Sludge treatment method for stabilizing heavy metals in sludge by hydrothermal combined stabilizer

Abstract

The invention discloses a sludge treatment method for stabilizing heavy metals in sludge by a hydrothermal combined stabilizer, and belongs to the technical field of environmental protection. According to the method, the sludge is treated through the combination of the stabilizer and the hydrothermal reaction, the leaching rate and mobility of all the heavy metals in a solid-phase product are reduced, the concentration of all the heavy metals in a water phase is reduced, and an unexpected synergistic interaction technical effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a sludge treatment method using a hydrothermal combined stabilizer to stabilize heavy metals in the sludge. Background Art

[0002] Hazardous waste refers to solid waste with hazardous characteristics that is listed in the "National Hazardous Waste List" or identified according to the national hazardous waste identification standards and identification methods. "Hazardous waste sludge" usually includes wastewater treatment sludge, waste oil sludge, waste acid and alkali sludge and other waste residues containing toxic components that are generated in industrial production processes or formed in other treatment activities and contain hazardous substances or heavy metals and other harmful components. Hazardous waste sludge is a mixture formed by the combination of various hydrocarbons, water, heavy metals and solid particles. It contains a large amount of toxic and harmful compounds (benzene, polycyclic aromatic hydrocarbons, etc.), heavy metals (Hg, Cu, Cr, Zn, etc.), bacteria, parasites, etc. If it is discharged directly without treatment, it will cause serious harm to soil, water sources and human health.

[0003] Aluminum oxidation sludge is a type of hazardous waste sludge, most of which is produced by aluminum anodizing process. Aluminum anodizing is the process of placing aluminum and its alloys in corresponding electrolytes (such as sulfuric acid, chromic acid, oxalic acid, etc.) as anodes, and electrolyzing them under specific conditions and external current. The wastewater generated in this process is treated by traditional flocculation process to produce aluminum oxidation sludge. Aluminum oxidation sludge is classified as hazardous waste sludge because of excessive toxicity of nickel and chromium leaching. High levels of nickel and chromium in sludge will have a huge impact on plant metabolism and growth after entering the soil environment. At the same time, they may migrate in various environmental media and accumulate in organisms through the food chain, eventually endangering human health. How to effectively control the environmental risks of heavy metals in aluminum oxidation sludge is a major problem currently encountered.

[0004] Municipal sludge is a by-product of urban sewage treatment, mainly composed of microbial cells, organic debris, inorganic particles, etc., with high water content and high organic matter content. According to the different locations of sludge production, municipal sludge can be divided into primary sedimentation tank sludge, secondary sedimentation tank sludge, etc. Primary sedimentation tank sludge generally refers to the sludge discharged from the bottom of the tank after treatment in the primary sedimentation tank, which is mainly particulate matter and inorganic matter in sewage; secondary sedimentation tank sludge refers to the sludge discharged after treatment and sedimentation by the activated sludge method, which is mainly microorganisms and microbial metabolites. Municipal sludge contains a wide variety of heavy metals with high concentrations, which greatly limits the resource utilization of sludge. It needs to be reasonably treated and stabilized to reduce the environmental risks of heavy metals.

[0005] Many hazardous waste sludges and municipal sludges have accumulated a large amount of heavy metals, which pose a huge potential hazard to the environment and require efficient stabilization treatment. Hydrothermal liquefaction technology is a promising sludge resource treatment technology that can convert organic matter in municipal sludge into biomass oil. However, there is a risk of heavy metals in sludge being released.

[0006] Therefore, there is still an urgent need for a sludge treatment method with low heavy metal content in the treated liquid phase product, high stability of heavy metals in the treated sludge, and low leaching rate of heavy metals in the treated sludge. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions.

[0008] A method for treating sludge comprises the following steps:

[0009] Step (A): mixing sludge and a stabilizer to obtain a mixture; heating the obtained mixture under sealed conditions for reaction; wherein the sludge is wet sludge; the sludge is a mixture of municipal sludge and hazardous waste sludge;

[0010] Step (B): After the reaction in step (A) is completed, the reactant is obtained and filtered to obtain an aqueous phase product and a filter cake.

[0011] In some embodiments, the stabilizer includes at least one of calcium salts, potassium salts, sodium salts, aluminum salts, ferrous salts, oxides, hydroxides, sulfides, silicates, carbonates, and phosphates.

