CN112707448A

CN112707448A - Hydrotalcite-like compound, preparation method thereof and application thereof in arsenic removal

Info

Publication number: CN112707448A
Application number: CN202011417065.8A
Authority: CN
Inventors: 李青竹; 李水梅; 王庆伟; 闵小波; 刘恢; 杨志辉; 梁彦杰; 赵飞平
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2021-04-27
Anticipated expiration: 2040-12-07
Also published as: CN112707448B

Abstract

The invention discloses hydrotalcite-like compound, a preparation method thereof and application thereof in arsenic removal²⁺、Co²⁺And Mn²⁺Adding an alkaline precipitator into the heavy metal wastewater, uniformly mixing, performing hydrothermal reaction, and separating and collecting precipitate to obtain the heavy metal wastewater; among them, heavy metal waste water (Ni)²⁺+Co²⁺)：Mn²⁺In a molar ratio of 0.5 to 5: 1, adding the alkaline precipitant in an amount of controlling the pH of the reaction system to be more than 8. According to the invention, the hydrotalcite-like compound with a layered structure is formed after the lithium battery wastewater is reacted by adopting a urea hydrothermal methodThe compound is used for treating arsenic-containing wastewater, so that heavy metals in lithium battery wastewater can be recycled, the waste can be treated by the waste, and the arsenic can be removed; the prepared hydrotalcite-like compound has a plurality of surface defects and dispersed metals, and the doping of Mn obviously reduces the band gap of a system, so that the activity of a laminate is obviously improved, the surface layer is filled with active metal sites, and the effect of adsorbing arsenic-containing wastewater is excellent.

Description

Hydrotalcite-like compound, preparation method thereof and application thereof in arsenic removal

Technical Field

The invention belongs to the technical field of wastewater treatment, relates to a method for removing arsenic in wastewater, and particularly relates to hydrotalcite-like compound, a preparation method thereof and application thereof in arsenic removal.

Background

Since the 21 st century, development and application of new energy resources have gradually attracted attention from countries in the world to realize sustainable development of human society. The lithium battery has become a key project for new energy development due to the advantages of high energy density, short charging and discharging time, wide working temperature range and the like, and the production of the lithium battery is also rapidly developed; however, a large amount of wastewater is generated while the lithium battery industry is developing.

According to related reports in the prior art, industrial wastewater such as ternary concentrated water, ternary fresh water and raw material washing water can be generated in the production process of the ternary precursor of the lithium battery cathode material. In industrial wastewater produced by the lithium battery cathode material, the ternary concentrated water has the characteristics of high heavy metal content, high ammonia nitrogen concentration, high salt content, high alkalinity and the like, and is a direct threat to the ecological environment; the concentrations of heavy metal and ammonia nitrogen in the washing water are lower, but the total amount of harmful heavy metal is large; in addition, in the production process, a large amount of heavy metal ions such as nickel, cobalt, manganese and the like enter the wastewater in a multi-way migration mode, if the heavy metal ions can be properly treated, the pollution of the heavy metal ions to the environment can be greatly relieved, and meanwhile, metal resources can be effectively recycled.

In the prior art, the research reports of the resource treatment of the lithium battery wastewater are less.

The application number 201820051358.0 of the Chinese utility model discloses a lithium battery anode ternary precursor wastewater treatment device, and in the disclosed method for treating lithium battery anode ternary precursor wastewater, the treatment of heavy metals such as nickel, cobalt, manganese and the like is mainly based on the methods of adding drugs, adjusting alkali and the like, so that nickel, cobalt and manganese ions are generated and precipitated and then removed by filtration; the technology causes the loss of nickel, cobalt and manganese resources in the wastewater and generates a large amount of hazardous waste.

The Chinese patent application with the application number of 201810368700.4 discloses an adsorbent for removing arsenate ions in wastewater, and particularly relates to application of magnesium-iron binary hydrotalcite as an adsorbent for removing the arsenate ions in the wastewater, wherein the adsorption capacity can reach 415 mg/g; however, the method needs to additionally add metal salt to prepare the hydrotalcite-like adsorbent, which is uneconomical and easy to cause secondary pollution.

Arsenic pollution has great threat to environment and human health, and no report related to a method for removing arsenic by directly preparing hydrotalcite-like compound by using lithium battery wastewater components is seen so far.

