Modified straw biochar capable of adsorbing manganese as well as preparation method and application of modified straw biochar

Abstract

The invention relates to modified straw biochar capable of adsorbing manganese as well as a preparation method and application thereof, and relates to the technical field of water pollution treatment and biomass carbonization. Comprising the following steps: (1) pretreatment of rape straws: drying and crushing the rape straws to obtain rape straw powder; (2) preparation of modified straw biochar capable of adsorbing manganese: activating the rape straw powder and a K2CO3 solution to obtain activated rape straw powder; the activated rape straw powder is carbonized under the oxygen limiting condition, and the modified straw biochar capable of adsorbing manganese is obtained. According to the method, common agricultural waste rape straw is used as a raw material and is activated by the potassium carbonate solution to prepare the modified straw biochar capable of adsorbing manganese, so that the waste straw can be reasonably and resourcefully utilized, the environmental pressure is relieved, the problem of manganese pollution of a water body is solved, and the purpose of treating waste with waste is achieved.

Description

Technical Field

[0001] The invention relates to the fields of water pollution control technology and biomass carbonization technology, and in particular to a modified straw biochar capable of adsorbing manganese, a preparation method and application thereof. Background Art

[0002] In recent years, the mining of manganese ore resources has produced a large amount of tailings, waste slag and waste mud. Their unreasonable discharge has caused serious pollution to the local water and soil environment. If the human body consumes drinking water containing manganese at higher levels than normal for a long time, it will cause a series of health problems, such as impaired neurological function and mental disorders. Therefore, the treatment of manganese-containing wastewater has important practical significance.

[0003] Biochar is an adsorbent with extremely high carbon content. It has the characteristics of developed pore structure, large specific surface area, and rich functional groups on the surface. The raw materials for preparing biochar come from a wide range of sources. Among them, preparing biochar from agricultural waste is the most common. my country is a major agricultural country, with an annual rapeseed production of about 14 million tons. Directly discarding or burning rapeseed straw after harvest not only has adverse environmental benefits to the local area, but also causes waste of resources. Therefore, preparing rapeseed straw into biochar can not only alleviate land and environmental pressures, but also treat heavy metal wastewater to a certain extent.

[0004] The adsorption performance of biochar is limited by different biomass raw materials. The original biochar has a weak adsorption capacity for heavy metals and a low removal efficiency. The key to solving this problem is to modify the biomass raw materials to prepare modified biochar with better adsorption performance. Commonly used modification agents can be divided into acids, bases, salts and organic agents. The above-mentioned modifiers such as strong acids and strong bases may cause harm to human health, and there are also problems such as high cost. In view of this, the present invention provides a modified straw biochar capable of adsorbing manganese, a preparation method and application thereof. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art of complex preparation methods and low removal efficiency of manganese-contaminated wastewater, the technical problem to be solved by the present invention is to provide a modified straw biochar that can adsorb manganese by potassium carbonate for removing manganese from sewage, which has a simple preparation method, is economically feasible and has high adsorption efficiency, and a preparation method and application thereof.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, a method for preparing modified straw biochar capable of adsorbing manganese comprises the following steps:

[0008] (1) Rape straw pretreatment: drying and crushing the rape straw to obtain rape straw powder;

[0009] (2) Preparation of modified straw biochar capable of adsorbing manganese: The rape straw powder was mixed with K 2 CO 3 The solution is activated to obtain activated rape straw powder; the activated rape straw powder is carbonized under oxygen-limited conditions to obtain modified straw biochar capable of adsorbing manganese.

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, the drying in step (1) is specifically as follows: drying the rape straw at 30° C. to 100° C. to a constant weight;

[0012] The crushing in step (1) specifically includes crushing the rape straw and then sieving it until it meets the standards.

[0013] Furthermore, the particle size of the rape straw powder is less than 60 meshes.

[0014] Further, step (2) includes the following specific steps:

[0015] (2-1) The rape straw powder and K 2 CO 3 The solutions are mixed, shaken and reacted at room temperature (e.g., about 30° C.), then left to stand, washed to neutrality, and then dried to constant weight to obtain activated rape straw powder;

[0016] (2-2) The activated rape straw powder is sealed in a ceramic crucible for carbonization to obtain modified straw biochar capable of adsorbing manganese.

[0017] Furthermore, in step (2-1), K 2 CO 3 K in solution 2 CO 3 The concentration of the rape straw powder is 2 mol / L; 2 CO 3 The solid-liquid ratio of the solution is 0.5-2g:10-20ml.

[0018] Further, the parameters of the oscillation reaction in step (2-1) are: oscillation speed is 50-200 rpm, time is 0.5h-2h;

[0019] The parameters for standing in step (2-1) are: standing at room temperature for 5h-60h;

[0020] The drying parameters in step (2-1) are: temperature of 30°C-100°C, and drying to constant weight.

