Kudzuvine root waste charcoal type adsorbent applied to dye wastewater

Abstract

The invention relates to the technical field of environmental protection and pollution abatement, and discloses a preparation method of a radix puerariae waste charcoal type adsorbent applied to dye wastewater, which comprises the following steps: washing radix puerariae waste residue with pure water to remove ash and impurities on the surface, drying at 70-90 DEG C for 10-15 hours, and crushing until the particle size is less than 5mm for later use; the radix puerariae waste residue powder is placed in a muffle furnace to be subjected to oxygen-limited pyrolysis carbonization, the pyrolysis temperature is set to be one or more temperature points of 450-850 DEG C, the heating rate is 5-15 DEG C / min, constant-temperature carbonization is conducted for 1-3 h, and cooling is conducted to the room temperature. The radix puerariae waste is used as agricultural processing waste, so that the cost is extremely low, and a cheap and easily available raw material basis is provided for production of the adsorbent. And the waste is converted into an adsorbent with high added value, so that the treatment cost of the waste is reduced, and additional economic value is created. Meanwhile, the preparation process of the adsorbent is simple, complex equipment and expensive modifiers are not needed, and the production cost is further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection and pollution control, and in particular to a kudzu root waste biochar-type adsorbent applied to dye wastewater. Background Art

[0002] In the current field of environmental protection, especially in the treatment of industrial wastewater, one of the key challenges is the effective purification of dye wastewater. Dye wastewater, containing large amounts of synthetic organic matter and chromogenic groups, is characterized by complex composition, poor biodegradability, high chroma, and high toxicity, posing a serious threat to the environment.

[0003] Existing dye wastewater treatment technologies primarily include physical and chemical methods and biological treatment. Physical and chemical methods such as adsorption, membrane separation, and chemical oxidation offer high treatment efficiency and stable results, but they suffer from high operating costs and the potential for secondary pollution. For example, activated carbon adsorbents are expensive and require complex regeneration after saturation. While biological treatment methods offer lower operating costs, they have stringent requirements for water quality and environmental conditions, require long treatment times, and have low removal rates, making deep treatment difficult to achieve.

[0004] Adsorption has attracted widespread attention in dye wastewater treatment due to its low cost, ease of operation, low energy consumption, and high efficiency. The properties of the adsorbent directly influence adsorption effectiveness. Currently, commonly used adsorbents include activated carbon, zeolite, and clay, but these materials suffer from limited adsorption capacity, high cost, and difficulty in regeneration. Biochar, as a new adsorption material, has become a research hotspot due to its wide availability, low cost, environmental friendliness, rich pore structure, and large specific surface area.

[0005] However, in practical applications, the preparation and modification process of biochar often requires a lot of energy consumption, especially under high-temperature modification conditions, which may lead to increased production costs and impose additional burden on the environment.

[0006] With the promotion of biomass waste resource utilization and low-carbon environmental protection technologies, the development of high-performance, low-cost adsorbents from agricultural waste has become a hot topic of research. For example, existing research has used agricultural waste such as corn stalks and rice husks to prepare biochar adsorbents for dye wastewater treatment. However, there is still room for improvement in terms of adsorption efficiency, cost control, and environmental friendliness.

[0007] In view of the above-mentioned deficiencies in the prior art, those skilled in the art have proposed a kudzu root waste biochar-based adsorbent for dye wastewater to solve the problems raised in the above-mentioned background technology. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the present invention provides a kudzu root waste biochar-type adsorbent for dye wastewater, which solves the problems raised in the above background technology.

[0009] To achieve the above objectives, the present invention is implemented through the following technical scheme: a kudzu waste biochar-type adsorbent applied to dye wastewater, wherein the adsorbent is prepared from kudzu waste by an oxygen-limited pyrolysis method, and in simulated dye wastewater with an initial concentration of 100-175 mg / L of malachite green, 80-150 mg / L of methylene blue and 80-150 mg / L of methyl orange, the adsorbent dosage is 0.3-0.5 g / L, the pH value is 6-8, the adsorption time is 120-180 min, and the temperature is 20-30°C. Under the conditions, the adsorption amount of malachite green can reach 250-293.21 mg / g, the adsorption amount of methylene blue reaches 200-221.83 mg / g, and the adsorption amount of methyl orange reaches 200-239.92 mg / g.

