Method for preparing pore channel-adjustable carbon molecular sieve by means of binary activation of heavy oil, and use thereof

Abstract

Provided are a method for preparing a pore channel-adjustable carbon molecular sieve by means of binary activation of heavy oil, and use thereof, which belong to the technical fields of biomass resource utilization and water treatment. The method comprises the following steps: (1) mixing heavy oil with a binary activator, and allowing the mixture to stand to form a carbon-containing precursor mixture, wherein the binary activator is calcium citrate and potassium oxalate; (2) subjecting the carbon-containing precursor mixture to pyrolysis activation in an inert atmosphere, and after completion of the pyrolysis, cooling to obtain biological activated carbon; and (3) washing and drying the biological activated carbon to obtain the carbon molecular sieve. The carbon molecular sieve is used as an adsorbent material for removing dye pollutants from wastewater.

Description

A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil and its application Technical Field

[0001] This invention relates to the fields of biomass resource utilization and water treatment technology, and to a method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil and its application. Background Technology

[0002] With the accelerating pace of global industrialization, industrial wastewater treatment has become a major challenge threatening the sustainable development of the ecological environment. Statistics show that the global annual discharge of untreated industrial wastewater exceeds hundreds of billions of cubic meters, with dye wastewater accounting for as much as 80% and being directly discharged into natural water bodies, totaling hundreds of millions of tons annually and continuing to rise. This type of industrial wastewater, containing complex organic macromolecular dyes, especially typical pollutants such as methyl orange, Congo red, and methylene blue (MB), poses a serious threat to aquatic systems. MB has received particular attention due to its unique physicochemical properties; this substance not only exhibits significant environmental persistence and bioaccumulation but can also cause multiple toxic effects on organisms through the food chain. Studies have confirmed that MB exposure can trigger oxidative stress in aquatic organisms, leading to DNA damage and reproductive dysfunction. More alarmingly, MB pollution has spread from the aquatic environment to the soil system, forming a complex pollution pattern and posing potential risks to farmland ecological security and groundwater quality. Therefore, the effective purification and treatment of dye wastewater has attracted widespread attention.

[0003] In the field of water treatment technology, porous activated carbon materials are widely used in wastewater treatment and purification due to their low cost, high specific surface area, large pore volume, renewability, and excellent adsorption properties. The most commonly used activating agents in traditional activated carbon material production processes are KOH and K₂CO₃.

[0004] For example, the literature (Wang K, Xu S. Preparation of High Specific Surface Area Activated Carbon from Petroleum Coke by KOH Activation in a Rotary Kiln[J]. Processes, 2024, 12(2).DOI:10.3390 / pr12020241.) developed a novel method for preparing activated carbon (AC) from petroleum coke (PC) using a rotary kiln filled with steel balls via KOH activation. This method utilizes molten KOH at a lower activation temperature, which causes the reaction mixture to expand, while molten K2O at a higher temperature causes particle agglomeration. The steel balls alleviate expansion and agglomeration by promoting heat and mass transfer in the reactor, thus promoting the development of the pore structure of AC. The introduction of CO2 during activation further reduces particle agglomeration and forms more mesopores in the AC by converting K2O into thermosetting K2CO3. Furthermore, the literature (Wu C, Liu J, Wang Y, et al. A clean method for controlling pore structure development in potassium activation systems to improve CO2 adsorption properties of biochar[J]. Science of the Total Environment, 2024, 954.DOI:10.1016 / j.scitotenv.2024.176429.) uses a KCl-assisted activation process and three activators (KOH, KHCO3, K2CO3) to prepare CO2 adsorbents with high specific surface area and excellent adsorption performance. However, these methods are corrosive, causing severe corrosion to equipment and posing a risk of heavy metal pollution. Microstructural analysis of carbon materials shows that the activated carbon produced by these methods has a well-developed pore structure and large pore volume, but its pore size structure is relatively dispersed, with most pores failing to function effectively, thus limiting the overall performance of the activated carbon. Based on this, developing binary activation technology based on the concept of green chemistry, and constructing a hierarchical pore system through a synergistic physical-chemical activation mechanism to achieve precise control of pore size distribution, has become a key research direction for breaking through the performance bottleneck of carbon molecular sieve materials. This has important engineering application value for promoting the scientific development of environmental functional materials.

