Sludge modified biochar based on phosphoric acid modification and activation as well as preparation method and application of sludge modified biochar

Abstract

The invention discloses sludge modified biochar based on phosphoric acid modification and activation and a preparation method and application thereof, and belongs to the technical field of treatment of wine brewing waste products. The preparation method comprises the following steps: drying biochemical sludge to prepare granular dried sludge; mixing the dried sludge with an H3PO4 modifier; raising the temperature to 700-800 DEG C at a constant speed in an inert atmosphere, and carrying out pyrolysis for several hours; and finally, washing with diluted hydrochloric acid or a NaOH solution to be neutral, and drying to obtain the sludge modified biochar. Phosphorus-containing functional groups (P = O, P-O-C, P = OOH) are introduced into a carbon skeleton by phosphoric acid through a dehydration reaction. Meanwhile, the pore expanding effect is achieved, and the average pore diameter is increased to 10.42 nm from 5.93 nm (when the ratio is 1: 1). The removal rate of phosphorus in the wine brewing wastewater reaches 67.15%, which is superior to that of an unmodified sample (20.15%).

Description

Technical Field

[0001] The present invention belongs to the technical field of treatment of winemaking waste products, and in particular relates to a sludge-modified biochar based on phosphoric acid modification and activation, and a preparation method and application thereof. Background Art

[0002] Baijiu (Chinese liquor), a distilled spirit unique to my country, produces large quantities of high-concentration organic wastewater (high COD, low pH, high SS, and high nitrogen, phosphorus, and sulfur content) during its production process. China has issued relevant emission standards (such as GB 27631-2011) requiring increased water reuse. During the production of baijiu, every ton of 65% vol baijiu produces 48 tons of wastewater and 1.5 tons of biochemical sludge. Biochemical sludge is a solid byproduct of wastewater treatment, containing organic matter, bacterial residues, and toxic substances (such as pathogens and heavy metals). Improper handling can easily cause pollution. Currently, dewatering and landfilling are the primary method used in China, but this method poses challenges such as large land occupation, greenhouse gas emissions, and high costs. Resource-resource-based alternatives are urgently needed.

[0003] Biochar, a highly efficient adsorption material produced by pyrolysis of biochemical sludge, features high porosity and a large surface area, making it suitable for wastewater treatment (adsorbing heavy metals and organic matter). Using biochemical sludge to produce biochar not only recycles the sludge but also adsorbs pollutants from brewery wastewater, embodying the concept of "waste treatment with waste." Unmodified biochar lacks specific functional groups on its surface, resulting in weak selective adsorption of phosphorus pollutants in brewery wastewater. Its low micropore ratio also hinders the capture of small molecule pollutants. Summary of the Invention

[0004] The present invention aims to provide a sludge-modified biochar based on phosphoric acid modification and activation, and its preparation method and application, in order to solve the technical problem of how to modify the biochemical sludge of brewing wastewater into biochar with high adsorption performance for brewing wastewater.

[0005] A method for preparing sludge-modified biochar based on phosphoric acid modification and activation in this scheme comprises the following steps:

[0006] S1. Drying and granulation: drying the biochemical sludge to make granular dry sludge;

[0007] S2, H3PO4 modification: mixing H3PO4 modifier with dry sludge;

[0008] S3, inert pyrolysis: in an inert atmosphere, the temperature is raised to 700-800°C at a constant rate and pyrolysis is carried out for several hours;

[0009] S4. Acid-base washing: washing with dilute hydrochloric acid or NaOH solution until neutral, drying to obtain sludge-modified biochar containing P=O functional groups.

[0010] Furthermore, in S1, the biochemical sludge is passed through a 20-mesh sieve, dried at 100-110° C., and then crushed to 60 mesh.

[0011] Furthermore, in said S4, after drying, the product is sieved through a 60-mesh sieve to obtain a specific surface area of ≥214m 2 / g of sludge-modified biochar, with a pore volume of 3 to 4.3 nm and micropores. This microporous structure provides numerous adsorption sites suitable for small molecule pollutants (such as COD); the microporous structure facilitates physical adsorption and capillary coagulation. The high specific surface area and specific pore size enhance the adsorption capacity for typical pollutants in brewery wastewater (such as ethanol and organic acids).

