Active biochar as well as preparation method and application thereof
By mixing the sludge with potassium ferrate, urea and potassium chloride and pyrolyzed, activated biochar with high-efficiency phosphate adsorption capacity is prepared, which solves the problem of limited adsorption capacity of biochar directly produced by municipal sludge, and achieves efficient and low-cost wastewater treatment.
Patent Information
- Application Number
- CN202411719827.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-27
- Publication Date
- 2025-03-04
AI Technical Summary
In the prior art, the adsorption capacity of bioactivated carbon directly produced by municipal sludge is limited, and the modification process is complex, which poses problems of high energy consumption and environmental pollution risks.
Active biochar with significant phosphate adsorption preference was prepared by mixing the dry sludge with potassium ferrate, urea and potassium chloride and pyrolyzed in an oxygen-free atmosphere.
High-efficiency phosphate adsorption of bioactivated carbon is achieved, the effluent phosphate concentration can be reduced to 0.1 mg/L, and the adsorption performance remains efficient within the pH range of 2-9, reducing production costs and environmental pollution risks.
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Figure CN119549111A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of sludge treatment, and specifically to an activated biochar and a preparation method and application thereof. Background Art
[0002] Municipal sludge is an inevitable byproduct of municipal sewage treatment plants during sewage treatment. It is composed of sediments and a large number of microorganisms in sewage. The biological activated carbon prepared from municipal sludge has good adsorption performance, and the preparation process is simple and low-cost. The obtained product has adsorption selectivity and stability for target pollutants. Therefore, the biological activated carbon prepared by pyrolysis of sludge is a potential resource recovery path.
[0003] The adsorption capacity of biological activated carbon directly produced from municipal sludge is limited, and it must be optimized and modified by external substances and energy to improve its own adsorption performance. At present, the modification method of biochar is usually to modify it with a single chemical agent, or to use salt solution in combination with acid solution, salt solution in combination with alkaline solution, solid oxide in combination with liquid oxidant, etc. In the process of biological activated carbon modification, methods that meet the advantages of low energy consumption, high efficiency, and easy operation have been widely studied and explored.
[0004] Among the many modification methods, different modification methods have different mechanisms of action. For example, studies have shown that by introducing high-density quaternary ammonium groups to anchor metal oxides in bioactivated carbon, the resulting composite bioactivated carbon has a high adsorption rate, adsorption capacity and adsorption preference for phosphate. Its main adsorption mechanism is the specific inner sphere complexation between phosphate and anchored iron oxide. This is mainly attributed to the introduction of quaternary ammonium groups that trigger the dispersion of iron oxide particles and the Donnan film effect. In addition, the introduction of non-metallic elements to functionalize biochar can attach some specific functional groups to its surface to improve the selectivity for phosphate. For example, the introduction of nitrogen can improve the surface alkalinity of biochar, thereby significantly improving the adsorption effect of phosphate.
[0005] Although the adsorption performance of the obtained adsorption material is improved, the phosphorus concentration in the effluent is still difficult to maintain below the concentration level of 0.1 mg / L, and the preparation process is still very complicated, with a very high risk of environmental pollution. In addition, after phosphorus is recovered through biochar, chemical reagents are required to separate phosphorus from biochar, thereby achieving biochar regeneration. However, this method has problems such as high production cost, low phosphorus recovery efficiency and environmental pollution. Summary of the invention
[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides an activated biochar and a preparation method and application thereof.
[0007] To achieve the above objectives, the scheme of this application is as follows:
[0008] In the first aspect, the present invention provides a method for preparing activated biochar, which uses sludge as raw material and sequentially comprises the steps of air drying, crushing, screening, drying, pyrolysis, post-treatment, cleaning and drying. After drying and before pyrolysis, the method further comprises the following steps: mixing the dried sludge with potassium ferrate, urea and potassium chloride.
[0009] Optionally, the sludge is municipal sludge.
[0010] Optionally, the drying temperature is 78-82°C.
[0011] Optionally, the pyrolysis comprises: heating to 750-850° C. at a heating rate of 8-12° C. / min in an oxygen-free atmosphere, and maintaining the temperature at 750-850° C. for 0.5-1.5 h.
[0012] Optionally, the flow rate of the oxygen-free atmosphere is 150-250 mL / min.
[0013] Optionally, the post-treatment includes: placing in a ferric chloride solution for treatment.
[0014] Optionally, the concentration of the ferric chloride solution is 0.05-0.15 mol / L.
[0015] Optionally, the drying temperature is 68-72°C.
[0016] Optionally, dry to constant weight.
[0017] Optionally, the mass ratio of the dried sludge, potassium ferrate, urea and potassium chloride is 3-4:0.5-1:0.5-1:3-4.
[0018] In a second aspect, the present application also provides activated biochar prepared according to the method described above.
[0019] In a third aspect, the present application also provides the use of the activated biochar as described above in the treatment of phosphate-containing wastewater.
[0020] Beneficial effects of the present invention:
[0021] The invention prepares biological activated carbon by using sludge as raw material, realizes waste resource utilization and reduces production cost.
