Preparation method and application of modified lignin / waste white clay co-pyrolysis adsorbent

Abstract

The present application belongs to the field of environmental functional material preparation and water treatment technology, and particularly relates to a preparation method of modified lignin / waste white clay co-pyrolysis adsorbent and application thereof. The preparation method comprises the following steps: (1) preparation of clay-based biochar; (2) preparation of iron-loaded adsorbent; (3) preparation of modified lignin / waste white clay co-pyrolysis adsorbent. The preparation method of the modified lignin / waste white clay co-pyrolysis adsorbent uses clay-based biochar prepared by co-pyrolysis of lignin and waste white clay as a modified precursor raw material, realizes high-value utilization of solid waste, and significantly increases the content of oxygen-containing functional groups on the surface of the adsorbent through combined modification of iron loading and nitric acid oxidation, optimizes the pore structure, and constructs a mesoporous-macroporous multi-level pore structure, which is beneficial to the diffusion and adsorption of BPA molecules. The prepared adsorbent provides a feasible path for efficient removal and degradation of BPA in water and regeneration of the adsorbent.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional material preparation and water treatment technology, specifically relating to a method for preparing a modified lignin / waste clay co-pyrolysis adsorbent and its application. Background Technology

[0002] Bisphenol A (BPA), one of the world's most produced chemicals, is widely used in the production of polycarbonate plastics and epoxy resins. Due to its endocrine-disrupting effects and ecotoxicity, BPA has been listed as a priority pollutant for control. BPA is widely detected in aquatic environments, and conventional water treatment processes struggle to completely remove it. Therefore, developing efficient and economical BPA removal technologies is of significant environmental importance.

[0003] Adsorption methods are widely used due to their advantages such as simple operation, low cost, and no secondary pollution. Biochar adsorbents have attracted attention due to their large specific surface area, rich functional groups, and wide availability of raw materials. However, traditional biochar has limited adsorption capacity for BPA and its raw material cost is relatively high. On the other hand, lignin, as a major byproduct of the papermaking industry, has a huge annual output but low utilization rate; waste bleaching clay is a solid waste generated during oil refining, containing a large amount of residual organic matter and abundant inorganic mineral components. Co-pyrolyzing lignin and waste bleaching clay to produce clay-based biochar materials is an effective way to realize the resource utilization of waste.

[0004] Furthermore, the adsorption capacity and selectivity of existing adsorbents for BPA still need improvement, and the regeneration and resource recovery issues after adsorption saturation also urgently need to be addressed. Common adsorbents used for adsorbing bisphenol A (BPA) include carbon-based materials, natural minerals, polymers, and metal-organic frameworks (MOFs). Natural minerals and polymers have drawbacks such as uneven pore size distribution and limited adsorption capacity; the preparation process of MOFs is relatively complex and the synthesis cost is relatively high. Carbon-based materials, on the other hand, present problems such as separation difficulties and the risk of secondary pollution. Therefore, it is necessary to explore a novel adsorbent to address the problem of BPA pollution in aquatic environments. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a modified lignin / waste clay co-pyrolysis adsorbent. The adsorbent prepared by this method has excellent adsorption performance and good selectivity for bisphenol A in water. In addition, this invention also provides its application.

[0006] The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent of the present invention comprises the following steps: (1) Preparation of clay-based biochar Lignin and waste clay were mixed and placed in a tube furnace for co-pyrolysis under an inert atmosphere. After pyrolysis, the mixture was cooled to room temperature under an inert atmosphere to prepare clay-based biochar. (2) Preparation of iron-supported adsorbent The clay-based biochar prepared in step (1) was mixed with an iron salt solution for impregnation. After impregnation, the mixture was dried and pyrolyzed to prepare an iron-loaded adsorbent. (3) Preparation of modified lignin / waste clay co-pyrolysis adsorbent The iron-loaded adsorbent prepared in step (2) was placed in a nitric acid solution for oxidative modification. After modification, it was washed with deionized water until neutral and then dried to obtain a modified lignin / waste clay co-pyrolysis adsorbent.

[0007] Wherein: the lignin mentioned in step (1) is industrial lignin, the waste clay is a waste material in the oil refining process, and the mass ratio of lignin to waste clay is 1:1-3:1.

