is returned to step (3) for nickel-cobalt metal adsorption and desorption operations for recovery.
  • a resource recovery method for high COD nickel-cobalt-lithium-magnesium wastewater, the specific process is:
  • Step (1) after the high COD nickel-cobalt-lithium-magnesium wastewater is allowed to stand, a 7MPa CO2 aqueous solution is introduced to perform flotation oil removal operation for 2 hours, wherein the amount of the high-pressure CO2 aqueous solution is 10% of the volume of the high COD nickel-cobalt-lithium-magnesium wastewater, and the COD content of the high COD nickel-cobalt-lithium-magnesium wastewater is 1000 mg/L, the nickel metal content is 30 mg/L, the cobalt metal content is 15 mg/L, the lithium metal content is 0.5 g/L, and the magnesium metal content is 50 mg/L;
  • Step (2) the wastewater after flotation oil removal is passed through an activated carbon column for adsorption oil removal again, and the COD of the solution can be reduced to 50 mg/L;
  • Step (3) using a polystyrene molecular skeleton chelating resin to adsorb Ni and Co metal ions on the wastewater obtained in step (2); the resin absorption tower is filled with a height-to-diameter ratio of 3:1, the flow rate is 5 BV/h, the solution is controlled to have a pH of 8, and a primary adsorption liquid is obtained after the adsorption operation; using 20% sulfuric acid to desorb and regenerate the polystyrene molecular skeleton chelating resin, and the pH is maintained at >3 during the pickling process to obtain a nickel-cobalt sulfate desorption liquid containing 2.8 g/L nickel, 1.3 g/L cobalt, and 0.25 g/L magnesium;
  • Step (4) passing the primary adsorption liquid obtained in step (3) into a styrene-divinylbenzene copolymer sulfonyl resin for Mg metal ion adsorption, the operating conditions being that the resin absorption tower is filled with a height-to-diameter ratio of 2:1, the flow rate is 3BV/h, and the solution is controlled at a pH of 7, to obtain a secondary adsorption liquid after the operation; the secondary adsorption liquid is subjected to MVR concentration and crystallization to obtain sodium sulfate, and the concentrated mother liquor is subjected to lithium precipitation operation using sodium carbonate to obtain crude lithium carbonate;
  • Step (5) using 10% sulfuric acid at a flow rate of 2 BV/h to desorb the saturated styrene-divinylbenzene copolymer sulfonyl resin in step (4) to obtain a magnesium sulfate desorption solution; then using a 20% sodium hydroxide solution at a flow rate of 5 BV/h to regenerate the styrene-divinylbenzene copolymer sulfonyl resin for 2 hours;
  • Step (6) adding a chelating agent HDTMPA, introducing ammonia gas to the magnesium salt desorption solution to carry out a magnesium precipitation reaction, wherein the concentration of the magnesium salt desorption solution is 2.5 mol/L, and the pH value of the solution is maintained at 12 by introducing ammonia gas.
  • the amount of the chelating agent added is 5% of the theoretical yield of magnesium hydroxide, the reaction temperature is 80° C., and the precipitation aging reaction time is 6 h; after aging and filtering, washing with water and then washing with 5% dilute hydrochloric acid, and finally washing with water, and drying to obtain a hexagonal magnesium hydroxide solid;
  • Step (7) after filtering the magnesium precipitate in step (6), the filtrate obtained is evaporated and concentrated, the evaporated ammonia is recycled to step (6), and soda ash is added to the concentrated mother liquor for value adjustment and precipitation to obtain nickel-cobalt slag; the nickel-cobalt slag is dissolved with low acid to obtain an acid solution which is returned to step (3) for nickel-cobalt metal adsorption and desorption operations for recovery.
  • a method for recycling high COD nickel-cobalt-lithium-magnesium wastewater which differs from Example 1 in that magnesium is adsorbed first and then nickel-cobalt is adsorbed.
  • the specific process is as follows:
  • Steps (1) and (2) are the same as in Example 1;
  • Step (3) passing the wastewater obtained in step (2) into a styrene-divinylbenzene cross-linked aminophosphonic acid chelating resin to adsorb Mg metal ions.
  • the operating conditions are as follows: a resin absorption tower is filled with a height-to-diameter ratio of 3:1, a flow rate of 5 BV/h, and the solution is controlled to have a pH of 9. After the operation, a primary adsorption liquid is obtained;
  • Step (4) passing the primary adsorption liquid obtained in step (3) into a polystyrene molecular skeleton chelating resin to adsorb Ni and Co metal ions, the resin absorption tower is filled with a height-to-diameter ratio of 2:1, the flow rate is 4BV/h, the solution is controlled to have a pH of 5, and a secondary adsorption liquid is obtained after the operation; using 10% sulfuric acid to desorb and regenerate the polystyrene molecular skeleton chelating resin, and the pH is maintained at >3 during the pickling process to obtain a nickel-cobalt sulfate desorption liquid containing 2.1 g/L nickel, 0.5 g/L cobalt, and 0.05 g/L magnesium;
  • Step (5) using 10% sulfuric acid at a flow rate of 2 BV/h to desorb the saturated styrene-divinylbenzene cross-linked aminophosphonic acid chelating resin in step (3) to obtain a magnesium sulfate desorption solution; then using a 20% sodium hydroxide solution at a flow rate of 5 BV/h to regenerate the styrene-divinylbenzene copolymer sulfonyl resin for 2 hours;
  • Step (6) The secondary adsorption liquid obtained in step (4) is subjected to MVR concentration and crystallization to obtain sodium sulphate.
