A phosphorus-modified chestnut cupule biochar, its preparation method and application

Abstract

The present invention discloses a phosphorus-modified chestnut cupule biochar, its preparation method and application, belonging to the cross technology field of functional materials and environment. The phosphorus-modified chestnut cupule biochar is prepared from chestnut cupule waste, with a specific surface area of 179 m² / g, a micropore volume of 0.103 cm³ / g, and an average pore diameter of 8.61 nm. The preparation method is to first carry out high-temperature pyrolysis treatment under oxygen-limited conditions to obtain chestnut cupule biochar, and then mix it evenly with sodium dihydrogen phosphate powder and carry out hydrothermal reaction to obtain phosphorus-modified chestnut cupule biochar. The phosphorus-modified chestnut cupule biochar provided by the present invention has rich oxygen-containing functional groups and phosphorus-containing functional groups, and can achieve a removal rate of more than 90% for cadmium with a concentration of 200 mg / L in water. It can not only realize the resource utilization of chestnut cupule waste, but also achieve the efficient removal of cadmium in water, achieving the dual purpose of treating pollution with waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials and environmental cross - technology, and specifically relates to a phosphorus - modified chestnut cupule biochar, a preparation method thereof, and an application thereof. Background Technique

[0002] With the acceleration of the industrialization and agriculturalization processes, a large amount of heavy metals are discharged into the natural environment through a series of human activities such as electroplating, fertilization, and irrigation, posing a great potential threat to the ecological environment and human health. Cadmium is a typical heavy metal element widely distributed in nature, with high toxicity, non - degradability, and bio - accumulation. At present, the methods for treating cadmium pollution generally have disadvantages such as high cost, cumbersome preparation steps, and small application scope. Therefore, how to achieve efficient, economical, and green cadmium pollution treatment remains an environmental problem that urgently needs to be solved at present.

[0003] Biochar has advantages such as a large cation exchange capacity, strong adsorption ability, large specific surface area, and stable structure. As a low - cost, widely available, and environmentally friendly functional material, it plays an important role in the field of heavy metal pollution treatment. At present, there is no relevant report on preparing biochar from chestnut cupule waste under anaerobic or oxygen - limited conditions.

[0004] Single biochar has disadvantages such as low porosity, few adsorption sites, and few surface functional groups. Based on this, researchers have proposed a series of modification strategies for biochar, including mineral impregnation method, surface oxidation method, surface reduction method, and nano - metal loading method, etc. Although these methods have improved the performance of biochar to a certain extent, it is particularly important to select a modification method that is economically efficient, easy to prepare, and does not harm the environment in the actual application process.

[0005] Phosphorus doping is a modification strategy that can not only improve the performance of biochar but also be cost - effective. Phosphorus doping can activate pore formation and increase the specific surface area of biochar; phosphorus - containing functional groups are hydrophilic, can provide abundant electrons, and have excellent adsorption effects on various transition metal ions; orthophosphate is more soluble in water than other phosphorus - containing compounds and can form precipitates with most heavy metals through surface adsorption, cation substitution, and precipitation, etc. At present, the main methods for preparing phosphorus - modified biochar are, one is to pyrolyze after pretreating biomass with phosphate, and the other is to impregnate biochar obtained by pyrolyzing biomass with phosphate solution.

[0006] The Chinese invention patent with the authorization announcement number of CN 112675815B discloses a preparation method and application of boron - doped porous biochar. The boron - doped porous biochar prepared by the method solves the problem of poor adsorption capacity of the original biochar and can efficiently remove divalent iron ions in sewage.

[0007] The Chinese invention patent with the authorization announcement number CN 115869979A discloses a preparation method of porous nitrogen-doped lignin biochar and its application in mediating the reduction of hexavalent chromium. The porous nitrogen-doped lignin biochar prepared by this method can rapidly catalyze the reduction of hexavalent chromium in wastewater, and the removal rate of 20 mg / L hexavalent chromium can reach more than 99% within 15 minutes.