[0012] Furthermore, in S3, the temperature was raised to 750° C. at 5° C. / min under a nitrogen atmosphere and pyrolysis was performed for 4 hours. The pyrolysis parameters were optimized to achieve a balance between biochar yield and adsorption performance. The nitrogen atmosphere prevented oxidation and maintained the integrity of the carbon skeleton.

[0013] Furthermore, the concentration of the dilute hydrochloric acid is 10%, and the concentration of the NaOH solution is 0.1 mol / L.

[0014] Furthermore, the ratio of the ZnCl2 modifier to the dried sludge is 0.1:1 to 1:1.

[0015] Disclosed is a sludge-modified biochar based on phosphoric acid modification and activation. The sludge-modified biochar is prepared by the method for preparing the sludge-modified biochar based on phosphoric acid modification and activation according to the present invention.

[0016] The sludge-modified biochar based on phosphoric acid modification and activation described in the present invention can be used alone or in combination with other wastewater purification reagents for the purification treatment of brewing wastewater.

[0017] Furthermore, the sludge-modified biochar based on phosphoric acid modification and activation was used to adsorb phosphorus in brewing wastewater, with an addition amount of 15 g / L, pH = 6, temperature of 20°C, and time of 80 min, and a phosphorus removal rate of ≥67.15%.

[0018] The beneficial technical effect of the present invention is that phosphoric acid introduces phosphorus-containing functional groups (P=O, POC, P=OOH) into the carbon skeleton through a dehydration reaction. At the same time, it has a pore expansion effect, and the average pore diameter increases from 5.93nm to 10.42nm (at a ratio of 1:1). The removal rate of phosphorus in brewing wastewater reaches 67.15%, which is better than that of the unmodified sample (20.15%). Table 1 shows the comparative data of the P adsorption effect in brewing wastewater before and after biochar modification. The adsorption conditions are an addition amount of 15g / L, pH=6, a temperature of 20°C, and a time of 80min.

[0019] Table 1 Comparison of adsorption effects before and after biochar modification

[0020] Unmodified biochar Modified biochar P adsorption rate (%) 20.15 67.15 BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The effect of the amount of phosphoric acid modifier added on TC / TOC in biochar;

[0022] Figure 2 The effect of the amount of phosphoric acid modifier added on the ash content of biochar;

[0023] Figure 3 Fourier transform infrared spectrum of biochar prepared by phosphoric acid modifier;

[0024] Figure 4 Raman comparison spectrum of biochar prepared by phosphoric acid modifier;

[0025] Figure 5 XRD spectrum of biochar material prepared with phosphoric acid modifier;

[0026] Figure 6 Electron microscopic morphology of biochar materials prepared with phosphoric acid modifier (a and b are electron microscopic morphology of biochar at different magnifications without adding modifier; c and d correspond to electron microscopic images of the ratio of phosphoric acid addition to biochemical sludge of 0.1:1; e and f correspond to the ratio of 0.3:1; g and h correspond to the ratio of 0.5:1; i and j correspond to the ratio of 0.7:1; k and l correspond to the ratio of 1:1);

[0027] Figure 7 Nitrogen adsorption-desorption isotherms of biochar samples prepared with phosphoric acid modifier;

[0028] Figure 8 Particle size distribution of biochar produced with phosphoric acid modifier. DETAILED DESCRIPTION

[0029] The following is further described in detail through specific implementation methods:

[0030] 1. Implementation

[0031] A method for preparing sludge-modified biochar based on phosphoric acid modification and activation comprises the following steps:

[0032] S1. Dry the biochemical sludge to make granular dry sludge

[0033] Biochemical sludge is used as raw material, and is pre-sieved through a 20-mesh sieve and placed in a sample container. It is dehydrated in an electric blast drying oven at 105°C for 6 hours, and the sample is taken out. Finally, the dried sample is sieved through a 60-mesh sieve to obtain biochemical sludge powder, which is then sealed and stored for later use.

[0034] S2. Mix H3PO4 modifier with dry sludge

[0035] The amount of modifier added to 2g of dry biochemical sludge was used as a variable, and the ratio of the added amount to the biochemical sludge was 0.1:1, 0.3:1, 0.5:1, 0.7:1, and 1:1. The masses of the added modifier were 0.2g, 0.6g, 1.0g, 1.4g, and 2.0g, respectively.

[0036] S3. Raise the temperature to 700-800℃ at a constant speed in an inert atmosphere and pyrolyze for several hours.