  • the concentrated mother liquor is subjected to lithium precipitation operation using sodium carbonate to obtain crude lithium carbonate.
  • Steps (1) to (5) are the same as those in Example 3.
  • Step (6) without adding a chelating agent, ammonia gas was directly introduced into the magnesium salt solution to precipitate magnesium, the concentration of the magnesium salt solution was 2.5 mol/L, ammonia gas was introduced to maintain the solution pH at 12, the reaction temperature was 80°C, and the precipitation aging reaction time was 6 hours; the aging process After filtration, the product was washed with water and dried to obtain hexagonal magnesium hydroxide solid.
  • the element content wt% refers to the ratio of each metal element to the total metal elements in the magnesium sulfate desorption solution.
  • the Mg content in the magnesium sulfate desorption solution of Comparative Example 1 is significantly reduced, while the nickel and cobalt elements are increased. This is because the styrene-divinylbenzene copolymer sulfonyl resin is not selective enough for magnesium. When adsorbing magnesium, part of the nickel and cobalt will be adsorbed together, affecting the adsorption effect of the resin on magnesium. In Example 1, nickel and cobalt are first adsorbed, and then magnesium is adsorbed. The polystyrene molecular skeleton chelating resin has a stronger selectivity for nickel and cobalt, and only a small amount of magnesium is entrained, which does not affect the adsorption capacity of nickel and cobalt.
  • the impurity elements in the magnesium hydroxide solid prepared in Comparative Example 2 are significantly more than those in Example 3. This is because after the chelating agent is added to Example 3, the chelating agent can ionize the Ni, Co, Ca, and Fe metals in the magnesium sulfate desorption solution. The chelating agent is chelated and basically will not precipitate or be sandwiched in the magnesium hydroxide precipitate, thereby improving the purity of the magnesium hydroxide.
  • the specific surface area of Comparative Example 2 is also significantly higher than that of Example 3, indicating that the magnesium hydroxide crystals generated without the use of a chelating agent have obvious defects and the crystal form is incomplete.
  • the recovery rate of nickel, cobalt and magnesium in Comparative Example 1 is significantly reduced, because the specific selectivity of styrene-divinylbenzene cross-linked aminophosphonic acid chelating resin to magnesium is not strong enough.
  • part of nickel and cobalt will be adsorbed together, affecting the adsorption effect of the resin on magnesium.
  • Example 1 first adsorbs nickel and cobalt, and then adsorbs magnesium.
  • the specific selectivity of the polystyrene molecular skeleton chelating resin to nickel and cobalt is stronger, and only a small amount of magnesium is entrained, which does not affect the adsorption capacity of nickel and cobalt.
  • the recovery rate of nickel, cobalt, lithium and magnesium in Comparative Example 2 is not much different from that in Example 3, because the chelating agent added in Example 3 does not affect the recovery rate of magnesium, but only affects the hexagonal magnesium hydroxide crystal form.
  • the use of a special selective resin for segmented adsorption of nickel, cobalt and magnesium combined process can increase the recovery rate of nickel, cobalt, lithium and magnesium.
  • FIG 3 is an SEM image of hexagonal magnesium hydroxide surface-modified with hexamethylenediaminetetramethylenephosphonic acid (HDTMPA) in different addition amounts (1%, 3%, and 5%);
  • Figure 4 is an SEM image of magnesium hydroxide prepared by direct precipitation without the use of a chelating agent in Comparative Example 2. It can be seen from the figure that the hexagonal magnesium hydroxide prepared under the conditions of adding 1%, 3%, and 5% HDTMPA respectively is significantly different from that without the addition of a chelating agent. The crystal morphology generated without the use of a chelating agent is different, the crystals are staggered and overlapped, the agglomeration is serious, and the crystals have obvious defects.
  • HDTMPA hexamethylenediaminetetramethylenephosphonic acid
  • the resulting crystal form is more complete, the arrangement is more orderly, and the agglomeration is improved.
  • a smaller amount of HDTMPA (1%) is added, the crystal form still has irregular, agglomerated flakes, which is due to insufficient chelating agent molecular chains.
  • more HDTMPA (5%) is added, the excessively long molecular chains may cause the hexagonal flakes to entangle with each other during the growth process. Adding an appropriate amount of HDTMPA (3%) can obtain more successfully modified hexagonal flakes. Square magnesium hydroxide.
  • Figure 5 is a DSC curve of magnesium hydroxide before (a) and after (b) modification corresponding to Example 3 and Comparative Example 2.
