A method for efficiently preparing high-catalytic-performance biochar based on pulping black liquor and application
By treating waste biomass with sodium hydroxide, sodium sulfide, and ferric chloride hexahydrate in pulping black liquor, sulfur-doped nano-zero-valent iron biochar with high catalytic performance was prepared, solving the problems of low lignin recovery rate and high treatment cost. This achieved efficient utilization of black liquor and high-value conversion of biochar, which can be applied to the catalytic degradation of antibiotic wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF GEOGRAPHY HENAN ACAD OF SCI
- Filing Date
- 2024-12-13
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods cannot simultaneously achieve efficient recovery of lignin from pulping black liquor and conversion into functional biochar. Traditional processes suffer from low lignin recovery rates and high processing costs.
Waste biomass was treated with a mixed solution of sodium hydroxide and sodium sulfide, followed by the addition of ferric chloride hexahydrate for reaction, freeze-drying, and high-temperature pyrolysis to prepare sulfur-doped nano-zero-valent iron biochar. Process parameters were optimized to improve lignin recovery rate and biochar catalytic performance.
The method achieves efficient recovery and high-value conversion of lignin in pulping black liquor. The prepared biochar exhibits excellent catalytic performance in water treatment, reducing environmental pollution and treatment costs, especially demonstrating high catalytic efficiency in the catalytic degradation of antibiotic wastewater.
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Figure CN119680579B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-value conversion and application of waste biomass, specifically involving a method and application for the efficient preparation of high-catalytic-performance biochar based on pulping black liquor. Background Technology
[0002] Waste biomass resources are abundant and contain high levels of lignocellulose, often used in the papermaking and pulping industry. Chemical methods, such as the sulfate and caustic soda processes, are among the most common papermaking and pulping techniques. However, these chemical pulping processes generate large quantities of black liquor as a byproduct. This black liquor, as biomass waste, is produced in large quantities and is difficult to degrade, posing significant challenges to plant treatment. It not only increases treatment costs but also causes environmental pollution. Research shows that chemical pulping black liquor contains a large amount of lignin. As is well known, lignin is a biomass energy source, a high-molecular-weight organic compound with excellent structural properties and high product value. Therefore, how to efficiently separate and recover lignin from black liquor to achieve harmless treatment and high-value conversion of pulping black liquor has become a key research focus.
[0003] Current research on the separation and extraction of lignin from black liquor primarily focuses on the purity of lignin extraction for the production of biomass energy and high-value-added fuel products. However, prioritizing lignin separation and purification can easily lead to low lignin recovery rates, while the cumbersome separation and extraction processes increase processing costs. Acid precipitation, as a traditional and mature method for separating lignin, is simple, but wastewater treatment after its implementation remains a challenge. Therefore, some studies have employed the co-precipitation of lignin with ferric chloride and sodium hydroxide, followed by one-step carbonization into nano-zero-valent iron biochar. This approach achieves lignin modification, capture, and high-value conversion without damaging lignin quality. However, while this method achieves efficient and convenient recovery of lignin from black liquor, the functionality of the resulting biochar remains insufficient and needs improvement. Summary of the Invention
[0004] The purpose of this invention is to solve the technical problem that existing methods cannot simultaneously achieve efficient recovery of lignin and conversion of biochar with excellent functionality from pulping black liquor, and to provide a method and application for efficient preparation of biochar with high catalytic performance based on pulping black liquor.
[0005] The technical solution of the present invention is as follows:
[0006] One objective of this invention is to provide a method for efficiently preparing high-catalytic-performance biochar based on pulping black liquor, the method comprising the following steps:
[0007] S1: Place the waste biomass in a mixed solution of sodium hydroxide and sodium sulfide and heat it at high temperature to separate the solid and liquid, thus obtaining black liquor;
[0008] S2: Add ferric chloride hexahydrate to black liquor, heat to react, centrifuge, freeze dry the precipitate, and then pyrolyze it at high temperature in a tube furnace to obtain sulfur-doped nano-zero-valent iron biochar.
[0009] Further specifying, the waste biomass in S1 is straw, wood, or livestock and poultry manure.
[0010] Further specified, the concentration of sodium hydroxide in the mixed solution in S1 is 0.5-1.5 mol / L.
[0011] Further specifying, the molar ratio of sodium hydroxide to sodium sulfide in S1 is (4-6):1.
[0012] Further specifying, the ratio of waste biomass to mixed solution in S1 is 1g:(15-25)mL.
