Preparation method and application of iron-based modified charcoal adsorbent
By preparing iron-based modified biochar CF and CFN, the problems of difficult separation and poor stability of biochar in heavy metal wastewater treatment were solved, achieving efficient and stable thallium removal and low-cost treatment, which is suitable for industrial application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-20
- Publication Date
- 2026-04-07
AI Technical Summary
Existing biochar has problems such as difficulty in separation, poor stability, limited adsorption capacity and complex preparation process in the treatment of heavy metal wastewater. In particular, it performs poorly under the interference of coexisting ions and alkaline conditions, which limits its practical application.
Iron-based modified biochars CF and CFN were prepared by mixing pre-made biochar with potassium ferrate and ball milling, followed by pyrolysis under a protective atmosphere, thereby improving their adsorption performance.
Iron-based modified biochar CF and CFN exhibit high adsorption capacity and stability over a wide pH range, significantly improving the removal rate of thallium and resistance to interference from coexisting ions, reducing treatment costs, and possessing magnetic properties that facilitate solid-liquid separation, making them suitable for industrial applications.
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Figure CN121797263A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of adsorbent technology, specifically to a method for preparing and applying an iron-based modified biochar adsorbent. Background Technology
[0002] With rapid industrialization, heavy metal pollution has become a serious environmental problem. Thallium (Tl), a highly toxic heavy metal, poses a serious threat to ecosystems and human health when present in wastewater. Currently, adsorption is widely used in the treatment of heavy metal wastewater due to its simple operation and low cost. Biochar, as an excellent adsorbent material, has attracted widespread attention due to its wide availability, large specific surface area, and abundant surface functional groups. However, raw biochar faces challenges in application, including separation difficulties, poor stability, and limited adsorption capacity, which restricts its widespread application in practical wastewater treatment.
[0003] To improve the adsorption performance and practicality of biochar, researchers have attempted to modify it by introducing metal oxides. Iron-based modified biochar has become a research hotspot due to the stability of iron species, excellent magnetic properties, and strong adsorption capacity. Existing studies have shown that iron oxides such as Fe3O4 and α-Fe2O3 can enhance the adsorption of heavy metals through mechanisms such as surface complexation and electrostatic attraction. However, existing iron-based biochars still have limitations in terms of interference from coexisting ions, insufficient stability under alkaline conditions, and complex preparation processes, necessitating the development of improved iron-based biochar materials. Summary of the Invention
[0004] Against this background, this invention prepared iron-based modified biochar through different process routes and systematically investigated its adsorption performance and mechanism for Tl(I). The results show that the prepared material exhibits high adsorption capacity and stability over a wide pH range, providing a new material and method for the efficient treatment of thallium-containing wastewater.
[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing an iron-based modified biochar adsorbent, wherein the iron-based modified biochar adsorbent includes iron-based biochar CFN, and the method for preparing the iron-based biochar CFN is as follows: pre-prepared biochar BC-500 is uniformly mixed with K2FeO4 and ball-milled to obtain the adsorbent.
[0006] Preferably, the iron-based modified biochar adsorbent further includes iron-based biochar CF, which is prepared by uniformly mixing pre-prepared biochar BC-500 with K2FeO4 and ball milling it; then placing the ball-milled mixture in a tube furnace and pyrolyzing it under a N2 atmosphere.
[0007] Preferably, the pyrolysis conditions are: under a nitrogen atmosphere, the temperature is increased to 500°C at a rate of 2-20°C / min, and held at that temperature for 0.5-4 h.
[0008] More preferably, the pyrolysis conditions are: heating to 500°C at a rate of 5°C / min under a nitrogen atmosphere, and holding at that temperature for 2 hours.
[0009] Preferably, in the preparation of iron-based biochar CFN, the mass ratio of biochar BC-500 to K2FeO4 is 8-1:5-1.
[0010] More preferably, the mass ratio of biochar BC-500 to K2FeO4 in the preparation of iron-based biochar CFN is 5:3.
[0011] Preferably, in the preparation of iron-based biochar CF, the mass ratio of biochar BC-500 to K2FeO4 is 8-1:5-1.