[0012] In some embodiments, the stabilizer includes at least one of calcium oxide, KH2PO4, FeSO4, Al2O3, Ca(OH)2, magnesium hydroxide, Na2CO3, NaOH, Na2S, Na2HPO4, NaH2PO4, and sodium citrate.

[0013] In some preferred embodiments, the stabilizer is at least one of calcium oxide, KH2PO4, magnesium hydroxide, and NaH2PO4. In some more preferred embodiments, the stabilizer is calcium oxide and KH2PO4.

[0014] In some embodiments, the mass ratio of calcium oxide to KH2PO4 is 1:10-10:1. In some embodiments, the mass ratio of calcium oxide to KH2PO4 is 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1. In some preferred embodiments, the mass ratio of calcium oxide to KH2PO4 is 1:3-3:1.

[0015] In some embodiments, the hazardous waste sludge includes at least one of aluminum oxidation sludge, electroplating sludge, and other industrial sludges with hazardous waste characteristics.

[0016] In some embodiments, the solid content of the sludge is 0.5wt%-30.0wt%. In some preferred embodiments, the solid content of the sludge is 10.0wt%-20.0wt%.

[0017] In some embodiments, the dry mass ratio of municipal sludge to hazardous waste sludge in the mixed sludge is 1:10-10:1. In some embodiments, the dry mass ratio of municipal sludge to hazardous waste sludge in the mixed sludge is 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1. In some preferred embodiments, the dry mass ratio of municipal sludge to hazardous waste sludge in the mixed sludge is 1:1.

[0018] In some embodiments, the mass ratio of the dry mass of the sludge to the stabilizer is 100:5-100:30. In some embodiments, the mass ratio of the dry mass of the sludge to the stabilizer is 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, 100:15, 100:16, 100:17, 100:18, 100:19, 100:20, 100:21, 100:22, 100:23, 100:24, 100:25, 100:26, 100:27, 100:28, 100:29 or 100:30.

[0019] In some embodiments, the reaction temperature of the heating reaction is 250° C.-360° C. In some embodiments, the reaction temperature of the heating reaction is 250° C., 260° C., 270° C., 280° C., 290° C., 300° C., 310° C., 320° C., 330° C., 340° C., 350° C. or 360° C. In some preferred embodiments, the reaction temperature of the heating reaction is 300° C.

[0020] In some embodiments, the reaction time of the heating reaction is at least 5 min. In some embodiments, the reaction time of the heating reaction is at least 10 min, at least 20 min, at least 30 min, at least 40 min, at least 50 min, at least 60 min. In some embodiments, the reaction time of the heating reaction is 60 min-600 min. In some embodiments, the reaction time of the heating reaction is 60 min, 100 min, 150 min, 200 min, 300 min, 400 min, 500 min or 600 min.

[0021] In some embodiments, the treatment method further includes step (C): mixing the filter cake obtained in step (B) with an organic solvent; ultrasonicating and filtering to obtain a filtrate and a filter residue, removing the organic solvent from the filtrate obtained in step (C) to obtain biomass oil; and drying the filter residue obtained in step (C) to obtain a solid phase product.

[0022] In some embodiments, the organic solvent includes at least one of acetone, ethanol, dichloromethane, hexane, and toluene.

[0023] In some embodiments, in step (C), every 1 g of the filter cake is mixed with 20 ml-50 ml of the organic solvent. In some embodiments, in step (C), every 1 g of the filter cake is mixed with 20 ml, 30 ml, 40 ml or 50 ml of the organic solvent.

[0024] In some embodiments, the removing of the organic solvent from the filtrate obtained in step (C) comprises using nitrogen blowing to remove the organic solvent.

[0025] Beneficial Effects

[0026] Compared with the prior art, a certain embodiment of the present invention has at least one of the following beneficial effects:

[0027] (1) It can be seen from the above results that, compared with treating municipal sludge alone or treating aluminum oxide sludge alone, the present invention mixes municipal sludge and aluminum oxide sludge for post-treatment, which greatly increases the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, and greatly reduces the leaching rate and mobility of each heavy metal in the solid phase product, which has an unexpected synergistic technical effect.

[0028] (2) It can be seen from the above results that, compared with the use of a stabilizer alone or a hydrothermal treatment alone, the present invention uses both a stabilizer and a hydrothermal treatment to treat sludge, which greatly increases the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, greatly reduces the leaching rate and mobility of each heavy metal in the solid phase product, and greatly reduces the concentration of each heavy metal in the aqueous phase, which has an unexpected synergistic technical effect.

