Magnesium-based hydrotalcite for treating multi-metal co-pollution as well as preparation and application of magnesium-based hydrotalcite

Abstract

The invention relates to the technical field of water and soil remediation, in particular to magnesium-based hydrotalcite for treating multi-metal co-pollution as well as preparation and application of the magnesium-based hydrotalcite. The magnesium-based hydrotalcite laminate is customized by regulating and controlling trivalent metal elements and object interlayer anions of the magnesium-based hydrotalcite host laminate, the trivalent metal elements are one of Al (III), Fe (III) and the like, and the object interlayer anions are one of CO3 < 2->, NO3 <-> and the like. Preferably, the magnesium-based hydrotalcite is MgAl-CO3, MgAl-NO3, MgFe-CO3 or MgFe-NO3, and the magnesium-based hydrotalcite is a magnesium-based hydrotalcite or magnesium-based hydrotalcite. The LDHs-based material can mineralize heavy metal ions in an ultra-stable manner, and is suitable for rapidly, efficiently, stably and simultaneously removing various heavy metals, and mineralized products have extremely low Ksp (about 10-50), so that secondary pollution caused by secondary dissolution of the heavy metals is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of water body and soil remediation, and in particular to a magnesium-based hydrotalcite for treating multi-metal co-pollution, and a preparation method and application thereof. Background Art

[0002] Soil is a precious resource that nourishes life on Earth and is essential not only for food production but also for a sustainable future for humanity. In recent years, with the development of urbanization and industrialization around the world, industries such as lead and zinc smelters, tanneries, and mining plants have generated a large amount of heavy metal pollution, including cadmium (Cd(II)), lead (Pb(II)), and arsenic (mainly As(V)), which show high toxicity, non-biodegradability, and environmental durability. Due to natural deposition and various anthropogenic activities, multiple heavy metals gradually accumulate in ecological cycles and are enriched in water bodies and / or soil. The absorption of multiple heavy metals by crops not only reduces yields but also causes irreversible damage to humans. Therefore, it is crucial to develop appropriate remediation technologies for water and soil contaminated by coexisting Cd(II), Pb(II), and As(V).

[0003] At present, various technologies have been applied to treat water and soil contaminated by heavy metals, such as electrochemistry, elution, membrane separation, phytoremediation and soil replacement. Considering the cost, efficiency, product stability and durability of the remediation technology, the in-situ mineralization method shows great promise in treating multiple heavy metal pollution in water and soil. By adding in-situ mineralizers to the contaminated water and soil, the occurrence state of heavy metals can be changed from a free state to a mineralized state, reducing toxicity without causing secondary pollution.

[0004] It has been reported that various types of mineralizers can be used for heavy metal removal, such as metal oxides, nano-zero-valent iron (nZVI), activated carbon, metal-organic frameworks (MOFs), etc. Among them, layered double hydroxides (LDHs), defined as a class of inorganic two-dimensional nanomaterials with brucite-like laminates, have gradually attracted the attention of researchers recently because their unique layered structure allows multiple interactions between host laminates and guest anions, resulting in excellent mineralization performance for single heavy metals.

[0005] However, considering the different existence states and physicochemical properties of heavy metal cations and anions, the “trade-off” effect makes it difficult to remove heavy metals such as Cd(II), Pb(II) and As(V) simultaneously. Specifically, Cd(II) and Pb(II) can be removed as Cd(II), Pb(II) and As(V) at low pH values. 2+ and Pb 2+ It exists in the form of high mobility and toxicity, which is consistent with the alkaline environment of CdCO 3 、Cd(OH) 2 and / or Pb3 (CO 3 ) 2 (OH) 2 As for As(V), AsO 4 3- It has high mobility and toxicity, and is more toxic than H under acidic conditions (relatively low pH values). 2 AsO 4 - The state of occurrence is more active and dangerous. Therefore, the co-contamination of heavy metal cations and anions cannot be treated simultaneously using mineralizers with a single adsorption site. This "trade-off" effect makes it extremely challenging to simultaneously remove coexisting heavy metal cations and anions. Therefore, the development of a single suitable mineralizer that can efficiently and cost-effectively remediate multiple heavy metal pollution has attracted widespread interest in science and industry. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a magnesium-based hydrotalcite for treating multi-metal co-pollution and its preparation and application.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A magnesium-based hydrotalcite for treating multi-metal co-pollution, wherein the magnesium-based hydrotalcite is customized according to the complex working conditions of multi-metal anion and cation co-existence pollution by regulating the trivalent metal element of the main layer of magnesium-based hydrotalcite (Mg based LDHs) and the guest interlayer anion, wherein the trivalent metal element is one of Al(III), Fe(III), etc., and the guest interlayer anion is CO 3 2- 、NO 3 - One of the above.

