Iron-calcium double hydroxide modified charcoal as well as preparation method and application thereof

Abstract

The invention discloses iron-calcium double hydroxide modified biochar as well as a preparation method and application thereof, belongs to application of modified biochar in nonferrous metal mine wastewater, and discloses the preparation method of the iron-calcium double hydroxide modified biochar. Comprising the following steps: performing thermostatic reaction on a mixed solution containing calcium oxide, ferric chloride hexahydrate and biochar, filtering to obtain a precipitate, washing, drying, grinding and sieving to prepare the iron-calcium double hydroxide modified biochar, and the biochar is prepared from yak dung. The surface of the iron-calcium double hydroxide modified biochar provided by the invention contains rich functional groups, the iron-calcium double hydroxide modified biochar has good adsorption performance and good adsorption capacity to various heavy metals, when the concentration of Cu < 2 + >, Cd < 2 + > and Pb < 2 + > in a solution is 100 mg / L, the removal rate can reach 90.0% or above, and meanwhile, the dispersity of layered double hydroxides can be enhanced.

Description

TECHNICAL FIELD

[0001] The application belongs to the application of modified biochar in non-ferrous mine wastewater, in particular to an iron-calcium double hydroxide modified biochar and a preparation method and application thereof. BACKGROUND

[0002] Acidic wastewater generated by mine development has high concentrations of toxic metal elements, such as lead (Pb), cadmium (Cd) and copper (Cu) heavy metal pollutants, which pose a serious threat to water bodies and the surrounding environment. Tibet Autonomous Region has a large number of yaks, which can produce a large amount of cow dung. Yak dung is an easily accessible biomass resource, and its renewable nature meets the basic requirements of biomass raw materials, and can provide raw material support for related industries over a long period of time. Using yak dung, a low-cost and abundant high-quality biomass resource, to prepare biochar (BC) for the remediation of water body heavy metal pollution has also gradually attracted people's attention. However, some unmodified yak dung biochar in the literature performs poorly in terms of adsorption performance and stability, making it difficult to promote and apply.

[0003] Layered double hydroxides (LDH), commonly known as hydrotalcite, are a class of inorganic materials with unique layered structure. Its structure is composed of positively charged layer plates and interlayer anions. The layer plate is usually an octahedral structure formed by two or more +2 or +3 metal elements (such as Al 3+ , Fe 3+ , Ca 2+ and Mn 2+ , etc.) connected by hydroxyl (OH - ). It has high specific surface area and adsorption performance, good biocompatibility, and high ion exchange capacity. However, LDH has a certain aggregation tendency, which can significantly reduce its activity as an adsorbent. However, the combination of biochar and LDH can not only effectively improve the adsorption performance of biochar, but also significantly improve the dispersibility of LDH. Currently, the synthesis methods of LDH include coprecipitation, hydrothermal method, reverse micelle method and electrochemical method, etc. Among them, the most simple and commonly used coprecipitation method also has the shortcomings of harsh preparation conditions and high cost, which limits the large-scale application of LDH.

[0004] Therefore, it is a technical problem that needs to be solved by researchers in the field to develop a layered double metal hydroxide supported biochar material with simple process, low cost, easy industrialization and good properties. SUMMARY

[0005] In order to solve the above problems, the application provides a kind of iron calcium double hydroxide modified biochar and its preparation method and application.Overcome the defect that the solution pH is too cumbersome in the process of preparing LDH by coprecipitation method in the past.The iron calcium double hydroxide modified biochar provided by the application has high adsorption efficiency and large adsorption capacity, and can be used as an adsorbent to remove heavy metal ions in water, thereby purifying water quality and protecting water resources.

[0006] One of the technical solutions provided by the application is:

[0007] A preparation method of iron calcium double hydroxide modified biochar includes the following steps: a mixed solution containing calcium oxide, ferric chloride hexahydrate and biochar is subjected to constant temperature reaction, and the precipitate is obtained by filtration, washing, drying, grinding and sieving to prepare the iron calcium double hydroxide modified biochar, and the biochar is prepared from yak dung.