[0008] The inert atmosphere mentioned in step (1) is nitrogen, and the gas flow rate is 0.2-0.4 L / min.

[0009] The co-pyrolysis described in step (1) involves heating to 550-650℃ at a heating rate of 10-15℃ / min and holding at that temperature for 1-3 hours.

[0010] The cooling to room temperature mentioned in step (1) refers to cooling to room temperature with the furnace.

[0011] The iron salt mentioned in step (2) is one of FeCl3, Fe(NO3)3 or Fe2(SO4)3, and the concentration of the iron salt is 0.5-2.0 mol / L.

[0012] In step (2), the mass-volume ratio of clay-based biochar to iron salt solution is 0.05-0.5:1, with units of g / mL.

[0013] In step (2), the immersion reaction is carried out at room temperature for 12-24 hours.

[0014] The drying temperature in step (2) is 100-110℃ and the drying time is 10-14h.

[0015] The pyrolysis described in step (2) is performed in a tube furnace at 600-700℃ for 2-3 hours under a nitrogen atmosphere.

[0016] In step (2), the iron-loaded adsorbent is represented by the symbol Fe / C.

[0017] In step (3), the concentration of nitric acid solution is 0.5-2.0 mol / L, and the mass-volume ratio of iron-supported adsorbent to nitric acid solution is 0.02-0.2:1, with units of g / mL.

[0018] In step (3), the oxidation modification temperature is room temperature and the oxidation modification time is 2-8h.

[0019] In step (3), the drying temperature is 80-105℃ and the drying time is 10-14h.

[0020] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) has a surface carboxyl content of 0.20-0.35 mmol / g, a phenolic hydroxyl content of 0.70-1.00 mmol / g, and a mesoporous and macroporous pore volume of 60-68 cm³. 3 / g, the content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was determined by nitrogen adsorption-desorption characterization.

[0021] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) is represented by Fe / Ads-xN, where x is the nitric acid concentration (in mol / L), x = 0.5-2.0 mol / L, preferably x = 1, i.e. Fe / Ads-1N.

[0022] The application of the modified lignin / waste clay co-pyrolysis adsorbent of the present invention consists of the following steps: adding the modified lignin / waste clay co-pyrolysis adsorbent to a bisphenol A (BPA) solution for adsorption reaction, filtering after the reaction is complete, and pyrolyzing the saturated modified lignin / waste clay co-pyrolysis adsorbent for regeneration.

[0023] The dosage of the modified lignin / waste clay co-pyrolysis adsorbent in the bisphenol A solution is 0.5-5 g / L, the initial concentration of the bisphenol A solution is 10-200 mg / L, and water is used as the solvent.

[0024] The pH value of the adsorption reaction is 4-11, the temperature of the adsorption reaction is 15-35℃, and the time of the adsorption reaction is 12-24h.

[0025] The modified lignin / waste clay co-pyrolysis adsorbent has an adsorption capacity of 45-48 mg / g for bisphenol A in water.

[0026] The specific method for pyrolyzing and regenerating the saturated modified lignin / waste clay co-pyrolyzing adsorbent is as follows: the saturated modified lignin / waste clay co-pyrolyzing adsorbent is placed in a pyrolysis furnace, and under a nitrogen atmosphere, the gas flow rate is 0.1-0.5 L / min. The temperature is increased to 500-600℃ at a heating rate of 10-20℃ / min and held for 60-90 min for regeneration. Phenol is recovered from the regenerated liquid phase product, CH4 is recovered from the gas phase product, and the solid phase is the regenerated modified lignin / waste clay co-pyrolyzing adsorbent, which can be recycled.

[0027] In bisphenol A (BPA), the C-C bond connecting the two benzene rings undergoes homolytic cleavage upon heating, generating two phenoxy radicals (PhOH·) and one isopropenyl radical (IPP·). At higher temperatures (500-600℃), the IPP· radical is unstable and further cleaves to generate methane (CH4) and ethynyl radicals. Methane is the stable end product and accumulates in large quantities in the gas phase. Simultaneously, the phenoxy radical abstracts a hydrogen atom to form phenol.