[0012] More preferably, the mass ratio of biochar BC-500 to K2FeO4 in the preparation of iron-based biochar CF is 5:3.
[0013] Preferably, the preparation method of the biochar BC-500 is as follows: the biomass is dried at 105°C for later use, and then heated to 500°C at a rate of 5°C / min and kept at that temperature for 2 hours.
[0014] Secondly, the present invention provides an iron-based modified biochar adsorbent prepared by the preparation method described herein.
[0015] Thirdly, the present invention provides the application of the iron-based modified biochar adsorbent in the treatment of thallium-containing wastewater, wherein the iron-based modified biochar adsorbent is used to adsorb and remove thallium from the wastewater.
[0016] Preferably, the pH value of the wastewater is 3-11.
[0017] Preferably, the dosage of the iron-based modified biochar adsorbent is 0.5-5 g / L.
[0018] More preferably, the dosage of the iron-based modified biochar adsorbent is 0.5-1 g / L.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The adsorption performance of iron-based biochar CF and CFN for Tl(I) is significantly better than that of biochar BC-500, with CF showing the best performance: at a dosage of 1 g / L and pH=7, the removal rate of Tl(I) reaches 97.87%, and the equilibrium adsorption capacity reaches 11.88 mg / g. At a dosage of 5 g / L, the removal rate of Tl(I) for all three adsorbents is close to 99%, achieving deep purification.
[0020] (2) Within a wide pH range of 3-11, the removal rates of Tl(I) by CF and CFN remained stable, with the removal rate of CF consistently above 97%. Even under strongly acidic conditions, the risk of iron leaching was low, and the adsorption performance showed no significant decline, thus solving the problem of insufficient stability of traditional adsorbents under extreme pH conditions.
[0021] (3) Facing the common coexisting cations (Ca) in wastewater 2+ Mg 2+ Cd 2+ The adsorption performance of CF and CFN is significantly inhibited compared to biochar BC-500: the removal rate of CF can still reach 90.22%, which is significantly improved compared to BC-500 (50.81%), and can be adapted to the actual complex treatment scenarios of thallium-containing wastewater.
[0022] (4) CF can achieve efficient removal with a dosage of only 1 g / L, which is 80% lower than the dosage of biochar BC-500 (which requires more than 5 g / L), greatly reducing treatment costs and solid waste generation; at the same time, iron oxide imparts magnetism to the adsorbent, which facilitates solid-liquid separation and regeneration, further enhancing its practical application value.
[0023] (5) The preparation of adsorbent does not require complex equipment and can be achieved by mixing-ball milling or mixing-ball milling-pyrolysis. The pyrolysis conditions are mild (500℃, 0.5-4 h). Biochar raw materials (seafood mushroom substrate) are widely available and suitable for industrial mass production. Attached Figure Description
[0024] Figure 1 The removal rate of Tl(I) by biochar and the pH value of the solution after reaction are shown under different initial pH conditions.
[0025] Figure 2 The effect of solid-liquid ratio on the adsorption of Tl(I) by biochar.
[0026] Figure 3 The effect of coexisting cations on the adsorption of Tl(I) by biochar.
[0027] Figure 4 X-ray diffraction spectroscopy characterization of biochar.
[0028] Figure 5A The Fourier transform infrared spectrum of biochar before adsorption of Tl(I) is shown.
[0029] Figure 5B The Fourier transform infrared spectrum is shown for biochar after adsorption of Tl(I).
[0030] Figure 6A The fine XPS-Tl 4f spectrum of BC-500 after adsorption of Tl(I).
[0031] Figure 6B The fine XPS-Tl 4f spectrum of iron-based biochar after adsorption of Tl(I) by CF.
[0032] Figure 6C The fine XPS-Tl 4f spectrum of iron-based biochar CFN after adsorption of Tl(I). Detailed Implementation
[0033] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially.
[0034] Example 1: Experimental Materials and Methods 1.1 Experimental Materials The reagents used are listed in Table 1, and the instruments used are listed in Table 2.
