A method for solidifying heavy metal contaminated soil at the estuary where it flows into the sea

Abstract

The present invention discloses a method for synergistically solidifying heavy metal contaminated soil at the estuary of the sea using urease and its modifiers in combination with microwave technology, including: 1. Mix soy flour and deionized water, stir and centrifuge to remove soybean dregs, and take the supernatant as the urease solution; 2. Mix the urea solution and the calcium salt solution to obtain the cementitious liquid; 3. Crush waste concrete waste to obtain fine building aggregates, and add milky quartz powder to make a urease-induced carbonate modifier; 4. Dig the surface heavy metal contaminated soil and mix it with the modifier in step 3, and air-dry it; 5. Add water to the air-dried contaminated soil to the optimal moisture content and backfill it; 6. Lay a white cleaning cloth on the surface of the backfilled contaminated soil, pour the urease solution and the cementitious liquid in sequence, and use the self-weight seepage to make the urease solution and the cementitious liquid penetrate into the interior of the contaminated soil; 7. Turn on the microwave generator to irradiate the soil. The present invention can solidify heavy metal contaminated soil in a high salinity environment, reduce the leaching concentration of heavy metals in the contaminated soil, and improve the strength of the contaminated soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and particularly relates to a method for remediating heavy metal contaminated soil at the estuary of the sea, and more particularly to a method for solidifying heavy metal contaminated soil at the estuary of the sea. Background Art

[0002] Since the Pearl River Delta region is mainly an industrial cluster for light industries, there are many hardware, chemical, and electroplating enterprises, and the treatment and processing of heavy metals are relatively intensive. Due to the lack of sufficient attention to environmental pollution problems in the early stage, a large amount of industrial waste gas, industrial wastewater, and industrial solid waste were directly discharged without effective treatment, resulting in heavy metal pollutants directly or indirectly entering the soil, bringing difficult-to-treat metal pollution to the soil in the Pearl River Delta region. Among them, several inorganic pollutants such as Cu, Zn, Cd, and Pb are the main polluting metals. In addition to the pollution problem in the Pearl River Delta region, there is also the phenomenon of "saltwater intrusion" in the groundwater of its soil. "Saltwater intrusion" refers to the phenomenon that seawater with a high salt concentration at the end of the river flows backward along the river channel with the ebb and flow of the tide, causing the salt concentration in the upstream river water to rise, which is commonly found in the river estuary area. Due to the large amount of rainfall in the Pearl River Delta region, the river network in the estuary area is dense, and there is a complex exchange relationship between groundwater and atmospheric precipitation, river surface water, and seawater. Seawater flows into the rivers in the Pearl River Delta region through various ways, and a certain proportion of seawater seeps into the groundwater, increasing the salt concentration of the groundwater and the chloride concentration higher than 5000 mg / L, thereby causing soil salinization. This means that while considering how to treat the contaminated soil in the Pearl River Delta region, we also need to consider the background of the high salinity environment of the soil brought about by the "saltwater intrusion" phenomenon.

[0003] At present, the main heavy metal contaminated soil remediation technologies are biological control technology and chemical control technology. In the past more than 10 years, the theoretical and technical research on phytoremediation has received relatively much attention at home and abroad. However, phytoremediation usually requires a relatively long time period, and there is a risk that heavy metals originally in the soil may be transferred to the food chain through plant absorption, causing the diffusion of pollutants. Moreover, it is difficult for plants to survive in a high-salt environment. The solidification / stabilization technology is a commonly used means for the remediation of contaminated sites of metals and some organic substances. The main process of its solidification / stabilization is to mix pollutants with solidifying agents, and reduce the leachability of pollutants through physical or chemical methods, and transform toxic and harmful waste into stable landfill materials to meet the basic requirements of people's living use. At present, cement is usually used as a solidifying agent to stabilize contaminated soil. However, in the high-salinity soil environment generated by seawater intrusion on the slope of the Pearl River Estuary, it is not conducive to the hardening reaction of cement and the treatment cost is relatively high. Using microbial technology to solidify / stabilize heavy metals in contaminated soil is a new soil remediation technology that combines in-situ microbial remediation and chemical fixation. As a new type of physical treatment means, microwave radiation has received extensive attention in recent years because of its advantages such as cleanliness, high efficiency, pollution-free, energy-saving, time-saving, and simple operation. The thermal effect and non-thermal effect generated by appropriate low-frequency microwave radiation can change the conformation and catalytic ability of enzyme proteins, improve the enzyme activity, and realize the efficient optimization induction of biological enzymes. Using microbial technology alone has certain limitations and the achieved effect is not good. Therefore, the present invention proposes a method for efficiently inducing urease to repair heavy metal contaminated soil at the estuary of the sea in a high-salinity environment through microwave radiation technology combined with modifiers. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for synergistically solidifying heavy metal contaminated soil at the estuary of the sea by using urease and its modifiers in combination with microwave technology. This remediation method repairs the heavy metal contaminated soil at the estuary of the sea by inducing carbonate precipitation with urease, adding modifiers and combining with microwave technology, improves the physical and chemical properties of the soil, and effectively solves the problem of solidification / stabilization of contaminated soil.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A method for synergistically solidifying heavy metal contaminated soil at the estuary of the sea by using urease and its modifiers in combination with microwave technology, comprising the following steps:

[0007] Step 1: Bake soybeans, then crush them with a grinder, sieve them to obtain soybean powder, mix the soybean powder and deionized water, stir and centrifuge the mixed solution to remove soybean dregs, and take the supernatant of the remaining liquid as urease solution for standby;

[0008] Step 2: Mix the urea solution and the calcium salt solution evenly to obtain a cementing liquid for standby;

[0009] Step 3: Take waste concrete scraps, crush them, perform secondary crushing on the crushed concrete blocks, screen out the part in the range of 0.16 mm to 2.36 mm as fine building aggregates, add a certain mass of milky quartz powder to make a urease-induced carbonate modifier, and set it aside for later use;

[0010] Step 4: Clean the surface sundries of the heavy metal contaminated soil site, then dig the surface heavy metal contaminated soil with a depth of 0.5 m to 2.0 m from top to bottom and place it in the mixing yard near the site, and uniformly mix it with the modifier prepared in Step 3, and air-dry it naturally;

[0011] Step 5: Add water to the air-dried contaminated soil to the optimal moisture content, backfill it in layers of 200 mm to 250 mm to the original contaminated soil site, tamp it after each layer is paved, after backfilling to the design elevation, level it by pulling a line, the deviation of the backfill flatness is 50 mm, and take measures such as shoveling and filling and tamping to deal with the deviation exceeding the standard;

[0012] Step 6: Lay a layer of non-woven fabric on the surface of the backfilled contaminated soil, and then pour the urease solution prepared in Step 1 and the cementing solution prepared in Step 2 on the surface of the contaminated soil in sequence, and use the self-weight seepage to make the urease solution and the cementing solution penetrate into the interior of the contaminated soil;

[0013] Step 7: Turn on the microwave generator to irradiate the soil, where the microwave frequency is 300 MHz to 20 GHz and the power is 0.8 kW to 10 kW;

[0014] Step 8: After the contaminated soil is mineralized, repeat Step 7 for 3 to 5 times to complete the treatment.

[0015] More specifically, a method for synergistically solidifying heavy metal contaminated soil at the estuary of the sea using urease and its modifier in combination with microwave technology includes the following steps:

[0016] Step 1, take soybeans, bake them at 40 °C for 6 hours, then crush them with a grinder, screen them through a 0.15 mm sieve to obtain soybean powder. Mix the soybean powder and deionized water at a concentration of 100 g / L in a beaker. Stir the mixed solution magnetically for 30 min, and then centrifuge it at 3000 r / min for 30 min to remove the soybean dregs. Take the supernatant of the remaining liquid as the urease solution and set it aside for later use;

[0017] Step 2, mix the urea solution and the calcium salt solution evenly to obtain a cementing solution and set it aside for later use;

[0018] Step 3: Take waste concrete, break it by manual hammering, and then use a jaw crusher to perform secondary crushing on the crushed concrete blocks. Use the method of manual screening to select the part in the range of 0.16 mm to 2.36 mm from the crushed recycled aggregate as building fine aggregate for standby; add a certain mass of milky quartz powder to make a urease-induced carbonate modifier, and the mass ratio of the building fine aggregate to the milky quartz powder is 1:1 to 5:1 for standby;

[0019] Step 4: First, clean the surface sundries of the heavy metal contaminated soil site, and then dig the surface heavy metal contaminated soil with a depth of 0.5 m to 2.0 m from top to bottom and place it in the mixing yard near the site, and evenly mix it with the modifier prepared in Step 3 and air-dry it naturally;