[0028] Compared with the prior art, the present invention has the following advantages: (1) The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent of the present invention uses clay-based biochar prepared by co-pyrolysis of lignin and waste clay as the modified precursor raw material, realizing the high-value utilization of solid waste, avoiding the environmental burden of waste residue disposal, and reducing the production cost of adsorbent. Moreover, the porous structure formed during the initial carbonization process is conducive to improving the subsequent impregnation modification effect. Through the combined modification of iron loading and nitric acid oxidation, the content of oxygen-containing functional groups on the surface of the adsorbent is significantly increased. Nitric acid treatment also optimizes the pore structure and constructs a mesoporous-macroporous hierarchical pore structure, which is conducive to the diffusion and adsorption of BPA molecules.

[0029] (2) In the preparation method of the modified lignin / waste clay co-pyrolysis adsorbent described in this invention, the Fe3O4 introduced by iron loading is the core active site for electron transfer, and the nitric acid oxidation increases the oxygen-containing functional groups on the surface. The synergistic effect of the two significantly improves the adsorption performance. The adsorption capacity of Fe / Ads-1N modified with 1 mol / L nitric acid for BPA reached 47.5 mg / g (Example 1), which is higher than that of the original clay-based biochar (4.9 mg / g, Comparative Example 1) and the iron-loaded adsorbent without nitric acid modification (27.2 mg / g, Comparative Example 2).

[0030] (3) The modified lignin / waste clay co-pyrolysis adsorbent described in this invention is used for the adsorption of bisphenol A. The adsorption process follows a pseudo-second-order kinetic model and a Langmuir isotherm model, and belongs to endothermic spontaneous monolayer chemical adsorption (ΔH > 0, ΔG < 0). The modified lignin / waste clay co-pyrolysis adsorbent maintains a stable adsorption capacity in the pH range of 4-11, and is effective against common coexisting ions in water (Na+). + Ca 2+ NO3 - SO4 2- It exhibits good selectivity.

[0031] (4) The application of the modified lignin / waste clay co-pyrolysis adsorbent described in this invention also provides a pyrolysis regeneration method for the adsorbent after adsorption saturation. After three adsorption-pyrolysis regeneration cycles, Fe / Ads-1N still maintains an adsorption capacity of 40.8 mg / g (Example 1), exhibiting good recyclability. The liquid phase product from the pyrolysis regeneration contains 91.2% phenol (Example 1), and the gas phase product contains 83.0% CH4 (Example 1), achieving the recovery of phenol and methane-rich gas resources. Detailed Implementation

[0032] Example 1

[0033] The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 1 consists of the following steps: (1) Preparation of clay-based biochar Lignin and waste clay were mixed and placed in a tube furnace for co-pyrolysis under an inert atmosphere. After pyrolysis, the mixture was cooled to room temperature under an inert atmosphere to prepare clay-based biochar. (2) Preparation of iron-supported adsorbent The clay-based biochar prepared in step (1) was mixed with an iron salt solution for impregnation. After impregnation, the mixture was dried and pyrolyzed to prepare an iron-loaded adsorbent. (3) Preparation of modified lignin / waste clay co-pyrolysis adsorbent The iron-loaded adsorbent prepared in step (2) was placed in a nitric acid solution for oxidative modification. After modification, it was washed with deionized water until neutral and then dried to obtain a modified lignin / waste clay co-pyrolysis adsorbent.

[0034] Wherein: the lignin mentioned in step (1) is industrial lignin, the waste clay is a waste material in the oil refining process, and the mass ratio of lignin to waste clay is 2:1.

[0035] The inert atmosphere mentioned in step (1) is nitrogen, and the gas flow rate is 0.3 L / min.

[0036] The co-pyrolysis described in step (1) involves heating to 600°C at a heating rate of 12°C / min and holding at that temperature for 2 hours.

[0037] The cooling to room temperature mentioned in step (1) refers to cooling to room temperature with the furnace.

[0038] The iron salt mentioned in step (2) is FeCl3, and the concentration of the iron salt is 1.0 mol / L.

[0039] In step (2), the mass-to-volume ratio of the iron-supported adsorbent to the nitric acid solution is 0.1:1, with units of g / mL. The impregnation reaction temperature is room temperature, and the impregnation reaction time is 18h.

[0040] The drying temperature in step (2) is 105℃ and the drying time is 12h.

[0041] The pyrolysis described in step (2) is performed in a tube furnace at 700°C for 2 hours under a nitrogen atmosphere.

[0042] In step (2), the iron-loaded adsorbent is represented by the symbol Fe / C.

