Modified straw pyrolytic carbon adsorbent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of agricultural waste recycling and water treatment, in particular to a modified straw pyrolytic carbon adsorbent and a preparation method and application thereof. The preparation method of the modified straw pyrolytic carbon adsorbent comprises the following steps: by taking a calcium source and a zinc source as modifiers, activating and dipping straw powder by using a modifier solution, evaporating to remove a solvent, performing pyrolytic carbonization, and then performing acid pickling, water washing and drying to obtain the modified straw pyrolytic carbon adsorbent. The calcium source and the zinc source are used as modifiers for activating, impregnating and pyrolyzing and carbonizing the straw powder, so that the prepared modified straw pyrolytic carbon adsorbent can have relatively large adsorption capacity, and the adsorption performance on bisphenol A in water is improved; the problem that the adsorption capacity of the rice straw pyrolytic carbon prepared through an existing method on bisphenol A in water is low is solved.

Description

Technical Field

[0001] This invention relates to the fields of agricultural waste resource utilization and water treatment technology, specifically to a modified straw pyrolysis char adsorbent, its preparation method, and its application. Background Technology

[0002] Recalcitrant organic pollutants in the environment, such as bisphenol A (BPA), often pose potential safety risks to the aquatic environment due to their slow degradation in water. The most common treatment method for BPA is physical adsorption, which has the advantages of simple operation, low cost, and a wide availability of adsorbents.

[0003] Most crop straw, such as soybean straw, wheat straw, and rice straw, is disposed of through burning or landfilling, which not only wastes resources but also exacerbates greenhouse gas emissions and air pollution. Therefore, using biomass carbonization technology to pyrolyze crop straw to prepare porous carbon materials can not only achieve the resource utilization of crop straw but also prevent the significant impact of crop straw burning on the urban and rural ecological environment. Currently, porous carbon materials prepared by pyrolyzing crop straw using biomass carbonization technology can be used as adsorbents to adsorb recalcitrant organic pollutants in the environment. However, these agricultural waste adsorbents have a low adsorption capacity for organic pollutants, limiting their widespread application in water treatment.

[0004] For example, Reference 1: Wang Jianfei, Chen Zaiming, Li Bing. Study on the adsorption and removal performance of rice straw ash for bisphenol A in water [J]. DOI: 10.3969 / j.issn.1001-5132.2020.02.011. Reference 1 records that rice straw ash produced by burning rice straw at 500℃ can be used for the adsorption and removal of bisphenol A in water. This is mainly because rice straw pyrolysis char has a well-developed pore structure, a high degree of carbonization, and stable chemical properties. However, the maximum adsorption capacity of rice straw pyrolysis char for bisphenol A in water per unit mass is only 10.3 mg / g, which is too low and difficult to meet the requirements for large-scale promotion and use. Summary of the Invention

[0005] To address the problem of low adsorption capacity of bisphenol A in water by rice straw pyrolysis char prepared by existing methods, this invention provides a modified straw pyrolysis char adsorbent, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] The first aspect of this invention provides a method for preparing a modified straw pyrolysis char adsorbent, comprising the following steps: Using calcium and zinc sources as modifiers, straw powder was activated and impregnated with the modifier solution. After evaporation to remove the solvent, it was pyrolyzed and carbonized, then acid-washed and water-washed, and dried to obtain modified straw pyrolysis carbon adsorbent. The ratio of straw powder to modifier was 1g:10mmol; the molar ratio of zinc source to calcium source was 1:0.4-1.5.

[0008] This invention primarily uses calcium and zinc sources as modifiers. The straw powder is activated and impregnated with a modifier solution, allowing calcium and zinc ions to penetrate into the fiber structure of the straw powder and catalyze the hydrolysis of cellulose and hemicellulose. The activated and impregnated straw powder is then subjected to pyrolysis and carbonization. During this stage, the calcium and zinc ions located in the straw fiber structure promote dehydration, cross-linking, and condensation reactions, further forming double bonds and aromatic structures. This reduces the content of oxygen-containing hydrophilic groups on the surface of the pyrolysis char, enhancing hydrophobicity. Consequently, the prepared modified straw pyrolysis char adsorbent possesses a larger adsorption capacity and improves its adsorption performance for bisphenol A in water.