[0020] Step 5: Add water to the air-dried contaminated soil to the optimal moisture content, and backfill it in layers of 200 mm to 250 mm to the original contaminated soil site. After each layer is paved, compact it. After backfilling to the design elevation, level it by pulling a line. The deviation of the backfill flatness is 50 mm. For those exceeding the deviation, take measures such as leveling and filling and compacting the soil;

[0021] Step 6: Lay a layer of non-woven fabric on the surface of the backfilled contaminated soil, and then pour the urease solution prepared in Step 1 and the cementing solution prepared in Step 2 on the surface of the contaminated soil in sequence. Use the self-weight seepage to make the urease solution and the cementing solution penetrate into the interior of the contaminated soil;

[0022] Step 7: Turn on the microwave generator to irradiate the soil, where the microwave frequency is 300 MHz to 20 GHz, the power is 0.8 kW to 10 kW, rest for 25 minutes every 5 minutes of irradiation, and the average irradiation per hour is 10 minutes, and the total irradiation treatment is 6 hours;

[0023] Step 8: Wait for the contaminated soil to mineralize for 24 hours, and repeat the process described in Step 7 for 3 to 5 times to complete the treatment.

[0024] Preferably, in Step 2, the concentration of the urea solution is 1.0 mol / L, the calcium salt solution is CaCl2 with a concentration of 1.0 mol / L, and the volume mixing ratio [CaCl2:urea] = 2:3;

[0025] Preferably, in Step 3, the particle size of the milky quartz powder is ≤1 mm, and the mass ratio of the modifier to the contaminated soil during mixing is 1:10;

[0026] Preferably, in Step 5, the optimal moisture content refers to the moisture content corresponding to the peak point on the dry density and moisture content relationship curve obtained in the compaction test of the soil. Generally, the optimal moisture content is 15% to 20%; the compaction times for each layer of backfilled soil are 3 times, and the commonly used frog rammer manual compaction method is adopted. The positions of the compaction points should be connected to each other, vertically and horizontally crossed to ensure no missed compaction points;

[0027] Preferably, taking one reinforcement cycle in step 6 as an example, first pour urease solution with a volume of 1 times the pore volume of the contaminated soil on the surface of the contaminated soil, and let it stand for 1 h; then pour cementing liquid with a volume of 1 times the pore volume on the surface of the contaminated soil, cover it with a plastic film on the surface, and react for 24 h;

[0028] Preferably, in step 8, the microwave irradiation frequency is 2.45 GHz and the power is 2 kW;

[0029] The method for synergistically solidifying heavy metal contaminated soil at the estuary of the sea using urease and its modifiers in combination with microwave technology is used for the remediation of heavy metal contaminated soil at the estuary of the sea.

[0030] Compared with the prior art, the beneficial effects of the present invention include:

[0031] 1. It is difficult for the prior art to effectively treat contaminated soil in a high-salinity environment. Therefore, the present invention proposes a method for synergistically remediating heavy metal contaminated soil at the estuary of the sea by urease-induced carbonate precipitation technology, adding modifiers and combining with microwave technology, which can better solidify heavy metal contaminated soil in a high-salinity environment, reduce the leaching concentration of heavy metals in the contaminated soil, improve the strength of the contaminated soil, realize the solidification and stabilization of the contaminated soil, and facilitate the secondary development and utilization of the contaminated site.

[0032] 2. Microorganisms are not easy to survive in a high-salinity environment. Compared with the conventional microorganism-induced technology, the urease-induced technology has lower environmental requirements, simpler operation, faster reaction rate, lower cost, smaller environmental safety risk, and more obvious effect on mineralizing heavy metal contaminated soil. Moreover, urease has a wide range of sources and can be obtained from plants such as soybeans more easily.

[0033] 3. By using a urease solution with a concentration of 100 g / L and controlling the cementing liquid to be composed of a urea solution with a concentration of 1.0 mol / L - 1.5 mol / L and a calcium salt solution with a concentration of 1.0 mol / L - 1.5 mol / L, and the mixing ratio [CaCl2:urea] = 2:3, the yield of calcium carbonate precipitation can be effectively improved, the morphology and structure of calcium carbonate precipitation can be improved, and the precipitate can form a uniform microcrystalline structure, thereby improving its strength and stability and enhancing the solidification effect.

