CN112108509A - Method for removing arsenic, cadmium and lead in field soil by using combined eluent in synergy mode - Google Patents
Method for removing arsenic, cadmium and lead in field soil by using combined eluent in synergy mode Download PDFInfo
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Abstract
The invention discloses a method for removing arsenic, cadmium and lead in field soil by using a combined eluent in a synergistic manner. According to the invention, the biodegradable chelating agent and the low-molecular organic acid are combined to obtain the combined eluent, the combined eluent is used for ectopic treatment of field soil, the removal rate of arsenic in the field soil is not lower than 30%, the removal rate of cadmium and lead is not lower than 60%, the components in the combined eluent can synergistically improve the removal rate of arsenic, cadmium and lead in the polluted field soil, and the removal rate of the combined eluent on arsenic, cadmium and lead is greatly improved.
Description
Technical Field
The invention relates to a method for removing arsenic, cadmium and lead in field soil by using a matched eluent in a synergistic manner, belonging to the technical field of heavy metal contaminated soil remediation.
Background
In recent years, the industry of China is rapidly developed, and serious heavy metal pollution exists in the heavy nonferrous metal ore (containing associated ores) mining and selecting industry (copper, lead zinc, nickel cobalt, tin, antimony and mercury ore mining and selecting industry and the like), heavy nonferrous metal smelting industry (copper, lead zinc, nickel cobalt, tin, antimony and mercury smelting and the like), lead storage battery manufacturing industry, leather and product industry (leather tanning processing and the like), chemical raw material and product manufacturing industry (calcium carbide method polyvinyl chloride industry, chromium salt industry and the like), electroplating industry and the like in important industries. Large-scale industrial structure adjustment and industrial enterprise relocation are carried out in each big city in China, so that a large amount of residual heavy metal pollution sites are generated. The most prominent pollution is arsenic, cadmium and lead, and the arsenic and the cadmium and lead are difficult to remove simultaneously due to different existing forms in the soil, so that the soil of the arsenic, cadmium and lead polluted site needs to be repaired and treated by selecting a proper soil repairing technology urgently.
The leaching method in the chemical remediation technology is widely used due to good remediation effect and short remediation period, and can thoroughly remove heavy metals in soil. Therefore, the method is of great importance for exploring an eluting agent which has little influence on the physical and chemical properties of soil and can efficiently and synergistically remove arsenic, cadmium and lead in field soil.
Disclosure of Invention
Aiming at the problems and the defects in the existing arsenic-cadmium-lead polluted site soil remediation, the invention aims to provide the method for removing the arsenic, cadmium and lead in the site soil by using the compound eluent, the compound eluent is obtained by combining the biodegradable chelating agent and the low-molecular organic acid, and the compound eluent is used for the ectopic treatment of the site soil, so that the removal rate of the arsenic, cadmium and lead in the site soil can be greatly improved.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a method for removing arsenic, cadmium and lead from field soil by using a combined eluent comprises the steps of combining a biodegradable chelating agent and a low-molecular organic acid to obtain a combined eluent, and then using the combined eluent for ectopic treatment of the field soil to remove the arsenic, cadmium and lead from the field soil.
The field soil in the invention is the field soil with various texture types such as sand, soil, stickiness and the like polluted by arsenic, cadmium and lead.
Preferably, the concentration ratio of the biodegradable chelating agent to the low-molecular organic acid is 1: 5-2: 1, the pH value of the formulated eluent is 3-7.
Preferably, the biodegradable chelating agent is selected from one or more of EDDS, MGDA, GLDA, HIDS and IDSA.
Preferably, the low molecular organic acid is selected from one or more of formic acid, acetic acid, malonic acid, citric acid, ascorbic acid, oxalic acid, tartaric acid and fumaric acid.
Preferably, the liquid-solid ratio of the compound eluting agent to the field soil is 10-25: 1, the ectopic treatment is mixing and stirring at a speed of 100--1The time is 30-120min, and the temperature is 10-50 ℃.