[0021] Furthermore, the carbonization parameters in step (2-2) are: carbonization temperature is 400°C-700°C, and carbonization time is 1h-4h.

[0022] In a second aspect, a modified straw biochar capable of adsorbing manganese is provided, wherein the modified straw biochar capable of adsorbing manganese is prepared by the preparation method.

[0023] Furthermore, the specific surface area of ​​the modified straw biochar capable of adsorbing manganese is 2.22 m 2 / g, the average pore diameter is 42.81nm; the total pore volume is 0.024mL / g.

[0024] In a third aspect, a modified straw biochar capable of adsorbing manganese is used to remove manganese in water.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention uses rapeseed straw, a common agricultural waste, as raw material and prepares modified straw biochar capable of adsorbing manganese after activation with potassium carbonate solution. This not only can rationalize and resource the utilization of waste straw and alleviate environmental pressure, but also solves the problem of manganese pollution in water bodies, thus achieving the purpose of "treating waste with waste".

[0027] (2) The pore volume of the modified straw biochar capable of adsorbing manganese prepared by the present invention is 1.26 times that of the unmodified original biochar, and the average pore diameter is 1.94 times that of the unmodified original biochar. The expansion of the pore volume and pore diameter is beneficial to the removal of heavy metals.

[0028] (3) The modified straw biochar prepared by the present invention that can adsorb manganese with potassium carbonate has a good removal effect on Mn and is superior to other adsorbents for removing manganese under the same reaction conditions.

[0029] (4) The preparation method of the modified straw biochar capable of adsorbing manganese by potassium carbonate prepared by the present invention is simple and environmentally friendly, and can be applied to actual industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope image of the original biochar from rapeseed straw;

[0031] Figure 2 This is a scanning electron microscope image of the modified straw biochar that can adsorb manganese using potassium carbonate;

[0032] Figure 3 X-ray diffraction patterns of biochar before and after modification;

[0033] Figure 4 This is a graph showing the effect of different initial concentrations of manganese solutions on the adsorption of manganese by modified straw biochar that can be adsorbed by potassium carbonate in the present invention;

[0034] Figure 5 This is a comparison chart of specific surface area analysis of the present invention. DETAILED DESCRIPTION

[0035] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0036] The detection method adopted in the following examples is as follows:

[0037] 1. Characterization of biochar:

[0038] (1) The morphology of the biochar surface was observed using a FEI Inspect F50 scanning electron microscope at a magnification of 500 to 40,000 times and an electron beam acceleration voltage of 20 kV.

[0039] (2) Using 3H-2000PS4 surface area analyzer, the 2 The specific surface area, average pore size and total pore volume of biochar were measured under degassing conditions of 120 °C for 12 h.

[0040] 2. Adsorption and removal rate of manganese:

[0041] In order to investigate the actual application effect of the prepared modified biochar, the following adsorption experiments were carried out: 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L and 300 mg / L manganese solutions were prepared respectively, 0.05 g potassium carbonate modified biochar was added to the above solutions, shaken at room temperature for 4 hours, taken out after the reaction was completed, filtered with a 0.45 μm filter membrane and diluted.

[0042] The residual concentration of manganese after adsorption was determined by atomic absorption spectrophotometry (national standard GB / T 7475-1987). The effect of different initial concentrations of manganese solution on the adsorption amount and removal rate of manganese adsorbed by potassium carbonate modified straw biochar was calculated by the formula:

[0043]

[0044] Where: Q and P are the adsorption capacity (mg / g) and removal rate (%) of heavy metals by biochar, respectively; C 0 and C t are the initial heavy metal solution concentration and the remaining heavy metal solution concentration after the reaction, mg / L; V is the volume of the heavy metal solution, mL; m is the mass of biochar, g.

[0045] Example

[0046] 1. Preparation of modified straw biochar with potassium carbonate capable of adsorbing manganese

[0047] The present embodiment relates to a method for preparing modified straw biochar capable of adsorbing manganese, comprising the following steps:

[0048] (1) Rape straw pretreatment: drying and crushing the rape straw to obtain rape straw powder;

[0049] Preferably, the drying in step (1) is specifically: drying the rape straw at 30°C-100°C to constant weight; the pulverizing in step (1) is specifically: pulverizing the rape straw and then sieving until it meets the standard. The particle size of the rape straw powder is less than 60 mesh.

[0050] (2) Preparation of modified straw biochar capable of adsorbing manganese:

[0051] The rape straw powder was mixed with a certain concentration of K 2 CO 3 The solution is activated to obtain activated rape straw powder; the activated rape straw powder is carbonized under sealed conditions to obtain modified straw biochar capable of adsorbing manganese.

