A Stabilizing Agent for Contaminated Soil Remediation and Its Preparation Method

Abstract

The present invention relates to the technical field of soil remediation, and particularly relates to a stabilizer for contaminated soil remediation and a preparation method thereof. The stabilizer includes: modified neutralization residue a and modified neutralization residue b; the preparation method of the modified neutralization residue a includes: mixing a first part of the neutralization residue with water to obtain a suspension, reacting the suspension at 80-140 °C and a pH value of 10-12, stirring and mixing the reaction product liquid with diatomite, and after solid-liquid separation, obtaining the modified neutralization residue a; the preparation method of the modified neutralization residue b includes: mixing a second part of the neutralization residue with an alkaline material and then calcining to obtain the modified neutralization residue b; in the neutralization residue, the mass content of calcium oxide is 27%-30%, the mass content of calcium sulfate is 34%-38%, and the mass content of iron hydroxide is 16%-20%. When the stabilizer is used to treat contaminated soil, the reduction rate of the leaching concentration of lead and cadmium in the contaminated soil is greater than 80%.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and particularly relates to a stabilizing agent for contaminated soil remediation and a preparation method thereof. Background Art

[0002] Most of the components of ordinary passivators are initial raw materials, and there are many drawbacks in the process of soil remediation. For example, lime-based passivators are too alkaline, which is likely to harm the activities of microorganisms in the soil and the normal growth of crops. Long-term addition will also cause soil compaction and lack of trace nutrients. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a stabilizing agent for contaminated soil remediation and a preparation method thereof. When the stabilizing agent is used to treat contaminated soil, the reduction rate of the leaching concentration of lead and cadmium is relatively excellent.

[0004] The present invention provides a stabilizing agent for contaminated soil remediation, including: modified neutralization residue a and modified neutralization residue b;

[0005] The preparation method of the modified neutralization residue a includes the following steps:

[0006] Mix the first part of the neutralization residue with water to obtain a suspension, react the suspension at 80-140°C and a pH value of 10-12, stir and mix the reaction product liquid with diatomite, and after solid-liquid separation, obtain the modified neutralization residue a;

[0007] The preparation method of the modified neutralization residue b includes the following steps:

[0008] Mix the second part of the neutralization residue with an alkaline material and then calcine to obtain the modified neutralization residue b;

[0009] In the neutralization residue, the mass content of calcium oxide is 27%-30%, the mass content of calcium sulfate is 34%-38%, and the mass content of iron hydroxide is 16%-20%.

[0010] Preferably, the mass ratio of the modified neutralization residue a to the modified neutralization residue b is 3-6:4-7.

[0011] Preferably, in the preparation method of the modified neutralization residue a, the dosage ratio of the first part of the neutralization residue to water is 100 g:200-800 mL.

[0012] Preferably, in the preparation method of the modified neutralization residue a, after obtaining the suspension, use a sodium hydroxide solution to adjust the pH value of the suspension to 10-12;

[0013] The mass concentration of the sodium hydroxide solution is 25%-35%.

[0014] Preferably, in the preparation method of the modified neutralization slag a, the reaction time is 0.5 - 2 h;

[0015] After the reaction, it further includes: naturally cooling to room temperature.

[0016] Preferably, in the preparation method of the modified neutralization slag a, the mass ratio of the diatomite to the first - part neutralization slag is 1 - 4:10.

[0017] Preferably, in the preparation method of the modified neutralization slag a, the product liquid after the reaction and the diatomite are stirred and mixed at room temperature for 0.5 - 1.5 h;

[0018] After the solid - liquid separation, it further includes: drying the obtained solid substance; the drying temperature is 55 - 65 °C.

[0019] Preferably, in the preparation method of the modified neutralization slag b, the alkaline material includes limestone powder and / or dolomite powder;

[0020] The mass ratio of the second - part neutralization slag to the alkaline material is 6 - 9:1 - 4.

