Modified coal-based activated carbon for sewage treatment and preparation method and application thereof

Abstract

The application relates to the technical field of wastewater treatment materials, in particular to modified coal quality activated carbon for sewage treatment and a preparation method and application thereof. The adsorption material is prepared by mixing and sintering after impregnation of a composite nitrate solution with coal powder and CNC as a matrix, realizes oxidation hole expansion and metal / amino dual functionalization. The adsorption material of the application has excellent adsorption efficiency (>=90%) and long-term stability in composite pollution water quality containing organic matter and heavy metals, and can effectively meet the application in complex pollution water quality.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment materials technology, and more specifically, it relates to a modified coal-based activated carbon for wastewater treatment, its preparation method, and its application. Background Technology

[0002] In recent years, in response to the country's green development policy, heavy industry has begun to implement stricter controls on wastewater discharge and treatment, with organic pollution of water bodies being the most common. Based on this, various adsorption materials that can effectively remove organic matter or its derivatives from water bodies have been tested.

[0003] The adsorption materials used in related technologies are still mainly low-cost natural materials, such as activated carbon, zeolite, and fly ash. They mainly rely on van der Waals forces and pore retention to adsorb organic matter in water, i.e., physical adsorption. They have strong adaptability and broad-spectrum properties.

[0004] However, the above-mentioned adsorption materials are more suitable for preliminary water treatment or systems with relatively simple water composition (only organic matter), and cannot meet the application requirements in water with complex pollution (organic matter + heavy metals). In addition, they have weak regenerability and stability. Therefore, based on the shortcomings of existing adsorption materials, a modified coal-based activated carbon for wastewater treatment and its preparation method are provided. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a modified coal-based activated carbon for wastewater treatment and its preparation method. This adsorption material still exhibits excellent adsorption efficiency (≥90%) and long-term stability in complex polluted water containing organic matter and heavy metals.

[0006] In a first aspect, this application provides a modified coal-based activated carbon for wastewater treatment, employing the following technical solution:

[0007] A modified coal-based activated carbon for wastewater treatment, wherein the modified coal-based activated carbon is prepared by impregnating coal powder with CNC in a composite nitrate solution and then sintering.

[0008] The composite nitrate solution is composed of ferric nitrate, lanthanum nitrate, ammonium nitrate and water.

[0009] Preferably, the composite nitrate solution comprises the following components by weight percentage:

[0010] Ferric nitrate 15-18 wt%, lanthanum nitrate 7-9 wt%, ammonium nitrate 5-7 wt%, water as balance.

[0011] Preferably, the ratio of the amount of coal powder, CNC and compound nitrate solution is 1:(0.1-0.2):(2-3).

[0012] Preferably, the pulverized coal is anthracite with an ash content of ≤5% and a particle size of 80-120 mesh.

[0013] Preferably, the CNC has a diameter of 10-20 nm, a length of 200-500 nm, a crystallinity of >85%, and a surface charge of -35 mV to -50 mV.

[0014] Preferably, the sintering is a staged heating sintering under staged nitrogen conditions.

[0015] By adopting the above technical solution, modified coal-based activated carbon is prepared by impregnating a composite nitrate solution with coal powder and CNC as the matrix and then mixing and sintering. This achieves oxidation pore expansion and metal / amino bifunctionalization, and based on this, it enables the treatment of organic matter and heavy metals in complex water quality.

[0016] Secondly, this application provides a method for preparing modified coal-based activated carbon for wastewater treatment, employing the following technical solution:

[0017] A method for preparing modified coal-based activated carbon for wastewater treatment includes the following steps:

[0018] S1. First, mix and impregnate the coal powder, CNC and composite nitrate solution according to the corresponding weight ratio, and stir at a constant temperature of 60℃ for 1-3 hours. After the mixture is uniform, the sintering precursor is obtained for later use.

[0019] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0020] 1) Dehydrate the coal precursor obtained in S1 at 100-120℃ for 1-2 hours;

[0021] 2) After heating to 250-280℃, nitrogen gas is introduced and sintering continues for 1-2 hours;

[0022] 3) Heat to 300-350℃ for amino fixation treatment for 0.5-1 hour;

[0023] 4) Heat to 600-620℃ and perform metal oxidation treatment for 0.5-1h.

