CN110479746B - Soil remediation and lead recovery process for lead-polluted site - Google Patents
Soil remediation and lead recovery process for lead-polluted site Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 185
- 238000005067 remediation Methods 0.000 title claims abstract description 23
- 238000011084 recovery Methods 0.000 title claims abstract description 18
- 239000012065 filter cake Substances 0.000 claims abstract description 73
- 239000000706 filtrate Substances 0.000 claims abstract description 62
- 239000007788 liquid Substances 0.000 claims abstract description 42
- 239000010865 sewage Substances 0.000 claims abstract description 29
- 238000004140 cleaning Methods 0.000 claims abstract description 28
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- 238000000354 decomposition reaction Methods 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000003763 carbonization Methods 0.000 claims abstract description 23
- 230000004913 activation Effects 0.000 claims abstract description 21
- 239000002253 acid Substances 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 20
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
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- 238000011065 in-situ storage Methods 0.000 abstract description 11
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- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 abstract 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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Abstract
The invention relates to a soil remediation and lead recovery process for a lead-polluted site, which comprises the steps of screening the grain size of the lead-polluted site soil, carbonizing, decomposing, activating in acid, cleaning, treating filtrate, and then recovering lead resources. After soil in a lead-polluted site is screened and crushed to be less than 13mm, the soil is firstly carbonized by ammonia water in a carbonization tank, filter cakes obtained after solid-liquid separation enter a decomposition tank to be decomposed by fluosilicic acid, slurry obtained after decomposition is subjected to solid-liquid separation and then sequentially enters an acidic activation tank for activation treatment and a cleaning tank for cleaning treatment, and filtrate is recycled after being treated by sewage treatment equipment, so that clean soil and lead-containing filter cakes are finally obtained. The invention has simple process flow and easy realization. After the soil in the lead-polluted site is treated by the process, the aims of in-situ backfilling of the soil in the lead-polluted site and recycling of lead resources in the soil are fulfilled, secondary pollution to the surrounding environment is avoided, and technical guarantee is provided for deep restoration and treatment of the soil in the lead-polluted site.
Description
Technical Field
The invention belongs to the field of polluted soil remediation and resource recycling, and particularly relates to a soil remediation and lead recycling process for a lead-polluted site.
Background
Lead-containing waste water, waste gas and waste residue can be generated in the processes of lead smelting, lead storage battery production, industrial electroplating, lead-containing gasoline use, lead-containing pigment use and the like, and lead-containing waste water, waste gas and waste residue can cause soil pollution when entering soil. Lead is one of the most common heavy metal pollutants in soil, can enter a human body through animals and plants, and can damage the digestive system after entering the human body, so that the immunologic function of the human body is reduced, a nervous system, a bone marrow hematopoietic system, the digestive system, a kidney and a reproductive system are damaged, and the growth of infants is slow, the children are short, the intelligence development is slow, and the like. Lead-contaminated soil poses a threat to ecological safety, and remediation and treatment of the type of contaminated soil are urgently needed.
Common technologies for repairing lead-polluted site soil include a soil leaching technology, a solidification and stabilization technology, a cement kiln cooperative treatment technology, a phytoremediation technology and the like, wherein the solidification and stabilization technology is used for wrapping lead in the soil inside by adding a stabilizer, cement and other curing agents to reduce the biotoxicity of the lead-polluted soil, but the risk of cracking of a wrapping layer exists along with the lapse of time, so that secondary pollution is caused to the environment; the cement kiln cooperative treatment is to send the lead polluted soil to a cement kiln, and the polluted soil is added in the cement production process, the method transfers the lead pollutants into cement, the polluted soil is not treated, and the cement use process still has the risk of secondary pollution; the phytoremediation is to utilize plants to absorb lead in soil and reduce the content of lead in the soil, but the method has long time and has no good treatment measures for the plants after absorbing heavy metals; soil leaching is a commonly used remediation technique in engineering by washing the soil with water or a leaching agent to separate lead contaminants from the soil. In the Li Shupeng 'a soil leaching remediation system and method' (2017102497807), the pollutants on the surfaces of coarse particles (comprising gravel, coarse sand, fine sand and the like) are eluted, transferred and concentrated into fine particle soil by leaching with clear water, slurry containing the fine particles is dehydrated, filter-pressed into mud cakes and then concentrated for subsequent treatment, and the leached clean coarse particles can be directly recycled after being detected to be qualified without being repaired.
