A method for solidifying cobalt ions in waste liquid

Abstract

The present invention relates to the technical field of treatment of cobalt ions in waste liquid, and more particularly to a method for solidifying cobalt ions in waste liquid. The method comprises the following steps: (1) adding silicate and aluminum salt to cobalt-containing waste liquid, mixing uniformly, and adjusting the pH value to 7-11 to obtain a mixture; (2) placing the mixture in step (1) in a reactor and reacting under constant temperature; (3) the reaction is terminated, cooled to room temperature, and the suspension is separated to obtain a cobalt solidified body and cobalt-free wastewater, thereby achieving the solidification of cobalt. The method provided by the present invention achieves highly efficient solidification of cobalt ions by potential balance, participation in polymerization reaction and the inclusive effect of a three-dimensional network, with a fixation rate of up to 100%; the cobalt solidified body formed has high stability and a leaching rate of as low as 0.25%. The solidification method process provided by the present invention is simple, reaction conditions are easily controlled, and operability is strong, with a wide range of application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of treatment of cobalt ions in waste liquid, in particular to a method for solidifying cobalt ions in waste liquid. Background Art

[0002] Cobalt (Co) is a lustrous, steel-gray metal located in the fourth period of the periodic table with an atomic number of 27. In nature, cobalt primarily exists in divalent and trivalent forms, belonging to the transition metal class. Currently, it is primarily used in circuits, aerospace, new energy batteries, metallurgy, and environmental protection. With the rapid development of new energy lithium batteries in recent years, lithium cobalt oxide, the primary cathode material for lithium batteries, will generate significant amounts of cobalt-related wastewater as cobalt-containing electrode materials are produced and decommissioned.

[0003] Since cobalt salts are easily soluble and non-biodegradable, and can be used as Co 2+ It migrates in the form of water, so it is easy to accumulate in aquatic plants and animals, and can be enriched into the human body through the food chain. 2+ It cannot be metabolized by the body and can cause great harm to health. Given the bioaccumulation, difficulty in degradation and potential toxicity of cobalt, it is particularly important to control cobalt pollution in wastewater.

[0004] At present, domestic and foreign researchers focus on adsorption, ion exchange and chemical precipitation to effectively remove Co from water. 2+ The main strategy is to adjust the process parameters and adsorbent characteristics to improve the removal rate, with the aim of removing the easily migrated Co in the water. 2+ Transferring to an inert solid phase for solidification slows down its migration activity in the environment, but little attention has been paid to its stability after transfer to the solid phase. Cobalt ions do not disappear naturally in the environment, and unstabilized cobalt ions pose a risk of secondary pollution from leaching. Therefore, exploring strategies for stabilizing and solidifying cobalt ions in aqueous solutions will be an effective way to avoid their environmental pollution risks.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The object of the present invention is to provide a method for solidifying cobalt ions in waste liquid, which can effectively seal the cobalt ions in the waste liquid, and the formed cobalt solid body has high stability and low leaching rate.

[0007] The present invention provides a method for solidifying cobalt ions in waste liquid, comprising the following steps:

[0008] (1) adding silicate and aluminum salt to the cobalt-containing waste liquid, mixing them uniformly, and adjusting the pH value to 7-11 to obtain a mixture;

[0009] (2) placing the mixture in step (1) in a reactor and reacting under constant temperature conditions;

[0010] (3) After the reaction is completed, the suspension is cooled to room temperature and the suspension is separated to obtain a cobalt solid body and a waste liquid free of cobalt, thereby achieving cobalt solidification.

[0011] Preferably, the molar ratio of silicon, aluminum and cobalt in the mixture in step (1) is (0.1-4):(0.1-4):(1-16).

[0012] Preferably, the molar ratio of silicon, aluminum and cobalt in the mixture in step (1) is 2:1:1.

[0013] Preferably, the cobalt-containing waste liquid in step (1) 2+ The concentration is 1-16mmol / L.

[0014] Preferably, the cobalt-containing waste liquid in step (1) 2+ The concentration is 8mmol / L.

[0015] Preferably, the reaction temperature in step (2) is 25-200°C, and the reaction time is 22-24 hours. More preferably, the reaction temperature is 200°C, and the reaction time is 24 hours.

[0016] Preferably, the silicate in step (1) is sodium silicate nonahydrate.