[0013] Further specified, the high-temperature heating in S1 is at a temperature of 110-130℃ for 1.5-2.5 hours.
[0014] Further specifying, the concentration of ferric chloride hexahydrate in the black liquor of S2 is 0.40-0.5 mol / L.
[0015] Further specified, the heating temperature in S2 is 50-70℃, and the heating time is 0.5-1.5h.
[0016] Further specifying, the high-temperature pyrolysis temperature in S2 is 650-750℃, and the time is 1-3h.
[0017] The second objective of this invention is to provide an application of the above-mentioned method in the high-value conversion of pulping black liquor.
[0018] A third objective of this invention is to provide a biochar prepared by the above method.
[0019] The fourth objective of this invention is to provide an application of the biochar prepared by the above method in the field of water treatment.
[0020] The fifth objective of this invention is to provide a method for advanced oxidation treatment of antibiotic wastewater, wherein the method includes:
[0021] The above-mentioned sulfur-doped nano-zero-valent iron biochar catalytic oxidant was used to treat antibiotic wastewater at room temperature.
[0022] To further specify, antibiotics include sulfamethoxazole and sulfadiazine.
[0023] Further limits were set, with antibiotic concentrations in wastewater ranging from 5 to 15 mg / L.
[0024] Further specified, the oxidant includes persulfate, and the amount of oxidant used is 0.5-5 mmol / L.
[0025] The dosage of biochar is further specified as 0.35-0.45 g / L.
[0026] The advantages of this invention compared to existing technologies are:
[0027] This invention aims to prepare high-value products after separating and recovering lignin. It employs appropriate methods to precipitate lignin and endow it with product conversion potential, fully utilizing the sulfur element present in black liquor while introducing other metal elements. Furthermore, by optimizing process parameters, it obtains biochar with excellent functionality. Specific advantages are as follows:
[0028] (1) This invention provides an efficient method for recovering lignin from black liquor produced during the sulfate chemical pulping process. Compared with traditional methods, it has the advantages of simple operation steps and high recovery rate. This method can not only recover lignin, but also precipitate sulfur in black liquor at the same time. Furthermore, by optimizing the process parameters, the biochar produced by its high-value conversion contains both heteroatom sulfur and transition metal iron, giving the biochar better catalytic properties.
[0029] (2) This invention simultaneously achieves efficient recovery and high-value conversion of lignin in black liquor produced by chemical pulping. The treatment and utilization of black liquor reduces environmental pollution and greatly lowers the treatment cost of such difficult-to-biodegrade water bodies. The high-value biochar conversion of black liquor is applied to the catalytic degradation of sulfonamide antibiotic wastewater, embodying the ecological concept of treating waste with waste. Attached Figure Description
[0030] Figure 1 The concentration of residual lignin in the liquid after separating and precipitating lignin in Examples 1-2 and Comparative Examples 1-3; ↑ represents the proportion of increased extraction rate compared to Comparative Example 1;
[0031] Figure 2 The concentration of residual iron ions in the liquid after lignin precipitation in Examples 1-2 and Comparative Examples 2-3;
[0032] Figure 3 The yields of biochar prepared in Examples 1-2 and Comparative Examples 2-3 are shown.
[0033] Figure 4 Comparison of the chemical element content of biochar prepared in Examples 1-2 and Comparative Examples 1-3;
[0034] Figure 5 The X-ray diffraction (XRD) patterns of the biochar prepared in Examples 1-2 and Comparative Examples 2-3 are shown.
[0035] Figure 6 Here is a high-resolution transmission electron microscope (HRTEM) image of the biochar prepared in Example 2;
[0036] Figure 7 The X-ray diffraction (XRD) pattern of the biochar prepared in Comparative Example 4;
[0037] Figure 8 The X-ray diffraction (XRD) pattern of the biochar prepared in Comparative Example 5;
[0038] Figure 9 The graph shows the degradation behavior of sulfamethoxazole by different biochar-activated persulfate in the application examples;
[0039] Figure 10 The graph shows the degradation behavior of sulfadiazine by different biochar-activated persulfate in the application examples. Detailed Implementation
[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0042] Example 1:
[0043] This embodiment describes a method for efficiently preparing high-catalytic-performance biochar from pulping black liquor, which is carried out according to the following steps:
[0044] (1) Add 5g of corn stalks (40-100 mesh) to 100mL of a mixed solution of sodium hydroxide (1mol / L) and sodium sulfide nonahydrate (0.2mol / L). Heat in a constant-temperature oil bath at 120℃ for 2 hours under normal pressure. After vacuum filtration and solid-liquid separation, obtain the pulping black liquor stock. Record the lignin concentration in this black liquor stock as 100% (see attached). Figure 1 (shown) as a control for the efficiency of later lignin precipitation.