[0037] The modifier and the dried biochemical sludge powder were mixed and put into a crucible, and calcined at 750 ° C in a N2 atmosphere for 4 h with a heating rate of 5 ° C / min. After the reaction was completed, it was naturally cooled.

[0038] According to the different amounts of sample modifier added, the samples were named BC-H3PO4 0.1:1 , BC-H3PO4 0.3:1 , BC-H3PO4 0.5:1 , BC-H3PO4 0.7:1 , BC-H3PO4 1:1 The sample control group without adding modifier was named C-control.

[0039] S4, washing with dilute hydrochloric acid or NaOH solution until neutral, drying to obtain the sludge-modified biochar

[0040] The crude sample obtained after calcination was washed with a 10% dilute hydrochloric acid solution or a 0.1 mol / L NaOH solution to a pH of approximately 7, then rinsed 3-5 times with deionized water to remove impurities. The washed sample was then filtered and dried in an oven to a constant weight. After cooling, the dried sample was passed through a 60-mesh sieve to obtain the modified biochar material. The samples were individually sealed in sealed bags, named, and stored in a desiccator until ready for use.

[0041] 2. Detection and Analysis

[0042] The seven indicators of composition analysis, FT-IR, XRD, Raman, BET, laser particle size and SEM of the modified biochar material were analyzed and tested, and the carbon production results were obtained by analyzing the data.

[0043] 1. Adsorption performance of modified biochar

[0044] The modified biochar with the most significant increase in specific surface area and the largest specific surface area among the biochars produced by adding different amounts of phosphoric acid modifier was selected for adsorption performance research. First, a preliminary dilution test was performed on the brewery wastewater to determine the diluted concentration of the brewery wastewater as the initial concentration, which served as the mother liquor for the adsorption performance study. Then, the effect of adsorption time on adsorption performance was studied separately, and the phosphorus (P) content in the brewery wastewater was measured separately. The removal rate of the content before and after adsorption was compared to determine the adsorption effect. The experimental plan is as follows:

[0045] In order to study the adsorption performance, the brewery wastewater was first diluted 5000 times and its concentration was measured as the mother liquor. The mother liquor was then subjected to a series of studies:

[0046] (2) Influence of adsorption time

[0047] 20.0 mL of brewery wastewater mother liquor was adjusted to pH 7, 0.4 g of sludge-modified biochar was added, the magnetic stirrer speed was set at 200 rpm, and the adsorption temperature was maintained at 30°C. Adsorption was continued for 30, 40, 60, 80, and 100 minutes, respectively. After adsorption was complete, the liquid was filtered and the phosphorus content was determined.

[0048] 2. Analysis Method

[0049] (1) Composition analysis

[0050] The total carbon (TC) and organic carbon (TOC) content of the biochar samples was determined using a TOC analyzer, a Jena multi N / C 3100 from Germany. The test employed non-dispersive infrared absorption, using high-temperature catalytic combustion oxidation. The measurement range was 0-30,000 ppm, with a resolution of 4 ppd.

[0051] The ash content is determined by the muffle furnace ignition method in accordance with GB 5009.4-2016.

[0052] (2) Structural analysis

[0053] This experiment primarily analyzes the sample's structure, specifically its phase structure, surface group structure, and carbon structure. To accomplish these analyses, we employed a variety of advanced analytical and characterization instruments, including Fourier transform infrared spectroscopy (FT-IR), laser Raman spectroscopy (Raman), and X-ray diffractometers (XRD). These instruments provide a more accurate understanding of the sample's internal structure and properties.

[0054] In order to characterize the functional group structure of the sample, a Fourier transform infrared spectrometer was used, specifically the Shimadzu IRTracer 100 from Japan. During the test, the sample to be tested was pretreated according to the KBr pellet method. Specifically, the sample to be tested was mixed with KBr in a mass ratio of 1:100 and ground in a mortar until fine. Subsequently, the sample was taken and pelletized. During the infrared scanning process, the scanning area was set to 400-4000cm-1, the instrument resolution was set to 4cm-1, the number of scans was 64, and the test temperature was maintained at 25°C. Through this series of operations, the infrared spectrum data of the sample can be accurately obtained, and the functional group structure of the sample can be analyzed.

[0055] A LabRAM HR evolution laser Raman spectrometer from Horiba Scientific (Japan) was used to analyze and characterize the sample's morphology and crystallinity. During the test, sludge-modified biochar powder was used as the sample, and the Raman spectrometer was set to an excitation source of 325 nm and a scan range of 100–3800 nm.