[0034] 4. The thermal effect of microwave radiation can effectively act on opalescent quartz powder. The addition of opalescent quartz powder can significantly increase the thermal conductivity of the material and enhance the heating effect of microwave radiation. Controlling the microwave frequency between 300MHz and 20GHz and the power between 0.8kW and 10kW can effectively increase the ambient temperature around urease, enhance urease activity, accelerate urea hydrolysis, improve the efficiency of urease-induced carbonate precipitation, increase the amount of heavy metal carbonate produced, and reduce the leaching concentration of heavy metal ions in contaminated soil. Furthermore, the non-thermal effect of microwave radiation can change the conformation of the enzyme protein, which can also increase enzyme activity to a certain extent and improve the efficiency of urease-induced carbonate precipitation.

[0035] 5. The raw materials for preparing fine building aggregate are all derived from construction waste and industrial waste. This invention achieves waste utilization, is highly economical, and achieves low-carbon and sustainable development. Recycled fine building aggregate with a particle size of 0.16mm to 2.36mm is obtained by crushing and screening discarded concrete. Due to the mortar attached to the surface, its bluntness, aspect ratio, and sphericity are relatively low, while its porosity is large, resulting in a low loose bulk density and high water absorption rate. When mixed with milky white quartz powder and added to heavy metal-contaminated soil, it can optimize the particle size distribution of the heavy metal-contaminated soil, provide attachment sites for urease, improve the uniformity of its remediation, and improve the physical and chemical properties of the soil, thus facilitating ecological restoration. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the purpose of the embodiments is to further illustrate the content of the present invention and should not be interpreted as limiting the scope of protection of the present invention in any sense.

[0037] Example 1

[0038] A method for solidifying heavy metal-contaminated soil at river mouths, using urease and its modifier in combination with microwave technology for synergistic solidification:

[0039] Waste concrete was collected from a demolition site in Wuhan. After being manually hammered, the crushed concrete blocks were re-crushed using a jaw crusher. The recycled aggregate was manually screened to identify the fine aggregate in the 0.16mm to 2.36mm range.

[0040] Soil was retrieved from the contaminated site, air-dried naturally, and reserved. An amendment was prepared, which consisted of 12.5 g of fine building aggregate and 2.5 g of milky quartz powder. 15 g of the amendment was mixed with 150 g of heavy metal-contaminated soil at a mass ratio of 1:10, passed through a 1-mm sieve, and air-dried naturally for reserve. A soybean urease cementing solution was prepared, which mainly consisted of two parts: a crude soybean urease extract and a cementing solution. The preparation method of the crude soybean urease extract was as follows: Soybeans were baked at 40 °C for 6 hours, then crushed with a grinder and screened through a 0.15-mm sieve to obtain soybean powder. The soybean powder and deionized water were mixed in a beaker at a concentration of 100 g / L. The mixed solution was stirred for 30 min and then centrifuged at 3000 r / min for 30 min to remove soybean dregs. The supernatant of the remaining liquid was taken as the urease solution; the cementing solution was a urea-calcium chloride solution ([CaCl2:urea] = 2:3, [CaCl2] = 1.0 M), which was mixed evenly to obtain the cementing solution. 150 g of the soil sample after mixing and drying the amendment with the contaminated soil was weighed and placed into a cylindrical flexible mold with a diameter of 40 mm and a height of 80 mm to form a cylindrical specimen. A water-permeable stone with a thickness of 10 mm was placed at the lower end of the mold. 20 mL of the urease solution and the cementing solution were sequentially injected from the top of the soil sample at a rate of 4 mL / min with a peristaltic pump, and then microwave irradiation treatment was carried out for 6 h, where the microwave frequency was 2.45 GHz and the power was 2 kW. After mineralization for 24 h, the injection and irradiation were repeated 4 times. After the mineralization reaction time of 10 days, the cylindrical specimen was taken out, the cylindrical flexible mold was removed, and it was air-dried naturally. The above steps were repeated to make three parallel specimens in total. The air-dried specimens were subjected to an unconfined compressive strength test and a toxicity leaching test. The test results were the average values of the three groups.