[0017] Preferably, the aluminum salt in step (1) is aluminum nitrate.

[0018] Preferably, the reagents used to adjust the pH value in step (1) are sodium hydroxide solution and nitric acid solution.

[0019] Preferably, in step (3), the suspension is separated by centrifugation.

[0020] In summary, the present invention has the following advantages compared with the prior art:

[0021] The technical solution of the present invention realizes the solidification of cobalt by utilizing silicate and aluminum salt under hydrothermal conditions. The cobalt ions participate in the formation of the three-dimensional network of the aluminosilicate polymer through potential balance, and during the heating process, part of the cobalt enters the polymer structure and is gradually stabilized in the aluminosilicate polymer by replacing the position of silicon atoms or aluminum atoms in the aluminosilicate. Therefore, the method provided by the present invention realizes a very efficient solidification of cobalt ions through potential balance, participation in polymerization reaction and the inclusion of the three-dimensional network, with a fixation rate of up to 100%; the cobalt solid body formed is highly stable and the leaching rate is as low as 0.25%. The solidification method provided by the present invention has a simple process flow, easy-to-control reaction conditions, strong operability, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The figure is a bar graph showing the fixation efficiency of cobalt ions in waste liquid at different temperatures in the present invention;

[0024] Figure 2 The cobalt ion leaching rate bar graph of the cobalt solidified body at different temperatures in the present invention;

[0025] Figure 3 This is a line graph of pH-fixation rate when the molar ratio of silicon, aluminum, and cobalt in the mixture of the present invention is 2:1:(1-16);

[0026] Figure 4 This is a line graph of pH-fixation rate when the molar ratio of silicon, aluminum, and cobalt in the mixture of the present invention is (0-4):1:8;

[0027] Figure 5 This is a line graph showing the pH-fixation rate when the molar ratio of silicon, aluminum, and cobalt in the mixture of the present invention is 2:(0-4):8. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0031] Weigh 0.233 g of cobalt nitrate hexahydrate solid and dissolve it in pure water, stir it thoroughly, and transfer it to a 100 mL volumetric flask and make up the volume after it is completely dissolved to obtain 8 mmol / L of cobalt-containing wastewater.

[0032] Example 1

[0033] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0034] (1) Sodium silicate nonahydrate and aluminum nitrate are added to wastewater containing a cobalt ion concentration of 8 mmol / L, the mixture is evenly mixed, and the pH value is adjusted to 7 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:8.

[0035] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes, and then transferred to a polytetrafluoroethylene reactor, placed in an electric constant temperature drying oven, and reacted at 25° C. for 24 hours.

[0036] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0037] Example 2

[0038] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0039] (1) Sodium silicate nonahydrate and aluminum nitrate are added to wastewater containing a cobalt ion concentration of 8 mmol / L, the mixture is evenly mixed, and the pH value is adjusted to 7 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:8.

[0040] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes, then transferred to a polytetrafluoroethylene reactor, placed in an electric constant temperature drying oven and reacted at 50° C. for 24 hours.

[0041] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0042] Example 3

[0043] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0044] (1) Sodium silicate nonahydrate and aluminum nitrate are added to wastewater containing a cobalt ion concentration of 8 mmol / L, the mixture is evenly mixed, and the pH value is adjusted to 7 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:8.

[0045] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes, then transferred to a polytetrafluoroethylene reactor, placed in an electric constant temperature drying oven, and reacted at 100° C. for 24 hours.

[0046] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0047] Example 4

[0048] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0049] (1) Sodium silicate nonahydrate and aluminum nitrate are added to wastewater containing a cobalt ion concentration of 8 mmol / L, the mixture is evenly mixed, and the pH value is adjusted to 7 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:8.

[0050] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes, then transferred to a polytetrafluoroethylene reactor, placed in an electric constant temperature drying oven, and reacted at 150° C. for 24 hours.

[0051] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0052] Example 5

[0053] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0054] (1) adding sodium silicate nonahydrate and aluminum nitrate to wastewater containing a cobalt ion concentration of 8 mmol / L, mixing the mixture evenly, and adjusting the pH value to 7 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:8;

[0055] (2) The mixture prepared in step (1) was ultrasonically dispersed for 10 minutes, and then transferred to a polytetrafluoroethylene reactor, and placed in an electric constant temperature drying oven to react at 200° C. for 24 hours.