[0005] Heavy oil is a non-water-soluble liquid, mainly formed through the deposition of large molecules during processes such as biomass pyrolysis or gasification. Heavy oil is characterized by its complex composition, high carbon content, low ash content, high viscosity, good thermoplasticity, and easy polymerization. These characteristics make it difficult to directly purify and upgrade it into high-value-added chemicals and liquid fuels through methods such as distillation and extraction. Developing a novel processing technology to transform waste heavy oil into carbon-based molecular sieve adsorbent materials with highly concentrated pore structures via thermochemical methods, and then using it as a high-performance adsorbent for water treatment to remove pollutants, would not only achieve waste reuse but also effectively solve the problem of the difficulty in directly utilizing heavy oil, providing a new approach to environmental pollution control. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a convenient and efficient method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil is provided, comprising the following steps:

[0007] (1) Mix heavy oil and binary activator, and let stand to form a carbon-containing precursor mixture; wherein, the binary activator is calcium citrate and potassium oxalate;

[0008] (2) The carbon-containing precursor mixture is pyrolyzed and activated under an inert atmosphere. After pyrolysis, it is cooled to obtain bio-activated carbon.

[0009] (3) The bio-activated carbon is washed and dried to obtain carbon molecular sieve.

[0010] Preferably, in step (1), the ratio of heavy oil, calcium citrate and potassium oxalate by mass is 2:1:0.25-2.

[0011] The component ratios of heavy oil and binary activator should be controlled within the preferred range of this invention. If the proportion of calcium citrate is too low, it will weaken the ordered arrangement process of carbon microcrystals, which is not conducive to the formation of highly graphitized carbon and will weaken the subsequent K... + Alternatively, it could be the reaction of CO2 molecules with the carbon framework. If the proportion of calcium citrate is too high, its pyrolysis will generate CaO template agents, leading to more site-occupying pore-forming reactions and a significant increase in the mesoporous structure of the produced activated carbon. This is detrimental to the formation of activated carbon adsorbent materials with a highly concentrated pore size distribution. Furthermore, a continuous increase in the overall amount of binary activators is detrimental to environmental and economic sustainability. Therefore, a properly proportioned binary activator can facilitate a synergistic effect between the two activators, thereby forming activated carbon with a highly concentrated pore size distribution and molecular sieve-like properties.

[0012] Preferably, in step (1), the mixing time is 5-30 min and the settling time is 5-30 min.

[0013] Allowing the mixture to stand after mixing helps ensure that the components are mixed evenly.

[0014] Preferably, in step (2), the initial temperature of pyrolysis is room temperature, the heating rate is 5-10 ℃ / min, the pyrolysis temperature is 600-800 ℃, and the holding time is 10-60 min.

[0015] Preferably, in step (2), the inert atmosphere includes at least one of nitrogen, argon, and helium; the gas flow rate is 50-100 mL / min.

[0016] Those skilled in the art can select appropriate pyrolysis equipment, such as a pyrolysis furnace, based on actual conditions. Common pyrolysis furnaces include fluidized bed reactors and fixed bed reactors. Among them, fixed bed reactors have certain advantages over fluidized bed reactors, namely, the activator can fully contact and react with the heavy oil.

[0017] Preferably, in step (3), the bio-activated carbon is washed with dilute acid and water, and then dried at 100-150 °C to obtain carbon molecular sieve.

[0018] More preferably, the type of dilute acid includes at least one of hydrochloric acid, nitric acid, and sulfuric acid; the concentration of the dilute acid is 0.1-1 mol / L.

[0019] In a second aspect of the present invention, a carbon molecular sieve with well-developed pore structure and concentrated pore size distribution is provided, which is prepared by the method provided in the first aspect of the present invention.

[0020] In a third aspect of the invention, an application of the carbon molecular sieve of the second aspect of the invention as an adsorbent material in water treatment is provided.

[0021] Preferably, the carbon molecular sieve is used as an adsorbent material to remove dye pollutants from wastewater.