[0009] Preferably, the calcium source is calcium chloride, calcium nitrate, or calcium carbonate; the zinc source is zinc chloride, zinc sulfate, or zinc nitrate. This invention does not specifically limit the specific components of the calcium and zinc sources, and appropriate calcium and zinc sources can be selected according to requirements.

[0010] Preferably, the activation impregnation temperature is 65℃~70℃. This invention, by adjusting the activation impregnation temperature, promotes the penetration of calcium and zinc ions into the fiber structure of straw powder, catalyzes the hydrolysis of cellulose and hemicellulose, and also gradually evaporates moisture during the activation impregnation process, reducing subsequent processing time.

[0011] Preferably, the ratio of straw powder to water is 1g:40mL to 50mL. This invention does not limit the specific amount of water used; it can be selected according to actual needs.

[0012] Preferably, the pyrolysis carbonization is carried out under a nitrogen atmosphere with a nitrogen flow rate of 0.5 L / min to 0.6 L / min; the pyrolysis carbonization temperature is 450℃ to 500℃; and the pyrolysis carbonization time is 1 h to 1.5 h.

[0013] Using nitrogen for pyrolysis creates an oxygen-deficient or anaerobic environment. As an inert gas, nitrogen removes oxygen from the tubular furnace, ensuring that biomass undergoes thermal decomposition under anaerobic conditions rather than simple combustion, thus preserving its carbon skeleton structure. The anaerobic environment promotes the slow release of volatile components from within the biomass, forming a rich porous structure, and the nitrogen atmosphere also retains more oxygen-containing functional groups. The presence of oxygen leads to pore wall oxidation and collapse, reducing pore area, and oxygen also excessively oxidizes oxygen-containing functional groups, further decreasing their number.

[0014] Different pyrolysis temperatures significantly modulate the structure and adsorption performance of straw-modified biochar. At lower temperatures, reaching 400℃, biomass undergoes initial decomposition, resulting in low porosity and the retention of abundant oxygen-containing functional groups. Adsorption relies on hydrogen bonding, but tar clogs the pores, leading to an adsorption capacity of less than 100 mg / g. At sufficiently high pyrolysis temperatures, reaching 450℃–500℃, cellulose undergoes deep pyrolysis, resulting in optimal pore development. Zinc / calcium is converted into active nanocrystals, namely ZnO / porous CaCO3, which synergistically forms a triple adsorption mechanism of hydrophobic interactions, π-π interactions, and metal complexation, thereby enhancing BPA adsorption. At excessively high temperatures, micropore collapse and graphitization intensify, functional groups disappear, zinc volatilizes and calcium sintersulates into CaCO3, and adsorption capacity decreases due to residual hydrophobic interactions.

[0015] Preferably, the pickling is performed by stirring with hydrochloric acid at a concentration of 0.1 mol / L to 0.2 mol / L for 30 to 50 minutes; the water washing is performed by washing with water until neutral.

[0016] The purpose of washing biochar is to remove soluble salts and alkaline ash to prevent water pollution or interference with adsorption; to dissolve pore blockages and increase specific surface area; and to adjust the pH to neutral to prevent biochar from altering the acidity or alkalinity of the water being treated. The purpose of acid washing is to deeply deash and dissolve metal oxides / carbonates, reducing ash occupation of pores; to increase surface acidic groups and enhance hydrogen bond adsorption capacity; and to expand the material's applicability under acidic conditions.

[0017] Preferably, the straw powder has a particle size of 60-80 mesh; the solvent is water.