  • the carbon chain increases, the thermal stability and flame retardancy are improved, the heat absorption of the modified magnesium hydroxide increases, and the endothermic enthalpy increases. Due to the grafting of the chelating agent HDTMPA, the pyrolysis temperature increases.

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Abstract

一种高COD镍钴锂镁废水的资源化方法及其应用，包括对高COD镍钴锂镁废水进行除油处理，用氢离子型树脂对除油后液中的Ni、Co离子进行吸附，用钠离子型树脂对一次吸附后液中的Mg离子进行吸附，再用酸对吸附后的钠离子型树脂进行解吸处理，得到镁盐解吸液，在镁盐解吸液中加入有机膦类螯合剂、并通入氨气进行沉镁反应，沉淀物用水和稀酸洗涤，得到六方型氢氧化镁固体。除COD后的废水经过氢离子型树脂和钠离子型树脂两段树脂联合吸附作用，有利于后续得到纯度更高的六方型氢氧化镁阻燃剂固体，螯合剂可以接枝到生成的六方型氢氧化镁固体表面对其进行改性，改性后的六方型氢氧化镁固体的热稳定性和阻燃性能得到改善。

Description

高COD镍钴锂镁废水的资源化方法及其应用 技术领域
本发明属于废水处理及金属资源回收利用技术领域，具体涉及一种高COD镍钴锂镁废水的资源化方法及其应用。
背景技术
伴随着中国新能源行业的快速发展，锂离子电池因其具备储存能量大、可快速充放电、循环寿命长、环境友好等特点得到了广泛应用，正负极材料是锂离子电池中的核心关键材料，锂离子电池的能量密度下限取决于正负极材料，并且正负极材料占锂离子电池成本的60％～70％。因此加快正负极材料的研发和改进生产工艺，不仅有利于提高锂离子电池的综合性能，同时还可能显著降低目前过高的电池成本。
三元正极材料湿法冶炼过程中，萃取分离提纯硫酸镍钴锰的精制过程中，会有大量高COD含镍钴锂镁废水产生，由于镍钴、锂的高经济属性，该类废水具有很高的回收价值，目前采用的工艺为活性炭除油后、使用硫化钠除去镍钴锰金属，得到的滤渣返回浸出工序，向得到的含锂镁硫酸钠溶液中加入氢氧化钠得到氢氧化镁，压滤后形成固废和废液，废水再经过蒸发浓缩，得到硫酸钠、硫酸锂。该工艺靠化学沉淀法来去除金属，锂的损失较大，去除能力有限，使得后端蒸发浓缩工艺处理负荷较高，在一定程度上增加了运营成本。由此可见，目前处理含重金属、盐度高、COD偏高的含镁废水的方法，使用硫化钠除镍钴的同时，会有部分镁被沉淀并再次进入系统；硫化钠不仅容易造成环境污染，还会损害作业环境中工人的健康；使用氢氧化钠回调沉镁，氢氧化钠的用量较多；沉淀法还存在锂损失较高的问题。因此，急需研发一种处理高COD含镍钴锂镁废水的方法并实现资源化利用。
发明内容
本发明旨在至少解决上述现有技术中存在的技术问题之一。为此，本发明提出一种高COD镍钴锂镁废水的资源化方法及其应用，在处理高COD镍钴锂镁废水的同时制备 表面改性的六方型氢氧化镁阻燃剂，并在后端浓缩液中沉淀回收镍钴，实现废水废渣中金属的高效回收和高值化利用。
根据本发明的一个方面，提出了一种高COD镍钴锂镁废水的资源化方法，包括以下步骤：
S1：对高COD镍钴锂镁废水进行除油处理，得到除油后液；
S2：用氢离子型树脂对所述除油后液中的Ni、Co离子进行吸附，得到一次吸附后液；
S3：用钠离子型树脂对所述一次吸附后液中的Mg离子进行吸附，得到二次吸附后液，再用酸对吸附后的钠离子型树脂进行解吸处理，得到镁盐解吸液；
S4：在所述镁盐解吸液中加入有机膦类螯合剂、并通入氨气进行沉镁反应，陈化后固液分离，所得沉淀物用水和稀酸洗涤，得到六方型氢氧化镁固体。
在本发明的一些实施方式中，步骤S1中，所述高COD镍钴锂镁废水中COD含量为1000-1500mg/L，镍金属含量为30-100mg/L，钴金属含量为15-100mg/L，锂金属含量为0.5-10g/L，镁金属含量为50-150mg/L。
