Preparation method and application of material for removing heavy metals from lithium battery waste liquid

Abstract

The application provides a material preparation method and application for removing heavy metals in lithium battery waste liquid, and relates to the technical field of wastewater treatment. First, chitosan is dispersed in acetic acid (1 Vol%), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide and L-cysteine are sequentially added, and sealed, light-avoiding stirring is conducted for 24 hours; then, the product is precipitated by using anhydrous ethanol, followed by centrifugation and washing by using ethanol and deionized water, and the sample is vacuum dried at 50 DEG C to obtain L-cysteine modified chitosan (Cys-CTS); Cys-CTS and cetyltrimethylammonium bromide are added into the heavy metal-containing wastewater, and magnetic stirring is conducted; then, polyacrylamide is added into the stirring solution, and after sufficient stirring for 30 minutes, heavy metals can be removed by static settling. The application directly utilizes a flocculant to flocculate and precipitate heavy metals, has high heavy metal removal efficiency, saves cost, has a simple process flow and does not need complex special equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a material preparation method for removing heavy metals in lithium battery waste liquid and application. BACKGROUND

[0002] At present, in the production of lithium batteries, the generated contaminated wastewater contains a large amount of heavy metal ions and toxic and harmful substances, such as chromium, cadmium, lead, etc. Chromium is one of the most toxic heavy metals. According to the drinking water guidelines formulated by the World Health Organization, the maximum allowable limit of total chromium is 0.05 mg / L. When present at a higher concentration, chromium can cause significant health problems, especially the toxicity, mutagenicity and carcinogenicity of Cr(VI) are 500 times of Cr(III). Heavy metals have the property of bioaccumulation, which can directly threaten human health after entering the food chain. In addition, the self-purification ability of water body is limited, and the accumulated heavy metal pollution in water body is difficult to completely remove. How to scientifically monitor and effectively remove the heavy metal pollution in water body to make it reach a safe level is still a great challenge for environmental protection workers. Therefore, it is crucial to develop new, efficient and low-cost heavy metal removal technology.

[0003] In recent years, modified adsorbents based on natural polymer materials have attracted extensive attention due to their environmental friendliness, renewability and high adsorption performance. Chitosan, as a natural polysaccharide material, has abundant amino and hydroxyl functional groups, and has been widely used in wastewater treatment. However, the adsorption capacity and selectivity of chitosan are limited, and it is often necessary to improve them through chemical modification methods such as graft copolymerization, crosslinking and acylation. L-cysteine, as a sulfur-containing amino acid, has reducing and chelating properties, making it an ideal candidate for binding with heavy metal ions.

[0004] At present, the commonly used heavy metal wastewater treatment technologies include chemical precipitation method, ion exchange method, membrane separation method and adsorption method, etc. However, these traditional heavy metal wastewater treatment technologies have some significant shortcomings such as high treatment cost, relatively complex operation process, limited adaptability to heavy metal ions, possible frequent replacement of treatment materials and poor water quality stability after treatment, etc. The flocculation sedimentation method can avoid these shortcomings and is more simple and easy to operate. It usually has relatively low cost and can achieve effective treatment of heavy metals through a simple sedimentation process by adding appropriate flocculants; it has good treatment effect on various heavy metal ions and strong adaptability; and the water quality can remain stable for a long time after treatment, which is a practical and obviously advantageous heavy metal wastewater treatment method. However, the existing flocculation sedimentation method still has some shortcomings such as poor treatment effect on high-concentration wastewater, large sludge production and secondary pollution caused by flocculants. SUMMARY

[0005] In order to solve the above technical problems existing in the prior art, the embodiment of the present application provides a material preparation method for removing heavy metals in lithium battery waste liquid and application. The technical solution is as follows:

[0006] A material preparation method for removing heavy metals in lithium battery waste liquid, the method comprises:

[0007] S11, dispersing chitosan (CTS) in acetic acid solution to form a uniform solution;