[0018] Preferably, the straw powder is soybean straw powder. This invention does not limit the specific source of the straw powder; soybean straw powder can be used, or it can be selected according to actual needs.

[0019] Preferably, the straw powder is obtained by soaking and washing the straw in water to remove surface ash and impurities, drying it, and then crushing and sieving it. The straw is soybean straw, and the soaking and washing time in water is 1 to 3 hours.

[0020] The second aspect of this invention provides a modified straw pyrolysis carbon adsorbent, which is prepared using the preparation method of the modified straw pyrolysis carbon adsorbent described in the first aspect.

[0021] The third aspect of this invention provides an application of the modified straw pyrolysis char adsorbent described in the second aspect as an adsorbent for the removal of bisphenol A from water.

[0022] Preferred, specific application method: The modified straw pyrolysis char adsorbent was placed in an aqueous solution containing bisphenol A for bisphenol A adsorption. After the adsorption process reached equilibrium, it was filtered. The concentration of bisphenol A in the aqueous solution was 100 mg / L to 200 mg / L, and the pH was 7 ± 0.2. The dosage of the modified straw pyrolysis char adsorbent was 0.25 g / L to 1.0 g / L. The adsorption temperature was 25℃ ± 0.5℃.

[0023] Preferably, during the adsorption process, the rotation speed is adjusted to 150 rpm to 180 rpm.

[0024] The beneficial effects of this invention are: 1. This invention utilizes calcium and zinc sources as modifiers to activate, impregnate, and pyrolyze straw powder, thereby enabling the prepared modified straw pyrolysis carbon adsorbent to have a larger adsorption capacity, improve the adsorption performance of bisphenol A in water, and solve the problem of low adsorption capacity of rice straw pyrolysis carbon for bisphenol A in water prepared by existing methods.

[0025] 2. This invention primarily uses calcium and zinc sources as modifiers. The straw powder is activated and impregnated with a modifier solution, allowing calcium and zinc ions to penetrate into the fiber structure of the straw powder and catalyze the hydrolysis of cellulose and hemicellulose. The activated and impregnated straw powder is then subjected to pyrolysis and carbonization. During this stage, the calcium and zinc ions located in the straw fiber structure promote dehydration, cross-linking, and condensation reactions, further forming double bonds and aromatic structures. This reduces the content of oxygen-containing hydrophilic groups on the surface of the pyrolysis char, enhancing hydrophobicity. Consequently, the prepared modified straw pyrolysis char adsorbent possesses a larger adsorption capacity and improves its adsorption performance for bisphenol A in water.

[0026] 3. The modified straw pyrolysis char adsorbent of the present invention can adsorb and remove bisphenol A from water at a dosage of 0.25 g / L to 1.0 g / L, with a removal rate of up to 79% and an adsorption capacity of more than 316 mg / g. Attached Figure Description

[0027] Figure 1 A flowchart illustrating the preparation process of the modified straw pyrolysis char adsorbent provided for embodiments of the present invention.

[0028] Figure 2 Scanning electron microscope (SEM) images of the modified straw pyrolysis char adsorbent prepared in Example 1 and the unmodified straw pyrolysis biochar prepared in Comparative Example 6. Specifically, (a) and (b) are SEM images of the unmodified straw pyrolysis biochar prepared in Comparative Example 6 at the same magnification of 10K at two different locations; (c) and (d) are SEM images of the modified straw pyrolysis char adsorbent prepared in Example 1 at the same magnification of 10K at two different locations.

[0029] Figure 3 The images show scanning electron microscope (SEM) images of the modified straw pyrolysis char adsorbent prepared in Example 1 and the unmodified straw pyrolysis biochar prepared in Comparative Example 6 at different magnifications. Specifically, (a) to (c) are SEM images of the unmodified straw pyrolysis biochar prepared in Comparative Example 6 at magnifications of 10K, 50K, and 100K, respectively; and (d) to (f) are SEM images of the modified straw pyrolysis char adsorbent prepared in Example 1 at magnifications of 10K, 50K, and 100K, respectively.