[0056] The composition and phase structure of the samples were analyzed in depth using a Bruker D8 Advance X-ray diffractometer from Bruker, Germany. Cu-Kα was used as the emission source, with a scan rate of 2° / min, a scan range of 5-90°, an operating voltage of 40 kV, and a current of 40 mA. The entire test was performed at room temperature.

[0057] (3) Morphology analysis

[0058] The microscopic morphology of the samples was characterized using a field-emission scanning electron microscope (FESEM). The instrument used for this experiment was a German Zeiss SIGMA HD equipped with an OXFORD X-MAS spectrometer. During the test, sample powder was evenly sprinkled onto the conductive adhesive on the sample stage via a capillary tube. The sample was then gold-plated, and the surface morphology was analyzed in detail using a FESEM.

[0059] (4) Analysis of specific surface area, pore size and particle size distribution

[0060] The pore size distribution and specific surface area of the biochemical sludge were calculated using a Micromeritics ASAP2460 surface area analyzer (BET) and the Brunauer-Emmett-Teller (BET) method. The particle size distribution of the biochar was analyzed using a Malvern Mastersizer 2000 laser particle size analyzer (UK). Deionized water was used as the dispersant, and ultrasonication was performed for 20 minutes. The particle size distribution was measured at the D90, D50, and D10 ranges.

[0061] (5) Adsorption performance analysis

[0062] The determination of P shall refer to GB / T 11893-1989 and be carried out using a spectrophotometer.

[0063] 3. Results

[0064] Figure 1The figure shows the effect of the amount of H3PO4 modifier added on the TC / TOC ratio in biochar. As can be seen from the figure, as the amount of modifier added increases, the TC and TOC contents show a downward trend. The TC and TOC contents of the biochemical sludge were 280.35 g / kg and 224.91 g / kg, respectively. Without the addition of the modifier, the TC and TOC of the biochar were 216.43 g / kg and 183.64 g / kg. With the increase of the modifier, the TC and TOC ultimately dropped to 79.71 g / kg and 76.66 g / kg. The results show that after pyrolysis, the TC and TOC of the biochar decreased significantly, resulting in significant carbon loss. This is due to the thermal cracking of the biochemical sludge caused by calcining the biochemical sludge at high temperatures.

[0065] Figure 2 The effect of the amount of H3PO4 modifier added on the ash content of biochar. The results show that as the amount of modifier added increases, the ash content also increases, from 73.5% when no modifier is added, and finally reaches 86.24% when the ratio of modifier addition to biochemical sludge is 1:1. The increase in ash content is due to the high pyrolysis temperature and the effect of the modifier.

[0066] Figure 3 The following is the Fourier transform infrared spectrum of biochar prepared by adding different amounts of H3PO4 modifier. Fourier transform infrared spectroscopy is used to explore the surface functional groups of the material. Figure 3 It can be seen that the biochar materials with and without H3PO4 modifier added have a high -1 A small stretching vibration appeared at 1625cm, corresponding to OH, and the peak became stronger after adding the modifier; -1 There is a very weak absorption peak at 2922cm, which corresponds to C=O. -1 and 2864cm -1 The infrared peak of CH appeared at 1113 cm -1 and 995cm -1 Phosphorus-related functional groups (P=O, POC, P=OOH) appeared at the surface of the biochar samples. Infrared spectroscopy proved that there were abundant oxygen-containing functional groups and phosphorus-containing functional groups on the surface of the biochar samples, which provided more active sites for the adsorption of pollutants.

[0067] Figure 4 The Raman spectra of biochar prepared with different addition amounts of phosphoric acid modifier were compared. The graphitization and defect degree of biochar materials with or without the addition of modifier were analyzed by Raman spectra. Regardless of whether the H3PO4 modifier was added or not, the graphitization and defect degree of biochar materials with or without the addition of modifier were significantly different at 1340 cm -1 Nearby and 1590cm -1D peak and G peak appear near the surface of the carbon atom, both of which are characteristic Raman peaks of carbon atom crystals. After adding the modifier, the ID / IG values decrease and are all less than 1, so the biochar material includes amorphous carbon and graphitized carbon, and the degree of graphitization is relatively high.