[0010] A method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater comprises the following steps:

[0011] Wash the kudzu root waste residue with pure water to remove ash and impurities on the surface, dry it at 70-90°C for 10-15h, crush it to a particle size of less than 5mm, and set aside;

[0012] The kudzu root waste residue powder is placed in a muffle furnace for oxygen-limited pyrolysis carbonization, the pyrolysis temperature is set to one or more temperature points between 450-850°C, the heating rate is 5-15°C / min, the constant temperature carbonization is performed for 1-3 hours, and the mixture is cooled to room temperature.

[0013] Preferably, after the oxygen-limited pyrolysis carbonization is completed, the pyrolysis product is washed with a 0.8-1.2 mol / L HCl solution for 10-30 min.

[0014] Preferably, the method further comprises discarding the supernatant after washing, collecting the precipitate, and then washing with deionized water 2-4 times until the pH of the supernatant is 6.5-7.5, collecting the precipitate, drying it in an oven at 60-80°C for 6-12 hours, cooling it, and sieving it to obtain the kudzu waste biochar-type adsorbent with a particle size of 0.1-0.3 mm.

[0015] Preferably, the kudzu root waste residue is a mixture of one or more of waste kudzu root fibers, kudzu root peels, etc. generated during the kudzu root processing, and its moisture content does not exceed 10%.

[0016] Preferably, after obtaining the kudzu root waste biochar-type adsorbent, the method further comprises the steps of sealing and packaging the biochar and storing the biochar in a dry, cool place with a temperature of 5-25° C. and a humidity below 60%.

[0017] Preferably, the oxygen-limited pyrolysis method is to introduce an inert gas such as nitrogen or argon into a muffle furnace at a gas flow rate of 10-50 mL / min, or to perform pyrolysis carbonization under vacuum conditions to ensure an oxygen-limited environment during the pyrolysis process, wherein when the inert gas is introduced, the oxygen content during the pyrolysis carbonization process is less than 5%, and when under vacuum conditions, the vacuum degree is 0.01-0.05 MPa.

[0018] Preferably, before placing the kudzu root waste residue powder in a muffle furnace for oxygen-limited pyrolysis and carbonization, the method further comprises drying the kudzu root waste residue powder until the moisture content is less than 5%, with a drying temperature of 40-60° C. and a drying time of 8-12 hours.

[0019] Preferably, during the oxygen-limited pyrolysis carbonization process, the pyrolysis temperature is 850°C, the heating rate is 10°C / min, and the constant temperature carbonization is performed for 2 hours. The prepared kudzu waste biochar-type adsorbent has the best adsorption performance for MG, MB and MO.

[0020] The present invention provides a kudzu root waste biochar adsorbent for dye wastewater treatment. It has the following beneficial effects:

[0021] 1. The present invention utilizes kudzu root waste as agricultural processing waste, providing an extremely low-cost, readily available raw material base for adsorbent production. Converting it into a high-value-added adsorbent not only reduces waste disposal costs but also creates additional economic value. Furthermore, the adsorbent preparation process is simple, eliminating the need for complex equipment and expensive modifiers, further reducing production costs.

[0022] 2. By optimizing the preparation process, the present invention effectively regulates its internal pore structure and specific surface area, enabling efficient adsorption of a variety of organic dye molecules in dye wastewater, including cationic dyes such as malachite green and methylene blue, and anionic dyes such as methyl orange. This allows for high dye removal rates with a reduced adsorbent dosage in actual dye wastewater treatment, effectively reducing wastewater treatment costs, improving treatment efficiency, and ensuring that wastewater discharge meets environmental standards.