[0030] Figure 4 The image shows the energy dispersive spectroscopy (EDS) elemental analysis of the unmodified straw pyrolysis biochar prepared in Comparative Example 6. (a) through (d) show the elemental distributions of C, O, Ca, and Zn, respectively.

[0031] Figure 5 The image shows the energy dispersive spectroscopy (EDS) elemental analysis of the modified straw pyrolysis char adsorbent prepared in Example 1. (a) through (d) show the elemental distributions of C, O, Ca, and Zn, respectively.

[0032] Figure 6 The image shows the total energy spectrum of the unmodified straw pyrolysis biochar prepared in Comparative Example 6. Figure 6 The illustration shows the atomic percentage of each element.

[0033] Figure 7 The image shows the total energy spectrum of the modified straw pyrolysis char adsorbent prepared in Example 1. Figure 7 The illustration shows the atomic percentage of each element. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The technical solution of the present invention will be further described below through specific embodiments.

[0037] Unless otherwise specified, the methods described in the following embodiments and comparative examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0038] In the following embodiments and comparative examples, pyrolysis and carbonization were carried out in a tubular furnace, specifically a T-1400ST series vacuum tubular high-temperature furnace from Zhengzhou Tianzong Electrical Equipment Co., Ltd., using a high concentration of nitrogen to maintain the nitrogen atmosphere within the furnace. Soybean straw was obtained from Yutai County, Jining City, Shandong Province. The calcium source used in this invention was calcium chloride, and the zinc source was zinc chloride.

[0039] Example 1 like Figure 1 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0040] Step 2: Preparation of calcium-zinc modified straw pyrolysis char adsorbent: Zinc chloride and calcium chloride were used as modifiers. The raw materials were weighed according to the ratio of straw powder to modifier of 1g:10mmol and the molar ratio of zinc chloride to calcium chloride of 1:0.5.

[0041] 1 g of pretreated straw powder, 0.9088 g of zinc chloride, and 0.3699 g of calcium chloride were added to 50 mL of pure water and mixed and impregnated at 70 °C until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5 L / min, reaction temperature of 500 °C, and reaction time of 1 h. After the reaction was completed, the product was washed with 0.1 mol / L hydrochloric acid solution with stirring, then washed and filtered with pure water until the filtrate was neutral. The residue was dried at 60 °C to obtain calcium-zinc modified straw pyrolysis carbon adsorbent.

[0042] Example 2 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0043] Step 2: Preparation of calcium-zinc modified straw pyrolysis char adsorbent: Zinc chloride and calcium chloride were used as modifiers. The raw materials were weighed according to the ratio of straw powder to modifier of 1g:10mmol and the molar ratio of zinc chloride to calcium chloride of 3:2.

[0044] 1 g of pretreated straw powder, 0.8179 g of zinc chloride, and 0.4439 g of calcium chloride were added to 50 mL of pure water and mixed and impregnated at 70 °C until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.6 L / min, reaction temperature of 500 °C, and reaction time of 1 h. After the reaction was completed, the product was washed with 0.1 mol / L hydrochloric acid solution, stirred, and then washed and filtered with pure water until the filtrate was neutral. The residue was dried at 60 °C to obtain the calcium-zinc modified straw pyrolysis carbon adsorbent.

[0045] Comparative Example 1 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0046] Step 2: Preparation of calcium-zinc modified straw pyrolysis char adsorbent: Zinc chloride and calcium chloride were used as modifiers. The raw materials were weighed according to the ratio of straw powder to modifier of 1.5g:10mmol and the molar ratio of zinc chloride to calcium chloride of 1:0.5.

