Biomass-based electro-adsorption electrode material for heavy metal wastewater treatment as well as preparation method and application of biomass-based electro-adsorption electrode material
Biomass-based electroadsorption electrode materials were prepared by pretreatment with sodium sulfite and N/P co-doping, which solved the problems of incomplete lignin removal and low electrode specific capacity in the existing technology, and achieved efficient and low-consumption treatment of heavy metal wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-10
AI Technical Summary
Existing biomass-based electroadsorption electrode materials suffer from incomplete lignin removal or poor modification effects due to unreasonable pretreatment processes, unreasonable N/P co-doping process parameters, low electrode specific capacity, and poor heavy metal adsorption performance, which limits their application in heavy metal wastewater treatment.
Sodium sulfite was used to pretreat wheat straw to remove lignin, and it was co-doped with NH4H2PO4. The N/P co-doped porous carbon active material was formed by high-temperature pyrolysis, and the biomass-based electroadsorption electrode material was prepared and coated on the surface of carbon cloth to form an electrode.
It significantly improves the specific capacity and heavy metal adsorption performance of the electrode, reduces energy consumption, is suitable for large-scale production, and is applicable to distributed heavy metal wastewater treatment.
Smart Images
Figure CN121823749A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, specifically relating to a biomass-based electroadsorption electrode material for treating heavy metal wastewater, its preparation method, and its application. Background Technology
[0002] With rapid industrial development, industries such as mining, electroplating, metallurgy, electronics manufacturing, and medical treatment are increasingly discharging heavy metal wastewater, including Ag. + Cu 2+ Ni 2+ Pb 2+ Cd 2+ Cr 6+ Heavy metal ions are non-biodegradable and easily accumulate in the environment over a long period of time. They can also harm human health through the food chain amplification effect, causing serious problems such as liver and kidney damage, cancer, and mutation.
[0003] Existing heavy metal wastewater treatment technologies have significant drawbacks: chemical precipitation, while simple, generates large amounts of sludge that can easily cause secondary pollution; activated carbon adsorption is low-cost, but requires thermal regeneration after adsorption saturation and has poor selectivity for heavy metals; ion exchange produces high-quality effluent and recovers metals, but the resin is prone to poisoning and regeneration costs are high; electrolysis can recover metals, but the electrodes are prone to passivation and energy consumption is as high as 1.5–4.5 kWh·kg⁻¹. -1 Metals; membrane separation methods offer high separation precision, but are prone to membrane fouling, consume a lot of energy, and are difficult to dispose of the concentrate.
[0004] Electroadsorption, as a novel and efficient treatment technology, achieves electrostatic adsorption of heavy metal ions by forming an electric double layer at the electrode / solution interface through the application of a low-voltage DC voltage of 0.8-1.4 V. Furthermore, it can be reduced in situ (e.g., Ag). 0 Cu 0 This achieves integrated "adsorption-recovery" with energy consumption only 1 / 3 that of electrolysis (0.5-1.5 kWh·kg⁻¹). -1 Lignin removal is significantly advantageous when using biomass as a raw material. However, existing electroadsorption electrode materials still have shortcomings: when using biomass as a raw material, unreasonable pretreatment processes lead to incomplete lignin removal or poor modification effects, resulting in insufficient material specific surface area and active sites; the introduction of doping elements (such as N, P, S) is limited by a single method, making it difficult to form synergistic adsorption sites and limiting the improvement of selectivity for heavy metals; the electrode specific capacity is generally lower than 80 F / g, and the electroadsorption capacity and cycle stability are poor, restricting industrial applications.
