A porous biochar and non-activated preparation method and application thereof

Abstract

A kind of porous biochar and its non-activated preparation method and application, biomass precursor is mixed with KOH solution, is placed in hydrothermal reactor, and solid-liquid mixture is obtained;The solid-liquid mixture is placed in a container, deionized water is added, and the liquid is collected by repeated washing;Add HCl dropwise to the liquid, and let the precipitate stand still, then dry after centrifugal washing to obtain a solid product;The solid product is carbonized in a nitrogen atmosphere at 300-500 DEG C, and then washed with water and dried to obtain a solid product;The obtained solid product is carbonized in a nitrogen atmosphere at 900 DEG C, and then washed with water and dried to obtain a porous biochar.The porous biochar prepared by the non-activated process provided by the application can efficiently load organic pollutants, and the adsorption capacity of phthalate can reach 999.33 mg / g, which can be used for water environment remediation.

Description

Technical Field

[0001] This invention belongs to the field of biomass waste resource utilization and water environment remediation, and more specifically, relates to a porous biochar and its non-activated preparation method and application. Background Technology

[0002] Porous carbon, such as activated carbon, is a multifunctional and high-value material that can perform functions such as storage, filtration, purification, and enrichment. It is widely used in industry, medicine, agriculture, aerospace, energy, and healthcare, with huge demand. The performance of porous carbon depends on its pore structure, mainly including specific surface area, pore size distribution, and pore volume. In recent years, the preparation of porous carbon based on agricultural and forestry biomass (referred to as porous biochar) has become a cutting-edge research topic, enabling the simultaneous resource recovery from waste and the low-cost preparation of porous carbon.

[0003] In the preparation of porous biochar, pyrolysis coupled with activation is a crucial process that determines the pore structure of the biochar. During pyrolysis, physical activation requires reactant gases such as carbon dioxide and water vapor, while chemical activation requires chemical reagents such as potassium hydroxide, phosphoric acid, zinc chloride, and potassium formate. Porous biochar prepared by coupled chemical activation exhibits a more developed pore structure. Currently, most commercially available porous biochar (activated carbon) employs a pyrolysis coupled with chemical reagent activation process. During chemical reagent activation, the high temperature generates highly reactive elemental metals or metal oxides, and the activator itself or its derivatives can corrode equipment during pyrolysis, leading to difficulties in mass production and high production costs.

[0004] In conclusion, optimizing the preparation process of porous biochar and reducing or eliminating the use of activators during pyrolysis can lower costs, reduce equipment wear and potential environmental pollution, and is an important foundation and prerequisite for the upgrading and transformation of the porous biochar industry. Summary of the Invention

[0005] Technical Problem Solved: This invention provides a porous biochar, its non-activated preparation method, and its application. The method employs alkaline humification, acid precipitation, low-temperature carbonization, and high-temperature carbonization processes. By first dissolving biomass, then precipitating it, the pore structure is reshaped. After low-temperature and high-temperature carbonization shaping, a micropore-dominated porous biochar is formed. The resulting carbon material possesses a well-developed pore structure. As an adsorbent, this carbon material exhibits extremely high removal efficiency for organic pollutants in aquatic environments.

[0006] Technical Solution: A method for preparing porous biochar without activation, comprising the following steps: Step 1, alkaline humification: Biomass precursor is mixed with KOH solution and placed in a hydrothermal reactor at a temperature of 160–260℃ for 2–5 hours. After cooling to room temperature, the solid-liquid mixture is removed. Step 2, acid precipitation: The solid-liquid mixture obtained in Step 1 is placed in a container, deionized water is added, and the mixture is repeatedly washed and the liquid is collected. HCl is added dropwise to the liquid to adjust the pH to 1. The mixture is allowed to stand to stabilize the precipitate. The precipitate is then centrifuged, washed with deionized water, and dried to obtain a solid product. Step 3, low-temperature carbonization: The solid product from Step 2 is carbonized in a nitrogen atmosphere at 300–500℃. After cooling, it is washed with water and dried to obtain a solid product. Step 4, high-temperature carbonization: The solid product from Step 3 is carbonized in a nitrogen atmosphere at 900℃. After cooling, it is washed with water and dried to obtain porous biochar.

[0007] Preferably, the above-mentioned biomass precursor is bamboo.

[0008] No activator is added during the high-temperature carbonization in step 4.

[0009] Preferably, the KOH concentration in step 1 is 20-100 g / L, and the solid-liquid ratio of the biomass precursor to the KOH solution is 200-400 g / L.

[0010] Preferably, in step 3, the carbonization time is 2-4 hours, the heating rate is 2-10℃ / min, and the nitrogen flow rate is maintained at 50-200mL / min.