[0047] 1.5 g of pretreated straw powder, 0.9088 g of zinc chloride, and 0.3699 g of calcium chloride were added to 50 mL of pure water and mixed and impregnated at 70 °C until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5 L / min, reaction temperature of 500 °C, and reaction time of 1 h. After the reaction was completed, the product was washed with 0.1 mol / L hydrochloric acid solution, stirred, and then washed and filtered with pure water until the filtrate was neutral. The residue was dried at 60 °C to obtain the calcium-zinc modified straw pyrolysis carbon adsorbent.

[0048] Comparative Example 2 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0049] Step 2: Preparation of zinc-modified straw pyrolysis char adsorbent: Using zinc chloride as a modifier, the raw materials were weighed according to the ratio of straw powder to modifier of 1g:5mmol.

[0050] 1g of pretreated straw powder and 0.682g of zinc chloride were added to 50mL of pure water and mixed and impregnated at 70℃ until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5L / min, reaction temperature of 500℃, and reaction time of 1h. After the reaction was completed, the product was washed with 0.1mol / L hydrochloric acid solution with stirring, then washed with pure water and filtered until the filtrate was neutral. The residue was dried at 60℃ to obtain the zinc-modified straw pyrolysis carbon adsorbent.

[0051] Comparative Example 3 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0052] Step 2: Preparation of calcium-modified straw pyrolysis char adsorbent: Using calcium chloride as a modifier, the raw materials were weighed according to the ratio of straw powder to modifier of 1g:5mmol.

[0053] 1g of pretreated straw powder and 0.555g of calcium chloride were added to 50mL of pure water and mixed and impregnated at 70℃ until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5L / min, reaction temperature of 500℃, and reaction time of 1h. After the reaction was completed, the product was washed with 0.1mol / L hydrochloric acid solution with stirring, then washed with pure water and filtered until the filtrate was neutral. The residue was dried at 60℃ to obtain calcium-modified straw pyrolysis carbon adsorbent.

[0054] Comparative Example 4 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0055] Step 2: Preparation of zinc-modified straw pyrolysis char adsorbent: Using zinc chloride as a modifier, the raw materials were weighed according to the ratio of straw powder to modifier of 1g:3mmol.

[0056] 1 g of pretreated straw powder and 0.409 g of zinc chloride were added to 50 mL of pure water and mixed and impregnated at 70 °C until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5 L / min, reaction temperature of 500 °C, and reaction time of 1 h. After the reaction was completed, the product was washed with 0.1 mol / L hydrochloric acid solution with stirring, then washed and filtered with pure water until the filtrate was neutral. The residue was dried at 60 °C to obtain the zinc-modified straw pyrolysis carbon adsorbent.

[0057] Comparative Example 5 A method for preparing a modified straw pyrolysis char adsorbent includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0058] Step 2: Preparation of calcium-modified straw pyrolysis char adsorbent: Using calcium chloride as a modifier, the raw materials were weighed according to the ratio of straw powder to modifier of 1 g: 3 mmol.

[0059] 1g of pretreated straw powder and 0.333g of calcium chloride were added to 50mL of pure water and mixed and impregnated at 70℃ until the water evaporated. The activated and impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5L / min, reaction temperature of 500℃, and reaction time of 1h. After the reaction was completed, the product was washed with 0.1mol / L hydrochloric acid solution with stirring, then washed and filtered with pure water until the filtrate was neutral. The residue was dried at 60℃ to obtain calcium-modified straw pyrolysis carbon adsorbent.

[0060] Comparative Example 6 A method for preparing straw pyrolysis biochar includes the following steps: Step 1: Straw pretreatment: The straw is thoroughly soaked and washed in pure water to remove impurities, then dried in a blower dryer and pulverized through a 60-mesh sieve to obtain straw powder.

[0061] Step 2: Preparation of straw pyrolysis biochar: 1g of pretreated straw powder was added to 50mL of pure water and mixed and impregnated at 70℃ until the water evaporated. The impregnated straw powder was dried to remove residual moisture, then spread evenly in a rectangular ceramic boat and pyrolyzed and carbonized in a vacuum tube furnace under a nitrogen atmosphere. The pyrolysis and carbonization reaction conditions were: nitrogen flow rate of 0.5L / min, reaction temperature of 500℃, and reaction time of 1h. After the reaction was completed, the product was washed with 0.1mol / L hydrochloric acid solution with stirring, then washed with pure water and filtered until the filtrate was neutral. The residue was dried at 60℃ to obtain straw pyrolysis biochar.