[0009] Preferably, the magnesium-based hydrotalcite is MgAl-CO 3 , the preparation comprises the following steps:

[0010] Weigh 2.18 g Mg(NO 3 ) 2 6H 2 O and 1.60g Al(NO 3 ) 3 9H 2 O was dissolved in 25 mL of deionized water to obtain solution A;

[0011] Weigh 4.0g NaOH and 10.75g Na 2 CO 3 Dissolve in 100 mL of deionized water to obtain solution B;

[0012] Add 50 mL of deionized water to a three-necked flask, and slowly drop solution B (about 1-2 drops) thereinto until the pH thereof is adjusted to about 10, to obtain solution C;

[0013] At 65°C, a peristaltic pump with a drop rate of 16 was used to drop solution A into solution C, and solution B was added dropwise to maintain the pH of the system at about 10. Magnetic stirring was used to keep the solution uniformly dispersed in the process;

[0014] When the solution A was added dropwise, the reaction was terminated quickly, the precipitated product was obtained by centrifugation and washed with deionized water 3 times and ethanol once, and the product was placed in an oven at 60°C to dry.

[0015] Preferably, the magnesium-based hydrotalcite is MgAl-NO 3 , the preparation comprises the following steps:

[0016] Weigh 1.0 g MgAl-CO 3 Dispersed in 90 mL of methanol, at room temperature and with N 2 The mixture was stirred under magnetic stirring for 6 h to obtain solution A;

[0017] Take 616 μL of concentrated nitric acid and dilute it into 10 mL of methanol, then quickly add it dropwise to solution A, and continue magnetic stirring for 6 hours; centrifuge to obtain the precipitated product and wash it twice with methanol. Place the product in a 60°C oven to dry before use.

[0018] Preferably, the magnesium-based hydrotalcite is MgFe-CO 3 , the preparation comprises the following steps:

[0019] Weigh 9.24 g Mg(NO 3 ) 2 6H 2 O and 4.85g Fe(NO 3 ) 3 9H 2 O was dissolved in 160 mL of deionized water to obtain solution A;

[0020] Weigh 1.92g NaOH and 5.08g Na 2 CO 3 Dissolve in 160 mL of deionized water to obtain solution B;

[0021] Solutions A and B were added to the colloid mill at a constant pouring speed, and the rotation speed was maintained at 4000 rpm / min for 2 min. After the reaction was completed and cooled to room temperature, the precipitated product was obtained by centrifugation and washed with deionized water 3 times and ethanol once. The product was placed in an oven at 60°C to dry for later use.

[0022] Preferably, the magnesium-based hydrotalcite is MgFe-NO 3 , the preparation comprises the following steps:

[0023] Weigh 1.0 g MgFe-CO 3 Dispersed in 90 mL of methanol, at room temperature and with N 2 The mixture was stirred under magnetic stirring for 6 h to obtain solution A;

[0024] Take 616 μL of concentrated nitric acid and dilute it into 10 mL of methanol, and quickly add it dropwise to solution A, and continue magnetic stirring for 6 hours; centrifuge to obtain the precipitated product and wash it twice with methanol, and place the product in a 60°C oven to dry for later use.

[0025] The magnesium-based hydrotalcite for treating multi-metal co-pollution described in the present invention can be used to treat the co-existence pollution of Cd(II), Pb(II) and As(V) in soil, and can in-situ mineralize the co-existence of Cd(II), Pb(II) and As(V) in the soil.