[0021] Preferably, in the preparation method of the modified neutralization slag b, the calcination temperature is 600 - 1200 °C and the time is 1.5 - 2.5 h;

[0022] After the calcination, it further includes: naturally cooling to room temperature and then grinding.

[0023] The present invention also provides a preparation method of the stabilization agent for contaminated soil remediation described above, including the following steps:

[0024] Mix the modified neutralization slag a and the modified neutralization slag b to obtain the stabilization agent for contaminated soil remediation.

[0025] The present invention provides a stabilizing agent for contaminated soil remediation, comprising: modified neutralization residue a and modified neutralization residue b; The preparation method of the modified neutralization residue a comprises the following steps: mixing a first part of the neutralization residue with water to obtain a suspension, reacting the suspension at 80-140 °C and a pH value of 10-12, stirring and mixing the reaction product liquid with diatomite, and performing solid-liquid separation to obtain the modified neutralization residue a; The preparation method of the modified neutralization residue b comprises the following steps: mixing a second part of the neutralization residue with an alkaline material and then performing calcination to obtain the modified neutralization residue b; In the neutralization residue, the mass content of calcium oxide is 27%-30%, the mass content of calcium sulfate is 34%-38%, and the mass content of iron hydroxide is 16%-20%. The stabilizing agent for contaminated soil remediation provided by the present invention has simple components and a simple preparation method, and the neutralization residue is cheap and easily available; When the stabilizing agent for contaminated soil remediation provided by the present invention is used to treat contaminated soil, the reduction rate of the leaching concentration of lead and cadmium in the contaminated soil is greater than 80%. It meets the Class III standard of the Surface Water Environmental Quality Standard GB 3838-2002. At the same time, the present invention can improve the added value of the resource utilization of the neutralization residue, reduce the storage capacity pressure of the neutralization residue precipitation, and effectively realize the organic unity of environmental protection benefits and economic benefits. Detailed implementation manners

[0026] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] The present invention provides a stabilizing agent for contaminated soil remediation, comprising: modified neutralization residue a and modified neutralization residue b;

[0028] The preparation method of the modified neutralization residue a comprises the following steps:

[0029] Mix a first part of the neutralization residue with water to obtain a suspension, react the suspension at 80-140 °C and a pH value of 10-12, stir and mix the reaction product liquid with diatomite, and perform solid-liquid separation to obtain the modified neutralization residue a;

[0030] The preparation method of the modified neutralization residue b comprises the following steps:

[0031] Mix a second part of the neutralization residue with an alkaline material and then perform calcination to obtain the modified neutralization residue b;

[0032] In the neutralization residue, the mass content of calcium oxide is 27%-30%, the mass content of calcium sulfate is 34%-38%, and the mass content of iron hydroxide is 16%-20%.

[0033] In certain embodiments of the present invention, the mass ratio of the modified neutralization slag a to the modified neutralization slag b is 3-6:4-7; specifically 5:5, 6:4 or 5:4.

[0034] In the present invention, the preparation method of the modified neutralization slag a includes the following steps:

[0035] Mix the first part of the neutralization slag with water to obtain a suspension, react the suspension at 80-140 °C and a pH value of 10-12, stir and mix the reaction product liquid with diatomite, and after solid-liquid separation, obtain the modified neutralization slag a.

[0036] In the neutralization slag of the present invention, the mass content of calcium oxide is 27%-30%, specifically 28%; the mass content of calcium sulfate is 34%-38%, specifically 35%; the mass content of iron hydroxide is 16%-20%, specifically 17%.

[0037] In certain embodiments of the present invention, the preparation method of the neutralization slag includes:

[0038] Neutralize the acidic wastewater generated from a copper sulfide mine with lime to obtain a neutralization slurry, and then obtain the neutralization slag after plate and frame filtration. The neutralization slag is a light yellow powder, and the mass ratio of particles with a particle size less than 0.045 μm is 95%-98%; specifically it can be 96%.

[0039] Before using the neutralization slag, it further includes: pretreating the neutralization slag. Specifically, it includes: drying the neutralization slag, then performing a pulverization treatment, and passing through a 20-mesh sieve.