在本发明的一些实施方式中，步骤S1中，所述除油的过程为：先向所述高COD镍钴锂镁废水中通入高压CO2水溶液或高压CO2液体进行气浮除油，再将气浮除油后的废水经过填充柱进行吸附除油，得到所述除油后液。进一步地，所述高压CO2水溶液为饱和的CO2加压水溶液，加压压力为0.5-7Mpa，高压CO2水溶液的用量为高COD镍钴锂镁废水体积的8-12％。进一步地，所述气浮除油的时间为2-4h。使用高压CO2水溶液进行气浮除油，可以利用CO2在减压下从溶液中析出的过程特征，气化或者使废水中呈微乳化状的油类物质团聚上浮，且高压二氧化碳经除油吸附处理后，可以再利用空气压缩机重复利用，降低生产过程中的辅料消耗。本发明联用高压CO2水溶液进行气浮除油和填充柱吸附除油，可以有效降低废水中COD含量，减少油类物质对后续工段吸附树脂的污染，增强工艺稳定性。
在本发明的一些实施方式中，步骤S1中，经所述气浮除油后的CO2通过空气过滤净化，在0.5-1Mpa的压力下压缩回用至气浮除油工序。
在本发明的一些实施方式中，步骤S1中，所述填充柱的除油填充物为活性炭或乙烯基-丙烯氰共聚物凝胶型除油树脂。
在本发明的一些实施方式中，步骤S1中，经所述除油后高COD镍钴锂镁废水中COD含量为50-200mg/L。
在本发明的一些实施方式中，步骤S2中，所述氢离子型树脂为聚苯乙烯分子骨架螯合树脂。
在本发明的一些实施方式中，步骤S2中，所述氢离子型树脂的吸附条件为：树脂吸收塔装填高径比(2-3)：1，流速4-5BV/h，溶液控制pH为5-8。
在本发明的一些实施方式中，步骤S2中，还包括：用酸对吸附后的氢离子型树脂进行解吸再生处理，得到镍钴解吸液。进一步地，所用酸为质量浓度10％-20％的硫酸，酸洗过程保持pH＞3。
在本发明的一些实施方式中，步骤S3中，所述钠离子型树脂为苯乙烯-二乙烯苯共聚磺酰基树脂、苯乙烯-二乙烯苯交联氨基膦酸螯合树脂或聚苯乙烯共聚I型季胺官能基树脂。
在本发明的一些实施方式中，步骤S3中，所述钠离子型树脂的吸附条件为：树脂吸收塔装填高径比(2-3)：1，流速3-5BV/h，溶液控制pH为7-9。
在本发明的一些实施方式中，步骤S3中，采用质量浓度10％-20％的硫酸进行解吸，酸洗流量为2-4BV/h。
在本发明的一些实施方式中，步骤S3中，所述钠离子型树脂经解吸后，用流量2-5BV/h的20wt％-30wt％氢氧化钠溶液进行再生1-2h。
在本发明的一些实施方式中，步骤S3中，还包括：对所述二次吸附后液进行MVR浓缩得到元明粉和浓缩后液，所述浓缩后液用碳酸钠进行沉锂得到粗碳酸锂。二次吸附后液本身盐分较高，通过蒸发浓缩至原体积的1/5-1/3后可得到元明粉。
在本发明的一些实施方式中，步骤S4中，所述镁盐解吸液中镁离子的浓度为0.5-2.5mol/L。
在本发明的一些实施方式中，步骤S4中，通入所述氨气保持溶液pH为10-12。
在本发明的一些实施方式中，步骤S4中，所述有机膦类螯合剂为己二胺四甲叉膦酸(HDTMPA)、乙二胺四亚甲基膦酸、羟基乙叉二膦酸(HEDP)、氨基三亚甲基膦酸、己基膦酸或十二烷基膦酸中的至少一种。
在本发明的一些实施方式中，步骤S4中，所述有机膦类螯合剂的添加量为氢氧化镁理论产量的1wt％-5wt％。
在本发明的一些实施方式中，步骤S4中，所述沉镁反应的温度为40-80℃。
在本发明的一些实施方式中，步骤S4中，所述陈化的时间为2-6h。
在本发明的一些实施方式中，步骤S4中，所述稀酸的质量浓度为1％-5％。进一步地，所述稀酸为稀盐酸。
在本发明的一些实施方式中，步骤S4中，还包括：将所述固液分离后的滤液进行蒸发浓缩，蒸出的氨气回用到沉镁操作中，蒸发浓缩后的溶液加入碱调节pH值进行沉淀，得到镍钴渣。进一步地，所述镍钴渣进行酸溶后返回步骤S2氢离子型树脂进行吸附，解吸后得到镍钴解吸液，或返回前端萃取工序进行提纯生产精制镍钴溶液。
本发明还提供所述的资源化方法制得的六方型氢氧化镁固体在阻燃材料中的应用。
根据本发明的一种优选的实施方式，至少具有以下有益效果：