[0068] Figure 5 The following are XRD spectra of biochar prepared with different additions of the phosphoric acid modifier. X-ray diffractometer (XRD) was used to analyze the material composition and phase structure of the samples. The XRD diffraction patterns of the biochar materials are shown in the figure. Regardless of whether the modifier was added, a distinct peak appeared near 2θ = 26°, which is the diffraction peak of SiO2 (PDF#97-003-9830). With increasing additions of the phosphoric acid modifier, the SiO2 diffraction peak gradually weakened, corresponding to a higher degree of crystal graphitization in the Raman spectrum. After adding the phosphoric acid modifier, diffraction peaks appeared near 2θ = 21°, 29°, and 31° for P4 (PDF#97-015-4318), P2O5 (PDF#97-007-9698), and H3PO4 (PDF#97-001-5887), respectively.

[0069] The results showed that the addition of phosphoric acid modifier and pyrolysis carbonization of biochemical sludge were highly similar to the results presented by infrared spectra. The presence of oxygen-containing and phosphorus-containing functional groups in biochar provided more attachment sites for biochar.

[0070] Figure 6 Electron microscopic morphology of biochar materials prepared with different addition amounts of phosphoric acid modifier. Figure 6 a. Figure 6 b is the SEM image with no modifier added, magnified 5k times and 20k times respectively. Figure 6 c and Figure 6 d. Figure 6 e and Figure 6 f. Figure 6 g and Figure 6 h. Figure 6 i and Figure 6 j. Figure 6 k and Figure 6 l are SEM images magnified 5k times and 20k times when the ratio of phosphoric acid addition to biochemical sludge is 0.1:1, 0.3:1, 0.5:1, 0.7:1 and 1:1, respectively.

[0071] SEM images can provide an intuitive understanding of the surface microstructure morphology. Some significant differences between different samples are as follows: Figure 6 As shown, the magnification is 5k~20k. Figure 6 a. Figure 6 b shows that when no modifier is added, the biochar has a flaky structure and is relatively smooth. Figure 6 e- Figure 6 It can be seen from the results that after adding H3PO4 modifier, the surface of biochar becomes rough obviously and the roughness deepens with the increase of the amount of modifier added, but the pore structure is not very obvious, which is confirmed by the BET results.

[0072] In order to explore the specific surface area and pore structure of biochar prepared with different contents of phosphoric acid modifier, the specific surface area and pore structure of the obtained biochar samples were analyzed. Figure 7 This is the nitrogen adsorption-desorption isotherm of the biochar samples prepared with different addition amounts of phosphoric acid modifier. The experimental results are as follows Figure 7 shown.

[0073] At lower pressures (P / P0 < 0.1), the isotherm rises rapidly, indicating that micropore adsorption is dominant, with monolayer adsorption occurring. In the absence of H3PO4 modifier and with the addition of a small amount of H3PO4 modifier (10%), capillary coagulation begins to occur as the adsorption pressure rises (P / P0 > 0.35). As the isotherm gradually rises, the adsorption and desorption isotherms begin to deviate, creating a hysteresis loop. As shown in the figure, this hysteresis loop belongs to a Type IV isotherm, an H4-type hysteresis loop, and is characterized by mesopores. The corresponding biochar pore structure exhibits a flat slit, crack, or wedge-shaped structure. When the ratio of the added H3PO4 modifier to the biochemical sludge was 0.3:1, 0.5:1, 0.7:1, and 1:1, there was a rapid increase in gas adsorption in the low relative pressure region, which was attributed to micropore filling. The subsequent horizontal or near-horizontal platform surface was filled with micropores, and no or almost no further adsorption occurred. This is often seen in solids with relatively small micropores on the surface, such as activated carbon, molecular sieve zeolites, and certain porous oxides. From the SEM image, it can be seen that the number of micropores increased after the addition of the modifier. The results show that the addition of the H3PO4 modifier has a significant impact on the pore structure, and the shape and size of the pores have changed.

[0074] Figure 7 The nitrogen adsorption-desorption diagram of each sample after adding different amounts of phosphoric acid modifier is shown. According to the BET theory, the specific surface area values and total pore volume of the biochar samples prepared with different contents of phosphoric acid modifier are obtained, as shown in Table 2 below.