[0040] In certain embodiments of the present invention, the dosage ratio of the first part of the neutralization slag to water is 100 g:200-800 mL; specifically 100 g:400 mL, 100 g:600 mL or 100 g:800 mL. The water is deionized water.

[0041] In certain embodiments of the present invention, the first part of the neutralization slag is stirred and mixed evenly with water to obtain a suspension.

[0042] After obtaining the suspension, use a sodium hydroxide solution to adjust the pH value of the suspension to 10-12, specifically 11; the mass concentration of the sodium hydroxide solution is 25%-35%; specifically 30%.

[0043] In certain embodiments of the present invention, the temperature of the reaction is 120 °C; the time is 0.5-2 h, specifically 1 h.

[0044] After the reaction, it further includes: naturally cooling to room temperature.

[0045] In certain embodiments of the present invention, the mass ratio of the diatomaceous earth to the first part of the neutralization slag is 1 to 4:10; specifically, it is 2:10, 3:10, or 2.5:10.

[0046] The product liquid after the reaction and the diatomaceous earth are stirred and mixed at room temperature for 0.5 to 1.5 h; specifically, it is 1 h.

[0047] In certain embodiments of the present invention, the method for solid-liquid separation is suction filtration.

[0048] After the solid-liquid separation, it further includes: drying the obtained solid substance; the temperature for drying is 55 to 65°C; specifically, it is 60°C.

[0049] In the modification process of the present invention, diatomaceous earth is added. As a modification substance, the diatomaceous earth makes the neutralization slag not easily agglomerate into blocks, and it can be better mixed with the soil during subsequent use. At the same time, adding diatomaceous earth can also improve the heavy metal adsorption capacity.

[0050] The modified neutralization slag a obtained in the present invention can obtain calcium sulfate whiskers, which can increase the specific surface area and surface free energy.

[0051] In the present invention, the preparation method of the modified neutralization slag b includes the following steps:

[0052] Mix the second part of the neutralization slag with the alkaline material and then carry out calcination to obtain the modified neutralization slag b.

[0053] In certain embodiments of the present invention, the alkaline material includes limestone powder and / or dolomite powder.

[0054] The mass ratio of the second part of the neutralization slag to the alkaline material is 6 to 9:1 to 4; specifically, it is 7:3 or 6:4.

[0055] In certain embodiments of the present invention, the temperature for calcination is 600 to 1200°C, specifically, it is 800°C; the time is 1.5 to 2.5 h, specifically, it is 2 h. The calcination is carried out in a muffle furnace.

[0056] After the calcination, it further includes: naturally cooling to room temperature and then grinding. The particle size after grinding is <2 mm.

[0057] The alkaline agent used in the present invention is a calcium-containing agent, which is mixed with the neutralization slag and then calcined again. Through the calcination, the content of the active ingredient calcium oxide increases. At the same time, the high-temperature modification synergistic effect among the components during the calcination process improves the chemical stability.

[0058] The present invention also provides a preparation method of the stabilization agent for contaminated soil remediation described above, including the following steps:

[0059] After mixing the modified neutralization slag a and the modified neutralization slag b, a stabilizing agent for contaminated soil remediation is obtained.

[0060] In some embodiments of the present invention, after the mixing, it further includes: grinding. The particle size after grinding < 2 mm.

[0061] The grinding time is 0.2 - 1 h; specifically 0.5 h.

[0062] The stabilizing agent for contaminated soil remediation provided by the present invention has simple components, a simple preparation method, and the neutralization slag is cheap and easily available; when the stabilizing agent for contaminated soil remediation provided by the present invention is used to treat contaminated soil, the reduction rate of the leaching concentration of lead and cadmium in the contaminated soil is greater than 80%. It meets the Class III standard of the Surface Water Environmental Quality Standard GB 3838 - 2002. At the same time, the present invention can increase the added value of the resource utilization of the neutralization slag, reduce the pressure on the precipitation storage capacity of the neutralization slag, and effectively realize the organic unity of environmental protection benefits and economic benefits.

