A reductive hydrothermal biochar adsorption material with carbon microsphere surface for treating technetium and preparation method thereof

Abstract

The present invention belongs to the field of nuclear energy environmental protection technology, and specifically relates to a reducing hydrothermal biochar adsorption material with a carbon microsphere surface for treating technetium and a preparation method thereof. The preparation method comprises the following steps: 1) washing the biomass raw material, drying it, crushing it, and sieving it; 2) adding the crushed and sieved biomass raw material to an organic acid solution at a certain solid-liquid ratio to obtain a hydrothermal reaction feed; 3) subjecting the hydrothermal reaction feed to a hydrothermal reaction, cooling it to room temperature, filtering it, washing the solid phase, and drying it to obtain a reducing hydrothermal biochar adsorption material with a carbon microsphere surface for treating technetium. The present invention uses low-cost waste biomass as raw material, uses green organic acid for modification, and obtains a reducing hydrothermal biochar adsorption material with a carbon microsphere surface for treating technetium through a simple one-step hydrothermal method, which can be used as an efficient and clean adsorbent for adsorbing and separating heptavalent technetium.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear energy environmental protection, and in particular relates to a technetium-treated reducing hydrothermal biochar adsorption material with a carbon microsphere surface and a preparation method thereof. Background Art

[0002] Energy, as an important material basis for human survival and development, plays a vital role in all aspects of economic and social development. For a long time, my country's energy consumption has mainly come from fossil energy. With the development of the economy, people's demand for energy has continued to increase, making non-renewable fossil energy gradually facing depletion, so it is necessary to seek an alternative energy source. Nuclear energy has the advantages of high energy density and stable power generation, and has stronger economic competitiveness and substitution capacity compared to other non-fossil energy sources. However, with the development of nuclear energy, a large number of difficult-to-handle radioactive nuclides will inevitably be produced. Among these radioactive nuclides, technetium is mainly in the form of heptavalent pertechnetate (TcO4 - ) form, it has extremely high environmental mobility. Once leakage occurs, technetium can easily migrate in groundwater, be absorbed by plants and enter the food chain, thereby increasing the risk of human cancer and leukemia. Therefore, it is of great significance to separate technetium from radioactive nuclear waste liquid. The materials that have been developed for separating technetium include layered hydroxides, metal organic frameworks, ion exchange resins and biochar. Among them, biochar materials have the advantages of wide range of raw materials and low prices, and can be used as adsorbents to adsorb and separate heavy metal ions in solutions. Hydrothermal biochar is a biochar material prepared by hydrothermal carbonization, which has the advantages of economy, sustainability and simple preparation. However, unmodified hydrothermal biochar has the disadvantage of low technetium removal rate. Increasing the adsorption capacity of hydrothermal biochar on technetium by modification and using it to treat technetium-containing waste liquid is of great significance to the development of nuclear energy. Summary of the invention

[0003] In order to improve the adsorption performance of technetium, the purpose of the present invention is to provide a reducing hydrothermal biochar adsorption material with a carbon microsphere surface for treating technetium and a preparation method thereof.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface, comprising the following steps:

[0006] 1) Wash the biomass raw materials, dry them, crush and sieve them, and collect the biomass particles;

[0007] 2) adding biomass particles into an organic acid solution at a certain solid-liquid ratio to obtain a hydrothermal reaction feed;

[0008] 3) subjecting the hydrothermal reaction feed to a hydrothermal reaction, cooling to room temperature, filtering, solid phase washing, and drying to obtain a reducing hydrothermal biochar adsorption material having a carbon microsphere surface for treating technetium;

[0009] The biomass raw material is one or two of sawdust, pine wood, rice husk, corn stalk, bamboo shoot husk, and willow wood;

[0010] The particle size of the biomass particles ranges from 150 to 300 μm;

[0011] The organic acid is one or more of oxalic acid, lactic acid, glycolic acid, and malic acid;

[0012] The solid-liquid ratio is 1g:1~10ml;

[0013] The concentration of the organic acid solution is 0.01-10 mol / L;

[0014] The temperature of the hydrothermal reaction is 150-260° C. and the time is 1-10 hours.