In conclusion, how to properly and simply treat the lithium battery wastewater for pollution treatment and simultaneously exert the coexistence advantage of various metals to realize the treatment of wastes with processes of wastes against one another is a technical problem to be solved urgently in the field and is a development trend of recycling the lithium battery wastewater at present.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides hydrotalcite-like compound, a preparation method thereof and application thereof in arsenic removal.

The invention adopts the following technical scheme:

in one aspect, the present invention provides a method for preparing a hydrotalcite-like compound comprising adding Ni to a mixture containing Ni²⁺、Co²⁺And Mn²⁺Adding an alkaline precipitator into the heavy metal wastewater, uniformly mixing, performing hydrothermal reaction, and separating and collecting precipitate to obtain the heavy metal wastewater.

Wherein, the heavy metal wastewater contains (Ni)²⁺+Co²⁺)：Mn²⁺In a molar ratio of (0.5-5): 1, and the alkali precipitationThe addition amount of the starch is controlled to control the pH of the reaction system to be more than 8.

Specifically, the heavy metal waste water (Ni)²⁺+Co²⁺)：Mn²⁺The molar ratio of (C) is controlled to be (0.5-5): 1, hydrotalcite-like compound with single crystal phase can be obtained, and the nickel-cobalt-manganese hydrotalcite-like compound can be obtained only when the pH value of the reaction system is more than 8.

In the above technical solution, the alkaline precipitant is one or more of sodium hydroxide, sodium carbonate, hexamethylene tetramine and urea, preferably urea.

Specifically, when the alkaline precipitator is urea, the prepared hydrotalcite-like compound has larger grain size, regular internal structure and three-dimensional layered structure.

In the technical scheme, the heavy metal wastewater is one or more of ternary concentrated water, ternary fresh water and raw material washing water in the production of the lithium battery cathode material.

Specifically, in the above technical solution, the temperature of the hydrothermal reaction is 80-200 ℃, preferably 100-150 ℃.

Specifically, when the temperature of the hydrothermal reaction is too low (less than 80 ℃), the nickel-cobalt-manganese hydrotalcite cannot be generated; meanwhile, when the temperature of the hydrothermal reaction is too high (more than 200 ℃), the nickel-cobalt-manganese hydrotalcite cannot be generated.

Specifically, in the above technical scheme, the hydrothermal reaction time is 8-28h, preferably 18-23 h.

In one embodiment, the alkaline precipitating agent is urea; and the addition of the urea is Ni in the heavy metal wastewater according to the amount of the substances²⁺、Co²⁺And Mn²⁺3-3.5 times, preferably 3.3 times the sum of (A) and (B).

Specifically, ammonia released by urea hydrolysis provides alkali required for metal ion precipitation, the pH values of urea hydrolysis with different molar ratios are different, and the pH directly influences the preparation of hydrotalcite-like compound and the removal rate of heavy metals; when the addition amount of the urea is Ni in the heavy metal wastewater²⁺、Co²⁺And Mn ²⁺3 to 3.5 times of the total amount of the above components, the obtained hydrotalcite-like compound has high crystallinity,the crystal form is good.

In another embodiment, the method of making comprises adding Ni to the alloy containing Ni²⁺、Co²⁺And Mn²⁺Adding urea into the heavy metal wastewater, stirring vigorously for 12-18min, transferring the obtained clear solution into a hydrothermal kettle, sealing, placing in an oven at 80-120 ℃ for hydrothermal reaction for 8-28h, cooling to room temperature after the reaction is finished, taking the precipitate, washing with deionized water, and finally drying at 75-85 ℃ for 10-15h to obtain the heavy metal wastewater.

In another aspect, the invention provides a hydrotalcite-like compound prepared by the above preparation method.

Specifically, the hydrotalcite-like compound has a layered structure.

In another aspect, the invention provides the above preparation method or application of hydrotalcite-like compound in arsenic removal.

Specifically, the application comprises the steps of adjusting the pH value of arsenic-containing wastewater to 3-11, adding the hydrotalcite-like compound, carrying out constant-temperature oscillation reaction at 25-35 ℃, and carrying out adsorption removal.

Preferably, in the above technical scheme, the addition amount of the hydrotalcite-like compound is 0.1-2 g/L.

