Modified biochar and its preparation method and application

Abstract

The present invention discloses a modified biochar, its preparation method, and application, belonging to the field of solid waste treatment technology. The present invention first dries and grinds sludge, and calcines it under nitrogen conditions to obtain sludge biochar; then, the sludge biochar is immersed in a KMnO4 solution, filtered, washed, and dried to obtain KMnO4-modified sludge biochar; finally, the KMnO4-modified sludge biochar is placed in a suspension of Saccharomyces cerevisiae, stirred, and centrifuged to obtain the modified sludge biochar. The present invention uses KMnO4 modification to allow more Saccharomyces cerevisiae flora to be fixed on the modified biochar, reducing flora loss and increasing the material's adsorption support capacity. KMnO4 modification also increases metal adsorption sites and cell attachment sites. The loading of Saccharomyces cerevisiae further increases the adsorption sites of the KMnO4-modified biochar and the stability of the adsorption material. Therefore, the combination of Saccharomyces cerevisiae and KMnO4 greatly increases the adsorption sites of the biochar for heavy metals and the adsorption stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste treatment, and specifically relates to a modified biochar and a preparation method and application thereof. Background Art

[0002] With rapid economic development, the volume of urban wastewater treated continues to rise, leading to a growing volume of sludge. Sludge contains high levels of heavy metals, organic micropollutants, and pathogens, posing a significant threat to the environment. However, it also contains significant amounts of nutrients and trace elements such as total nitrogen, total phosphorus, and total potassium, making it both a pollutant and a resource. Furthermore, with the advancement of industrialization, the environmental problems caused by heavy metals and emerging pollutants in wastewater are becoming increasingly serious. Furthermore, with the advancement of industrialization, the environmental problems caused by heavy metal pollution in mineral processing wastewater are becoming increasingly serious. Heavy metals are among the most dangerous pollutants, exhibiting high toxicity, carcinogenicity, and resistance to biodegradation, posing serious risks to ecosystems and human health. Large amounts of heavy metals in mineral processing wastewater are discharged into surface waters, contaminating groundwater.

[0003] After the sludge is prepared into biochar, not only can the heavy metals in the sludge be stabilized, but the obtained sludge biochar also has the characteristics of looseness and pores, large specific surface area, rich surface functional groups, and many active sites. It has good adsorption performance, which is not only conducive to the habitat and reproduction of microorganisms, but also can enhance the process of pollutant adsorption. In the existing technology, municipal sludge biochar can effectively adsorb heavy metal ions and antibiotics in water through precipitation, membrane separation, ion exchange and adsorption methods. In addition, municipal sludge biochar contains many mineral components (such as Si, Mg, Al, Fe and Ca) that are sensitive to Cu 2+ The adsorption of Pb in water can be effectively adsorbed by using the abundant functional groups on the surface after alkali modification. 2+ . For organic pollutants discharged by industries such as leather, textiles and papermaking, the inorganic components in sludge biochar (such as SiO2 and Al2O3) have better adsorption effects than other biochars. Sludge biochar can adsorb inorganic salt components (phosphates, nitrates, ammonium salts, etc.) in water through surface functional groups, electrostatics, co-precipitation, complexation and hydrogen bonding. In addition, biochar can increase the specific surface area and obtain a richer pore structure after various modifications and metal surface modification. The adsorption sites of biochar can be increased by loading microorganisms, thereby improving the adsorption performance of biochar, and the microorganisms themselves have a certain biological adsorption effect on heavy metals. In addition, biochar has a good removal effect on antibiotics, endocrine disruptors, microplastics and organic pollutants in water after various modifications and metal surface modification.

[0004] The existing technology uses sludge biochar as a carrier to make sewage treatment reactors. Phosphate is added during the preparation of sludge biochar, which can form stable phosphates with heavy metal ions in the soil, reduce the mobility of heavy metal ions, increase the phosphorus content in the soil, and promote the growth of rice. In addition, sludge biochar can be modified by ultraviolet radiation, surface loading of metals and their oxides, organic matter, acid and alkali solutions, etc., and can obtain a larger specific surface area and more pore structures and functional groups than the original biochar. In addition, fungi can tolerate and detoxify heavy metals through active accumulation, adsorption to mycelium and spores, intracellular and extracellular precipitation, and valence state conversion, thereby acting as a catalyst for heavy metal bioremediation and effectively removing heavy metals from the environment. However, fungi attached to the surface of biochar easily fall off, resulting in a decrease in the adsorption performance of the modified organisms for heavy metals and unstable adsorption performance. Summary of the Invention