[0063] In order to further illustrate the present invention, the following describes in detail a stabilizing agent for contaminated soil remediation and its preparation method provided by the present invention in combination with embodiments, but it should not be construed as a limitation to the protection scope of the present invention.

[0064] Example 1

[0065] 1. Preparation of the stabilizing agent:

[0066] 1) Preparation and pretreatment of the neutralization slag:

[0067] The acidic wastewater generated from a copper sulfide mine is neutralized with lime to obtain a neutralization slurry, and then after plate and frame filtration, a brownish-yellow powder is obtained, which is the neutralization slag; the mass ratio of the particles with a particle size less than 0.045 μm in the neutralization slag is 96%;

[0068] In the neutralization slag, the mass content of calcium oxide is 28%, the mass content of calcium sulfate is 35%, and the mass content of iron hydroxide is 17%;

[0069] The neutralization slag is dried, then pulverized, and passed through a 20-mesh sieve to obtain the pretreated neutralization slag;

[0070] 2) Weigh 100 g of the pretreated neutralization slag into a beaker, add 400 mL of deionized water and stir evenly to obtain a suspension; adjust the pH of the suspension to 11 with a 30% NaOH aqueous solution by mass concentration; then pour it into a reaction kettle and place it in an oven to react at 120 °C for 1 h. After the reaction is completed, it is naturally cooled to room temperature; add 20 g of diatomaceous earth, stir at room temperature for 1 h, then filter by suction, and dry it in an oven (60 °C) to obtain the modified neutralization slag a;

[0071] 3) Weigh 100 g of the pretreated neutralization residue and mix it with limestone powder at a mass ratio of 7:3. Calcinate it in a muffle furnace at 800 °C for 2 h. After natural cooling to room temperature, grind it (the particle size after grinding < 2 mm) to obtain the modified neutralization residue b;

[0072] 4) Mix the modified neutralization residue a and the modified neutralization residue b at a mass ratio of 5:5, and then grind for 0.5 h (the particle size after grinding < 2 mm) to obtain the stabilization agent for contaminated soil remediation.

[0073] 2. Usage effect of the stabilization agent:

[0074] 1) Soil pollution situation

[0075] The tested soil is from a heavy metal contaminated soil site in Fujian. The soil is severely contaminated by heavy metals. The sampling layer is the surface layer of 0 - 20 cm, the soil pH = 4.69 ± 0.25; the total lead content is 2060 mg / kg, the total cadmium content is 121.7 mg / kg, the lead leaching concentration is 78.5 μg / L, the cadmium leaching concentration is 46.7 μg / L, and the water content is 16%. Before use, the soil is naturally air-dried, and plant residues, gravel, etc. are selected and ground through a 10-mesh sieve for standby;

[0076] 2) Test steps

[0077] Weigh 100 g of the above-mentioned lead-cadmium contaminated soil and add it to a 500 mL beaker. Sprinkle 3 g of the prepared stabilization agent, mix and stir the two evenly, then add an appropriate amount of deionized water. During the test, keep the saturated water content of the soil at 25%; then stir evenly further, seal it with plastic wrap and make ventilation holes; Add water every 2 d to keep the water content of the system; When the curing time reaches 30 d, take out the sample for air-drying treatment and send it for inspection.

[0078] 3) Test results

[0079] The results show that the leaching concentrations of Pb and Cd in the above-mentioned contaminated soil by the stabilization agent are 15.4 μg / L and 2.9 μg / L respectively, and their reduction rates are 80.30% and 93.78% respectively. The final result shows that it meets the Class III standard of the Surface Water Environmental Quality Standard GB 3838 - 2002.