[0041] After testing, the leaching concentration of Cu decreased from 378.56 mg / L before solidification to 76.32 mg / L after solidification; the leaching concentration of Zn decreased from 412.91 mg / L before solidification to 86.59 mg / L after solidification; the leaching concentration of Cd decreased from 8.72 mg / L before solidification to 0.81 mg / L after solidification; the leaching concentration of Pb decreased from 19.26 mg / L before solidification to 4.23 mg / L after solidification; the unconfined compressive strength of the specimen after solidification was 1.268 MPa, which was much higher than the unconfined compressive strength of 0.267 MPa of the specimen before solidification. According to the identification of the leaching toxicity of hazardous wastes in the Standard for Identification of Hazardous Wastes - Leaching Toxicity Identification (GB5085.3 - 2007) of the People's Republic of China, the experimental result data was lower than the standard value of the leaching toxicity identification of hazardous wastes. At the same time, the unconfined compressive strength of the heavy metal-contaminated soil after remediation reached 0.35 MPa, which met the requirements of the US Environmental Protection Agency.

[0042] Example 2

[0043] Same as Example 1, except that the urease solution is replaced with the same volume of deionized water, and the unconfined compressive strength test and toxicity leaching test are carried out on the specimen.

[0044] After testing, the leaching concentration of Cu decreased from 378.56 mg / L before solidification to 315.64 mg / L after solidification; the leaching concentration of Zn decreased from 412.91 mg / L before solidification to 372.34 mg / L after solidification; the leaching concentration of Cd decreased from 8.72 mg / L before solidification to 7.65 mg / L after solidification; the leaching concentration of Pb decreased from 19.26 mg / L before solidification to 15.52 mg / L after solidification; the unconfined compressive strength of the specimen after solidification was 0.364 MPa, slightly higher than the unconfined compressive strength of 0.267 MPa of the specimen before solidification.

[0045] Example 3

[0046] Same as Example 1, the difference is that 150 g of the soil sample after mixing and drying the modifier and the contaminated soil is weighed and placed into a cylindrical flexible mold with a diameter of 40 mm and a height of 80 mm to form a cylindrical specimen. A permeable stone with a thickness of 10 mm is placed at the lower end of the mold, and 20 mL of urease solution and cementing liquid are sequentially injected from the top of the soil sample at a rate of 4 mL / min with a peristaltic pump, and then no microwave irradiation is carried out. After reaching the mineralization reaction time of 10 days, the cylindrical specimen is taken out, the cylindrical flexible mold is removed, and it is naturally air-dried. The above steps are repeated to make three parallel specimens in total. The air-dried specimens are taken for unconfined compressive strength test and toxicity leaching test. The test results are the average values of the three groups.

[0047] After testing, the leaching concentration of Cu decreased from 378.56 mg / L before solidification to 302.78 mg / L after solidification; the leaching concentration of Zn decreased from 412.91 mg / L before solidification to 354.98 mg / L after solidification; the leaching concentration of Cd decreased from 8.72 mg / L before solidification to 5.63 mg / L after solidification; the leaching concentration of Pb decreased from 19.26 mg / L before solidification to 12.65 mg / L after solidification; the unconfined compressive strength of the specimen after solidification was 0.457 MPa, slightly higher than the unconfined compressive strength of 0.267 MPa of the specimen before solidification.

[0048] In order to prove the technical effect of the present invention, a single comparative test is designed. It can be seen that the effects of single urease and microwave are not good, and the heavy metal leaching concentration has not changed significantly before and after treatment. However, the effect is obvious after the combined treatment of the two, and the experimental result data after treatment is lower than the hazardous waste leaching toxicity identification standard value of the "Identification Standard for Hazardous Wastes - Leaching Toxicity Identification" (GB5085.3 - 2007) of the People's Republic of China, and it has a very obvious technical effect in the remediation of heavy metal contaminated sites at the estuary of the sea.