[0011] Preferably, in step 4, the carbonization time is 1-2 hours, the heating rate is 2-10℃ / min, and the nitrogen flow rate is maintained at 50-200mL / min.

[0012] The porous biochar material prepared by the above method.

[0013] The specific surface area of ​​the aforementioned porous biochar material reaches 1627 m². 2 / g, pore volume up to 0.85cm 3 / g.

[0014] The above-mentioned porous biochar materials are used in the remediation of aquatic environments.

[0015] The above-mentioned porous biochar materials are used in the removal of phthalate organic pollutants from water.

[0016] Beneficial effects: (1) The non-activated method for preparing porous biochar provided by this invention, compared with the prior art, adopts alkaline humification, acid precipitation, low-temperature carbonization and high-temperature carbonization processes. By first dissolving biomass and then precipitating, the pore structure is reshaped. After low-temperature carbonization and high-temperature carbonization shaping, micropore-dominated porous biochar is formed, avoiding the use of activators during thermal decomposition. (2) The non-activated method for preparing porous biochar provided by this invention, compared with the prior art, can prepare carbon-based materials with well-developed pore structure and a specific surface area of ​​1627 m². 2 / g, pore volume up to 0.85cm 3 / g, which is much higher than that of activated carbon and other porous carbon materials sold on the market. (3) The present invention provides a non-activated method for preparing porous biochar, which is simple to prepare, low in cost, and can be used for large-scale promotion. (4) The porous biochar prepared by the non-activated process provided by the present invention can efficiently load organic pollutants, and its adsorption capacity for phthalates can reach 999.33mg / g, which can be used for water environment remediation. Attached Figure Description

[0017] Figure 1 The nitrogen adsorption isotherms are for the biochar prepared in Example 1 and the comparative example.

[0018] Figure 2 The images show the pore size distribution of the biochar prepared in Example 1 and the comparative examples.

[0019] Figure 3 The images show the adsorption kinetic curve (a) and isotherm (b) of the porous biochar prepared in Example 1 for phthalates. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments.

[0021] Example 1

[0022] This embodiment provides a method for preparing porous biochar without activation and the resulting porous biochar material, including alkaline humification, acid precipitation, low-temperature carbonization, and high-temperature carbonization, specifically comprising the following steps:

[0023] Step 1, Alkali Humification: Collect bamboo waste, dry it at 110℃, crush it in a pulverizer, and pass it through a 100-mesh sieve. Mix bamboo biomass with 80g / L KOH solution at a ratio of 320g / L, place it in a hydrothermal reactor, set the temperature to 180℃, and continue for 4 hours. After cooling, remove the solid-liquid mixture.

[0024] Step 2, acid precipitation: Place the solid-liquid mixture obtained in Step 1 in a beaker, add deionized water, stir, and centrifuge to obtain a liquid product. Wash repeatedly and collect all the liquid. Add HCl dropwise to adjust the pH to 1, let the precipitate stand to stabilize (24h), centrifuge for 5min (8000r / min), wash with deionized water, and dry to obtain a solid product.

[0025] Step 3, low-temperature carbonization: Place the solid product from step 2 in a crucible and carbonize it at low temperature (300℃) in a muffle furnace for 2 hours. The heating rate is 10℃ / min, the nitrogen flow rate is maintained at 100mL / min, and the product is cooled to room temperature. It is then repeatedly rinsed with distilled water, filtered, kept at a constant temperature of 80℃, dried, and stored in a sealed glass bottle for later use.

[0026] Step 4, high-temperature carbonization: The solid product from step 3 is placed in a crucible and carbonized at high temperature (900℃) in a muffle furnace for 2 hours. The heating rate is 5℃ / min and the nitrogen flow rate is maintained at 100mL / min. After cooling, the product is washed with water and dried to obtain biochar material 1 (C1).

[0027] Comparative Example 1

[0028] Step 1: Collect bamboo waste, dry it at 110℃, crush it in a pulverizer, and pass it through a 100-mesh sieve. Mix the bamboo biomass with deionized water (320g / L), place it in a hydrothermal reactor, set the temperature to 180℃, and continue for 4 hours. After cooling, remove the solid-liquid mixture.

[0029] Step 2: Collect the solid product using a vacuum filtration device and dry it at 100℃ for 12h. Mix the solid product with potassium formate (mass ratio 1:1) and place it in a crucible. Carbonize it at high temperature (900℃) in a muffle furnace for 2h with a heating rate of 5℃ / min and a nitrogen flow rate of 100mL / min. After cooling, acid wash, water wash, and drying are performed to obtain biochar 2 (C2).