[0045] (2) Take 20 mL of the pulping black liquor stock solution obtained in step (1), add ferric chloride hexahydrate to it according to the concentration of ferric chloride hexahydrate in the black liquor of 0.40 mol / L, react at 60℃ for 60 min, and keep the supernatant obtained by the first centrifugation after the reaction, and record it as 0.40F. The precipitate after the first centrifugation is washed and centrifuged three more times, and then freeze-dried as the raw material for the subsequent preparation of biochar.
[0046] (3) The precipitate obtained in step (2) was pyrolyzed at 700°C for 2 hours in a tube furnace and then naturally cooled to room temperature to obtain sulfur-doped iron-based biochar, denoted as 0.40FLC.
[0047] Example 2:
[0048] The difference between this embodiment and Example 1 is that: in step (2), the concentration of ferric chloride hexahydrate in the black liquor is 0.46 mol / L, and the supernatant obtained after the first centrifugation after the reaction is retained and recorded as 0.46F. The biochar obtained in step (3) is recorded as 0.46FLC. Other steps and parameters are the same as in Example 1.
[0049] Comparative Example 1:
[0050] The difference between this comparative example and Example 1 is that in step (1), lignin is recovered by precipitation using the traditional method of adding hydrochloric acid. Specifically, hydrochloric acid solution is used instead of the sodium hydroxide / sodium sulfide nonahydrate mixed solution. The pH is adjusted to 1.8 by adding hydrochloric acid solution. After the precipitate is freeze-dried, step (3) is carried out directly. The biochar obtained is denoted as LC. Other steps and parameters are the same as in Example 1.
[0051] Comparative Example 2:
[0052] The difference between this comparative example and Example 1 is that: in step (2), the concentration of ferric chloride hexahydrate added is 0.55 mol / L, and the supernatant obtained after the first centrifugation after the reaction is recorded as 0.55F. The biochar obtained in step (3) is recorded as 0.55FLC. Other steps and parameters are the same as in Example 1.
[0053] Comparative Example 3:
[0054] The difference between this comparative example and Example 1 is that: in step (2), the concentration of ferric chloride hexahydrate added is 0.65 mol / L, and the supernatant obtained after the first centrifugation after the reaction is recorded as 0.65F. The biochar obtained in step (3) is recorded as 0.65FLC. Other steps and parameters are the same as in Example 1.
[0055] Comparative Example 4:
[0056] (1) Mix 5g of corn stalks (40-100 mesh) with 100mL of 2wt% hydroxide solution, heat in an oil bath at 75℃ for 120min, and then separate the solid and liquid by vacuum filtration. The resulting liquid is the biomass black liquor.
[0057] (2) Add ferric chloride hexahydrate to the biomass black liquor obtained in step (1). The ratio of biomass black liquor to ferric chloride hexahydrate is 20 mL: 1 g. Heat the mixture at 60 °C for 60 min. Centrifuge to obtain the precipitate. Wash the precipitate three times with ultrapure water. Dry the precipitate to constant weight to obtain biochar precursor.
[0058] (3) The biochar precursor obtained in step (2) is placed in a tube furnace and heated to 700°C at 5°C / min in a nitrogen atmosphere. It is then carbonized at this temperature for 2 hours and naturally cooled to room temperature to obtain nano-zero valent iron biochar.
[0059] (4) The nano-zero-valent iron biochar was soaked in a sodium sulfide solution with a concentration of 0.2 mol / L, heated at 60°C for 60 min, centrifuged to obtain the precipitate, and dried to constant weight to obtain sulfur-doped nano-zero-valent iron biochar, denoted as FCS.
[0060] Comparative Example 5:
[0061] (1) Add 5g of corn stalks (40-100 mesh) to 100mL of sodium hydroxide solution with a concentration of 1mol / L, heat in a constant temperature oil bath at 120℃ for 2h under normal pressure, and obtain the pulping black liquor stock solution after vacuum filtration and solid-liquid separation.
[0062] (2) Take 20 mL of the pulping black liquor stock solution obtained in step (1), add ferric chloride hexahydrate to it, the concentration of ferric chloride hexahydrate added is 0.46 mol / L, react at 60℃ for 60 min, the precipitate after centrifugation is washed and centrifuged three times, and then freeze-dried as the raw material for the preparation of subsequent biochar.