[0008] The Chinese invention patent with the authorization announcement number CN 114146701A discloses a preparation method and application of nitrogen / oxygen self-doped porous biochar. The method uses alfalfa plants rich in nitrogen and oxygen atoms as raw materials, and under the condition of no need for external nitrogen sources, concentrated acids or strong oxidants for oxidation, nitrogen / oxygen self-doped porous biochar is successfully prepared by calcination, which has good economic benefits and environmental protection significance. Summary of the Invention

[0009] Aiming at the deficiencies of the above prior art, the purpose of the present invention is to provide a phosphorus-modified chestnut cupule biochar and its preparation method, and apply it to the treatment of cadmium-containing wastewater, which can not only realize the resource utilization of chestnut cupule waste, but also realize the efficient removal of cadmium in water, achieving the dual purpose of treating pollution with waste.

[0010] In order to achieve the above purpose, the present invention is realized through the following technical solutions:

[0011] According to the first aspect of the present invention, there is provided a phosphorus-modified chestnut cupule biochar, which is prepared from chestnut cupule waste, and is characterized in that the phosphorus-modified chestnut cupule biochar has: a specific surface area of 179 m 2 / g, a micropore volume of 0.103 cm 3 / g, an average pore diameter of 8.61 nm, and contains rich oxygen-containing functional groups and phosphorus-containing functional groups.

[0012] According to the second aspect of the present invention, there is provided a preparation method of phosphorus-modified chestnut cupule biochar, which is characterized by including the following steps:

[0013] (1) Wash, dry and grind chestnut cupules, and after passing through a 20-mesh sieve, obtain cupule particles, place them in a muffle furnace, and perform high-temperature pyrolysis treatment under oxygen-limited conditions to obtain chestnut cupule biochar;

[0014] (2) Mix the obtained chestnut cupule biochar with sodium dihydrogen phosphate powder evenly, add deionized water, place it in a reaction kettle for hydrothermal reaction, and then wash the hydrothermal product and dry it in a vacuum drying oven to obtain phosphorus-modified chestnut cupule biochar.

[0015] Preferably, the chestnut cupules in step (1) are agricultural and forestry waste, collected in Yixing City, Jiangsu Province.

[0016] Preferably, the high-temperature pyrolysis conditions in step (1) are heating to 445 °C at a heating rate of 5 °C / min and continuously pyrolyzing for 6 h.

[0017] Preferably, the doping ratio of the chestnut cupule biochar to sodium dihydrogen phosphate in step (2) is 160:1 (w:w), and the solid-liquid ratio of the above mixture to deionized water is 1 g:15 mL.

[0018] Preferably, the hydrothermal temperature in step (2) is 80 °C, the hydrothermal time is 2 h; the drying temperature is 60 °C, and the drying time is 24 h.

[0019] According to the third aspect of the present invention, there is provided an application of the phosphorus-modified chestnut cupule biochar obtained by the above preparation method in the treatment of cadmium-containing wastewater.

[0020] In one embodiment, the phosphorus-modified chestnut cupule biochar is mixed with the cadmium-containing water body and then left standing at room temperature for 2160 min. After the reaction is completed, the solution after removing cadmium is obtained by filtration.

[0021] Preferably, the initial concentration of cadmium in the cadmium-containing water body is 50-300 mg / L, and the dosage of the phosphorus-modified chestnut cupule biochar is 5 g / L.

[0022] Compared with the prior art, the beneficial effects of the present invention mainly include but are not limited to the following aspects:

[0023] (1) The phosphorus-modified chestnut cupule biochar prepared by the present invention uses chestnut cupule waste as a raw material, which is currently only used for preparing fertilizers and fuels. By using this method to synthesize phosphorus-modified chestnut cupule biochar for the treatment of cadmium-containing wastewater, it can not only realize the resource utilization of chestnut cupule waste, but also achieve the efficient removal of cadmium in the water body, achieving the dual purpose of treating pollution with waste.

