CN110340134B - Method for in-situ filling and restoring polluted soil - Google Patents
Method for in-situ filling and restoring polluted soil Download PDFInfo
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- CN110340134B CN110340134B CN201910649218.2A CN201910649218A CN110340134B CN 110340134 B CN110340134 B CN 110340134B CN 201910649218 A CN201910649218 A CN 201910649218A CN 110340134 B CN110340134 B CN 110340134B
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- 239000002689 soil Substances 0.000 title claims abstract description 104
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000011049 filling Methods 0.000 title claims abstract description 41
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 15
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 20
- 239000004115 Sodium Silicate Substances 0.000 claims abstract description 19
- 229920002401 polyacrylamide Polymers 0.000 claims abstract description 19
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052911 sodium silicate Inorganic materials 0.000 claims abstract description 19
- 125000000129 anionic group Chemical group 0.000 claims abstract description 18
- 238000012423 maintenance Methods 0.000 claims abstract description 9
- 239000007864 aqueous solution Substances 0.000 claims description 43
- 239000003795 chemical substances by application Substances 0.000 claims description 31
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 25
- 239000011575 calcium Substances 0.000 claims description 25
- 229910052791 calcium Inorganic materials 0.000 claims description 25
- 239000005077 polysulfide Substances 0.000 claims description 25
- 229920001021 polysulfide Polymers 0.000 claims description 25
- 150000008117 polysulfides Polymers 0.000 claims description 25
- 230000008439 repair process Effects 0.000 claims description 23
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 10
- 239000012190 activator Substances 0.000 claims description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 5
- 239000011651 chromium Substances 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 238000005067 remediation Methods 0.000 abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 23
- 239000003344 environmental pollutant Substances 0.000 description 13
- 231100000719 pollutant Toxicity 0.000 description 13
- 238000002386 leaching Methods 0.000 description 12
- 230000035699 permeability Effects 0.000 description 12
- 239000000243 solution Substances 0.000 description 11
- 238000002347 injection Methods 0.000 description 10
- 239000007924 injection Substances 0.000 description 10
- 229910001385 heavy metal Inorganic materials 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 229910052785 arsenic Inorganic materials 0.000 description 7
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 6
- 239000012153 distilled water Substances 0.000 description 6
- 239000003814 drug Substances 0.000 description 6
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 6
- 239000000945 filler Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 238000004891 communication Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 239000013543 active substance Substances 0.000 description 3
- 239000000084 colloidal system Substances 0.000 description 3
- 239000000356 contaminant Substances 0.000 description 3
- 238000011109 contamination Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000035515 penetration Effects 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 239000002910 solid waste Substances 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 2
- 239000012752 auxiliary agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000013003 healing agent Substances 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000013049 sediment Substances 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- 238000004017 vitrification Methods 0.000 description 2
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- QPCDCPDFJACHGM-UHFFFAOYSA-N N,N-bis{2-[bis(carboxymethyl)amino]ethyl}glycine Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(=O)O)CCN(CC(O)=O)CC(O)=O QPCDCPDFJACHGM-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 238000003321 atomic absorption spectrophotometry Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000002419 base digestion Methods 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 229910001430 chromium ion Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910001447 ferric ion Inorganic materials 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000035876 healing Effects 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- ZODDGFAZWTZOSI-UHFFFAOYSA-N nitric acid;sulfuric acid Chemical compound O[N+]([O-])=O.OS(O)(=O)=O ZODDGFAZWTZOSI-UHFFFAOYSA-N 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229960003330 pentetic acid Drugs 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- NSVHDIYWJVLAGH-UHFFFAOYSA-M silver;n,n-diethylcarbamodithioate Chemical compound [Ag+].CCN(CC)C([S-])=S NSVHDIYWJVLAGH-UHFFFAOYSA-M 0.000 description 1
- 238000003900 soil pollution Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C2101/00—In situ
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Soil Sciences (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention belongs to the technical field of soil remediation, and particularly relates to a method for in-situ filling and remediation of polluted soil. The method for repairing the polluted soil by injecting the repairing reagent comprising sodium silicate and anionic polyacrylamide into the polluted soil for maintenance is simple, efficient and low in cost, and can be used for treating different polluted soil.