[0024] By adopting the above technical solution, the modified coal-based activated carbon for wastewater treatment produced by the above steps has stable and uniform performance, exhibiting excellent pore structure and heavy metal adsorption effect, and its service life is also significantly extended. Based on the relevant data analysis, the underlying principle may be as follows:

[0025] After dehydration in step 1), the obtained coal precursor decomposes ammonium nitrate in step 2) and releases HNO3, thereby oxidizing the carbon surface (forming -COOH), with NH3 as the nitrogen source;

[0026] The main modification in step 3) is amino grafting (primary amine generation), and in step 4) it is metal oxide fixation. O2 / NO2 further expands the pores. In addition, the nitrogen gas introduced from step 2) effectively inhibits the oxidative decomposition of amino at temperatures above 300°C.

[0027] Thirdly, this application provides a modified coal-based activated carbon for wastewater treatment, or the application of the product obtained by the above process, which is particularly suitable for the treatment of wastewater with complex polluted water quality (heavy metals + organic matter), and has better long-term applicability and universality.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. In this application, modified coal-based activated carbon is prepared by impregnating coal powder and CNC with a composite nitrate solution and then mixing and sintering. This achieves oxidation pore expansion and metal / amino dual functionalization, thereby ensuring the treatment effect on wastewater with complex pollutants (heavy metals + organic matter).

[0030] 2. The modified coal-based activated carbon for wastewater treatment prepared by the process described in this application has relatively stable and uniform performance due to the precision and controllability of the process. It has achieved sufficient oxidation and pore expansion and metal / amino bifunctionalization, and has excellent long-term stability, with significant industrialization value.

[0031] 3. The modified coal-based activated carbon adsorbent material for wastewater treatment in this application can effectively meet the application requirements of wastewater treatment in complex polluted water (heavy metals + organic matter) compared with natural adsorbent materials. It also has better long-term applicability and universality, and its cost is still lower than that of synthetic materials such as silicone resin. Detailed Implementation

[0032] The following detailed description of this application is based on the embodiments. Except for some specifications that are explicitly limited, the raw materials used in this application are all commercially available common materials.

[0033] Preparation Examples 1-5

[0034] A complex nitrate solution, comprising the following components by weight percentage (per 100 kg):

[0035] Table: Components and their weights (kg) in Preparation Examples 1-5

[0036]

[0037] Performance testing

[0038] The modified coal-based activated carbon prepared in the examples was selected as the test object, and its specific surface area, mesoporous ratio, macroporous ratio, phenol adsorption capacity, heavy metal adsorption capacity, and acid and alkali resistance were tested respectively. The specific test methods and conditions are as follows:

[0039] Unmodified coal-based activated carbon (ash content ≤5%, particle size 100 mesh) served as the control group.

[0040] 1) Specific surface area (BET) and mesoporous ratio (BJH) test

[0041] 1.1) Sample pretreatment:

[0042] First, weigh 50 mg of coal-based activated carbon as a sample, place it in a sample tube, and then degas it under vacuum at 200℃ for 6 hours (degassing instrument: VacPrep061), avoiding contact with air.

[0043] 1.2) N2 adsorption-desorption test (Micromeritics ASAP 2460 surface area analyzer):

[0044] The sample tube was first equilibrated in a liquid nitrogen bath (77K), and then the relative pressure range (P / P0: 0.05-0.30) and full range scan (P / P0: 0.01-0.99) were controlled to obtain the adsorption-desorption isotherm.

[0045] Then, their specific surface areas were calculated using the BET model.

[0046] The desorption branch data were analyzed using the BJH method to calculate the pore volume percentage in the 2-50 nm pore size range.

[0047] The pore volume percentage in the >50 nm pore size range was determined by mercury porosimetry.

[0048] The testing standards are in accordance with GB / T 19587-2017 and ASTM D4641-2017.