[0005] Therefore, developing a method for preparing high-performance electroadsorption electrode materials with controllable microstructure by using low-cost biomass (such as wheat straw) as raw material and optimizing pretreatment and doping processes has become the key to solving the problem of heavy metal wastewater treatment. Summary of the Invention
[0006] To overcome the shortcomings of existing biomass-based electroadsorption electrode materials, such as poor pretreatment effect (incomplete lignin removal or insufficient modification), unreasonable N / P co-doping process parameters, low electrode specific capacity, and poor heavy metal adsorption performance, the primary objective of this invention is to provide a method for preparing biomass-based electroadsorption electrode materials for heavy metal wastewater treatment, thereby achieving precise control of electrode microstructure and electrochemical performance.
[0007] Another object of the present invention is to provide a biomass-based electroadsorption electrode material for treating heavy metal wastewater prepared by the above method.
[0008] Another object of the present invention is to provide the application of the above-mentioned biomass-based electroadsorption electrode material for heavy metal wastewater treatment.
[0009] The present invention also provides a heavy metal wastewater treatment device.
[0010] The objective of this invention is achieved through the following technical solution: A method for preparing a biomass-based electroadsorption electrode material for treating heavy metal wastewater includes the following steps: (I) Straw pretreatment: Chop the wheat straw and then add Na2SO3 solution for cooking to obtain delignified wheat straw fiber; (II) Drying and grinding: The wheat straw fiber obtained in step (I) is dried, ground, and then sieved to obtain straw powder; (III) N / P co-doped pyrolysis: After the straw powder and NH4H2PO4 are mixed evenly, they are pyrolyzed at high temperature under an inert protective atmosphere and then naturally cooled to obtain N / P co-doped porous carbon active material. (IV) Electrode preparation: N / P co-doped porous carbon active material, conductive agent and binder are mixed and homogenized to form a slurry. The slurry is then coated on the surface of carbon cloth and dried to obtain the biomass-based electroadsorption electrode material for heavy metal wastewater treatment.
[0011] Preferably, the steaming in step (I) is carried out at 120-180 ℃ for 2 h, the wheat straw is chopped into 2-3 cm pieces, the mass concentration of the Na2SO3 solution is 10-16%, and the solid-liquid ratio of the Na2SO3 solution to the wheat straw is 1:5-1:10 g / mL.
[0012] More preferably, the cooking in step (I) is performed at 165 °C for 2 h, the mass concentration of the Na2SO3 solution is 15%, and the solid-liquid ratio of the Na2SO3 solution to the wheat straw is 1:5 g / mL.
[0013] Preferably, in step (II), the drying is carried out at 60-80 ℃ for about 10 h until constant weight is achieved, and the sieving is carried out through a 100-mesh sieve.
[0014] Preferably, in step (III), the mass ratio of straw powder to NH4H2PO4 is 1:0.2-1, more preferably 1:0.5.
[0015] Preferably, in step (III), the inert protective atmosphere is N2 or Ar, and the flow rate is 50-200 mL / min.
[0016] Preferably, the high-temperature pyrolysis in step (III) is carried out at 800-900 °C and held for 2 h. More preferably, the temperature is increased at a rate of 5 °C / min.
[0017] Preferably, in step (IV), the mass ratio of the N / P co-doped porous carbon active material, the conductive agent, and the binder is 7:2:1 or 8:1:1.
[0018] Preferably, in step (IV), when the N / P co-doped porous carbon active material, conductive agent and binder are mixed, N-methylpyrrolidone is added as a solvent, and the ratio of the N / P co-doped porous carbon active material, conductive agent and binder mixture to N-methylpyrrolidone is 15:1 mg / mL. The homogenization refers to homogenizing with a homogenizer for ≥30 min to form a slurry.
[0019] Preferably, in step (IV), the conductive agent is carbon black and the binder is polyvinylidene fluoride (PVDF).
[0020] Preferably, in step (IV), the slurry is coated onto the surface of the carbon cloth with a brush and then pressed and scraped evenly with a glass slide, with a coating thickness of about 1 mm.
[0021] Preferably, in step (IV), the drying is performed under vacuum at 80 °C for 12 h.