[0023] 3. The present invention uses kudzu root waste as raw material, realizes the resource recycling of biomass, avoids the environmental pollution that may be caused by the incineration or landfill of waste, reduces greenhouse gas emissions, and conforms to the concept of sustainable development. Secondly, the preparation process adopts the oxygen-limited pyrolysis method, which does not require the addition of toxic and harmful chemicals, thus avoiding the generation of secondary pollution. In addition, the used biochar adsorbent can be safely disposed of or used as a soil conditioner, further promoting the improvement of the ecological environment and reflecting the green and environmentally friendly characteristics of the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a flow chart of the steps for preparing biochar from kudzu root waste residue of the present invention;

[0025] Figure 2 This is a flow chart for preparing biochar from kudzu root waste residue of the present invention;

[0026] Figure 3 A schematic diagram of the kinetic model parameters for removing MG, MB and MO according to an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of the adsorption isotherm fitting of Examples MB (a, b, c and d), MG (e, f, g and h) and MO (i, j, k and l) of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Please see the attached Figure 1 -Attached Figure 4 The present invention provides a method for preparing a kudzu root waste biochar adsorbent for dye wastewater, and the specific steps are as follows:

[0030] Pretreatment of kudzu residue: Take an appropriate amount of kudzu residue (primarily composed of discarded kudzu fiber and kudzu bark, with a moisture content of no more than 10%) and thoroughly wash it in pure water to remove surface ash and impurities. Subsequently, dry the washed kudzu residue in an 80°C drying oven for 12 hours, ensuring even and thorough drying. After drying, crush the kudzu residue to a particle size of less than 5 mm for later use.

[0031] Specifically, the kudzu root waste (primarily consisting of discarded kudzu root fiber and kudzu root bark, with a moisture content controlled to no more than 10%) is first washed thoroughly in pure water. This step aims to utilize the flow of water to wash away dust, dirt, and other soluble impurities adhering to the surface of the kudzu root waste, thereby improving the purity of the raw material and laying a good foundation for subsequent processing steps.

[0032] After the washing process, the kudzu root waste is placed in a drying oven and dried at 80°C for 12 hours. The purpose of this drying process is to remove any residual moisture from the kudzu root waste, ensuring it reaches the desired dryness. Uniform and thorough drying helps prevent adverse reactions caused by moisture during the subsequent pyrolysis process, such as side reactions between water vapor and pyrolysis products. This also helps improve the quality and properties of the final biochar.

[0033] Finally, the dried kudzu residue is crushed to a particle size of less than 5 mm. This crushing process adjusts the particle size of the kudzu residue to meet the requirements of the subsequent pyrolysis and carbonization process. A moderate particle size helps ensure uniform heat transfer and material conversion during the pyrolysis process, thereby improving the biochar yield and adsorption performance, ensuring the effective practical application of the prepared biochar-based adsorbent.

[0034] Pyrolysis and carbonization: The pretreated kudzu root waste powder was placed in a muffle furnace, set to a pyrolysis temperature of 850°C, and heated at a rate of 10°C / min. During the pyrolysis process, nitrogen was introduced into the muffle furnace as an inert gas at a flow rate of 30 mL / min to ensure an oxygen-limited environment (less than 5%). After reaching the set temperature, carbonization was continued at a constant temperature for 2 hours, then the muffle furnace was closed and allowed to cool naturally to room temperature.

[0035] Specifically, the pretreated kudzu root waste residue powder is placed in a muffle furnace. A muffle furnace is a device that can provide a high-temperature environment and is suitable for pyrolysis and carbonization processes. A specific pyrolysis temperature is set and heated at a controlled heating rate to ensure that the waste residue is evenly heated, thereby achieving a stable pyrolysis reaction. During the pyrolysis process, nitrogen is introduced as an inert gas to remove oxygen from the air and create an oxygen-limited environment. This oxygen-limited environment can prevent the waste residue from undergoing complete oxidation and combustion at high temperatures, but instead promotes a pyrolysis reaction to produce biochar.

[0036] At the same time, the flow rate of nitrogen is controlled to maintain the stability of the pyrolysis environment. After reaching the preset pyrolysis temperature, the temperature is maintained constant for a period of time. This step is called constant temperature carbonization. The constant temperature carbonization process is to ensure that the kudzu root waste residue powder undergoes sufficient pyrolysis reaction under this high temperature condition to produce a biochar material with a rich pore structure and good adsorption properties. After the constant temperature carbonization is completed, the muffle furnace is turned off and allowed to cool naturally to room temperature. Natural cooling helps to avoid damage to the biochar structure caused by a sudden drop in temperature, while stabilizing the properties of the biochar, making it easier to handle and use later.

