Method for preparing biochar from sludge

Abstract

The invention provides a method for preparing biochar from sludge. The method comprises the following steps: step 1, mixing sludge and slag to obtain a first mixture; 2, adding an activating agent into the first mixture, and mixing to obtain a second mixture; 3, heating the second mixture to a first temperature at a first heating rate under the condition of air isolation, and keeping the first temperature for a first time period; and 4, cooling the product obtained in the step 3, and crushing to obtain the biochar. The pore volume of the biochar is in a range of 0.1-1.5 cm < 3 > / g, the specific surface area is in a range of 75-1200 m < 2 > / g, and the number of Lewis acid sites is 20-300 [mu] mol / g.

Description

Technical Field

[0001] This application belongs to the technical field of environmental engineering, and relates to a method for preparing biochar from sludge, and particularly to a method for preparing biochar by using sludge and slag. Background Art

[0002] With the development of the economy, the treatment volume of urban sewage and industrial sewage has been continuously increasing, which has led to a growing sludge output. Sludge has a complex composition, containing a large number of harmful components such as parasite eggs, pathogenic bacteria, organic debris, heavy metals, etc., and is prone to corruption and odor, resulting in a decline in environmental quality and posing potential hazards to people's living health. Sludge reduction and harmless treatment are important issues and major challenges faced by current sewage treatment plants. In recent years, a favored way to treat sludge is to make biochar from sludge to achieve the resource utilization of sludge. Biochar is a good environmental remediation material due to its large specific surface area, rich surface groups, and high contents of elements such as nitrogen, phosphorus, and potassium. At the same time, based on the porous adsorption performance of biochar, biochar is also used to condition sludge and make it participate in the sludge dewatering process to achieve the effect of "treating waste with waste". Nevertheless, there are still many challenges in making biochar from sludge. For example, the high moisture content of sludge increases the energy consumption for biochar preparation, the yield of biochar made from sludge is low, and the chemical properties of the prepared biochar are limited, etc. Among these problems, the chemical properties of biochar are the most prominent. To solve these problems, various studies have been carried out. For example, many activators have been developed to improve the biochar prepared from sludge, and these activators include potassium hydroxide, zinc chloride, phosphoric acid, etc. However, the functions of these activators are limited to the regulation of the pore size distribution and specific surface area of biochar, and have limited effects on improving chemical properties such as surface activity. This makes the biochar prepared by these activators unable to meet the increasingly diverse application requirements and higher production requirements. For example, when the biochar prepared by these activators is used for sludge dewatering, the biochar cannot efficiently obtain dewatered sludge. For example, the ability of these biochars to catalytically condition sludge with ozone is limited, and the activity of some biochars is even insufficient to participate in this reaction. Therefore, new activators and methods are still needed to continuously improve the chemical properties of biochar, such as surface active sites, to improve the surface chemical activity of biochar, thereby expanding the application scenarios of biochar prepared from sludge. Summary of the Invention

[0003] For the above reasons, the inventors have conducted in-depth and extensive research. The inventors unexpectedly found that adding slag to sludge to prepare biochar can significantly improve the performance of biochar. Based on this, this application provides a new method for manufacturing biochar from sludge.

[0004] In one embodiment, a method for preparing biochar from sludge is provided, and the method includes:

[0005] Step 1: Mix the sludge and the slag to obtain a first mixture;

[0006] Step 2: Add an activator to the first mixture and mix to obtain a second mixture;

[0007] Step 3: Heat the second mixture to a first temperature at a first heating rate in the absence of air and maintain it at this first temperature for a first period of time;

[0008] Step 4: Cool the product of Step 3 and crush it to obtain biochar,

[0009] wherein the pore volume of the biochar is in the range of 0.1 - 1.5 cm 3 / g, and the specific surface area is in the range of 75 - 1200 m 2 / g (square meters per gram), and the number of Lewis acid sites is in the range of 20 - 300 μmol / g (micromoles per gram).

[0010] In one embodiment, the sludge is selected from at least one of municipal sludge and oily sludge.

[0011] In one embodiment, the sludge is dehydrated.

[0012] In one embodiment, the slag is selected from silicate slag, calcareous slag, and aluminate slag.

[0013] In one embodiment, the slag contains 30 - 35 wt% SiO2, 34 - 38 wt% CaO, 0.5 - 7 wt% Fe2O3, 6 - 9 wt% MgO, and 14 - 18 wt% Al2O3.

