CN114669591B - Wet detoxification process for hexavalent chromium contaminated soil - Google Patents
Wet detoxification process for hexavalent chromium contaminated soil Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
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- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
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Abstract
The application relates to the technical field of hexavalent chromium contaminated soil remediation, and particularly discloses a wet detoxification process for hexavalent chromium contaminated soil. The wet detoxification process for the hexavalent chromium contaminated soil comprises the following steps: (1) detecting the concentration of hexavalent chromium in the soil before remediation; (2) Crushing the polluted soil by a wet ball milling process to obtain slurry; (3) Adding the slurry into a reaction tank, synchronously adding an acidic regulator and the slurry for mixing when the slurry is added into the reaction tank with the volume of 1/5-1/4 of the volume of the reaction tank, and synchronously adding the slurry and a reducing agent for filling when the volume of the reaction tank is 1/3-1/2 of the volume of the reaction tank to obtain a mixed solution; (4) Adding the mixed solution into a microbial carbon source agent, and keeping for 1-2 hours to obtain a soil mixed solution; (5) And dehydrating the soil mixed solution to obtain the repaired soil. The concentration of hexavalent chromium in the repaired hexavalent chromium soil is low, the soil quality standard is met, and meanwhile, the repaired soil is stable.
Description
Technical Field
The application relates to the technical field of hexavalent chromium contaminated soil remediation, in particular to a wet detoxification process for hexavalent chromium contaminated soil.
Background
The soil environment is an open system, and the quality of the soil environment is influenced by superposition of multiple factors. Due to the rapid growth of urban population and the rapid development of industrial economy, solid wastes are stacked and dumped on the surface of soil, harmful wastewater permeates into the soil, harmful substances in the atmosphere fall into the soil, and the loss of pollutants or leakage of pipes/tanks in the industrial production process is a way to cause soil pollution. Chromium is also one of the main soil pollutants in China.
Chromium generally exists in two valence states of trivalent chromium and hexavalent chromium in soil, the trivalent chromium is easily adsorbed or precipitated by soil colloid in the soil, and the toxic effect is light; hexavalent chromium has strong oxidation effect, strong water solubility, stimulation and corrosion effect on skin and mucosa, and is a common sensitizer, and the toxicity of hexavalent chromium can rapidly enter cells through easy diffusion and nonspecific anion channels on cell membranes, thereby affecting human health.
Aiming at the problem that the soil polluted by high-concentration hexavalent chromium is usually detoxified by a wet detoxification process so as to reduce the content of the hexavalent chromium in the soil, the wet detoxification process mainly comprises the steps of wet ball milling, water dissolving, hydrolysis, reduction and the like, so that the hexavalent chromium in the soil is converted into trivalent chromium, and the detoxification of the soil polluted by the chromium is completed.
In view of the above-mentioned related technologies, the inventor believes that hexavalent chromium contaminated soil is generally alkaline, sulfuric acid is added to acidify after slurry is filled in a reduction tank, acid-base reaction is severe, and a large amount of acid foam is generated to attach to the liquid level of the slurry, thereby affecting the detoxification effect of chromium contaminated soil.
Disclosure of Invention
In order to improve the detoxification effect of the high-concentration hexavalent chromium contaminated soil, the application provides a wet detoxification process of the hexavalent chromium contaminated soil.