[0022] Based on the above technical solutions, the design concept and principle of this invention are as follows:

[0023] This invention proposes a method for preparing activated carbon materials by thermally polymerizing heavy components in heavy oil through a simple thermochemical conversion (pyrolysis activation). In this process, the complex composition, high carbon content, low ash content, good thermoplasticity, and ease of polymerization of heavy oil are utilized to overcome its drawbacks of high viscosity, poor flowability, and difficulty in direct utilization. This allows for the efficient conversion of waste heavy oil for use in water purification. Simultaneously, the synergistic coupling effect between the binary green activators is fully utilized to promote the efficient activation reaction. The biomass-derived heavy oil used is widely available, has a high carbon content and high viscosity, and is in a semi-liquid state, perfectly dissolving the binary organic salt activators. This allows the large molecular components in the heavy oil to fully contact the activator molecules, facilitating the efficient functioning of the activators and promoting the efficient activation reaction.

[0024] Traditional methods for selecting activators in thermochemical conversion processes often involve inorganic salts such as KOH and K₂CO₃, which are highly corrosive and not environmentally friendly. This invention selects relatively mild organic salts such as calcium citrate and potassium oxalate as activators, which are not only environmentally friendly but also produce carbon materials with molecular sieve properties.

[0025] The pyrolysis activation process of heavy oil is relatively complex. During pyrolysis, calcium citrate activator generates metal oxide (CaO) and releases CO2 gas. CaO acts as a template agent, guiding the ordered arrangement of carbon microcrystals to form highly graphitized carbon materials, while the released CO2 contributes to the formation of microporous carbon structures. Furthermore, during activation, calcium citrate activator can dissociate calcium ions (CaO) in solution. 2+ ), Ca 2+ Because its high charge density can promote cross-linking between molecules, it connects the macromolecules of heavy components in heavy oil to form macromolecular backbone bridges, which is conducive to the polymerization reaction of macromolecules.

[0026] Potassium oxalate activator forms potassium oxide and releases CO2 during pyrolysis. At high temperatures, the potassium oxide reacts with small carbon molecules in the heavier components through a gasification reaction (C + K2O → CO↑ + 2K), while the generated CO2 can etch the carbon framework (CO2 + C → 2CO), contributing to the formation of microporous carbon. Furthermore, during activation, potassium oxalate activator dissociates into potassium ions (K+) in solution. + ), K + It can promote the generation of free radicals and accelerate chain cleavage reactions. + The presence of [certain substances] promotes chain pyrolysis reactions, forming more aromatic free radicals, and this process contributes to the formation of Ca[substances]. 2+The capture of free radicals generated by pyrolysis and the synergistic effect between them further promote the condensation reaction to form polycyclic aromatic hydrocarbons. In addition, the synergistic effect between the binary activators helps to dynamically adjust the pore structure.

[0027] Therefore, this method is beneficial for forming carbon molecular sieves with uniform pore structure and concentrated pore size distribution, significantly improving the quality of carbon products. Applying carbon molecular sieves to efficient water treatment not only effectively treats waste heavy oil but also synergistically purifies dye wastewater, achieving comprehensive resource utilization of both pollutants.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] This invention provides a method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, which has the advantages of being green and environmentally friendly, convenient, and efficient in production.

[0030] This invention provides a carbon molecular sieve with a well-developed pore structure and concentrated pore size distribution, exhibiting excellent adsorption properties.

[0031] This invention provides an application of carbon molecular sieve as an adsorbent material in water treatment, which has broad application prospects. Attached Figure Description

[0032] Figure 1 is a flowchart of the method and application of preparing tunable carbon molecular sieves by binary activation of heavy oil.

[0033] Figure 2 shows a comparison of the microstructures of the carbon molecular sieve adsorbents prepared in the examples; where (a)-(f) correspond to the observation results of HBAC-0 to HBAC-5 respectively.

[0034] Figure 3 shows a comparison of X-ray diffraction patterns of the carbon molecular sieve adsorbents prepared in the examples;

[0035] Figure 4 shows the physical parameter characterization results of the carbon molecular sieve adsorbents prepared in the examples; where (a) is the nitrogen adsorption-desorption curve of each carbon molecular sieve adsorbent, (b) is the total pore specific surface area of ​​each carbon molecular sieve adsorbent, (c) is the micropore specific surface area of ​​each carbon molecular sieve adsorbent, and (d)-(i) are comparison diagrams of pore size distribution curves corresponding to HBAC-0 to HBAC-5 respectively.