[0056] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0057] Example 6

[0058] A method for solidifying cobalt ions in waste liquid, the specific process is as follows:

[0059] (1) Sodium silicate nonahydrate and aluminum nitrate are added to wastewater containing a cobalt ion concentration of 8 mmol / L, the mixture is evenly mixed, and the pH value is adjusted to 11 with a sodium hydroxide solution and a nitric acid solution to obtain a mixture, wherein the molar ratio of silicon, aluminum, and cobalt elements in the mixture is 2:1:1.

[0060] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes, and then transferred to a polytetrafluoroethylene reactor, placed in an electric constant temperature drying oven, and reacted at 25° C. for 24 hours.

[0061] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0062] Test of cobalt ion fixation rate

[0063] The cobalt ion fixation rate of the curing method in the above Examples 1-5 was determined by the following method:

[0064] 5 mL of the suspension cooled to room temperature in step (3) of Examples 1-5 was taken respectively, and filtered with a 0.45 μm microporous filter membrane. The filtrate obtained was analyzed for the residual cobalt ion concentration by inductively coupled plasma emission spectrometry, and the cobalt fixation rate was further calculated, as shown in FIG. Figure 1 As shown in the figure, the fixation rate of cobalt ions reached 87.89% at 200℃; the fixation rates at 25℃, 50℃, 100℃ and 150℃ were 61.95%, 66.85%, 71.84% and 83.97% respectively.

[0065] Testing the cobalt ion leaching rate of dicobalt solid

[0066] The cobalt solids obtained in Examples 1-5 were washed and dried with deionized water, dried to constant weight, and a buffer solution with a pH value of 3.20 was prepared with a mixed solution of nitric acid and sulfuric acid (1:2 wt.%) as a leaching agent. The constant weight cobalt solids were respectively put into the leaching agent at room temperature at a liquid-solid ratio of 10:1 (L / kg), placed on a tumbling oscillator (30 r / min) and shaken for 18 h. After sampling, the suspension was filtered through a 0.45 μm microporous membrane to obtain a filtrate. The concentration of residual cobalt ions was analyzed by inductively coupled plasma emission spectrometry, and the leaching rate of the cobalt solid was calculated according to the amount of cobalt contained in the cobalt solid and the amount of cobalt contained in the solution after leaching, as shown in FIG. Figure 2 As shown in Figure 2, the cobalt leaching rate under the solidification condition of 200 °C is as low as 0.25%.

[0067] The cobalt fixation rate at different pH values ​​was tested when the molar ratio of silicon, aluminum and cobalt was 2:1:(1-16).

[0068] Set up multiple parallel experiments to test the curing rate of different molar ratios of silicon, aluminum, and cobalt in the mixture at pH values ​​of 7, 9, and 11. The process is as follows:

[0069] (1) Sodium silicate nonahydrate and aluminum nitrate were added to wastewater containing a cobalt ion concentration of 8 mmol / L, mixed evenly, and the pH values ​​were adjusted to 7, 9, and 11 with sodium hydroxide solution and nitric acid solution to obtain a mixture, wherein the molar ratios of silicon, aluminum, and cobalt elements in the mixture were 2:1:1, 2:1:4, 2:1:8, and 2:1:16, respectively.

[0070] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes and then transferred to a polytetrafluoroethylene reactor and reacted at 200° C. for 24 hours.

[0071] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0072] The cobalt solidification rate was determined by using the method of test 1 for multiple parallel experiments in test 3, such as Figure 3 As shown, when the molar ratio of silicon, aluminum and cobalt in the mixture is 2:1:1 and the pH is 11, the solidification rate of cobalt can reach up to 100%.

[0073] The cobalt fixation rate at different pH values ​​was tested when the molar ratio of tetrasilicon aluminum to cobalt was (0-4):1:8.

[0074] (1) Sodium silicate nonahydrate and aluminum nitrate were added to wastewater containing a cobalt ion concentration of 8 mmol / L, mixed evenly, and the pH values ​​were adjusted to 7, 9, and 11 with sodium hydroxide solution and nitric acid solution to obtain a mixture, wherein the molar ratios of silicon, aluminum, and cobalt elements in the mixture were 0:1:8, 1:1:8, 2:1:8, and 4:1:8, respectively.