[0063] (3) The biochar precursor obtained in step (2) was soaked in a sodium sulfide nonahydrate solution with a concentration of 0.2 mol / L, heated at 60°C for 60 min, centrifuged to obtain the precipitate, washed the precipitate three times with ultrapure water, and dried the precipitate to constant weight to obtain sulfur-doped biochar precursor.
[0064] (4) The precipitate obtained in step (3) is pyrolyzed at 700°C for 2 hours in a tube furnace and then naturally cooled to room temperature to obtain sulfur-doped iron-based biochar, denoted as FSC.
[0065] The residual lignin and residual iron ion concentrations of the supernatants obtained from the first centrifugation in Examples 1-2 and Comparative Examples 1-3 were measured at 0.40F, 0.46F, 0.55F, and 0.65F, respectively. The results are shown in Figures 1 and 2. Figure 2 As shown. (Attached) Figure 1The results show that as the concentration of ferric chloride added increases, the remaining lignin gradually decreases, and all concentrations are lower than those remaining after conventional acid precipitation (Comparative Example 1). Compared with the conventional method, the lignin removal rates are increased by 10.9%, 64.43%, 78.48%, and 88.29%, respectively. These results demonstrate that the method of the present invention has highly efficient lignin recovery characteristics. (Appendix) Figure 2 The results showed that the added ferric chloride reacted with the original solution and formed a precipitate. The concentration of residual iron ions in the liquid after precipitation was much lower than the initial concentration of iron ions added. The utilization rates of ferric chloride in the residual liquids of 0.40F and 0.46F were as high as 99.55% and 97.02%, respectively.
[0066] The yields of the four types of biochar prepared in Examples 1-2 and Comparative Examples 2-3 were tested, and the results are as follows: Figure 3 As shown in the attached figure, the yields of the four types of biochar were 65.45%, 71.82%, 68.93%, and 61.82%, respectively. The biochar raw material with the highest yield came from the precipitate obtained by adding 0.46 mol / L ferric chloride.
[0067] XPS analysis was performed on the chemical elemental composition of the biochar prepared in Examples 1-2 and Comparative Examples 1-3, and the results are as follows: Figure 4 As shown in the attached figure, compared with biochar prepared from lignin extracted in the traditional method, the carbon content at 0.40 FLC, 0.46 FLC, 0.55 FLC, and 0.65 FLC is significantly increased, rising from 36.69% to 49.23%, 66.71%, 66.65%, and 66.95%, respectively. This high carbon content undoubtedly originates from the sedimentation of lignin in the original solution. This result further confirms the claim that the method of this invention achieves a higher lignin recovery rate. Meanwhile, the iron content at 0.46 FLC is 8.11%, not significantly different from that at 0.55 FLC and 0.65 FLC, combined with… Figure 2 and Figure 3 Analysis of the results indicates that a ferric chloride dosage of 0.46 mol / L is the optimal condition for lignin recovery and biochar preparation.
[0068] The phase composition of the four types of biochar prepared in Examples 1-2 and Comparative Examples 2-3 was further determined by XRD analysis. Figure 5 As shown in the attached figure, 0.40FLC, 0.46FLC, 0.55FLC and 0.65FLC all contain two phases, FeS and Fe2(SiO4). In addition, zero-valent iron was detected in 0.40FLC and 0.46FLC.
[0069] Based on the above results, it can be confirmed that 0.46 mol / L is the optimal iron ion concentration for lignin recovery, and 0.46 FLC is the optimal sulfur-doped zero-valent iron biochar prepared by the method of this invention. High-resolution TEM testing of the 0.46 FLC obtained in Example 2 confirmed that the zero-valent iron particles are nanoscale. Based on these results, the feasibility of the present invention in the efficient recovery of lignin to prepare sulfur-doped nano-zero-valent iron biochar is confirmed.
[0070] XRD tests were performed on the biochar obtained from Comparative Example 4 and Comparative Example 5, respectively, and the results are as follows: Figure 7 and Figure 8 As shown. (Attached) Figure 7 The results showed that when biomass black liquor treated with sodium hydroxide was first precipitated with ferric chloride to produce biochar, subsequent soaking in sodium sulfide yielded only biochar dominated by zero-valent iron phase. Furthermore, XPS analysis revealed a chemical composition of C (68.92%), O (21.23%), Fe (8.78%), and S (1.07%), confirming that sulfur was loaded onto the biochar, but could not be present in crystalline form on the material surface. (Appendix) Figure 8 The results show that the black liquor obtained by first treating it with sodium hydroxide, then precipitating it with ferric chloride, and then soaking the dried precipitate in sodium sulfide again, resulted in biochar of the dried body after carbonization. The main phase of the biochar was iron tetroxide. Although zero-valent iron, ferrous sulfide and ferrous disulfide phases appeared, its strength was obviously insufficient compared with Examples 1-2.