[0080] Example 2

[0081] 1. Preparation of the stabilization agent:

[0082] 1) Preparation and pretreatment of the neutralization residue:

[0083] The acidic wastewater generated from a copper sulfide mine is neutralized with lime to obtain a neutralized slurry, which is then subjected to plate and frame filtration to obtain a brownish-yellow powder, namely the neutralization residue; the proportion of particles with a particle size less than 0.045 μm in the neutralization residue is 96%;

[0084] In the neutralization residue, the mass content of calcium oxide is 28%, the mass content of calcium sulfate is 35%, and the mass content of iron hydroxide is 17%;

[0085] The neutralization residue is dried, then pulverized, and passed through a 20-mesh sieve to obtain the pretreated neutralization residue;

[0086] 2) Weigh 100 g of the pretreated neutralization residue into a beaker, add 600 mL of deionized water and stir evenly to obtain a suspension; adjust the pH of the suspension to 11 with a 30% NaOH aqueous solution by mass concentration; then pour it into a reaction kettle and place it in an oven to react at 120 °C for 1 h. After the reaction is completed, it is naturally cooled to room temperature; add 30 g of diatomaceous earth, stir at room temperature for 1 h, then filter by suction, and dry it in an oven (60 °C) to obtain the modified neutralization residue a;

[0087] 3) Weigh 100 g of the pretreated neutralization residue and mix it with limestone powder in a mass ratio of 6:4, calcine it in a muffle furnace at 800 °C for 2 h, naturally cool it to room temperature, and then grind it (the particle size after grinding < 2 mm) to obtain the modified neutralization residue b;

[0088] 4) Mix the modified neutralization residue a and the modified neutralization residue b in a mass ratio of 6:4, and then grind for 0.5 h (the particle size after grinding < 2 mm) to obtain a stabilizing agent for contaminated soil remediation.

[0089] 2. Usage effect of the stabilizing agent:

[0090] 1) Soil pollution situation

[0091] The test soil is from a heavy metal contaminated soil at a certain site in Fujian. The soil is severely contaminated by heavy metals. The sampling layer is the surface layer of 0 - 20 cm, the soil pH = 4.69 ± 0.25; the total lead content is 2060 mg / kg, the total cadmium content is 121.7 mg / kg, the lead leaching concentration is 78.5 μg / L, the cadmium leaching concentration is 46.7 μg / L, and the water content is 16%. Before use, the soil is naturally air-dried, and plant residues, gravel, etc. are selected and ground, and then passed through a 10-mesh sieve for standby;

[0092] 2) Test steps

[0093] Weigh 100 g of the above-mentioned lead-cadmium contaminated soil and add it to a 500 mL beaker. Sprinkle 3 g of the above-prepared stabilizing agent, mix the two evenly, add an appropriate amount of deionized water, and keep the saturated water content of the soil at 25% during the experiment. Then stir evenly, seal it with plastic wrap and make ventilation holes. Add water every 2 days to maintain the water content of the system. When the curing time reaches 30 days, take out the sample for air drying and send it for inspection.

[0094] 3) Test results

[0095] The results show that the leaching concentrations of Pb and Cd in the above contaminated soil by the stabilizing agent are 13.4 μg / L and 2.7 μg / L respectively, and their reduction rates are 82.9% and 94.2% respectively. The final result shows that it meets the Class III standard of the Surface Water Environment Quality Standard GB3838-2002.

[0096] Example 3

[0097] 1. Preparation of the stabilizing agent:

[0098] 1) Preparation and pretreatment of the neutralization residue:

[0099] The acidic wastewater generated from the copper sulfide mine is neutralized with lime to obtain a neutralization slurry, and then after plate and frame filtration, a brownish-yellow powder is obtained, which is the neutralization residue. The mass ratio of particles with a particle size less than 0.045 μm in the neutralization residue is 96%.

[0100] In the neutralization residue, the mass content of calcium oxide is 28%, the mass content of calcium sulfate is 35%, and the mass content of iron hydroxide is 17%.

[0101] Dry the neutralization residue, then crush it, and pass through a 20-mesh sieve to obtain the pretreated neutralization residue.