[0008] Further, the molar ratio of calcium oxide to ferric chloride hexahydrate is (3-4) : 1, and the ratio of biochar to the total mass of calcium oxide and ferric chloride hexahydrate is (3-6) : 1.

[0009] The reason for limiting the molar ratio of calcium oxide to ferric chloride hexahydrate to (3-4) : 1 is that the usual method for generating layered double hydroxide by coprecipitation is to add two metal salt compounds to the solution at the same time, and the pH of the solution is adjusted to 10-11 by using lye. In the application, CaO reacts with water to generate Ca(OH)2, and Ca(OH)2 reacts with FeCl3 to generate Fe(OH)3. By limiting the molar ratio of calcium oxide to ferric chloride hexahydrate to (3-4) : 1, the pH of the solution during the process can be maintained between 10 and 11, meeting the preparation conditions of layered double hydroxide, without the need for additional lye. Since the solubility of calcium hydroxide generated by the reaction of calcium oxide with water is low, in order to ensure that there are enough hydroxyl ions to continuously dissociate to maintain the pH of the solution at 10-11 during the reaction process, the amount of substance of calcium oxide needs to be greater than that of ferric chloride hexahydrate (molar ratio (3-4) : 1). In this way, after the reaction with FeCl3 to generate Fe(OH)3, there is still un-dissolved calcium oxide in the mixed solution, which can continue to react with water to generate Ca(OH)2, thereby stably providing the alkaline environment required for the reaction. CaO reacts with water to generate Ca(OH)2, Ca(OH)2 reacts with FeCl3 to generate Fe(OH)3, and then double metal hydroxide is loaded on the surface of biochar.

[0010] Further, the temperature of the constant temperature reaction is 60-80℃, and the time is 12-24h.

[0011] Further, the preparation method of the biochar comprises the following steps: crushing and sieving the naturally air-dried yak dung, placing the obtained yak dung powder in a tubular furnace reactor, pyrolyzing under N2 atmosphere, washing to neutral, drying and grinding, to obtain the biochar.

[0012] Further, the specific operation of the pyrolysis is: heating to 500℃ at 10℃ / min, and the residence time is 2h.

[0013] The second technical solution provided by the present application is:

[0014] The iron-calcium double hydroxide modified biochar prepared by the above preparation method.

[0015] The third technical solution provided by the present application is:

[0016] The application of the above iron-calcium double hydroxide modified biochar in removing heavy metal ions in water.

[0017] The fourth technical solution provided by the present application is:

[0018] A method for removing heavy metal ions in water, which uses the above iron-calcium double hydroxide modified biochar as an adsorbent to adsorb and remove heavy metal contaminated wastewater.

[0019] Further, the pH value of the heavy metal contaminated wastewater is 3-6; the concentration of metal ions in the heavy metal contaminated wastewater is 10mg / L-400mg / L; and the adsorption time is 10-120min.

[0020] Further, the metal ions include Cu 2+ , Cd 2+ and Pb 2+ .

[0021] Compared with the prior art, the present application has the following advantages and technical effects:

[0022] The present application realizes the recycling of waste and reduces the preparation cost of the iron-calcium double hydroxide modified biochar by pyrolyzing yak dung as biomass to obtain biochar; the present application uses the method of coprecipitation to prepare the iron-calcium double hydroxide modified biochar, which does not need to add additional alkali solution to adjust the pH, and the process is simple and easy to operate; the surface of the iron-calcium double hydroxide modified biochar provided by the present application contains rich functional groups, has good adsorption performance, and has good adsorption capacity for various heavy metals; when the concentration of Cu 2+ , Cd 2+ and Pb 2+ in the solution is 100mg / L, the removal rate can reach more than 90.0%, and the dispersibility of the layered double hydroxide can be enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0024] Figure 1 Scanning electron microscope images of the iron calcium double hydroxide modified biochar and the original biochar prepared in Example 1, (a) and (b) are scanning electron microscope images of the iron calcium double hydroxide modified biochar, (c) and (d) are scanning electron microscope images of the original biochar;