1、本发明除COD后的废水经过氢离子型树脂和钠离子型树脂两段树脂联合吸附作用，可以增加镁盐解吸液中Mg离子的含量，减少镍钴锰金属的含量，有利于后续得到纯度更高的六方型氢氧化镁阻燃剂固体，而且解吸得到的镍钴盐溶液可以直接回用到前端萃取工序提纯生产精制镍钴盐产品。采用先吸附镍钴，再吸附镁，达到镍钴与镁的分离是目前实验最佳工艺，由于市面上吸附镍钴的树脂特效选择性更强，镁只会因镍钴、镁浓度差有少量夹带，不影响对镍钴的吸附容量；若先吸附废水中的镁，再吸附镍钴，一方面吸附镁的时候，镍钴会一同吸附上去，影响树脂对镁的吸附效果，另一方面增大了镍钴的损失。
2、本发明通过特效选择性树脂分段吸附镍钴、镁的组合工艺，可实现短程高效回 收废水中的镍钴锂，且两种树脂对Li离子的吸附量低，二次吸附后液中的锂经浓缩可副产元明粉，浓缩母液沉淀得到粗碳酸锂，综合回收率可达到98％。
3、有机膦类螯合剂可以与镁盐解吸液中的Ni、Co、Ca、Fe金属离子进行螯合，在氨气的碱性条件下基本不会沉淀或被包夹在氢氧化镁沉淀中，螯合剂具有多个磷酸基团，其分子链可以优先吸附在氢氧化镁晶面(001)和(101)晶面，而(001)和(101)晶面是正六方形片状的主要显露面，因此螯合剂具有调控氢氧化镁晶型生长方向的作用，可以得到适用于阻燃剂的六方型晶体结构。此外，螯合剂也可以接枝到生成的六方型氢氧化镁固体表面对其进行改性，改性后的六方型氢氧化镁固体碳链增多，热稳定性和阻燃性能得到改善，且可以提高氢氧化镁与阻燃基体材料之间的表面粘合力以及解决二者之间相容性差的问题，达到可以添加进聚合物进行阻燃的标准。
4、沉镁反应后所得沉淀物经稀酸洗涤，可以去除表面的络合杂质金属离子，同时使表面接枝的磷酸根基团成为P(OH)，若不用稀酸洗涤，可能成为P-O-M，不利于氢氧化镁的阻燃，采用浓度低的稀酸，对氢氧化镁固体的影响较少。
附图说明
下面结合附图和实施例对本发明做进一步的说明，其中：
图1为本发明实施例1的工艺流程图；
图2为本发明己二胺四甲叉膦酸(HDTMPA)表面改性的氢氧化镁原理示意图；
图3为本发明不同己二胺四甲叉膦酸(HDTMPA)加入量(1％、3％、5％)表面改性的六方型氢氧化镁SEM图；
图4为本发明对比例2未使用螯合剂直接沉淀制备的氢氧化镁SEM图；
图5为改性前(a)、后(b)氢氧化镁的DSC曲线。
具体实施方式
以下将结合实施例对本发明的构思及产生的技术效果进行清楚、完整地描述，以充分地理解本发明的目的、特征和效果。显然，所描述的实施例只是本发明的一部分实施例，而不是全部实施例，基于本发明的实施例，本领域的技术人员在不付出创造性劳动 的前提下所获得的其他实施例，均属于本发明保护的范围。
实施例1
一种高COD镍钴锂镁废水的资源化方法，参照图1，具体过程为：
步骤(1)：高COD镍钴锂镁废水在静置后，通入0.5MPa的CO2水溶液进行气浮除油操作4h，其中高压CO2水溶液的用量为高COD镍钴锂镁废水体积的10％，高COD镍钴锂镁废水中COD含量为1500mg/L，镍金属含量100mg/L，钴金属含量35mg/L，锂金属含量10g/L，镁金属含量150mg/L；
步骤(2)：气浮除油后的废水再次经过活性炭填充柱进行吸附除油，溶液的COD可以降至150mg/L；
步骤(3)：将步骤(2)得到的废水用聚苯乙烯分子骨架螯合树脂(西安蓝晓科技有限公司氢离子型树脂D463树脂)进行Ni、Co金属离子吸附，树脂吸收塔装填高径比2：1，流速4BV/h，溶液控制pH为5，吸附操作后得到一次吸附后液；使用10％的硫酸对聚苯乙烯分子骨架螯合树脂进行解吸再生，酸洗过程保持pH＞3，得到镍2.4g/L、钴0.9g/L、镁0.1g/L的硫酸镍钴解吸液；
步骤(4)：将步骤(3)得到的一次吸附后液通入苯乙烯-二乙烯苯交联氨基膦酸螯合树脂(西安蓝晓科技有限公司氨基膦酸螯合树脂LSC-850)进行Mg金属离子吸附，操作条件为树脂吸收塔装填高径比3：1，流速5BV/h，溶液控制pH为9，操作后得到二次吸附后液；二次吸附后液进行MVR浓缩结晶得到元明粉，浓缩母液使用碳酸钠进行沉锂操作得到粗碳酸锂；