[0026] The magnesium-based hydrotalcite for treating multi-metal co-pollution described in the present invention can be used to treat the co-existing Cd(II), Pb(II) and As(V) pollution in water bodies, and can in-situ mineralize the co-existing Cd(II), Pb(II) and As(V) in water bodies.

[0027] Compared with other types of mineralizers (metal oxides, nano zero-valent iron (nZVI), activated carbon, metal organic framework (MOF)), the LDHs-based materials of the present invention can ultra-stable mineralize heavy metal ions, and are suitable for rapid, efficient and stable simultaneous removal of multiple heavy metals, and the mineralized products have extremely low K sp (about 10 -50 ) to avoid the re-dissolution of heavy metals and secondary pollution.

[0028] Compared with the single metal hydroxide (Mg(OH) 2 It has stronger acid resistance and a wider pH range of applicable working conditions, and is suitable for simultaneously treating coexisting multi-metal anions and cations with a "trade-off" effect.

[0029] Magnesium is an important component of chlorophyll. In the process of simultaneous mineralization of multiple metals, Mg(II) in the MgAl / MgFe-LDHs of the present invention will be slowly released into the soil, and over time Mg(II) will gradually migrate to the roots, stems, and even leaves of the plants, thereby promoting the growth of red bean seedlings, pea seedlings, and other plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 MgAl-CO 3 and MgAl-NO 3 XRD and FT-IR characterization diagrams.

[0032] Figure 2 MgFe-CO 3 and MgFe-NO 3 XRD and FT-IR characterization diagrams.

[0033] Figure 3 For the use of MgAl-NO 3 Effect diagram of treating different concentrations of coexisting Cd(II), Pb(II) and As(V) in water.

[0034] Figure 4 For the use of MgFe-CO 3 With MgFe-NO 3 Effect diagram of treating the coexistence of Cd(II), Pb(II) and As(V) in water.

[0035] Figure 5 For the use of MgAl-NO 3 Effect diagram of treating the coexistence of Cd(II), Pb(II) and As(V) in soil.

[0036] Figure 6 For the use of MgFe-CO 3 With MgFe-NO 3 Effect diagram of treating the coexistence of Cd(II), Pb(II) and As(V) in soil.

[0037] Figure 7 For the use of MgAl-NO 3 A picture showing the effect of a plant cultivation experiment on the treated co-contaminated soil.

[0038] Figure 8 For the use of MgFe-CO 3 With MgFe-NO 3 A picture showing the effect of a plant cultivation experiment on the treated co-contaminated soil. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0040] Example 1

[0041] MgAl-CO 3 Preparation

[0042] Weigh 2.18 g Mg(NO 3 ) 2 6H 2 O and 1.60g Al(NO 3 ) 3 9H 2 O was dissolved in 25 mL of deionized water to obtain solution A; 4.0 g of NaOH and 10.75 g of Na 2 CO 3 Dissolve in 100 mL of deionized water to obtain solution B; add 50 mL of deionized water to a three-necked flask, and slowly drip solution B until its pH is adjusted to about 10 to obtain solution C; at 65°C, use a peristaltic pump with a drip rate of 16 to drip solution A into solution C, and at the same time drip solution B to maintain the system pH at about 10, wherein the process uses magnetic stirring to keep the solution uniformly dispersed; after the dripping is completed, centrifuge to obtain the precipitated product and wash it with deionized water 3 times and ethanol once. The product is placed in a 60°C oven to dry.

[0043] Example 2

[0044] MgAl-NO 3 Preparation

[0045] Weigh 1.0 g MgAl-CO 3 Dispersed in 90 mL of methanol, at room temperature and with N 2 The mixture was stirred under magnetic stirring for 6 h to obtain solution A. 616 μL of concentrated nitric acid was diluted to 10 mL of methanol and quickly added to solution A for 6 h. The precipitate was obtained by centrifugation and washed twice with methanol. The product was dried in an oven at 60 °C for later use.