Further preferably, in the above technical scheme, the reaction time is 15-30h, preferably 20-25 h.

The invention has the advantages that:

(1) according to the method, components of the lithium battery wastewater are directly used for preparing hydrotalcite-like compounds to remove arsenic, the lithium battery wastewater is subjected to hydrothermal treatment by a urea hydrothermal method, and hydrotalcite-like compounds with a layered structure are formed after reaction and are used for treating arsenic-containing wastewater;

(2) according to the method, the hydrotalcite-like compound directly prepared from the lithium battery wastewater components has many surface defects and dispersed metals, and the doping of Mn obviously reduces the band gap of a system, so that the activity of the laminate is obviously improved, the surface layer is filled with active metal sites, and the method has unexpected adsorption effect in the field of treating arsenic-containing wastewater;

(3) the method is economical, environment-friendly and practical, has wide practical application prospect, and has very important practical significance in the field of environmental management.

Drawings

FIG. 1 is an XRD diagram of hydrotalcite-like compounds with different metal ratios directly prepared from waste water components of lithium batteries in example 1 according to the present invention;

FIG. 2 is a graph showing the comparison of the removal rates of Ni, Co and Mn in a stock solution of hydrotalcite-like compounds with different metal ratios directly prepared from the components of lithium battery wastewater in example 1 of the present invention;

FIG. 3 is a graph showing the comparison of the arsenic adsorption capacities of hydrotalcite-like compounds with different metal ratios directly prepared from the components of lithium battery wastewater in example 1 of the present invention;

FIG. 4 is a graph showing the comparison of the removal rates of Ni, Co and Mn in the stock solutions of hydrotalcite-like compounds with different hydrothermal temperatures directly prepared from the components of lithium battery wastewater in example 2 of the present invention;

FIG. 5 is a graph showing the comparison of arsenic adsorption capacities of hydrotalcite-like compounds obtained by directly preparing wastewater components of lithium batteries according to example 2 of the present invention;

FIG. 6 is a comparison graph of the removal rates of Ni, Co and Mn in the stock solutions of hydrotalcite-like compounds prepared directly by using the components of lithium battery wastewater in example 3 according to the present invention at different hydrothermal times;

FIG. 7 is a graph showing the comparison of arsenic adsorption capacities of hydrotalcite-like compounds prepared directly from lithium battery wastewater components according to example 3 of the present invention;

FIG. 8 is an adsorption isotherm diagram of arsenic from hydrotalcite-like compound directly prepared from lithium battery wastewater in example 4 of the present invention;

FIG. 9 is an SEM image of a hydrotalcite-like compound prepared under optimum conditions in example 4 of the present invention;

FIG. 10 is a nitrogen adsorption and desorption isotherm and pore size distribution curve of hydrotalcite-like compound prepared under optimum conditions in example 4 of the present invention;

FIG. 11 is an O1s spectrum of a hydrotalcite-like compound prepared under optimum conditions in example 4 of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the present invention, but not to limit the scope of the invention, which is defined by the claims. Unless otherwise specified, the test reagents and materials used in the examples of the present invention are commercially available. Unless otherwise specified, the technical means used in the examples of the present invention are conventional means well known to those skilled in the art.

Example 1

In this example 1, the influence of different metal ratios on the formation of nickel-cobalt-manganese hydrotalcite to treat Ni, Co, Mn and arsenic-containing wastewater in lithium battery wastewater is compared, and the specific process is as follows:

weighing a certain amount of NiSO₄·6H₂O、CoSO₄·7H₂O、MnSO₄·H₂O and CO (NH)₂)₂Dissolving in 50mL deionized water to prepare a mixed salt solution, and changing the molar ratio of Ni, Co and Mn to be n (Ni)²⁺):n(Co²⁺):n(Mn²⁺) The ratio of the urea to the Ni in the heavy metal wastewater is 3:1:1, 1:2:1, 1:1:1, 2:1:1 and 5:3:2, wherein the addition amount of the urea is calculated by the mass amount of Ni in the heavy metal wastewater²⁺、Co²⁺And Mn²⁺3.3 times the sum of; and after the mixed solution is vigorously stirred for 15min by a magnetic stirrer, transferring the clear solution into a hydrothermal kettle, putting the hydrothermal kettle into an oven, crystallizing the hydrothermal kettle for 24h at a constant temperature of 120 ℃, taking the hydrothermal kettle out, cooling the hydrothermal kettle to room temperature, washing the obtained precipitate with deionized water, and drying the obtained precipitate in the oven at 80 ℃ in vacuum to obtain LDHs with different metal ratios.