[0037] Acid washing treatment: The product after pyrolysis carbonization is taken out, placed in a beaker, added with 1 mol / L HCl solution, and soaked and washed at room temperature for 15 minutes to remove the ash produced during the pyrolysis process and prevent it from clogging the pore structure of the biochar, thereby improving the adsorption performance.

[0038] Specifically, after pyrolysis and carbonization, the resulting product will contain some ash impurities, primarily derived from the mineral components of the kudzu vine waste. The pyrolysis product is removed and placed in a beaker, where it is then soaked and cleaned with a dilute hydrochloric acid solution. Dilute hydrochloric acid reacts chemically with the ash impurities, producing water-soluble chlorides, effectively removing these impurities. The acid washing process is carried out at room temperature, avoiding potential damage to the biochar structure caused by high temperatures.

[0039] Washing and Drying: Discard the acid-washing supernatant and collect the precipitate. Rinse the precipitate several times with deionized water (three times) until the pH of the supernatant reaches approximately 7. Dry the washed precipitate in a 60°C oven for 8 hours. After drying, remove and cool to room temperature.

[0040] Specifically, after the pickling process is completed, the pickling liquid (supernatant) needs to be poured out, leaving only the precipitate, which is the biochar after preliminary purification. Next, the precipitate is repeatedly washed with deionized water. Multiple washings can more thoroughly remove the residual acid and impurities dissolved in the acid. The number and effect of the washing are usually judged by the pH value of the supernatant after pickling. When the pH value of the supernatant is close to neutral, it indicates that the pickling residue has been basically removed.

[0041] The washed precipitate is placed in an oven for drying. The purpose of drying is to remove moisture from the biochar, drying it to a dry state for subsequent use and storage. The drying temperature and time must be carefully considered to ensure thorough drying without damaging the biochar's structure and adsorption properties. After drying, the dried biochar is removed and allowed to cool naturally to room temperature. This stabilizes its physical properties for subsequent processing or application.

[0042] Sieving: The cooled product is sieved to obtain a kudzu waste biochar-type adsorbent with a particle size of 0.1-0.3 mm.

[0043] Storage: The prepared adsorbent should be sealed and stored in a dry, cool place with a temperature of 20°C and a humidity of 50% to maintain its stable performance.

[0044] The kudzu root waste biochar type adsorbent prepared by the above steps shows excellent adsorption performance in simulated dye wastewater. In the simulated dye wastewater with an initial concentration of 125 mg / L malachite green, 100 mg / L methylene blue and 100 mg / L methyl orange, the adsorbent dosage is 0.4 g / L, the pH value is 7, the adsorption time is 150 min, and the temperature is 25 ° C. Under the conditions, the adsorption amount of malachite green can reach 293.21 mg / g, the adsorption amount of methylene blue can reach 221.83 mg / g, and the adsorption amount of methyl orange can reach 239.92 mg / g. This result fully proves that the kudzu root waste biochar type adsorbent prepared by the present invention has efficient dye adsorption capacity, can effectively remove organic dye molecules in dye wastewater, and the preparation process is simple, low cost, environmentally friendly, and has broad application prospects.

[0045] To compare the dye adsorption capacity of kudzu waste biochar, 0.05 g of kudzu waste biochar, pyrolyzed at 450, 550, 650, 750, and 850°C, was added to 100 mL of MG (100 mg / L), 100 mL of MB (100 mg / L), and 100 mL of MO (100 mg / L). The mixture was placed in a 250 mL conical flask and shaken at 160 rpm for 2.5 hours at 25°C. The samples were then collected and the residual dye concentrations were measured using a UV-visible spectrophotometer at specific wavelengths (MG: 618 nm, MB: 665 nm, MO: 464 nm). Among all the samples, RPB850 exhibited the highest adsorption capacity for MG, MB, and MO, and was therefore selected for further investigation. The effects of different single factors on the dye adsorption on biochar were studied, such as biochar dosage (0.02-0.06 g), pH (3-11), and initial solution concentration (50-175 mg / L), to confirm its optimal adsorption performance.