[0052] Preferably, step (2) includes the following specific steps:

[0053] (2-1) The rape straw powder and K 2 CO 3 The solutions are mixed, shaken and reacted at room temperature (e.g., about 30° C.), then left to stand, washed to neutrality, and then dried to constant weight to obtain activated rape straw powder;

[0054] Among them, K in step (2-1) 2 CO 3 K in solution 2 CO 3 The concentration of the rape straw powder is 2 mol / L; 2 CO 3 The solid-liquid ratio of the solution is 0.5-2g:10-20ml. The parameters of the oscillation reaction in step (2-1) are: oscillation speed is 50-200rpm, time is 0.5h-2h; the parameters of the standing in step (2-1) are: standing at room temperature for 5h-60h; the parameters of the drying in step (2-1) are: temperature is 30℃-100℃, and drying is performed to constant weight.

[0055] (2-2) The activated rape straw powder is sealed in a ceramic crucible for carbonization to obtain modified straw biochar capable of absorbing manganese. Specifically, a certain amount of activated rape straw powder is placed in a ceramic crucible, sealed and wrapped with tin foil, and placed in a muffle furnace, and the carbonization temperature and carbonization time are set. After the reaction is completed, it is cooled to room temperature, ground and passed through a 100-mesh standard sample sieve to obtain modified straw biochar capable of absorbing manganese by potassium carbonate.

[0056] Wherein, the carbonization parameters in step (2-2) are: carbonization temperature is 400°C-700°C, and carbonization time is 1h-4h.

[0057] 2. Condition Optimization

[0058] When the carbonization temperature was changed and the solid-liquid ratio (1 g: 15 ml) and carbonization time (2.5 h) were kept constant, the modified straw biochar that could adsorb manganese by potassium carbonate was obtained. The adsorption amount and removal rate were tested. The results are shown in Table 1:

[0059] Table 1

[0060]

[0061] When the carbonization time was changed and the carbonization temperature (500°C) and the solid-liquid ratio (1:10) were kept unchanged, the modified straw biochar that could adsorb manganese by potassium carbonate was obtained. The adsorption amount and removal rate were tested. The results are shown in Table 2:

[0062] Table 2

[0063]

[0064] When the solid-liquid ratio (g: ml) was changed and the carbonization temperature (500°C) and carbonization time (2.5 h) were kept unchanged, the modified straw biochar that can adsorb manganese by potassium carbonate was obtained. The adsorption amount and removal rate were tested. The results are shown in Table 3:

[0065] It can be seen that the rape straw powder and the K 2 CO 3 The solid-liquid ratio of the solution is 1:15 (g:ml), and the carbonization parameters are: carbonization temperature 600℃, carbonization time 2.5h. The modified straw biochar with potassium carbonate adsorbing manganese has the best performance.

[0066] Table 3

[0067]

[0068] 3. Rapeseed straw raw biochar

[0069] Compared with Example 1, pure water was used to replace K 2 CO 3Except for the solution, the rest were the same as in Example 1, and rape straw raw biochar was obtained.

[0070] Table 4 Statistics of specific surface area, average pore size and total pore volume of biochar

[0071]

[0072] As shown in Table 1, the specific surface area of ​​the modified straw biochar capable of adsorbing manganese obtained under the optimal conditions is 2.22 m 2 / g, the average pore diameter is 42.81nm; the total pore volume is 0.024mL / g.

[0073] 4. Comparison with other existing literature records

[0074] The modified straw biochar capable of adsorbing manganese obtained under the optimal conditions was compared with that recorded in other existing literature, and the results are shown in Table 5.

[0075] References [1] to [4] are as follows:

[0076] [1] Bao Fuxing, Yue Zhengbo, Gao Yijun, et al. Study on the adsorption of Mn2+ by composite modified sludge biochar. Journal of Hefei University of Technology (Natural Science Edition). 2023, 46(10): 1322-30.

[0077] [2]CHOWDHURY Z,ABD HAMID SB,ZAIN S,et al.Catalytic Pretreatment ofBiochar residues derived from Lignocellulosic Feedstock for EquilibriumStudies of Manganese,Mn(II)cations from aqueous solution[J].RSC Adv,2014,5.

[0078] [3]DE CASTRO AE, PENIDO ES, SOUZA TF, et al. Biochars from modified sugarcane bagasse for manganese removal from mining effluents[J]. Journal of Environmental Chemical Engineering, 2023, 11(5).

[0079] [4]AN Q,MIAO Y,ZHAO B,et al.An alkali modified biochar for enhancing Mn2+adsorption:Performance and chemical mechanism[J].Materials Chemistry andPhysics,2020,248.