[0014] In one embodiment, the slag is in powder form with a particle size of 200 - 400 mesh. In another embodiment, the particle size is 200 - 300 mesh. In another embodiment, the particle size is 250 - 350 mesh. In another embodiment, the particle size is 220 - 280 mesh.

[0015] In one embodiment, based on the weight of the dry matter, the ratio of the sludge to the slag is in the range of 1:99 - 1:3. In another embodiment, this ratio is in the range of 1:7 - 1:4.

[0016] In one embodiment, the activator is selected from at least one of the following: potassium hypochlorite, zinc peroxide, and potassium peroxymonosulfate.

[0017] In one embodiment, based on the weight of dry matter, the weight ratio of the activator to the dry matter of the sludge and slag is 1:99 to 1:1. In another embodiment, based on the weight of dry matter, the weight ratio of the activator to the dry matter of the sludge and slag is 1:5 to 1:3.

[0018] In one embodiment, the first heating rate is in the range of 10 - 20 °C / minute. In another embodiment, the first heating rate is in the range of 10 - 15 °C / minute.

[0019] In one embodiment, the first temperature is in the range of 600 - 800 °C. In another embodiment, the first temperature is in the range of 650 - 750 °C.

[0020] In one embodiment, the first time period is in the range of 3 - 6 hours. Preferably, the first time period is in the range of 4 - 5 hours.

[0021] In one embodiment, the cooling in step 4 includes natural cooling. In another embodiment, the cooling in step 4 is at a first cooling rate. In some embodiments, the first cooling rate is in the range of 10 - 30 °C / minute. In some other embodiments, the first cooling rate is in the range of 20 - 25 °C / minute.

[0022] In one embodiment, the comminution in step 4 is selected from at least one of the following: crushing, grinding, shearing, impact, high-pressure roller.

[0023] In one embodiment, the activator is potassium hypochlorite, the first heating rate is in the range of 10 - 20 °C / minute, the first temperature is in the range of 650 - 750 °C, and the first time period is in the range of 3.5 - 4.5 hours.

[0024] In one embodiment, the activator is zinc peroxide, the first heating rate is in the range of 10 - 20 °C / minute, the first temperature is in the range of 600 - 700 °C, and the first time period is in the range of 4 - 5 hours.

[0025] In one embodiment, the activator is potassium monopersulfate, the first heating rate is in the range of 10 - 20 °C / minute, the first temperature is in the range of 650 - 750 °C, and the first time period is in the range of 3.5 - 4.5 hours.

[0026] In one embodiment, the activator is in the form of a solution, and a step of removing the liquid is further included between step 2 and step 3.

[0027] In one embodiment, after step 4, it further includes the steps of washing and drying. In some embodiments, the washing is selected from at least one of water washing, acid washing, and alkali washing. In some embodiments, the drying is selected from normal temperature drying, freeze drying, high temperature drying, or a combination thereof.

[0028] The pore volume of the biochar prepared by the method described herein is in the range of 0.1 - 1.5 cm 3 / g, and the specific surface area is in the range of 75 - 1200 m 2 / g, and the number of Lewis acid sites is in the range of 20 - 300 μmol / g. Detailed Embodiments

[0029] The "ranges" disclosed herein are presented in the form of lower and upper limits. There can be one or more lower limits, and one or more upper limits. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of a particular range. All ranges that can be defined in this way include the end values and can be combined with each other, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. Additionally, if the minimum range values listed are 1 and 2, and the maximum range values 3, 4, and 5 are also listed, the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5.

[0030] In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is just an abbreviated representation of these numerical combinations.

[0031] In this application, "above" or "below" following a number includes the number itself. For example, "5 or below" means less than or equal to 5, and "7 or above" means greater than or equal to 7.

[0032] In this application, unless otherwise specified, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions.

[0033] In this application, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form new technical solutions.

[0034] In this application, unless otherwise specified, all steps mentioned herein can be carried out sequentially or randomly, but preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0035] In this application, unless otherwise specified, "including" as mentioned herein means open-ended or may also be closed-ended. For example, "including" may mean that other components not listed may also be included, or may only include the listed components.

[0036] The above expression methods are also commonly used in the art. It should be emphasized here that only some specific embodiments of the present invention are described below, and the protection scope of the present invention is not limited to these specific embodiments. The protection scope of the present invention is defined by the claims of the present invention, and may include any technical means within the scope of the claims, including but not limited to further improvements and substitutions of these specific embodiments.

[0037] Now, the method of this application will be specifically described.