[0029] (3) It can be seen from the above results that, compared with the use of a single stabilizer, the preferred combination of calcium oxide and KH2PO4 in the present invention is more conducive to greatly increasing the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, and is more conducive to reducing the leaching rate and mobility of each heavy metal in the solid phase product, and is more conducive to reducing the concentration of each heavy metal in the aqueous phase, which has an unexpected synergistic technical effect.

[0030] Terminology

[0031] In the description of the present invention, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0032] The term "room temperature" means ambient temperature, referring to a temperature between about 10°C and about 30°C, or between about 20°C and 30°C, or about 25°C.

[0033] The term "wt%" means percent by mass.

[0034] The term "W / W" means mass ratio.

[0035] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0036] In the following, all numbers disclosed herein are approximate, regardless of whether the word "about" or "approximately" is used. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15% or 20%. Whenever a number with a value of N is disclosed, any number with a value of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15% or N+ / -20% will be explicitly disclosed, where "+ / -" means plus or minus. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, some non-limiting embodiments are further disclosed below to further describe the present invention in detail.

[0038] The reagents used in the present invention can be purchased from the market or prepared by the method described in the present invention.

[0039] 1. Sources of reagents and raw materials

[0040] The sources of some reagents and raw materials used in the embodiments or comparative examples of the present invention are as follows:

[0041] Aluminum oxidation sludge was sampled from Ningbo Kono Precision Technology Co., Ltd. The source of the enterprise's wastewater is aluminum anodizing, and the wastewater treatment process is a flocculation treatment process using PAM flocculant.

[0042] Municipal sludge was sampled from the domestic sewage treatment plant in Jiangdong District, Ningbo. 2 / O sewage treatment process, with a daily water treatment capacity of approximately 100,000 tons.

[0043] The above aluminum oxide sludge and municipal sludge were both taken from the return section of the secondary sedimentation tank. After the sludge was taken back to the laboratory, it was passed through a 24-mesh sieve to remove large suspended particles, and then part of the sludge was freeze-dried, ground and mixed evenly, and stored in a dryer for the physical and chemical properties of the two sludges, as shown in the following table.

[0044]

[0045] 2. Product related performance measurement methods

[0046] 1. Detection method of heavy metal content in water phase:

[0047] After extraction, the aqueous phase sample was diluted to 100 mL in a volumetric flask, and the concentrations of five heavy metal elements, Cu, Zn, Ni, Cr and Mn, were determined using a high-efficiency inductively coupled plasma optical emission spectrometer (ICP-OES).

[0048] 2. Detection method of heavy metal content in solid phase and oil phase:

[0049] 2.1 Sample processing method:

[0050] (1) Weigh an appropriate amount of solid or oily sample into a polytetrafluoroethylene beaker, moisten it with 1 mL of deionized water in a fume hood, add 10 mL of nitric acid (concentration 32.5%-34%), insert a triangular funnel into the bottle mouth, and heat it on a hot plate for 10 min.

[0051] (2) After cooling, add 5 mL of nitric acid and heat for 30 min. The brown-yellow smoke is produced by nitric acid oxidizing the sample.

[0052] (3) Repeat step (2), adding 5 mL of nitric acid each time, until no brown smoke is produced.

[0053] (4) After cooling, add a small amount of deionized water and hydrogen peroxide and heat to carry out peroxidation reaction.

[0054] (5) Continue to add 1 mL of hydrogen peroxide each time until the reaction is no longer violent (note that the total amount of hydrogen peroxide added should not exceed 10 mL).

[0055] (6) After cooling, add 10 mL of hydrochloric acid, cover with a glass watch glass, and heat for 15 min.

[0056] (7) After cooling, add 40 mL of deionized water and heat to boil until the solution remains at 10 mL.

[0057] (8) The treated sample is filtered and diluted to a 50 mL volumetric flask with deionized water for testing.

[0058] 2.2 Sample determination method:

[0059] The concentrations of five heavy metal elements, Cu, Zn, Ni, Cr and Mn, were determined by inductively coupled plasma optical emission spectrometry after atmospheric pressure digestion according to standard CJ / T221-2005 using a high-efficiency inductively coupled plasma optical emission spectrometer (ICP-OES). The heavy metal concentrations were calculated using the following formula (1):

[0060]

[0061] In the formula: Wi is the concentration of the heavy metal to be measured, mg / kg; C is the heavy metal value found on the standard curve, mg / L; C0 is the heavy metal value in the blank test on the standard curve, mg / L; m is the mass of the weighed sample, g; V is the fixed volume of the test solution, mL; f is the water content, %.