[0022] An electroadsorption electrode material for treating heavy metal wastewater is prepared by the above-described method. This electrode material has a specific capacity ≥75 F / g and exhibits high specific gravity for Cu. 2+ Pb 2+ Cd 2+ The adsorption capacity is ≥150 mg / g, and the capacitance retention rate is ≥74% at a current density of 10 A / g.
[0023] The aforementioned electroadsorption electrode material can be used to treat wastewater containing heavy metals, including Cu. 2+ Pb 2+ Cd 2 + Cr 6+ One or more of them.
[0024] The present invention also provides a heavy metal wastewater treatment device, comprising the above-mentioned electroadsorption electrode material, with a treatment voltage of 0.8-1.4 V.
[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects: In this invention, sodium sulfite pretreatment can significantly remove lignin (15-10 cm⁻¹) from wheat straw. -1 With 1460 cm -1 (The peak intensity decreased), which increased the crystallinity of cellulose from 39.08% to 56.57%, providing abundant active sites for heavy metal adsorption.
[0026] The sodium sulfite pretreatment + 0.5 g doping group described in this invention exhibits the highest capacity, reaching 106.20 F / g, with a capacitance retention rate exceeding 74% at a current density of 10 A / g; it also demonstrates high adsorption capacity for heavy metals, particularly Cd. 2+ The maximum adsorption capacity was 452.71 mg / g (initial concentration of 200 ppm), and the adsorption kinetics fit R²>0.97.
[0027] This invention uses agricultural waste wheat straw as raw material, which is widely available and low in cost; the pretreatment and doping process parameters are easy to control and do not require complex equipment; the electrodes can be desorbed and regenerated by shorting or reverse voltage, without secondary pollution, making it suitable for large-scale production.
[0028] The preparation method described in this invention has a processing voltage of 0.8-1.4 V, low energy consumption, and can be coupled with renewable energy sources such as solar and wind power. It is suitable for distributed heavy metal wastewater treatment scenarios and meets the wastewater treatment needs of different industries. Attached Figure Description
[0029] Figure 1 The CV curves of the electrode materials prepared in Examples 1, 2, 3, 1, 3, and 4 of this invention are obtained under the conditions of 1 mol / L NaCl solution as electrolyte and 10 mV / s scanning speed. The experimental results are all stable data obtained by repeating the experiment three times. Figure 2 The GCD curves of the electrode materials prepared in Examples 1, 2, 3 and Comparative Example 3 of this invention were obtained under the conditions of 1 mol / L NaCl solution as electrolyte and 1 A / g current density. The experimental results are all stable data obtained by repeating the experiment three times. Figure 3 The GCD specific capacitance curves and capacitance retention rates of the electrode materials prepared in Examples 1, 2, 3 and Comparative Example 3 of this invention were obtained under different current densities in an electrolyte of 1 mol / L NaCl solution. The experimental results are all stable data obtained by repeating the experiment three times. Figure 4 The Fourier transform infrared (FTIR) curves of the electrode materials prepared in Comparative Examples 1 and 3 of this invention are shown. The experimental results indicate that after boiling with sodium sulfite, the curves at 1510 cm⁻¹... -1 (Aromatic ring skeletal vibration) and 1460 cm -1 The peak intensity of the (aromatic ring CH deformation vibration) decreased significantly, indicating that the alkaline environment of sodium sulfite promoted the sulfonation and dissolution of lignin, effectively disrupting the aromatic skeleton structure. Simultaneously, the peak intensity at 1320-1260 cm⁻¹... -1 (Phenolic hydroxyl CO stretching vibration) and 1120-1030 cm -1 The peak intensity of (COC ether bond) was significantly weakened, indicating a decrease in phenolic hydroxyl content and ether bond breakage, reflecting the fragmentation and depolymerization of lignin molecules; Figure 5 The absorption-desorption curves (top) and pore size distribution diagrams (bottom) of the electrode materials prepared in Examples 1, 2, 1, and 3 of this invention are shown. Figure 6 The images show the Raman spectra of the electrode materials prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this invention. Figure 7 SEM images of the electrode materials prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this invention; Figure 8 The electrode material prepared in Example 1 of this invention is used for the electroadsorption of Cd of different concentrations. 2+ Adsorption curve; Figure 9 The contents of the three major elements (cellulose, hemicellulose, and lignin) in wheat straw before and after Na2SO3 pretreatment in Example 1 of this invention were determined. The results show that the lignin content decreased significantly after pretreatment. Detailed Implementation
[0031] To clearly demonstrate the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be comprehensively and accurately described below. It should be understood that the following embodiments are only for illustrating the present invention and are not intended to limit it. Unless otherwise expressly stated, all technical and scientific terms used herein follow the general definitions within the technical field, and all reagents mentioned meet industrial or analytical purity standards. Furthermore, the accompanying drawings and descriptions are intended to help those skilled in the art to deeply understand this application, and are not intended to limit the subject matter covered by the claims.