Description
Technical Field
The invention belongs to the technical field of soil remediation, and particularly relates to a method for in-situ filling and remediation of polluted soil.
Background
The existing soil repairing technology is divided into three types of physical repairing, chemical repairing and biological repairing according to principles, wherein the physical repairing comprises a direct soil replacement method, a thermalization method, a vitrification repairing method and an electrode driving repairing method; chemical repair includes solidification-stabilization, leaching, and oxidation-reduction; bioremediation includes techniques such as phytoremediation, microbial remediation, and biological combination remediation.
Although the repairing method can relieve the soil pollution problem to a certain extent, the repairing method has defects of different degrees in the treatment process, such as large soil replacement project amount by a direct soil replacement method, difficult treatment of polluted soil and high cost, which is equivalent to the process of digging an east wall and repairing a west wall, and is difficult to apply on a large scale; the thermalization method has high energy consumption and limits the application of the method; the vitrification repair method needs high temperature and high pressure, and also has the problems of high energy consumption and high cost; the electrode driving repair method is only suitable for soil with higher humidity, needs to consume a large amount of electric energy, has higher cost and has certain danger.
The solidification-stabilization technology is to fix pollutants in a pollution medium to enable the pollutants to be in a long-term stable state, is a rapid control and restoration method which is commonly applied to soil heavy metal pollution, and has obvious advantages for simultaneously treating various heavy metal composite polluted soil; the method has the defects that the volume of the treated soil is increased, broken stone or underground barriers need to be removed before engineering implementation, and the pollutants and the stabilizer are difficult to mix uniformly; the leaching technology is a restoration method for injecting water or water solution containing a flushing aid, acid-base solution, complexing agent or surfactant and other leaching agents into polluted soil or sediment, and eluting and cleaning pollutants in the soil, and the method has the defects that the leaching agent is generally expensive, difficult to popularize and use, large in engineering quantity and has the risk of secondary pollution; oxidation-reduction techniques are carried out by adding chemical oxidizing agents, e.g. ozone, hydrogen peroxide, potassium permanganate, etc. or reducing agents, e.g. SO, to the soil 2 FeO, gaseous H 2 S and the like, and the purpose of purifying the soil is achieved by making the S and the like chemically react with the pollutant. In general, the chemical oxidation method is suitable for repairing the soil and the underground water polluted by organic matters at the same time, and has the advantages of narrow application range, high cost and high risk of medicament pollution.
The biological repair method has the advantages of simple operation, low cost, less disturbance to the environment and difficult secondary pollution, but the method has long repair period, more severe requirements on repair conditions, easy influence of external environment change and wide application range.
In conclusion, the existing soil restoration method still cannot realize efficient restoration of polluted soil.
Disclosure of Invention
The invention aims to provide a method for repairing polluted soil by in-situ filling, which utilizes the in-situ filling principle to stabilize and solidify the polluted soil and is simple and quick.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for repairing polluted soil by in-situ filling, which comprises the steps of injecting a repairing reagent comprising sodium silicate and anionic polyacrylamide into the polluted soil for maintenance.
Preferably, the repair agent is injected in the form of an aqueous solution; the mass concentration of sodium silicate in the aqueous solution is 8-20%, and the concentration of anionic polyacrylamide is 1.0-1.5 g/L.
Preferably, the repair agent further comprises an activator comprising hydrochloric acid and/or phosphoric acid.
Preferably, the repair agent further comprises calcium polysulfide.
Preferably, the calcium polysulfide is injected in the form of an aqueous solution, and the mass concentration of the aqueous solution of the calcium polysulfide is 2.5-3%.