[0046] Example 3

[0047] MgFe-CO 3 Preparation

[0048] Weigh 9.24 g Mg(NO 3 ) 2 6H2 O and 4.85g Fe(NO 3 ) 3 9H 2 O was dissolved in 160 mL of deionized water to obtain solution A. Weigh 1.92 g of NaOH and 5.08 g of Na 2 CO 3 Dissolve in 160 mL of deionized water to obtain solution B. Add solutions A and B to the colloid mill at a constant pouring speed and keep the speed at 4000 rpm / min for 2 minutes. After the reaction is completed and cooled to room temperature, centrifuge to obtain the precipitated product and wash it with deionized water 3 times and ethanol once. Place the product in a 60°C oven to dry and set aside.

[0049] Example 4

[0050] MgFe-NO 3 Preparation

[0051] Weigh 1.0 g MgFe-CO 3 Dispersed in 90 mL of methanol, at room temperature and with N 2 The mixture was stirred under magnetic stirring for 6 h to obtain solution A. 616 μL of concentrated nitric acid was diluted to 10 mL of methanol and quickly added to solution A for 6 h. The precipitate was obtained by centrifugation and washed twice with methanol. The product was dried in an oven at 60 °C for later use.

[0052] like Figure 1-Figure 2 As shown, XRD and FT-IR characterizations can prove that Example 1, Example 2, Example 3, and Example 4 successfully synthesized MgAl-CO 3 、MgAl-NO 3 MgFe-CO 3 With MgFe-NO 3 .

[0053] Application Example 1

[0054] Coexistence of Cd(II), Pb(II) and As(V) in in situ mineralized water

[0055] According to 1.0 g L -1 Take an appropriate amount of MgAl-CO prepared in Example 3 、MgAl-NO 3 MgFe-CO 3 、MgFe-NO 3 The samples were dispersed into aqueous solutions containing different amounts of Cd(II), Pb(II) and As(V) (the initial concentration of each ion was 5 mg L -1 , 10mg L -1, 15mg L -1 and 20 mg L -1 ), a water polymetallic mineralization experiment was conducted at room temperature for different time periods. At regular intervals, 0.5-2 mL of the suspension was extracted and immediately filtered through a 0.22 μm filter membrane. The contents of Cd, Pb, As and Mg in the solution were analyzed using ICP-OES.

[0056] result:

[0057] The ICP-OES test results show that for Cd(II), Pb(II) and As(V) coexisting in water, the use of MgAl-NO 3 Within 24 hours, the removal rate of the above three heavy metals can reach more than 95%, and the use of MgFe-CO 3 With MgFe-NO 3 The synchronous mineralization effect is better, and the efficient removal rate of the above three heavy metals can reach more than 99% within 4 hours.

[0058] Application Example 2

[0059] Coexistence of Cd(II), Pb(II) and As(V) in in situ mineralized soils

[0060] At room temperature, 50.0 g of contaminated soil samples were mixed with different masses of MgAl-CO 3 、MgAl-NO 3 MgFe-CO 3 With MgFe-NO 3 (dosage is 0.5% to 4%), and then the soil mixture was fully mixed with deionized water at a ratio of 50.0 g to 40 mL for a 2-week soil dynamics experiment, during which magnetic stirring was maintained. About 3.0 g of soil samples were collected every 2 to 3 days and dried at 60 ° C for 12 h. CaCl 2 The available Cd, Pb and As in the samples were extracted by the buffered DPTA extraction method, and their concentrations were determined by ICP-OES.

[0061] result:

[0062] The results of a two-week soil dynamics experiment showed that the use of MgAl-NO 3 The removal rates of Cd(II), Pb(II) and As(V) were 79.25%, 64.75% and 62.00% respectively. 3 With MgFe-NO 3 The removal rates of three effective heavy metals, Cd(II), Pb(II) and As(V), all exceeded 80%.

[0063] In summary, the magnesium-based hydrotalcite of the present invention can simultaneously achieve ultrastable mineralization of three effective heavy metals, namely Cd(II), Pb(II) and As(V), and can be used to treat the coexisting Cd(II), Pb(II) and As(V) pollution in water or soil.

