Cobalt-loaded walnut shell biochar as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to cobalt-loaded walnut shell biochar as well as a preparation method and application thereof. In the invention, transition metal cobalt (Co) is rich in electron configuration, can realize circulation of Co < 2 + > / Co < 3 + > after being activated by persulfate, and is an element for efficiently generating. SO4 < 2->. Cobalt is loaded on a biochar carrier to construct a heterogeneous catalyst, cobalt ions can be effectively prevented from being dissolved out, the stability of the catalyst is improved, meanwhile, the large specific surface area, the abundant pore structure and surface functional groups of biochar can provide additional adsorption sites and electron transfer channels, and the biochar and cobalt active sites generate a synergistic catalytic effect. According to the preparation method, resource utilization of agricultural and forestry waste walnut shells can be achieved, the production cost is reduced, meanwhile, the specific surface area and active sites of the cobalt-loaded walnut shell biochar can be greatly increased, and TBBPA in wastewater can be efficiently degraded.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a cobalt-supported walnut shell biochar, its preparation method, and its application. Background Technology

[0002] Tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame retardants, is extensively used in electronics, textiles, and building materials. Its production, use, and electronic waste disposal processes generate large quantities of TBBPA-containing wastewater. Due to its environmental persistence, bioaccumulation, and endocrine-disrupting toxicity, TBBPA poses a serious threat to aquatic ecosystems and human health. Therefore, the development of efficient and sustainable TBBPA wastewater treatment technologies is urgently needed.

[0003] There are various methods for removing TBBPA from wastewater, mainly including physical adsorption, biodegradation, and advanced oxidation technologies. Among these, methods based on sulfate radicals (·SO4) are particularly effective. 2- In Fenton-like advanced oxidation technology, SO4 2- With a longer half-life, wider pH range, and higher redox potential than hydroxyl radicals (·OH), homogeneous Fenton-like systems exhibit significant advantages in the degradation of TBBPA. However, these systems suffer from inherent drawbacks such as secondary pollution caused by metal ion dissolution and difficulties in catalyst recovery. Therefore, there is an urgent need to develop a highly efficient, stable, and heterogeneous catalytic material capable of generating reactive oxygen species with high redox potentials for the efficient degradation of TBBPA. Summary of the Invention

[0004] The purpose of this invention is to provide a cobalt-loaded walnut shell biochar, its preparation method, and its application. The cobalt-loaded walnut shell biochar obtained by the method provided by this invention can efficiently degrade TBBPA.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing cobalt-supported walnut shell biochar, comprising the following steps: Walnut shells are pyrolyzed to obtain walnut shell biochar; The walnut shell biochar and activator are mixed and then pyrolyzed to obtain activated biochar. The activated biochar was impregnated in a cobalt-source organic solution and then subjected to pyrolysis to obtain the cobalt-loaded walnut shell biochar.

[0006] Preferably, the pyrolysis temperature is 300~500℃, the holding time is 3~5h, and the heating rate is 5~10℃ / min.

[0007] Preferably, the activator includes at least one of potassium hydroxide and sodium hydroxide; The mass ratio of the walnut shell biochar and the activator is 1-3:1.

[0008] Preferably, the temperature of the pyrolysis activation is 600-800℃, the holding time is 3-5h, and the heating rate is 5-10℃ / min.

[0009] Preferably, the cobalt source organic solution comprises a cobalt source and an organic solvent; the cobalt source comprises at least one of cobalt acetylacetonate, cobalt chloride and cobalt nitrate; and the organic solvent comprises at least one of tetrahydrofuran, 2-methyltetrahydrofuran and 1,4-dioxane. The mass ratio of the activated biochar and the cobalt source is 5-15:1-3. The use amount ratio of the activated biochar and the organic solvent is 1g:90-110mL.

[0010] Preferably, the impregnation is carried out under stirring, and the impregnation time is 14-18h.

[0011] Preferably, the temperature of the pyrolysis treatment is 600-800℃, the holding time is 3-5h, and the heating rate is 5-10℃ / min. The pyrolysis treatment is carried out in a protective atmosphere.

[0012] The application further provides the cobalt-loaded walnut shell biochar prepared by the preparation method.

[0013] Preferably, the mass percentage content of the cobalt is 5-15%.

[0014] The application further provides the application of the cobalt-loaded walnut shell biochar in the treatment of tetrabromobisphenol A wastewater.