[0015] A reducing hydrothermal biochar adsorption material prepared by the above preparation method.

[0016] The above-mentioned reducing hydrothermal biochar adsorption material is used for the adsorption and separation of technetium.

[0017] The above-mentioned reducing hydrothermal biochar adsorption material is used for reducing heptavalent technetium.

[0018] The significant advantages of the present invention are:

[0019] (1) The present invention uses a one-step hydrothermal method, biomass as raw material, and an environmentally friendly organic acid to obtain a reductive hydrothermal biochar adsorption material with a carbon microsphere surface treated with technetium. This technology has the advantages of mild reaction, environmental friendliness and low cost.

[0020] (2) The surface of the reductive hydrothermal biochar adsorption material with a carbon microsphere surface treated with technetium prepared by the present invention is mainly composed of highly active reductive carbon microspheres, so that the surface of the material has a larger reductive active surface area and a stronger electron exchange capacity.

[0021] (3) The reducing hydrothermal biochar adsorption material with a carbon microsphere surface provided by the present invention can be used to adsorb and separate heptavalent technetium with an adsorption capacity of 383 mg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cyclic voltammetric characteristic curve diagram of the reducing hydrothermal biochar with carbon microsphere surface prepared in Example 1 and the unmodified hydrothermal biochar prepared in Comparative Example 1.

[0023] Figure 2 This is a scanning electron microscope image of the hydrothermal biochar prepared in Example 1.

[0024] Figure 3 This is a scanning electron microscope image of the hydrothermal biochar prepared in Comparative Example 1.

[0025] Figure 4 1 is the adsorption equilibrium curve of the hydrothermal biochar prepared in Example 1 and the hydrothermal biochar prepared in Comparative Example 1. DETAILED DESCRIPTION

[0026] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0027] Example 1

[0028] A method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface is carried out according to the following steps:

[0029] (1) Wash the bamboo shoot shells, dry them at 60°C, and then crush them. Pass them through a 60-mesh sieve and collect the bamboo shoot shell particles with a particle size of 180-250 μm.

[0030] (2) Take 5 g of bamboo shoot shell particles and add them into 30 mL of 1.2 mol / L lactic acid solution to obtain a hydrothermal reaction feed.

[0031] (3) The hydrothermal reaction feed was transferred to a hydrothermal reactor, and the hydrothermal reaction was carried out at 200°C for 6 h. The reaction was cooled to room temperature, filtered, and the solid phase was washed with deionized water until neutral. The solid phase was then dried at 80°C for 8 h to obtain a reducing hydrothermal biochar adsorption material having carbon microspheres with a particle size range of 0.5 to 5 μm on the surface.

[0032] Comparative Example 1

[0033] A method for preparing unmodified hydrothermal biochar is carried out according to the following steps:

[0034] (1) Wash the bamboo shoot shells, dry them at 60°C, and then crush them. Pass them through a 60-mesh sieve and collect the bamboo shoot shell particles with a particle size of 180-250 μm.

[0035] (2) Take 5 g of bamboo shoot shell particles and add them into 30 mL of deionized water to obtain a hydrothermal reaction feed.

[0036] (3) The hydrothermal reaction feed was transferred to a hydrothermal reactor, and the hydrothermal reaction was carried out at 200 °C for 6 h. The reaction was cooled to room temperature, filtered, and the solid phase was washed with deionized water until neutral. The solid phase was then dried at 80 °C for 8 h to obtain unmodified hydrothermal biochar.

[0037] Figure 1The cyclic voltammetric characteristic curves of the hydrothermal biochar prepared in Example 1 and the hydrothermal biochar prepared in Comparative Example 1 are shown in FIG. As can be seen from the figure, the reducing property of the hydrothermal biochar prepared in Example 1 is stronger than that of the hydrothermal biochar prepared in Comparative Example 1.