[0030] Comparative Example 2

[0031] Step 1: Collect bamboo waste, dry it at 110℃, crush it in a pulverizer, and pass it through a 100-mesh sieve. Mix the bamboo biomass with deionized water (320g / L), place it in a hydrothermal reactor, set the temperature to 180℃, and continue for 4 hours. After cooling, remove the solid-liquid mixture.

[0032] Step 2: Collect the solid product using a vacuum filtration device and dry it at 100℃ for 12 hours. Place the solid product in a crucible and carbonize it at high temperature (900℃) in a muffle furnace for 2 hours with a heating rate of 5℃ / min and a nitrogen flow rate of 100mL / min. After cooling, acid wash, water wash, and drying are performed to obtain biochar 3 (C3).

[0033] Results analysis:

[0034] The properties of the porous biochar prepared in Example 1 were tested and identified. Figure 1 These are nitrogen adsorption curves for the porous biochar (C1) prepared in this embodiment and the carbon materials (C2 and C3) prepared in comparative examples 1 and 2. The specific surface area of ​​C1 can reach 1965 m². 2 / g, with a pore volume up to 0.96cm³ 3 / g, C2 specific surface area can reach 1366m² 2 / g, with a pore volume up to 0.11cm³ 3 / g, C3 specific surface area can reach 8m² 2 / g, pore volume up to 0.02cm 3 / g. It can be seen that although Example 1 did not undergo activation treatment during the high-temperature pyrolysis process, its pore surface area and pore volume were significantly higher than those of the carbon material in Comparative Example 1 that underwent high-temperature activation treatment. This data still indicates that without the strategy of this invention or the high-temperature activation strategy, its pore structure is underdeveloped.

[0035] Figure 2 This is a pore size distribution diagram of the porous biochar prepared in Example 1. It shows that micropores (<2 nm) are dominant. Although it did not undergo a similar high-temperature activation process, it shows some similarity to the pore-forming process induced by potassium formate activation. Without the process of this invention or the high-temperature activation process, the number of pores of each size is extremely limited. The porous biochar of this invention has pore sizes mainly concentrated between 1-2 nm, which can efficiently capture small molecule compounds such as carbon dioxide, volatile and semi-volatile organic pollutants.

[0036] Example 2

[0037] This embodiment provides a method for preparing porous biochar without activation and the resulting porous biochar material, including alkaline humification, acid precipitation, low-temperature carbonization, and high-temperature carbonization, specifically comprising the following steps:

[0038] Step 1, Alkali Humification: Collect bamboo waste, dry it at 110℃, crush it in a pulverizer, and pass it through a 100-mesh sieve. Mix bamboo biomass with 20g / L KOH solution at a ratio of 200g / L, place it in a hydrothermal reactor, set the temperature to 160℃, and continue for 2 hours. After cooling, remove the solid-liquid mixture.

[0039] Step 2, acid precipitation: Place the solid-liquid mixture obtained in Step 1 in a beaker, add deionized water, stir, and centrifuge to obtain a liquid product. Wash repeatedly and collect all the liquid. Add HCl dropwise to adjust the pH to 1, let the precipitate stand to stabilize (24h), centrifuge for 5min (8000r / min), wash with deionized water, and dry to obtain a solid product.

[0040] Step 3, low-temperature carbonization: Place the solid product from step 2 in a crucible and carbonize it at low temperature (400℃) in a muffle furnace for 3 hours. The heating rate is 5℃ / min, the nitrogen flow rate is maintained at 50mL / min, and the product is cooled to room temperature. It is then repeatedly rinsed with distilled water, filtered, kept at a constant temperature of 80℃, dried, and stored in a sealed glass bottle for later use.

[0041] Step 4, high-temperature carbonization: Place the solid product from step 3 in a crucible and carbonize it at high temperature (900℃) in a muffle furnace for 1 hour. The heating rate is 2℃ / min, and the nitrogen flow rate is maintained at 50mL / min. After cooling, wash with water and dry to obtain porous biochar.

[0042] Example 3

[0043] This embodiment provides a method for preparing porous biochar without activation and the resulting porous biochar material, including alkaline humification, acid precipitation, low-temperature carbonization, and high-temperature carbonization, specifically comprising the following steps:

[0044] Step 1, Alkali Humification: Collect bamboo waste, dry it at 110℃, crush it in a pulverizer, and pass it through a 100-mesh sieve. Mix bamboo biomass with 100g / L KOH solution at a ratio of 400g / L, place it in a hydrothermal reactor, set the temperature to 260℃, and continue for 5 hours. After cooling, remove the solid-liquid mixture.

[0045] Step 2, acid precipitation: Place the solid-liquid mixture obtained in Step 1 in a beaker, add deionized water, stir, and centrifuge to obtain a liquid product. Wash repeatedly and collect all the liquid. Add HCl dropwise to adjust the pH to 1, let the precipitate stand to stabilize (24h), centrifuge for 5min (8000r / min), wash with deionized water, and dry to obtain a solid product.