[0025] Figure 2 X-ray diffraction patterns of the iron calcium double hydroxide modified biochar and the original biochar prepared in Example 1;

[0026] Figure 3 Fourier transform infrared spectrograms of the iron calcium double hydroxide modified biochar and the original biochar prepared in Example 1. DETAILED DESCRIPTION

[0027] The various illustrative embodiments of the present application will now be described in detail in connection with the accompanying drawings. This description is made for illustrative purposes only and is not intended to limit the application. It is understood that the detailed description and specific examples, while indicating certain embodiments of the application, are intended for purposes of illustration only and are not intended to limit the scope of the application.

[0028] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. Additionally, it is to be understood that the use of any numerical range recited herein includes every number within that range, including the end points, unless specifically stated otherwise. Each intermediate range recited herein is included within the scope of the application. The upper and lower limits of these intermediate ranges can be independently included or excluded.

[0029] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In the case of conflict between the present specification and any document incorporated herein by reference, the present specification will control.

[0030] Many modifications and variations to the illustrative embodiments described herein will be apparent to those of ordinary skill in the art from the foregoing description. Such modifications and variations are intended to fall within the scope of the present application. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0031] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or list of materials.

[0032] The embodiment of the present application provides a preparation method of iron calcium double hydroxide modified biochar, and specifically comprises the following steps:

[0033] (1) The collected yak dung is naturally air-dried;

[0034] (2) The air-dried yak dung is crushed in a pulverizer, and then is dried at room temperature and stored after being screened through a 40-mesh sieve;

[0035] (3) Yak dung powder is weighed and placed in a quartz boat, the quartz boat is placed in a tube furnace reactor, pyrolysis is carried out under N2 atmosphere, the pyrolysis product is washed to neutral, dried, ground and screened to prepare biochar, which is stored in a centrifuge tube for standby;

[0036] (4) CaO and FeCl3·6H2O are weighed and placed in different glass containers, and are ultrasonically dissolved in H2O for standby, and are called A liquid (CaO solution) and B liquid (FeCl3 solution);

[0037] (5) Biochar powder is weighed and ultrasonically dispersed in H2O to prepare a suspension, which is called C liquid;

[0038] (6) The C liquid is moved to a constant-temperature water bath, and a cantilever electric stirrer is used for stirring, after the stirring starts, the A liquid and the B liquid are simultaneously added to the C liquid to obtain a mixed liquid;

[0039] (7) The mixed liquid obtained in step (6) is moved to a forced air drying oven for constant-temperature modification, filtration is carried out to obtain a precipitate, and the precipitate is washed, dried, dried, ground and screened to obtain iron calcium double hydroxide modified biochar, which is packaged for standby;

[0040] In some preferred embodiments of the present application, the temperature of pyrolysis in step (3) is 400-600℃, the heating rate is 10℃ / min, the heating time is 1h, and the reaction is carried out for 2h after heating to 500℃.

[0041] In some preferred embodiments of the present application, the molar ratio of CaO to FeCl3·6H2O in step (4) is (3-4) : 1.

[0042] In some preferred embodiments of the present application, the ratio of the total mass of the biochar to calcium oxide and iron chloride hexahydrate in step (5) is (3-6):1.

[0043] In some preferred embodiments of the present application, the temperature of the blast drying oven in step (7) is 60-80℃, the drying time is 12-24h, and after grinding, the product is sieved through a 100-mesh sieve, and the cleaning liquid can be H2O or ethanol.

[0044] The present application provides a preparation method of iron-calcium double hydroxide modified biochar, which is simple in process, low in cost, easy to industrialize, and has good properties.

[0045] The room temperature of the present application refers to 25±2℃.

[0046] Example 1: A preparation method of iron-calcium double hydroxide modified biochar

[0047] S1. The yak dung is naturally air-dried, and after air-drying, the yak dung is crushed in a pulverizer, sieved through a 40-mesh sieve, and then stored under room temperature drying conditions. 10g of yak dung powder is weighed in a quartz boat and placed in a tube furnace reactor, pyrolyzed under N2 atmosphere, heated to 500℃ at a heating rate of 10℃ / min, and the residence time is 2h. Biochar is prepared, washed with deionized water until neutral, dried, ground, and sieved (100 mesh) to obtain biochar powder, which is stored in a centrifuge tube for later use.