[0022] The biological activated carbon of the present invention has a significant preference for phosphate adsorption and a wide adsorption pH, and still maintains a relatively high removal efficiency (≥81.62%) under the condition of the presence of high concentration adsorption competing ions, and the phosphate removal efficiency is higher than 80% in the pH range of 2-9.
[0023] The biological activated carbon of the present invention has excellent adsorption performance in the continuous adsorption column operation, which can process about 590 bed volumes (BV) and achieve breakthrough (effluent phosphate concentration is 0.1 mg / L), and the bed volume lost after two regenerations is low.
[0024] The biological activated carbon of the present application has no biological toxicity before and after adsorption, and has an extremely low risk of environmental pollution after adsorption, and can be directly used as a phosphate fertilizer for plant cultivation. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.
[0026] Figure 1 It is a scanning electron microscope (SEM);
[0027] Figure 2 The adsorption effect diagram of the biological activated carbon prepared in Example 1 at different times;
[0028] Figure 3 The adsorption effect of different biological activated carbons at different times
[0029] Figure 4 This is a diagram showing the adsorption effect of the biological activated carbon prepared in Example 1 at different pH values;
[0030] Figure 5 This is a diagram showing the adsorption effect of the biological activated carbon prepared in Example 1 and the interfering ions of different concentrations;
[0031] Figure 6 The figure is a diagram showing the adsorption effect of the biological activated carbon prepared in Example 1 on five groups of actual water samples;
[0032] Figure 7 The figure is a graph showing the change of the removal rate of phosphate by the biological activated carbon prepared in Example 1 with the number of cycles;
[0033] Figure 8 This is a diagram showing the operation effect of the continuous adsorption column of biological activated carbon prepared in Example 1;
[0034] Fig. 9 This is a graph showing the effects of adsorption on mung bean growth before and after adsorption. DETAILED DESCRIPTION
[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0036] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present invention; however, it is apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details.
[0037] Example 1
[0038] The preparation method of activated biochar includes the following specific steps:
[0039] S1. Air drying: Spread the sludge from the municipal sewage treatment plant evenly on a plastic board, keeping a uniform thickness of about 5 mm, avoid sunlight, and dry naturally;
[0040] S2. Crushing: The air-dried sludge is put into a grinder for crushing to obtain sludge powder;
[0041] S3. Sieving: The sludge powder is sieved through a 100-mesh sieve to obtain a uniform sludge material;
[0042] S4. Drying: The uniform sludge obtained in step S3 is placed in a drying oven and dried at 80±2°C for 24h to obtain dried sludge;
[0043] S5. Mixing: mixing the dried sludge with potassium ferrate, urea and potassium chloride in a mass ratio of 3:1:1:3 to obtain a mixture;
[0044] S6. Pyrolysis: The mixture was placed in a tubular furnace, filled with nitrogen (200 mL / min), heated to 800°C at a heating rate of 10°C / min, and kept at 800°C for 1 h, and then cooled to room temperature.
[0045] S7. Post-treatment: treating the pyrolysis product with a 0.1 mol / L ferric chloride hexahydrate solution to remove residual phosphorus;
[0046] S8. Washing and drying: washing the post-treatment product with deionized water until the pH is neutral, and drying it at 70±2°C to constant weight to obtain activated biochar.
[0047] Comparative Example 1
[0048] The difference between this comparative example and Example 1 is:
[0049] S5. Mixing: Mix the dried sludge with potassium ferrate and potassium chloride in a mass ratio of 3:1:3 to obtain a mixture.
[0050] That is, urea was not added in the mixed material of this comparative example.
[0051] Comparative Example 2
[0052] The difference between this comparative example and Example 1 is:
[0053] S5. Mixing: Mix the dried sludge with urea and potassium chloride in a mass ratio of 3:1:3 to obtain a mixture.
[0054] That is, potassium ferrate was not added to the mixed material of this comparative example.
[0055] Performance Testing
[0056] The activated biochar prepared in Example 1, Comparative Example 1 and Comparative Example 2 was scanned by electron microscope. The results are as follows: Figure 1 shown.
[0057] The activated biochar prepared in Example 1 was subjected to nitrogen adsorption-desorption testing, and the results are shown in Table 1.
[0058] Table 1 Nitrogen adsorption-desorption test results
[0059] Group <![CDATA[Specific surface area (m 2 / g)]]> Average pore size (nm) <![CDATA[Pore volume (cm 3 / g)]]> Example 1 (Fe / N-KBC) 285.72 6.57 0.364 Comparative Example 1 (Fe / KBC) 28.64 7.46 0.038 Comparative Example 2 (N-KBC) 188.62 6.24 0.290
[0060] It can be seen from Table 1 that the biological activated carbon prepared in Example 1 has a developed pore structure and a high specific surface area.
[0061] The adsorption of phosphate in wastewater by the biological activated carbon prepared in Example 1, Comparative Example 1 and Comparative Example 2 was tested. The concentration of phosphate in the wastewater was 1.2 mg / L and the pH was 6.0. The amount of biological activated carbon was 1 g / L. The results are as follows: Figure 2 and Figure 3 shown.