In-situ backfilling and heavy metal resource recycling after the site contaminated soil is repaired and cleaned are development trends of soil remediation. At present, only the soil leaching technology can realize in-situ backfilling of partial coarse-particle soil, but the leaching technology can only remove acid-soluble lead pollutants and partial organic lead pollutants in the soil, the lead pollutants in the soil are transferred into fine-particle soil, the fine-particle soil still needs solidification and stabilization and ex-situ landfill treatment, and the lead pollutants cannot be completely separated from the soil. For a site with fine soil Pb content as high as 60% -75%, the soil leaching technology has the defects that the leaching of clean coarse-particle soil is limited, and the fine soil still needs to be solidified and stabilized, so that most of lead-polluted soil cannot be backfilled in situ, secondary pollution to the environment is caused, and lead resources in the soil are wasted.
Therefore, improvement of existing lead-contaminated site soil remediation is needed, so that the in-situ backfilling of coarse-particle soil in the prior art can be realized, the in-situ backfilling can be performed after the fine-particle soil is thoroughly separated from lead pollutants, and meanwhile, the lead in the pollutants can be recycled.
Disclosure of Invention
In view of the above, the present invention provides a soil remediation and lead recovery process for a lead-contaminated site, so as to achieve the purposes of in-situ backfilling of treated soil and lead resource recovery.
In order to achieve the purpose, the invention provides the following technical scheme:
a process for soil remediation and lead recovery in a lead contaminated site, the process comprising:
(1) screening and crushing the soil size fraction of the lead polluted site to obtain soil with the size fraction larger than 100mm and soil with the size fraction smaller than or equal to 13 mm;
(2) carbonizing the soil with the size fraction less than or equal to 13mm in the step (1), and settling and centrifuging to obtain a filter cake I;
(3) performing decomposition treatment on the filter cake I in the step (2), and performing sedimentation and centrifugation to obtain a filter cake II and a filtrate II:
(4) and (3) acidifying the filter cake II in the step (3), and performing sedimentation and centrifugation to obtain a filter cake III and a filtrate III:
(5) and (3) cleaning and separating the filter cake III in the step (4) to obtain a filter cake IV and a filtrate IV, wherein the filter cake IV is the clean soil:
(6) and (4) carrying out sewage treatment on the filtrate obtained in the steps (3) to (5), and carrying out solid-liquid separation after the treatment is finished to obtain a filter cake V and a filtrate V, wherein the filter cake V is the lead recovery material.
Preferably, the soil size fraction screening and crushing treatment of the lead-polluted site in the step (1) is specifically as follows:
(1) feeding the soil in the lead-polluted site into a circular vibrating screen for screening, feeding the soil I with the size fraction larger than 100mm on the screen into a coarse-grained soil temporary storage area, feeding the soil with the size fraction smaller than or equal to 100mm below the screen into a drum screen for wet screening to obtain soil II with the size fraction of 100-13 mm on the screen of the drum screen and soil III with the size fraction smaller than or equal to 13mm below the screen of the drum screen, and washing the soil with circulating water in the wet screening process;
(2) and (3) enabling the soil II to enter a hammer crusher, returning to the drum screen for wet screening after crushing, and repeating until the soil II becomes the soil IV with the screen size of less than or equal to 13mm below the drum screen.
Preferably, the carbonization treatment in the step (2) is specifically: the soil with the size fraction less than or equal to 13mm in the step (1) enters a carbonization tank, and 0.2mol/L NH is continuously added4And carbonizing the aqueous solution of OH for 1-2 hours, and settling and centrifuging after carbonization to respectively obtain a filter cake I and a filtrate I.
Preferably, the decomposition treatment in the step (3) is specifically: the filter cake I in the step (2) enters a decomposition pool, and 0.15mol/L H is continuously added2SiF6Decomposing the aqueous solution for 1-2 hours, and performing sedimentation and centrifugation after the decomposition is finished to respectively obtain a filter cake II and a filtrate II.