[0102] 2) Weigh 100 g of the pretreated neutralization residue in a beaker, add 800 mL of deionized water and stir evenly to obtain a suspension. Adjust the pH of the suspension to 11 with a 30% NaOH aqueous solution by mass concentration. Then pour it into a reaction kettle and place it in an oven to react at 120 °C for 1 h. After the reaction, naturally cool to room temperature. Add 25 g of diatomaceous earth, stir at room temperature for 1 h, then filter by suction, and dry it in an oven (60 °C) to obtain the modified neutralization residue a.

[0103] 3) Weigh 100 g of the pretreated neutralization residue and mix it with limestone powder in a mass ratio of 7:3, calcine it in a muffle furnace at 800 °C for 2 h, naturally cool to room temperature, and then grind it (the particle size after grinding < 2 mm) to obtain the modified neutralization residue b.

[0104] 4) Mix the modified neutralized slag a and the modified neutralized slag b according to a mass ratio of 5:4, and then grind for 0.5 h (the particle size after grinding < 2 mm) to obtain a stabilizer for contaminated soil remediation.

[0105] 2. Usage effect of the stabilizer:

[0106] 1) Soil pollution situation

[0107] The tested soil is from a heavy metal contaminated soil site in Fujian. The soil is severely contaminated by heavy metals. The sampling layer is the surface layer of 0 - 20 cm. The soil pH = 4.69 ± 0.25; the total lead content is 2060 mg / kg, the total cadmium content is 121.7 mg / kg, the lead leaching concentration is 78.5 μg / L, the cadmium leaching concentration is 46.7 μg / L, and the water content is 16%. Before use, the soil is naturally air-dried, and plant residues, gravel, etc. are selected, ground, and passed through a 10-mesh sieve for standby;

[0108] 2) Test steps

[0109] Weigh 100 g of the above lead and cadmium contaminated soil and add it to a 500 mL beaker. Sprinkle 3 g of the above-prepared stabilizer, mix and stir the two evenly, then add an appropriate amount of deionized water. During the test, keep the saturated water content of the soil at 25%; then stir evenly, seal with plastic wrap and make ventilation holes; Add water every 2 d to maintain the water content of the system; When the ripening time reaches 30 d, take out the sample for air-drying treatment and send it for inspection.

[0110] 3) Test results

[0111] The results show that the leaching concentrations of Pb and Cd in the above contaminated soil by the stabilizer are 12.4 μg / L and 2.1 μg / L respectively, and their reduction rates are 84.2% and 95.5% respectively. The final result shows that it meets the Class III standard of the Surface Water Environmental Quality Standard GB3838 - 2002.

[0112] Control Example 1

[0113] 1. Preparation of the stabilizer:

[0114] 1) Preparation and pretreatment of the neutralized slag:

[0115] The acidic wastewater generated from the copper sulfide mine is treated by lime neutralization to obtain a neutralized slurry, and then after plate and frame filtration, a yellowish-brown powder is obtained, which is the neutralized slag; the mass ratio of the particles with a particle size less than 0.045 μm in the neutralized slag is 96%;

[0116] In the neutralized slag, the mass content of calcium oxide is 28%, the mass content of calcium sulfate is 35%, and the mass content of iron hydroxide is 17%;

[0117] Dry the neutralization slag, then crush it, and sieve it through a 20-mesh sieve to obtain the pretreated neutralization slag.

[0118] 2. Usage effect of the stabilizing agent:

[0119] 1) Soil pollution situation

[0120] The tested soil is from a heavy metal-polluted soil site in Fujian. The soil is severely polluted by heavy metals. The sampling layer is the surface layer of 0 - 20 cm, the soil pH = 4.69 ± 0.25; the total lead content is 2060 mg / kg, the total cadmium content is 121.7 mg / kg, the lead leaching concentration is 78.5 μg / L, the cadmium leaching concentration is 46.7 μg / L, and the water content is 16%. Before use, the soil is naturally air-dried, and plant residues, gravel, etc. are selected, ground, and sieved through a 10-mesh sieve for standby;

[0121] 2) Test steps

[0122] Weigh 100 g of the above-mentioned lead-cadmium polluted soil and add it to a 500 mL beaker. Sprinkle 3 g of the pretreated neutralization slag mentioned above, mix and stir the two evenly, then add an appropriate amount of deionized water. During the test process, keep the saturated water content of the soil at 25%; then stir evenly further, seal it with plastic wrap and make air holes; Add water every 2 days to maintain the water content of the system; When the ripening time reaches 30 days, take out the sample for air-drying treatment and send it for inspection.