[0005] In view of the above shortcomings of the prior art, the present invention proposes a modified biochar and a preparation method and application thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing modified biochar, comprising the following steps:

[0007] (1) drying and grinding the sludge, and then calcining it under nitrogen to obtain sludge biochar;

[0008] (2) soaking the sludge biochar in a KMnO4 solution, and then filtering, washing, and drying to obtain KMnO4-modified sludge biochar;

[0009] (3) The KMnO4-modified sludge biochar was placed in a suspension of Saccharomyces cerevisiae and stirred, and the modified sludge biochar was obtained after centrifugation.

[0010] As a preferred embodiment of the present invention, in step (1), the calcination temperature is 500-700°C, the time is 1.5-2h, the heating rate is 5-10°C / min, and the nitrogen flow rate is 100-200mL / min.

[0011] As a preferred embodiment of the present invention, in step (2), the concentration of the KMnO4 solution is 0.1 mol / L, and the mass volume ratio of the sludge biochar to the KMnO4 solution is 1 g:5-10 mL.

[0012] As a preferred embodiment of the present invention, the immersion time is 48-72 hours, the temperature is 25° C., and the sludge biochar is stirred in the KMnO 4 solution for 30-45 minutes before immersion.

[0013] As a preferred embodiment of the present invention, the concentration of Saccharomyces cerevisiae in the Saccharomyces cerevisiae suspension is 10 g / L.

[0014] As a preferred embodiment of the present invention, the mass volume ratio of the KMnO4 modified sludge organisms to the saccharomyces cerevisiae suspension is 1g:10-15ml.

[0015] As a preferred embodiment of the present invention, in step (3), the stirring time is 30-45 minutes and the temperature is 25°C.

[0016] The present invention also claims protection for the modified biochar prepared by the modified biochar preparation method.

[0017] The present invention also claims protection for the application of the modified biochar in removing heavy metals from mineral processing wastewater.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention improves the adsorption capacity of heavy metals by modifying the biochar with potassium permanganate and saccharomyces cerevisiae, increasing the specific surface area of ​​the biochar and obtaining a good pore structure.

[0020] (2) The present invention, through KMnO4 modification, allows more Saccharomyces cerevisiae colonies to be fixed on the modified biochar, reducing colony loss and increasing the material's adsorption support capacity. Furthermore, KMnO4 modification also increases metal adsorption sites and cell attachment sites. The loading of Saccharomyces cerevisiae further increases the adsorption sites of the KMnO4-modified biochar and the stability of the adsorption material. Therefore, the combination of Saccharomyces cerevisiae and KMnO4 significantly increases the adsorption sites of biochar for heavy metals and the stability of adsorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a flow chart of a method for preparing modified biochar and the application of modified biochar in removing heavy metals from mineral processing wastewater.

[0022] Figure 2 This is the SEM image of the sludge raw material.

[0023] Figure 3 These are the SEM images of the sludge biochar and modified biochar prepared in Example 1, where A is the SEM image of the sludge biochar and B is the SEM image of the modified biochar. DETAILED DESCRIPTION

[0024] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] like Figure 1 As shown, a method for preparing modified biochar comprises the following steps:

[0027] (1) Sludge (morphology see Figure 2 ) After drying and grinding through a 100-mesh sieve, the sludge was evenly placed in a high-temperature quartz boat, and then placed in the middle of a tube furnace. The nitrogen flow rate was set to 120 mL / min, the heating rate was 5 ° C / min, and it was fired at 500 ° C for 2 h to obtain sludge biochar (morphology see Figure 3 A).

[0028] (2) At 25°C, the sludge biochar was added to a 0.1 mol / L KMnO4 solution and magnetically stirred for 30 min, then immersed for 48 h, and finally filtered, washed, and dried to a constant temperature to obtain KMnO4-modified sludge biochar; the mass volume ratio of sludge biochar to KMnO4 solution was 1 g:5 ml.