In a first aspect, the application provides a wet detoxification process of hexavalent chromium contaminated soil, which adopts the following technical scheme: a hexavalent chromium contaminated soil wet detoxification process comprises the following steps:
(1) And (3) detecting the concentration of hexavalent chromium: detecting the concentration of hexavalent chromium in the soil before remediation;
(2) Soil crushing: crushing the polluted soil by a wet ball milling process to obtain slurry;
(3) And (3) slurry treatment: adding the slurry obtained in the step (2) into a reaction tank, synchronously adding an acidic regulator and the slurry for mixing when the slurry is added into the reaction tank with the volume of 1/5-1/4 of the volume of the reaction tank, and synchronously adding the slurry and a reducing agent for filling when the volume of the reaction tank is 1/3-1/2 of the volume of the reaction tank to obtain a mixed solution;
(4) Treating the mixed solution: adding the mixed solution obtained in the step (3) into a microbial carbon source agent, and keeping for 1-2 hours to obtain a soil mixed solution; the microbial carbon source medicament is mainly prepared from the following raw materials in parts by weight: 10-20 parts of cane sugar molasses and 10-20 parts of beet molasses;
(5) And (3) dehydration treatment: and (5) dehydrating the soil mixed liquor obtained in the step (4) to obtain the repaired soil.
Preferably, the soil is ground and crushed by a 120-200 mesh sieve in the step (2); the mass ratio of the soil to the steel balls is 1.5.
Preferably, the acidic regulator in step (3) is sulfuric acid, and the pH is adjusted to 4.
Preferably, the method for preparing the reducing agent in the step (3) comprises the following steps: dissolving ferrous sulfate in water, wherein the mass ratio of the ferrous sulfate to the water is 1.
Preferably, the mass ratio of the reducing agent to the soil is 1.
By adopting the technical scheme, after the soil is ground in the step (2), slurry is obtained, a part of slurry is added into the reaction tank, then the acid regulator and a part of slurry are simultaneously added into the reaction tank, the slurry reacts with the acid regulator, the pH of the slurry is adjusted, meanwhile, the intensity of acid-base reaction is slowed down, acid foam generated by acid-base reaction is reduced, synchronously, the reducing agent and the rest of slurry are continuously and synchronously added, so that the reducing agent can reduce hexavalent chromium in the reaction tank, chromium hydroxide sediment is obtained, hexavalent chromium is reduced, the content of hexavalent chromium in the soil is reduced, and the discharge standard is reached; the addition of the microbial carbon source agent in the step (4) is convenient for further improving the soil remediation effect, the sucrose molasses and the beet molasses in the microbial carbon source agent contain reducing sugar which has reducibility and is convenient for further improving the cleaning of hexavalent chromium in soil, meanwhile, the reducing sugar does not influence the detection of hexavalent chromium in soil, after the saccharic acid salt is dissolved in water, the saccharic acid salt is convenient for cleaning by washing, and meanwhile, the reducing sugar easily loses activity under the conditions of high temperature and strong alkali, so that the concentration of hexavalent chromium in soil is further reduced.
Preferably, the mass ratio of the microbial carbon source medicament to the mixture in the step (4) is (0.1-0.5): 100.
By adopting the technical scheme, when the adding amount of the microbial carbon source medicament in the step (4) is higher, the microbial carbon source medicament is easy to waste, so that the cost of chromium pollution treatment in soil is increased, when the adding amount of the microbial carbon source medicament is lower, hexavalent chromium in the mixed solution cannot be reduced better, so that more hexavalent chromium is caused in soil, the soil detoxification effect is poor, when the ratio of the adding amount of the microbial carbon source medicament to the mixed solution is (0.1-0.5): 100, hexavalent chromium ions in the mixed solution can be reduced better, the cost is lower, and the treatment efficiency of chromium pollution in soil can be improved better.
Preferably, the press filtrate is obtained after the dehydration treatment in the step (5), and the repaired soil obtained in the step (5) is subjected to maintenance treatment through the press filtrate.
By adopting the technical scheme, the press filtrate after dehydration has Fe which does not participate in reaction 2+ The chromium hydroxide is convenient to change into trivalent chromium ions due to the change of the external environment, and is further oxidized into hexavalent chromium by natural oxidants in soil, and Fe in the filter press liquid 2+ Is convenient for further reducing hexavalent chromium, thereby improving the detoxification stability of chromium-contaminated soil.