[0049] 2) Dynamic adsorption capacity test (liquid column experiment)

[0050] 2.1 Adsorption column packing:

[0051] Weigh out coal-based activated carbon as a sample and fill it evenly into a 20 mm × 300 mm adsorption column at a packing density of 0.35 ± 0.02 g / cm³. Fix both ends of the adsorption column with quartz wool and a 100-mesh sieve.

[0052] 2.2 Test conditions:

[0053] Using simulated water bodies, tests were conducted at a flow rate of 10 BV / h and 25±1℃, and the results were verified by online ICP-OES (Cr). 6+ ) and HPLC (phenol) to record concentration changes;

[0054] The components and contents of the simulated water body are shown in the table below (simulating wastewater from a complex system).

[0055] Components concentration use phenol 50 ppm Represents small molecule organic compounds <![CDATA[Cr 6+ (K2Cr2O7)]]> 50 ppm Representing heavy metals humic acid 100 mg / L Simulated colloidal blockage

[0056] Adsorption capacity Q 苯酚 and Q 重金属 calculate:

[0057]

[0058] Where Q is the adsorption capacity (mg / g), C0 is the inlet pollutant concentration (mg / L), F is the flow rate (L / min), and t breakthrough denoted as breakthrough time (min), and m as sample mass (g).

[0059] 3) Acid and alkali resistance - acid and alkali combined accelerated aging treatment

[0060] First, the test sample (modified coal-based activated carbon) was immersed in 1M H2SO4 solution (pH=1) for 24 hours, then washed with deionized water until neutral, and dried at 80℃.

[0061] The test sample (modified coal-based activated carbon) was then immersed in 1M NaOH solution (pH=13) for 24 hours, washed with deionized water until neutral, and dried at 80°C.

[0062] Then, following the dynamic adsorption capacity test in section 2), the total adsorption capacity Q before and after coal-based activated carbon treatment was recorded again. before and Q after And based on the ratio of the two, the adsorption efficiency retention rate is obtained.

[0063] Example

[0064] Example 1

[0065] A modified coal-based activated carbon for wastewater treatment is prepared using the following steps:

[0066] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.1:1 to obtain a coal precursor for later use.

[0067] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0068] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0069] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0070] 2) After heating to 250℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0071] 3) Heat to 300℃ for amino fixation treatment for 0.5 h;

[0072] 4) Heat to 600℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0073] Example 2

[0074] A modified coal-based activated carbon for wastewater treatment is prepared using the following steps:

[0075] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.1:2 to obtain the coal precursor for later use.

[0076] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0077] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0078] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0079] 2) After heating to 250℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0080] 3) Heat to 300℃ for amino fixation treatment for 0.5 h;

[0081] 4) Heat to 600℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0082] Example 3

[0083] A modified coal-based activated carbon for wastewater treatment is prepared using the following steps:

[0084] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.15:2.5 to obtain the coal precursor for later use.

[0085] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0086] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0087] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0088] 2) After heating to 250℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0089] 3) Heat to 300℃ for amino fixation treatment for 0.5 h;

[0090] 4) Heat to 600℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0091] Example 4

[0092] A modified coal-based activated carbon for wastewater treatment is prepared using the following steps:

[0093] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.2:3 to obtain the coal precursor for later use.

[0094] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0095] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0096] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0097] 2) After heating to 250℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0098] 3) Heat to 400℃ for amino fixation treatment for 0.5 h;

[0099] 4) Heat to 600℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0100] Example 5

[0101] A modified coal-based activated carbon for wastewater treatment is prepared using the following steps:

[0102] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.2:4 to obtain the coal precursor for later use.

[0103] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0104] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0105] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0106] 2) After heating to 250℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0107] 3) Heat to 400℃ for amino fixation treatment for 0.5 h;

[0108] 4) Heat to 600℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0109] Ten groups of modified coal-based activated carbon for wastewater treatment prepared in Examples 1-5 were selected, and their specific surface area, mesopore ratio, macropore ratio, phenol adsorption capacity, heavy metal adsorption capacity, and acid and alkali resistance were tested respectively. The average value of the test results was recorded in the table below.