[0029] (3) At 25 °C, KMnO4 modified sludge biochar was placed in a suspension of Saccharomyces cerevisiae and stirred for 30 min. The mixture was allowed to settle and the supernatant was removed. The mixture was centrifuged at 4800 r / min for 30 min to obtain modified sludge biochar (morphology shown in Figure 2). Figure 3 B); the mass volume ratio of KMnO4 modified sludge biochar to Saccharomyces cerevisiae suspension is 1g:10ml; the concentration of Saccharomyces cerevisiae in the Saccharomyces cerevisiae suspension is 10g / L.

[0030] like Figure 2 As shown in the figure, the morphology of the sludge raw materials is mainly blocky, with a relatively smooth surface and less pore structure.

[0031] like Figure 3 As shown in the figure, the surface of sludge biochar is rougher than that of sludge raw material, with less block structure and part of it being granular. After modification with KMnO4 and brewer's yeast, it can be clearly observed that the biochar is mainly granular and has a rich pore structure inside, which helps to improve its physical and chemical properties such as specific surface area and micropore area.

[0032] Example 2

[0033] A method for preparing modified biochar comprises the following steps:

[0034] (1) The sludge was dried and ground, passed through a 100-mesh sieve, and evenly placed in a high-temperature quartz boat. The boat was then placed in the middle of a tube furnace. The nitrogen flow rate was set to 200 mL / min, the heating rate was set to 10 °C / min, and the sludge was fired at 700 °C for 1.5 h to obtain sludge biochar.

[0035] (2) At 25°C, the sludge biochar was added to a 0.1 mol / L KMnO4 solution and magnetically stirred for 45 min, then immersed for 72 h, and finally filtered, washed, and dried to a constant temperature to obtain KMnO4-modified sludge biochar; the mass volume ratio of sludge biochar to KMnO4 solution was 1 g:10 ml.

[0036] (3) At 25°C, the KMnO4-modified sludge biochar was placed in a Saccharomyces cerevisiae suspension and stirred for 45 min. The mixture was allowed to settle and the supernatant was poured off. The mixture was centrifuged at 4800 r / min for 30 min to obtain the modified sludge biochar. The mass volume ratio of the KMnO4-modified sludge biochar to the Saccharomyces cerevisiae suspension was 1 g:15 ml. The concentration of Saccharomyces cerevisiae in the Saccharomyces cerevisiae suspension was 10 g / L.

[0037] Comparative Example 1

[0038] A method for preparing sludge biochar comprises the following steps:

[0039] The sludge was dried and ground through a 100-mesh sieve, then evenly placed in a high-temperature quartz boat and placed in the middle of a tube furnace. The nitrogen flow rate was set to 120 mL / min, the heating rate was set to 5°C / min, and it was fired at 500°C for 2 h to obtain sludge biochar.

[0040] Comparative Example 2

[0041] A method for preparing modified biochar comprises the following steps:

[0042] (1) After drying and grinding the sludge through a 100-mesh sieve, the sludge was evenly placed in a high-temperature quartz boat, which was then placed in the middle of a tube furnace. The nitrogen flow rate was set to 120 mL / min, the heating rate was set to 5 °C / min, and the sludge was fired at 500 °C for 2 h to obtain sludge biochar.

[0043] (2) At 25°C, the sludge biochar was added to a 0.1 mol / L KMnO4 solution and magnetically stirred for 30 min, then immersed for 48 h, and finally filtered, washed, and dried to a constant temperature to obtain KMnO4-modified sludge biochar; the mass volume ratio of sludge biochar to KMnO4 solution was 1 g:5 ml.

[0044] Comparative Example 3

[0045] A method for preparing modified biochar comprises the following steps:

[0046] (1) After drying and grinding the sludge through a 100-mesh sieve, the sludge was evenly placed in a high-temperature quartz boat, which was then placed in the middle of a tube furnace. The nitrogen flow rate was set to 120 mL / min, the heating rate was set to 5 °C / min, and the sludge was fired at 500 °C for 2 h to obtain sludge biochar.

[0047] (2) The sludge biochar was placed in a saccharomyces cerevisiae suspension at 25°C and stirred for 30 min. The mixture was allowed to settle and the supernatant was poured off. The mixture was centrifuged at 4800 r / min for 30 min to obtain modified sludge biochar. The mass volume ratio of the sludge biochar to the saccharomyces cerevisiae suspension was 1 g:10 ml. The concentration of saccharomyces cerevisiae in the saccharomyces cerevisiae suspension was 10 g / L.

[0048] Effect Example 1

[0049] Test samples: sludge biochar or modified biochar prepared in Example 1 and Comparative Examples 1-3.