[0036] Figure 5 is a comparison of the adsorption rate and removal rate of adsorbent samples for adsorbed MB under different experimental conditions in the application of the present invention.

[0037] Figure 6 is a comparison of the effects of adsorbent samples on MB adsorption under different experimental conditions in the application of the present invention; where (a) is the relationship between the initial concentration of MB and the amount of adsorption, and (b) is the relationship between adsorption time and the amount of adsorption. Embodiments of the present invention

[0038] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0039] In the following embodiments:

[0040] The commercial source of the activated carbon is Huajing Activated Carbon Co., Ltd., and the product type is coconut shell water purification carbon.

[0041] Biomass heavy oil is obtained by pyrolyzing pine wood flour in an inert atmosphere (nitrogen atmosphere, purity 99.999%) at 500 °C for 1 h, followed by condensation and collection of the lower viscous liquid phase of the bio-oil.

[0042] Example 1

[0043] A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, the steps of which are as follows:

[0044] (1) The heavy components obtained from the pyrolysis of pine wood were selected as heavy oil samples. The heavy oil, calcium citrate and potassium oxalate activator were weighed according to the mass ratio of 2:1:0.125 and mixed thoroughly. After standing, a carbon-containing precursor mixture was formed.

[0045] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0046] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a forced-air drying oven to obtain carbon molecular sieve adsorbent, denoted as HBAC-1.

[0047] Example 2

[0048] A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil is shown in Figure 1, and the steps are as follows:

[0049] (1) Select the heavy component obtained from pine wood pyrolysis as heavy oil sample. Weigh the heavy oil, calcium citrate and potassium oxalate activator in a mass ratio of 2:1:0.25 and mix them thoroughly. After standing, a carbon-containing precursor mixture is formed.

[0050] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0051] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a blower drying oven to obtain carbon molecular sieve adsorbent, which is denoted as HBAC-2.

[0052] Example 3

[0053] A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, the steps of which are as follows:

[0054] (1) Select the heavy component obtained from pine wood pyrolysis as heavy oil sample, weigh the heavy oil, calcium citrate and potassium oxalate activator according to the mass ratio of 2:1:0.5, mix them thoroughly, and let them stand to form a carbon-containing precursor mixture;

[0055] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0056] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a blower drying oven to obtain carbon molecular sieve adsorbent, which is denoted as HBAC-3.

[0057] Example 4

[0058] A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, the steps of which are as follows:

[0059] (1) Select the heavy component obtained from pine wood pyrolysis as heavy oil sample, weigh the heavy oil, calcium citrate and potassium oxalate activator in a mass ratio of 2:1:1, mix them thoroughly, and let them stand to form a carbon-containing precursor mixture;

[0060] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0061] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a blower drying oven to obtain carbon molecular sieve adsorbent, which is denoted as HBAC-4.

[0062] Example 5

[0063] A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, the steps of which are as follows:

[0064] (1) Select the heavy component obtained from pine wood pyrolysis as heavy oil sample, weigh the heavy oil, calcium citrate and potassium oxalate activator in a mass ratio of 2:1:2, mix them thoroughly, and let them stand to form a carbon-containing precursor mixture;

[0065] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0066] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a blower drying oven to obtain carbon molecular sieve adsorbent, which is denoted as HBAC-5.

[0067] Comparative Example 1

[0068] In this comparative example, commercial activated carbon (CAC) was selected as the blank control adsorbent.

[0069] Comparative Example 2

[0070] The preparation steps of the mono-component activated heavy oil-based activated carbon in this comparative example are as follows:

[0071] (1) Select the heavy component obtained from pine wood pyrolysis as heavy oil sample, weigh the heavy oil and potassium oxalate activator at a mass ratio of 1:1 and mix them thoroughly. After standing, a carbon-containing precursor mixture is formed.

[0072] (2) The mixed carbon precursor was transferred to a fixed-bed reactor for pyrolysis. Nitrogen gas was introduced as the reaction atmosphere at a flow rate of 100 mL / min and a heating rate of 10 ℃ / min. The temperature was raised to 800 ℃ and held for 60 min. After pyrolysis, the carbon precursor was cooled to obtain bio-activated carbon.

[0073] (3) After collecting the biological activated carbon, it is washed multiple times with dilute acid and deionized water until neutral, and then dried in a blower drying oven to obtain mono-activated heavy oil-based activated carbon, denoted as HBAC-0.