[0110] Table: Performance Test Results of Examples 1-5

[0111]

[0112] As can be seen from the table above, the modified coal-based activated carbons for wastewater treatment prepared in Examples 1-5 all possess excellent pore structure and adsorption capacity, effectively meeting the purification needs of complex water qualities. Compared with the control group using unmodified coal-based activated carbon, they all show varying degrees of improvement, as detailed below:

[0113] Its specific surface area is as high as 1120-1240 m² / g, which is about 72-90% higher than that of the control group;

[0114] Its mesopore ratio was 35-38%, and its macropore ratio was 34-35%, both of which were much higher than those of the control group;

[0115] Its phenol adsorption capacity is as high as 172-182 mg / g, which is about 152-167% higher than that of the control group, demonstrating its excellent organic matter adsorption and treatment capabilities.

[0116] Its heavy metal adsorption capacity is as high as 53.1-56.2 mg / g, which is about 261-282% higher than that of the control group, indicating that it has excellent heavy metal adsorption and treatment capacity after modification.

[0117] It also has an acid resistance of about 85%, and possesses excellent long-term usability and weather resistance.

[0118] In summary, coal-based activated carbon is prepared by impregnation with a composite nitrate solution followed by sintering, achieving oxidation pore expansion and metal / amino bifunctionalization, thus enhancing the adsorption treatment effect of complex water quality. The ratio of coal powder, CNC and composite nitrate solution is 1:(0.1-0.2):(2-3).

[0119] Based on the various data, the possible reasons are as follows:

[0120] 1) Synergistic enhancement mechanism of CNC - nanotemplate effect:

[0121] CNC (cellulose nanocrystals), as rigid nanofibers (10-20 nm in diameter), form a three-dimensional network framework during sintering, which inhibits the excessive melting and agglomeration of coal powder particles, creates a hierarchical pore structure (micropores + mesopores), and improves specific surface area and diffusion efficiency.

[0122] Furthermore, thanks to the negative charge (-35~-50 mV) on the CNC surface, it also attracts metal cations (Fe) from the composite nitrate through electrostatic interaction. 3+ / La 3+ This achieves uniform loading of metal active sites, avoiding sintering and agglomeration. CNC high-temperature carbonization forms a conductive carbon network, enhancing the electronic conductivity of activated carbon and promoting redox adsorption (such as Cr). 6+ Reduced to Cr 3+ It is important to avoid high-temperature decomposition and excessive pore blockage.

[0123] 2) Targeted functionalization of complex nitrates

[0124] 2.1 Ferric nitrate (Fe(NO3)3):

[0125] Pyrolysis generates α-Fe₂O₃ / Fe₃O₄ nanoparticles, providing:

[0126] (1) Chemisorption sites for heavy metals (such as As) 3+ / Pb 2+ (Complexed with Fe—O bonds);

[0127] (2) Fenton-like catalytic activity, degrading organic pollutants (H2O2→·OH).

[0128] 2.2 Lanthanum nitrate (La(NO3)3):

[0129] The formation of La₂O₃ / La(OH)₃, due to its strong Lewis acidity, preferentially adsorbs oxygen-containing anions (PO₄²⁻). 3- F - );

[0130] It works synergistically with Fe to increase the surface oxygen vacancy concentration and enhance electron transfer efficiency.

[0131] 2.3 Ammonium nitrate (NH4NO3):

[0132] High-temperature explosive decomposition (NH4NO3→ N2O + 2H2O) creates and expands pores;

[0133] The released NH3 reacts with carboxyl groups to generate amide / pyridine nitrogen groups, thereby enhancing the affinity for organic pollutants.

[0134] 3) Shape and property control mechanism of segmented sintering

[0135] 3.1 Low-temperature dehydration (100-120℃):

[0136] Remove free water to prevent pore collapse in the subsequent high-temperature section.

[0137] 3.2 Medium-temperature nitrogen sintering (250-280℃):

[0138] An inert atmosphere inhibits the oxidation of organic matter and promotes the gradual decomposition of nitrates into metal oxide precursors.

[0139] 3.3 Amino fixation segment (300-350℃):

[0140] CNC and the carboxyl groups in coal react with NH3 to generate nitrogen-containing functional groups (—CONH2, —NH2), which enhance the adsorption of cationic dyes.