[0075] Table 2 Specific surface area, total pore volume and average pore diameter of biochar prepared with different contents of phosphoric acid modifier

[0076]

[0077] Analysis of the data in Table 2 shows that the addition of the H3PO4 modifier significantly impacts the specific surface area. Compared to biochar prepared without the addition of an activator, the SBET decreases with increasing H3PO4 modifier content. Organic acids clog the biochar's micropores during the modification process, resulting in a decrease in specific surface area. The total pore volume also exhibits a similar trend to the specific surface area. The average pore diameter of the biochar increases with increasing modifier addition, rising from 5.93 nm in the absence of the modifier to a final 10.42 nm. This is due to the pore-expanding effect of phosphoric acid.

[0078] Figure 8 The particle size distribution of biochar prepared with different addition amounts of phosphoric acid modifier was tested to explore the particle size distribution of biochar. The results are as follows Figure 8 As shown: A laser particle size analyzer was used to compare the particle sizes of biochars prepared with different amounts of added phosphoric acid modifiers. It was found that the particle sizes were mostly concentrated between 60-700 μm, and the particle size distribution of the biochar after pyrolysis was relatively uniform.

[0079] 4. Conclusion

[0080] The FT-IR infrared spectrum of the modified biochar prepared using the acidic modifier (H3PO4) shows the presence of functional groups such as P=O, POC, and P=OOH, which provide more active sites for the adsorption of pollutants. When the ratio of the modifier addition to the biochemical sludge is 0.3:1, the biochar has the largest specific surface area of 72.45 m 2 ·g -1 , the pore volume is 0.0994cm 3 ·g -1 The pore size distribution is between 2.5 and 4.3 nm, with a small amount of micropores. The SEM image shows that the surface of the biochar has obvious wrinkles, and the roughness is increased compared with the unmodified state.

[0081] Finally, the present invention explored the P removal rate of biochar prepared by phosphoric acid modifier in brewing wastewater at different adsorption times when the ratio of modifier addition to biochemical sludge was 0.3:1. The results are shown in Table 3.

[0082] Table 3 P removal rate of biochar prepared by phosphoric acid modifier at different adsorption times in brewing wastewater

[0083]

Claims

1. A method for preparing sludge-modified biochar based on phosphoric acid modification and activation, characterized in that: The following steps are involved: S1. Drying and granulation: drying the biochemical sludge to make granular dry sludge; S2, H3PO4 modification: H3PO4 modifier is mixed with dry sludge; S3, inert pyrolysis: in an inert atmosphere, the temperature is raised to 700-800°C at a constant rate and pyrolysis is carried out for several hours; S4. Acid-base washing: washing with dilute hydrochloric acid or NaOH solution until neutral, drying to obtain sludge-modified biochar containing P=O functional groups.

2. The method for preparing sludge-modified biochar based on phosphoric acid modification and activation according to claim 1, characterized in that: In the above S1, the biochemical sludge is passed through a 20-mesh sieve, dried at 100-110° C., and then crushed to 60 mesh.

3. The method for preparing sludge-modified biochar based on phosphoric acid modification and activation according to claim 2, characterized in that: In the S4, after drying, the mixture was sieved through a 60-mesh sieve to obtain a specific surface area of ≥72m 2 / g of sludge-modified biochar, the pore size of the sludge-modified biochar is 2.5-4.3nm, and the sludge-modified biochar has micropores.

4. The method for preparing sludge-modified biochar based on phosphoric acid modification and activation according to claim 1, characterized in that: In the S3, the temperature was raised to 750° C. at a rate of 5° C. / min under a nitrogen atmosphere, and pyrolysis was performed for 4 hours.

5. The method for preparing sludge-modified biochar based on phosphoric acid modification and activation according to claim 1, characterized in that: The concentration of the dilute hydrochloric acid is 10%, and the concentration of the NaOH solution is 0.1 mol / L.

6. The method for preparing sludge-modified biochar based on phosphoric acid modification and activation according to claim 1, characterized in that: The ratio of the phosphoric acid modifier to the dried sludge is 0.1:1 to 1:

1.

7. A sludge-modified biochar based on phosphoric acid modification and activation, characterized by: The sludge-modified biochar is prepared by the method according to any one of claims 1 to 6.

8. The sludge-modified biochar based on phosphoric acid modification and activation according to claim 7 is used alone or in combination with other wastewater purification reagents for the purification of brewing wastewater.

9. The sludge-modified biochar based on phosphoric acid modification and activation according to claim 8 is used to adsorb phosphorus in brewery wastewater, with an addition amount of 15 g / L, pH = 6, temperature of 20°C, and time of 80 min, and a phosphorus removal rate of ≥67.15%.

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