[0038] In the field of sludge engineering, although some people have already made sludge into biochar, the performance of the obtained biochar is not satisfactory. The inventors of this application found that when slag is added to the raw materials, the performance of the biochar can be significantly improved.

[0039] Therefore, in one embodiment, this application provides a method for preparing biochar from sludge, and the method includes the following steps 1-4.

[0040] Step 1: Mix the sludge and slag to obtain a first mixture.

[0041] In this step, sludge and slag are provided and mixed.

[0042] In some embodiments, the sludge may be selected from at least one of municipal sludge and oily sludge. For example, in some embodiments, the sludge may be municipal sludge. In some embodiments, the sludge may be oily sludge. Preferably, the sludge is dehydrated. For example, the moisture content of the sludge does not exceed 10% by weight. Those skilled in the art know the dehydration methods of sludge. For example, ozone combined with pressure filtration dehydration can be used.

[0043] Slag refers to the granular material with a loose texture and many pores produced after quenching of the melt mainly composed of silicate formed by the reaction of impurities such as silicon dioxide and alumina in iron ore with lime during the smelting of pig iron in a blast furnace. In some embodiments, the slag may be selected from at least one of silicate slag, calcareous slag, and aluminate slag. Generally, the slag contains 30-35 wt% SiO2, 34-38 wt% CaO, 0.5-7 wt% Fe2O3, 6-9 wt% MgO, and 14-18 wt% Al2O3. For example, the slag may be S95 slag. Alternatively, the slag may be S105 slag.

[0044] In some embodiments, the slag is in the form of powder. For example, the slag may be in the form of powder with a particle size of 200-400 mesh. In some embodiments, the particle size of the slag powder is in the following ranges: 200-350 mesh, 200-300 mesh, 210-350 mesh, 210-320 mesh, 210-290 mesh, 220-280 mesh, 230-270 mesh, 240-260 mesh, 250-285 mesh, including all ranges and sub-ranges therebetween.

[0045] In some embodiments, based on the weight of dry matter, the ratio of the sludge to the slag may be 1:99-1:3. Preferably, the ratio of the sludge to the slag may be 1:7-1:4. For example, the ratio of the sludge to the slag may be 1:7, 1:6, 1:5, or 1:4.

[0046] Step 2: Add an activator to the first mixture and mix to obtain a second mixture.

[0047] In this step, an activator is added to the first mixture.

[0048] The activator can increase the pore volume of the final biochar and play a role in pore expansion, etc. In some embodiments, the activator may be selected from at least one of the following: potassium hypochlorite, zinc peroxide, potassium peroxymonosulfate. For example, in one embodiment, the activator may be potassium hypochlorite. In another embodiment, the activator may be zinc peroxide. In another embodiment, the activator may be potassium peroxymonosulfate. In the embodiments of the present application, potassium hypochlorite is particularly preferably used as the activator.

[0049] In some embodiments, based on the weight of dry matter, the weight ratio of the activator to the dry matter of the sludge and the slag is 1:99-1:1, preferably 1:5-1:3.

[0050] In some embodiments, the activator can be in the form of a solution. For example, the activator can be an aqueous solution of potassium hypochlorite. In some embodiments, the concentration of the activator solution can be an activator solution with a concentration of 3 to 8 moles per liter. For example, in the case of an aqueous solution of potassium hypochlorite, the activator can be an aqueous solution of potassium hypochlorite with a concentration of 3 to 8 moles per liter.

[0051] When the activator is in the form of a solution, a step of removing the liquid is further included between step 2 and step 3. For example, it is carried out by drying.

[0052] Step 3: Heat the second mixture to a first temperature at a first heating rate under air isolation, and maintain it at this first temperature for a first period of time.

[0053] In this step, the second mixture is pyrolyzed to prepare biochar. Specifically, this step is carried out under airtight conditions. For this purpose, step 3 can be carried out in an inert gas atmosphere. In some embodiments, step 3 can be carried out in a nitrogen atmosphere. In other embodiments, step 3 can be carried out in a helium atmosphere.

[0054] In the embodiments of the present application, the first heating rate can be in the range of 10 to 20 °C / minute. Preferably, the first heating rate can be in the range of 10 to 15 °C / minute. The first heating rate can be constant, or it can also vary within the above range.

[0055] In some embodiments, the first temperature can be in the range of 600 to 800 °C. Preferably, the first temperature can be in the range of 650 to 750 °C, or in the range of 600 to 700 °C.