[0123] 3) Test results

[0124] The results show that: the leaching concentrations of Pb and Cd in the above-mentioned polluted soil by the stabilizing agent are 52.4 μg / L and 29.1 μg / L respectively, and their reduction rates are 33.2% and 37.7% respectively. The final result shows that it does not meet the Class III standard of the Surface Water Environmental Quality Standard GB 3838 - 2002.

[0125] Comparative Example 2

[0126] The difference from Example 1 is:

[0127] 1. In the preparation of the stabilizing agent, in step 3), weigh 100 g of the pretreated neutralization slag and mix it with limestone powder according to a mass ratio of 7:3, grind it (the particle size after grinding < 2 mm) to obtain modified neutralization slag b.

[0128] 2. Usage effect of the stabilizing agent:

[0129] 1) Soil pollution situation

[0130] The test soil was taken from a heavily heavy metal - polluted soil site in Fujian. The sampling layer was the surface layer of 0 - 20 cm, with soil pH = 4.69 ± 0.25; the total lead content was 2060 mg / kg, the total cadmium content was 121.7 mg / kg, the lead leaching concentration was 78.5 μg / L, the cadmium leaching concentration was 46.7 μg / L, and the water content was 16%. Before use, the soil was naturally air - dried, and plant residues, gravel, etc. were picked out, ground and passed through a 10 - mesh sieve for standby;

[0131] 2) Test procedures

[0132] Weigh 100 g of the above - mentioned lead - cadmium - polluted soil and add it to a 500 - mL beaker. Sprinkle 3 g of the prepared stabilizing agent, mix the two evenly, then add an appropriate amount of deionized water. During the test, keep the saturated water content of the soil at 25%; then stir evenly further, seal it with plastic wrap and make ventilation holes; add water every 2 d to maintain the water content of the system; when the curing time reaches 30 d, take out the sample for air - drying treatment and send it for inspection.

[0133] 3) Test results

[0134] The results show that the leaching concentrations of Pb and Cd in the above - mentioned polluted soil by the stabilizing agent are 21 μg / L and 9.9 μg / L respectively, and their reduction rates are 73.2% and 78.8% respectively. The final result shows that it does not meet the Class Ⅲ standard of the Surface Water Environmental Quality Standard GB3838 - 2002.

[0135] Comparative example 3

[0136] The difference from Example 1 is as follows:

[0137] 1. In the preparation of the stabilizing agent, in step 2), weigh 100 g of the pretreated neutralization residue in a beaker, add 400 mL of deionized water and stir evenly to obtain a suspension; adjust the pH of the suspension to 11 with a 30% NaOH aqueous solution by mass; add 20 g of diatomite, stir at room temperature for 1 h, then filter by suction and dry in an oven (60℃) to obtain modified neutralization residue a.

[0138] 2. The use effect of the stabilizing agent:

[0139] 1) Soil pollution situation

[0140] The test soil was taken from a heavily heavy metal - polluted soil site in Fujian. The sampling layer was the surface layer of 0 - 20 cm. The soil pH was 4.69 ± 0.25; the total lead content was 2060 mg / kg, the total cadmium content was 121.7 mg / kg, the lead leaching concentration was 78.5 μg / L, the cadmium leaching concentration was 46.7 μg / L, and the water content was 16%. Before use, the soil was naturally air - dried, and plant residues, gravel, etc. were picked out. After grinding, it was passed through a 10 - mesh sieve for standby;

[0141] 2) Test procedures

[0142] Weigh 100 g of the above - mentioned lead - cadmium - polluted soil and add it to a 500 - mL beaker. Sprinkle 3 g of the above - prepared stabilization agent, mix the two evenly, then add an appropriate amount of deionized water. During the test, keep the saturated water content of the soil at 25%; then stir evenly further, seal it with plastic wrap and punch air holes; add water every 2 days to maintain the water content of the system; when the curing time reaches 30 days, take out the sample for air - drying treatment and send it for inspection.