ICP-OES is used for detecting the content of residual Ni, Co and Mn in the solution after the LDHs with different metal ratios are hydrothermally synthesized, and the removal rate of Ni, Co and Mn is calculated.

The prepared LDHs is put into an arsenic-containing solution, the concentration of arsenic after reaction equilibrium is detected by ICP-OES, and the adsorption capacity is calculated.

FIGS. 1 to 3 are XRD patterns of hydrotalcite-like compounds with different metal ratios, comparison of Ni, Co and Mn removal rates in stock solutions of hydrotalcite-like compounds with different metal ratios, and comparison of arsenic adsorption capacities of hydrotalcite-like compounds with different metal ratios, respectively.

As can be seen from FIG. 1, the LDHs have sharp characteristic peaks at 2 theta of 11.36 degrees, 22.04 degrees, 34.68 degrees, 39.12 degrees, 46.32 degrees, 60.50 degrees and 61.76 degrees, the peaks correspond to (003), (006), (012), (015), (018), (110) and (113) planes respectively, and the peaks are consistent with characteristic diffraction peaks of the layered double hydroxide, which indicates that the LDHs containing NiCoMn of the trimetal layered double hydroxide is successfully prepared, and the (003) plane indicates the existence of a layered structure.

Example 2

In this example 2, the influence of different hydrothermal temperatures on the formation of nickel-cobalt-manganese hydrotalcite to treat Ni, Co, Mn and arsenic-containing wastewater in lithium battery wastewater is compared, and the specific process is as follows:

weighing a certain amount of NiSO₄·6H₂O、CoSO₄·7H₂O、MnSO₄·H₂O and CO (NH)₂)₂Dissolving in 50mL deionized water to obtain mixed salt solution, wherein n (Ni)²⁺):n(Co²⁺):n(Mn²⁺) 1:2:1, the adding amount of the urea is Ni in the heavy metal wastewater in terms of the amount of substances²⁺、Co²⁺And Mn²⁺3.3 times the sum of; violently stirring the mixed solution for 15min under a magnetic stirrer, transferring the clarified solution into a hydrothermal kettle, placing the hydrothermal kettle into an oven to crystallize at the constant temperature of 80 ℃, 90 ℃, 100 ℃, 120 ℃, 150 ℃, 180 ℃ and 200 ℃ for 24h, taking the hydrothermal kettle out, cooling the hydrothermal kettle to room temperature, washing the obtained precipitate with deionized water, and drying the obtained precipitate in the oven at the temperature of 80 ℃ in vacuum to obtain NiCo with different hydrothermal temperatures₂Mn LDHs。

ICP-OES is used for detecting the content of residual Ni, Co and Mn in the solution after the LDHs with different hydrothermal temperatures are hydrothermally synthesized, and the removal rate of Ni, Co and Mn is calculated.

And (3) putting the prepared LDHs into an arsenic-containing solution, detecting the concentration of the arsenic after reaction equilibrium by using ICP-OES, and calculating the adsorption capacity.

FIGS. 4 to 5 are a comparison graph of Ni, Co and Mn removal rates in a stock solution of hydrotalcite-like compounds at different hydrothermal temperatures and a comparison graph of arsenic adsorption capacities.

Example 3

In this embodiment 3, the influence of different hydrothermal times on the formation of nickel-cobalt-manganese hydrotalcite on the treatment of Ni, Co, Mn and arsenic-containing wastewater in lithium battery wastewater is compared, and the specific process is as follows:

weighing a certain amount of NiSO₄·6H₂O、CoSO₄·7H₂O、MnSO₄·H₂O and CO (NH)₂)₂Dissolving in 50mL deionized water to obtain mixed salt solution, wherein n (Ni)²⁺):n(Co²⁺):n(Mn²⁺) 1:2:1, the adding amount of the urea is Ni in the heavy metal wastewater in terms of the amount of substances²⁺、Co²⁺And Mn²⁺3.3 times the sum of; and after the mixed solution is stirred vigorously for 15min under a magnetic stirrer, transferring the clear solution into a hydrothermal kettle, and putting the hydrothermal kettle into an oven to crystallize at constant temperature for 8h, 12h, 16h, 20h, 24h and 28h respectively at 100 ℃. Taking out the hydrothermal kettle, cooling to room temperature, washing the obtained precipitate with deionized water, and drying the obtained precipitate in a 80 ℃ oven in vacuum to obtain NiCo with different hydrothermal times₂Mn LDHs。