Preferably, the step (5) is dehydrated to obtain a pressure filtrate, and the pressure filtrate is used for introducing into the ball milling stage in the step (2) or dissolving the reducing agent in the step (3).
By adopting the technical scheme, the reduction agent is dissolved in the press filtrate, so that the addition of the reduction agent is convenient to reduce, the cost of treating chromium-polluted soil is reduced, and meanwhile, fe in the press filtrate 2+ The hexavalent chromium ions are further reduced conveniently, so that the hexavalent chromium ions in the repaired soil are reduced.
Preferably, steel balls are added in the ball milling in the step (2), and the grading of the steel balls is as follows: phi 100mm 30-40%, phi 80mm 40-50% and phi 60mm 29-35%.
By adopting the technical scheme, the steel balls with larger particle size have enough energy to crush the chromium slag in the soil, so that the chromium slag is crushed into small particles, sufficient collision frequency is generated between the steel balls with smaller particle size and the small chromium slag particles, the small chromium slag particles are further crushed, the particle size of the chromium slag is further reduced, the leaching rate of hexavalent chromium in the chromium slag is improved, and the detoxification effect on chromium-polluted soil is improved.
Preferably, the repairing agent in the step (4) is a microbial carbon source agent, and the microbial carbon source agent is mainly prepared from the following raw materials in parts by weight: 10-20 parts of cane sugar molasses, 10-20 parts of beet molasses, 20-30 parts of potato powder, 10-15 parts of cassava dregs, 10-15 parts of soybean meal and 5-10 parts of pectin powder.
By adopting the technical scheme, the potatoes contain glucose, fructose, sucrose and phosphate ester of sugar, the sucrose has certain reducibility after hydrolysis, and simultaneously the glucose and the fructose in the potatoes have reducibility, so that the hexavalent chromium content in the repaired soil can be further reduced conveniently; the cassava residues contain amylose which contains more glucose, so that the concentration of hexavalent chromium in soil can be further reduced; the bean pulp contains a large amount of phytic acid, the phytic acid is convenient to reduce the pH value of the mixture, so that the leaching rate of hexavalent chromium ions is improved, and the N-acetylglucosamine contained in the bean pulp is used for improving the reduction efficiency of hexavalent chromium; the pectin powder is mainly linear polysaccharide, the main chain is D-galacturonic acid, and multiple components are matched together, so that the concentration of hexavalent chromium in soil is reduced.
Preferably, the step (3) further comprises a defoaming agent, the defoaming agent and the acidic regulator are synchronously added into the reaction tank, and the defoaming agent is composed of dialkynyl polyethylene glycol, polydimethylsiloxane and nonylphenol polyoxyethylene ether according to the mass ratio of (3-5) to (2-3).
Preferably, the mass ratio of the defoaming agent to the slurry is (1-3): 100.
By adopting the technical scheme, on one hand, the addition of the defoaming agent eliminates acid foam generated by acid-base reaction, thereby facilitating reduction of incomplete acidification caused by the existence of the acid foam and further improving the detoxification efficiency of soil; the dialkynyl polyethylene glycol has certain defoaming performance, so that the bubble surfactant can be solubilized conveniently, the effective concentration can be reduced, the bubble surfactant can be dissolved into the surfactant adsorption layer, the compactness among the molecules of the surfactant can be reduced, and meanwhile, the dialkynyl polyethylene glycol contains carbon-carbon triple bonds and a plurality of hydroxyl groups, so that hexavalent chromium ions can be reduced conveniently, and the content of the hexavalent chromium ions in the mixed solution can be reduced; polydimethylsiloxane has strong hydrophobicity, is easy to generate spreading and adsorption of foaming agent molecules in an aqueous system, and takes away a layer of solution adjacent to the surface during spreading, so that the foam liquid becomes thin, and bubbles are broken; the nonylphenol polyoxyethylene ether facilitates dispersing active ingredients into small particles, and the small particles are dispersed in water, so that the nonylphenol polyoxyethylene ether and the dialkynyl polyethylene glycol and the polydimethylsiloxane jointly act, acid foam generated in the stirring process is reduced, and the detoxification effect of the soil is improved.
