Application of delta-MnO2 loaded active carbon material in heavy metal passivation repair
By infiltrating the agricultural and forestry waste powder in the manganese source aqueous solution and carbonizing it, a delta-type MnO2-loaded activated carbon material is formed, which solves the problems of long reaction time and secondary pollution in the prior art, and achieves an efficient, environmentally friendly and low-cost heavy metal passivation and repair effect.
Patent Information
- Application Number
- CN202311064857.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-23
- Publication Date
- 2025-02-25
AI Technical Summary
In the prior art, metal oxide-loaded activated carbon has a long reaction time, and strong acids or strong alkalis are often required to regulate, resulting in secondary pollution, which is not conducive to promotion and application.
By fully immersing the agricultural and forestry waste powder in the aqueous solution of manganese source, manganese crystallizes during the carbonization process to form delta-type MnO2, which is mainly loaded in activated carbon micropores and mesopores, and is loaded on the surface in a small amount, which significantly increases the specific surface area of activated carbon and the adsorption passivation active site.
It realizes δ-type MnO2-loaded activated carbon material with simple process, excellent adsorption performance, environmentally friendly and low-cost, significantly improves the adsorption passivation performance of activated carbon and is easy to promote and apply on a large scale.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of environmental restoration engineering, and in particular to the application of a delta-type manganese oxide-loaded activated carbon composite material in the passivation and restoration of heavy metals in soil. Background Art
[0002] Heavy metal pollution refers to the pollution effect of metal ions on the ecological environment. Heavy metal elements are not easily degraded and thus accumulate in the environment. After heavy metals enter the soil through atmospheric deposition, mining, and rivers, except for a small part absorbed by organisms and plants in the soil, most of the remaining are adsorbed by various organic and inorganic colloids and particulate matter in the soil, and then deposited in the soil through aggregation and sedimentation. Heavy metal pollutants mainly include lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), arsenic (As), nickel (Ni), copper (Cu), thallium (TI), etc. Due to the obvious advantages of metal oxide passivation adsorption, the metal oxide δ-type MnO2 was selected to prepare. δ-MnO2 is a mesoporous material with stable chemical properties. It has the advantages of high specific surface area and pore volume, many surface adsorption sites, narrow pore size distribution, regular pore structure, large and adjustable pore size, etc., and can be used as a good environmental remediation material.
[0003] As a major agricultural and forestry country, China is rich in agricultural and forestry wastes such as straw and "three wastes". The theoretical annual output of straw resources reaches more than 900 million tons. In line with the concept of high-quality development, straw and "three wastes" are used to prepare activated carbon, which has a high passivation effect and adsorption effect when used in soil remediation. However, since the surface functional groups, porosity and active sites of activated carbon obtained by direct carbonization are usually limited, its application is limited to a certain extent. Therefore, it is of great practical significance to modify activated carbon to improve its surface functional groups, porosity and active sites, which has become one of the current research hotspots.
[0004] Loading some metal oxides on the surface of activated carbon can effectively increase its surface functional groups and active sites, and improve the adsorption and passivation performance of activated carbon. However, the metal oxide loading process reported in related patents usually has a long reaction time, and most of them require strong acid or strong base to adjust, which is easy to cause secondary pollution and is not conducive to promotion and application. Summary of the invention
[0005] In view of the problems existing in the current existing technology, it is urgent to develop a metal oxide-loaded activated carbon with simple process, excellent adsorption performance, environmental friendliness, low cost, and easy large-scale promotion and application for the passivation and remediation of soil mercury.
[0006] In order to solve the above technical problems, the inventors have found that by fully soaking the powder of abandoned agricultural and forestry waste in a manganese source aqueous solution, the manganese fully soaked in the activated carbon during the carbonization process undergoes crystallization, evaporation of water molecules and volatilization of organic matter inside the straw, forming a large number of pore structures. At the same time, MnO2 reacts and transforms its crystal structure during the heating process to form a δ-type crystal, which is mainly loaded in the micropores and mesopores of the activated carbon and a small amount is loaded on the surface, significantly increasing the specific surface area of the activated carbon and the adsorption passivation active sites, thereby significantly improving the adsorption passivation performance of the activated carbon.