[0062] like Figure 2 and Figure 3 As shown, the biological activated carbon prepared in Example 1 can achieve a phosphate removal rate of 98.64% within 2 hours, while the phosphate removal rates of the biological activated carbons prepared in Comparative Examples 1 and 2 within 2 hours are 22.57% and 65.10%, respectively.
[0063] The adsorption of phosphate in wastewater with different pH values by the biological activated carbon prepared in Example 1 was tested. The concentration of phosphate in the wastewater was 1.2 mg / L and the pH values were 2-9. The amount of biological activated carbon used was 1 g / L. The results are as follows: Figure 4 shown.
[0064] like Figure 4As shown, the removal rate of phosphate by the biological activated carbon prepared in Example 1 is higher than 80% in the pH range of 2-9.
[0065] The adsorption of phosphate in wastewater in the presence of different interfering ions by the biological activated carbon prepared in Example 1 was tested. The concentration of phosphate in the wastewater was 1.2 mg / L and the pH was 6.0. The dosage of the biological activated carbon was 1 g / L. The results are as follows: Figure 5 shown.
[0066] like Figure 5 As shown in the figure, when the concentration is tripled and all competing ions are mixed, the phosphate removal efficiency can still be as high as 81.62%.
[0067] The adsorption of phosphate in wastewater by the biological activated carbon prepared in Example 1 was tested. Specifically, water samples from the secondary sedimentation tank of the sewage treatment plant were taken at fixed time points for five consecutive days. The amount of biological activated carbon was 1 g / L and the adsorption time was 2 h. The results are as follows: Figure 6 shown.
[0068] like Figure 6 As shown, the phosphate removal rate in each group (i.e. corresponding days) was higher than 88%.
[0069] Will Figure 2 The treated wastewater was subjected to biological activated carbon adsorption test again. Specifically, it was separated by filtration and regenerated with 0.1 mol / L NaOH solution. Figure 2 The test parameters shown above correspond to the adsorption of phosphate, and the results are as follows Figure 7 shown.
[0070] like Figure 7 As shown, the phosphate removal efficiency in the fifth cycle was still maintained at 88.37%, and the iron leaching amount was extremely low, only 0.005 mg / L.
[0071] The biological activated carbon prepared in Example 1 was used to adsorb and remove phosphate. Specifically, 1 mL of biological activated carbon was added to the adsorption column, and the adsorption column was continuously operated and its effluent concentration was tested. The results are as follows: Figure 8 shown.
[0072] like Figure 8 As shown, the biochar activated carbon could treat 590 bed volumes (BV) before reaching breakthrough (effluent phosphate concentration of 0.1 mg / L), and the loss of bed volume after regeneration was very low.
[0073] Pick Figure 2The treated wastewater was filtered to separate the adsorbed biological activated carbon, and dried at 70±2°C to constant weight. The bioactivated carbon prepared in Example 1 was used for hydroponic mung bean experiment, and a blank group and a Hogland nutrient solution control group were set (specifically, a total of 4 groups, 1 of which was a blank group (500ml deionized water), without adding any nutrients; 0.5g Fe / N-KBC adsorbent and 0.5g Fe / N-KBC-P adsorbent were added to 500ml deionized water respectively in groups 2 and 3; group 4 was a Hogland nutrient solution group, specifically, 0.945g of reagent A and 1.24g of reagent B were added to 1L deionized water, and then 500ml was measured for the experiment). The results are as follows Fig. 9 shown.
[0074] The results are as follows Fig. 9 As shown, the biochar before and after adsorption has no biological toxicity, and the adsorbed biochar can be directly used as a phosphate fertilizer for plant cultivation.
[0075] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for preparing activated biochar, characterized in that: The method uses sludge as raw material, and includes air drying, crushing, screening, drying, pyrolysis, post-treatment, cleaning and drying steps in sequence. After drying and before pyrolysis, the method also includes the following steps: mixing the dried sludge with potassium ferrate, urea and potassium chloride.
2. The method for preparing activated biochar according to claim 1, characterized in that: The sludge is municipal sludge.
3. The method for preparing activated biochar according to claim 1, characterized in that: The drying temperature is 78-82°C.
4. The method for preparing activated biochar according to claim 1, characterized in that: The pyrolysis comprises: heating to 750-850° C. at a heating rate of 8-12° C. / min in an oxygen-free atmosphere, and maintaining the temperature at 750-850° C. for 0.5-1.5 h.
5. The method for preparing activated biochar according to claim 1, characterized in that: The post-treatment comprises: placing in a ferric chloride solution for treatment.
6. The method for preparing activated biochar according to claim 5, characterized in that: The concentration of the ferric chloride solution is 0.05-0.15 mol / L.
7. The method for preparing activated biochar according to claim 1, characterized in that: The drying temperature is 68-72°C.
8. The method for preparing activated biochar according to claim 1, characterized in that: The mass ratio of the dried sludge, potassium ferrate, urea and potassium chloride is 3-4:0.5-1:0.5-1:3-4.
9. Activated biochar prepared according to the method according to any one of claims 1 to 8.
10. Use of the activated biochar according to claim 9 in the treatment of phosphate-containing wastewater.