[0062] Table 1 Comparison of different modifiers and dosages Surface morphology analysis: The surface morphology of the modified straw pyrolysis biochar adsorbent prepared in Example 1 and the unmodified straw pyrolysis biochar prepared in Comparative Example 6 were analyzed, and the results are as follows: Figure 2 and Figure 3 As shown. For ease of description, the modified straw pyrolysis biochar adsorbent prepared in Example 1 is denoted as BC-Zn / Ca; the unmodified straw pyrolysis biochar prepared in Comparative Example 6 is denoted as BC.

[0063] Depend on Figure 2 and Figure 3 Scanning electron microscopy (SEM) images show that Ca and Zn modification significantly affect the surface morphology of straw pyrolysis biochar. The unmodified straw pyrolysis biochar surface is relatively smooth, with only a few irregular pores and cracks. In contrast, the surface of the Ca and Zn-modified straw pyrolysis biochar adsorbent becomes noticeably rougher, exhibiting numerous pores and irregular structures. This indicates that the introduction of Ca and Zn promotes pore formation, increases the specific surface area, and thus improves adsorption performance.

[0064] Furthermore, in the unmodified straw pyrolysis biochar prepared in Comparative Example 6, some straw fiber structures could still be observed. However, in the modified straw pyrolysis biochar adsorbent of Example 1 of this invention, modified with Ca and Zn, the fiber structure was destroyed, forming more fragments and irregular structures. This is mainly because calcium and zinc ions promote the dehydration, cross-linking, and condensation reactions of straw, leading to the reorganization of the fiber structure.

[0065] like Figure 3 From the microstructure of the modified straw pyrolysis char adsorbent modified with Ca and Zn in Example 1 of this invention, some fine particles or nanocrystal structures can also be observed. This is mainly related to the conversion of zinc / calcium into active nanocrystals, such as ZnO / porous CaCO3. The formation of these nanocrystals helps to enhance the adsorption capacity of the adsorbent.

[0066] In summary, the embodiments of the present invention significantly improved the surface morphology of straw pyrolysis biochar through Ca and Zn modification, increased the pore structure and roughness, and generated ZnO / porous CaCO3 active nanocrystals, which is beneficial to improving its adsorption performance for bisphenol A in water.

[0067] Energy dispersive spectroscopy elemental analysis: Energy dispersive spectroscopy (EDS) was performed on the modified straw pyrolysis biochar adsorbent prepared in Example 1 and the unmodified straw pyrolysis biochar prepared in Comparative Example 6. The results are as follows: Figures 4 to 7 As shown.

[0068] Depend on Figures 4 to 7 Analysis shows that in the unmodified straw pyrolysis biochar prepared in Comparative Example 6, the atomic percentage of carbon is as high as 84.35%, oxygen is 14.46%, and other elements account for a very low proportion. This indicates that the unmodified straw pyrolysis biochar is mainly composed of carbon and oxygen.

[0069] In the modified straw pyrolysis char adsorbent prepared in Example 1, the atomic percentage of carbon decreased to 51.22%, while the oxygen content increased to 20.74%. This indicates that other elements were introduced during the modification process, altering the relative contents of carbon and oxygen. Specifically, calcium and zinc were significantly introduced into the modified straw pyrolysis char adsorbent, with atomic percentages of 8.72% and 10.34%, respectively. Furthermore, small amounts of sodium, magnesium, aluminum, and potassium were also introduced. This demonstrates that zinc and calcium were successfully loaded onto the biochar during the modification process.