[0046] For the adsorption kinetics experiment, 0.04 g RPBP850 was added to 100 mL of MG solution (125 mg / L), MB solution (100 mg / L), and MO (100 mL 100 mg / L) at pH 7 and shaken at 25 °C for 5, 15, 30, 45, 60, 90, 120, 150, 180, and 210 min. For the adsorption isotherm experiments, 0.04 g RPBP850 was added into 100 mL of MG (100, 125, 200, 275, 350, 500, 650, and 800 mg / L), MB (75, 100, 150, 200, 250, 300, 350, and 400 mg / L), and MB (75, 100, 150, 200, 300, 400, 500, and 600 mg / L) solutions at different concentrations, and the adsorption process was studied by oscillation at different temperatures (288 K, 298 K, 308 K, and 318 K) for 2.5 h.

[0047] Biochar preparation process design Figure 2 As shown, the retrieved kudzu root waste residue is first washed with pure water to remove ash and impurities on the surface, dried at 80° C., crushed, and set aside.

[0048] The kudzu root waste residue powder was placed in a muffle furnace for oxygen-limited pyrolysis carbonization. Five different pyrolysis temperatures (450°C, 550°C, 650°C, 750°C, and 850°C) were set for carbonization. The carbonization temperature was kept constant for 2 hours and then cooled. It was then washed with a 1 mol / L HCl solution to reduce the blockage of the pores by ash. The supernatant was discarded, the precipitate was collected, and then washed with deionized water until the pH of the supernatant was about 7. The precipitate was then collected, dried in an oven, cooled, and sieved for later use. The biochars prepared at different pyrolysis temperatures were labeled RPB450, RPB550, RPB650, RPB750, and RPB850, respectively.

[0049] The adsorption capacity and removal rate of biochar are calculated according to the following equation. The formula is as follows:

[0050]

[0051] Where: qe is the amount of dye adsorbed by biochar at equilibrium, mg / g; C0 is the concentration of the initial dye solution, mg / L; C e is the concentration of the dye solution at adsorption equilibrium, mg / L; V is the volume of the dye solution, mL; m is the mass of added biochar, g; E is the removal efficiency, %.

[0052] The kinetic properties of biochar on dye solution were studied in depth using pseudo-first-order adsorption kinetics, pseudo-second-order adsorption kinetics, intraparticle diffusion, and the Elovich model. The formula is as follows:

[0053] Pseudo-first-order adsorption kinetics: qt =q e ×[1–exp(–k1t)]

[0054] Pseudo-secondary adsorption kinetics:

[0055] Intraparticle diffusion model: q i =k s t 0.5 +A

[0056] Elovich model: q ι =k4×ln t +B

[0057] Where: q r ,q e are the adsorption capacity at time t and adsorption equilibrium, mg / g; k l , k2, k3, k4 are the rate constants corresponding to the four kinetic models, min l , [g / (mg·min)], [mg / (g·min0.5)], [mg / (g·min)]; A and B represent the boundary layer constant of the Weber-Morris model and the Elovich model constant, respectively.

[0058] Adsorption isotherms are used to illustrate the interaction mechanism between the adsorbent and the adsorbate in the solution. The Langmuir, Freundlich, and Temkin models shown in the following formulas are fitted to the adsorption experimental data at different initial dye concentrations and reaction temperatures. The dimensionless parameter R is used. L Equation (10) evaluates the difficulty of the adsorption reaction. When RL = 0, the adsorption is irreversible; when 0 < RL < 1, the adsorption proceeds smoothly; when RL = 1, the adsorption has a linear relationship; and when RL > 1, it indicates that the adsorbent has difficulty adsorbing the adsorbate. The formula is as follows:

[0059] Langmuir model:

[0060] Freundlich model:

[0061]

[0062] Temkin model: q e =ClnK T C e

[0063] Where: q s ,q mRespectively represent the equilibrium adsorption capacity and theoretical maximum adsorption capacity of methyl orange, mg / g; C s is the mass concentration of methyl orange at adsorption equilibrium, K L represents the adsorption equilibrium constant of the Langmuir model; K F , n represents the correlation constant of the Freundlich model; Kτ represents the equilibrium binding constant of the Temkin model; C represents the coefficient related to the adsorption heat.