[0024] (2) The phosphorus-modified chestnut cupule biochar prepared by the present invention has a stable structure, a specific surface area of 179 m 2 / g, a micropore volume of 0.103 cm 3 / g, an average pore diameter of 8.61 nm, and has abundant oxygen-containing functional groups and phosphorus-containing functional groups, which can make the removal rate of cadmium with a concentration of 200 mg / L in the water body reach more than 90%. It is an environmental functional restoration material suitable for the treatment of cadmium-containing wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly understand the embodiments of the present invention or the technical solutions in the prior art, the following will further describe in detail the drawings required to be used in the description of the embodiments or the prior art. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, where:

[0026] Figure 1 It is the scanning electron microscope image of the phosphorus-modified chestnut cupule biochar in Example 2 of the present invention;

[0027] Figure 2 It is the Fourier infrared spectrum of the phosphorus-modified chestnut cupule biochar in Example 2 of the present invention;

[0028] Figure 3 It is the X-ray diffraction pattern of the phosphorus-modified chestnut cupule biochar in Example 2 of the present invention;

[0029] Figure 4 It is the nitrogen adsorption-desorption spectrum of the phosphorus-modified chestnut cupule biochar in Example 2 of the present invention;

[0030] Figure 5 It is the removal rate of cadmium in water by the phosphorus-modified chestnut cupule biochar in Example 3 of the present invention at different reaction times;

[0031] Figure 6 It is the removal rate of cadmium with different concentrations in water by the phosphorus-modified chestnut cupule biochar in Example 4 of the present invention;

[0032] Figure 7 It is the removal rate of cadmium in water by the phosphorus-modified chestnut cupule biochar in Example 5 of the present invention under different pH conditions;

[0033] Figure 8 It is the removal rate of cadmium in water by the phosphorus-modified chestnut cupule biochar in Example 6 of the present invention at different reaction temperatures. Detailed implementation manners

[0034] The present invention will be described in detail below through specific implementation cases. The specific embodiments described are only used to explain the present invention, and those skilled in the art can refer to them and modify the process parameters when dealing with different application scenarios. It should be particularly emphasized here that any improvement of the parameters or modification of the process of the present invention will be regarded as a derivative product of the present invention and will not deviate from the scope covered by this patent. The specific implementation cases are as follows:

[0035] Example 1

[0036] This example is for the preparation of the phosphorus-modified chestnut cupule biochar.

[0037] Specifically, it includes the following steps:

[0038] Weigh a certain amount of chestnut husk cups, wash, dry and grind them, sieve them through a 20-mesh sieve to obtain chestnut husk cup particles, place them in a crucible, pyrolyze them in a muffle furnace at 445 °C for 6 h to obtain chestnut husk cup biochar, and take it out and cool it to room temperature. Then, hydrothermally react the chestnut husk cup biochar with sodium dihydrogen phosphate powder at a doping ratio of 160:1 (w:w) for 2 h to obtain phosphorus-modified chestnut husk cup biochar. After cooling, wash it with a mixed solution of ethanol and deionized water (v:v = 1:2), and place it in a vacuum drying oven to dry at 60 °C for 24 h.

[0039] Example 2

[0040] In this example, the phosphorus-modified chestnut husk cup biochar prepared in Example 1 was characterized.

[0041] Take an appropriate amount of phosphorus-modified chestnut husk cup biochar for scanning electron microscopy analysis to observe its morphology. The results are as Figure 1 shown. The surface of the phosphorus-modified chestnut husk cup biochar is rough and the pores are damaged. This is because during the hydrothermal reaction process, the surface of the biochar is affected by the activation of orthophosphate to form continuous carbon nanosheets.

[0042] Take an appropriate amount of phosphorus-modified chestnut husk cup biochar for Fourier transform infrared spectroscopy test to qualitatively analyze its functional groups. The results are as Figure 2 shown. The phosphorus-modified chestnut husk cup biochar shows peaks at around 2500 - 3400 cm -1 , 1575 cm -1 and 1450 cm -1 , which are attributed to the stretching vibrations of -OH, -COOH and C=O; peaks at 1100 cm -1 and 875 cm -1 appear at -PO4 3 - and -H2PO4 - respectively, indicating that the surface of the phosphorus-modified chestnut husk cup biochar contains rich phosphorus-containing functional groups and oxygen-containing functional groups.