[0048] S2. 0.015mol of CaO (0.84g) and 0.005mol of FeCl3·6H2O (1.351g) are weighed separately and dissolved in 100mL of H2O in different glass containers. After ultrasonic dissolution, they are stored for later use, and are referred to as A liquid and B liquid, respectively.

[0049] S3. 10g of the biochar powder prepared in S1 is ultrasonically dispersed in 300ml of H2O to form a suspension, which is referred to as C liquid. The C liquid is moved to a constant temperature water bath, the temperature is set to 70℃, and a cantilever electric stirrer is used for stirring. After the stirring starts, A liquid and B liquid are simultaneously added to the C liquid, and the stirring time is 2h. The mixed liquid is moved to a 70℃ blast drying oven for constant temperature modification for 12h, filtered to obtain a precipitate, which is dried after washing with deionized water, and then dried, ground, and sieved (100 mesh) to prepare the iron-calcium double hydroxide modified biochar.

[0050] Figure 1 The scanning electron microscope images of the iron-calcium double hydroxide modified biochar prepared in Example 1 and the original biochar are shown in (a) and (b), and the scanning electron microscope images of the original biochar are shown in (c) and (d). From the images, it can be seen that the iron-calcium double hydroxide modified biochar has a more uniform particle size and better dispersion than the original biochar. Figure 1It can be seen from the figure that the original biochar surface is smooth and has obvious pore structure. The dense iron calcium double hydroxide is loaded on the surface of the biochar, and at the same time presents a layered structure. Compared with the original biochar, the surface of the iron calcium double hydroxide modified biochar becomes rough, and its specific surface area is increased, thereby providing more adsorption sites for the adsorption of heavy metals.

[0051] Figure 2 The X-ray diffraction patterns of the iron calcium double hydroxide modified biochar and the original biochar prepared in Example 1 are shown in the figure. The XRD pattern of the original biochar shows that the characteristic peaks of SiO2 are observed at 20.86°, 29.37° and 60.03°, which correspond to the crystal faces (101), (111) and (311) respectively. This may be due to the fact that the yak dung contains a large amount of silicon element. In the pattern of the iron calcium double hydroxide modified biochar, there are sharp characteristic peaks at 11.26°, 26.61°, 30.21° and 40.26°, which correspond to (003), (006), (110) and (116) of the layered double hydroxide, indicating that the iron calcium double hydroxide is successfully loaded on the biochar.

[0052] Figure 3 The Fourier transform infrared spectra of the iron calcium double hydroxide modified biochar and the original biochar prepared in Example 1 are shown in the figure. Figure 3 It can be seen from the figure that the wide peak appearing at 3421.6 cm -1 is attributed to the stretching vibration of -OH, the absorption peak at 2927.3 cm -1 is caused by the symmetric and asymmetric stretching vibration of aliphatic hydrocarbon or naphthenic hydrocarbon -CH3 and -CH2, the peak at 1617.8 cm -1 corresponds to C=C group, the peak at 1414.1 cm -1 corresponds to -COOH group, and the absorption peak at 662.8 cm -1 can be attributed to the lattice vibration of double hydroxide. These specific functional group structures positively promote the adsorption of heavy metals.