Preferably, a vulcanizing agent is added into leachate obtained by separating mud from water after the ex-situ treatment, the liquid-solid ratio of the leachate to the vulcanizing agent is 10-50:1, and the leachate is stirred for 15-120min at the temperature of 10-50 ℃ and is used for precipitating arsenic, cadmium and lead in the leachate.
More preferably, the vulcanizing agent is selected from one or more of potassium sulfide, sodium sulfide, aluminum sulfide, barium sulfide and calcium sulfide.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. in the existing arsenic-cadmium-lead polluted site soil, the arsenic and the cadmium-lead are difficult to be removed simultaneously due to different forms of the arsenic and the cadmium-lead in the soil. The inventor finds that the removal rate of single components such as a biodegradable chelating agent and low-molecular organic acid on arsenic in the soil of the polluted site is not higher than 10%, the removal rate of cadmium is not higher than 40%, and the removal rate of lead is not higher than 20%; the removal rate of arsenic, cadmium and lead in the field soil is not lower than 30%, the removal rate of cadmium and lead is not lower than 60%, the removal rate of arsenic, cadmium and lead in the contaminated field soil can be synergistically improved by the components in the compound eluting agent, and the removal rate of arsenic, cadmium and lead in the compound eluting agent is greatly improved.
2. According to the invention, a vulcanizing agent is added into the leachate obtained by separating mud from water after the ectopic treatment, the recovery of arsenic, cadmium and lead is realized through precipitation and purification, and the leachate can be recycled.
3. The compound eluting agent can be used for treating various types of arsenic, cadmium and lead polluted site soil, and is particularly suitable for sandy and soil type polluted site soil.
Drawings
FIG. 1 is a graph showing the effect of MGDA, ascorbic acid and formulated leacheate in example 1 on the appearance of arsenic (a), cadmium (b) and lead (c) in contaminated site soil;
FIG. 2 is a graph showing the effect of GLDA, citric acid and formulated eluent in example 2 on the appearance of arsenic (a), cadmium (b) and lead (c) in contaminated site soil;
FIG. 3 is a graph showing the effect of HIDS, tartaric acid and a formulated eluent in example 3 on the appearance of arsenic (a), cadmium (b) and lead (c) in contaminated site soil;
FIG. 4 is a graph of the effect of EDDS, malonic acid and a formulated eluent in example 4 on the appearance of arsenic (a) cadmium (b) lead (c) in contaminated site soil;
FIG. 5 is a graph of the effect of MGDA, acetic acid and formulated eluent in example 5 on the appearance of arsenic (a), cadmium (b) and lead (c) in contaminated site soil;
FIG. 6 is a graph showing the effect of IDSA, oxalic acid and formulated eluent on the appearance of arsenic (a), cadmium (b) and lead (c) in the soil of the contaminated site in example 6.
Detailed Description
The technical solution of the present invention will be described in detail with reference to the following embodiments, but the examples are not intended to limit the present invention.
Example 1
The sample is taken from soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 974.80 mg-kg-1、410.50mg·kg-1And 14730mg kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172 mg/kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 10: 1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing MGDA and ascorbic acid, and the concentration ratio of the MGDA to the ascorbic acid is 1: 4, preparing the eluting agent with the pH value of 3 at the temperature of 25 ℃ at 200 r.min-1Stirring for 60min, and under the same conditions, using the same amount of MGDA as the single component of the formulated lotion (same amount of MGDA as the formulated lotion, No. M1)Ascorbic acid (same amount of ascorbic acid in the formulated lotion, code K1), and separate rinses with MGDA (same sum of MGDA and ascorbic acid in the formulated lotion, code M2) and ascorbic acid (same sum of MGDA and ascorbic acid in the formulated lotion, code K2) in the same amount as the formulated lotion. The leaching rates of the leaching agents on arsenic, cadmium and lead in the polluted soil are calculated and shown in the table 1:
TABLE 1 removal rate of As, Cd and Pb in field soil by different eluents
Adding sodium sulfide into the leachate at a liquid-solid ratio of 25:1, stirring at 25 deg.C for 90min, filtering, separating to obtain Realgar, CdS precipitate, PbS precipitate and tail liquid, recovering the arsenic, cadmium and lead contents in leachate at 87%, 80% and 82%, and recycling the tail liquid.