[0043] Take an appropriate amount of phosphorus-modified chestnut husk cup biochar for X-ray diffraction to analyze its crystal structure. The results are as Figure 3 shown. The phosphorus-modified chestnut husk cup biochar shows characteristic diffraction peaks of P2O5 (2θ = 22.9°, 29.3°), NaH2PO4 (2θ = 26.5°, 43.1°, 47.3°, 48.5°), Na3PO4 (2θ = 20.9°, 39.3°) and P (2θ = 27.7°, 35.8°), indicating that P has been successfully doped onto the chestnut husk cup biochar.

[0044] Take an appropriate amount of phosphorus-modified chestnut husk cup biochar for nitrogen adsorption-desorption test to analyze its pore characteristics. The results are as Figure 4As shown. According to the IUPAC classification, the adsorption-desorption isotherm is a type-IV curve with an H4-type hysteresis loop, having an inflection point in the low-pressure region and non-coincident adsorption and desorption in the high-pressure region. Due to the micropore filling effect, the adsorption content increases sharply within a relatively low range, but shows multilayer adsorption and capillary condensation at higher pressures, indicating that there are a small number of micropores, a large number of mesopores, and macropores in the phosphorus-modified chestnut shell biochar, with an irregular structure and mostly slit-shaped pores on the surface.

[0045] Example 3

[0046] This example explores the removal rate of cadmium in water by phosphorus-modified chestnut shell biochar at different reaction times.

[0047] In this example, the cadmium-containing wastewater was prepared with cadmium chloride, and the initial concentration was 200 mg / L. Weighed 0.05 g of phosphorus-modified chestnut shell biochar and placed it in a 50 mL conical flask. Starting from the addition of 10 mL of the above cadmium solution, timing was started. Under room temperature conditions, when the reaction proceeded for 5, 10, 15, 30, 60, 120, 240, 480, 720, 1440, 2160 min, the supernatant was collected, filtered, and the cadmium concentration in the filtrate was measured using a flame atomic absorption spectrophotometer.

[0048] Result analysis:

[0049] Figure 5 is the removal rate of cadmium in water by phosphorus-modified chestnut shell biochar at different reaction times. The removal rate of cadmium by phosphorus-modified chestnut shell biochar increased rapidly within the first 10 min, reaching a maximum removal rate of 16.9 mg / L / min; subsequently, the removal rate of cadmium increased slowly and basically reached equilibrium at 1440 min, with a removal rate of 76.8%.

[0050] Example 4

[0051] This example explores the removal rate of different concentrations of cadmium in water by phosphorus-modified chestnut shell biochar.

[0052] In this example, the cadmium-containing wastewater was prepared with cadmium chloride, and the initial concentrations were 50, 100, 150, 200, 250, 300 mg / L respectively. Weighed 0.05 g of phosphorus-modified chestnut shell biochar and placed it in a 50 mL conical flask. Starting from the addition of 10 mL of the above cadmium solutions with different concentrations, timing was started. Under room temperature conditions, when the reaction proceeded for 2160 min, the supernatant was collected, filtered, and the cadmium concentration in the filtrate was measured using a flame atomic absorption spectrophotometer.

[0053] Result analysis:

[0054] Figure 6The removal rate of phosphorus-modified chestnut shell biochar for cadmium at different concentrations in water. When the initial concentration of cadmium in water is 100 mg / L, the phosphorus-modified chestnut shell biochar has the best removal effect on cadmium in water, and the removal rate can reach 92.2%.

[0055] Example 5

[0056] This example explores the removal rate of phosphorus-modified chestnut shell biochar for cadmium in water under different initial pH conditions.