[0008] S12, adding 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC), N-hydroxysuccinimide (NHS) and L-cysteine (L-Cys) into the uniform solution obtained in step S11 in sequence to obtain a mixed solution;

[0009] S13, adjusting the pH value of the mixed solution obtained in step S12, then sealing, and continuously stirring the mixed solution under light-proof condition for 24h;

[0010] S14, adding anhydrous ethanol to precipitate the product in the stirred solution obtained in step S13, then centrifuging the precipitate, and washing the centrifuged precipitate with ethanol and deionized water, vacuum drying the obtained sample at 50°C to obtain material Cys-CTS.

[0011] The concentration of acetic acid solution in step S11 is 1 Vol%, and the dosage ratio of chitosan to acetic acid solution is 1g: 50-300ml.

[0012] The deacetylation degree of CTS in step S11 is more than 95%, and the viscosity is 100-200map·s.

[0013] The mass ratio of chitosan, 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide, N-hydroxysuccinimide and L-cysteine in step S12 is 3:2.3:4:3;

[0014] The purity of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide is 95%, the purity of N-hydroxysuccinimide is 98%, and the purity of L-cysteine is 99%.

[0015] In step S12, 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide is replaced by a carbodiimide reagent, and N-hydroxysuccinimide is replaced by sulfo-N-hydroxysuccinimide.

[0016] In step S13, the pH value of the mixed solution is adjusted to 1-3.5; generally, a hydrochloric acid solution containing 2% volume fraction of concentrated hydrochloric acid is used to adjust the pH value.

[0017] The stirring rate in step S13 is 400-700rpm.

[0018] The centrifuge speed in the step S14 of centrifugal separation of the precipitate is above 500 rpm.

[0019] The amount of anhydrous ethanol in the step S14 is 4-6 times of the acetic acid solution (1 Vol%).

[0020] The ethanol and deionized water are each washed for more than three times in the step S14.

[0021] The application of the material for removing heavy metals in lithium battery waste liquid includes the following steps:

[0022] S21, adjusting the pH value of the lithium battery waste liquid, adding cetyltrimethylammonium bromide (CTAB) and the material Cys-CTS obtained in the step S14 into the lithium battery waste liquid, and performing magnetic stirring to obtain a mixed stirring liquid;

[0023] S22, adding a flocculant polyacrylamide into the mixed stirring liquid obtained in the step S21, fully stirring for 30 min, and then standing and settling for 24 h, and then filtering to remove the heavy metals in the solution.

[0024] The lithium battery waste liquid contains Cr(Ⅵ) in the step S21, and the concentration of Cr(Ⅵ) is 30 mg / L.

[0025] The pH value of the lithium battery waste liquid is adjusted to 1-4 in the step S21. Generally, hydrochloric acid solution or sodium hydroxide solution is used for adjustment.

[0026] The purity of the cetyltrimethylammonium bromide (CTAB) is 99% in the step S21, and the dosage is 300-600 mg / L, and the dosage of Cys-CTS is 2-5 g / L.

[0027] The cetyltrimethylammonium bromide in the step S21 is replaced by dodecyltrimethylammonium bromide or cetyltrimethylammonium chloride.

[0028] The rate of the magnetic stirring in the step S21 is 400-700 rpm, and the time is 2 h.

[0029] The mass fraction of the flocculant PAM in the step S22 is 0.1%, and the dosage of the flocculant is 25-150 ml / L.

[0030] The PAM is non-ionic, and the molecular weight is 5 million.

[0031] The technical scheme provided by the embodiment of the application has at least the following beneficial effects:

[0032] The above scheme has the advantages of simple process, wide source of CTS, non-toxicity, easy degradation, low cost, good environmental and economic benefits, and the like.

[0033] The above scheme has the advantages of the synergistic effect of Cys-CTS and CTAB and the use of PAM, which significantly improves the removal efficiency of heavy metals.