[0056] In some embodiments, the first time period can be in the range of 3 to 6 hours, preferably in the range of 4 to 5 hours.

[0057] The inventors of the present application have found that when different activators are used, biochar with better performance can be obtained by correspondingly using different first heating rates, first temperatures, and first time periods. For example, when the activator is potassium hypochlorite, the first heating rate is in the range of 10 to 20 °C / minute, the first temperature is in the range of 650 to 750 °C, and the first time period is in the range of 3.5 to 4.5 hours. Another example is that when the activator is zinc peroxide, the first heating rate is in the range of 10 to 20 °C / minute, the first temperature is in the range of 600 to 700 °C, and the first time period is in the range of 4 to 5 hours. For example, when the activator is potassium peroxymonosulfate, the first heating rate is in the range of 10 to 20 °C / minute, the first temperature is in the range of 650 to 750 °C, and the first time period is in the range of 3.5 to 4.5 hours. The corresponding processes are described in more detail in the following examples.

[0058] Step 4: Cool the product of Step 3 and pulverize it to obtain biochar.

[0059] After step 3, the product of step 3 can be cooled and crushed to obtain biochar. In some embodiments, the cooling can be natural cooling. In other embodiments, the cooling can be at a first cooling rate. For example, the first cooling rate is in the range of 10 to 30 °C per minute, preferably in the range of 20 to 25 °C per minute.

[0060] In the embodiments of the present application, the crushing can be selected from at least one of the following: crushing, grinding, shearing, impact, high-pressure roller or any crushing method known in the art. For example, the crushing can be carried out by milling. The particle size of the crushed biochar can be in the range of 200 to 500 mesh. For example, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480 mesh.

[0061] Optionally, a step of washing and drying after Step 4

[0062] After step 4, the biochar can be further washed and dried. In some embodiments, the washing of the present application can be selected from at least one of water washing, acid washing, and alkali washing. For example, in one embodiment, the biochar can be first washed with deionized water, then acid washed, and then washed with deionized water again. In other embodiments, alkali washing can be carried out first, and then washed with deionized water. In some embodiments, dilute hydrochloric acid can be used for acid washing. For example, hydrochloric acid with a concentration of 2 to 4 mol / L.

[0063] The drying is, for example, freeze drying, normal temperature drying, high temperature drying or a combination thereof.

[0064] Compared with the prior art, the present application has the following beneficial effects:

[0065] 1. In addition to sludge, slag is also a waste product in industrial production. Therefore, both raw materials of the present application come from waste products in life and production, which not only reduces the production cost, but also effectively plays the role of waste recycling.

[0066] 2. The slag contains a relatively high amount of Al2O3, and these large amounts of Al2O3 can effectively increase the Lewis acid sites of the sludge biochar and improve the ability of surface hydroxyl groups to dissociate or protonate in water. This makes the biochar manufactured by the method of the present application not only have the adsorption performance of general biochar, but also be particularly suitable for conditioning sludge in combination with ozone, thereby promoting the catalytic decomposition of ozone to generate hydroxyl radicals and improving the ozone oxidation efficiency to further improve the sludge dehydration rate.

[0067] 3. During the reaction at high temperature (700 - 900 °C), a large amount of Al2O3 in the slag can react with MgO to form magnesium aluminate (MgAl2O4), which has both acidic and basic active centers. The acidic sites can catalyze the decomposition of ozone molecules, and Al in the MgAl2O4 lattice 3+ In the presence of protonated hydroxyl groups at the basic sites, an electron transfer reaction can occur with ozone molecules, thereby generating reactive oxygen free radicals such as superoxide radicals and hydroxyl radicals, further enhancing the ozone catalytic oxidation effect.

[0068] 4. Magnesium aluminate (MgAl2O4) has high mechanical strength and hydrophobicity, and can be used as a sludge skeleton construct, enhancing sludge rigidity, constructing drainage channels, reducing sludge compressibility, improving sludge filtration performance, and promoting water release during sludge pressure filtration and dehydration.

[0069] 5. The biochar of this application can be used for sludge conditioning and dehydration, thereby achieving the purpose of "treating waste with waste".

[0070] Examples

[0071] The present invention will be described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0072] In the following examples, the sludge was taken from Qingpu Wastewater Treatment Plant in Shanghai. A certain amount was placed in an oven at 105 °C for 1 - 3 h during the usage period, and then ground into powder to obtain dehydrated sludge powder. The slag powder was S95 slag powder purchased from Henan Dingnuo Purification Materials Co., Ltd., with a particle size of 325 mesh.