[0046] Step 3, low-temperature carbonization: Place the solid product from step 2 in a crucible and carbonize it at low temperature (500℃) in a muffle furnace for 4 hours. The heating rate is 5℃ / min, the nitrogen flow rate is maintained at 200mL / min, and the product is cooled to room temperature. It is then repeatedly rinsed with distilled water, filtered, kept at a constant temperature of 80℃, dried, and stored in a sealed glass bottle for later use.

[0047] Step 4, high-temperature carbonization: The solid product from step 3 is placed in a crucible and carbonized at high temperature (900℃) in a muffle furnace for 1.5 hours. The heating rate is 10℃ / min and the nitrogen flow rate is maintained at 200mL / min. After cooling, the product is washed with water and dried to obtain porous biochar.

[0048] Example 4

[0049] This embodiment provides an application of porous biochar prepared by a non-activation method in the remediation of aquatic environments. Specifically, C1 prepared in Example 1 is used as an adsorbent to adsorb emerging organic pollutants in the aquatic environment—phthalates. The specific steps are as follows:

[0050] A 20 mL solution of phthalate (diethyl phthalate, DEP, 50 mg / L) prepared with CaCl2 (0.01 mol / L) was placed in a brown glass bottle. 2 mg of the porous biochar prepared in Example 1 was added, and the solution was shaken at 25 °C (200 rpm). Samples were collected at time intervals, and after high-speed centrifugation, the concentration of phthalate in the supernatant was determined by high-performance liquid chromatography (HPLC). The adsorption capacity was calculated by the difference method. Different phthalate concentrations were set to further study the adsorption potential.

[0051] Results analysis:

[0052] The adsorption kinetic curve and isotherm of porous biochar for phthalates in this embodiment are as follows: Figure 3 As shown, a is the adsorption kinetics curve, and b is the isotherm. From Figure 3 (a) It can be seen that the adsorption rate is relatively fast, and equilibrium can be reached within 2-4 hours; from Figure 3 (b) indicates a huge adsorption potential, reaching 999.33 mg / g. The maximum adsorption capacities of C2 and C3 are 162.66 mg / g and 306.78 mg / g, respectively. The adsorption performance of the biochar material of the present invention is far superior to that of conventional biochar (non-activated) and conventional activated biochar.

[0053] The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of the invention described herein. Furthermore, the background art is intended to illustrate the current state of development and significance of the technology and is not intended to limit the present invention or its application areas.

Claims

1. A method for preparing porous biochar without activation, characterized in that, Step 1, Alkaline Humification: The biomass precursor is mixed with KOH solution and placed in a hydrothermal reactor. The temperature is set to 160~260 ℃ and maintained for 2~5 h. After cooling to room temperature, the solid-liquid mixture is removed. The biomass precursor is bamboo. Step 2, Acid Precipitation: The solid-liquid mixture obtained in Step 1 is placed in a container, deionized water is added, and the mixture is repeatedly washed and the liquid is collected. HCl is added dropwise to the liquid to adjust the pH to 1. The mixture is allowed to stand to stabilize the precipitate. The precipitate is then centrifuged, washed with deionized water, and dried to obtain a solid product. Step 3, Low-Temperature Carbonization: The solid product from Step 2 is carbonized in a nitrogen atmosphere at 300~500 ℃. After cooling, it is washed with water and dried to obtain a solid product. Step 4, High-Temperature Carbonization: The solid product from Step 3 is carbonized in a nitrogen atmosphere at 900 ℃. After cooling, it is washed with water and dried to obtain porous biochar. No activator is added during high-temperature carbonization.

2. The method for preparing porous biochar without activation according to claim 1, characterized in that, In step 1, the KOH concentration is 20~100 g / L, and the solid-liquid ratio of the biomass precursor to the KOH solution is 200~400 g / L.

3. The method for preparing porous biochar without activation according to claim 1, characterized in that, In step 3, the carbonization time is 2-4 h, the heating rate is 2-10 ℃ / min, and the nitrogen flow rate is maintained at 50-200 mL / min.

4. The method for preparing porous biochar without activation according to claim 1, characterized in that, In step 4, the carbonization time is 1-2 h, the heating rate is 2-10 ℃ / min, and the nitrogen flow rate is maintained at 50-200 mL / min.

5. The porous biochar material prepared by any one of claims 1-4, characterized in that, The porous biochar material has a specific surface area of ​​1627 m². 2 / g, pore volume up to 0.85 cm³ 3 / g.

6. The application of the porous biochar material according to claim 5 in the remediation of aquatic environments.

7. The application of the porous biochar material according to claim 5 in the removal of phthalate organic pollutants from water.

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