Treatment method for co-treating chromium-containing polluted soil by using waste desulfurization slag and waste organic solvent

Abstract

The invention relates to the technical field of waste treatment, in particular to a treatment method for co-treating chromium-containing polluted soil through waste desulfurization residues and a waste organic solvent, which comprises the following steps: step 1, crushing the chromium-containing polluted soil, and spraying the waste organic solvent and water in a certain proportion after treatment to ensure that the water content is 30-50% to obtain a mixture A; 2, adding a certain amount of a catalyst into the mixture A to catalyze the reaction, and uniformly stirring to obtain a mixture B; step 3, adding waste desulfurization slag into the mixture B, and uniformly stirring to obtain a mixture C; according to the harmless treatment method for the chromium-containing contaminated soil, the chromium-containing contaminated soil serves as another detoxification agent while detoxification is achieved, waste is turned into wealth, the effect of treating pollution with waste is achieved, meanwhile, the operation process is simplified, the treatment cost is reduced, and economic benefits are improved; conforming to the landfill standard becomes a problem urgently needed to be solved by technicians in the field at present.

Description

Technical Field

[0001] The invention relates to the technical field of waste disposal, and in particular to a method for co-disposing chromium-contaminated soil by using waste desulfurization slag and waste organic solvent. Background Art

[0002] Chromium and its compounds are important inorganic chemical raw materials, widely used in metallurgy, chemical industry, machinery, electronics, medicine and other industries. According to statistics, nearly 10% of my country's commodities are related to chromium salts. Heavy metal chromium, especially hexavalent chromium, is highly mobile, easy to spread, and highly carcinogenic. It is one of the three carcinogenic metals recognized by the world. Countries around the world generally list chromium pollution as a key prevention and control target.

[0003] Chromium-containing pollutants generated by industrial activities enter the environment through various pathways, some of which exist in the form of trivalent chromium, and some exist in the hexavalent form, which is more toxic and more easily migrated. According to incomplete statistics, the annual discharge of chromium-contaminated wastewater in China is 320,000 to 400,000 tons. According to the first national soil pollution survey report, the amount of hexavalent chromium-contaminated soil in my country is as high as 15 million tons. The main treatment method for chromium-contaminated soil is chemical treatment, which reduces hexavalent chromium to trivalent chromium by adding a reducing agent. Other methods include ion exchange, membrane separation, and biological methods.

[0004] The currently disclosed methods for disposing chromium-contaminated soil are as follows: First, the patent name is a solidification stabilizer and use method for chromium slag or chromium contaminated soil. The patent application date is 2021.06.25, and the patent number is CN2021107099412. This Chinese invention patent discloses the use of 0.1-0.2% of hydroquinone, 0.1-0.2% of organic amine, 2.5-3.2% of reducing agent, 0.1-0.5% of precipitant, 1.5-2.5% of clay mineral, 0.5-0.75% of alkaline regulator, and 0.5-0.75% of flocculant to stabilize and solidify chromium-contaminated soil. However, this method requires many types of reagents, has high costs, and increases the landfill capacity.

[0005] Second, the patent name is a method for harmless and resourceful treatment of chromium slag, the patent application date is 2021.12.29, and the patent number is CN2021116364737, a Chinese invention patent, which discloses the following steps: (1) pre-treating and reducing the chromium slag in sequence to obtain detoxified chromium slag; (2) pickling the detoxified chromium slag obtained in step (1) to obtain pickled detoxified chromium slag; (3) sulfiding the pickled detoxified chromium slag obtained in step (2) to obtain sulfided detoxified chromium slag; (4) using the detoxified chromium slag obtained in step (1), or the pickled detoxified chromium slag obtained in step (2), or the sulfided detoxified chromium slag obtained in step (3) for the remediation of hexavalent chromium-contaminated water or soil. However, this method is complicated to operate, and the obtained resource-based products are difficult to sell and difficult to industrialize.