[0032] Regarding the "range" mentioned in this application, it is defined by setting a lower limit and an upper limit, which define the boundaries of a specific range. Such a range may or may not include its endpoints, and can be freely combined; that is, any lower limit can be combined with any upper limit to form a new range.
[0033] Unless otherwise specified, all embodiments and their optional solutions in this application can be combined with each other to create new technical solutions. Similarly, unless otherwise specified, all technical features and their optional features in this application can also be combined with each other to form new technical solutions.
[0034] Performance testing method for electrode materials prepared according to embodiments of the present invention: (1) Adsorption experiment: Heavy metal solutions with initial concentrations of 10, 20, 50, 100, and 200 ppm were prepared. 90 mL of each solution was placed in an electrolytic cell. Two electrodes with similar specific capacitances prepared in this invention were used as the positive and negative electrodes, respectively. The solution was stirred slowly at 200 r / min to ensure thorough mixing. A constant potential of 1.2 V was applied on a Chenhua 760E electrochemical workstation to construct the electroadsorption system. Samples were taken at 30 / 60 min intervals, and the concentration of heavy metal ions in the solution was determined by atomic absorption spectrophotometry (AAS).
[0035] (2) Structural and performance characterization tests: Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were performed using a Chenhua 760E electrochemical workstation. A three-electrode system was used, with the prepared electrode as the working electrode, the platinum electrode as the counter electrode, and the saturated calomel electrode as the reference electrode. The electrolyte was 1 mol / L NaCl solution. The specific capacitance was calculated using the equation "C = "I×∆t" / "m×∆V", where I(a), Δt(s), ΔV(V), and m(g) correspond to the applied current, discharge time, working voltage, and mass load of the active material, respectively. Specific surface area and pore size analysis (BET) was performed on an ASAP2460 four-station fully automatic specific surface area and pore size analyzer. Raman spectroscopy was measured on an HJY LabRAM Odyssey laser confocal micro Raman spectrometer.
[0036] Example 1 (Sodium sulfite pretreatment + 0.5g NH4H2PO4 doping) (I) Take 50 g of wheat straw, chop it into 2-3 cm pieces, add 250 mL of 15% Na2SO3 solution (solid-liquid ratio 1:5), cook at 165 ℃ for 2 h, and filter to obtain wheat straw fiber; (II) The wheat straw fiber was dried at 70 ℃ for 10 h, ground and passed through a 100-mesh sieve, and 1 g of the powder after sieving was taken. (III) Add 0.5 g of NH4H2PO4 and mix evenly (the mass ratio of straw powder to NH4H2PO4 is 1:0.5). Pass N2 into the tube furnace (50 mL / min), heat to 900 ℃ at 5 ℃ / min and keep warm for 2 h to obtain the active substance; (IV) Weigh 21 mg of active material, 6 mg of carbon black, and 3 mg of PVDF according to the ratio of active material: carbon black: PVDF = 7:2:1. Add 2 mL of NMP and homogenize for 30 min. Brush the mixture onto carbon cloth and vacuum dry at 80 °C for 12 h to obtain electrode sample 1.