[0034] The above scheme has the advantages of simple one-step precipitation process, use of flocculant PAM for precipitation and removal of heavy metal complexes, simple operation process, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0036] Figure 1 is the FT-IR graph of CTS and Cys-CTS involved in the material preparation method for removing Cr(Ⅵ) in lithium battery waste liquid provided by the embodiments of the present application;

[0037] Figure 2 is the SEM-EDS graph of CTS and Cys-CTS involved in the embodiments of the present application;

[0038] Figure 3 is the Cr(Ⅵ) removal rate of CTS and Cys-CTS without CTAB in the embodiments of the present application;

[0039] Figure 4 is the influence of Cys-CTS dosage on the Cr(Ⅵ) removal rate under the condition of adding CTAB in the embodiments of the present application.

[0040] Figure 5 is the influence of Cys-CTS and CTAB on the Cr(Ⅵ) removal rate in the embodiments of the present application;

[0041] Figure 6 is the influence of the pH of the Cr(Ⅵ) containing solution on the Cr(Ⅵ) removal rate in the experimental process in the embodiments of the present application;

[0042] Figure 7is the influence of the PAM dosage on the precipitation effect in the embodiment of the present application;

[0043] Figure 8 is the influence of the precipitation time on the precipitation effect in the embodiment of the present application. DETAILED DESCRIPTION

[0044] The technical solutions in the present application will be described below with reference to the drawings.

[0045] In the embodiments of the present application, the words such as "example", "for example" and the like are used to represent as an example, illustration or description. Any embodiment or design scheme described as "example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the word "example" is intended to present the concept in a specific manner. In addition, in the embodiments of the present application, the meaning expressed by "and / or" can be both, or can be one of the two.

[0046] In order to make the technical problems, technical solutions and advantages of the present application clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0047] The embodiments of the present application provide a material preparation method for removing heavy metals in lithium battery waste liquid and application thereof.

[0048] The material preparation method for removing heavy metals in lithium battery waste liquid comprises the following steps:

[0049] S11, dispersing chitosan in acetic acid solution to form a uniform solution;

[0050] S12, adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide and L-cysteine into the uniform solution obtained in step S11 in sequence to obtain a mixed solution;

[0051] S13, adjusting the pH value of the mixed solution obtained in step S12, then sealing, and continuously stirring the mixed solution under light-proof conditions for 24 hours;

[0052] S14, adding anhydrous ethanol to the stirred solution obtained in step S13 to precipitate the product, then centrifuging, and washing the precipitate after centrifugation with ethanol and deionized water, vacuum drying the obtained sample at 50 DEG C to obtain material Cys-CTS.

[0053] The application of the material for removing heavy metals in lithium battery waste liquid comprises the following steps:

[0054] S21, adjusting the pH value of the lithium battery waste liquid, adding cetyltrimethylammonium bromide and the material Cys-CTS obtained in step S14 into the lithium battery waste liquid, and performing magnetic stirring to obtain a mixed stirring liquid;

[0055] S22, add flocculant polyacrylamide to the mixed stirring solution obtained in step S21, fully stir for 30 min, then stand and settle for 24 h, and filter to remove the heavy metals in the solution.

[0056] The following will be described in conjunction with specific examples.

[0057] Example 1

[0058] 0.1379 g of potassium dichromate was dissolved in ultrapure water to prepare a Cr(Ⅵ) solution of 30 mg / L to simulate actual Cr(Ⅵ) waste liquid.

[0059] 200 ml of the prepared Cr(Ⅵ) solution was taken in a conical flask, the solution was adjusted to pH = 3, 0.4 g of Cys-CTS was added, and magnetic stirring was performed for two hours. Then 10 ml of 0.1% PAM was added to the mixed stirring solution, fully stirred for 30 min, and then naturally stood and settled for 24 h. After settling, sampling and filtration were performed to detect the concentration of Cr(Ⅵ) in the solution. The concentration of Cr(Ⅵ) was analyzed by 1,5-diphenylcarbazide spectrophotometry.