步骤(5)：使用流量为2BV/h的10％硫酸对步骤(4)中吸附饱和的苯乙烯-二乙烯苯共聚磺酰基树脂进行解吸操作，得到硫酸镁解吸液；再用流量5BV/h的20％氢氧化钠溶液对进行苯乙烯-二乙烯苯共聚磺酰基树脂再生2h；
步骤(6)：添加螯合剂HDTMPA、通入氨气对镁盐解吸液进行沉镁反应，镁盐解吸液浓度为0.5mol/L，通入氨气保持溶液pH为10，螯合剂添加量为氢氧化镁理论产量的1％，反应温度为40℃，沉淀陈化反应时间2h；陈化过滤后，水洗后再使用1％的稀盐酸洗涤，最后再使用水进行洗涤，干燥后得到六方型氢氧化镁固体；
步骤(7)：将步骤(6)中沉镁过滤后得到滤液进行蒸发浓缩，蒸出的氨气回用到步骤(6)，浓缩母液加入纯碱进行调值沉淀，得到镍钴渣；镍钴渣使用低酸进行溶解后得到酸溶液返回步骤(3)进行镍钴金属吸附和解吸操作进行回收。
实施例2
一种高COD镍钴锂镁废水的资源化方法，具体过程为：
步骤(1)：高COD镍钴锂镁废水在静置后，通入3MPa的CO2水溶液进行气浮除油操作3h，其中高压CO2水溶液的用量为高COD镍钴锂镁废水体积的8％，高COD镍钴锂镁废水中COD含量为1300mg/L，镍金属含量50mg/L，钴金属含量25mg/L，锂金属含量5g/L，镁金属含量100mg/L；
步骤(2)：气浮除油后的废水再次经过活性炭填充柱进行吸附除油，溶液的COD可以降至100mg/L；
步骤(3)：将步骤(2)得到的废水用聚苯乙烯分子骨架螯合树脂进行Ni、Co金属离子吸附，树脂吸收塔装填高径比2.5：1，流速4.5BV/h，溶液控制pH在7，吸附操作后得到一次吸附后液；使用15％的硫酸对聚苯乙烯分子骨架螯合树脂进行解吸再生，酸洗过程保持pH＞3，得到镍2.6g/L、钴1.2g/L、镁0.15g/L的硫酸镍钴解吸液；
步骤(4)：将步骤(3)得到的一次吸附后液通入苯乙烯-二乙烯苯共聚磺酰基树脂进行Mg金属离子吸附，操作条件为树脂吸收塔装填高径比2.5：1，流速4BV/h，溶液控制pH为8，操作后得到二次吸附后液；二次吸附后液进行MVR浓缩结晶得到元明粉，浓缩母液使用碳酸钠进行沉锂操作得到粗碳酸锂；
步骤(5)：使用流量为2BV/h的10％硫酸对步骤(4)中吸附饱和的苯乙烯-二乙烯苯共聚磺酰基树脂进行解吸操作，得到硫酸镁解吸液；再用流量5BV/h的20％氢氧化钠溶液对进行苯乙烯-二乙烯苯共聚磺酰基树脂再生2h；
步骤(6)：添加螯合剂HDTMPA、通入氨气对镁盐解吸液进行沉镁反应，镁盐解吸液浓度为1.5mol/L，通入氨气保持溶液pH为11，螯合剂添加量为氢氧化镁理论产量的3％，反应温度为60℃，沉淀陈化反应时间4h；陈化过滤后，水洗后再使用3％的稀盐酸洗涤，最后再使用水进行洗涤，干燥后得到六方型氢氧化镁固体；
步骤(7)：将步骤(6)中沉镁过滤后得到滤液进行蒸发浓缩，蒸出的氨气回用到步骤(6)，浓缩母液加入纯碱进行调值沉淀，得到镍钴渣；镍钴渣使用低酸进行溶解后得到酸溶液返回步骤(3)进行镍钴金属吸附和解吸操作进行回收。
实施例3
一种高COD镍钴锂镁废水的资源化方法，具体过程为：
步骤(1)：高COD镍钴锂镁废水在静置后，通入7MPa的CO2水溶液进行气浮除油操作2h，其中高压CO2水溶液的用量为高COD镍钴锂镁废水体积的10％，高COD镍钴锂镁废水中COD含量为1000mg/L，镍金属含量30mg/L，钴金属含量15mg/L，锂金属含量0.5g/L，镁金属含量50mg/L；
步骤(2)：气浮除油后的废水再次经过活性炭填充柱进行吸附除油，溶液的COD可以降至50mg/L；
步骤(3)：将步骤(2)得到的废水用聚苯乙烯分子骨架螯合树脂进行Ni、Co金属离子吸附，树脂吸收塔装填高径比3：1，流速5BV/h，溶液控制pH为8，吸附操作后得到一次吸附后液；使用20％的硫酸对聚苯乙烯分子骨架螯合树脂进行解吸再生，酸洗过程保持pH＞3，得到镍2.8g/L、钴1.3g/L、镁0.25g/L的硫酸镍钴解吸液；
步骤(4)：将步骤(3)得到的一次吸附后液通入苯乙烯-二乙烯苯共聚磺酰基树脂进行Mg金属离子吸附，操作条件为树脂吸收塔装填高径比2：1，流速3BV/h，溶液控制pH为7，操作后得到二次吸附后液；二次吸附后液进行MVR浓缩结晶得到元明粉，浓缩母液使用碳酸钠进行沉锂操作得到粗碳酸锂；