[0062] 3. Detection method of heavy metal leaching rate (leaching toxicity) in solid products:

[0063] The TCLP (Toxicity Characteristic Leaching Procedure) leaching method was used to determine the toxicity of heavy metal leaching. The specific steps are as follows:

[0064] Add 0.5g of solid sample to a 50mL beaker, add 9.65mL of deionized water, stir for 5min, and measure the pH of the solution. When the pH of the solution is less than 5, use extractant 1 (dissolve 5.7mL of acetic acid in 500mL of deionized water, add 64.3mL of 1mol / L NaOH, dilute to 1L, and adjust the pH value with 1mol / L HNO3 or 1mol / L NaOH to keep the pH of the extractant at 4.39±0.05). When the pH of the solution is greater than 5, use extractant 2 (dilute 5.7mL of acetic acid to 1L with deionized water to keep the pH of the solution within the range of 2.88±0.05). After determining the extractant to be used, take 0.2 g of sample into 4 mL of extract solution (solid-liquid ratio of 1:20), oscillate at 150 rpm for 18 h at room temperature, and filter the solution through a 0.45 μm filter membrane. The filtrate obtained is used to measure the heavy metal leaching concentration using a high-efficiency inductively coupled plasma emission spectrometer. The leaching rate is calculated according to formula (2). In this paper, the leaching rate is used as the main parameter for judging leaching toxicity.

[0065] Ri=(Bi / Wi)×100% formula (2);

[0066] Where: Ri is the leaching rate, %; Bi is the leaching concentration, mg / kg; Wi is the heavy metal concentration in the solid phase, mg / kg.

[0067] 4. Heavy metal form analysis:

[0068] At present, the most widely used methods for determining the occurrence forms of heavy metals are the Tessier method and the BCR method. This paper adopts the improved BCR continuous extraction method for heavy metal form analysis and detection, and divides the forms of heavy metals into four types, including exchangeable state, carbonate-bound state (F1), reducible state (F2), oxidizable state (F3) and residual state (F4). The toxicity is ranked as F1>F2>F3>F4. F1 has the strongest migration ability and the stronger biological toxicity, followed by F2 and F3. F4 is the most stable and not easily bioavailable. The specific experimental operation steps are as follows:

[0069] (1) Acid soluble / exchangeable fraction (F1, exchangeable metal and carbonate related fraction): The sludge and solid phase product (0.5 g) were introduced into a 50 mL centrifuge tube containing 20 mL of acetic acid (0.1 mol / L), and then shaken at room temperature for 16 h. The solution and solid phase were separated by centrifugation at 4000 rpm for 20 min. Subsequently, the suspension was filtered through a 0.45 μm membrane filter, the filtrate was tested, and the solid residue was saved for subsequent extraction.

[0070] (2) Reducible fraction (F2, fraction associated with iron and manganese oxides): The residue from step (1) was shaken for 16 h with 20 mL of 0.1 mol / L hydroxylammonium chloride (adjusted to pH = 2 with nitric acid). The liquid phase and the solid phase were separated by centrifugation at 4000 rpm for 20 min. The suspension was filtered through a 0.45 μm membrane filter, the filtrate was tested, and the solid residue was saved for subsequent extraction.

[0071] (3) Oxidizable fraction (F3, fraction bound to organic matter): Add 5 mL of hydrogen peroxide (30%) to the residue from step (2) and digest at room temperature for 1 h with occasional shaking. Introduce 5 mL of hydrogen peroxide again and digest in a 358K (84.85°C) water bath for 1 h. Evaporate the contents to 1-2 mL.

[0072] About 25 mL of ammonium acetate (1.0 mol / L, adjusted to pH 2 with nitric acid) was added to the residue, and then shaken at room temperature for 16 h. The solution and solid phase were separated by centrifugation at 4000 rpm for 20 min. The suspension was filtered through a 0.45 μm membrane filter, and the filtrate was tested.

[0073] (4) Residual fraction (F4, residue state): calculated by subtracting the total concentration difference.

[0074] The filtrate generated by F1-F3 was made up to 25 mL with deionized water, and the concentrations of Cu, Zn, Cr, Mn and Ni in the resulting solution were determined using a high-performance inductively coupled plasma emission spectrometer.