[0060] The above Cys-CTS sample was characterized by Figure 1 the characteristic peaks in the infrared spectrum and Figure 2 the SEM image and EDS element mapping image can prove that L-Cys is successfully inserted into CTS.

[0061] In Example 1, Cys-CTS was replaced by CTS, and the other conditions of Example 1 were not changed, and Figure 3 . Figure 3 The Cr(Ⅵ) removal rate of CTS and Cys-CTS without adding CTAB is shown in Table 1. Figure 3 As can be seen from Table 1, after introducing L-Cys, the selective adsorption capacity of CTS for Cr(Ⅵ) is enhanced, and the Cr(Ⅵ) removal rate is increased from 23.2% to 74.1%.

[0062] Example 2

[0063] 0.1379 g of potassium dichromate was dissolved in ultrapure water to prepare a Cr(Ⅵ) solution of 30 mg / L to simulate actual Cr(Ⅵ) waste liquid.

[0064] 200 ml of the prepared Cr(Ⅵ) solution was taken in a conical flask, the solution was adjusted to pH = 3, 0.4 g of Cys-CTS and 0.06 g of CTAB were added, and magnetic stirring was performed for two hours. Then 10 ml of 0.1% PAM was added to the mixed stirring solution, fully stirred for 30 min, and then naturally stood and settled for 24 h. After settling, sampling and filtration were performed to detect the concentration of Cr(Ⅵ) in the solution. The concentration of Cr(Ⅵ) was analyzed by 1,5-diphenylcarbazide spectrophotometry.

[0065] The Cys-CTS dosage in Example 2 was changed to 0.1 g, 0.2 g, 0.6 g, 0.8 g, and 1.0 g, respectively. The other conditions of Example 2 were not changed, and the following results were obtained Figure 4 . Figure 4 The effect of Cys-CTS dosage on Cr(Ⅵ) removal rate under the condition of adding CTAB. It can be seen from Figure 4 that the dosage of Cys-CTS has a significant effect on the removal efficiency of Cr(Ⅵ). As the dosage increases from 0.1 g to 1.0 g, the removal rate increases from about 88% to nearly 96%. This phenomenon shows that the introduction of L-Cys enhances the removal capacity of CTS, providing more complexation sites to capture Cr(Ⅵ).

[0066] The dosage of Cys-CTS in Example 2 was changed to only add CTAB. The other conditions of Example 2 were not changed, and combined with Example 1, the following results were obtained Figure 5 . Figure 5 The effect of Cys-CTS and CTAB on Cr(Ⅵ) removal rate. It can be seen from Figure 5 that the effect of adding Cys-CTS or CTAB alone is not good. When Cys-CTS and CTAB are used together, the removal efficiency is significantly improved through the synergistic effect of chemical and physical mechanisms, from 74.1% to 94.82%.

[0067] The pH of the solution in Example 2 was changed to adjust the solution pH to pH = 1, pH = 2, pH = 4, pH = 6, pH = 8, pH = 10, and pH = 12. The other conditions of Example 2 were not changed, and the following results were obtained Figure 6 . Figure 6 The effect of solution pH on Cr(Ⅵ) removal rate during the experiment. It can be seen from Figure 6 that the Cr(Ⅵ) removal rate under acidic conditions is much higher than that under alkaline conditions.

[0068] Example 3

[0069] 0.1379 g of potassium dichromate was dissolved in ultrapure water to prepare a 30 mg / L Cr(Ⅵ) solution to simulate actual Cr(Ⅵ) waste liquid.

[0070] 200 ml of the prepared Cr(Ⅵ) solution was taken in a conical flask, the solution was adjusted to pH = 3, 0.6 g of Cys-CTS and 0.06 g of CTAB were added, and magnetic stirring was carried out for 2 h. Then 10 ml of 0.1% PAM was added to the mixed and stirred solution, and after stirring for 30 min, the supernatant was taken after natural static settling for 24 h, and the turbidity of the supernatant was detected.