[0035] Table 1 Experimental Reagents
[0036] Table 2 Experimental Instruments
[0037] The raw material for preparing primitive biochar is edible fungi cultivation substrate.
[0038] 1.2 Preparation of different types of iron-based biochar (1) Preparation of CF: The pre-made biochar BC-500 and potassium ferrate (K2FeO4) were mixed uniformly at a mass ratio of 5:3 and ball-milled. Then, the ball-milled mixture was placed in a tube furnace, heated to 500°C at a rate of 5°C / min under N2 atmosphere and pyrolyzed for 2 h. The resulting product was denoted as iron-based biochar CF. The preparation method of the biochar BC-500 is as follows: the biomass (seafood mushroom substrate) is dried at 105℃ and set aside for later use, and then heated to 500℃ at a rate of 5℃ / min and kept at that temperature for 2 hours.
[0039] (2) Preparation of CFN: The pre-made biochar BC-500 and K2FeO4 were mixed uniformly at a mass ratio of 5:3 and ball-milled. The resulting mixture was directly recorded as iron-based biochar CFN (without undergoing a secondary pyrolysis step). The preparation method of the biochar BC-500 is as follows: the biomass (seafood mushroom substrate) is dried at 105℃ and set aside for later use, and then heated to 500℃ at a rate of 5℃ / min and kept at that temperature for 2 hours.
[0040] (3) Preparation of BC-500: The biomass (edible fungus cultivation substrate) was dried at 105℃ and kept warm at a rate of 5℃ / min to 500℃ for 2 hours to obtain biochar BC-500.
[0041] Example 2 Adsorption Performance Study 2.1 Adsorption Kinetics The kinetic model fitting results in Table 3 confirm that the adsorption process of Tl(I) by different types of biochar also conforms more closely to the pseudo-second-order kinetic model, indicating that its adsorption kinetic behavior may be dominated by chemical reactions (such as ion exchange or complexation). Moreover, compared with BC-500 and CFN, CF has a higher equilibrium adsorption capacity and initial adsorption rate for Tl(I), and its adsorption performance is the best.
[0042] Table 3. Model parameters of adsorption kinetic equations for different types of biochar
[0043] 2.2 Effect of initial pH value Depend on Figure 1 (Adsorption conditions: initial concentration = 10 mg / L, adsorbent mass = 1 g / L, background ion NaNO3 = 0.01 mol / L) It can be seen that within the pH range of 3-11, the removal rate of Tl(I) by different types of biochar remained stable, indicating that this pH range is not a key factor affecting the Tl(I) removal efficiency. Although under strongly acidic conditions, the iron component in iron-based biochar may dissolve and release Fe. 3+ / Fe 2+ Iron ions compete with Tl(I) for active adsorption sites, potentially weakening adsorption performance. However, both iron-based biochars maintained high Tl(I) removal rates under strongly acidic conditions, demonstrating good acid resistance. This characteristic also proves that CF and CFN significantly improve the applicability of biochars under a wide range of pH conditions compared to BC-500. Specifically, CF achieved a removal rate of over 97% under different initial pH conditions, significantly higher than BC-500 and CFN.
[0044] 2.3 Effect of initial solid-liquid ratio Figure 2(Adsorption conditions: initial concentration = 10 mg / L, pH = 7, background ion NaNO3 = 0.01 mol / L) This study demonstrates the effect of solid-liquid ratio on the adsorption of Tl(I) in solutions by biochar prepared by different methods. Within a solid-liquid ratio range of 0.5–1 g / L, the removal rates of Tl(I) by the three biochars all showed a rapid upward trend with increasing solid-liquid ratio. Specifically, when the solid-liquid ratio reached 1 g / L, the removal rates of Tl(I) by BC-500, CF, and CFN reached 71.7%, 97.87%, and 88.15%, respectively. Notably, when the solid-liquid ratio increased to 5 g / L, the removal efficiency of the three biochars approached complete removal (approximately 99%), indicating that the adsorption process tended to saturate at this dosage. These results demonstrate that iron oxide modification effectively enhances the adsorption capacity and affinity of biochar for Tl(I) ions. This is directly reflected in the fact that iron-modified materials can achieve highly efficient Tl(I) removal at significantly lower solid-liquid ratios (e.g., 1 g / L). Among them, CF material stands out, achieving a removal rate of 97.87% with a dosage of only 1 g / L, far superior to BC-500 and CFN under the same conditions. This highly efficient adsorption performance means that when treating Tl(I)-containing wastewater, CF can significantly reduce the adsorbent dosage by 50-80% while maintaining high removal efficiency, thereby greatly reducing treatment costs and subsequent solid waste treatment volume, demonstrating significant economic and environmental benefits.