[0043] In step (3), the concentration of nitric acid solution is 1.0 mol / L, and the mass-volume ratio of iron-supported adsorbent to nitric acid solution is 0.05:1, with units of g / mL.

[0044] In step (3), the oxidation modification temperature is room temperature and the oxidation modification time is 4 hours.

[0045] In step (3), the drying temperature is 105℃ and the drying time is 10h.

[0046] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) has a surface carboxyl content of 0.31 mmol / g, a phenolic hydroxyl content of 0.96 mmol / g, and a mesoporous and macroporous pore volume of 68 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was determined by nitrogen adsorption-desorption characterization.

[0047] The application of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 1 consists of the following steps: adding the modified lignin / waste clay co-pyrolysis adsorbent to a bisphenol A (BPA) solution for adsorption reaction, filtering after the reaction is complete, and pyrolyzing the saturated modified lignin / waste clay co-pyrolysis adsorbent for regeneration.

[0048] The dosage of the modified lignin / waste clay co-pyrolysis adsorbent in the bisphenol A solution was 1 g / L, and the initial concentration of the bisphenol A solution was 50 mg / L.

[0049] The pH value of the adsorption reaction is 6, the temperature of the adsorption reaction is 25℃, and the time of the adsorption reaction is 16h.

[0050] The modified lignin / waste clay co-pyrolysis adsorbent Fe / Ads-1N has an adsorption capacity of 47.5 mg / g for bisphenol A in water and a BPA removal rate of 95%.

[0051] The specific method for pyrolytic regeneration of the saturated modified lignin / waste clay co-pyrolysis adsorbent is as follows: The saturated modified lignin / waste clay co-pyrolysis adsorbent is placed in a pyrolysis furnace under a nitrogen atmosphere at a gas flow rate of 0.3 L / min, and the temperature is increased to 600℃ at a rate of 10℃ / min and held for 60 min for regeneration. Phenol is recovered from the regenerated liquid phase product, with a phenol content of 91.2% in the liquid phase product. CH4 is recovered from the gas phase product, with a CH4 content of 83.0% in the gas phase product. The solid phase is the regenerated modified lignin / waste clay co-pyrolysis adsorbent. The regenerated adsorbent is used in the next round of adsorption experiments. After three cycles, the adsorption capacity is 40.8 mg / g, and the retention rate is 85.9%. The phenol content in the liquid phase product is determined by gas chromatography-mass spectrometry, and the CH4 content in the gas phase product is determined by a portable gas chromatograph.

[0052] In addition, Fe / Ads-0.5N (0.5M nitric acid) and Fe / Ads-2N (2M nitric acid) were prepared according to the method in Example 1, and adsorption tests were performed under the same conditions. The adsorption capacity of Fe / Ads-0.5N was 43.8 mg / g, Fe / Ads-1N was 47.5 mg / g, and Fe / Ads-2N was 40.1 mg / g. The results indicate that the combined modification with 1M nitric acid has the best effect.

[0053] Adsorption tests were conducted using Fe / Ads-1.0N at pH 3, 4, 5, 6, 7, 8, 9, 10, and 11 (initial BPA concentration 50 mg / L). The results showed that the adsorption capacity remained stable within the pH range of 4-11 (44.1 mg / g, 46.5 mg / g, 47.5 mg / g, 47.4 mg / g, 47.0 mg / g, 47.1 mg / g, 45.2 mg / g, and 44.6 mg / g, respectively), while the adsorption capacity decreased to 32.5 mg / g at pH 3.

[0054] Using Fe / Ads-1.0N, in the presence of Na + Ca 2+ NO3 - SO4 2-Adsorption tests were conducted in BPA solutions (50 mg / L) with a concentration of 10 mM. The results showed that coexisting ions had little effect on the adsorption capacity (46.1 mg / g, 43.2 mg / g, 45.1 mg / g, and 44.7 mg / g, respectively, with retention rates >90%). However, in 10 mM HCO3... - In its presence, the adsorption capacity decreased by approximately 35% from 31.0 mg / g; in the presence of 10 mg / L humic acid, the adsorption capacity decreased by approximately 49% from 24.1 mg / g. Example 2