[0071] The PAM dosage in Example 3 is changed, and the PAM dosage is changed to 0 ml, 5 ml, 15 ml, 20 ml and 30 ml respectively. The conditions of Example 3 are not changed, and the following results are obtained Figure 7 . Figure 7 The influence of PAM dosage on the precipitation effect is shown in the following table. Figure 7 It can be seen that with the increase of PAM dosage, the turbidity of the solution rapidly decreases from about 375 NTU in the 0-10 mL stage, indicating that the introduction of PAM effectively promotes the aggregation and settling of particles. With the continuous increase of PAM dosage (10-30 mL), the turbidity change tends to be stable, with a slight decrease. This shows that after a certain amount, the additional addition of PAM is no longer significant to the improvement of turbidity.

[0072] The precipitation time after adding PAM in Example 3 is changed, and the precipitation time is changed to 1 h, 4 h, 8 h, 12 h, 16 h and 20 h respectively. The conditions of Example 3 are not changed, and the following results are obtained Figure 8 . Figure 8 The influence of precipitation time on the precipitation effect is shown in the following table. Figure 8 It can be seen that with the increase of precipitation time, the turbidity of the solution shows a downward trend, and the suspended particles are gradually removed effectively. After 12 h, the solution turbidity decreases slowly, and tends to be stable at 24 h.

[0073] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing materials to remove heavy metals from lithium battery wastewater, characterized in that, The method includes: S11. Disperse chitosan in acetic acid solution to form a homogeneous solution; S12. Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide and L-cysteine ​​to the homogeneous solution obtained in step S11 in sequence to obtain a mixed solution. S13. Adjust the pH value of the mixed solution obtained in step S12, then seal it and stir the mixed solution continuously for 24 hours under light-protected conditions. S14. Add anhydrous ethanol to the solution obtained after stirring in step S13 to precipitate the product, then centrifuge to separate the precipitate, and wash the precipitate after centrifugation with ethanol and deionized water. Dry the sample under vacuum at 50°C to obtain the material Cys-CTS. In step S12, the mass ratio of chitosan, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, N-hydroxysuccinimide, and L-cysteine ​​is 3:2.3:4:

3. The purity of the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is 95%, the purity of the N-hydroxysuccinimide is 98%, and the purity of the L-cysteine ​​is 99%. The application of the material for removing heavy metals from lithium battery waste liquid includes the following steps: S21. Adjust the pH value of the lithium battery waste liquid, add hexadecyltrimethylammonium bromide and Cys-CTS obtained in step S14 to the lithium battery waste liquid, and perform magnetic stirring to obtain a mixed stirring liquid. S22. Add flocculant polyacrylamide to the mixed liquid obtained in step S21, stir thoroughly for 30 minutes, let it stand for 24 hours, filter, and the heavy metals in the solution can be removed. In step S21, the pH of the lithium battery waste liquid is adjusted to 1-4.

2. The method for preparing materials to remove heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S11, the concentration of the acetic acid solution is 1 Vol%, and the ratio of chitosan to acetic acid solution is 1 g: 50-300 ml.

3. The method for preparing materials to remove heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S12, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is replaced by a carbodiimide reagent, and N-hydroxysuccinimide is replaced by sulfon-N-hydroxysuccinimide.

4. The method for preparing materials to remove heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S13, the pH value of the mixed solution is adjusted to 1-3.

5.

5. The material for removing heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S21, the dosage of cetyltrimethylammonium bromide is 300-600 mg / L, and the dosage of Cys-CTS is 2-5 g / L.

6. The material for removing heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S21, hexadecyltrimethylammonium bromide is replaced with dodecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride.

7. The material for removing heavy metals from lithium battery wastewater according to claim 1, characterized in that, In step S22, the mass fraction of flocculant PAM is 0.1%, and the dosage of flocculant is 25-150 ml / L.

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