The inventors found that, when MGDA, ascorbic acid and a combination eluent are used to treat the contaminated soil, the change of arsenic, cadmium and lead forms is shown in FIGS. 1(a), (b) and (c), and it is clear from the figure that, after MGDA is leached alone, arsenic in the obligatory adsorption state, the binding state of iron aluminum oxide hydrate with weak crystallization and the binding state of iron aluminum oxide hydrate with crystallization is increased by 4.59 mg/kg-1And a reduction of 55.68 mg/kg-1And a reduction of 50.32mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 149.63 mg/kg-1And a reduction of 10.71 mg/kg-1And an increase of 43.53mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1157.48 mg/kg-1、865.75mg·kg-1And 138.62mg kg-1After ascorbic acid is washed independently, arsenic in an obligatory adsorption state, a combined state of iron aluminum oxide hydrate with weak crystallization and a combined state of iron aluminum oxide hydrate with crystallization is reduced by 0.74 mg/kg-1、150.13mg·kg-1And 102.96mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 129.84 mg/kg-1、17.94mg·kg-1And 7.98mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 192.28 mg/kg-1、132.50mg·kg-1And 1357.73mg kg-1After being mixed with MGDA and ascorbic acid and washed, the arsenic in the obligatory adsorption state, the combined state of weak crystal hydrated iron-aluminum oxide and the combined state of crystal hydrated iron-aluminum oxide is respectively reduced by 21.08 mg/kg-1、212.92mg·kg-1And 201.50mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 186.88 mg/kg-1、29.12mg·kg-1And 69.69mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1338 mg/kg-1、3780.40mg·kg-1And 4438.53mg kg-1。
Example 2
The sample is taken from sandy soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 683.20 mg-kg-1、386.50mg·kg-1And 12547mg kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172 mg/kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 20:1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing GLDA and citric acid, and the concentration ratio of the GLDA to the citric acid is 3: 8, preparing the eluting agent with the pH value of 3 at the temperature of 25 ℃ at 200 r.min-1Is stirred for 90min and under the same conditions, a separate rinse is performed with GLDA (same amount as GLDA in the formulation) and citric acid (same amount as citric acid in the formulation) in the same amounts as the individual components in the formulation. The leaching rates of the leaching agents on arsenic, cadmium and lead in the polluted soil are calculated and shown in the table 2:
TABLE 2 removal rate of As, Cd and Pb in field soil by different eluents
| Arsenic removal Rate (%) | Cadmium removal Rate (%) | Lead removal (%) | |
| GLDA | 5.53％ | 38.00％ | 15.75％ |
| Citric acid | 6.25％ | 36.78％ | 6.87％ |
| Compound eluting agent | 38％ | 67％ | 65％ |
Adding potassium sulfide into the leachate at a liquid-solid ratio of 20:1, stirring at 30 ℃ for 60min, filtering and separating to obtain realgar, CdS precipitate, PbS precipitate and tail liquid, wherein the recovery rates of arsenic, cadmium and lead in the leachate are respectively 84%, 78% and 80%, and the obtained tail liquid is returned for reuse.