[0057] In this example, the cadmium-containing wastewater is prepared with cadmium chloride, and the initial concentration is 200 mg / L. 1M hydrochloric acid or 1M ammonia water is used to adjust the initial pH of the solution to 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0. Weigh 0.05 g of phosphorus-modified chestnut shell biochar and place it in a 50 mL conical flask. Start timing from the addition of 10 mL of the above cadmium solutions with different pH values. Under room temperature conditions, after the reaction proceeds for 2160 min, collect the supernatant, filter it, and use a flame atomic absorption spectrophotometer to measure the cadmium concentration in the filtrate.

[0058] Result analysis:

[0059] Figure 7 The removal rate of phosphorus-modified chestnut shell biochar for cadmium in water under different initial pH conditions. When the initial pH of the cadmium solution is 10, the phosphorus-modified chestnut shell biochar has the best removal effect on cadmium in water, and the removal rate can reach 95.2%.

[0060] Example 6

[0061] This example explores the removal rate of phosphorus-modified chestnut shell biochar for cadmium in water at different reaction temperatures.

[0062] In this example, the cadmium-containing wastewater is prepared with cadmium chloride, and the initial concentration is 200 mg / L. Weigh 0.05 g of phosphorus-modified chestnut shell biochar and place it in a 50 mL conical flask. Start timing from the addition of 10 mL of the above cadmium solution. Under the conditions of 20, 30, and 40 °C respectively, after the reaction proceeds for 2160 min, collect the supernatant, filter it, and use a flame atomic absorption spectrophotometer to measure the cadmium concentration in the filtrate.

[0063] Result analysis:

[0064] Figure 8 The removal rate of phosphorus-modified chestnut shell biochar for cadmium in water at different reaction temperatures. When the reaction temperature is 40 °C, the phosphorus-modified chestnut shell biochar has the best removal effect on cadmium in water, and the removal rate can reach 89.8%.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. Application of phosphorus-modified chestnut cupule biochar in treating cadmium-containing wastewater, characterized in that, The phosphorus-modified chestnut cupule biochar is prepared from chestnut cupule waste, and the preparation method comprises the following steps: (1) Wash, dry and grind chestnut cupules, and obtain cupule particles after passing through a 20-mesh sieve. Place them in a muffle furnace and carry out high-temperature pyrolysis treatment under oxygen-limited conditions. The pyrolysis temperature is 445 °C to obtain chestnut cupule biochar; (2) Mix the chestnut cupule biochar obtained in step (1) with sodium dihydrogen phosphate powder evenly according to a doping ratio of 160:1 (w:w), add deionized water, place it in a reaction kettle and carry out hydrothermal reaction at 80 °C. Then wash the hydrothermal product and dry it in a vacuum drying oven to obtain phosphorus-modified chestnut cupule biochar; The phosphorus-modified chestnut cupule biochar described above has: a specific surface area of 179 m 2 / g, a micropore volume of 0.103 cm 3 / g, an average pore diameter of 8.61 nm, and contains abundant oxygen-containing functional groups and phosphorus-containing functional groups.

2. The application according to claim 1, characterized in that The chestnut cupules described in step (1) are agricultural and forestry waste, collected in Yixing City, Jiangsu Province.

3. The application according to claim 1, characterized in that The high-temperature pyrolysis conditions described in step (1) are heating to 445 °C at a heating rate of 5 °C / min and continuously pyrolyzing for 6 h.

4. The application according to claim 1, characterized in that The solid-liquid ratio of the mixture of chestnut cupule biochar and sodium dihydrogen phosphate to deionized water in step (2) is 1 g:15 mL.

5. The application according to claim 1, characterized in that, The hydrothermal time in step (2) is 2 h; the drying temperature is 60 °C and the drying time is 24 h.

6. The application according to claim 1, wherein It includes the following steps: Mix the phosphorus-modified chestnut cupule biochar with cadmium-containing water body evenly, stand still at room temperature for 2160 min, and filter after the reaction ends to obtain the solution after removing cadmium.

7. The application according to claim 6, characterized in that The initial concentration of cadmium in the water body is 50-300 mg / L, and the dosage of the phosphorus-modified chestnut cupule biochar is 5 g / L.

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