Preferably, the acidification treatment in the step (4) is specifically: the filter cake II in the step (3) enters an acid activation tank, and 0.1mol/L of HNO is continuously added3And (3) carrying out acidification treatment on the aqueous solution for 1-2 h, and carrying out sedimentation and centrifugation after acidification to respectively obtain a filter cake III and a filtrate III.
Preferably, the cleaning and separating treatment in the step (5) is specifically: and (4) cleaning the filter cake III in a cleaning pool for 0.5-1 h by using circulating water, separating in a membrane filter press after cleaning to obtain a filter cake IV and a filtrate IV, and feeding the filter cake IV into a clean soil temporary storage area.
Preferably, the volume-to-mass ratio of the liquid to the solid in the carbonization tank in the carbonization treatment process is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the decomposition tank in the decomposition treatment process is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the acidic activation tank in the acidification treatment process is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the cleaning tank in the cleaning and separating treatment process is not less than 10:1, and the unit of the volume-to-mass ratio is mL: g.
Preferably, the sewage treatment in the step (6) is specifically: and (3) treating the filtrate II, the filtrate III and the filtrate IV obtained in the steps (3) to (5) in sewage treatment equipment to obtain overflow and base liquid, recycling the overflow in a circulating water tank, performing solid-liquid separation on the base liquid in a filter press to obtain a filter cake V and filtrate V, allowing the filter cake V to enter a lead cake temporary storage area, and allowing the filtrate V to enter the sewage treatment equipment to repeat the operation.
Preferably, NaOH is added into the sewage treatment equipment in the step (6) to adjust the pH value and adjust the pH value in the sewage treatment equipment to be 8-10, and PAM is added to be a flocculating agent.
The invention has the beneficial effects that:
1. the invention discloses a soil remediation and lead recovery process for a lead-polluted site, which comprises the steps of screening the grade of the lead-polluted site soil, carbonizing the soil, decomposing, activating the soil, cleaning, treating filtrate, and then recovering lead resources. The method realizes the purposes of in-situ backfilling of the soil in the lead-polluted site and recycling of lead resources in the soil, avoids secondary pollution to the surrounding environment, and provides technical support for deep remediation and treatment of the soil in the lead-polluted site.
2. The technical scheme is adopted to treat the lead-polluted site soil, so that the organic-state, iron-manganese-oxidation-state and residue-state lead pollutants in the soil can be completely removed, the lead content in the soil can be reduced to be below a construction land soil pollution risk screening value, and the problems that the lead pollutants in the soil can not be completely separated from the soil and the lead resource in the soil can not be wasted in the prior art are solved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a flow chart of a soil remediation and lead recovery process for a lead contaminated site.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
The soil of a lead polluted site of an original factory site of a lead storage battery factory in a foot area of Chongqing city is taken as an experimental object to carry out the treatment of the soil remediation and lead recovery process, and the flow chart is shown in figure 1:
example 1
(1) Circulating water is utilized to prepare the following aqueous solution: 0.2mol/L NH4Aqueous OH solution, 0.15mol/L H2SiF6Say solution, 0.1mol/L of HNO3An aqueous solution;
(2) 10Kg of soil in the excavated lead-polluted site is fed into a circular vibrating screen for screening to obtain 0.61Kg of soil I with the size fraction larger than 100mm on the screen, and the lead content is determined to be 298.1mg/Kg, so that the soil can directly enter a coarse-grained soil temporary storage area due to lower lead content; while the soil with the size fraction less than or equal to 100mm under the screen enters a drum screen for wet screening, and the soil is continuously washed by circulating water in the wet screening process, so that the volume of the circulating water in the drum screen is ensured to be more than 27L (namely the volume ratio of liquid to solid in the drum screen is more than 3:1, and L: Kg);