[0038] Figure 2 This is a scanning electron microscope image of the hydrothermal biochar prepared in Example 1. Its surface is mainly composed of carbon microspheres with a particle size range of 0.5-5 μm.

[0039] Figure 3 This is a scanning electron microscope image of the hydrothermal biochar prepared in Comparative Example 1. Its surface is mainly composed of large fragment structures.

[0040] Figure 4 The adsorption equilibrium curves of the hydrothermal biochar prepared in Example 1 and the hydrothermal biochar prepared in Comparative Example 1 are shown. The technetium adsorption capacity of the hydrothermal biochar prepared in Example 1 is significantly increased by about 58% compared with that of the hydrothermal biochar prepared in Comparative Example 1.

[0041] Application Example 1

[0042] The reductive hydrothermal biochar adsorption material with carbon microsphere surface prepared in Example 1 and the unmodified hydrothermal biochar adsorption material prepared in Comparative Example 1 were subjected to adsorption experiments, as follows:

[0043] Preparation of heptavalent technetium solution: Take 0.1817 g of ammonium pertechnetate and prepare 1 g / L technetium stock solution in a 100 mL volumetric flask. Take an appropriate amount of technetium stock solution and dilute to the required concentration.

[0044] 0.009 g of reduced hydrothermal biochar with carbon microsphere surface was added to a solution with a pH of 1 and an initial concentration of heptavalent technetium of 200-400 mg·L -1 The adsorption was carried out for 36 h at 30 °C and 130 rpm. The maximum adsorption of technetium was 383 mg / g after adsorption equilibrium. 0.009 g of unmodified hydrothermal biochar was added to a solution with a pH of 1 and an initial technetium concentration of 200-400 mg·L -1 The adsorption was carried out in a solution at 30°C and 130 rpm for 36 hours, and the adsorption amount of heptavalent technetium was measured. The maximum adsorption amount of technetium after adsorption equilibrium was 243 mg / g.

[0045] Application Example 2:

[0046] The valence distribution of technetium adsorbed on the surface of the reducing hydrothermal biochar adsorption material having the surface of carbon microspheres in Application Example 1 was characterized, and the characterization results are shown in the following table:

[0047]

[0048] The results show that the adsorption mechanism of technetium by the reducing hydrothermal biochar adsorption material with a carbon microsphere surface is a redox mechanism. After adsorption, the proportion of tetravalent technetium on the surface of the material is as high as 90.05%, indicating that the reducing hydrothermal biochar adsorption material with a carbon microsphere surface has a strong reduction activity and can reduce heptavalent technetium to tetravalent technetium.

[0049] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface, characterized in that: The following steps are involved: 1) Wash the biomass raw materials, dry them, crush and sieve them, and collect the biomass particles; 2) adding biomass particles into an organic acid solution at a certain solid-liquid ratio to obtain a hydrothermal reaction feed; 3) subjecting the hydrothermal reaction feed to a hydrothermal reaction, cooling to room temperature, filtering, solid phase washing, and drying to obtain a reducing hydrothermal biochar adsorption material having a carbon microsphere surface for treating technetium; The biomass raw material is bamboo shoot shells; The organic acid is lactic acid; The concentration of the organic acid solution is 0.01-10 mol / L.

2. The method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface according to claim 1, characterized in that: The particle size of the biomass particles ranges from 150 to 300 μm.

3. The method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface according to claim 1, characterized in that: The solid-liquid ratio is 1g:1~10ml.

4. The method for preparing a reducing hydrothermal biochar adsorption material having a carbon microsphere surface according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 150-260° C. and the time is 1-10 hours.

5. A reducing hydrothermal biochar adsorption material prepared by the preparation method according to claim 1.

6. Use of the reducing hydrothermal biochar adsorption material as claimed in claim 5 in the adsorption and separation of technetium.

7. Use of the reducing hydrothermal biochar adsorption material as claimed in claim 5 in reducing heptavalent technetium.

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