[0064] The adsorption process of MG, MB and MO on RPB was described by pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich kinetic models. The fitting results are shown in Figure 3 and Table 1. It can be seen that for MG, MB and MO, the Elovich model (R 2 =0.9970, R 2 =0.9960 and R 2 =0.9949) is generally higher than the regression coefficient (R2) of the pseudo-first-order model (R 2 =0.8976, R 2 =0.9425 and R 2 =0.9193), quasi-second-order model (R 2 =0.9568, R 2 =0.9892 and R 2 = 0.9700) and intraparticle diffusion model (R 2 =0.6792, R 2 =0.8017 and R 2 =0.8744), indicating that the adsorption process is more consistent with the Elovich model. Hoslett et al. also found that the adsorption process follows a pseudo-second-order kinetic model. A study on the removal of MB from water using biochar prepared by pyrolysis of mixed municipal solid waste. Its coefficient of determination R 2 Higher than the pseudo-first-order and intraparticle diffusion models. According to the Elovich model, chemical adsorption is the key rate-limiting step, but liquid film diffusion, surface adsorption, and particle diffusion may also have an impact on the adsorption process.

[0065]

[0066] Table 1 (Kinetic model parameters for removing MG, MB and MO)

[0067] The intra-particle diffusion model was used to fit the adsorption data of MG, MB and MO in stages to further explore the rate-limiting step of RPB adsorption of MG, MB and MO. As shown in Table 2, the adsorption process of MG, MB and MO by RPB can be divided into three stages, namely the external diffusion stage (stage I, lasting 0-45min), the internal diffusion stage (stage II, lasting 45-120min) and the adsorption reaction stage (stage III, lasting 120-210min) (Fig. 2). Among them, in stage I, the content of MG, MB and MO in the reaction system is high, and the adsorption points on RPB are abundant. MG, MB and MO diffuse rapidly to the RPB surface through the liquid boundary film. Therefore, the adsorption time in this stage is short and the adsorption rate is fast (k 31 ,MG=12.29,k 31 ,MB=19.60 and k 31 ,MO=19.42). In stage II, MG, MB and MO diffuse into the internal pores of RPB under the driving force of external mass transfer. Compared with stage I, the adsorption rate begins to slow down, k 32 The k 32 ,MG=6.609), 2.21 times (k 32 ,MB=6.105) and 1.92 times (k 32 MO = 9.402). With further prolonged adsorption time, the rate of decrease in the concentrations of MG, MB, and MO in the solution gradually flattened (Fig. 2), indicating that the surface adsorption and internal attachment on the RPB gradually saturated. However, the A values ​​for all three adsorption stages were greater than 0, indicating that the fitted curves did not pass through the origin of the coordinate axis, confirming that intraparticle diffusion is not the sole rate-limiting factor in the removal of MG, MB, and MO from water by RPB. The adsorption of MG, MB, and MO by RPB is also influenced by other processes such as liquid film diffusion and adsorption reactions.

[0068]

[0069] Table 2 (Phase-specific fitting parameters for the intra-particle diffusion model of MG, MB, and MO)

[0070] The adsorption isotherm experimental data of three dyes (malachite green-MG, methylene blue-MB, and methyl orange-MO) on kudzu waste biochar-based adsorbent were fitted using three different adsorption models (Langmuir-Freundlich and Temkin), as shown in Table 3 below:

[0071]

[0072]

[0073]

[0074] Table 3

[0075] The energy conservation and emission reduction benefit analysis of this project is as follows.

[0076] Coconut shell activated carbon, prepared by impregnation and calcination, has no optimal pH range, the best adsorption capacity is 112.7 mg·g-1, and the cost is 100 yuan / kg;

[0077] Straw biochar, prepared by oxygen-limited slow pyrolysis, has an optimal adsorption capacity of 27.82 mg·g-1 at pH 7-8, and a cost of 34 yuan / kg.

[0078] Ginkgo leaves, calcined in a muffle furnace, have an optimal adsorption capacity of 57.14 mg·g-1 at pH = 2, and the cost is 54 yuan / kg.

[0079] The details are shown in Table 4 below:

[0080]

[0081]

[0082] Table 4

[0083] This experiment used biochar from kudzu root waste, produced by oxygen-limited pyrolysis, which is not pH-restricted. At initial MG, MB, and MO concentrations of 125, 100, and 100 mg / L, respectively, adsorption capacities reached 293.21, 221.83, and 239.92 mg / g, respectively, at a cost of 36 yuan per kg.