[0015] The application provides a preparation method of cobalt-loaded walnut shell biochar, comprising the following steps: pyrolyzing walnut shells to obtain walnut shell biochar; mixing the walnut shell biochar and an activator, and performing pyrolysis activation to obtain activated biochar; impregnating the activated biochar in a cobalt source organic solution, and then performing pyrolysis treatment to obtain the cobalt-loaded walnut shell biochar.

[0016] In the application, the transition metal cobalt (Co) has rich electronic configuration, and can realize the cycle of Co 2+ / Co 3+ after being activated by persulfate, and is efficient in generating ·SO4 2-The cobalt is loaded on the biochar carrier to construct a heterogeneous catalyst, which can effectively prevent the dissolution of cobalt ions and improve the stability of the catalyst, and the large specific surface area, rich pore structure and surface functional groups of the biochar can also provide additional adsorption sites and electron transfer channels, and produce a synergistic catalytic effect with the cobalt active site. The preparation method provided by the application not only realizes the resource utilization of the agricultural and forestry waste walnut shell and reduces the production cost, but also greatly improves the specific surface area and active sites of the cobalt-loaded walnut shell biochar, and efficiently degrades TBBPA in wastewater.

[0017] The preparation method provided by the application is simple, does not require a functional and complex material preparation device, has low production and preparation requirements, and does not produce polluting by-products throughout the process, in line with the concept of green preparation. The output of the cobalt-loaded walnut shell biochar is large, which is conducive to industrial application. The cobalt-loaded walnut shell biochar obtained has the characteristics of large specific surface area, many active sites and high catalytic activity, and greatly improves the treatment efficiency of tetrabromobisphenol A wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The XRD characterization graph of the cobalt-loaded walnut shell biochar obtained in Example 1 is shown in the figure; Figure 2 The Raman characterization graph of the cobalt-loaded walnut shell biochar obtained in Example 1 is shown in the figure; Figure 3 The EPR characterization graph of the cobalt-loaded walnut shell biochar obtained in Example 1 is shown in the figure. DETAILED DESCRIPTION

[0019] The application provides a preparation method of cobalt-loaded walnut shell biochar, comprising the following steps: Pyrolyzing the walnut shell to obtain walnut shell biochar; Mixing the walnut shell biochar and an activating agent, and performing pyrolysis activation to obtain activated biochar; After the activated biochar is immersed in a cobalt source organic solution, pyrolysis treatment is performed to obtain the cobalt-loaded walnut shell biochar.

[0020] In the application, the walnut shell is pyrolyzed to obtain walnut shell biochar.

[0021] In the application, before pyrolysis, the walnut shell is preferably pretreated, and the pretreatment comprises cleaning, drying and sieving treatment. In the application, the cleaning is preferably washing 3-5 times with ultrapure water; the temperature of the drying is preferably 70 DEG C, and the time is preferably 6-8 h; and the mesh size of the screen used in the sieving treatment is preferably 60 mesh.

[0022] In the present application, the temperature of the pyrolysis is preferably 300-500℃, and can be specifically 300℃, 400℃, or 500℃; the holding time is preferably 3-5h, and can be specifically 3h, 4h, or 5h; the heating rate is preferably 5-10℃ / min, and can be specifically 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; the pyrolysis is preferably performed in a protective atmosphere, and the protective atmosphere is preferably high-purity nitrogen; and the pyrolysis is further followed by cooling to room temperature.

[0023] After obtaining the walnut shell biochar, the walnut shell biochar and an activating agent are mixed in the present application, pyrolysis activation is performed, and activated biochar is obtained.

[0024] In the present application, the activating agent preferably comprises at least one of potassium hydroxide and sodium hydroxide; and the mass ratio of the walnut shell biochar to the activating agent is preferably 1-3:1, and can be specifically 1:1, 2:1, or 3:1. In the present application, the mixing is preferably performed under grinding, and the grinding is further preferably followed by sieving; and the mesh size of the sieve used in the sieving is preferably 60 mesh. In the present application, the temperature of the pyrolysis activation is preferably 600-800℃, and can be specifically 600℃, 700℃, or 800℃; the holding time is preferably 3-5h, and can be specifically 3h, 4h, or 5h; the heating rate is preferably 5-10℃ / min, and can be specifically 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; the pyrolysis activation is preferably performed in a protective atmosphere, and the protective atmosphere is preferably high-purity nitrogen; and the pyrolysis activation is further preferably followed by cooling to room temperature, washing, and drying.

[0025] After obtaining the activated biochar, the activated biochar is impregnated in a cobalt source organic solution in the present application, and pyrolysis treatment is performed, and the cobalt-loaded walnut shell biochar is obtained.