The inventor finds that after the GLDA, the citric acid and the compound eluting agent are used for treating the polluted soil, the arsenic, the cadmium and the lead are subjected to morphological changes as shown in figure 2(a), (b), (c) and (d)b) As shown in (c), it is found that, when GLDA was washed alone, the amount of arsenic in the form of obligatory adsorption, weakly crystalline hydrated iron-aluminum oxide bound state and crystalline hydrated iron-aluminum oxide bound state was reduced by 14.27 mg/kg, respectively, as compared with the original soil-1、32.65mg·kg-1And 7.36mg kg-1The cadmium in acid extractable state, reducible state and residue state are respectively reduced by 97.23 mg.kg-1、8.74mg·kg-1And 13.77mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1026.72 mg/kg-1、664.04mg·kg-1And 256.74mg kg-1After citric acid is washed independently, arsenic in an obligatory adsorption state, a combined state of iron-aluminum oxide hydrate with weak crystallization and a combined state of iron-aluminum oxide hydrate with crystallization is reduced by 26.02 mg/kg-1、16.24mg·kg-1And 3.06mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 105.34 mg/kg-1、16.79mg·kg-1And 5.62mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 438.28 mg/kg-1、32.56mg·kg-1And 376.75mg kg-1After the combination of GLDA and citric acid is washed, arsenic in an obligatory adsorption state, a weak-crystallization iron-aluminum oxide hydrate combined state and a crystallization iron-aluminum oxide hydrate combined state is respectively reduced by 34.82 mg/kg-1、182.15mg·kg-1And 156.74mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 179.12 mg/kg-1、30.53mg·kg-1And 39.31mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1283.65 mg/kg-1、5563.28mg·kg-1And 4063.56mg kg-1。
Example 3
The sample is taken from sandy soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 683.20 mg-kg-1、386.50mg·kg-1And 12547mg kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172mg·kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 10: 1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing HIDS and tartaric acid, and the concentration ratio of the HIDS to the tartaric acid is 2: 5, preparing the eluting agent with the pH value of 3 at the temperature of 25 ℃ at 250 r.min-1Is stirred for 30min and under the same conditions, separate rinses are performed with the same amounts of HIDS (same amount of HIDS in the combination rinse, code H1), tartaric acid (same amount of tartaric acid in the combination rinse, code J1) as the individual components in the combination rinse, and with the same amounts of HIDS (same sum of HIDS and tartaric acid in the combination rinse, code H2), tartaric acid (same sum of HIDS and tartaric acid in the combination rinse, code J2) as the combination rinse. The leaching rates of the leaching agents on arsenic, cadmium and lead in the polluted soil are calculated and shown in the table 3:
TABLE 3 removal rate of As, Cd and Pb in field soil by different eluents
| Arsenic removal Rate (%) | Cadmium removal Rate (%) | Lead removal (%) | |
| HIDS(H1) | 4.39％ | 30.00％ | 17.94％ |
| Tartaric acid (J1) | 8.37％ | 13.76％ | 16.86％ |
| HIDS(H2) | 8.63％ | 34.05％ | 19.72％ |
| Tartaric acid (J2) | 6.57％ | 21.29％ | 18.41％ |
| Compound eluting agent | 40％ | 65％ | 68％ |
Adding sodium sulfide into the leachate at a liquid-solid ratio of 25:1, stirring at 30 deg.C for 120min, filtering and separating to obtain Realgar, CdS precipitate, PbS precipitate and tail liquid, wherein the recovery rates of arsenic, cadmium and lead in the leachate are 90%, 88% and 85%, respectively, and the obtained tail liquid is reused.