[0064] Application Example 3

[0065] Plant cultivation experiment

[0066] MgAl-CO 3 、MgAl-NO 3 MgFe-CO 3 With MgFe-NO 3 The results showed that: Figure 7-Figure 8 As shown, MgAl-CO 3 、MgAl-NO 3 MgFe-CO 3 With MgFe-NO 3 The simultaneous mineralization of multiple metals is accompanied by the dissolution of Mg(II), which gradually migrates to the roots, stems, and even leaves of the plants, thereby promoting the growth of plants such as red bean seedlings and pea seedlings.

[0067] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A magnesium-based hydrotalcite for treating multi-metal co-pollution, characterized in that: The magnesium-based hydrotalcite is customized according to the complex working conditions of coexistence of multiple metal anions and cations, by regulating the trivalent metal elements of the main layer of the magnesium-based hydrotalcite and the guest interlayer anions, wherein the trivalent metal element is Al (III) or Fe (III), and the guest interlayer anions are CO3 2- or NO3 - .

2. The magnesium-based hydrotalcite for treating multi-metal co-pollution according to claim 1, characterized in that: The magnesium-based hydrotalcite is one of MgAl-CO3, MgAl-NO3, MgFe-CO3 and MgFe-NO3.

3. A method for preparing a magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: The steps include: Weigh 2.18 g of Mg(NO3)2·6H2O and 1.60 g of Al(NO3)3·9H2O and dissolve them in 25 mL of deionized water to obtain solution A; Weigh 4.0 g NaOH and 10.75 g Na2CO3 and dissolve them in 100 mL deionized water to obtain solution B; Add 50 mL of deionized water into a three-necked flask, and slowly dropwise add solution B thereto until the pH thereof is adjusted to 10, to obtain solution C; At 65°C, a peristaltic pump was used to drop solution A into solution C, and solution B was added dropwise to maintain the pH of the system at 10. Magnetic stirring was used to keep the solution uniformly dispersed in the process; After the addition of solution A was completed, the reaction was terminated, the precipitated product was obtained by centrifugation and washed with deionized water three times and ethanol once, and the product was placed in an oven at 60°C to dry.

4. A method for preparing a magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: The steps include: Weigh 1.0 g of MgAl-CO3 and disperse it in 90 mL of methanol. Maintain the mixture under magnetic stirring for 6 h at room temperature and with N2 flowing to obtain solution A. Take 616 μL of concentrated nitric acid and dilute it into 10 mL of methanol, then quickly add it dropwise to solution A and continue magnetic stirring for 6 h; The precipitated product was obtained by centrifugation and washed twice with methanol, and then dried in an oven at 60°C.

5. A method for preparing a magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: The steps include: Weigh 9.24 g of Mg(NO3)2·6H2O and 4.85 g of Fe(NO3)3·9H2O and dissolve them in 160 mL of deionized water to obtain solution A; Weigh 1.92 g NaOH and 5.08 g Na2CO3 and dissolve them in 160 mL deionized water to obtain solution B; Add solution A and solution B into the colloid mill along the inner wall at the same time, and keep the speed at 4000 rpm / min for 2 minutes; After the reaction was completed and cooled to room temperature, the precipitated product was obtained by centrifugation and washed with deionized water three times and ethanol once, and the product was placed in an oven at 60°C to dry.

6. A method for preparing a magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: The steps include: Weigh 1.0 g of MgFe-CO3 and disperse it in 90 mL of methanol. Maintain the mixture under magnetic stirring for 6 h at room temperature and with N2 flowing to obtain solution A. Take 616 μL of concentrated nitric acid and dilute it into 10 mL of methanol, then quickly add it dropwise to solution A and continue magnetic stirring for 6 h; The precipitated product was obtained by centrifugation and washed twice with methanol, and then dried in an oven at 60°C.

7. The use of magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: Used to control soil pollution caused by the co-existence of Cd(II), Pb(II) and As(V).

8. The use according to claim 7, characterized in that: For in situ mineralization of coexisting Cd(II), Pb(II) and As(V) in soils.

9. The use of magnesium-based hydrotalcite for treating multi-metal co-pollution according to any one of claims 1 to 2, characterized in that: Used to treat Cd(II), Pb(II) and As(V) pollution coexisting in water bodies.

10. The use according to claim 9, characterized in that: Used for in situ mineralization of coexisting Cd(II), Pb(II) and As(V) in water bodies.

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