And detecting the content of residual Ni, Co and Mn in the solution after hydrothermally synthesizing LDHs for different hydrothermal times by using ICP-OES, and calculating the removal rate of Ni, Co and Mn.

FIGS. 6 to 7 are a comparison graph of Ni, Co and Mn removal rates and an arsenic adsorption capacity of hydrotalcite-like raw liquids at different hydrothermal times, respectively.

Comparing fig. 2-7, it can be found that the removal rate of Ni, Co and Mn by the method is less influenced by the mole ratio, is greatly influenced by the hydrothermal temperature and time, and the removal of Ni, Co and Mn is favored at high temperature for a long time, and the removal of arsenic is favored at low temperature for a short time.

Example 4

Example 4 tests (n (Ni) under optimum conditions²⁺):n(Co²⁺):n(Mn²⁺) 1:2:1, the hydrothermal temperature is 100 ℃, and the hydrothermal time is 20h), and the specific process is as follows:

adding 25mL of arsenic-containing solution with initial concentration of 10-1000mg/L into conical flask, adding 0.025g adsorbent, and adding 0.1 mol.L^-1NaOH or 0.1 mol. L^-1Adjusting the pH value of the solution to 5.0 +/-0.1 by HCl, and carrying out constant-temperature oscillation reaction at 30 ℃, 40 ℃ and 50 ℃ for 24 hours at the rotating speed of 150 r.min^-1And filtering the solution by using a microporous filter membrane with the aperture of 0.45um, and determining the equilibrium concentration of arsenic in the solution.

FIG. 8 is a comparison graph of adsorption isotherms of hydrotalcite-like compounds directly prepared from lithium battery wastewater according to example 4 of the present invention with respect to arsenic; calculating NiCo according to Langmuir model₂The maximum equilibrium adsorption capacity of Mn LDHs to arsenic at 30 ℃, 40 ℃ and 50 ℃ is respectively as follows: 407.23, 454.04 and 518.78 mg/g.

As shown below, NiCo is shown in Table 1₂The relevant parameters of the isothermal adsorption model for adsorbing arsenic by Mn LDHs are NiCo shown in Table 2₂Pore structure parameters of Mn LDHs.

TABLE 1 NiCo₂Relevant parameters of isothermal adsorption model for adsorbing arsenic by Mn LDHs

TABLE 2 NiCo₂Pore structure parameters of Mn LDHs

The analysis of the results shows that the Freundlich model has higher correlation coefficient, which indicates that the Freundlich model can better fit adsorption data than the Langmuir model, and the adsorption process is multilayer adsorption; calculating NiCo according to Langmuir model₂The maximum equilibrium adsorption capacity of Mn LDHs to arsenic at 30 ℃, 40 ℃ and 50 ℃ is respectively as follows: 407.23, 454.04 and 518.78mg/g, slightly larger than the experimental results; furthermore, as the temperature increased, the amount of adsorption increased, indicating NiCo₂The adsorption of Mn LDHs to arsenic is an endothermic reaction; n values at different temperatures are calculated to be more than 1 according to Freundlich model fitting, which indicates that NiCo₂Mn LDHs readily adsorbs arsenic and a chemisorption process occurs.

FIG. 9 is a NiCo prepared under optimal conditions according to example 4 of the present invention₂SEM picture of Mn LDHs; as seen from the SEM image, a large amount of pores are enriched, and the surface defects are large, so that the surface layer is full of active metal sites, and the adsorption of arsenic is facilitated.

FIG. 10 is a schematic representation of NiCo prepared under optimal conditions according to example 4 of the present invention₂The nitrogen adsorption and desorption isotherms and the pore size distribution curves of the Mn LDHs; from the pore size distribution curve, it can be seen that all pores are mesoporous, indicating the presence of internal pores. The specific surface area of the LDHs is large, and enough active sites can be provided, so that the performance of adsorbing arsenic is good.