Preferably, in the step (3), fe in the mixed solution is detected every 5-8min 2+ The reaction progress is judged according to the concentration of (1).
Preferably, fe is mixed in the solution 2+ The concentration detection method is used for detecting Fe in the mixed solution according to the detection method in the national standard MT/T368-2005' determination method of iron ions in coal mine Water 2+ And (4) concentration.
By adopting the technical scheme, fe in the mixture is detected 2+ By judging the concentration of Fe 2+ Concentration of (1), fe 2+ Used for reducing hexavalent chromium into trivalent chromium, and Fe in the mixture when the concentration of hexavalent chromium in the mixture is low 2+ The concentration of the chromium-containing compound tends to be stable, so that the judgment reaction is thorough, and the detoxification efficiency of the chromium-polluted soil is improved.
Preferably, fe in the mixed solution after the reaction in the step (3) 2+ The mass concentration of (A) is 0.5-1g/L.
By adopting the technical scheme, when the mass concentration of the divalent ferrous ions is 0.5-1g/L, on one hand, the judgment of lower hexavalent chromium content in the mixture is facilitated, the soil emission standard is facilitated, and when the ferrous ion concentration is too high, the concentration of the reducing agent is easily caused to be too high, so that the treatment cost of chromium pollution in soil is caused to be too high.
Preferably, grinding aid is added while the soil is added in the wet grinding in the step (1), and the grinding aid consists of triisopropanolamine, cane sugar molasses, sodium sulfide and citric acid residue in a mass ratio of (10-15): (3-8): 5-10.
Preferably, the citric acid residues comprise the following components in percentage by weight: 3.12% of silicon oxide, 0.13% of ferric oxide, 0.41% of aluminum oxide, 41.36% of calcium oxide, 0.11% of magnesium oxide, 40.20% of sulfur trioxide, 18.32% of crystal water and 9.10% of water.
Preferably, the mass ratio of the grinding aid to the soil is (0.5-0.8): 100.
Preferably, the particle size of the citric acid residues is 5-10mm.
By adopting the technical scheme, grinding aid molecules are adsorbed on the surface of the chromium slag, the surface energy of chromium slag particles is reduced, the position of crystal lattices close to a surface layer is caused to migrate, and the defects of points or lines are generated, so that the strength and the hardness of the chromium slag particles are reduced, meanwhile, the grinding aid permeates into micro cracks of the particles, a strong wedge splitting effect is generated, the cracks are prevented from healing and crack expansion is accelerated, the grinding aid is adsorbed on the particle surface of the chromium slag material, redundant electrons generated by the fracture of chemical bonds are neutralized, and the active points are prevented from being mutually attracted, so that the dispersity and the flowability of the chromium slag are improved; triisopropanolamine belongs to polar organic substances, and 0H and-CH are contained in hydroxypropyl 3 Two end groups, namely hydroxyl-0H, are easily adsorbed on chromium slag particles, so that triisopropanolamine molecules shield active points on the new section of the particles and play a wedge splitting role at a micro-crack. alkyl-CH in triisopropanolamine 3 The chromium slag particles are extended outwards, so that the agglomeration of the chromium slag particles can be prevented, and the dispersibility is improved; the main component of the molasses is a carbohydrate substance which contains more-0H and is easy to adsorb on the chromium slag particles, so that redundant charges are shielded, the particles are prevented from agglomerating, and the dispersibility of the chromium slag is improved; therefore, the molasses has a good grinding-aiding effect on the chromium slag; the sodium sulfide is used as one of the grinding aids, so that on one hand, the grinding efficiency of the chromium slag is improved, the particle size of chromium slag particles is further reduced, and the sulfide ions have reducibility, so that hexavalent chromium in the slurry can be reduced conveniently in the ball milling process, and the content of hexavalent chromium in the chromium slag can be reduced conveniently; the citric acid residue reduces the particle size in the soil grinding process on one handThe leaching rate of hexavalent chromium in the soil is improved, and meanwhile, the citric acid residues have certain acidity, so that the leaching rate of hexavalent chromium is further improved, and the detoxification efficiency of the soil is further improved.