[0075] Comparative Example 1: Treatment of Municipal Sludge

[0076] Take municipal sludge and prepare biomass oil and treat municipal sludge according to the following operations:

[0077] (1) Mixing sludge with a solid content of 20% with a stabilizer, wherein the sludge is municipal sludge, and heating the mixture at 300° C. for 60 minutes under sealed conditions; the stabilizer is calcium oxide; and the dry weight ratio of the stabilizer to the municipal sludge is 15:100;

[0078] (2) After the reaction in step (1) is completed, the mixture is cooled to room temperature, the sealing condition is removed to release the gas (gas phase product), and the reactant (solid-liquid mixture) is obtained, and the mixture is filtered (the filtrate obtained after filtration in step (2) is the aqueous phase product) to obtain a filter cake;

[0079] (3) Mixing the filter cake obtained in step (2) with acetone, mixing 1 g of the filter cake with 40 mL of the acetone; ultrasonicating for 30 min, filtering to obtain a filtrate and a filter residue, blowing nitrogen at 50° C. the filtrate obtained in step (3) to remove acetone in the filtrate to obtain biomass oil (also known as oil phase product); drying the filter residue at 65° C. for 2 h to obtain treated sludge (also known as solid phase product).

[0080] Comparative Example 2: Treatment of Aluminum Oxidation Sludge

[0081] Take the aluminum oxide sludge and treat it as follows:

[0082] (1) Mixing sludge with a solid content of 20% with a stabilizer, wherein the sludge is aluminum oxide sludge, and heating the mixture at 300° C. for 60 minutes under sealed conditions; the stabilizer is calcium oxide; and the dry weight ratio of the stabilizer to the municipal sludge is 15:100;

[0083] (2) After the reaction in step (1) is completed, the mixture is cooled to room temperature, the sealing condition is removed to release the gas, and the reactants (solid-liquid mixture) are obtained. The reactants are filtered (the filtrate obtained after filtration in step (2) is the aqueous phase product) to obtain the treated sludge (solid phase product).

[0084] Example 1: Treatment of mixed sludge of municipal sludge and aluminum oxidation sludge

[0085] The municipal sludge in Comparative Example 1 was replaced by a mixed sludge of municipal sludge: aluminum oxidation sludge = 1:1 (W / W), and the solid content of the mixed sludge was 20%. The remaining operations were the same as those in Comparative Example 1.

[0086] Example 2-Example 8: Stabilizer Investigation

[0087] The selection of the stabilizer was examined based on the operation of Example 1, and the stabilizer in Example 1 was replaced with a stabilizer in Table 1 of the same mass.

[0088] Table 1: Investigation of stabilizers

[0089] Example Stabilizer Example 2 <![CDATA[KH2PO4]]> Example 3 <![CDATA[Calcium oxide and KH2PO4 with a mass ratio of 1:1]]> Example 4 <![CDATA[Calcium oxide and KH2PO4 with a mass ratio of 3:1]]> Example 5 <![CDATA[Calcium oxide and KH2PO4 with a mass ratio of 1:3]]> Example 6 Calcium hydroxide Example 7 Magnesium hydroxide Example 8 <![CDATA[NaH2PO4]]>

[0090] Comparative Example 3-Comparative Example 5: Investigation of mixed sludge treatment methods

[0091] Comparative Example 3: Based on the treatment method of Example 1, no stabilizer is added, and the remaining operations are the same as Example 1.

[0092] Comparative Example 4: Based on the treatment method of Example 1, the hydrothermal reaction temperature was changed to 25°C (ie, no hydrothermal reaction occurred), and the remaining operations were the same as Example 1.

[0093] Comparative Example 5 (control): Based on the treatment method of Example 1, no stabilizer was added, the hydrothermal reaction temperature was changed to 25° C. (ie, no hydrothermal reaction occurred), and the remaining operations were the same as Example 1.

[0094] Test Example 1: Treatment Effect Detection

[0095] Detection: The yield ratio of the solid phase product, aqueous phase product, oil phase product, and gas phase product of each embodiment was detected (the results are shown in Table 2), the heavy metal concentration in the aqueous phase product (the results are shown in Table 3), the leaching toxicity of heavy metals in the solid phase product (the results are shown in Table 4), the proportion of specific heavy metals in the solid phase product in the total amount of the specific heavy metals (see Tables 5-6), and the heavy metal form distribution of each heavy metal in the solid phase product (see Table 7).