[0026] In the present application, the cobalt source preferably comprises at least one of cobalt acetylacetonate, cobalt chloride, and cobalt nitrate; the organic solvent preferably comprises at least one of tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane; the mass ratio of the activated biochar to the cobalt source is preferably 5-15:1-3; and the usage ratio of the activated biochar to the organic solvent is preferably 1g:90-110mL. In the present application, the impregnation is preferably performed under stirring, and the impregnation time is preferably 14-18h; and the impregnation is further preferably followed by sequentially performing filtration, washing, drying, grinding, and sieving through a 60-mesh sieve; the washing is preferably sequentially performed 3-5 times using ultrapure water and once using ethanol; and the drying temperature is preferably 70℃, and the time is preferably 6-8h.

[0027] In the present application, the temperature of the pyrolysis treatment is preferably 600-800℃, and can be specifically 600℃, 700℃ or 800℃; the holding time is preferably 3-5h, and can be specifically 3h, 4h or 5h; the heating rate is preferably 5-10℃ / min, and can be specifically 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min; the pyrolysis treatment is preferably carried out in a protective atmosphere, and the protective atmosphere is preferably high-purity nitrogen; and the pyrolysis treatment is preferably followed by cooling to room temperature.

[0028] The present application also provides a cobalt-loaded walnut shell biochar prepared by the preparation method described in the above technical solution, which comprises walnut shell biochar and cobalt loaded on the walnut shell biochar. In the present application, the mass percentage content of the cobalt is preferably 5-15%.

[0029] The present application also provides the application of the cobalt-loaded walnut shell biochar described in the above technical solution in the treatment of tetrabromobisphenol A wastewater.

[0030] Unless otherwise specified, the materials and equipment used in the present application are commercially available in the art.

[0031] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Embodiment 1 The walnut shell is washed with ultrapure water for 2-3 times to remove soluble impurities, and then is placed in a 70℃ drying box for drying for 6h. After drying, the walnut shell is sieved through a 60-mesh sieve, and the particle size of-60 mesh accounts for 100%. The sieved walnut shell 5g is placed in a tube furnace for pyrolysis, the pyrolysis rate is 5℃ / min, the pyrolysis time is 4h, the pyrolysis temperature is 400℃, high-purity nitrogen is passed through the whole process to keep the furnace in an oxygen-free state, and the pyrolysis is cooled to room temperature after completion, to obtain walnut shell biochar; The 3g walnut shell biochar and 3g KOH solid are mixed and ground through a 60-mesh sieve, and then are placed in a tube furnace for activation pyrolysis, the pyrolysis rate is 5℃ / min, the pyrolysis time is 4h, the pyrolysis temperature is 700℃, high-purity nitrogen is passed through the whole process to keep the furnace in an oxygen-free state, and the pyrolysis is cooled to room temperature after completion, washed and dried, to obtain activated biochar; 0.5 g of activated biochar and 0.1 g of cobalt acetylacetonate were added to 90 mL of tetrahydrofuran, and after stirring for 16 h, the precipitate was filtered, washed with ultrapure water for 3-5 times, washed with ethanol once, and then placed in a 70°C drying oven for drying for 6 h, ground and passed through a 60 mesh sieve; the obtained material was placed in a tube furnace for pyrolysis treatment, the pyrolysis rate was 5°C / min, the pyrolysis temperature was 700°C, and the pyrolysis time was 4 h, and high-purity nitrogen was passed through the whole process to keep the furnace oxygen-free, and after cooling to room temperature, cobalt-loaded walnut shell biochar was obtained, wherein the mass percentage of cobalt loading was 10%.

[0033] The cobalt-loaded walnut shell biochar obtained was tested for performance: 0.01 g of cobalt-loaded walnut shell biochar was added to 100 mL of 50 mg / L tetrabromobisphenol A solution with pH=8, 9, and 10, respectively, for adsorption and degradation experiments, 0.2 g / L PMS was added after 5 min of adsorption for degradation reaction, and after 30 min of degradation, the supernatant was filtered through a 0.45 μm filter membrane, and immediately measured by ultraviolet spectrophotometer (UV-6100) at an absorbance wavelength of 310 nm. The concentration of residual tetrabromobisphenol A was 1.88 mg / L, 0.52 mg / L, and 0.94 mg / L, respectively, and the removal rate of cobalt-loaded walnut shell biochar for tetrabromobisphenol A was calculated to be 96.24%, 98.96%, and 98.12%, respectively.