[0006] Third, the patent name is a method for detoxification and stabilization of heavy metal waste, the patent application date is 2019.04.30, and the patent number is CN2019103596457, which is a Chinese invention patent. It discloses the following contents: add iron-rich cutting mud and / or organic amine salt waste residue to solid chromium-containing waste, stir evenly to obtain mixture A; b) add acid solution to mixture A, stir evenly, and place for 1 to 3 days to obtain mixture B; c) solidify and landfill mixture B. The two wastes of iron-rich cutting mud and organic amine salt waste residue can be used as reducing agents to reduce hexavalent chromium to trivalent chromium to achieve a detoxification effect: this method needs to add a large amount of organic ammonium salt to dispose of high-content hexavalent chromium. According to the latest landfill standards, the addition of a large amount of ammonium salt will cause the water-soluble salt to fail to meet the landfill standards, and the curing agent needs to be added continuously, resulting in a large increase in landfill capacity. In addition, a large amount of sulfuric acid is added in this scheme, making the overall system strongly acidic. In the later stage, alkaline substances need to be added to adjust the pH, which increases the disposal cost. Summary of the invention

[0007] The purpose of the present invention is to provide a method for treating chromium-contaminated soil, which can detoxify the chromium-contaminated soil and can also be used as a detoxifier to dispose of waste organic solvents and desulfurization slag, thereby achieving the goal of treating waste with waste. The operation is simple, the treatment cost is low, and it meets the landfill standards, thereby improving the economic benefits. The proposed method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvents is provided.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: The method for treating chromium-contaminated soil by co-disposing waste desulfurization slag and waste organic solvent comprises the following steps: Step 1: crushing the chromium-contaminated soil, spraying a certain proportion of waste organic solvent and water after the treatment to ensure that the moisture content is 30-50%, and obtaining a mixture A; Step 2: adding a certain amount of catalyst to the mixture A to catalyze the reaction, stirring evenly, to obtain a mixture B; Step 3, adding the waste desulfurization slag to the mixture B, stirring evenly, to obtain a mixture C; Step 4: Add a certain amount of cement to mixture C, the pH value rises to 7-8, and metal hydroxide precipitation is generated.

[0009] As a further description of the above technical solution: In the step 1, the chromium-contaminated soil is crushed, and it is necessary to ensure that the diameter of the crushed chromium-contaminated soil is less than 1 cm.

[0010] As a further description of the above technical solution: The waste organic solvent used in step 1 is an alcohol solvent containing ethanol and dicarboxylic acids such as oxalic acid and citric acid produced in the laboratory. The content of alcohol and dicarboxylic acid is about 40%, and the waste organic solvent is weakly acidic. The alcohol reagent of the waste organic solvent can effectively reduce hexavalent chromium. The reaction formula is as follows: 3CH 3 CH 2 OH+4H 2 CrO 4 +6H 2 SO 4 =3CH 3 COOH+2Cr 2 (SO 4 ) 3 +13H 2 O The ethanol in the waste organic solvent and the iron and sulfur in the waste desulfurization slag can reduce hexavalent chromium to achieve detoxification of chromium-containing soil. The oxalic acid in the waste organic solvent can catalytically reduce hexavalent chromium by adding a manganese ion catalyst.

[0011] As a further description of the above technical solution: The ratio of the hexavalent chromium content in the chromium-contaminated soil to the alcohol and carboxylic acid content in the waste organic solvent in the step 1 is 1:1-2. If the moisture content is insufficient, a small amount of water is added to control the moisture content to 30-50%. If the pH value is alkaline, a small amount of waste acid is added to control the pH value of the system to about 5.0.

[0012] As a further description of the above technical solution: The catalyst used in step 2 is divalent manganese ions such as manganese sulfate and manganese chloride, and the added amount is 1% of the carboxylic acid content in the waste organic solvent.

[0013] As a further description of the above technical solution: The waste desulfurization slag used in the step three refers to the waste slag produced during the pre-desulfurization treatment of molten iron before entering the converter. The desulfurization slag produced during the molten iron pretreatment contains about 30%-40% iron and about 10-20% sulfur. The total iron content and sulfur content of the waste desulfurization slag is 2-3 times the hexavalent chromium in the chromium-contaminated soil.