(3) the soil after being screened by the drum screen is divided into soil II with the size fraction of 100-13 mm on the screen and soil III with the size fraction of less than or equal to 13mm under the screen, wherein the soil II enters the hammer type crusher to be crushed and then returns to the drum screen until the soil with the size fraction of less than or equal to 13mm is completely formed, and the soil with the size fraction of less than or equal to 13mm enters the carbonization tank;
(4) continuously adding 0.2mol/L NH into the carbonization tank4Carbonizing soil for 1h by using an OH aqueous solution, keeping the ratio of liquid to solid in a carbonization pool to be not less than 10:1 and L: Kg, separating the slurry after carbonization in a sedimentation centrifuge to obtain a filter cake I and a filtrate I, continuously feeding the filter cake I into a decomposition pool for further treatment, and feeding the filtrate I into the carbonization pool for recycling;
(5) continuously adding 0.15mol/L H into the decomposition tank2SiF6The water solution decomposes the soil for 1h, the ratio of liquid to solid in a decomposition pool is kept to be not less than 10:1, and L: Kg, the decomposed slurry enters a sedimentation centrifuge to be separated to obtain a filter cake II and a filtrate II, the filter cake II continues to enter an acid activation pool for further treatment, and the filtrate II enters sewage treatment equipment for treatment;
(6) continuously adding 0.1mol/L HNO into the acid activation tank3The water solution of (2) is used for carrying out acid activation treatment on soil for 1h, the ratio of liquid to solid in an acid activation pool is kept to be not less than 10:1, L: Kg, and the acid activity is keptThe slurry after the chemical reaction is separated in a sedimentation centrifuge to obtain a filter cake III and a filtrate III, the filter cake III is continuously treated in a cleaning tank, and the filtrate III is treated in sewage treatment equipment;
(7) continuously adding circulating water into the cleaning pool to clean the soil for 0.5h, keeping the ratio of liquid to solid in the cleaning pool to be not less than 10:1, and L: Kg, separating the washed slurry in a membrane filter press to obtain a filter cake IV and a filtrate IV, wherein the filter cake IV is the treated soil and can enter a clean soil temporary storage area, and the filtrate IV enters sewage treatment equipment to be treated;
(8) sequentially adding a Ph regulator (NaOH) and a flocculating agent (PAM) into the sewage treatment equipment, and regulating the pH value to be 8; after the treatment is finished, obtaining overflow and base liquid, wherein the overflow can directly enter a circulating water tank for recycling, the base liquid enters a box-type filter press for solid-liquid separation to obtain a filter cake V and a filtrate V, the filter cake V is a lead-containing pollutant and can enter a lead cake temporary storage area, and the filtrate V can return to sewage treatment equipment for repeated treatment until the discharge or use standard is reached;
(9) the soil treated by the above process was tested for size fraction and corresponding lead content, and the results are shown in table 1.
Example 2
(1) Circulating water is utilized to prepare the following aqueous solution: 0.2mol/L NH4Aqueous OH solution, 0.15mol/L H2SiF6Say solution, 0.1mol/L of HNO3An aqueous solution;
(2) 10Kg of soil in the excavated lead-polluted site is fed into a circular vibrating screen for screening to obtain 0.61Kg of soil I with the size fraction larger than 100mm on the screen, and the lead content is determined to be 298.1mg/Kg, so that the soil can directly enter a coarse-grained soil temporary storage area due to lower lead content; while the soil with the size fraction less than or equal to 100mm under the screen enters a drum screen for wet screening, and the soil is continuously washed by circulating water in the wet screening process, so that the volume of the circulating water in the drum screen is ensured to be more than 27L (namely the volume ratio of liquid to solid in the drum screen is more than 3:1, and L: Kg);
(3) the soil after being screened by the drum screen is divided into soil II with the size fraction of 100-13 mm on the screen and soil III with the size fraction of less than or equal to 13mm under the screen, wherein the soil II enters the hammer type crusher to be crushed and then returns to the drum screen until the soil with the size fraction of less than or equal to 13mm is completely formed, and the soil with the size fraction of less than or equal to 13mm enters the carbonization tank;