Preferably, when the repair agent includes calcium polysulfide, the aqueous solution of calcium polysulfide is injected alternately with the aqueous solution of sodium silicate and anionic polyacrylamide.
Preferably, the contaminated soil comprises heavy metal contaminated soil or non-heavy metal inorganic contamination.
Preferably, when repairing a gravel or grit formation, the repair agent further includes a solid filler.
Preferably, the solid filler comprises cement and/or clay.
The invention provides a method for repairing polluted soil by in-situ filling, which comprises the steps of injecting a repairing reagent comprising sodium silicate and anionic polyacrylamide into the polluted soil for maintenance. The invention utilizes the reaction between the anionic polyacrylamide and sodium silicate, pollutants and water to generate sediment and colloid in the soil body, stabilizes the pollutants and blocks a pollution channel, thereby achieving the purposes of quickly repairing the polluted soil and improving the soil strength. The embodiment results show that the method provided by the invention is simple, efficient and low in cost, and can be used for treating different polluted soil; in the treatment process, the repairing effect is better according to the pollutants contained in the soil to be treated and the corresponding stabilizing agents.
Drawings
FIG. 1 is a schematic diagram of a soil restoration effect test device according to the present invention;
in the figure, 1-medicament canister; 2-a distilled water tank; 3-three-way valve; 4-filling the soil column; 5-a liquid spraying receiving device; 6-a flange of a sieve pore; 7-a cover; 8-a three-way valve; 9-a filtrate tank.
Detailed Description
In the following embodiments, the reagents described in the present invention are commercially available products well known to those skilled in the art.
The invention provides a method for repairing polluted soil by in-situ filling, which comprises the steps of injecting a repairing reagent comprising sodium silicate and anionic polyacrylamide into the polluted soil for maintenance.
In the present invention, the repair agent is preferably injected in the form of an aqueous solution. The dissolved water in preparing the aqueous solution of the repair agent can be tap water, industrial recycled water, river water or rainwater. In the aqueous solution of the repairing reagent, the mass concentration of sodium silicate is preferably 8-20%, more preferably 10-18%, and still more preferably 12-15%; the concentration of the anionic polyacrylamide is preferably 1.0 to 1.5g/L, and may be specifically 1.0g/L, 1.1g/L, 1.2g/L, 1.3g/L, 1.4g/L or 1.5g/L. The preparation method of the aqueous solution has no special requirement, and the components are mixed according to the concentration content to obtain the aqueous solution with uniform dispersion.
In the present invention, the repair agent preferably further comprises an activator, preferably comprising hydrochloric acid and/or phosphoric acid, more preferably phosphoric acid or hydrochloric acid. In the invention, the activating agent is used for adjusting the pH of the repairing agent, so that the repairing agent can react with pollutants in polluted soil to form a precipitate, and the repairing agent is promoted to form colloid; in addition, the activating reagent can also influence the gel time and gel strength of the repairing reagent, so that the in-situ filling effect is ensured.
In the present invention, the amount of the active agent is preferably controlled according to the kind of the pollution source in the polluted soil:
when the pollution source in the polluted soil is heavy metal, the dosage of the active agent preferably enables the pH value of the aqueous solution of the repairing agent to reach 8.5-10, more preferably 9-9.5;
when the source of contamination in the contaminated soil is arsenic contaminant, the amount of active agent is preferably such that the pH of the aqueous remediation agent solution reaches 8 to 10, more preferably 8.5 to 10.
In the present invention, the repair agent preferably further comprises calcium polysulfide or ferric chloride, which is preferably injected in the form of an aqueous solution. The present invention preferably stabilizes hexavalent chromium ions by calcium polysulfide, in aqueous solution of which calcium polysulfide (CaS 5 ) And Cr in polluted soil 6+ The molar ratio of (2) is preferably 3 to 5:1, more preferably 4 to 5:1, wherein Cr 6+ The concentration of (2) is obtained by detection. In the invention, the calcium polysulfide aqueous solution refers to a mixed feed liquid of calcium polysulfide and water, and does not comprise sodium silicate or anionic polyacrylamide so as to avoid the reaction of all components and influence the repairing effect.