[0014] As a further description of the above technical solution: The waste desulfurization slag in step 3 contains more sulfur ions and ferrous ions, which dissolve faster in acidic solution. It contains a small amount of barium ions, etc., which can reduce hexavalent chromium to achieve detoxification of chromium-containing waste. The reaction formula is as follows: Cr 2 O 7 2- +6Fe 2+ +14H + →2Cr 3+ +6Fe 3+ +7H 2 O Cr 2 O 7 2- +3S 2- +14H + →2Cr 3+ +3S↓+7H 2 O Fe 2+ +2Cr 3+ +8OH - →FeCr 2 O 4 ↓+4H 2 O Ba 2+ +CrO 4 2- →BaCrO 4 ↓ Cr 3+ +3OH - →Cr(OH) 3 ↓ The iron and sulfur in the waste desulfurization slag can reduce hexavalent chromium to achieve detoxification of chromium-containing soil.

[0015] As a further description of the above technical solution: The amount of cement added in step 4: chromium-contaminated soil is 1:1-1.2.

[0016] As a further description of the above technical solution: The waste organic solvent and waste desulfurization slag can both be used to reduce hexavalent chromium separately, but using only one of them will lead to a significant increase in the amount added, using only waste organic solvent will lead to an increase in organic matter in the system, and using only waste desulfurization slag will cause the landfill to increase too much and have low economic benefits.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In the present invention, the goal of treating waste with waste is achieved by reducing hexavalent chromium by using ethanol in waste organic solvents in hazardous wastes.

[0018] 2. In the present invention, the addition of acidic organic solvent reduces the addition of water and waste acid, and the pH value is controlled at a weak acid, which reduces the addition of alkali in the later stage and reduces the disposal cost of chromium-contaminated soil.

[0019] 3. In the present invention, the reduction of hexavalent chromium by carboxylic acid compounds in waste organic solvents is completed by adding catalyst manganese ions, which fully utilizes the effective components in the waste organic solvents and provides a method for treating hexavalent chromium containing dicarboxylic acids.

[0020] 4. In the present invention, oxalic acid / ethanol is used to synergistically reduce hexavalent chromium. After oxalic acid and Cr(VI) are combined, the instability of tetrahedral Cr(VI) species caused by the ligand field effect reduces the reaction barrier of the transformation of Cr(VI) to Cr(III), thereby facilitating the electron transfer between Cr(VI) and ethanol and accelerating the reaction rate.