[0096] Table 2: Mass ratio of each phase product

[0097]

[0098]

[0099] Table 3: Heavy metal concentrations in aqueous products

[0100]

[0101]

[0102] Table 4: Heavy metal leaching rate in solid products

[0103]

[0104]

[0105] Table 5: Proportion of specific heavy metals in the solid phase product in the total amount of the specific heavy metals

[0106]

[0107] Table 6: Proportion of specific heavy metals in the solid phase product in the total amount of the specific heavy metals

[0108]

[0109] Table 7: Distribution of heavy metal forms of each heavy metal in the solid phase product

[0110]

[0111]

[0112]

[0113]

[0114] Result analysis:

[0115] (1) It can be seen from the above results that, compared with treating municipal sludge alone or treating aluminum oxide sludge alone, the present invention mixes municipal sludge and aluminum oxide sludge for post-treatment, which greatly increases the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, and greatly reduces the leaching rate and mobility of each heavy metal in the solid phase product, which has an unexpected synergistic technical effect.

[0116] (2) It can be seen from the above results that, compared with the use of a stabilizer alone or a hydrothermal treatment alone, the present invention uses both a stabilizer and a hydrothermal treatment to treat sludge, which greatly increases the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, greatly reduces the leaching rate and mobility of each heavy metal in the solid phase product, and greatly reduces the concentration of each heavy metal in the aqueous phase, which has an unexpected synergistic technical effect.

[0117] (3) It can be seen from the above results that, compared with the use of a single stabilizer, the preferred combination of calcium oxide and KH2PO4 in the present invention is more conducive to greatly increasing the proportion of each specific heavy metal in the solid phase product in the total amount of the specific heavy metal, and is more conducive to reducing the leaching rate and mobility of each heavy metal in the solid phase product, and is more conducive to reducing the concentration of each heavy metal in the aqueous phase, which has an unexpected synergistic technical effect.

[0118] The method of the present invention has been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein within the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention.

Claims

1. A method for treating sludge, characterized in that: The following steps are involved: Step (A): mixing sludge and a stabilizer to obtain a mixture; heating the obtained mixture under sealed conditions for reaction; wherein the sludge is wet sludge; the sludge is a mixture of municipal sludge and hazardous waste sludge; Step (B): After the reaction in step (A) is completed, the reactant is obtained and filtered to obtain an aqueous phase product and a filter cake.

2. The treatment method according to claim 1, wherein the stabilizer comprises at least one of calcium salts, potassium salts, sodium salts, aluminum salts, ferrous salts, oxides, hydroxides, sulfides, silicates, carbonates, and phosphates.

3. The treatment method according to claim 2, wherein the stabilizer comprises at least one of calcium oxide, KH2PO4, FeSO4, Al2O3, Ca(OH)2, magnesium hydroxide, Na2CO3, NaOH, Na2S, Na2HPO4, NaH2PO4, and sodium citrate.

4. The treatment method according to any one of claims 1 to 3, wherein the stabilizer is at least one of calcium oxide, KH2PO4, magnesium hydroxide, and NaH2PO4; or The stabilizer is calcium oxide and KH2PO4; and / or The mass ratio of calcium oxide to KH2PO4 is 1:10-10:1, preferably 1:3-3:1; and / or The hazardous waste sludge includes at least one of aluminum oxidation sludge, electroplating sludge, and other industrial sludges with hazardous waste characteristics.

5. The treatment method according to any one of claims 1 to 4, wherein the solid content of the sludge is 0.5wt%-30.0wt%, preferably 10.0wt%-20.0wt%.

6. According to the treatment method according to any one of claims 1 to 5, the dry mass ratio of municipal sludge to hazardous waste sludge in the mixed sludge is 1:10-10:1 or 1:

1.

7. The treatment method according to any one of claims 1 to 6, wherein the mass ratio of the dry mass of the sludge to the stabilizer is 100:5-100:30; and / or The reaction temperature of the heating reaction is 250°C-360°C, preferably 300°C; and / or The reaction time of the heating reaction is at least 5 minutes.

8. The treatment method according to any one of claims 1 to 7, further comprising step (C): mixing the filter cake obtained in step (B) with an organic solvent; ultrasonicating and filtering to obtain a filtrate and a filter residue, removing the organic solvent from the filtrate obtained in step (C) to obtain biomass oil; and drying the filter residue obtained in step (C) to obtain a solid phase product.

9. The treatment method according to claim 8, wherein in step (C), every 1g of the filter cake is mixed with 20ml-50ml of the organic solvent.

10. The treatment method according to any one of claims 8 to 9, wherein the removing the organic solvent from the filtrate obtained in step (C) comprises using nitrogen blowing to remove the organic solvent.

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