[0070] The following is a detailed description of the application of the modified straw pyrolysis carbon adsorbent prepared in the above embodiments as an adsorbent for the removal of bisphenol A from water.

[0071] Application Example 1 The application method of using the modified straw pyrolysis char adsorbent prepared in Example 1 as an adsorbent for the removal of bisphenol A from water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25℃±0.5℃.

[0072] Application Example 2 The application method of using the modified straw pyrolysis char adsorbent prepared in Example 1 as an adsorbent for the removal of bisphenol A from water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 200mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25℃±0.5℃.

[0073] Application Example 3 The application method of using the modified straw pyrolysis char adsorbent prepared in Example 2 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.02g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0074] Application Example 4 The application method of using the modified straw pyrolysis char adsorbent prepared in Example 2 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.02g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 200mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0075] Application Comparative Example 1 The application method of the modified straw pyrolysis char adsorbent prepared in Comparative Example 1 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0076] Application Comparative Example 2 The application method of the modified straw pyrolysis char adsorbent prepared in Comparative Example 2 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0077] Application Comparative Example 3 The application method of the modified straw pyrolysis char adsorbent prepared in Comparative Example 3 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0078] Application Comparative Example 4 The application method of the modified straw pyrolysis char adsorbent prepared in Comparative Example 4 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0079] Application Comparative Example 5 The application method of the modified straw pyrolysis char adsorbent prepared in Comparative Example 5 as an adsorbent for the removal of bisphenol A in water includes the following steps: 0.01g of modified straw pyrolysis char adsorbent was placed into a 100mL Erlenmeyer flask containing 40mL of 100mg / L bisphenol A solution. The initial pH was adjusted to 7.0±0.2. The flask was then shaken at 150rpm for 12h in a water bath at 25±0.5℃.

[0080] To further verify the effectiveness of the modified straw pyrolysis char adsorbent prepared in the embodiments of the present invention, the modified straw pyrolysis char adsorbent prepared in the above embodiments and comparative examples was used for bisphenol A removal from water. After adsorption was completed, the adsorbed solution was taken as the test sample, filtered using a 0.22 μm syringe filter, and 0.5 mL of the solution was taken to determine the bisphenol A concentration of the final supernatant using high performance liquid chromatography. Three parallel experiments were conducted, and the specific data are shown in Table 2.

[0081] Table 2 Total Bisphenol A Concentration in Initial Solution and Adsorption Termination Solution Note: The initial solution is the bisphenol A solution before adsorption; the adsorption termination solution is the solution after adsorption.

[0082] As shown in Table 2, compared with Comparative Example 1, the modified straw pyrolysis char adsorbent of Example 1 of this invention exhibits significantly better removal rate and adsorption capacity of bisphenol A in water than the modified straw pyrolysis char adsorbent of Comparative Example 1. This indicates that the addition of excessive straw powder leads to a lower total amount of calcium and zinc ions in the prepared modifier, which is detrimental to the adsorption and removal of bisphenol A from water. Therefore, a straw powder to modifier ratio of 1g:10mmol is more conducive to the removal of bisphenol A from water.

[0083] Furthermore, as the concentration of bisphenol A in the water increases, when the concentration of bisphenol A in the water reaches 100 mg / L, the modified straw pyrolysis carbon adsorbent prepared in Example 1 of this invention achieves a removal rate of approximately 80% for bisphenol A in the water, and the adsorption capacity is significantly higher than that of the modified straw pyrolysis carbon adsorbent prepared in Comparative Example 1.

[0084] When the concentration of bisphenol A in water reaches 200 mg / L, the removal rate of bisphenol A in water by the modified straw pyrolysis carbon adsorbent prepared in Example 1 of this invention is reduced, basically reaching a removal effect of 50%.

[0085] The results from Comparative Examples 1, 2, and 3 show that the adsorption capacity of biochar prepared using zinc chloride or calcium chloride alone is relatively low compared to that of biochar modified with both zinc chloride and calcium chloride.