[0021] 5. In the present invention, the method for treating chromium-contaminated soil has simple steps, has no requirements for temperature and pressure, has high economic benefits, and can treat chromium-contaminated soil on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a data comparison table of six embodiments of the method for co-disposing chromium-contaminated soil by using waste desulfurization slag and waste organic solvents proposed in the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1 The present invention provides a technical solution: a method for treating chromium-contaminated soil by co-disposing waste desulfurization slag and waste organic solvent, comprising the following steps: The first step is to crush the chromium-contaminated soil to ensure that the diameter of the crushed chromium-contaminated soil is less than 1 cm. After the treatment, a certain proportion of waste organic solvent and water are sprayed to ensure that the water content is 30-50%, and a mixture A is obtained, wherein the ratio of the hexavalent chromium content in the chromium-contaminated soil to the alcohol and carboxylic acid content in the waste organic solvent is 1:1-2. If the water content is insufficient, a small amount of water is added to control the water content to 30-50%. If the pH value is alkaline, a small amount of waste acid is added to control the pH value of the system to be about 5.0; The waste organic solvents used are alcohol solvents such as ethanol and dicarboxylic acids such as oxalic acid and citric acid produced in the laboratory. The content of alcohols and dicarboxylic acids is about 40%, and the waste organic solvents are weakly acidic. The alcohol reagents of the waste organic solvents can effectively reduce hexavalent chromium. The reaction formula is as follows: 3CH 3 CH 2 OH+4H 2 CrO 4 +6H 2 SO 4 =3CH 3 COOH+2Cr 2 (SO 4 ) 3 +13H 2 O The ethanol in the waste organic solvent can reduce hexavalent chromium and achieve detoxification of chromium-containing soil. The oxalic acid in the waste organic solvent can catalytically reduce hexavalent chromium by adding manganese ion catalyst. The second step is to add a certain amount of catalyst to the mixture A to catalyze the reaction, stir evenly, and obtain a mixture B, wherein the catalyst is a divalent manganese ion such as manganese sulfate and manganese chloride, and the added amount is 1% of the carboxylic acid content in the waste organic solvent; The third step is to add waste desulfurization slag to the mixture B and stir evenly to obtain a mixture C, wherein the waste desulfurization slag used refers to the waste slag generated during the pre-desulfurization treatment of molten iron before entering the converter, and the desulfurization slag generated during the pretreatment of the molten iron contains about 30%-40% iron and about 10-20% sulfur, and the total amount of iron content and sulfur content of the waste desulfurization slag is 2-3 times the hexavalent chromium in the chromium-contaminated soil; In addition, the waste desulfurization slag contains more sulfur ions and ferrous ions, which dissolve faster in acidic solution. It also contains a small amount of barium ions, which can reduce hexavalent chromium and achieve detoxification of chromium-containing waste. The reaction formula is as follows: Cr 2 O 7 2- +6Fe 2+ +14H + →2Cr 3+ +6Fe 3+ +7H2 O Cr 2 O 7 2- +3S 2- +14H + →2Cr 3+ +3S↓+7H 2 O Fe 2+ +2Cr 3+ +8OH - →FeCr 2 O 4 ↓+4H 2 O Ba 2+ +CrO 4 2- →BaCrO 4 ↓ Cr 3+ +3OH - →Cr(OH) 3 ↓ The iron and sulfur in the waste desulfurization slag can reduce hexavalent chromium and achieve detoxification of chromium-containing soil.

[0025] Step 4: Add a certain amount of cement to mixture C, the pH value rises to 7-8, and metal hydroxide precipitation is produced at the same time, wherein the amount of cement added: chromium-contaminated soil is 1:1-1.2.

[0026] Specifically, waste organic solvents and waste desulfurization slag can both be used to reduce hexavalent chromium individually, but using only one of them will lead to a significant increase in the amount added. Using only waste organic solvents will lead to an increase in organic matter in the system, and using only waste desulfurization slag will cause the landfill to expand too much and have low economic benefits.

[0027] Specifically, dicarboxylic acids such as oxalic acid do not react with hexavalent chromium or react slowly, but the present invention can accelerate its reduction reaction by adding a small amount of catalyst manganese ions, effectively utilizing the carboxylic acid compounds in the waste organic solvent. This catalytic effect may be due to the formation of complex ions between Mn(II) and two carboxyl groups, which further increases the activity of a-OH, thereby reacting with a-OH to CrO 4 2- A more complex complex is formed, and the reaction rate of organic acid reduction of hexavalent chromium is accelerated.

[0028] Ethanol and oxalic acid in waste organic solvents can synergistically accelerate the conversion of hexavalent chromium to trivalent chromium. In the system of oxalic acid / ethanol reduction of Cr(VI), the activity of Cr transferring electrons to oxygen atoms or protonation is further enhanced: according to the frontier orbital theory, the smaller the band gap, the easier it is to be excited. The complex narrows the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, thereby enhancing the driving force of electron transfer between the complex and the electron donor ethanol. There is a major obstacle for the reduction of Cr(VI) to Cr(III) from tetrahedral configuration (Cr(VI) / Cr(V)) to octahedral configuration (Cr(IV) / Cr(III)). After oxalic acid and Cr(VI) are combined, the instability of tetrahedral Cr(VI) species caused by the ligand field effect may reduce the reaction barrier for the conversion of Cr(VI) to Cr(III), thereby facilitating the electron transfer between Cr(VI) and ethanol.