[0050] The application of sludge biochar or modified biochar in the removal of heavy metals in mineral processing wastewater includes: placing the test sample in mineral processing wastewater with a pH of 6 and shaking it for 120 minutes at 25°C, where the solid-liquid ratio is 20g / L. The mineral processing wastewater is selected from a mining area in Yunnan Province. The mineral processing wastewater mainly contains Cu 2+ 、Cd 2+ 、Zn 2+ , Pb 2+ The concentrations of the metal ions are Cu 2+ =130mg / L, Cd 2+ =8.1mg / L, Zn 2+ =21.5mg / L, Pb 2+ =33.5mg / L, wastewater pH=3, use NaOH or HCl to adjust pH=6. The heavy metal removal efficiency is calculated by measuring the initial content of heavy metal ions in the wastewater, which is recorded as C0; the content of heavy metals in the mineral processing wastewater after removal treatment is recorded as C e , the results are shown in Table 1.

[0051] Table 1

[0052]

[0053] According to Table 1, the modified biochar prepared in the embodiment of the present invention has much higher removal efficiency for heavy metal ions than that of comparative examples 1-3.

[0054] Comparison of Example 1 and Comparative Examples 2-3 shows that the synergistic effect of KMnO4 and Saccharomyces cerevisiae achieves effective removal of heavy metal ions. After KMnO4 modifies the biochar, manganese oxide is loaded on the surface of the biochar. On the one hand, manganese oxide can combine with the functional groups on the cell wall of Saccharomyces cerevisiae to improve the adsorption stability of Saccharomyces cerevisiae. On the other hand, KMnO4 modification increases the types and number of oxygen-containing functional groups on the surface of the biochar and the cation exchange capacity, thereby increasing the electrostatic adsorption force between Saccharomyces cerevisiae and the biochar; and after KMnO4 modification, the aromaticity of the biochar is enhanced, the C / N ratio is increased, and the (O+N / C) ratio is reduced, thereby enhancing the surface zeta potential, making it more suitable for the growth and development of the flora and facilitating the fixation of microorganisms. In addition, the polar functional groups of the biochar are reduced, the polarity is reduced, and the Saccharomyces cerevisiae flora can better combine with the hydrophobic and non-polar surfaces. Therefore, the synergistic effect of KMnO4 and Saccharomyces cerevisiae, on the one hand, increases the attachment sites of metals and Saccharomyces cerevisiae, and improves the adsorption performance; on the other hand, after modification with KMnO4, the surface roughness of biochar increases and the granular structure increases, which is conducive to the attachment of Saccharomyces cerevisiae to deeper biochar, making full use of the pore structure of biochar and the biooxidation and bioremediation functions of Saccharomyces cerevisiae on metals to adsorb heavy metals in wastewater.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing modified biochar, characterized in that: The steps include: (1) Drying and grinding the sludge, and then calcining it under nitrogen to obtain sludge biochar; (2) Immersing the sludge biochar in a 0.1 mol / L KMnO4 solution, followed by filtration, washing, and drying to obtain KMnO4-modified sludge biochar; wherein the mass volume ratio of sludge biochar to KMnO4 solution is 1 g: 5-10 mL; (3) The KMnO4-modified sludge biochar was placed in a suspension of Saccharomyces cerevisiae and stirred, and the modified sludge biochar was obtained after centrifugation; The immersion time is 48-72 hours, the temperature is 25°C, and the sludge biochar is stirred in the KMnO4 solution for 30-45 minutes before immersion; The concentration of Saccharomyces cerevisiae in the Saccharomyces cerevisiae suspension is 10 g / L; the mass volume ratio of the KMnO4 modified sludge organisms to the Saccharomyces cerevisiae suspension is 1 g:10-15 ml.

2. The method for preparing modified biochar according to claim 1, wherein: In the step (1), the calcination temperature is 500-700°C, the time is 1.5-2h, the heating rate is 5-10°C / min, and the nitrogen flow rate is 100-200mL / min.

3. The method for preparing modified biochar according to claim 1, wherein: In the step (3), the stirring time is 30-45 minutes and the temperature is 25°C.

4. Modified biochar prepared by the method for preparing modified biochar according to any one of claims 1 to 3.

5. Use of the modified biochar as claimed in claim 4 in removing heavy metals from mineral processing wastewater.

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