In summary, the present application has the following beneficial effects:
1. according to the wet detoxification process of the hexavalent chromium contaminated soil, the slurry subjected to ball milling, the acid regulator and the reducing agent are added in batches to be mixed, so that acid foam generated by violent reaction between the acid regulator and the slurry is reduced, the leaching amount of hexavalent chromium is increased, and the concentration of hexavalent chromium in the soil after restoration is increased.
2. According to the wet detoxification process of the hexavalent chromium contaminated soil, after the mixture containing hexavalent chromium ions is reduced, a microbial carbon source medicament is further added, so that the concentration of hexavalent chromium in the soil can be further reduced.
Detailed Description
The present application will be described in further detail with reference to examples.
The soil comes from the polluted soil of the chromium slag yard, and the concentration range of the hexavalent chromium in the soil is 500-800mg/kg.
The chromium slag in the soil comprises the following components in percentage by weight: 3.22% of chromium oxide, 5.65% of ferric oxide, 9.48% of aluminum oxide, 16.8% of silicon dioxide, 18.45% of magnesium oxide, 30.79% of calcium oxide, 0.32% of water-soluble chromium, 0.49% of acid-soluble chromium and water immersion pH of more than 10.
Examples
Example 1
The wet detoxification process for the hexavalent chromium contaminated soil comprises the following steps:
(1) And (3) detecting the concentration of hexavalent chromium: detecting the concentration of hexavalent chromium in the soil; the soil is from polluted soil of a chromium slag storage yard, and the concentration range of hexavalent chromium in the soil is 600mg/kg;
(2) Soil crushing: crushing soil by a wet ball milling process to obtain slurry; wherein the average grain diameter of the ground slurry is 200 meshes; the mass ratio of the steel balls to the soil is 1.5; the grading of the steel balls is as follows: phi 100mm 30%, phi 80mm 40%, phi 60mm30%;
(3) And (3) slurry treatment: adding the slurry obtained in the step (2) into a reaction tank, synchronously adding an acidic regulator and the slurry for mixing when the slurry is added to the volume of 1/4 of the volume of the reaction tank, regulating the pH value in the reaction tank to be 4, synchronously adding the slurry and a reducing agent for filling when the volume of the reaction tank is 1/2, and detecting Fe in the reaction tank every 5min 2+ When Fe in the reaction tank is detected 2+ When the concentration is less than 1g/L, obtaining a mixed solution; wherein the acidity regulator is sulfuric acid; the preparation method of the reducing agent comprises the following steps: dissolving ferrous sulfate in water, wherein the mass ratio of the ferrous sulfate to the water is 1; the mass ratio of the reducing agent to the soil is 1; wherein, fe is contained in the mixed solution 2+ The concentration detection method is used for detecting Fe in the mixed solution according to the detection method in the national standard MT/T368-2005' determination method of iron ions in coal mine Water 2+ Concentration;
(4) Treating the mixed solution: adding the mixed solution obtained in the step (3) into a microbial carbon source agent, and keeping for 1h to obtain a soil mixed solution; the mass ratio of the microbial carbon source medicament to the mixed solution is 0.1, wherein the microbial carbon source medicament is mainly prepared from the following raw materials in parts by weight: 10kg of cane sugar molasses and 10kg of beet molasses;
(5) And (3) dewatering treatment: and (4) dehydrating the soil mixed liquor obtained in the step (4) to respectively obtain the repaired soil and the filter pressing liquor, wherein the filter pressing liquor is added into the ball mill in the step (2).