The present invention preferably stabilizes the arsenic contaminant by ferric chloride, preferably in a molar ratio of ferric ions to arsenic of 3 to 6:1, more preferably 4 to 6:1, still more preferably 6:1. When the arsenic-polluted soil is treated, the ferric chloride is preferably injected in a solution mode, and the concentration of the ferric chloride in the solution is not particularly required, so that the ferric chloride can be uniformly dispersed.
In the invention, injection refers to the process of penetrating a fluid component into the soil inner layer, and the injection mode can be pressurized penetration or gravity penetration under natural conditions. The method has no special requirement on the injection mode of the aqueous solution of the repairing reagent, and can be used for one-time injection or batch injection. In the present invention, when calcium polysulfide is included in the repair agent, the aqueous solution of calcium polysulfide is preferably injected alternately with the aqueous solution of sodium silicate and anionic polyacrylamide, more preferably by injecting the aqueous solution of calcium polysulfide first and then the aqueous solution of sodium silicate and anionic polyacrylamide.
In the present invention, when the restoration agent is used at the concentration described in the above technical scheme, the volume of the restoration agent is preferably 20 to 60%, more preferably 25 to 50% of the volume of the soil body to be restored, which is obtained by two parameters of the pollution diffusion area and the pollution penetration depth. In the present invention, when the healing agent further comprises an aqueous solution of calcium polysulfide, the volume of the calcium polysulfide solution is preferably 30 to 60%, more preferably 40 to 50%, of the total volume of the healing agent.
In the present invention, the contaminated soil preferably includes heavy metal contaminated soil or non-heavy metal inorganic contaminated soil, which preferably includes arsenic contaminated soil, by the kind of the contamination source. In the present invention, when the restoration of a gravel or grit formation is performed, the restoration agent preferably further comprises a solid filler, preferably comprising cement and/or clay. In the present invention, when a solid filler is included in the remediation agent, the solid filler is preferably dispersed in an aqueous solution of sodium silicate and anionic polyacrylamide, and then injected into the contaminated soil.
After the repairing reagent is injected into the polluted soil, the invention cures the polluted soil injected with the repairing reagent, and each component in the repairing reagent reacts with the pollutant and water in the curing process to generate precipitate and colloid, fill gaps in the soil, block the propagation path of a pollution source and achieve the purpose of filling and repairing the polluted soil in situ. In the present invention, the curing time is preferably 2 to 7 days, more preferably 3 to 5 days.
In order to characterize the application effect of the technical scheme, the invention provides a device shown in fig. 1 for experiment and detection:
in fig. 1, a soil filling column 4 is vertically arranged and used for filling heavy metal polluted soil samples, an upper port of the soil filling column 4 is connected with a medicament tank 1 and a distilled water tank 2 through a three-way valve 3, and a flange 6 and a cover 7 with sieve holes are arranged at the upper port; a leaching solution receiving container 5 is arranged at the lower port of the filling column 4; the three-way valve 8 is used for connecting the filling column 4, the filtrate tank 9 and the leachate receiving container 5.