(4) continuously adding 0.2mol/L NH into the carbonization tank4Carbonizing soil for 1.5h by using an OH aqueous solution, keeping the ratio of liquid to solid in a carbonization tank to be not less than 10:1 and L: Kg, separating the carbonized slurry in a sedimentation centrifuge to obtain a filter cake I and a filtrate I, continuously feeding the filter cake I into a decomposition tank for further treatment, and feeding the filtrate I into the carbonization tank for recycling;
(5) continuously adding 0.15mol/L H into the decomposition tank2SiF6The water solution decomposes the soil for 1.5h, the ratio of liquid to solid in a decomposition pool is kept to be not less than 10:1, L: Kg, the mud after decomposition enters a sedimentation centrifuge for separation to obtain a filter cake II and a filtrate II, the filter cake II continues to enter an acid activation pool for further treatment, and the filtrate II enters sewage treatment equipment for treatment;
(6) continuously adding 0.1mol/L HNO into the acid activation tank3The water solution is used for carrying out acid activation treatment on the soil for 1.5h, the ratio of liquid to solid in an acid activation pool is kept to be not less than 10:1, L: Kg, the slurry after the acid activation is finished enters a sedimentation centrifuge for separation to obtain a filter cake III and a filtrate III, the filter cake III continues to enter a cleaning pool for further treatment, and the filtrate III enters sewage treatment equipment for treatment;
(7) continuously adding circulating water into the cleaning pool to clean the soil for 0.75h, keeping the ratio of liquid to solid in the cleaning pool to be not less than 10:1, and L: Kg, separating the washed slurry in a membrane filter press to obtain a filter cake IV and a filtrate IV, wherein the filter cake IV is the treated soil and can enter a clean soil temporary storage area, and the filtrate IV enters sewage treatment equipment to be treated;
(8) sequentially adding a Ph regulator (NaOH) and a flocculating agent (PAM) into the sewage treatment equipment, and regulating the pH value to 9; after the treatment is finished, obtaining overflow and base liquid, wherein the overflow can directly enter a circulating water tank for recycling, the base liquid enters a box-type filter press for solid-liquid separation to obtain a filter cake V and a filtrate V, the filter cake V is a lead-containing pollutant and can enter a lead cake temporary storage area, and the filtrate V can return to sewage treatment equipment for repeated treatment until the discharge or use standard is reached;
(9) the soil treated by the above process was tested for size fraction and corresponding lead content, and the results are shown in table 1.
Example 3
(1) Circulating water is utilized to prepare the following aqueous solution: 0.2mol/L NH4Aqueous OH solution, 0.15mol/L H2SiF6Say solution, 0.1mol/L of HNO3An aqueous solution;
(2) 10Kg of soil in the excavated lead-polluted site is fed into a circular vibrating screen for screening to obtain 0.61Kg of soil I with the size fraction larger than 100mm on the screen, and the lead content is determined to be 298.1mg/Kg, so that the soil can directly enter a coarse-grained soil temporary storage area due to lower lead content; while the soil with the size fraction less than or equal to 100mm under the screen enters a drum screen for wet screening, and the soil is continuously washed by circulating water in the wet screening process, so that the volume of the circulating water in the drum screen is ensured to be more than 27L (namely the volume ratio of liquid to solid in the drum screen is more than 3:1, and L: Kg);
(3) the soil after being screened by the drum screen is divided into soil II with the size fraction of 100-13 mm on the screen and soil III with the size fraction of less than or equal to 13mm under the screen, wherein the soil II enters the hammer type crusher to be crushed and then returns to the drum screen until the soil with the size fraction of less than or equal to 13mm is completely formed, and the soil with the size fraction of less than or equal to 13mm enters the carbonization tank;