Example 2
The present embodiment is different from embodiment 1 in that: adding the slurry obtained in the step (2) into a reaction tank, synchronously adding an acidic regulator and the slurry for mixing when the slurry is added into the reaction tank with the volume of 1/5 of the volume of the reaction tank, and synchronously adding the slurry and a reducing agent when the volume of the reaction tank is 1/2 of the volume of the reaction tank to obtain a mixed solution; spraying the repaired soil every 5 days with the press filtrate obtained in the step (5), dissolving the reducing agent in the step (3) with the press filtrate obtained in the step (5), and the rest is completely the same as the embodiment 1.
Example 3
The present embodiment is different from embodiment 1 in that: the mass ratio of the microbial carbon source medicament to the mixture in the step (4) is 0.5.
Example 4
The present embodiment is different from embodiment 1 in that: the microbial carbon source medicament in the step (4) is prepared from the following raw materials in parts by weight: 10kg of cane sugar molasses, 10kg of beet molasses, 20kg of potato powder, 10kg of cassava dregs, 10kg of bean pulp and 5kg of pectin powder. The rest is exactly the same as in example 1.
Example 5
The present embodiment is different from embodiment 1 in that: the microbial carbon source medicament in the step (4) is prepared from the following raw materials in parts by weight: 15kg of cane sugar molasses, 15kg of beet molasses, 25kg of potato powder, 13kg of cassava residue, 13kg of soybean meal and 8kg of pectin powder. The rest is exactly the same as in example 1.
Example 6
The present embodiment is different from embodiment 1 in that: the microbial carbon source medicament in the step (4) is prepared from the following raw materials in parts by weight: 20kg of cane sugar molasses, 20kg of beet molasses, 30kg of potato powder, 15kg of cassava dregs, 15kg of soybean meal and 10kg of pectin powder. The rest is exactly the same as in example 1.
Example 7
This embodiment is different from embodiment 6 in that: and (3) slurry treatment: adding the slurry obtained in the step (2) into a reaction tank, synchronously adding an acidic regulator, the slurry and a defoaming agent for mixing when the slurry is added into the reaction tank with the volume of 1/4 of the volume of the reaction tank, and synchronously adding the slurry and a reducing agent when the volume of the reaction tank is 1/2 of the volume of the reaction tank to obtain a mixed solution; the defoaming agent consists of dialkynyl polyethylene glycol, polydimethylsiloxane and nonylphenol polyoxyethylene ether according to the mass ratio of 3.
Example 8
This embodiment is different from embodiment 7 in that: step (2) soil crushing: crushing soil, steel balls and grinding aid by a wet ball milling process to obtain slurry; wherein the grinding aid consists of triisopropanolamine, molasses, sodium sulfide and citric acid residues according to a mass ratio of 10.
Comparative example
Comparative example 1
The comparative example differs from example 1 in that: and (3) slurry treatment: adding the slurry obtained in the step (2), an acidic regulator and a reducing agent into a reaction tank together, filling, regulating the pH value to 4, and mixing to obtain a mixed solution; the rest is exactly the same as in example 1.
Comparative example 2
This comparative example differs from example 1 in that: and (3) slurry treatment: filling the slurry obtained in the step (2) into a reduction tank, adding an acidic regulator and a reducing agent, regulating the pH to 4, and mixing to obtain a mixed solution; the rest is exactly the same as in example 1.