[0143] 3) Test results

[0144] The results show that: the leaching concentrations of Pb and Cd in the above - mentioned polluted soil with the stabilization agent are 25.4 μg / L and 13 μg / L respectively, and their reduction rates are 67.6% and 72.1% respectively. The final result shows that it does not meet the Class Ⅲ standard of the Surface Water Environmental Quality Standard GB3838 - 2002.

[0145] The experimental results show that when treating polluted soil (in the polluted soil, pH = 4.69 ± 0.25, total lead content 2060 mg / kg, total cadmium content 121.7 mg / kg, lead leaching concentration 78.5 μg / L, cadmium leaching concentration 46.7 μg / L, water content 16%) with the stabilization agent for polluted soil remediation provided by the present invention, the reduction rate of the leaching concentrations of lead and cadmium in the polluted soil is greater than 80%.

[0146] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stabilization agent for contaminated soil remediation, comprising: Modified neutralization slag a and modified neutralization slag b; The preparation method of the modified neutralization slag a includes the following steps: Mix the first part of the neutralization slag with water to obtain a suspension, react the suspension at 80-140°C and a pH value of 10-12, stir and mix the reaction product liquid with diatomite, and after solid-liquid separation, obtain the modified neutralization slag a; The preparation method of the modified neutralization slag b includes the following steps: Mix the second part of the neutralization slag with limestone powder and / or dolomite powder, and then calcine to obtain the modified neutralization slag b; In the neutralization slag, the mass content of calcium oxide is 27%-30%, the mass content of calcium sulfate is 34%-38%, and the mass content of iron hydroxide is 16%-20%; The mass ratio of the modified neutralization slag a to the modified neutralization slag b is 3-6:4-7.

2. The stabilizing agent for contaminated soil remediation according to claim 1, wherein In the preparation method of the modified neutralization slag a, the dosage ratio of the first part of the neutralization slag to water is 100 g:200-800 mL.

3. The stabilization agent for contaminated soil remediation according to claim 1, characterized in that, In the preparation method of the modified neutralization slag a, after obtaining the suspension, use a sodium hydroxide solution to adjust the pH value of the suspension to 10-12; The mass concentration of the sodium hydroxide solution is 25%-35%.

4. The stabilizing agent for contaminated soil remediation according to claim 1, characterized in that, In the preparation method of the modified neutralization slag a, the reaction time is 0.5-2 h; After the reaction, it further includes: naturally cooling to room temperature.

5. The stabilization agent for contaminated soil remediation according to claim 1, wherein In the preparation method of the modified neutralization slag a, the mass ratio of the diatomite to the first part of the neutralization slag is 1-4:

10.

6. The stabilizing agent for contaminated soil remediation according to claim 1, characterized in that, In the preparation method of the modified neutralization slag a, the reaction product liquid and the diatomite are stirred and mixed at room temperature for 0.5-1.5 h; After the solid-liquid separation, it further includes: drying the obtained solid substance; the drying temperature is 55-65°C.

7. The stabilizing agent for contaminated soil remediation according to claim 1, characterized in that, The mass ratio of the second part of the neutralization slag to the limestone powder and / or dolomite powder is 6-9:1-4.

8. The stabilizing agent for contaminated soil remediation according to claim 1, characterized in that, In the preparation method of the modified neutralization slag b, the calcination temperature is 600-1200°C and the time is 1.5-2.5 h; After the calcination, it further includes: naturally cooling to room temperature and then grinding.

9. The preparation method of the stabilizing agent for contaminated soil remediation according to any one of claims 1-8, includes the following steps: Mix the modified neutralization slag a and the modified neutralization slag b to obtain a stabilizing agent for contaminated soil remediation.