[0074] Test Example 1

[0075] The microstructure of the carbon molecular sieve adsorbents was observed using cold field emission scanning electron microscopy, and the results are shown in Figure 2. The microstructure of HBAC-0 is shown in Figure 2(a). HBAC-0 is an irregular granular structure with a certain degree of pore structure on its surface. The microstructures of HBAC-1 to HBAC-5 are shown in Figures 2(b)-(f), all exhibiting irregular granular structures. Furthermore, the pore structure on the surface becomes more developed with increasing potassium oxalate activator dosage.

[0076] The crystal structure of the carbon molecular sieve adsorbent was tested using X-ray diffraction, and the results are shown in Figure 3. As can be seen from the figure, the typical carbon crystal planes (002) and (100) can be observed in the crystal structure of HBAC-0. The typical carbon crystal planes (002) and (100) can also be observed in HBAC-1 to HBAC-5.

[0077] The pore structure of the carbon molecular sieve adsorbent was analyzed using a fully automated specific surface area and pore structure analyzer, and the results are shown in Figure 4. The nitrogen adsorption-desorption and pore size distribution curves of the HBAC-0 adsorbent are shown in Figures 4(a) and 4(d), with a total pore specific surface area and a micropore specific surface area of ​​1147 m². 2 / g and 1050 m 2 / g, see Figure 4(b) and Figure 4(c). The nitrogen adsorption-desorption and pore size distribution curves of the carbon molecular sieve adsorbents (HBAC-1 to HBAC-5) are shown in Figure 4(a) and Figure 4(e)-(i). It can be clearly seen that their pore sizes are mainly concentrated around 0.8 nm, exhibiting obvious molecular sieve structural characteristics. The specific surface areas of the carbon molecular sieves are shown in Figure 4(b) and Figure 4(c), where the total pore specific surface area and micropore specific surface area of ​​HBAC-5 reach 1857 m², respectively. 2 / g and 1559 m 2 / g.

[0078] Test Example 2

[0079] This test example examines the adsorption performance of the above samples in practical applications. The steps are as follows:

[0080] 1) Weigh 50 mg of the sample and add it to 50 mL of MB with a specific concentration (25-1000 mg / L) in an Erlenmeyer flask, and transfer it to a shaker to adsorb at room temperature for a certain period of time (0-1440 min).

[0081] 2) After the adsorption process is completed, the solution is subjected to solid-liquid separation to obtain a liquid phase that does not contain solids;

[0082] 3) Transfer the pure liquid phase to a cuvette and measure its absorbance using a UV spectrophotometer with the UV wavelength set to 664 nm.

[0083] Figure 5 shows the equilibrium adsorption capacity and MB removal rate of each adsorbent sample (CAC, HBAC-0 to HBAC-5) when the initial MB concentration is 1000 mg / L. As can be seen from the figure, the equilibrium adsorption capacity of CAC can reach 428.9 mg / g, and the MB removal rate is 42.9%. The equilibrium adsorption capacity of HBAC-0 adsorbent, obtained by activation of heavy oil with a single activator, is only 356.7 mg / g, and the MB removal rate is 35.7%. However, the adsorption capacity of the carbon molecular sieve adsorbents (HBAC-1 to HBAC-5) obtained by activation of heavy oil with a binary activator is significantly improved. Among them, HBAC-5 has the highest adsorption capacity and removal rate, at 819.3 mg / g and 81.9%, respectively, which is 1.91 times that of commercial activated carbon and 2.30 times that of the single-component activated HBAC-0 adsorbent.

[0084] The adsorption capacity of each adsorbent sample for MB at different initial concentrations is shown in Figure 6(a). It can be seen that as the initial concentration of MB increases, the adsorption capacity of each adsorbent for MB also shows a gradual increasing trend. When the initial concentration of MB reaches 800 mg / L, the adsorption capacity of HBAC-5 reaches 724.5 mg / g, which is 1.70 times that of CAC (425.8 mg / g) and 1.97 times that of HBAC-0 (368.3 mg / g). The adsorption capacity of MB for each adsorbent sample at different adsorption times is shown in Figure 6(b). The results show that the adsorption capacity of MB for each adsorbent gradually increases with the increase of adsorption time. Among them, the adsorption capacities of HBAC-3, HBAC-4 and HBAC-5 after 24 h of adsorption are 674.6 mg / g, 676.3 mg / g and 724.5 mg / g, respectively, which are much higher than those of CAC (425.9 mg / g) and HBAC-0 (356.7 mg / g).