Claims

1. A method for solidifying heavy metal contaminated soil at the estuary where it flows into the sea, characterized in that, It includes the following steps: Step 1: Take soybeans for baking, then crush them with a grinder, sieve them to obtain soybean powder. Mix the soybean powder and deionized water, stir and centrifuge the mixed solution to remove soybean dregs. Take the supernatant of the remaining liquid as the urease solution for standby. Step 2: Take the urea solution and the calcium salt solution and mix them evenly to obtain the cementing liquid for standby. Step 3: Take waste concrete scraps, crush them, and perform secondary crushing on the crushed concrete blocks. Screen out the part in the range of 0.16 mm to 2.36 mm as building fine aggregate, and add opal quartz powder with a mass ratio of 1:1 to 1:5 to the building fine aggregate to make the urease-induced carbonate modifier for standby. Step 4: Clean the surface sundries of the heavy metal contaminated soil site, then dig the surface heavy metal contaminated soil with a depth of 0.5 m to 2.0 m from top to bottom and place it in the mixing yard near the site, and mix it evenly with the modifier prepared in Step 3, and air-dry it naturally. Step 5: Add water to the air-dried contaminated soil until the moisture content is 15% to 20%, backfill it in layers of 200 mm to 250 mm to the original contaminated soil site. After each layer is paved, compact it. After backfilling to the design elevation, level it with a string. The backfilling flatness deviation is 50 mm. For those exceeding the deviation, take measures such as shoveling and filling and compacting the soil to deal with it. Step 6: Lay a layer of scouring pad on the surface of the backfilled contaminated soil, and then pour the urease solution prepared in Step 1 and the cementing liquid prepared in Step 2 on the surface of the contaminated soil in sequence. Use self-weight seepage to make the urease solution and the cementing liquid penetrate into the interior of the contaminated soil. Step 7: Turn on the microwave generator to irradiate the soil, where the microwave frequency is 300 MHz to 20 GHz and the power is 0.8 kW to 10 kW. Step 8: After the contaminated soil is mineralized, repeat Step 7 for 3 to 5 times to complete the treatment.

2. The method for solidifying heavy metal contaminated soil at the estuary of the sea as claimed in claim 1, wherein Step 1: Take soybeans and bake them at 30°C to 50°C for 6 hours, then crush them with a grinder, sieve them to obtain soybean powder. Mix the soybean powder and deionized water, stir the mixed solution for 30 min, and then centrifuge it at 3000 r / min for 30 min to remove soybean dregs. Take the supernatant of the remaining liquid as the urease solution for standby. Step 2: Take the urea solution and the calcium salt solution and mix them evenly to obtain the cementing liquid. The cementing liquid is composed of a urea solution with a concentration of 1.0 mol / L to 1.5 mol / L and a calcium salt solution with a concentration of 1.0 mol / L to 1.5 mol / L, and the volume mixing ratio [CaCl2:urea] = 2:3 for standby. Step 3: Take waste concrete scraps, after manually hammering and crushing them, use a jaw crusher to perform secondary crushing on the crushed concrete blocks. Screen out the part in the range of 0.16 mm to 2.36 mm as building fine aggregate, and add a certain mass of opal quartz powder to make the urease-induced carbonate modifier for standby. Step 7: Turn on the microwave generator to irradiate the soil, where the microwave frequency is 300 MHz to 20 GHz, the power is 0.8 kW to 10 kW, rest for 25 minutes every 5 minutes of irradiation, the average irradiation is 10 minutes per hour, and the total irradiation treatment is 6 hours.

3. A method for solidifying heavy metal contaminated soil at the estuary of the sea, according to claim 1 or 2, characterized in that In the said step 4, the mass ratio of the modifier to the contaminated soil during mixing is 1:5 to 1:

10.

4. A method for solidifying heavy metal contaminated soil at the estuary where it flows into the sea according to claim 1 or 2, characterized in that, In the said step 6, the volume ratio of the urease solution to the cementing liquid during mixing is 1:1 to 2:

3.

5. A method for solidifying heavy metal contaminated soil at the estuary where it flows into the sea according to claim 1 or 2, characterized in that, In the said step 1, after being crushed by a grinder, it is sieved through a 0.15 mm sieve.

6. A method for solidifying heavy metal contaminated soil at the estuary of a river flowing into the sea according to claim 1 or 2, characterized in that, In the said step 4, the modifier and the contaminated soil are mixed in a mass ratio of 1:10 and passed through a 1 mm sieve.

7. A method for solidifying heavy metal contaminated soil at the estuary where it flows into the sea according to claim 1 or 2, characterized in that, In the said step 8, the mineralization time of the contaminated soil is 24 hours.

8. A method for solidifying heavy metal contaminated soil at the estuary flowing into the sea according to claim 1 or 2, characterized in that, In the said step 1, the soybean powder and deionized water are mixed at a concentration of 100 g / L.

9. A method for solidifying heavy metal contaminated soil at the estuary of the sea for the remediation of heavy metal contaminated soil at the estuary of the sea according to claim 1 or 2.