[0141] 3.4 High-temperature metal oxidation (600-620℃):

[0142] The growth of Fe / La oxide crystal phase is activated, and the graphitization of the carbon skeleton improves mechanical stability. Therefore, the control group obviously cannot achieve the above effects.

[0143] Examples 6-9

[0144] A modified coal-based activated carbon for wastewater treatment differs from Example 3 in that the modified coal-based activated carbon used is used differently, and the specific correspondence is shown in the table below.

[0145] Table: Comparison of the use of modified coal-based activated carbon in Examples 6-9

[0146] Group Modified coal-based activated carbon Example 6 Prepared from Preparation Example 2 Example 7 Prepared from Preparation Example 3 Example 8 Prepared from Preparation Example 4 Example 9 Prepared from Preparation Example 5

[0147] Ten groups of modified coal-based activated carbon for wastewater treatment prepared in Examples 6-9 were selected, and their specific surface area, mesopore ratio, macropore ratio, phenol adsorption capacity, heavy metal adsorption capacity, and acid and alkali resistance were tested respectively. The average value of the test results was recorded in the table below.

[0148] Table: Performance Test Results of Examples 6-9

[0149]

[0150] As can be seen from the table above, the modified coal-based activated carbons for wastewater treatment prepared in Examples 6-9 all possess excellent pore structure and adsorption capacity, effectively meeting the purification needs of complex water qualities. Compared with the control group using unmodified coal-based activated carbon, they all show varying degrees of improvement.

[0151] As can be seen from Examples 1 and 6-9, the composite nitrate solution is preferably composed of the following components by weight percentage: 15-18 wt% ferric nitrate, 7-9 wt% lanthanum nitrate, 5-7 wt% ammonium nitrate, and water as the balance. Examples 1 and 9 with performance slightly decreased when the range is exceeded, which is presumably due to the limited degree of modification.

[0152] In summary, it can be concluded that Examples 6-8 are preferred embodiments of this application, with a specific surface area as high as 1250-1260 m² / g, a mesoporous ratio as high as 39%, a macroporous ratio as high as 36%, a phenol adsorption capacity of approximately 185 mg / g, a heavy metal adsorption capacity of 56.5-57.2 mg / g, and an acid and alkali resistance retention rate of approximately 85%. It is evident that these embodiments are suitable for the treatment of industrial wastewater with complex components, and exhibit superior long-term applicability and versatility.

[0153] Example 10

[0154] A modified coal-based activated carbon for wastewater treatment differs from Example 3 in that it has the same components but a different preparation process. Specifically, it is prepared using the following steps:

[0155] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.2:3 to obtain the coal precursor for later use.

[0156] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0157] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0158] 1) The coal precursor obtained in S1 was dehydrated at 120℃ for 1 hour;

[0159] 2) After heating to 280℃, nitrogen gas is introduced and sintering continues for 1 hour;

[0160] 3) Heat to 350℃ for amino fixation treatment for 0.5 h;

[0161] 4) Heat to 620℃ and perform metal oxidation treatment for 0.5h to obtain modified coal-based activated carbon.

[0162] Comparative Example 1

[0163] A modified coal-based activated carbon for wastewater treatment differs from Example 3 in that it has the same components but a different preparation process. Specifically, it is prepared using the following steps:

[0164] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.2:3 to obtain the coal precursor for later use.

[0165] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0166] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0167] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0168] 2) After heating to 250℃, continue sintering for 2 hours;

[0169] 3) Heat to 400℃ for amino fixation treatment for 0.5 h;

[0170] 4) Heat to 600℃ and perform metal oxidation treatment for 1 hour to obtain modified coal-based activated carbon.

[0171] Comparative Example 2

[0172] A modified coal-based activated carbon for wastewater treatment differs from Example 3 in that it has the same components but a different preparation process. Specifically, it is prepared using the following steps:

[0173] S1. First, mix and impregnate the coal powder, CNC and the composite nitrate solution obtained in Preparation Example 1 at a weight ratio of 1:0.2:3 to obtain the coal precursor for later use.