[0007] Specifically, the present invention proposes the following technical solutions: Specifically, the present invention proposes the following technical solutions:
[0008] On the one hand, the present invention provides a delta-type MnO2-loaded activated carbon composite material, wherein the MnO2 is delta-type and is mainly loaded in the micropores of the activated carbon and a small amount is loaded on the surface of the activated carbon.
[0009] The specific surface area of the MnO2-loaded activated carbon is 800.8~1527.3 m 2 ·g -1 , pore volume is 0.118~0.385cm 3 / g.
[0010] On the other hand, the present invention provides a method for preparing the above-mentioned δ-type MnO2-loaded activated carbon composite material, comprising crushing agricultural and forestry waste, screening, adding a manganese source aqueous solution to fully infiltrate, and then carbonizing to obtain the composite material.
[0011] Preferably, in the above-mentioned preparation method, the agricultural and forestry waste is any one of coconut shell, pine wood, oak, agricultural straw and a mixture thereof.
[0012] Preferably, in the above preparation method, the divalent manganese source is a divalent manganese salt selected from the group consisting of manganese sulfate, manganese nitrate, manganese acetate, and a mixture thereof.
[0013] Preferably, in the above-mentioned preparation method, the molar ratio of the manganese source aqueous solution KMnO4: divalent manganese source aqueous solution is 6-10:1, more preferably 6-8:1; and the mass ratio of delta-type MnO2 to straw powder is 1:(0.5-2.5).
[0014] Preferably, in the above-mentioned preparation method, the stirring rate of the manganese source aqueous solution KMnO4: divalent manganese source aqueous solution is 200 r / min, and the stirring time is 2~4h, and more preferably 4h.
[0015] Preferably, in the above-mentioned preparation method, the carbonization temperature is 300~800°C, more preferably 600~800°C; the heating rate is 8~12°C / min, more preferably 8~10°C / min; the carbonization time is 2~3h, the N2 flow rate is 40~100ml / min, and the vacuum degree of the tubular furnace is -0.4~-1MPa.
[0016] Preferably, the above preparation method does not involve treatment with strong acid or strong base.
[0017] On the other hand, the present invention provides an application of δ-MnO2-loaded activated carbon in the field of environmental remediation; preferably, it is applied to heavy metal ions in soil; further preferably, the heavy metal ions are one or more of mercury ions, arsenic ions, cadmium ions, and thallium ions.
[0018] The embodiment of the present invention also provides a soil mercury passivation remediation method, which comprises: adding δ-MnO2-loaded activated carbon to a soil system containing heavy metal ion mercury, so that the mercury ions in the soil are passivated by complexation or ion exchange.
[0019] In some embodiments, the added delta-MnO2-loaded activated carbon is added to the potting soil at a ratio of 1.5% (W biochar / W soil).
[0020] Compared with the prior art, the advantages of the present invention include: the δ-type MnO2-loaded activated carbon material of the present invention passivates and repairs heavy metal ions and has an adsorption function, and utilizes the material to specifically adsorb and passivate heavy metal ions, with a passivation removal rate of >63% for total mercury ions and a passivation removal rate of >78% for methylmercury ions.
[0021] The beneficial effects of the present invention include:
[0022] The invention provides a delta-type MnO2 loaded activated carbon with a simple preparation process, short reaction time, moderate reaction process conditions, no need for strong acid or alkali treatment, environmental friendliness, low cost, and easy industrialization and promotion. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The surface of the delta-type MnO2-loaded activated carbon prepared by the present invention has abundant functional groups and active sites, and can passivate heavy metal ions in soil through the combined action of precipitation, physical adsorption, ion exchange, and surface complexation, and has broad application prospects in the field of environmental adsorption engineering. Attached photos
[0024] Figure 1 and Figure 2 Implementation 3 and SEM photos
[0025] Figure 3 and Figure 4 SEM photos of implementation 4
[0026] Figure 5 and Figure 6 This is the SEM photo of Example 6 DETAILED DESCRIPTION
[0028] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.