[0073] The measurement method of pore volume can be referred to: GB / T 21650.1 - 2008 (Determination of pore size distribution and porosity of solid materials by mercury intrusion method and gas adsorption method - Part 1: Mercury intrusion method).

[0074] The measurement method of specific surface area can be referred to: GB / T 19587 - 2017 (Determination of specific surface area of solid materials by gas adsorption BET method).

[0075] The measurement method of Lewis acid sites is as follows: The biochar sample is first dehydrated at 200 °C and a helium flow rate of 100 cm 3 / min for 1 hour, and then cooled to room temperature; the dehydrated biochar sample is spread into a thin layer (10 mg / cm 2 ); then 1 μL of pyridine is continuously injected into the thin layer of the biochar sample (10 mg / cm 2), monitor the FTIR spectra of the biochar material before and after adsorbing pyridine; calculate the integrated area of the effective peak at 1445 cm -1 to quantify the number of Lewis acid sites.

[0076] Examples 1a - 1c: Prepare biochar using potassium hypochlorite as the activator.

[0077] At room temperature, mix 10 g of dehydrated sludge powder with 50 g of slag powder. Subsequently, add an aqueous solution of potassium hypochlorite at a concentration of 4 mol / L and stir at room temperature for 6 hours. Then centrifuge at 8000 rpm for 10 minutes. After removing the supernatant, dry it at 60 °C to obtain a pretreatment product. Place this pretreatment product in a pyrolysis device (a BTF-1400C tubular furnace purchased from Anhui Beike Equipment Technology Co., Ltd.), use nitrogen as the protective gas, heat it to the first temperature shown in Table 1 below at the first heating rate shown in Table 1 below, and maintain it at this first temperature for the first time period shown in Table 1 below. After completion, cool it naturally to room temperature and grind it. Screen it with an 80-mesh sieve. Wash it with clear water and 3 mol / L dilute hydrochloric acid, and then dry it to obtain activated biochar. Test the pore volume, specific surface area, and Lewis acid sites of the obtained biochar respectively, and the results are shown in Table 1 below.

[0078] Examples 2a - 2c: Prepare biochar using zinc peroxide as the activator.

[0079] Repeat the operations of Examples 1a to 1c, except that zinc peroxide solid is used instead of potassium hypochlorite as the activator. The first heating rate, first temperature, and first time period used in Examples 2a to 2c are as shown in Table 1 below. Test the pore volume, specific surface area, and Lewis acid sites of the obtained biochar respectively, and the results are shown in Table 1 below.

[0080] Examples 3a - 3c: Prepare biochar using potassium peroxymonosulfate as the activator.

[0081] Repeat the operations of Examples 1a to 1c, except that a potassium persulfate solution with a concentration of 5 g / L is used instead of potassium hypochlorite as the activator. The first heating rate, first temperature, and first time period used in Examples 3a to 3c are as shown in Table 1 below. Test the pore volume, specific surface area, and Lewis acid sites of the obtained biochar respectively, and the results are shown in Table 1 below.

[0082] Comparative Example 1: Prepare biochar without slag

[0083] Repeat the operation of Example 1a, except that slag is not added to the reaction. Test the pore volume, specific surface area, and Lewis acid sites of the obtained biochar respectively, and the results are shown in Table 1 below.

[0084] Comparative Example 2: Prepare biochar using steel slag

[0085] Repeat the operation of Example 1a, except that 50 g of steel slag is used instead of slag. The steel slag was purchased from Shijiazhuang Yuanjing Mineral Products Co., Ltd. The pore volume, specific surface area, and Lewis acid sites of the obtained biochar were measured respectively, and the results are shown in Table 1 below.

[0086] Table 1: Preparation raw materials and process parameters of bioactive carbon

[0087]

[0088] As can be seen from the above examples and comparative examples:

[0089] a). Compared with Comparative Example 1, the method of the present application can significantly improve the pore volume, specific surface area, and Lewis acid sites of biochar. This indicates that the properties of the biochar manufactured by the method of the present application have all been improved, making it have better application prospects.

[0090] b). Among Examples 1a - 1c, 2a - 2c, and 3a - 3c, the biochar of Examples 1a and 1b is particularly superior to other examples in terms of pore volume, specific surface area, and Lewis acid sites. This proves that when potassium hypochlorite is used as the activator, it is particularly preferred to set the first heating rate in the range of 10 - 20 °C / minute, the first temperature in the range of 650 - 750 °C, and the first time period in the range of 3.5 - 4.5 hours, as described above.