[0037] Performance testing: The CV curve is rectangular (electrolyte 1 mol / L NaCl, 10 mV / s), indicating significant double-layer behavior; GCD test (1 A / g) shows a specific capacitance of 131.58 F / g and a capacitance retention of 74.86% at 10 A / g; the BET specific surface area is 1069.61 m². 2 / g, pore size distribution is mainly micropores and mesopores; SEM images show more obvious granular / porous modification characteristics; Raman spectroscopy shows ID / IG=0.92, indicating the highest degree of graphitization; 10 ppm Cd 2+ The adsorption capacity in solution was 197.00 mg / g, and equilibrium was reached in 250 min. The pseudo-second-order kinetics fit was R. 2 =0.9896.
[0038] Example 2 (Sodium sulfite pretreatment + 0.2 g NH4H2PO4 doping) Referring to Example 1, only the amount of NH4H2PO4 doping was changed to 0.2 g (the mass ratio of straw powder to NH4H2PO4 was 1:0.2), resulting in electrode sample 2.
[0039] Performance testing: The rectangularity of the CV curve is inferior to that of sample 1; GCD test (1A / g) shows a specific capacitance of 69.70 F / g and a capacitance retention of 84.21% at 10 A / g; the BET specific surface area is 1083.26 m². 2 / g, the pore size distribution is mainly mesoporous.
[0040] Example 3 (Sodium sulfite pretreatment + 1 g NH4H2PO4 doping) Referring to Example 2, only the amount of NH4H2PO4 doping was changed to 1 g (the mass ratio of straw powder to NH4H2PO4 was 1:1), resulting in electrode sample 3.
[0041] Performance testing: The rectangularity of the CV curve is inferior to that of sample 1; the specific capacity of the GCD test (1A / g) is 44.11F / g. The 10 A / g capacitance retention rate is 83.9%.
[0042] Comparative Example 1 (No pretreatment + No doping) Referring to Example 1, the sodium sulfite pretreatment in step (I) was omitted, and the wheat straw was directly crushed, sieved, and then pyrolyzed, with other conditions remaining unchanged, to obtain electrode sample 4.
[0043] Performance testing: CV specific capacity 32.5 F / g; BET specific surface area 416.99 m² 2 / g, with a relatively narrow pore size distribution, mainly concentrated in the smaller pore size region; Raman spectroscopy showed ID / IG=1.16, indicating the lowest degree of graphitization; SEM images showed limited channels and surface active sites.
[0044] Comparative Example 2 (No pretreatment + 0.5 g NH4H2PO4 doping) Referring to Example 1, the sodium sulfite pretreatment in step (I) was omitted. The wheat straw was directly crushed, sieved, and then doped and pyrolyzed. Other conditions remained unchanged, and electrode sample 5 was obtained.
[0045] Performance testing: SEM analysis showed a long, strip-like macroscopic morphology with no significant changes in the overall structure; Raman spectroscopy showed that ID / IG=1.16, indicating a graphitization degree similar to Comparative Example 1, but both inferior to Example 1.
[0046] Comparative Example 3 (Sodium sulfite pretreatment + no doping) Referring to Example 1, the NH4H2PO4 doping in step (III) was omitted, and only the wheat straw fiber pretreated with sodium sulfite was pyrolyzed, while other conditions remained unchanged, to obtain electrode sample 6.
[0047] Performance testing: CV specific capacity 47.87 F / g; SEM analysis revealed a fluffy, curly fibrous / flocculent morphology on the surface, with a rough surface and more developed pores; Raman spectroscopy showed ID / IG=1.14, indicating a slight improvement in graphitization compared to Comparative Examples 1 and 2, but still inferior to Example 1; BET specific surface area 698.58 m². 2 / g, the pore size distribution is mainly concentrated in micropores and mesopores, but the proportion is less than that in Example 1.