[0084] In summary: The present invention uses kudzu root waste as agricultural processing waste, which has extremely low cost and provides a cheap and easily available raw material basis for the production of adsorbents. Converting it into a high-value-added adsorbent not only reduces the waste treatment cost, but also creates additional economic value. At the same time, the adsorbent preparation process is simple, does not require complex equipment and expensive modifiers, and further reduces production costs. By optimizing the preparation process, its internal pore structure and specific surface area are effectively regulated, so that it can efficiently adsorb a variety of organic dye molecules in dye wastewater, including cationic dyes malachite green, methylene blue and anionic dyes methyl orange. In this actual dye wastewater treatment process, a higher dye removal rate can be achieved with a smaller amount of adsorbent, effectively reducing wastewater treatment costs, improving treatment efficiency, and ensuring that wastewater discharge meets environmental protection standards.

[0085] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A kudzu root waste biochar adsorbent for dye wastewater, characterized in that: The adsorbent is prepared from kudzu root waste by an oxygen-limited pyrolysis method. In simulated dye wastewater with initial concentrations of 100-175 mg / L of malachite green, 80-150 mg / L of methylene blue, and 80-150 mg / L of methyl orange, the adsorbent dosage is 0.3-0.5 g / L, the pH value is 6-8, the adsorption time is 120-180 minutes, and the temperature is 20-30°C. Under the following conditions, the adsorption amount of malachite green can reach 250-293.21 mg / g, the adsorption amount of methylene blue can reach 200-221.83 mg / g, and the adsorption amount of methyl orange can reach 200-239.92 mg / g.

2. A method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater, according to claim 1, wherein the kudzu root waste biochar-based adsorbent is characterized in that: The following steps are involved: Wash the kudzu root waste residue with pure water to remove ash and impurities on the surface, dry it at 70-90°C for 10-15h, crush it to a particle size of less than 5mm, and set aside; The kudzu root waste residue powder is placed in a muffle furnace for oxygen-limited pyrolysis carbonization, the pyrolysis temperature is set to one or more temperature points between 450-850°C, the heating rate is 5-15°C / min, the constant temperature carbonization is performed for 1-3 hours, and the mixture is cooled to room temperature.

3. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: After the oxygen-limited pyrolysis carbonization is completed, the pyrolysis product is washed with a 0.8-1.2 mol / L HCl solution for 10-30 minutes.

4. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: The method also includes discarding the supernatant after washing, collecting the precipitate, washing it with deionized water 2-4 times until the pH of the supernatant is 6.5-7.5, collecting the precipitate, drying it in an oven at 60-80°C for 6-12 hours, cooling it, and sieving it to obtain the kudzu waste biochar-type adsorbent with a particle size of 0.1-0.3 mm.

5. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: The kudzu root waste residue is a mixture of one or more of waste kudzu root fibers, kudzu root peels, etc. produced during the kudzu root processing, and its moisture content does not exceed 10%.

6. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: After obtaining the kudzu root waste biochar type adsorbent, the method further includes the steps of sealing and packaging the biochar adsorbent and storing the biochar adsorbent in a dry and cool place with a temperature of 5-25° C. and a humidity of less than 60%.

7. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: The oxygen-limited pyrolysis method is to introduce an inert gas such as nitrogen or argon into a muffle furnace at a gas flow rate of 10-50 mL / min, or to perform pyrolysis and carbonization under vacuum conditions to ensure an oxygen-limited environment during the pyrolysis process. When the inert gas is introduced, the oxygen content during the pyrolysis and carbonization process is less than 5%, and when under vacuum conditions, the vacuum degree is 0.01-0.05 MPa.

8. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: Before placing the kudzu root waste residue powder in a muffle furnace for oxygen-limited pyrolysis and carbonization, the method further includes drying the kudzu root waste residue powder until the moisture content is less than 5%, with a drying temperature of 40-60° C. and a drying time of 8-12 hours.

9. The method for preparing a kudzu root waste biochar-based adsorbent for dye wastewater according to claim 2, characterized in that: During the oxygen-limited pyrolysis carbonization process, the pyrolysis temperature is 850°C, the heating rate is 10°C / min, and the constant temperature carbonization is performed for 2 hours. The prepared kudzu waste biochar-type adsorbent has the best adsorption performance for malachite green, methylene blue and methyl orange.

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