[0085] Compared with existing technologies, this invention provides a method for preparing tunable-pore carbon molecular sieves using a binary green activation process for heavy oil. Leveraging the complex composition, high carbon content, low ash content, good thermoplasticity, and ease of polymerization of heavy oil, it overcomes the drawbacks of high viscosity, poor flowability, and difficulty in direct utilization. This allows for the efficient conversion of waste heavy oil for use in water purification. Simultaneously, it fully utilizes the synergistic coupling effect between the binary green activators, promoting efficient activation reactions. The biomass-derived heavy oil used in this invention is widely available, high in carbon and viscosity, and in a semi-liquid state, perfectly dissolving the binary organic salt activators. This allows for sufficient contact between the macromolecular components in the heavy oil and the activator molecules, facilitating the efficient functioning of the activators and promoting efficient activation reactions. This results in the formation of carbon molecular sieves with uniform pore structure and concentrated pore size distribution, significantly improving the quality of the carbon product. Subsequently, the carbon molecular sieves are applied to efficient water treatment, effectively treating waste heavy oil while simultaneously purifying dye wastewater, achieving resource utilization of both waste heavy oil and dye wastewater pollutants.

[0086] In summary, this invention innovatively employs a two-component green activator combined with waste heavy oil, and successfully prepares a carbon-based molecular sieve material with a directional pore structure through a programmed temperature-controlled pyrolysis activation coupled with post-treatment. The resulting material possesses a significant three-dimensional hierarchical pore system, exhibiting a highly concentrated pore size distribution compared to carbon materials prepared by traditional methods. This material demonstrates superior adsorption performance for methylene blue, a typical organic pollutant in water, with a maximum adsorption capacity of 819 mg / g, which is 91% higher than that of commercially available activated carbon, and also possesses excellent adsorption kinetics. This technology offers advantages such as simple preparation process, environmental friendliness, and low cost, not only realizing the resource utilization of agricultural and forestry waste, but also providing an innovative solution for the development of highly efficient water treatment adsorption materials, thus possessing significant environmental and economic benefits.

[0087] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil, characterized in that, Includes the following steps: (1) Mix heavy oil and binary activator, and let stand to form a carbon-containing precursor mixture; wherein, the binary activator is calcium citrate and potassium oxalate; (2) The carbon-containing precursor mixture is pyrolyzed and activated under an inert atmosphere. After pyrolysis, it is cooled to obtain bio-activated carbon. (3) The bio-activated carbon is washed and dried to obtain carbon molecular sieve.

2. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 1, characterized in that: In step (1), the ratio of heavy oil, calcium citrate, and potassium oxalate by mass is 2:1:0.25-2.

3. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 1, characterized in that: In step (1), the mixing time is 5-30 min and the settling time is 5-30 min.

4. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 1, characterized in that: In step (2), the initial temperature of pyrolysis is room temperature, the heating rate is 5-10 ℃ / min, the pyrolysis temperature is 600-800 ℃, and the holding time is 10-60 min.

5. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 1, characterized in that: In step (2), the inert atmosphere includes at least one of nitrogen, argon, and helium; the gas flow rate is 50-100 mL / min.

6. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 1, characterized in that: In step (3), the bio-activated carbon is washed with dilute acid and water, and then dried at 100-150 °C to obtain carbon molecular sieve.

7. The method for preparing tunable-pore carbon molecular sieves by binary activation of heavy oil according to claim 6, characterized in that: The type of dilute acid includes at least one of hydrochloric acid, nitric acid, and sulfuric acid; the concentration of the dilute acid is 0.1-1 mol / L.

8. A carbon molecular sieve, characterized in that: It is prepared by the method described in any one of claims 1-7.

9. An application of the carbon molecular sieve as described in claim 8 as an adsorbent material in water treatment.

10. The application according to claim 9, characterized in that: The carbon molecular sieve is used as an adsorbent material to remove dye pollutants from wastewater.

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