步骤(5)：使用流量为2BV/h的10％硫酸对步骤(4)中吸附饱和的苯乙烯-二乙烯苯共聚磺酰基树脂进行解吸操作，得到硫酸镁解吸液；再用流量5BV/h的20％氢氧化钠溶液对进行苯乙烯-二乙烯苯共聚磺酰基树脂再生2h；
步骤(6)：添加螯合剂HDTMPA、通入氨气对镁盐解吸液进行沉镁反应，镁盐解吸液浓度为2.5mol/L，通入氨气保持溶液pH为12，螯合剂添加量为氢氧化镁理论产量的5％，反应温度为80℃，沉淀陈化反应时间6h；陈化过滤后，水洗后再使用5％的稀盐酸洗涤，最后再使用水进行洗涤，干燥后得到六方型氢氧化镁固体；
步骤(7)：将步骤(6)中沉镁过滤后得到滤液进行蒸发浓缩，蒸出的氨气回用到步骤(6)，浓缩母液加入纯碱进行调值沉淀，得到镍钴渣；镍钴渣使用低酸进行溶解后得到酸溶液返回步骤(3)进行镍钴金属吸附和解吸操作进行回收。
对比例1
一种高COD镍钴锂镁废水的资源化方法，与实施例1的区别在于，先吸附镁，再吸附镍钴，具体过程为：
步骤(1)和(2)与实施例1相同；
步骤(3)：将步骤(2)得到的废水通入苯乙烯-二乙烯苯交联氨基膦酸螯合树脂进行Mg金属离子吸附，操作条件为树脂吸收塔装填高径比3：1，流速5BV/h，溶液控制pH为9，操作后得到一次吸附后液；
步骤(4)：将步骤(3)得到的一次吸附后液通入聚苯乙烯分子骨架螯合树脂进行Ni、Co金属离子吸附，树脂吸收塔装填高径比2：1，流速4BV/h，溶液控制pH为5，操作后得到二次吸附后液；使用10％的硫酸对聚苯乙烯分子骨架螯合树脂进行解吸再生，酸洗过程保持pH＞3，得到镍2.1g/L，钴0.5g/L，镁0.05g/L硫酸镍钴解吸液；
步骤(5)：使用流量为2BV/h的10％硫酸对步骤(3)中吸附饱和的苯乙烯-二乙烯苯交联氨基膦酸螯合树脂进行解吸操作，得到硫酸镁解吸液；再用流量5BV/h的20％氢氧化钠溶液对苯乙烯-二乙烯苯共聚磺酰基树脂再生2h；
步骤(6)：将步骤(4)中得到的二次吸附后液进行MVR浓缩结晶得到元明粉，浓缩母液使用碳酸钠进行沉锂操作可以得到粗碳酸锂。
对比例2
苯乙烯-二乙烯苯共聚磺酰基树脂，与实施例3的区别在于，沉镁反应未添加螯合剂，具体过程为：
步骤(1)至(5)与实施例3相同；
步骤(6)：未添加螯合剂，直接通入氨气对镁盐溶液进行沉镁，镁盐溶液浓度为2.5mol/L，通入氨气保持溶液pH为12，反应温度为80℃，沉淀陈化反应时间6h；陈化过 滤后，在进行水洗，干燥后得到六方型氢氧化镁固体。
对实施例1-3与对比例1的硫酸镁解吸液的金属元素组成进行检测，结果如下表1所示。
表1硫酸镁解吸液的金属元素组成
注：元素含量wt％指硫酸镁解吸液中各金属元素占总金属元素的比值。
由表1可见，对比例1硫酸镁解吸液中的Mg含量明显降低，同时镍钴元素增加，这是由于苯乙烯-二乙烯苯共聚磺酰基树脂对镁的特效选择性不够强，在吸附镁的时候，部分镍钴会一同吸附上去，影响树脂对镁的吸附效果。而实施例1先吸附镍钴，再吸附镁，聚苯乙烯分子骨架螯合树脂对镍钴的特效选择性更强，镁只有少量夹带，不影响对镍钴的吸附容量。
对实施例1-3与对比例2的氢氧化镁固体的金属元素组成、比表面积(BET)、D50进行检测，结果如下表2所示。
表2氢氧化镁固体的金属元素组成、BET、D50
由表2可见，对比例2制得的氢氧化镁固体中杂质元素明显比实施例3的多，这是由于实施例3加入螯合剂后，螯合剂可以与硫酸镁解吸液中的Ni、Co、Ca、Fe金属离 子进行螯合，基本不会沉淀或被包夹在氢氧化镁沉淀中，提高了氢氧化镁的纯度。对比例2的比表面积也明显比实施例3高，表明未使用螯合剂生成的氢氧化镁晶体有明显缺陷，晶型不完整。
实施例1-3与对比例1-2的各金属收率如下表3所示。
表3实施例和对比例的各金属收率
对比例1镍钴镁回收率明显降低，这是由于苯乙烯-二乙烯苯交联氨基膦酸螯合树脂对镁的特效选择性不够强，在吸附镁的时候，部分镍钴会一同吸附上去，影响树脂对镁的吸附效果。而实施例1先吸附镍钴，再吸附镁，聚苯乙烯分子骨架螯合树脂对镍钴的特效选择性更强，镁只有少量夹带，不影响对镍钴的吸附容量。对比例2镍钴锂镁回收率与实施例3相差不大，这是由于实施例3加入的螯合剂不影响镁的回收率，只对六方型氢氧化镁晶型有影响。采用特效选择性树脂分段吸附镍钴、镁组合工艺，可以增加镍钴锂镁回收率。