[0080] Table 5 Comparison of the present invention and conventional manganese removal

[0081]

[0082] in, Figure 1 and Figure 2 The following are scanning electron micrographs of rape straw biochar and modified straw biochar that can adsorb manganese with potassium carbonate. Compared with the original rape straw biochar, the modified biochar has more surface particles and pores, and the pore volume and pore size are larger ( Figure 5 ), these changes create favorable conditions for the adsorption of heavy metals. Figure 3 The X-ray diffraction patterns of the original rapeseed straw biochar and the modified straw biochar that can adsorb manganese by potassium carbonate show that the mineral composition of the biochar has changed after modification, and more mineral diffraction peaks that promote adsorption have appeared, which can enhance the exchange of heavy metal ions with the mineral components on the surface of biochar.

[0083] The results of manganese adsorption and removal rate are as follows Figure 4 As shown in the figure, it can be found that with the increase of the initial concentration of manganese solution, the adsorption amount of modified biochar also increases. When the initial solution concentration is within 50mg / L-150mg / L, the removal rate is more than 95%. When the solution concentration increases to 300mg / L, the removal rate is still close to 80%. The modified biochar has a significant effect on removing manganese, indicating that it is a highly efficient adsorbent with good application potential.

[0084] In summary, the present invention uses rapeseed straw, a common agricultural waste, as raw material, and prepares modified straw biochar that can adsorb manganese after activation with potassium carbonate solution. This can not only rationalize and resource the utilization of waste straw to alleviate environmental pressure, but also solve the problem of manganese pollution in water bodies, thus achieving the purpose of "treating waste with waste".

[0085] The pore volume of the modified straw biochar capable of adsorbing manganese prepared by the present invention is 1.26 times that of the unmodified original biochar, and the average pore diameter is 1.94 times that of the unmodified original biochar. The enlargement of the pore volume and pore diameter is conducive to the removal of heavy metals. The modified straw biochar capable of adsorbing manganese prepared by the potassium carbonate of the present invention has a good removal effect on Mn, and is superior to other adsorbents for removing manganese under the same reaction conditions. The preparation method of the modified straw biochar capable of adsorbing manganese prepared by the potassium carbonate of the present invention is simple and environmentally friendly, and can be applied to actual industrial production.

[0086] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing modified straw biochar capable of adsorbing manganese, characterized in that: The steps include: (1) Rape straw pretreatment: drying and crushing the rape straw to obtain rape straw powder; (2) Preparation of modified straw biochar capable of adsorbing manganese: activating the rape straw powder with a K2CO3 solution to obtain activated rape straw powder; carbonizing the activated rape straw powder under oxygen-limited conditions to obtain modified straw biochar capable of adsorbing manganese.

2. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 1, characterized in that: The drying in step (1) specifically comprises: drying the rape straw at 30° C. to 100° C. to a constant weight; The crushing in step (1) specifically includes crushing the rape straw and then sieving it until it meets the standards.

3. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 1, characterized in that: The particle size of the rape straw powder is less than 60 meshes.

4. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 1, characterized in that: Step (2) includes the following specific steps: (2-1) mixing the rape straw powder with a K2CO3 solution, oscillating the mixture at room temperature, allowing the mixture to stand, washing the mixture to neutrality, and drying the mixture to constant weight to obtain activated rape straw powder; (2-2) The activated rape straw powder is sealed in a ceramic crucible for carbonization to obtain modified straw biochar capable of adsorbing manganese.

5. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 4, characterized in that: The concentration of K2CO3 in the K2CO3 solution in step (2-1) is 2 mol / L; the solid-liquid ratio of the rape straw powder to the K2CO3 solution is 0.5-2 g:10-20 ml.

6. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 4, characterized in that: The parameters of the oscillation reaction in step (2-1) are: oscillation speed is 50-200 rpm, and time is 0.5h-2h; The parameters for standing in step (2-1) are: standing at room temperature for 5h-60h; The drying parameters in step (2-1) are: temperature of 30°C-100°C, and drying to constant weight.

7. The method for preparing modified straw biochar capable of adsorbing manganese according to claim 1, characterized in that: The carbonization parameters in step (2-2) are: carbonization temperature is 400°C-700°C, and carbonization time is 1h-4h.

8. A modified straw biochar capable of adsorbing manganese, characterized in that: The modified straw biochar capable of adsorbing manganese is prepared by the preparation method according to any one of claims 1 to 7.

9. The modified straw biochar capable of adsorbing manganese according to claim 8, characterized in that: The specific surface area of ​​the modified straw biochar capable of adsorbing manganese is 2.22 m 2 / g, the average pore diameter is 42.81nm; the total pore volume is 0.024mL / g.

10. An application of modified straw biochar capable of adsorbing manganese, characterized in that: The modified straw biochar capable of adsorbing manganese as described in any one of claims 8 to 9 is used for removing manganese in water.

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