[0086] The results from Comparative Examples 2 and 4 show that the adsorption capacity of the adsorbent increases with the increase of zinc chloride dosage. Similarly, the results from Comparative Examples 3 and 5 also show that the dosage of calcium chloride is positively correlated with the adsorption capacity of the adsorbent.

[0087] In summary, the modified straw pyrolysis carbon adsorbent prepared in Example 1 of this invention has a high adsorption capacity for removing bisphenol A from water. The preparation process of this invention can not only effectively utilize soybean straw as a resource, but also effectively remove bisphenol A from water, thus achieving the joint treatment of straw and wastewater.

[0088] This is mainly attributed to the use of calcium and zinc sources as modifiers, employing a modifier solution to activate and impregnate straw powder, allowing calcium and zinc ions to penetrate into the fiber structure of the straw powder and catalyze the hydrolysis of cellulose and hemicellulose. In this invention, the activated and impregnated straw powder is then subjected to pyrolysis and carbonization. During the pyrolysis and carbonization stage, calcium and zinc ions located in the straw fiber structure promote dehydration, cross-linking, and condensation reactions, further forming double bonds and aromatic structures. This reduces the content of oxygen-containing hydrophilic groups on the surface of the pyrolysis char, enhancing hydrophobicity. Consequently, the prepared modified straw pyrolysis char adsorbent possesses a larger adsorption capacity and improves its adsorption performance for bisphenol A in water.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified straw pyrolysis char adsorbent, characterized in that, Includes the following steps: Using calcium and zinc sources as modifiers, straw powder is activated and impregnated with the modifier solution. After evaporation to remove the solvent, it is pyrolyzed and carbonized. Then, it is acid washed, water washed, and dried to obtain modified straw pyrolysis carbon adsorbent. The ratio of straw powder to modifier was 1g:10mmol; the molar ratio of zinc source to calcium source was 1:0.4-1.

5.

2. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, The calcium source is calcium chloride, calcium nitrate, or calcium carbonate; the zinc source is zinc chloride, zinc sulfate, or zinc nitrate.

3. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, The activation impregnation temperature is 65℃~70℃.

4. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, The ratio of straw powder to water is 1g:40mL~50mL.

5. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, The pyrolysis carbonization is carried out under a nitrogen atmosphere with a nitrogen flow rate of 0.5 L / min to 0.6 L / min; the pyrolysis carbonization temperature is 450℃ to 500℃; and the pyrolysis carbonization time is 1 h to 1.5 h.

6. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, Pickling involves stirring and washing with hydrochloric acid at a concentration of 0.1 mol / L to 0.2 mol / L for 30 to 40 minutes; water washing involves washing with water until the solution is neutral.

7. The method for preparing the modified straw pyrolysis char adsorbent according to claim 1, characterized in that, The straw powder has a particle size of 60-80 mesh; the solvent is water.

8. A modified straw pyrolysis char adsorbent, characterized in that, It was prepared using the preparation method of the modified straw pyrolysis carbon adsorbent according to any one of claims 1 to 7.

9. An application of a modified straw pyrolysis char adsorbent as an adsorbent for the removal of bisphenol A from water, characterized in that, The modified straw pyrolysis carbon adsorbent is the modified straw pyrolysis carbon adsorbent as described in claim 8.

10. The application of the modified straw pyrolysis char adsorbent according to claim 9 as an adsorbent for the removal of bisphenol A from water, characterized in that, The specific application method is as follows: The modified straw pyrolysis char adsorbent was placed in an aqueous solution containing bisphenol A for bisphenol A adsorption, and filtered after the adsorption process reached equilibrium. In the aqueous solution containing bisphenol A, the concentration of bisphenol A is 100 mg / L to 200 mg / L, and the pH is 7 ± 0.2; the dosage of modified straw pyrolysis char adsorbent is 0.25 g / L to 1.0 g / L; and the adsorption temperature is 25℃ ± 0.5℃.

Images