[0045] 2.4 Effect of coexisting cations Figure 3 (Adsorption conditions: initial concentration = 10 mg / L, adsorbent mass = 1 g / L, pH = 7, background ion NaNO3 = 0.01 mol / L) This demonstrates the coexistence of cations (Ca... 2+ Mg 2+ and Cd 2+ The effect of different types of biochar on the removal of Tl(I). Figure 3 As shown, in the presence of coexisting cations, the removal rates of Tl(I) by the three biochars decreased to varying degrees. The removal rate of BC-500 decreased to 50.81%, a reduction of 20.89% compared to the control group (CK) without added cations; the removal rate of CFN decreased to 78.93%; and the removal rate of CF decreased to 90.22%. Ca 2+ Mg 2+ and Cd 2+ It has a general inhibitory effect on the adsorption of Tl(I) by biochar, but its inhibitory strength on CFN and CF is significantly weaker than that of BC-500.
[0046] Example 3: Study on Adsorption Mechanism As shown in Table 4, the specific surface area, average pore size, and pore volume of both iron-based biochars were significantly lower than those of BC-500. This phenomenon can be attributed to the fact that BC-500 already possesses a well-developed pore structure, while the subsequently loaded iron oxide particles may have blocked some of the pores. However, despite their inferior pore structure parameters compared to BC-500, the overall adsorption performance of both iron-based biochars was actually better (CF was better than CFN, which was better than BC-500). This indicates that specific surface area and pore structure are not the main determining factors for improved adsorption performance, and there may be other more dominant adsorption mechanisms.
[0047] Table 4. Specific surface area and pore structure characteristics of biochar
[0048] like Figure 4 As shown, phase analysis of biochar prepared by different synthesis methods was performed by X-ray diffraction (XRD). The results showed that the main crystalline phase of BC-500 was calcium carbonate (CaCO3), which is due to the presence of gypsum (CaSO4) and lime (CaO) in the matrix. The main diffraction peaks of the two iron-based biochar samples, CF and CFN, both matched the characteristic peaks of the standard spectrum of magnetite (Fe3O4), indicating that their main crystalline phase was magnetite. This result confirms that iron was successfully loaded onto the biochar substrate in the form of highly crystalline magnetite during their respective synthesis processes. Furthermore, the presence of the magnetite phase directly endows both composite materials with inherent magnetic properties.
[0049] like Figure 5A , Figure 5B As shown, both iron-based biochar materials were at 701 cm⁻¹ -1 and 573 cm -1 Characteristic absorption peaks were observed, corresponding to high-spin Fe in Fe3O4. 3+ The stretching vibrations of the Fe-O functional groups within the complex further demonstrate that iron oxides are loaded onto biochar. Furthermore, 1455 cm⁻¹ -1 The absorption peak observed at 3420 cm⁻¹ can be attributed to the presence of Fe-OH groups. Simultaneously, the absorption peak at 3420 cm⁻¹... -1 The broad absorption peak at 1625 cm⁻¹ also indicates the presence of stretching vibrations of hydroxyl groups (-OH) on the material surface. -1 The distinct absorption peak at 863 cm⁻¹ corresponds to the stretching vibration of the C=C bond in the aromatic skeleton or olefin. -1 The peak detected at 1048 cm⁻¹ corresponds to the in-plane bending vibration of the CO bond in the carbonate. -1 The peak value at that point is due to the contribution of -COOH.