[0029] Comparative Example 1
[0030] The activated carbon is prepared by crushing coconut shell, pine, oak, and agricultural straw waste and passing through a 50-mesh sieve; then 30 g of the sieved agricultural and forestry waste powder is placed in a tubular furnace quartz dish with a N2 flow rate of 50-100 ml / min, and the temperature is increased to 100°C at a heating rate of 5-10°C / min and kept warm for 1 hour, then increased to 1000°C at a heating rate of 5-10°C / min and kept warm for 2 hours, and then naturally cooled to obtain activated carbon.
[0031] Comparative Example 2
[0032] Weigh a certain ratio of KMnO4: divalent manganese source, mix and stir the two; transfer to a high-pressure hydrothermal autoclave, dry and keep warm; filter the resulting suspension, wash until the pH value no longer changes, and dry the resulting solid at 110°C overnight to obtain δ-MnO2 powder.
[0033] Example 1
[0034] Weigh a certain ratio of KMnO4: divalent manganese source, mix and stir the two; weigh a certain mass of AC and add it to the KMnO4: divalent manganese source mixed solution, stir and ultrasonicate, transfer to a high-pressure hydrothermal autoclave, dry and keep warm; filter the resulting suspension, wash until the pH value no longer changes, and dry the resulting solid at 110°C overnight to obtain δ-MnO2 / AC (hydrothermal synthesis) (T-AC).
[0035] Example 2
[0036] Weigh a certain ratio of KMnO4: divalent manganese source, mix and stir the two; weigh a certain mass of coconut shell (passed through a 50-mesh sieve) and add it to the KMnO4: divalent manganese source mixed solution, stir, ultrasonicate, transfer to a high-pressure hydrothermal autoclave, dry and keep warm; filter the resulting suspension, wash until the pH value no longer changes, and dry the resulting solid at 110°C overnight to obtain δ-MnO2 / coconut shell (M-AC-1)
[0037] Example 3
[0038] Weigh a certain ratio of KMnO4: divalent manganese source, mix and stir the two; weigh a certain mass of pine wood (passed through a 50-mesh sieve) and add it to the KMnO4: divalent manganese source mixed solution, stir, ultrasonicate, transfer to a high-pressure hydrothermal autoclave, dry and keep warm; filter the resulting suspension, wash until the pH value no longer changes, and dry the resulting solid at 110°C overnight to obtain δ-MnO2 / pine wood (C-AC-2)
[0039] Example 6
[0040] Take a certain ratio of δ-MnO2:AC, mix the two, adjust the pH of the mixed solution to about 4, stir, ultrasonicate, transfer to a high-pressure hydrothermal autoclave, dry, and keep warm; filter the resulting suspension, wash until the pH value no longer changes, and dry the resulting solid at 110°C overnight to obtain δ-MnO2 / AC (acidic synthesis) powder. (M-AC-2) Adsorption performance test
[0041] The total mercury content of rice roots was determined by cold atomic absorption spectrometry (CVAAS) using an F-732VJ instrument and stannous chloride (SnCl2) as the reagent. The specific method of the preliminary digestion treatment is as follows: accurately weigh 0.2 g of the sample (accurate to 0.0001 g), add 5 mL of nitric acid (HNO3), place the mixture in a 95°C water bath for digestion, take it out after 3 hours, and after the sample cools down, accurately fill it to 25 mL for testing.
[0042] The mercury content in rice stems, leaves and rice grains was directly measured using a mercury analyzer (Millestone DMA-80). According to the difference in mercury content in different parts of rice, the sample weight was 0.1-0.25 g (accurate to 0.0001 g).
[0043] Figure 1 , Figure 2 and Figure 3 , Figure 4 The SEM photos of Example 2 and Example 3 are shown in Table 1. The structural parameters of the activated carbon in the examples and the removal rate of total mercury in the soil are shown in Table 1. Figure 1 , Figure 2 It can be seen that δ-MnO2-loaded activated carbon has more abundant surface functional groups than pure activated carbon, and δ-MnO2 is mainly loaded in the micropores of activated carbon, with a small amount loaded on the surface (see Figure 3 , Figure 4). As shown in Table 1, δ-MnO2-loaded activated carbon has a relatively larger specific surface area and pore volume. By comparing the removal rate of activated carbon on total mercury in soil, it can be seen that different δ-MnO2 / AC have different passivation and repair capabilities for heavy metal mercury in solution. The removal rate of total mercury in soil by δ-MnO2 is 45%, and the removal rate of total mercury in soil by δ-MnO2 / AC (hydrothermal synthesis) is 63%.