Comparative example 3
The wet detoxification process of the hexavalent chromium contaminated soil in the comparative example comprises the following steps:
(1) And (3) detecting the concentration of hexavalent chromium: detecting the concentration of hexavalent chromium in the soil;
(2) Soil crushing: crushing soil by a wet ball milling process to obtain slurry;
(3) And (3) slurry treatment: adding the slurry obtained in the step (2) into a reaction tank, synchronously adding an acidic regulator and the slurry for mixing when the slurry is added into the reaction tank with the volume of 1/5-1/4, synchronously adding the slurry and a reducing agent for filling when the volume of the reaction tank is 1/3-1/2, and regulating the pH value to 4 to obtain a mixed solution;
(4) And (3) dewatering treatment: and (4) dehydrating the mixed solution obtained in the step (3) to obtain the repaired soil.
Performance test
And (3) detecting the concentration of hexavalent chromium: the soil after remediation obtained in examples 1 to 8 and comparative examples 1 to 3 was subjected to detection of the concentration of hexavalent chromium in the soil according to HJ908-2017 "flow injection for determination of water quality hexavalent chromium-dibenzoyl dihydrazide photometry", and the detection results are shown in table 1.
And (3) detecting the leaching concentration of hexavalent chromium: the restored soils obtained in examples 1 to 8 and comparative examples 1 to 3 were measured for the leaching amount of hexavalent chromium in the soil according to HJ/T299 "sulfuric acid-nitric acid method for leaching toxicity of solid waste", and the measurement results are shown in table 1.
TABLE 1 detection of hexavalent chromium concentrations in soil after remediation of examples 1-8 and comparative examples 1-3
| Serial number | Hexavalent chromium concentration mg/kg | The leaching concentration of hexavalent chromium is mg/kg |
| Example 1 | 3.13 | 0.038 |
| Example 2 | 3.25 | 0.032 |
| Example 3 | 2.87 | 0.031 |
| Example 4 | 2.41 | 0.023 |
| Example 5 | 2.46 | 0.025 |
| Example 6 | 2.39 | 0.021 |
| Example 7 | 2.16 | 0.018 |
| Example 8 | 2.01 | 0.015 |
| Comparative example 1 | 5.01 | 0.051 |
| Comparative example 2 | 5.58 | 0.055 |
| Comparative example 3 | 4.89 | 0.047 |
In combination with the soil treated in the embodiments 1 to 8, the concentration of hexavalent chromium is reduced to 2.01 to 3.25mg/kg, the concentration of repaired hexavalent chromium is lower than the standard of soil for the second type of land in the soil pollution risk control standard (trial) for soil environmental quality construction land (GB 36600 to 2018), the leaching concentration of hexavalent chromium is reduced to 0.015 to 0.038mg/kg, and the leaching concentration of hexavalent chromium after repair is lower than the pollution control index limit value when chromium slag is used as a roadbed material and concrete aggregate in the technical specification of chromium slag pollution control and environmental protection (provisional). The concentration of hexavalent chromium in the soil repaired by the detoxification process and the leaching concentration of hexavalent chromium both meet the requirements of the current national standard.
By combining the example 1 and the comparative examples 1 to 3 and combining the table 1, it can be seen that the soil is ground into slurry, and the slurry, the acidity regulator and the reducing agent are added into the reaction tank in batches, so that acid foams generated in the reaction process can be reduced, the leaching amount of hexavalent chromium in the soil can be influenced, the treatment of the hexavalent chromium in the soil can be further influenced, and the addition of the microbial carbon source agent can be used for further repairing the hexavalent chromium in the soil, so that the concentration of the hexavalent chromium in the repaired soil can be further reduced.
As can be seen by combining examples 1 to 3 with table 1, the slurry obtained by grinding the soil, the acid regulator and the reducing agent are added into the reaction tank in batches, so that the influence of acid foam on the leaching amount of hexavalent chromium in the soil is reduced, and the microbial carbon source agent is combined, so that the cleaning of hexavalent chromium in the soil is further improved.