[0050] The K2FeO4-modified biochar not only successfully introduced iron-containing functional groups (such as Fe-O and Fe-OH), but its surface was also rich in various functional groups such as -OH, C=C, and -COOH. After the adsorption reaction, FTIR analysis showed that the intensity of the characteristic peaks of -OH and Fe-O was enhanced, while the positions of the characteristic peaks of C=C and Fe-OH shifted. These spectral changes indicate that, in addition to ion exchange and electrostatic attraction, the surface complexation reaction between iron-containing groups (especially Fe-O and Fe-OH) and Tl(I) is likely another important mechanism for the efficient adsorption of Tl(I) by iron-based biochar.
[0051] like Figure 6A , Figure 6B , Figure 6C As shown, compared with BC-500, the characteristic peak of Tl 4f was also clearly observed in the iron-based biochar sample after adsorption. Combined with energy analysis, it was confirmed that the Tl adsorbed by the iron-based biochar did not undergo redox reaction and existed stably in the Tl(I) valence state. The stability of this Tl(I) valence state is consistent with the observation results of the original biochar. The FTIR (Fourier Transform Infrared Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy) data of this invention further support that the mechanism of Tl(I) removal by iron-based biochar involves electrostatic attraction, surface complexation (involving iron- and oxygen-containing functional groups), and ion exchange. In addition, the magnetic iron oxides (such as Fe3O4) loaded on the surface of the iron-based biochar give it a significant advantage. Compared with the non-magnetic original biochar BC-500, iron-based biochar can be more conveniently separated into solid and liquid and regenerated through adsorption-desorption (desorption) processes, providing important convenience for its practical application.
[0052] Based on the above experimental results, CF exhibits significant advantages in adsorption rate, environmental adaptability, anti-interference ability, and treatment economy, making it the best-performing adsorbent overall; CFN is second best; and BC-500 is the weakest. Overall, the adsorption performance of the three biochar adsorbents prepared in this embodiment for Tl(I) shows that CF is superior to CFN, and CFN is superior to BC-500.
[0053] It should be understood that the disclosed invention is not limited to the specific methods, schemes, and substances described, as these are all subject to variation. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of the invention, which is limited only by the appended claims.
Claims
1. A method for preparing an iron-based modified biochar adsorbent, characterized in that, The iron-based modified biochar adsorbent includes iron-based biochar CFN, which is prepared by uniformly mixing pre-prepared biochar BC-500 with K2FeO4 and then ball milling it.
2. The preparation method according to claim 1, characterized in that, The iron-based modified biochar adsorbent also includes iron-based biochar CF, which is prepared by uniformly mixing pre-prepared biochar BC-500 with K2FeO4 and ball milling it; then placing the ball-milled mixture in a tube furnace and pyrolyzing it under a N2 atmosphere.
3. The preparation method according to claim 2, characterized in that, The pyrolysis conditions are as follows: under a nitrogen atmosphere, the temperature is increased to 500℃ at a rate of 2-20℃ / min, and held at that temperature for 0.5-4 h.
4. The preparation method according to claim 1, characterized in that, In the preparation of iron-based biochar CFN, the mass ratio of biochar BC-500 to K2FeO4 is 8-1:5-1.
5. The preparation method according to claim 2, characterized in that, In the preparation of iron-based biochar CF, the mass ratio of biochar BC-500 to K2FeO4 is 8-1:5-1.
6. The preparation method according to claim 1 or 2, characterized in that, The preparation method of the biochar BC-500 is as follows: the biomass is dried at 105℃ for later use, and then heated to 500℃ at a rate of 5℃ / min and kept at that temperature for 2 hours.
7. The iron-based modified biochar adsorbent prepared by the preparation method according to any one of claims 1-5.
8. The application of the iron-based modified biochar adsorbent according to claim 7 in the treatment of thallium-containing wastewater, characterized in that, The iron-based modified biochar adsorbent is used to adsorb and remove thallium from wastewater.
9. The application according to claim 8, characterized in that, The pH value of the wastewater is 3-11.
10. The application according to claim 8, characterized in that, The dosage of the iron-based modified biochar adsorbent is 0.5-5 g / L.