[0071] Application example: The steps of the method for catalyzing the degradation of sulfonamide antibiotics by persulfate using six types of biochar prepared in Examples 1-2 and Comparative Examples 2-5 are as follows:
[0072] Six types of sulfur-doped iron-based biochar obtained in Examples 1-2 and Comparative Examples 2-5 (0.4 g / L) were used to construct two catalytic degradation systems with 1 mmol / L potassium persulfate and 10 mg / L sulfamethoxazole and sulfadiazine, respectively. The residual concentrations of sulfamethoxazole and sulfadiazine were measured at certain time intervals to determine the catalytic activity of the biochar.
[0073] like Figure 9 As shown, the results indicate that with the participation of 0.40 FLC, 0.46 FLC, 0.55 FLC, 0.65 FLC, FCS, and FSC, the degradation efficiencies of sulfamethoxazole at 1 min were 66.84%, 71.00%, 74.52%, 79.03%, 23.09%, and 29.70%, respectively, and the final degradation efficiencies at 60 min were 95.04%, 95.81%, 95.72%, 96.71%, 62.71%, and 70.67%, respectively. Furthermore, as... Figure 10As shown, with the participation of 0.40 FLC, 0.46 FLC, 0.55 FLC, 0.65 FLC, FCS, and FSC, the degradation efficiencies of sulfadiazine reached 75.31%, 80.15%, 82.20%, 84.97%, 20.29%, and 28.08% at 1 min, respectively. The final degradation efficiencies at 60 min were 99.77%, 99.59%, 99.30%, 99.36%, 77.94%, and 86.91%, respectively. Based on these results, it is demonstrated that the four types of biochar of this invention exhibit highly efficient catalytic degradation capabilities for two antibiotics in an advanced oxidation system with potassium persulfate. A comprehensive comparison with the degradation results of the comparative examples consistently demonstrates that the biochar obtained by the method of this invention has excellent catalytic performance and can be applied in the field of water treatment.
[0074] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for efficiently preparing high-catalytic-performance biochar based on pulping black liquor, characterized in that, The method described: S1: Place the waste biomass in a mixed solution of sodium hydroxide and sodium sulfide and heat it at high temperature to separate the solid and liquid, thus obtaining black liquor; S2: Add ferric chloride hexahydrate to black liquor, heat to react, centrifuge and freeze-dry the precipitate, then pyrolyze it at high temperature in a tube furnace to obtain sulfur-doped nano-zero-valent iron biochar. The molar ratio of sodium hydroxide to sodium sulfide in S1 is (4-6):1, and the high-temperature heating temperature is 110-130℃; The concentration of ferric chloride hexahydrate in the black liquor of S2 is 0.4-0.5 mol / L.
2. The method according to claim 1, characterized in that, The waste biomass in S1 is straw, wood or livestock manure, the sodium hydroxide concentration in the mixed solution is 0.5-1.5 mol / L, and the ratio of waste biomass to mixed solution is 1 g: (15-25) mL.
3. The method according to claim 1, characterized in that, The high-temperature heating time in S1 is 1.5-2.5 hours.
4. The method according to claim 1, characterized in that, The heating temperature in S2 is 50-70℃ for 0.5-1.5h, and the high-temperature pyrolysis temperature is 650-750℃ for 1-3h.
5. The application of the method according to any one of claims 1-4 in the high-value conversion of black liquor from sulfate pulping.
6. The sulfur-doped nano-zero-valent iron biochar prepared by the method according to any one of claims 1-4.
7. The application of the sulfur-doped nano-zero-valent iron biochar according to claim 6 in the field of water treatment.
8. The method for catalytic degradation of antibiotic wastewater using biochar as described in claim 6, characterized in that, The method described: Sulfur-doped nano-zero-valent iron and persulfate were added to antibiotic wastewater and treated at room temperature.
9. The method according to claim 8, characterized in that, Antibiotics include sulfamethoxazole and sulfadiazine. The concentration of antibiotics in wastewater is 5-15 mg / L, and the amount of biochar added is 0.35-0.45 g / L.