[0055] The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 2 consists of the following steps: (1) Preparation of clay-based biochar Lignin and waste clay were mixed and placed in a tube furnace for co-pyrolysis under an inert atmosphere. After pyrolysis, the mixture was cooled to room temperature under an inert atmosphere to prepare clay-based biochar. (2) Preparation of iron-supported adsorbent The clay-based biochar prepared in step (1) was mixed with an iron salt solution for impregnation. After impregnation, the mixture was dried and pyrolyzed to prepare an iron-loaded adsorbent. (3) Preparation of modified lignin / waste clay co-pyrolysis adsorbent The iron-loaded adsorbent prepared in step (2) was placed in a nitric acid solution for oxidative modification. After modification, it was washed with deionized water until neutral and then dried to obtain a modified lignin / waste clay co-pyrolysis adsorbent.

[0056] Wherein: the lignin mentioned in step (1) is industrial lignin, the waste clay is a waste material in the oil refining process, and the mass ratio of lignin to waste clay is 1:1.

[0057] The inert atmosphere mentioned in step (1) is nitrogen, and the gas flow rate is 0.2 L / min.

[0058] The co-pyrolysis in step (1) involves heating to 550°C at a heating rate of 10°C / min and holding at that temperature for 3 hours.

[0059] The cooling to room temperature mentioned in step (1) refers to cooling to room temperature with the furnace.

[0060] The iron salt mentioned in step (2) is Fe(NO3)3, and the concentration of the iron salt is 2.0 mol / L.

[0061] In step (2), the mass-volume ratio of clay-based biochar to iron salt solution is 0.5:1, with units of g / mL.

[0062] In step (2), the impregnation reaction is carried out at room temperature for 24 hours.

[0063] The drying temperature in step (2) is 100℃ and the drying time is 14h.

[0064] The pyrolysis described in step (2) is performed in a tube furnace at 600°C for 3 hours under a nitrogen atmosphere.

[0065] In step (2), the iron-loaded adsorbent is represented by the symbol Fe / C.

[0066] In step (3), the concentration of nitric acid solution is 0.5 mol / L, and the mass-volume ratio of iron-supported adsorbent to nitric acid solution is 0.02:1, with units of g / mL.

[0067] In step (3), the oxidation modification temperature is room temperature and the oxidation modification time is 2 hours.

[0068] In step (3), the drying temperature is 80℃ and the drying time is 14h.

[0069] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) has a surface carboxyl content of 0.21 mmol / g, a phenolic hydroxyl content of 0.72 mmol / g, and a mesoporous and macroporous pore volume of 65 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was determined by nitrogen adsorption-desorption characterization.

[0070] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) is represented by Fe / Ads-xN, where x is the nitric acid concentration (in mol / L), x = 0.5 mol / L.

[0071] The application of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 2 consists of the following steps: adding the modified lignin / waste clay co-pyrolysis adsorbent to a bisphenol A (BPA) solution for adsorption reaction, filtering after the reaction is complete, and pyrolyzing the saturated modified lignin / waste clay co-pyrolysis adsorbent for regeneration.

[0072] The dosage of the modified lignin / waste clay co-pyrolysis adsorbent in the bisphenol A solution was 5 g / L, and the initial concentration of the bisphenol A solution was 200 mg / L.

[0073] The pH value of the adsorption reaction is 7, the temperature of the adsorption reaction is 15℃, and the time of the adsorption reaction is 24h.

[0074] The modified lignin / waste clay co-pyrolysis adsorbent has an adsorption capacity of 46.2 mg / g for bisphenol A in water and a BPA removal rate of approximately 92%.

[0075] The specific method for pyrolytic regeneration of the saturated modified lignin / waste clay co-pyrolysis adsorbent is as follows: The saturated modified lignin / waste clay co-pyrolysis adsorbent is placed in a pyrolysis furnace under an inert atmosphere at a gas flow rate of 0.1 L / min, and the temperature is increased to 550℃ at a heating rate of 20℃ / min and held for 75 min for regeneration. Phenol is recovered from the regenerated liquid phase product, with a phenol content of 90.8% in the liquid phase product. CH4 is recovered from the gas phase product, with a CH4 content of 80.9% in the gas phase product. The solid phase is the regenerated modified lignin / waste clay co-pyrolysis adsorbent, which can be recycled. After three cycles, the adsorption capacity is 38.8 mg / g, and the retention rate is 84.0%. The phenol content in the liquid phase product is determined by gas chromatography-mass spectrometry, and the CH4 content in the gas phase product is determined by a portable gas chromatograph. Example 3