(4) continuously adding 0.2mol/L NH into the carbonization tank4Carbonizing soil for 2 hours by using an OH aqueous solution, keeping the ratio of liquid to solid in a carbonization pool to be not less than 10:1 and L: Kg, separating the slurry after carbonization in a sedimentation centrifuge to obtain a filter cake I and a filtrate I, continuously feeding the filter cake I into a decomposition pool for further treatment, and feeding the filtrate I into the carbonization pool for recycling;
(5) continuously adding 0.15mol/L H into the decomposition tank2SiF6The water solution decomposes the soil for 2 hours, the ratio of liquid to solid in a decomposition pool is kept to be not less than 10:1, and L: Kg, the mud after decomposition enters a sedimentation centrifuge for separation to obtain a filter cake II and a filtrate II, the filter cake II continues to enter an acid activation pool for further treatment, and the filtrate II enters sewage treatment equipment for treatment;
(6) continuously adding 0.1mol/L HNO into the acid activation tank3The water solution is used for carrying out acid activation treatment on the soil for 2 hours, the ratio of liquid to solid in an acid activation pool is kept to be not less than 10:1, L: Kg, the slurry after the acid activation is finished enters a sedimentation centrifuge for separation to obtain a filter cake III and a filtrate III, the filter cake III continues to enter a cleaning pool for further treatment, and the filtrate III enters sewage treatment equipment for treatment;
(7) continuously adding circulating water into the cleaning pool to clean the soil for 1h, keeping the ratio of liquid to solid in the cleaning pool to be not less than 10:1, and L: Kg, separating the washed slurry in a membrane filter press to obtain a filter cake IV and a filtrate IV, wherein the filter cake IV is the treated soil and can enter a clean soil temporary storage area, and the filtrate IV enters sewage treatment equipment to be treated;
(8) sequentially adding a Ph regulator (NaOH) and a flocculating agent (PAM) into sewage treatment equipment, and regulating the pH value to be 10; after the treatment is finished, obtaining overflow and base liquid, wherein the overflow can directly enter a circulating water tank for recycling, the base liquid enters a box-type filter press for solid-liquid separation to obtain a filter cake V and a filtrate V, the filter cake V is a lead-containing pollutant and can enter a lead cake temporary storage area, and the filtrate V can return to sewage treatment equipment for repeated treatment until the discharge or use standard is reached;
(9) the soil treated by the above process was tested for size fraction and corresponding lead content, and the results are shown in table 1.
TABLE 1 size fraction and Pb content of the soil treated in examples 1 to 3
Control experiment:
the leaching technology in the prior art is adopted to repair the soil in the same place, the size fraction of the soil treated by the leaching technology and the corresponding lead content are tested, and the results are shown in table 2.
TABLE 2 Pb content in soil in the original lead-contaminated site and the soil treated by the leaching technique
| Particle size composition/mm | Content of each fraction/%) | Lead content/mg/kg in raw soil | Lead content/mg/kg in soil after leaching remediation |
| +100 | 6.1 | 357.3 | 251.7 |
| 100-13 | 5.5 | 834.6 | 292.11 |
| 13-5 | 4.3 | 2800.7 | 392.098 |
| 5-2 | 3.8 | 4276.7 | 855.34 |
| 2-1 | 8.4 | 6035.4 | 1508.85 |
| 1-0.25 | 10.1 | 10060.1 | 3018.03 |
| ＜0.25 | 61.8 | 18592.9 | 20795.7 |
| Total up to | 100 | 13364.1 | 13364.1 |
Note: the risk screening value of the lead pollutants of the construction land and the like is 400 mg/kg.
As can be seen from the determination results of the lead content in the tables 1 and 2, only 15.9% of the soil in the lead-polluted site meets the requirement of direct in-situ backfilling after the soil is restored by a leaching technology, and lead pollutants are enriched in the soil with the size fraction less than 0.25 mm. After the soil is repaired by the technical scheme of the invention, the content of lead in the soil of the site is obviously reduced, the lead content in the soil of each grade is smaller than the lead pollutant risk screening value of a land for construction and the like and is 400mg/kg standard, and the requirements of in-situ backfilling are all met; in addition, the lead content in the lead cake temporary storage area obtained by testing is about 80%, so that the recycling of lead resources in soil is realized, and the secondary pollution to the environment is avoided.