[0053] Application Example 1

[0054] The iron calcium double hydroxide modified biochar prepared in Example 1 is applied to the treatment of wastewater containing heavy metals copper, cadmium and lead under different pH conditions, and the specific steps are as follows:

[0055] Cu(NO3)2, Cd(NO3)2 and Pb(NO3)2 are weighed, and four mixed solutions of Cu 2+ , Cd 2+ and Pb 2+ are prepared (wherein Cu 2 + , Cd 2+ and Pb 2+concentrations of 100 mg / L), and the pH of the mixed solutions of Cu 2+ , Cd 2+ and Pb 2+ was adjusted to 3.0, 4.0, 5.0 and 6.0 using 0.1 mol / L nitric acid solution and 0.1 mol / L sodium hydroxide solution, respectively. 30 mg of the iron-calcium double hydroxide modified biochar prepared in Example 1 was taken in a 50 mL centrifuge tube, and 30 mL of the mixed solution of Cu 2+ , Cd 2+ and Pb 2+ was added. After oscillation at 20 ± 1 °C for 24 h, the sample was taken, filtered using a 0.45 μm water system filter membrane, and the concentrations of Cu 2+ , Cd 2+ and Pb 2+ in the filtrate were determined using an inductively coupled plasma emission spectrometer. The removal rates of the heavy metal ions by the iron-calcium double hydroxide modified biochar are shown in Table 1.

[0056] Table 1

[0057] pH 3 4 5 6 Cu 2+ Removal rate (%)]] 96.6 96.9 99.7 99.8 Cd 2+ Removal rate (%)]] 85.6 84.7 96.8 97.6 Pb 2+ Removal rate (%)]] 99.7 99.6 99.5 99.4

[0058] As shown in Table 1, the iron-calcium double hydroxide modified biochar prepared in the application has little effect on the adsorption of Cu 2+ , Pb 2 + under different pH conditions, has a certain effect on the adsorption of Cd 2+ under low pH, but the removal rate of the adsorption of Cd 2+ can still reach 85.6%.

[0059] Application Example 2

[0060] The iron-calcium double hydroxide modified biochar prepared in Example 1 was applied to wastewater treatment of heavy metals copper, cadmium and lead with different concentrations. The specific steps are as follows:

[0061] Cu(NO3)2, Cd(NO3)2 and Pb(NO3)2 were weighed, respectively, to prepare six mixed solutions of Cu 2+ , Cd 2+ and Pb 2+ with different concentrations (10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 400 mg / L), and 0.1 mol / L nitric acid solution and 0.1 mol / L sodium hydroxide solution were used to adjust the pH of Cu 2+ , Cd 2+ , Pb 2+The pH of the mixed solutions was 5.0 ± 0.1. Six 30 mg portions of the iron-calcium double hydroxide modified biochar prepared in Example 1 were placed in 50 mL centrifuge tubes, and 30 mL of Cu at different concentrations was added to each tube. 2+ Cd 2+ Pb 2+ The mixed solution was incubated at 20±1℃ for 24 hours, then sampled and filtered through a 0.45μm aqueous filter membrane. The Cu content in the filtrate was determined using inductively coupled plasma atomic emission spectrometry. 2+ Cd 2+ Pb 2+ The removal rates of heavy metal ions by iron-calcium double hydroxide modified biochar at the specified concentrations are shown in Table 2.

[0062] Table 2

[0063]

[0064] As shown in Table 2, with the increase of the initial concentration, Cu 2+ Cd 2+ The adsorption removal rate of Pb showed a decreasing trend, but the adsorption removal rate of Pb... 2+ It can still maintain a high adsorption and removal rate.

[0065] Application Example 3

[0066] The effect of adsorption time on the adsorption of heavy metals copper, cadmium, and lead by the iron-calcium double hydroxide modified biochar prepared in Example 1 was investigated. The specific steps are as follows:

[0067] Weigh out Cu(NO3)2, Cd(NO3)2 and Pb(NO3)2 respectively, and prepare Cu 2+ Cd 2+ and Pb 2+ A mixed solution (in which Cu 2+ Cd 2+ and Pb 2+ The concentrations of all solutions were 100 mg / L. Cu was adjusted using 0.1 mol / L nitric acid solution and 0.1 mol / L sodium hydroxide solution. 2+ Cd 2+ and Pb 2+ The pH of the mixed solution was 5.0. 30 mg of the iron-calcium double hydroxide modified biochar prepared in Example 1 was weighed and placed in a 50 mL centrifuge tube. 30 mL of the above-mentioned Cu was added. 2+ Cd 2+ and Pb 2+The mixed solution was shaken at 20±1℃ for 10 min, 30 min, 60 min, 120 min, 360 min, 720 min, and 1440 min, and then sampled. The sample was filtered with a 0.45 μm water filter membrane, and the concentrations of Cu 2+ , Cd 2+ , and Pb 2+ in the filtrate were determined by inductively coupled plasma emission spectrometry. The removal rates of heavy metal ions by the iron-calcium double hydroxide modified biochar are shown in Table 3.