[0075] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes and then transferred to a polytetrafluoroethylene reactor and reacted at 200° C. for 24 hours.

[0076] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0077] The cobalt solidification rate was determined by using the method of test 1 for multiple parallel experiments in test 4, such as Figure 4As shown in the figure, when there is no silicate participating in the reaction, under the curing condition of pH = 7, the cobalt curing rate only reaches 30.25%. This is because the polymerization reaction requires silicate to provide a Si-O-Si skeleton, otherwise a network polymer cannot be formed. As the silicate content increases, the curing rate of cobalt has a low difference, indicating that the silicate content has little effect on the curing rate of cobalt.

[0078] Test the cobalt fixation rate at different pH values ​​when the molar ratio of silicon, aluminum and cobalt is 2:(0-4):8

[0079] (1) Sodium silicate nonahydrate and aluminum nitrate were added to wastewater containing a cobalt ion concentration of 8 mmol / L, mixed evenly, and the pH values ​​were adjusted to 7, 9, and 11 with sodium hydroxide solution and nitric acid solution to obtain a mixture, wherein the molar ratios of silicon, aluminum, and cobalt elements in the mixture were 2:0:8, 2:1:8, 2:2:8, and 2:4:8, respectively.

[0080] (2) The mixture in step (1) was ultrasonically dispersed for 10 minutes and then transferred to a polytetrafluoroethylene reactor and reacted at 200° C. for 24 hours.

[0081] (3) After the reaction is completed, the mixture is cooled to room temperature and the suspension is centrifuged to obtain a cobalt solid and wastewater.

[0082] The cobalt solidification rate was determined by using the method of test 1 for multiple parallel experiments in test 5, such as Figure 5 As shown in the figure, when aluminum ions are not involved in the reaction, the active sites are missing, resulting in a low cobalt solidification effect. As the aluminum ion content increases, more [AlO4] tetrahedrons are formed during the hydrothermal process. These negative surface sites achieve potential equilibrium by adsorbing cobalt ions in the solution, thereby improving the cobalt solidification effect.

[0083] The above examples and tests show that when the molar ratio of silicon, aluminum, and cobalt in the mixture is 2:1:1 and the pH value is 11, and the mixture is placed in a reactor at 200° C. for 24 hours, the cobalt solidification rate can reach 100% and the leaching rate is as low as 0.25%.

[0084] The present invention synthesizes a cobalt-containing aluminosilicate solid under hydrothermal conditions, adsorbing wastewater cobalt ions through potential balance and three-dimensional network inclusion. The cobalt ions participate in a polymerization reaction during the hydrothermal process, thereby achieving efficient cobalt sealing. The aluminosilicate hydrothermal cobalt solidification method used in the present invention has a high fixation rate and a low leaching rate, with a fixation rate of up to 100% and a leaching rate of up to 0.25%.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for solidifying cobalt ions in waste liquid, characterized in that: The following steps are involved: (1) adding silicate and aluminum salt to the cobalt-containing waste liquid, mixing them uniformly, and adjusting the pH value to 11 to obtain a mixture; (2) placing the mixture in step (1) in a reactor and reacting under constant temperature conditions; (3) After the reaction is completed, the suspension is cooled to room temperature and the suspension is separated to obtain a cobalt solidified body and cobalt-free wastewater, thereby achieving cobalt solidification; The reaction temperature in step (2) is 200° C. and the reaction time is 22-24 hours; The silicate in step (1) is sodium silicate nonahydrate; The aluminum salt in step (1) is aluminum nitrate; The molar ratio of silicon, aluminum and cobalt in the mixture in step (1) is 2:1:

1.

2. The method for solidifying cobalt ions in waste liquid according to claim 1, characterized in that: Co in the cobalt-containing wastewater in step (1) 2+ The concentration is 1-16mmol / L.

3. The method for solidifying cobalt ions in waste liquid according to claim 2, characterized in that: Co in the cobalt-containing wastewater in step (1) 2+ The concentration is 8mmol / L.

4. The method for solidifying cobalt ions in waste liquid according to claim 1, characterized in that: The reagents used to adjust the pH value in step (1) are sodium hydroxide solution and nitric acid solution.

5. The method for solidifying cobalt ions in waste liquid according to claim 1, characterized in that: In step (3), the suspension is separated by centrifugation.

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