图3为使用不同加入量(1％、3％、5％)的己二胺四甲叉膦酸(HDTMPA)进行表面改性的六方型氢氧化镁SEM图；图4为对比例2未使用螯合剂直接沉淀制备的氢氧化镁SEM图。由图中可见，在分别加入1％、3％、5％HDTMPA的条件下制备的六方型氢氧化镁与不加入螯合剂有着明显的不同，未使用螯合剂生成的晶体形貌不一，交错重叠，团聚严重，晶体有明显缺陷。随着HDTMPA加入，得到的晶型更加完整，排列更加整齐，团聚情况得到改善。加入较少量HDTMPA(1％)，晶型仍有不规则、团聚的片状，这是由于螯合剂分子链不足。加入较多HDTMPA(5％)，过长的分子链可能导致六边形薄片生长过程相互缠绕。加入适量的HDTMPA(3％)可得到更多改性成功的六 方型氢氧化镁。
图5为分别对应于实施例3和对比例2的改性前(a)、后(b)的氢氧化镁的DSC曲线。六方型氢氧化镁固体表面经过HDTMPA改性后，碳链增多，热稳定性和阻燃性能得到改善，改性后氢氧化镁的吸热量增加，吸热焓增大，由于螯合剂HDTMPA接枝后，热解温度升高。
上面结合附图对本发明实施例作了详细说明，但是本发明不限于上述实施例，在所属技术领域普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下作出各种变化。此外，在不冲突的情况下，本发明的实施例及实施例中的特征可以相互组合。

Claims (10)

  1. 一种高COD镍钴锂镁废水的资源化方法，其特征在于，包括以下步骤：
    S1：对高COD镍钴锂镁废水进行除油处理，得到除油后液；
    S2：用氢离子型树脂对所述除油后液中的Ni、Co离子进行吸附，得到一次吸附后液；
    S3：用钠离子型树脂对所述一次吸附后液中的Mg离子进行吸附，得到二次吸附后液，再用酸对吸附后的钠离子型树脂进行解吸处理，得到镁盐解吸液；
    S4：在所述镁盐解吸液中加入有机膦类螯合剂、并通入氨气进行沉镁反应，陈化后固液分离，所得沉淀物用水和稀酸洗涤，得到六方型氢氧化镁固体。
  2. 根据权利要求1所述的资源化方法，其特征在于，步骤S1中，所述高COD镍钴锂镁废水中COD含量为1000-1500mg/L，镍金属含量为30-100mg/L，钴金属含量为20-100mg/L，锂金属含量为0.5-10g/L，镁金属含量为50-150mg/L。
  3. 根据权利要求1所述的资源化方法，其特征在于，步骤S1中，所述除油的过程为：先向所述高COD镍钴锂镁废水中通入高压CO2水溶液或高压CO2液体进行气浮除油，再将气浮除油后的废水经过填充柱进行吸附除油，得到所述除油后液。
  4. 根据权利要求1所述的资源化方法，其特征在于，步骤S2中，所述氢离子型树脂为聚苯乙烯分子骨架螯合树脂。
  5. 根据权利要求1所述的资源化方法，其特征在于，步骤S3中，所述钠离子型树脂为苯乙烯-二乙烯苯共聚磺酰基树脂、苯乙烯-二乙烯苯交联氨基膦酸螯合树脂或聚苯乙烯共聚I型季胺官能基树脂。
  6. 根据权利要求1所述的资源化方法，其特征在于，步骤S3中，还包括：对所述二次吸附后液进行MVR浓缩得到元明粉和浓缩后液，所述浓缩后液用碳酸钠进行沉锂得到粗碳酸锂。
  7. 根据权利要求1所述的资源化方法，其特征在于，步骤S4中，所述有机膦类螯合剂为己二胺四甲叉膦酸、乙二胺四亚甲基膦酸、羟基乙叉二膦酸、氨基三亚甲基膦酸、 己基膦酸或十二烷基膦酸中的至少一种。
  8. 根据权利要求1所述的资源化方法，其特征在于，步骤S4中，所述有机膦类螯合剂的添加量为氢氧化镁理论产量的1wt％-5wt％。
  9. 根据权利要求1所述的资源化方法，其特征在于，步骤S4中，还包括：将所述固液分离后的滤液进行蒸发浓缩，蒸出的氨气回用到沉镁操作中，蒸发浓缩后的溶液加入碱调节pH值进行沉淀，得到镍钴渣。
  10. 如权利要求1-9任一项所述的资源化方法制得的所述六方型氢氧化镁固体在阻燃材料中的应用。
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