[0068] Table 3

[0069]

[0070] As shown in Table 3, with the extension of the adsorption time, the adsorption removal rates of Cu 2+ , Cd 2+ , and Pb 2+ by the iron-calcium double hydroxide modified biochar increased, and when the adsorption time reached 120 min, the adsorption removal rates all reached more than 90%, and tended to be stable after 360 min.

[0071] Example 2

[0072] S1. The same as in Example 1;

[0073] S2. The same as in Example 1, except that 0.020 mol of CaO and 0.005 mol of FeCl3·6H2O were respectively weighed.

[0074] S3. The same as in Example 1.

[0075] Comparative Example 1

[0076] S1. The yak dung was naturally air-dried, and then crushed in a crusher after air-drying. The crushed yak dung was dried at room temperature and stored after being sieved through a 40-mesh sieve. 10 g of the yak dung powder was weighed in a quartz boat, and then placed in a tube furnace reactor for pyrolysis under a N2 atmosphere. The temperature was raised to 400℃ at a heating rate of 10℃ / min, and the residence time was 2 h. The biochar was obtained, washed with deionized water until neutral, dried, ground, and sieved (100 mesh) to obtain biochar powder, which was stored in a centrifuge tube for use.

[0077] S2. 0.015 mol of CaO and 0.005 mol of FeCl3·6H2O were respectively weighed and placed in different glass containers, and then dissolved in 100 ml of H2O. After ultrasonic dissolution, the solution was used as A liquid (CaO solution) and B liquid (FeCl3 solution).

[0078] S3. Take 5 g of the biochar powder prepared in S1, and disperse in 300 ml of H2O by ultrasonic to prepare a suspension, which is referred to as C liquid. The C liquid is placed in a constant temperature water bath, and the temperature is set to 60 DEG C. An electrically driven stirrer is used for stirring. After the stirring starts, the A liquid and the B liquid are simultaneously added to the C liquid. The stirring time is 2 h. The mixed liquid is placed in a 60 DEG C air drying oven for constant temperature modification for 24 h. Filtration is performed to obtain a precipitate. The precipitate is washed by deionized water and dried. Drying, grinding and sieving (100 mesh) are performed to prepare the calcium-iron double hydroxide modified biochar.

[0079] Comparative Example 2

[0080] S1. The yak dung is naturally air-dried. After air-drying, the yak dung is crushed in a crusher, sieved through a 40 mesh sieve, and then stored in a sealed container under normal temperature and dry conditions. 10 g of the yak dung powder is weighed in a quartz boat, and placed in a tube furnace reactor for pyrolysis under a N2 atmosphere. The temperature is raised to 600 DEG C at a rate of 10 DEG C / min, and the residence time is 2 h. The biochar is obtained, washed by deionized water until neutral, dried, ground, and sieved (100 mesh) to obtain biochar powder, which is stored in a centrifuge tube for later use.

[0081] S2. 0.015 mol of CaO and 0.005 mol of FeCl3·6H2O are respectively weighed and placed in different glass containers, and dissolved in 100 ml of H2O. After ultrasonic dissolution, the solutions are stored for later use, which are referred to as A liquid (CaO solution) and B liquid (FeCl3 solution).

[0082] S3. 5 g of the biochar powder prepared in S1 is weighed, and dispersed in 300 ml of H2O by ultrasonic to prepare a suspension, which is referred to as C liquid. The C liquid is placed in a constant temperature water bath, and the temperature is set to 80 DEG C. An electrically driven stirrer is used for stirring. After the stirring starts, the A liquid and the B liquid are simultaneously added to the C liquid. The stirring time is 2 h. The mixed liquid is placed in an 80 DEG C air drying oven for constant temperature modification for 16 h. Filtration is performed to obtain a precipitate. The precipitate is washed by deionized water and dried. Drying, grinding and sieving (100 mesh) are performed to prepare the calcium-iron double hydroxide modified biochar.