[0034] Example 2 The walnut shell was washed with ultrapure water for 2-3 times to remove soluble impurities, and then placed in a 70°C drying oven for drying for 6 h, and after drying, passed through a 60 mesh sieve, and the particle size was -60 mesh, accounting for 100%; The sieved walnut shell 10 g was placed in a tube furnace for pyrolysis, the pyrolysis rate was 5°C / min, the pyrolysis time was 4 h, and the pyrolysis temperature was 400°C, and high-purity nitrogen was passed through the whole process to keep the furnace oxygen-free, and after cooling to room temperature, walnut shell biochar was obtained; 3 g of walnut shell biochar and 1 g of KOH solid were mixed, ground and passed through a 60 mesh sieve, and then placed in a tube furnace for activation pyrolysis, the pyrolysis rate was 5°C / min, the pyrolysis time was 4 h, and the pyrolysis temperature was 700°C, and high-purity nitrogen was passed through the whole process to keep the furnace oxygen-free, and after cooling to room temperature, washing and drying, activated biochar was obtained; 1 g of activated biochar and 0.1 g of cobalt acetylacetonate were added to 100 mL of tetrahydrofuran. After soaking and stirring for 16 h, the precipitate was filtered and washed 3-5 times with ultrapure water and once with ethanol. The precipitate was then dried in a 70˚C drying oven for 6 h, ground, and passed through a 60-mesh sieve. The obtained material was then pyrolyzed in a tube furnace at a rate of 5 °C / min, a temperature of 700 °C, and a time of 4 h. High-purity nitrogen was purged throughout the process to maintain an oxygen-free environment in the furnace. After pyrolysis, the material was cooled to room temperature to obtain cobalt-loaded walnut shell biochar with a cobalt loading mass percentage of 5%.

[0035] The performance of the obtained cobalt-supported walnut shell biochar was tested: 0.01 g of cobalt-supported walnut shell biochar was added to 100 mL of tetrabromobisphenol A solutions with a concentration of 50 mg / L and pH values ​​of 8, 9, and 10 for adsorption and degradation experiments. After adsorption for 5 min, 0.2 g / L PMS was added for degradation reaction. After degradation for 30 min, the supernatant was filtered through a 0.45 μm filter membrane, and the absorbance at a wavelength of 310 nm was immediately measured using a UV spectrophotometer (UV-6100). The concentrations of the remaining tetrabromobisphenol A were 1.98 mg / L, 0.29 mg / L, and 0.85 mg / L, respectively. The calculated removal rates of tetrabromobisphenol A by the cobalt-supported walnut shell biochar were 96.04%, 99.42%, and 98.30%, respectively.

[0036] Example 3 Wash the walnut shells 2-3 times with ultrapure water to remove dissolved impurities, then dry them in a 70℃ drying oven for 6 hours. After drying, pass them through a 60-mesh sieve, with 100% of the particles being of -60 mesh size. 5g of sieved walnut shells were placed in a tube furnace for pyrolysis at a rate of 5˚C / min for 4h and a temperature of 400˚C. High-purity nitrogen was purged throughout the process to maintain an oxygen-free environment in the furnace. After pyrolysis, the furnace was cooled to room temperature to obtain walnut shell biochar. 2g of walnut shell biochar was mixed with 1g of KOH solid, ground and passed through a 60-mesh sieve, and then placed in a tube furnace for activation pyrolysis. The pyrolysis rate was 5˚C / min, the pyrolysis time was 4h, and the pyrolysis temperature was 700˚C. High-purity nitrogen was purged throughout the process to maintain an oxygen-free state in the furnace. After pyrolysis, the biochar was cooled to room temperature, washed and dried to obtain activated biochar. 0.5 g of activated biochar and 0.2 g of cobalt acetylacetonate were added to 90 mL of tetrahydrofuran. After soaking and stirring for 16 h, the precipitate was filtered and washed 3-5 times with ultrapure water and once with ethanol. The precipitate was then dried in a 70˚C drying oven for 6 h, ground, and passed through a 60-mesh sieve. The obtained material was then pyrolyzed in a tube furnace at a rate of 5 °C / min, a temperature of 800 °C, and a time of 4 h. High-purity nitrogen was purged throughout the process to maintain an oxygen-free environment in the furnace. After pyrolysis, the material was cooled to room temperature to obtain cobalt-loaded walnut shell biochar with a cobalt loading mass percentage of 15%.