[0029] The solution of the present invention is further described in detail below in conjunction with implementation cases.

[0030] The test sample is a chromium-contaminated soil (leaching solution Cr 6+ : 5000mg / L, total Cr: 8000mg / L). Cr (VI) was tested by diphenylcarbazide spectrophotometry (GB / T1555.5-1995). The chromium content of the leachate meets the limit requirements in the <Hazardous Waste Landfill Pollution Control Standard> (GB 18597-2023) and is qualified.

[0031] Implementation Case 1 Weigh 1kg of chromium-contaminated soil, crush it with a crusher and sieve it, select chromium-contaminated soil with a diameter of less than 1cm for the next study, add 125mL of waste organic solvent (alcohol and dicarboxylic acid content is about 40%) to the crushed chromium-contaminated soil, add 0.5g of manganese sulfate, and then spray about 200mL of water on the soil to control the moisture content to about 40%. Then add about 10mL of inorganic waste sulfuric acid with an acidity of 0.1mol / L, control the pH value to about 5.0, mix well, add 250g of waste desulfurization slag (iron content is about 30%, sulfur content is about 10%), stir well, leave for 1 day, add 100g of cement and stir to solidify, and conduct leaching toxicity test on the solidified product.

[0032] Implementation Case 2 Weigh 1kg of chromium-contaminated soil, crush it with a crusher and sieve it, select chromium-contaminated soil with a diameter of less than 1cm for the next step of research, add 140mL of waste organic solvent (alcohol and dicarboxylic acid content is about 40%) to the crushed chromium-contaminated soil, add 0.56g of manganese sulfate, and then spray about 180mL of water on the soil to control the moisture content to about 40%. Then add about 8mL of inorganic waste sulfuric acid with an acidity of 0.1mol / L, control the pH value to about 5.0, mix well, add 300g of waste desulfurization slag (iron content is about 30%, sulfur content is about 10%), stir well, leave for 1 day, add 100g of cement and stir to solidify, and conduct leaching toxicity test on the solidified product.

[0033] Implementation Case 3 The difference from Implementation Case 1 is that waste desulfurization slag is not added, and the remaining addition amounts and proportions are the same.

[0034] Implementation Case 4 The difference from Implementation Case 1 is that no waste organic solvent is added, the amount of recycled water added is 325 mL, and then about 15 mL of inorganic waste sulfuric acid with an acidity of 0.1 mol / L is added, and the pH value is controlled to be about 5.0. The remaining addition amounts and proportions are the same.

[0035] Implementation Case 5 The difference from Example 1 is that no catalyst manganese ions are added, and the remaining addition amounts and proportions are the same.

[0036] Implementation Case 6 The difference from Example 1 is that the carboxylic acid compound in the added waste organic solvent is a monocarboxylic acid, and the remaining addition amounts and proportions are the same.

[0037] In summary, please refer to Figure 1 , which is a comparison table of data from six embodiments. From the results of implementation cases 1-2, it can be seen that the method for treating chromium-contaminated soil by co-disposing waste desulfurization slag and waste organic solvent provided by the present invention has a large treatment capacity and a lasting solidification effect. By comparing implementation cases 3-4, it can be seen that the use of waste organic solvents alone or waste desulfurization slag alone does not meet the control restrictions for hazardous waste landfill. From implementation case 5, it can be seen that the catalyst has a significant catalytic effect. Without the addition of a catalyst, the carboxylic acid compounds of the waste organic solvent cannot be fully utilized. From implementation case 6, it can be seen that monocarboxylic acids cannot effectively reduce hexavalent chromium even with the addition of a manganese catalyst. Organic acids containing only a single carboxyl group cannot form chelates with manganese ions, so, regardless of the presence or absence of manganese ions, they cannot undergo redox reactions with hexavalent chromium.