[0091] c). Compared with Comparative Example 2, the biochar of Example 1a is not only significantly superior to Comparative Example 2 in terms of pore volume and specific surface area, but also the Lewis acid sites of the biochar of Example 1a are significantly higher than those of the biochar of Comparative Example 2. This shows that the biochar prepared by the method of the present application not only has the adsorption properties of general biochar, but is also particularly suitable for conditioning sludge in combination with ozone, thereby promoting the catalytic decomposition of ozone to generate hydroxyl radicals, improving the ozone oxidation efficiency, and further increasing the sludge dewatering rate.

[0092] Although the claimed subject matter has been described in accordance with various embodiments / implementations, those skilled in the art will recognize that various modifications / alterations, substitutions, deletions, and changes / variations can be made without departing from the spirit of the invention. Therefore, the scope of the claimed subject matter is intended to be defined only by the scope of the appended claims, including their equivalents.

[0093] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above - mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily with each other.

Claims

1. A method for preparing biochar from sludge, the method comprising: Step 1: Mixing sludge and slag to obtain a first mixture; Step 2: Adding an activator to the first mixture and mixing to obtain a second mixture; Step 3: Heating the second mixture to a first temperature at a first heating rate in the absence of air and maintaining at this first temperature for a first period of time; Step 4: Cooling the product of Step 3 and pulverizing it to obtain biochar, Among them, the pore volume of the biochar is in the range of 0.1 - 1.5 cm 3 / g, and the specific surface area is in the range of 75 - 1200 m 2 / g, and the number of Lewis acid sites is in the range of 20 - 300 μmol / g.

2. The method according to claim 1, wherein, wherein the sludge is selected from at least one of municipal sludge and oily sludge, preferably, the sludge is dehydrated; and / or the slag is selected from silicate slag, calcareous slag, aluminate slag; and / or the slag contains 30-35 wt% SiO2, 34-38 wt% CaO, 0.5-7 wt% Fe2O3, 6-9 wt% MgO, 14-18 wt% Al2O3; and / or the slag is in powder form with a particle size of 200-400 mesh, for example, 250-350 mesh.

3. The method according to any one of claims 1 or 2, wherein Based on the weight of dry matter, the ratio of the sludge to the slag is 1:99-1:3, preferably 1:7-1:

4.

4. The method according to any one of claims 1 to 3, wherein The activator is selected from at least one of the following: potassium hypochlorite, zinc peroxide, potassium peroxymonosulfate; and / or wherein, based on the weight of dry matter, the weight ratio of the activator to the dry matter of the sludge and the slag is 1:99-1:1, preferably 1:5-1:

3.

5. The method according to any one of claims 1-4, wherein The first heating rate is in the range of 10-20 °C / min, preferably in the range of 10-15 °C / min; and / or wherein, the first temperature is in the range of 600-800 °C, preferably in the range of 650-750 °C; and / or wherein, the first period of time is in the range of 3-6 hours, preferably in the range of 4-5 hours.

6. The method according to any one of claims 1-5, wherein The cooling in Step 4 includes natural cooling or cooling at a first cooling rate; wherein, the first cooling rate is in the range of 10-30 °C / min, preferably in the range of 20-25 °C / min.

7. The method according to any one of claims 1-6, wherein, The pulverizing in Step 4 is selected from at least one of the following: crushing, grinding, shearing, impact, high-pressure roller.

8. The method according to any one of claims 1-7, wherein, The activator is potassium hypochlorite, the first heating rate is in the range of 10-20 °C / min, the first temperature is in the range of 650-750 °C, and the first period of time is in the range of 3.5-4.5 hours; and / or The activator is zinc peroxide, the first heating rate is in the range of 10-20 °C / min, the first temperature is in the range of 600-700 °C, and the first period of time is in the range of 4-5 hours; and / or The activator is potassium peroxymonosulfate, the first heating rate is in the range of 10-20 °C / min, the first temperature is in the range of 650-750 °C, and the first period of time is in the range of 3.5-4.5 hours.

9. The method according to any one of claims 1-8, wherein, The activator is in the form of a solution, and a step of removing the liquid is further included between Step 2 and Step 3.

10. The method according to any one of claims 1-9, wherein A step of washing and drying is further included after Step 4, wherein, the washing is selected from at least one of water washing, acid washing, and alkali washing, and the drying is selected from normal temperature drying, freeze drying, high temperature drying or a combination thereof.

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