FIG. 11 is a NiCo prepared under optimal conditions according to example 4 of the present invention₂O1s spectrum of Mn LDHs; NiCo can be seen from the spectrum of O1s₂Mn LDHs respectively correspond to lattice oxygen M-O, hydroxyl-OH and adsorbed water H at 530.61eV, 531.27eV and 532.09eV₂And O. As-O characteristic peak appears at the 531.2eV position after arsenic adsorption, which shows that the coordination effect is good.

Comparative example 1

This comparative example provides NiCo prepared according to example 3 of the invention₂Mn LDHs and Liet al (Environmental Science and Pollution Research,2019,26(12):12014-12024) were prepared to have different amounts of adsorption of MgMnAl LDHs to As by co-precipitation. Let al. MgCl under nitrogen atmosphere by vigorous stirring₂·6H₂O、MnCl₂·4H₂O、AlCl₃·6H₂A mixed solution of O (Mg: Mn: Al molar ratio 2.9:1.1:2) was slowly added dropwise to the NaCl solution. The pH of the reaction solution was maintained at 9.5. + -. 0.2 by adjusting the dropping rate of the NaOH solution. Aging at 70 deg.C for 48h, and centrifuging; the adsorption quantity of the prepared MgMnAl LDHs to arsenic is 166.94mg g^-1。

The above embodiments are merely illustrative of the present invention, and not restrictive, and many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention, and it is intended that all such modifications and changes as fall within the true spirit of the invention and the scope of the claims be determined by those skilled in the art.

Claims

1. A process for producing a hydrotalcite-like compound, characterized in that,

comprises adding Ni²⁺、Co²⁺And Mn²⁺Adding an alkaline precipitator into the heavy metal wastewater, uniformly mixing, performing hydrothermal reaction, and separating and collecting precipitate to obtain the heavy metal wastewater;

wherein, the heavy metal wastewater contains (Ni)²⁺+Co²⁺)：Mn²⁺In a molar ratio of (0.5-5): 1, and the addition amount of the alkaline precipitator is to control the pH of the reaction system to be more than 8.

2. The production method according to claim 1,

the alkaline precipitator is one or more of sodium hydroxide, sodium carbonate, hexamethylene tetramine and urea, and is preferably urea.

3. The production method according to claim 1,

the heavy metal wastewater is one or more of ternary concentrated water, ternary fresh water and raw material washing water in the production of the lithium battery cathode material.

4. The production method according to any one of claims 1 to 3,

the temperature of the hydrothermal reaction is 80-200 ℃, preferably 100-150 ℃;

and/or the time of the hydrothermal reaction is 8-28h, preferably 18-23 h.

5. The production method according to any one of claims 1 to 4,

the alkaline precipitator is urea; and the addition of the urea is Ni in the heavy metal wastewater according to the amount of the substances²⁺、Co²⁺And Mn²⁺3-3.5 times of the sum ofPreferably 3.3 times.

6. The production method according to any one of claims 1 to 5,

comprises adding Ni²⁺、Co²⁺And Mn²⁺Adding urea into the heavy metal wastewater, stirring vigorously for 12-18min, transferring the obtained clear solution into a hydrothermal kettle, sealing, placing in an oven at 80-120 ℃ for hydrothermal reaction for 8-28h, cooling to room temperature after the reaction is finished, taking the precipitate, washing with deionized water, and finally drying at 75-85 ℃ for 10-15h to obtain the heavy metal wastewater.

7. The hydrotalcite-like compound obtained by the production process according to any one of claims 1 to 6.

8. The hydrotalcite-like compound according to claim 7, wherein the hydrotalcite-like compound is of a layered structure.

9. Use of the preparation process according to any one of claims 1 to 6 or the hydrotalcite-like compound according to any one of claims 7 to 8 for the removal of arsenic.

10. Use according to claim 9,

adjusting the pH value of the arsenic-containing wastewater to 3-11, then adding the hydrotalcite-like compound, carrying out constant-temperature oscillation reaction at 25-35 ℃, and removing by adsorption;

preferably, the addition amount of the hydrotalcite-like compound is 0.1-2 g/L;

further preferably, the reaction time is 15-30h, preferably 20-25 h.