The invention also provides a using method of the detecting device, and the using method preferably comprises the following steps:
paving soil sample layers in the soil filling columns 4, tamping the soil sample layers by layers, and then vertically fixing the soil filling columns 4 filled with the soil sample; and connecting the components in the manner of fig. 1;
the communication valve 3 is adjusted to enable the distilled water tank 2 and the filling column 4 to be in a communication state; the filling column 4 and the drenching liquid receiving device 5 are adjusted to be in a communicated state; injecting distilled water, and receiving the filtered liquid to obtain initial permeate;
adjusting the non-communication state between the filling column 4 and the drenching liquid receiving device 5, enabling the medicament filling 1 and the filling column 4 to be in communication state, injecting part of the aqueous solution of the gelatinizing agent into the filling column 4, injecting part of the aqueous solution of the inorganic auxiliary agent into the filling column 4 through the medicament tank 1 to form alternate injection, repeating the injection step of the aqueous solution of the gelatinizing agent and the injection step of the aqueous solution of the inorganic auxiliary agent, and finally injecting the aqueous solution of the gelatinizing agent for the last time; after injection, maintaining the soil body; during maintenance, the lower valve of the three-way valve 8 is closed, and the side valve is opened;
the filling column 4 and the drenching liquid receiving device 5 are adjusted to be in a communicating state, and the distilled water storage tank 2 and the filling column 4 are adjusted to be in a communicating state, so that distilled water is injected into the filling column 4; and (3) adjusting the lower valve of the three-way valve 8 to be opened, closing the side valve, and collecting filtered liquid which is the repaired permeate.
In the invention, the treatment effect of the polluted soil is preferably characterized by the filling rate and the pollutant content in the repaired penetrating fluid. In the invention, the filling rate is calculated by (permeability before filling-permeability after filling)/permeability before filling, and the soil filling rate after the polluted soil is restored by the method is more than or equal to 90 percent.
The present invention preferably characterizes the healing effect by the permeability coefficient (permeability), which is preferably calculated by the following method:
the permeability coefficient is obtained through constant head permeation experiment test. As shown in fig. 1: in the test, a sample with a section S and a length L is filled in the soil filling column 4, and a water valve is opened to enable water to flow through the soil sample from top to bottom and be discharged from a water outlet (a lower port of the soil filling column). After the head difference (Δh) and the exudation flow (Q) are stabilized, measuring the amount of water (V) flowing through the soil sample over a certain time (t), then:
V＝Q·t＝ν·S·t；
v=k·i, then v=k· (Δh/L) ·s·t, according to darcy' S law, giving:
k＝Q·L/(S·△h)；
in the above formula, v represents the permeation speed, k represents the permeation coefficient, i represents the hydraulic gradient, Q represents the seepage flow, Δh represents the head difference, and L represents the soil body length.
For further explanation of the present invention, a method for in situ filling remediation of contaminated soil provided by the present invention is described in detail below with reference to the accompanying drawings and examples, which are not to be construed as limiting the scope of the present invention.
Example 1
Soil body test sample filling is carried out by adopting a one-dimensional organic glass column, and an experimental device is shown in fig. 1: the inner diameter multiplied by length of the simulated column is 10cm multiplied by 20cm, flanges with sieve holes (with the inner diameter of 0.2 mm) uniformly distributed are arranged at two ends of the column, and then a layer of filter paper is paved to play roles in uniformly distributing water and preventing the medium of the aquifer from leaking. The simulation column is vertically arranged, the solution enters from the upper end of the simulation column, and the lower end of the simulation column is provided with a water outlet; experimental media are added from the bottom of the column in batches and tamped layer by layer to avoid layering non-uniformity.
The device is used for measuring the permeability of polluted soil, specifically, a soil sample to be measured (taken from a chromium polluted site in a new country, the water content of the soil is 9.0%) is provided with 8 columns, 3 columns are used for measuring the initial permeability, and 5 columns are used for measuring the permeability after treatment of a repairing reagent; injecting an aqueous solution of sodium silicate and anionic polyacrylamide into a soil body at one time, and curing for 7 days; during maintenance, the lower valve of the three-way valve 8 is closed, and the side valve is opened; before the permeability test, the lower valve of the three-way valve 8 is opened, and the side valve is closed; and (5) carrying out a permeability test after maintenance, and detecting the concentration of pollutants in the leaching liquid. Other parameters are listed in table 1.