[0048] Comparative Example 4 (Water Hyacinth-based Carbon Material) Referring to Example 1, only the wheat straw was replaced with water hyacinth, while other conditions remained unchanged, to obtain electrode sample 7.
[0049] Performance testing: The specific capacitance calculated by CV testing was 89.5 F / g, significantly lower than the specific capacitance of 131.58 F / g for the electrode sample in Example 1. This indicates that wheat straw has a relative advantage as a biomass source for electrode materials.
[0050] The test results show that the present invention significantly improves the electrode specific capacity and heavy metal adsorption performance through the synergistic effect of pretreatment and N / P co-doping. Without pretreatment or doping, the material performance drops significantly. Sodium sulfite pretreatment of wheat straw combined with NH4H2PO4 doping is the optimal process, with the best overall performance.
[0051] This invention optimizes the microstructure and performance of electroadsorption electrode materials by precisely controlling the straw pretreatment process and N / P co-doping parameters, providing a feasible technical path for the efficient and low-consumption treatment of heavy metal wastewater, and has certain industrial application value.
[0052] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for preparing a biomass-based electroadsorption electrode material for treating heavy metal wastewater, characterized in that, Includes the following steps: (I) Chop the wheat straw and then add Na2SO3 solution for cooking to obtain delignified wheat straw fiber; (II) The wheat straw fiber obtained in step (I) is dried, ground, and then sieved to obtain straw powder; (III) After mixing straw powder with NH4H2PO4 evenly, the mixture is pyrolyzed at high temperature under an inert protective atmosphere; after natural cooling, N / P co-doped porous carbon active material is obtained. (IV) N / P co-doped porous carbon active material, conductive agent and binder are mixed and homogenized to form a slurry. The slurry is then coated on the surface of carbon cloth and dried to obtain the biomass-based electroadsorption electrode material for heavy metal wastewater treatment.
2. The preparation method according to claim 1, characterized in that, The steaming in step (I) is carried out at 120-180 ℃ for 2 h, the wheat straw is chopped into 2-3 cm pieces, the mass concentration of the Na2SO3 solution is 10-16%, and the solid-liquid ratio of the Na2SO3 solution to the wheat straw is 1:5-1:10 g / mL.
3. The preparation method according to claim 1, characterized in that, In step (II), the drying is performed at 60-80 ℃ to constant weight, and the sieving is performed through a 100-mesh sieve.
4. The preparation method according to claim 1, characterized in that, In step (III), the mass ratio of straw powder to NH4H2PO4 is 1:0.2-1, more preferably 1:0.
5.
5. The preparation method according to claim 1, characterized in that, In step (III), the inert protective atmosphere is N2 or Ar, and the flow rate is 50-200 mL / min; The high-temperature pyrolysis described in step (III) is carried out at 800-900 ℃ and held for 2 h.
6. The preparation method according to claim 1, characterized in that, In step (IV), the mass ratio of the N / P co-doped porous carbon active material, conductive agent, and binder is 7:2:1 or 8:1:1; when the N / P co-doped porous carbon active material, conductive agent, and binder are mixed, N-methylpyrrolidone is added as a solvent, and the ratio of the N / P co-doped porous carbon active material, conductive agent, and binder mixture to N-methylpyrrolidone is 15:1 mg / mL; the homogenization refers to homogenizing with a homogenizer for ≥30 min to form a slurry.
7. The preparation method according to claim 1, characterized in that, In step (IV), the conductive agent is carbon black and the binder is polyvinylidene fluoride.
8. The preparation method according to claim 1, characterized in that, In step (IV), the drying is performed under vacuum at 80 °C for 12 h.
9. An electroadsorption electrode material for treating heavy metal wastewater, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.
10. The application of the electroadsorption electrode material according to claim 9 in the treatment of wastewater containing heavy metals.