[0076] The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 3 consists of the following steps: (1) Preparation of clay-based biochar Lignin and waste clay were mixed and placed in a tube furnace for co-pyrolysis under an inert atmosphere. After pyrolysis, the mixture was cooled to room temperature under an inert atmosphere to prepare clay-based biochar. (2) Preparation of iron-supported adsorbent The clay-based biochar prepared in step (1) was mixed with an iron salt solution for impregnation. After impregnation, the mixture was dried and pyrolyzed to prepare an iron-loaded adsorbent. (3) Preparation of modified lignin / waste clay co-pyrolysis adsorbent The iron-loaded adsorbent prepared in step (2) was placed in a nitric acid solution for oxidative modification. After modification, it was washed with deionized water until neutral and then dried to obtain a modified lignin / waste clay co-pyrolysis adsorbent.

[0077] Wherein: the lignin mentioned in step (1) is industrial lignin, the waste clay is a waste material in the oil refining process, and the mass ratio of lignin to waste clay is 3:1.

[0078] The inert atmosphere mentioned in step (1) is nitrogen, and the gas flow rate is 0.4 L / min.

[0079] The co-pyrolysis in step (1) involves heating to 650°C at a heating rate of 15°C / min and holding at that temperature for 1 hour.

[0080] The cooling to room temperature mentioned in step (1) refers to cooling to room temperature with the furnace.

[0081] The iron salt mentioned in step (2) is Fe2(SO4)3, and the concentration of the iron salt is 0.5 mol / L.

[0082] In step (2), the mass-volume ratio of clay-based biochar to iron salt solution is 0.05:1, with units of g / mL.

[0083] In step (2), the immersion reaction is carried out at room temperature for 12 hours.

[0084] The drying temperature in step (2) is 110℃ and the drying time is 10h.

[0085] The pyrolysis described in step (2) is performed in a tube furnace at 650°C for 2.5 h under a nitrogen atmosphere.

[0086] In step (2), the iron-loaded adsorbent is represented by the symbol Fe / C.

[0087] In step (3), the concentration of nitric acid solution is 2.0 mol / L, and the mass-volume ratio of iron-supported adsorbent to nitric acid solution is 0.2:1, with units of g / mL.

[0088] In step (3), the oxidation modification temperature is room temperature and the oxidation modification time is 8 hours.

[0089] In step (3), the drying temperature is 105℃ and the drying time is 10h.

[0090] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) has a surface carboxyl content of 0.35 mmol / g, a phenolic hydroxyl content of 0.98 mmol / g, and a mesoporous and macroporous pore volume of 60 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was determined by nitrogen adsorption-desorption characterization.

[0091] The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) is represented by Fe / Ads-xN, where x is the nitric acid concentration (in mol / L), x = 2.0 mol / L.

[0092] The application of the modified lignin / waste clay co-pyrolysis adsorbent described in Example 3 consists of the following steps: adding the modified lignin / waste clay co-pyrolysis adsorbent to a bisphenol A (BPA) solution for adsorption reaction, filtering after the reaction is complete, and pyrolyzing the saturated modified lignin / waste clay co-pyrolysis adsorbent for regeneration.

[0093] The dosage of the modified lignin / waste clay co-pyrolysis adsorbent in the bisphenol A solution was 0.5 g / L, and the initial concentration of the bisphenol A solution was 10 mg / L.

[0094] The pH value of the adsorption reaction is 7, the temperature of the adsorption reaction is 35℃, and the time of the adsorption reaction is 12h.

[0095] The modified lignin / waste clay co-pyrolysis adsorbent has an adsorption capacity of 45.0 mg / g for bisphenol A in water and a BPA removal rate of approximately 90.4%.

[0096] The specific method for pyrolytic regeneration of the saturated modified lignin / waste clay co-pyrolysis adsorbent is as follows: The saturated modified lignin / waste clay co-pyrolysis adsorbent is placed in a pyrolysis furnace under an inert atmosphere at a gas flow rate of 0.5 L / min, and the temperature is increased to 500℃ at a rate of 10℃ / min and held for 90 min for regeneration. Phenol is recovered from the regenerated liquid phase product, with a phenol content of 89.2% in the liquid phase product. CH4 is recovered from the gas phase product, with a CH4 content of 78.9% in the gas phase product. The solid phase is the regenerated modified lignin / waste clay co-pyrolysis adsorbent, which can be recycled. After three cycles, the adsorption capacity is 37.7 mg / g, and the retention rate is 83.8%.