By combining the examples 4-6 and the table 1, it can be seen that the microbial carbon source medicament is prepared by mixing and compounding sucrose molasses, beet molasses, potato powder, cassava dregs, bean pulp and pectin powder, wherein the sucrose molasses, the beet molasses, the potato powder and the cassava dregs contain reducing sugar, and have wide sources and low cost, thereby further treating hexavalent chromium in soil, the phytic acid contained in the bean pulp facilitates leaching of the hexavalent chromium in the soil,
by combining examples 6-8 and table 1, it can be seen that the addition of the grinding aid facilitates the improvement of the fineness of the ground soil and the improvement of the leaching amount of hexavalent chromium in the soil, and further reduces the leaching amount of the repaired soil, and the addition of the defoamer facilitates the reduction of the influence of acid foam on the leaching amount of hexavalent chromium in the soil, and further facilitates the reduction of the concentration of hexavalent chromium in the repaired soil, thereby improving the repair efficiency of the soil polluted by chromium.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (8)
1. A hexavalent chromium contaminated soil wet detoxification process is characterized by comprising the following steps:
(1) And (3) detecting the concentration of hexavalent chromium: detecting the concentration of hexavalent chromium in the soil before remediation;
(2) Soil crushing: crushing the polluted soil by a wet ball milling process to obtain slurry; adding a grinding aid while adding soil by wet ball milling, wherein the grinding aid consists of triisopropanolamine, sucrose molasses, sodium sulfide and citric acid residues in a mass ratio of (10-15) to (3-8) to (5-10);
(3) And (3) slurry treatment: adding the slurry obtained in the step (2) into a reaction tank, adding the slurry into the reaction tank when the volume of the reaction tank is 1/5-1/4, then simultaneously adding an acidic regulator and a part of slurry into the reaction tank, and continuously and synchronously adding a reducing agent and the rest of slurry when the volume of the reaction tank is 1/3-1/2 to obtain a mixed solution;
(4) Treating the mixed solution: adding the mixed solution obtained in the step (3) into a microbial carbon source agent, and keeping for 1-2 hours to obtain a soil mixed solution; the microbial carbon source medicament is prepared from the following raw materials in parts by weight: 10-20 parts of cane sugar molasses, 10-20 parts of beet molasses, 20-30 parts of potato powder, 10-15 parts of cassava dregs, 10-15 parts of soybean meal and 5-10 parts of pectin powder;
(5) And (3) dewatering treatment: and (5) dehydrating the soil mixed liquor obtained in the step (4) to obtain the repaired soil.
2. The wet detoxification process for hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: the mass ratio of the microbial carbon source medicament to the mixed solution in the step (4) is (0.1-0.5): 100.
3. The wet detoxification process for hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: and (4) obtaining press filtrate after dehydration treatment in the step (5), and maintaining the repaired soil obtained in the step (5) through the press filtrate.
4. The wet detoxification process for hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: and (5) obtaining a press filtrate after dehydration treatment, wherein the press filtrate is used for introducing into the ball milling stage in the step (2) and/or dissolving the reducing agent in the step (3).
5. The wet detoxification process for hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: adding steel balls in the ball milling in the step (2), wherein the grading of the steel balls is as follows: phi 100mm 30-40%, phi 80mm 40-50% and phi 60mm 29-35%.
6. The wet detoxification process for hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: the step (3) also comprises a defoaming agent, wherein the defoaming agent and the acidic regulator are synchronously added into the reaction tank, and the defoaming agent consists of dialkynyl polyethylene glycol, polydimethylsiloxane and nonylphenol polyoxyethylene ether according to the mass ratio of (3-5) to (2-3).
7. The wet detoxification process of hexavalent chromium contaminated soil according to claim 1, wherein the wet detoxification process comprises the following steps: in the step (3), fe in the mixed solution is detected every 5-8min 2+ The reaction progress is judged according to the concentration of (1).
8. The wet detoxification process for hexavalent chromium contaminated soil according to claim 7, wherein the wet detoxification process comprises the following steps: the mixed solution after the reaction in the step (3)Middle Fe 2+ The mass concentration of (b) is 0.5-1g/L.
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