[0174] The above-mentioned coal powder is anthracite with ash content ≤5% and particle size 100 mesh; the CNC has a diameter of 10-20 nm, a length of 200-500 nm, crystallinity >85%, and surface charge of -35 mV to -50 mV.

[0175] S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows:

[0176] 1) The coal precursor obtained in S1 was dehydrated at 100℃ for 1 hour;

[0177] 2) Heat to 400℃ for amino fixation treatment for 2.5 h;

[0178] 3) Heat to 600℃ and perform metal oxidation treatment for 1 hour to obtain modified coal-based activated carbon.

[0179] Ten groups of modified coal-based activated carbon for wastewater treatment prepared in Example 10 and Comparative Examples 1-2 were selected, and their specific surface area, mesopore ratio, macropore ratio, phenol adsorption capacity, heavy metal adsorption capacity, and acid and alkali resistance were tested respectively. The average value of the test results was recorded in the table below.

[0180] Table: Performance test results of Example 10 and Comparative Examples 1-2

[0181]

[0182] As can be seen from the table above, the modified coal-based activated carbon for wastewater treatment prepared in Example 10 all exhibit excellent pore structure and adsorption performance, with no significant performance fluctuation compared to Example 3. This indicates that the performance can be expected to vary within the preferred parameter range, therefore further details are omitted.

[0183] However, by comparing with Comparative Examples 1-2, it can be seen that the absence of a nitrogen atmosphere or staged temperature control significantly affects its various performance characteristics. The possible reasons for this are:

[0184] 1) Without the protective reducing atmosphere, in the 250-400℃ range, amino groups oxidize and decompose into NO2, and beyond 400℃, the reducing atmosphere causes Fe... 3+ Reduced to Fe 2+ ;

[0185] 2) Non-staged long-term heating causes irreversible thermal decomposition of CNC (cellulose nanocrystals) at high temperatures (>250℃), resulting in the complete loss of its template pore-forming function. Therefore, it is necessary to ensure its corresponding effect through segmentation and appropriate dosage ratio.

[0186] The above are all modifications that can be made to this embodiment without contributing any inventive step, or solutions that clearly constitute technical teaching, after reading this specification. However, as long as they are within the scope of the claims of this application, they should be protected by patent law.

Claims

1. A modified coal-based activated carbon for wastewater treatment, characterized in that, The modified coal-based activated carbon is prepared by impregnating coal powder with CNC in a composite nitrate solution and then sintering it. The composite nitrate solution is composed of the following components by weight percentage: Ferric nitrate 15-18 wt%, Lanthanum nitrate 7-9 wt%, Ammonium nitrate 5-7 wt%, Water as balance; The CNC is cellulose nanocrystals; The weight ratio of the pulverized coal, CNC, and composite nitrate solution is 1:(0.1-0.2):(2-3); The specific preparation steps are as follows: S1. First, mix and impregnate the coal powder, CNC and composite nitrate solution according to the corresponding weight ratio, and stir at a constant temperature of 60℃ for 1-3 hours. After the mixture is uniform, the sintering precursor is obtained for later use. S2. Then, the sintering precursor obtained in S1 is sintered, and the specific process is as follows: 1) Dehydrate the coal precursor obtained in S1 at 100-120℃ for 1-2 hours; 2) After heating to 250-280℃, nitrogen gas is introduced and sintering continues for 1-2 hours; 3) Heat to 300-350℃ for amino fixation treatment for 0.5-1 hour; 4) Heat to 600-620℃ and perform metal oxidation treatment for 0.5-1h.

2. The modified coal-based activated carbon for wastewater treatment according to claim 1, characterized in that, The pulverized coal is anthracite with an ash content of ≤5% and a particle size of 80-120 mesh.

3. The modified coal-based activated carbon for wastewater treatment according to claim 1, characterized in that, The CNC has a diameter of 10-20 nm, a length of 200-500 nm, a crystallinity of >85%, and a surface charge of -35 mV to -50 mV.

4. The application of the modified coal-based activated carbon for wastewater treatment according to any one of claims 1-3, characterized in that: It is suitable for treating industrial wastewater with complex components, and has good long-term applicability and versatility.

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