[0097] Comparative Example 1 Comparative document 1 uses only step (1) of Example 1 to prepare clay-based biochar. The surface carboxyl content of the clay-based biochar is 0.09 mmol / g, the phenolic hydroxyl content is 0.35 mmol / g, and the mesoporous and macroporous pore volume is 3.5 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was characterized by nitrogen adsorption-desorption. The prepared clay-based biochar was then applied in the same manner as in Example 1. Testing showed that the clay-based biochar had an adsorption capacity of 4.9 mg / g for bisphenol A in water, with a BPA removal rate of 10%. Subsequently, the saturated clay-based biochar was pyrolyzed and regenerated in the same manner as in Example 1. Testing showed that the phenol content in the liquid phase product was 80.1%, CH4 was recovered in the gas phase product, and the CH4 content in the gas phase product was 70.7%. The solid phase was the regenerated modified lignin / waste clay co-pyrolysis adsorbent, which can be recycled. After three cycles, the adsorption capacity was 1.6 mg / g, with a retention rate of 32.7%. The phenol content in the liquid phase product was determined by gas chromatography-mass spectrometry, and the CH4 content in the gas phase product was determined by a portable gas chromatograph.

[0098] Comparative Example 2 The only difference between the adsorbent prepared in Comparative Example 2 and that in Example 1 is that step (3) is omitted, and only an iron-supported adsorbent is prepared. The iron-supported adsorbent has a surface carboxyl group content of 0.11 mmol / g, a phenolic hydroxyl group content of 0.40 mmol / g, and a mesopore and macropore volume of 34 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was characterized by nitrogen adsorption-desorption. The prepared iron-supported adsorbent was then applied in the same manner as in Example 1. The test showed that the iron-supported adsorbent had an adsorption capacity of 27.2 mg / g for bisphenol A in water, with a BPA removal rate of approximately 54.4%. Subsequently, the saturated iron-supported adsorbent was regenerated by pyrolysis in the same manner as in Example 1. The test showed that the phenol content in the liquid phase product was 85.8%, CH4 was recovered in the gas phase product, and the CH4 content in the gas phase product was 74.3%. The solid phase was the regenerated modified lignin / waste clay co-pyrolysis adsorbent, which can be recycled. After three cycles, the adsorption capacity was 16.4 mg / g, with a retention rate of 60.3%. The phenol content in the liquid phase product was determined by gas chromatography-mass spectrometry, and the CH4 content in the gas phase product was determined by a portable gas chromatograph.

[0099] Comparative Example 3 The adsorbent prepared in Comparative Example 3 differs from that in Example 1 in that step (1) of Example 1 is omitted (2), and step (3) is directly performed, i.e., the prepared clay-based biochar is directly subjected to nitric acid oxidation in step (3). The resulting adsorbent has a surface carboxyl content of 0.16 mmol / g, a phenolic hydroxyl content of 0.55 mmol / g, and a mesopore and macropore volume of 18 cm³. 3 / g. The content of carboxyl and phenolic hydroxyl groups was determined by Boehm titration, and the pore volume was characterized by nitrogen adsorption-desorption. The prepared adsorbent was then applied under the same conditions as in Example 1. The adsorbent showed an adsorption capacity of 15.3 mg / g for bisphenol A in water, with a BPA removal rate of approximately 30.6%. Subsequently, the saturated nitric acid oxidative adsorbent was regenerated by pyrolysis in the same manner as in Example 1. The liquid phase product contained 82.1% phenol, and CH4 was recovered from the gas phase product, with a CH4 content of 71.5%. The solid phase was the regenerated modified lignin / waste clay co-pyrolysis adsorbent, which can be recycled. After three cycles, the adsorption capacity was 6.5 mg / g, with a retention rate of 42.5%. The phenol content in the liquid phase product was determined by gas chromatography-mass spectrometry, and the CH4 content in the gas phase product was determined by a portable gas chromatograph.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a modified lignin / waste clay co-pyrolysis adsorbent, characterized in that: It consists of the following steps: (1) Preparation of clay-based biochar Lignin and waste clay were mixed and placed in a tube furnace for co-pyrolysis under an inert atmosphere. After pyrolysis, the mixture was cooled to room temperature under an inert atmosphere to prepare clay-based biochar. (2) Preparation of iron-supported adsorbent The clay-based biochar prepared in step (1) was mixed with an iron salt solution for impregnation. After impregnation, the mixture was dried and pyrolyzed to prepare an iron-loaded adsorbent. (3) Preparation of modified lignin / waste clay co-pyrolysis adsorbent The iron-loaded adsorbent prepared in step (2) was placed in a nitric acid solution for oxidative modification. After modification, it was washed with deionized water until neutral and then dried to obtain a modified lignin / waste clay co-pyrolysis adsorbent.

2. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: The lignin mentioned in step (1) is industrial lignin, and the waste clay is a waste material in the oil refining process. The mass ratio of lignin to waste clay is 1:1-3:

1. The inert atmosphere mentioned in step (1) is nitrogen, and the gas flow rate is 0.2-0.4 L / min.

3. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: The co-pyrolysis described in step (1) involves heating to 550-650℃ at a heating rate of 10-15℃ / min and holding at that temperature for 1-3 hours. The cooling to room temperature mentioned in step (1) refers to cooling to room temperature with the furnace.

4. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: The iron salt mentioned in step (2) is one of FeCl3, Fe(NO3)3 or Fe2(SO4)3, and the concentration of the iron salt is 0.5-2.0 mol / L; In step (2), the mass-to-volume ratio of clay-based biochar to iron salt solution is 0.05-0.5:1, in g / mL. In step (2), the immersion reaction is carried out at room temperature for 12-24 hours.

5. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: The drying temperature in step (2) is 100-110℃, and the drying time is 10-14h; The pyrolysis described in step (2) is performed in a tube furnace at 600-700℃ for 2-3 hours under a nitrogen atmosphere.

6. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: In step (3), the concentration of nitric acid solution is 0.5-2.0 mol / L, and the mass-to-volume ratio of iron-supported adsorbent to nitric acid solution is 0.02-0.2:1, in g / mL. In step (3), the oxidation modification temperature is room temperature and the oxidation modification time is 2-8h.

7. The preparation method of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: In step (3), the drying temperature is 80-105℃ and the drying time is 10-14h; The modified lignin / waste clay co-pyrolysis adsorbent prepared in step (3) has a surface carboxyl content of 0.20-0.35 mmol / g, a phenolic hydroxyl content of 0.70-1.00 mmol / g, and a mesoporous and macroporous pore volume of 60-68 cm³. 3 / g.

8. The application of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 1, characterized in that: The process consists of the following steps: adding the modified lignin / waste clay co-pyrolysis adsorbent to a bisphenol A solution for adsorption reaction; filtering after the reaction is complete; and pyrolyzing the saturated modified lignin / waste clay co-pyrolysis adsorbent for regeneration.

9. The application of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 8, characterized in that: The dosage of the modified lignin / waste clay co-pyrolysis adsorbent in the bisphenol A solution is 0.5-5 g / L, the initial concentration of the bisphenol A solution is 10-200 mg / L, and water is used as the solvent. The pH value of the adsorption reaction is 4-11, the temperature of the adsorption reaction is 15-35℃, and the time of the adsorption reaction is 12-24h. The modified lignin / waste clay co-pyrolysis adsorbent has an adsorption capacity of 45-48 mg / g for bisphenol A in water.

10. The application of the modified lignin / waste clay co-pyrolysis adsorbent according to claim 8, characterized in that: The specific method for pyrolyzing and regenerating the saturated modified lignin / waste clay co-pyrolyzing adsorbent is as follows: the saturated modified lignin / waste clay co-pyrolyzing adsorbent is placed in a pyrolysis furnace, and under a nitrogen atmosphere, the gas flow rate is 0.1-0.5 L / min. The temperature is increased to 500-600℃ at a heating rate of 10-20℃ / min and held for 60-90 min for regeneration. Phenol is recovered from the regenerated liquid phase product, CH4 is recovered from the gas phase product, and the solid phase is the regenerated modified lignin / waste clay co-pyrolyzing adsorbent, which can be recycled.