In summary, according to the soil remediation and lead recovery process for the lead-polluted site disclosed by the invention, the clean soil and the lead-containing filter cake are finally obtained through the treatment operation of lead resource recovery after the grain size screening, the carbonization treatment, the decomposition treatment and the acid activation treatment of the soil of the lead-polluted site, the cleaning and the filtrate treatment, so that the purposes of all in-situ backfilling of the soil of the lead-polluted site and the recovery and utilization of the lead resource in the soil are realized, the secondary pollution to the surrounding environment is avoided, and the technical guarantee is provided for the deep remediation and treatment of the soil of the lead-polluted site.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (4)
1. A soil remediation and lead recovery process for a lead contaminated site, the process comprising:
(1) screening and crushing the soil size fraction of the lead polluted site to obtain soil with the size fraction larger than 100mm and soil with the size fraction smaller than or equal to 13 mm;
(2) carbonizing the soil with the size fraction less than or equal to 13mm in the step (1), and settling and centrifuging to obtain a filter cake I;
(3) performing decomposition treatment on the filter cake I in the step (2), and performing sedimentation and centrifugation to obtain a filter cake II and a filtrate II;
(4) acidifying the filter cake II in the step (3), and performing sedimentation and centrifugation to obtain a filter cake III and a filtrate III;
(5) cleaning and separating the filter cake III in the step (4) to obtain a filter cake IV and a filtrate IV, wherein the filter cake IV is the clean soil;
(6) performing sewage treatment on the filtrate obtained in the steps (3) - (5), and performing solid-liquid separation after the treatment to obtain a filter cake V and a filtrate V, wherein the filter cake V is the lead recovery material;
the soil size fraction screening and crushing treatment of the lead-polluted site in the step (1) specifically comprises the following steps:
a. feeding the soil in the lead-polluted site into a circular vibrating screen for screening, feeding the soil I with the size fraction larger than 100mm on the screen into a coarse-grained soil temporary storage area, feeding the soil with the size fraction smaller than or equal to 100mm below the screen into a drum screen for wet screening to obtain soil II with the size fraction smaller than or equal to 100mm and larger than 13mm on the screen of the drum screen and soil with the size fraction smaller than or equal to 13mm below the screen of the drum screen, and washing the soil with circulating water in the wet screening process;
b. enabling the soil II to enter a hammer crusher, returning to a drum screen for wet screening after crushing, and repeating until the soil II becomes the soil with the size of less than or equal to 13mm below the screen of the drum screen;
the carbonization treatment in the step (2) is specifically as follows: the soil with the size fraction less than or equal to 13mm in the step (1) enters a carbonization tank, and 0.2mol/L NH is continuously added4Carbonizing an OH aqueous solution for 1-2 hours, and then performing sedimentation and centrifugation to respectively obtain a filter cake I and a filtrate I;
the decomposition treatment in the step (3) is specifically as follows: the filter cake I in the step (2) enters a decomposition pool, and 0.15mol/L H is continuously added2SiF6Decomposing the aqueous solution for 1-2 hours, and performing sedimentation and centrifugation after the decomposition is finished to respectively obtain a filter cake II and a filtrate II;
the acidification treatment in the step (4) is specifically as follows: the filter cake II in the step (3) enters an acid activation tank, and 0.1mol/L of HNO is continuously added3Acidizing the aqueous solution for 1-2 h, and settling and centrifuging after acidizing to respectively obtain a filter cake III and a filtrate III;
the sewage treatment in the step (6) is specifically as follows: and (3) treating the filtrate II, the filtrate III and the filtrate IV obtained in the steps (3) to (5) in sewage treatment equipment to obtain overflow and base liquid, recycling the overflow in a circulating water tank, performing solid-liquid separation on the base liquid in a filter press to obtain a filter cake V and filtrate V, allowing the filter cake V to enter a lead cake temporary storage area, and allowing the filtrate V to enter the sewage treatment equipment to repeatedly perform the treatment.
2. The soil remediation and lead recovery process for a lead-contaminated site as claimed in claim 1, wherein the cleaning and separation treatment in step (5) is specifically: and (4) cleaning the filter cake III in a cleaning pool for 0.5-1 h by using circulating water, separating in a membrane filter press after cleaning to obtain a filter cake IV and a filtrate IV, and feeding the filter cake IV into a clean soil temporary storage area.
3. The soil remediation and lead recovery process for a lead-contaminated site as claimed in claim 1, wherein the volume-to-mass ratio of the liquid to the solid in the carbonation tank during the carbonation treatment is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the decomposition tank during the decomposition treatment is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the acidic activation tank during the acidification treatment is not less than 10:1, the volume-to-mass ratio of the liquid to the solid in the cleaning tank during the cleaning and separation treatment is not less than 10:1, and the unit of the volume-to-mass ratio is mL: g.
4. The soil remediation and lead recovery process for a lead-contaminated site according to claim 1, wherein NaOH is added to the sewage treatment equipment in the step (6) to adjust the pH value of the sewage treatment equipment to 8-10, and PAM is added to the sewage treatment equipment to serve as a flocculant.
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