[0044] In the above adsorption performance evaluation results, only the passivation and repair performance of modified activated carbon on mercury was listed; similar results were also found in the study of the adsorption performance of copper ions, arsenic ions, and thallium ions.
[0045] The above contents are only basic descriptions of the concept of the present invention, and any equivalent changes made according to the technical solution of the present invention shall fall within the protection scope of the present invention.
[0046] Table 1 Structural parameters of activated carbon and δ-MnO2-loaded activated carbon and their heavy metal adsorption performance in water Sample name <![CDATA[Specific surface area / m 2 / g]]> <![CDATA[Pore volume / cm 3 / g]]> Pore size (nm) Passivation removal rate of soil mercury ions / (%) <![CDATA[δ-MnO2]]> 16.546 0.253 21.920 45 M-AC-1 1219.428 0.251 26.965 58 M-AC-2 1527.372 0.385 18.321 63 C-AC 805.799 0.118 15.359 30 T-AC 807.863 0.127 15.429 44
Claims
1. A δ-MnO2-loaded activated carbon composite material, characterized in that: The δ-MnO2 is mainly loaded on the surface and micropores / mesopores of the activated carbon.
2. A method for preparing a δ-MnO2-loaded activated carbon composite material, characterized in that: The specific steps include: Step (1) After the activated carbon is crushed, it is passed through a 110-mesh sieve on a negative pressure sieve analyzer; Step (2) KMnO4 and a divalent manganese source are mixed in a certain proportion, stirred evenly, and then transferred to a tube furnace for drying and heat preservation; the resulting suspension is filtered and washed until the pH value no longer changes, and the resulting solid is dried at 110° C. overnight to obtain delta-type MnO2 powder.
3. Step (3) adding the sieved activated carbon powder into a manganese source aqueous solution, stirring, immersing, and ultrasonicating for a certain period of time, transferring to a supercritical reactor, heating, cooling, and washing until the pH remains unchanged; then placing the solid in a drying oven and drying to obtain a composite material.
4. A method for preparing the δ-type MnO2-loaded activated carbon composite material as claimed in claim 2, characterized in that: The agricultural and forestry waste in step (1) is any one of coconut shell, pine wood, fir wood, straw and a mixture thereof.
5. A δ-MnO2-loaded activated carbon composite material as claimed in claim 2, characterized in that: The divalent manganese source in step (2) is a divalent manganese salt, which is one of manganese sulfate, manganese nitrate, manganese acetate, or a mixture thereof.
6. A method for preparing the δ-type MnO2-loaded activated carbon composite material as claimed in claim 2, characterized in that: The manganese source aqueous solution in step (2) is KMnO4: divalent manganese solution, and the molar ratio of KMnO4: divalent manganese solution is 4-7.5:1; the mass ratio of delta-type MnO2 to agricultural and forestry waste powder is 1:(0.5-2.5).
7. A method for preparing the delta-type MnO2 material as claimed in claim 3, characterized in that: Step (2) δ-MnO2 is calcined in a tube furnace for 2-4 hours, the calcination temperature is set to 150-550°C, the heating rate is 2-5°C / min, and the temperature is naturally lowered.
8. A method for preparing the δ-type MnO2-loaded activated carbon composite material as claimed in claim 3, characterized in that: The carbonization temperature of step (3) is 300-800°C, the heating rate is 6-10°C / min, preferably 8-10°C / min; the carbonization time is 2-3h, the N2 flow rate is 40~100ml / min, and the vacuum degree of the tube furnace is -0.5~-1MPa.
9. Use of the δ-MnO2-loaded activated carbon composite material as described in any one of claims 1 to 2 or the δ-MnO2-loaded activated carbon material prepared by the preparation method described in any one of claims 3 to 7 in soil heavy metal passivation and remediation.
10. An application of the δ-type MnO2-loaded activated carbon composite material as claimed in claim 8 in soil heavy metal passivation and remediation, characterized in that: The heavy metal ions are one or more of mercury ions, arsenic ions, cadmium ions and thallium ions.