[0037] The performance of the obtained cobalt-supported walnut shell biochar was tested: 0.01 g of cobalt-supported walnut shell biochar was added to 100 mL of tetrabromobisphenol A solutions with a concentration of 50 mg / L and pH values ​​of 8, 9, and 10 for adsorption and degradation experiments. After adsorption for 5 min, 0.2 g / L PMS was added for degradation reaction. After degradation for 30 min, the supernatant was filtered through a 0.45 μm filter membrane, and the absorbance at a wavelength of 310 nm was immediately measured using a UV spectrophotometer (UV-6100). The concentrations of the remaining tetrabromobisphenol A were 2.14 mg / L, 0.86 mg / L, and 1.15 mg / L, respectively. The calculated removal rates of tetrabromobisphenol A by the cobalt-supported walnut shell biochar were 95.72%, 98.28%, and 97.70%, respectively.

[0038] Through the performance tests in Examples 1, 2, and 3, namely the adsorption and degradation tests of tetrabromobisphenol A (TBBPA) in a solution using cobalt-supported walnut shell biochar, it can be seen that the biochar achieved a one-time removal rate of over 95% for TBBPA within 35 minutes, demonstrating excellent removal performance. Furthermore, under constant conditions, within a certain pH range, the removal performance showed a trend of first increasing and then slightly decreasing with the increase of pH value. Similarly, under constant conditions, within a certain pyrolysis temperature range, the removal performance of the biochar decreased slightly with the increase of pyrolysis temperature.

[0039] Characterization: Figure 1 The image shows the XRD characterization of cobalt-loaded walnut shell biochar obtained in Example 1. It can be seen that the main component of the biochar is zero-valent cobalt, followed by graphitic carbon.

[0040] Figure 2 The Raman characterization diagram of cobalt-loaded walnut shell biochar obtained in Example 1 shows that the defect ratio (I) of the cobalt-loaded walnut shell biochar is... D / I G The defect ratio was 1.104, and the high defect ratio further improved the catalytic activity of the biochar.

[0041] Figure 3 The image shows the EPR characterization of cobalt-supported walnut shell biochar obtained in Example 1. It can be seen that the EPR vacancy test signal value of the cobalt-supported walnut shell biochar is 2.0034. The strong oxygen vacancy signal indicates that the biochar has a large number of oxygen vacancy active sites, which further improves the catalytic activity of the biochar.

[0042] The characterization figures above demonstrate the crystal structure, defect structure, and catalytic activity of the obtained biochar, providing evidence for the superior performance of cobalt-supported walnut shell biochar. Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing cobalt-supported walnut shell biochar, characterized in that, Includes the following steps: Walnut shells are pyrolyzed to obtain walnut shell biochar; The walnut shell biochar and activator are mixed and then pyrolyzed to obtain activated biochar. The activated biochar was impregnated in a cobalt-source organic solution and then subjected to pyrolysis to obtain the cobalt-loaded walnut shell biochar.

2. The preparation method according to claim 1, characterized in that, The pyrolysis temperature is 300~500℃, the holding time is 3~5h, and the heating rate is 5~10℃ / min.

3. The preparation method according to claim 1, characterized in that, The activator includes at least one of potassium hydroxide and sodium hydroxide; The mass ratio of walnut shell biochar to activator is 1~3:

1.

4. The preparation method according to claim 1, characterized in that, The pyrolysis activation temperature is 600~800℃, the holding time is 3~5h, and the heating rate is 5~10℃ / min.

5. The preparation method according to claim 1, characterized in that, The cobalt source organic solution includes a cobalt source and an organic solvent; the cobalt source includes at least one of cobalt acetylacetonate, cobalt chloride, and cobalt nitrate; the organic solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, and 1,4-dioxane. The mass ratio of the activated biochar to the cobalt source is 5~15:1~3; The ratio of activated biochar to organic solvent is 1g:90~110mL.

6. The preparation method according to claim 1, characterized in that, The impregnation is carried out under stirring conditions, and the impregnation time is 14-18 hours.

7. The preparation method according to claim 1, characterized in that, The pyrolysis treatment is performed at a temperature of 600~800℃, with a holding time of 3~5h and a heating rate of 5~10℃ / min. The pyrolysis process is carried out in a protective atmosphere.

8. The cobalt-loaded walnut shell biochar prepared by the preparation method according to any one of claims 1 to 7, characterized in that, It includes walnut shell biochar and cobalt loaded on the walnut shell biochar.

9. The cobalt-supported walnut shell biochar according to claim 8, characterized in that, The cobalt loading percentage is 5-15%.

10. The application of the cobalt-supported walnut shell biochar according to claim 8 or 9 in the treatment of tetrabromobisphenol A wastewater.

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