[0038] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvents, characterized in that: The following steps are involved: Step 1: crushing the chromium-contaminated soil, spraying a certain proportion of waste organic solvent and water after the treatment to ensure that the moisture content is 30-50%, and obtaining a mixture A; Step 2, adding a certain amount of catalyst to the mixture A to catalyze the reaction, stirring evenly, to obtain a mixture B; Step 3, adding the waste desulfurization slag to the mixture B, stirring evenly, to obtain a mixture C; Step 4: Add a certain amount of cement to mixture C, the pH value rises to 7-8, and metal hydroxide precipitation is generated.

2. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: In the step 1, the chromium-contaminated soil is crushed, and it is necessary to ensure that the diameter of the crushed chromium-contaminated soil is less than 1 cm.

3. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: The waste organic solvent used in step 1 is an alcohol solvent containing ethanol and dicarboxylic acids such as oxalic acid and citric acid produced in the laboratory. The content of alcohol and dicarboxylic acid is about 40%, and the waste organic solvent is weakly acidic. The alcohol reagent of the waste organic solvent can effectively reduce hexavalent chromium. The reaction formula is as follows: 3CH3CH2OH+4H2CrO4+6H2SO4=3CH3COOH+2Cr2(SO4)3+13H2O The ethanol in the waste organic solvent can reduce hexavalent chromium to achieve detoxification of chromium-containing soil, and the oxalic acid in the waste organic solvent can catalytically reduce hexavalent chromium by adding a manganese ion catalyst.

4. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 3, characterized in that: The ratio of the hexavalent chromium content in the chromium-contaminated soil to the alcohol and carboxylic acid content in the waste organic solvent in the step 1 is 1:1-2. If the moisture content is insufficient, a small amount of water is added to control the moisture content to 30-50%. If the pH value is alkaline, a small amount of waste acid is added to control the pH value of the system to about 5.

0.

5. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: The catalyst used in step 2 is divalent manganese ions such as manganese sulfate and manganese chloride, and the added amount is 1% of the carboxylic acid content in the waste organic solvent.

6. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: The waste desulfurization slag used in the step three refers to the waste slag produced during the pre-desulfurization treatment of molten iron before entering the converter. The desulfurization slag produced during the molten iron pretreatment contains about 30%-40% iron and about 10-20% sulfur. The total iron content and sulfur content of the waste desulfurization slag is 2-3 times the hexavalent chromium in the chromium-contaminated soil.

7. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1 or 6, characterized in that: The waste desulfurization slag in step 3 contains more sulfur ions and ferrous ions, which dissolve faster in acidic solution. It contains a small amount of barium ions, etc., which can reduce hexavalent chromium to achieve detoxification of chromium-containing waste. The reaction formula is as follows: Cr2O7 2- +6Fe 2+ +14H + →2Cr 3+ +6Fe 3+ +7H2O <h2 style=";text-align:left;direction:ltr">Cr2O7<h2 style=";text-align:left;direction:ltr"> 2- <h2 style=";text-align:left;direction:ltr"> +3S<h2 style=";text-align:left;direction:ltr"> 2- <h2 style=";text-align:left;direction:ltr"> +14H<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> →2Cr<h2 style=";text-align:left;direction:ltr"> 3+ <h2 style=";text-align:left;direction:ltr"> +3S↓+7H2O He 2+ +2Cr 3+ +8OH - →FeCr2O4↓+4H2O Not 2+ +CrO4 2- →BaCrO4↓ Cr 3+ +3OH - →Cr(OH)3↓ The iron and sulfur in the waste desulfurization slag can reduce hexavalent chromium to achieve detoxification of chromium-containing soil.

8. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: The amount of cement added in step 4: chromium-contaminated soil is 1:1-1.

2.

9. The method for treating chromium-contaminated soil by synergistically treating waste desulfurization slag and waste organic solvent according to claim 1, characterized in that: The waste organic solvent and waste desulfurization slag can both be used to reduce hexavalent chromium separately, but using only one of them will lead to a significant increase in the amount added, using only waste organic solvent will lead to an increase in organic matter in the system, and using only waste desulfurization slag will cause the landfill to increase too much and have low economic benefits.

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