[0083] Comparative Example 3

[0084] S1. The same as in Example 1.

[0085] S2. The same as in Example 1, except that 0.010 mol of CaO and 0.005 mol of FeCl3·6H2O are respectively weighed.

[0086] S3. The same as in Example 1.

[0087] The modified biochar prepared in Example 2 and Comparative Examples 1-3 is subjected to adsorption performance testing. The testing conditions are pH = 5, Cu 2+Cu, Cd and Pb 2+ Cu, Cd and Pb 2+ The concentration of the three heavy metals in the mixed solution was 100 mg / L, and the adsorption time was 120 min. The test results are shown in Table 4.

[0088] Table 4

[0089] Cu 2+ Removal rate (%)]]> Cd 2+ Removal (%)]]> Pb 2+ Removal rate (%)]] Example 2 97.3 92.8 99.1 Comparative Example 1 88.7 90.6 99.3 Comparative Example 2 83.4 51.7 99.6 Comparative Example 3 91.2 80.3 99.3

[0090] As can be seen from Table 4, comparing Example 1, Comparative Example 1 and Comparative Example 2, the removal rates of Cu, Cd and Pb in Example 1 are all higher than those in Comparative Example 1 and Comparative Example 2, which may be related to the preparation temperature of the biochar. The biochar prepared at the temperature of Example 1 has higher porosity and more abundant surface functional groups, which is beneficial to the adsorption of heavy metals. Since too little CaO is added in Comparative Example 3, the removal rates of Cu, Cd and Pb in Comparative Example 3 are obviously lower than those in Example 1. 2+ 2+ 2+ 2+

[0091] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed by the present application can be easily thought by those skilled in the art, which should be covered in 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 iron calcium double hydroxide modified biochar, characterized in that, The preparation method comprises the following steps: The mixed solution containing calcium oxide, ferric chloride hexahydrate and biochar is subjected to constant temperature reaction, and the precipitate is obtained by filtration, washing, drying, grinding and sieving to prepare the iron-calcium double hydroxide modified biochar, wherein the biochar is prepared from yak dung.

2. The production method according to claim 1, characterized by, The molar ratio of the calcium oxide to the ferric chloride hexahydrate is (3-4) : 1, and the ratio of the biochar to the total mass of the calcium oxide and the ferric chloride hexahydrate is (3-6) :

1.

3. The preparation method according to claim 1, characterized in that, The constant temperature reaction is carried out at a temperature of 60-80 ℃ for 12-24 h.

4. The production method according to claim 1, characterized by, The preparation method of the biochar comprises the following steps: the naturally air-dried yak dung is crushed and sieved, the obtained yak dung powder is placed in a tube furnace reactor, pyrolysis is carried out under N2 atmosphere, the obtained product is washed to neutral, and the product is dried and ground to obtain the biochar.

5. The preparation method according to claim 4, characterized in that, The pyrolysis is carried out by heating at a rate of 10 ℃ / min to 500 ℃, and the residence time is 2 h.

6. The iron-calcium double hydroxide modified biochar prepared by the preparation method of any one of claims 1-5.

7. The iron-calcium double hydroxide modified biochar according to claim 6 is used for removing heavy metal ions in water.

8. Use according to claim 7, wherein the heavy metal ions comprise Cu 2+ , Cd 2+ and Pb 2+ .

9. A method for removing heavy metal ions from water, characterized by, The heavy metal contaminated wastewater is adsorbed and removed by using the iron-calcium double hydroxide modified biochar according to claim 6 as an adsorbent.

10. The method of removing heavy metal ions from water according to claim 9, wherein, The pH value of the heavy metal contaminated wastewater is 3-6, the concentration of metal ions in the heavy metal contaminated wastewater is 10-400 mg / L, and the adsorption time is 10-120 min.

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