Preparing an aqueous solution with the mass concentration of 10% of sodium silicate and the concentration of 1.5g/L of anionic polyacrylamide (the pH value is regulated to be=9 by hydrochloric acid) and an aqueous solution with the mass concentration of 3% of calcium polysulfide as repair reagent aqueous solutions, firstly, injecting the aqueous solution of calcium polysulfide into a soil body at one time, then injecting the mixed aqueous solution of sodium silicate and polyacrylamide into the soil body at one time, wherein the volume of the repair reagent aqueous solution accounts for 1/2 of the volume of the soil body (the volume fraction of the aqueous solution of calcium polysulfide accounts for 40% of the total volume of the aqueous solution of the repair reagent), curing for 7 days at normal temperature, measuring the permeability of the soil body, calculating the filling rate, and measuring the result as shown in table 1.
Hexavalent chromium in soil is tested by adopting an alkali digestion flame atomic absorption spectrophotometry (HJ 687-2014).
Example 2
A lead-containing contaminated soil sample was treated as described in example 1, except that calcium polysulfide was not used and phosphoric acid was used as an activator to adjust the pH of the remediation agent to 10.
The effective state content of lead in the soil is determined by adopting a diethylene triamine pentaacetic acid leaching-inductively coupled plasma emission spectrometry (HJ 804-2016), and the leaching solution of the lead in the soil is prepared and determined according to a solid waste leaching toxicity leaching method acetic acid buffer solution method (HJ/T300-2007).
Example 3
The soil body containing arsenic contaminants (from a site contaminated with arsenic in a hillock) was tested As in example 1, the remediation agent replaced calcium polysulfide with ferric chloride (molar ratio of Fe/as=6), hydrochloric acid As activator, pH 10.0, and the test method was the same As in example 1.
The leaching solution is prepared by adopting a sulfuric acid nitric acid method (HJ/T299-2007) of a solid waste leaching toxicity leaching method, and is measured according to a silver diethyldithiocarbamate spectrophotometry for measuring solid waste arsenic (GB/T15555.3-1995).
The test results are shown in Table 1.
TABLE 1 compositions and amounts of the agents of examples 1 to 3 and their repairing effects
The test results of examples 1 to 3 show that the method provided by the invention can utilize the injected sodium silicate and anionic polyacrylamide to carry out in-situ filling and solidification on the soil when the polluted soil is restored, thereby increasing the compactness of the soil body, reducing the permeability of the polluted soil area, reducing the diffusion of a pollution source to other non-polluted areas or underground water bodies, and further achieving the purpose of restoring the polluted soil.
As can be seen from the contents of the above embodiments, the method provided by the invention is to fill the pores and cracks of the polluted soil in situ, block the polluted migration channel, and bond soil particles, repairing reagent and pollution source in the polluted soil into a whole, which is equivalent to multiple protection, greatly reduces the environmental risk and has strong practicability.
The medicament raw material provided by the invention is green and environment-friendly, and the secondary environment risk is low; the source is wide, and the cost of raw materials is reduced. The preparation method and the use method of the aqueous solution of the repairing agent for injection are simple, the restriction of the polluted soil area is avoided, and the method is particularly suitable for polluted stratum such as a silty layer, a fine sand layer, a middle sand layer and the like, in which pollutants are easy to migrate; the maintenance time is short, and the time cost is reduced.
Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.
Claims (1)
1. The in-situ filling and restoring method for polluted soil includes the steps of injecting restoring reagent comprising sodium silicate and anionic polyacrylamide into polluted soil for maintenance;
the repair agent is injected in the form of an aqueous solution; the mass concentration of sodium silicate in the aqueous solution is 8-20%, and the concentration of anionic polyacrylamide is 1.0-1.5 g/L;
the repair agent further comprises an activator comprising hydrochloric acid and/or phosphoric acid;
the repair reagent further comprises calcium polysulfide;
the calcium polysulfide is injected in the form of aqueous solution, and the mass concentration of the calcium polysulfide aqueous solution is 2.5-3%;
when the repair reagent comprises calcium polysulfide, the aqueous solution of the calcium polysulfide and the aqueous solution of sodium silicate and anionic polyacrylamide are alternately injected;
the polluted soil is chromium polluted soil.
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