The inventors found that when contaminated soil was treated with HIDS, tartaric acid and a combination eluent, arsenic, cadmium and lead were changed in the forms shown in FIGS. 3(a), (b) and (c), and it was found that when HIDS was eluted alone, arsenic in the obligatory adsorption state, the weakly crystalline hydrated iron-aluminum oxide bound state and the crystalline hydrated iron-aluminum oxide bound state were 21.35 mg/kg, respectively, as compared with the original soil-1、8.76mg·kg-1And 5.89mg kg-1The cadmium in acid extractable state, reducible state and residue state is respectively reduced by 76.84 mg.kg-1And a reduction of 18.67 mg/kg-1And an increase of 7.65mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 887.36 mg/kg-1、587.37mg·kg-1And 776.2mg kg-1After tartaric acid is singly washed, arsenic in an obligatory adsorption state, a weak-crystal bonded state of hydrated iron-aluminum oxide and a crystal bonded state of hydrated iron-aluminum oxide are respectively reduced by 18.43 mg/kg-1、28.97mg·kg-1And 16.35mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 20.83 mg.kg-1、7.65mg·kg-1And 18.97mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 162.73 mg/kg-1、342.61mg·kg-1And 1588.72mg kg-1After the HIDS and the tartaric acid are combined and washed, the arsenic in an obligatory adsorption state, a weak-crystal bonded ferric aluminum oxide state and a crystal bonded ferric aluminum oxide state is respectively reduced by 35.08 mg/kg-1、159.82mg·kg-1And 89.75mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 176.37 mg/kg-1、26.53mg·kg-1And 43.26mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1283.25 mg/kg-1、4874.63mg·kg-1And 2530.44mg kg-1。
Example 4
The sample is taken from soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 974.80 mg-kg-1、410.50mg·kg-1And 14730mg kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172 mg/kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 25:1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing EDDS and malonic acid, and the concentration ratio of EDDS to malonic acid is 2: 9, the pH value of the compound eluting agent is 4, and the temperature is lower than 30 ℃ at 300 r.min-1Is stirred for 45min and under the same conditions, a separate rinse is performed with the same amount of EDDS (same amount of EDDS in the formulation) and malonic acid (same amount of malonic acid in the formulation) as the single components in the formulation. Is calculated byThe leaching rates of the leaching agents on the arsenic, cadmium and lead in the polluted soil are shown in the table 4:
TABLE 4 removal rate of As, Cd and Pb in field soil by different eluents
| Arsenic removal Rate (%) | Cadmium removal Rate (%) | Lead removal (%) | |
| EDDS | 5.97％ | 25.00％ | 15.73％ |
| Malonic acid | 9.42％ | 31.53％ | 4.62％ |
| Compound eluting agent | 33.45％ | 63％ | 65.74％ |
Adding aluminum sulfide into the leachate according to the liquid-solid ratio of 15:1, stirring for 30min at 25 ℃, filtering and separating to obtain realgar, CdS precipitate, PbS precipitate and tail liquid, wherein the recovery rates of arsenic, cadmium and lead in the leachate are respectively 92%, 87% and 84%, and the obtained tail liquid is returned for reuse.
The inventors found that the contaminated soil treated with EDDS, malonic acid and a combination eluting agent exhibited morphological changes of arsenic, cadmium and lead as shown in FIGS. 4(a), (b) and (c), and it was found that arsenic in the obligatory adsorption state, the weakly crystalline hydrated iron-aluminum oxide bound state and the crystalline hydrated iron-aluminum oxide bound state was reduced by 20.12 mg/kg, respectively, after EDDS alone eluted, as compared with the original soil-1、32.75mg·kg-1And 10.82mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 156.77 mg/kg-1And a reduction of 8.56 mg/kg-1And an increase of 67.28mg kg-1The amount of lead in acid extractable, reducible and residual states was reduced by 1156 mg/kg-1、769.75mg·kg-1And 526.42mg kg-1After malonic acid is independently washed, the arsenic in an obligatory adsorption state, a combined state of iron-aluminum oxide hydrate with weak crystallization and a combined state of iron-aluminum oxide hydrate with crystallization is respectively reduced by 35.41 mg/kg-1、28.79mg·kg-1And 38.83mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 86.45 mg/kg-1、26.72mg·kg-1And 2.54mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 272.35 mg/kg-1、336.43mg·kg-1And 163.03mg kg-1After being mixed with EDDS and malonic acid and washed, the arsenic in an obligatory adsorption state, a weak-crystal bonded ferric aluminum oxide state and a crystal bonded ferric aluminum oxide state is respectively reduced by 53.56 mg/kg-1、208.63mg·kg-1And 177.39mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 196.63 mg/kg-1、38.96mg·kg-1And 74.25mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1756.72 mg/kg-1、5483.74mg·kg-1And 2457.32mg kg-1。
Example 5
The sample is taken from sandy soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 683.20 mg-kg-1、386.50mg·kg-1And 12547mg·kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172 mg/kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 15:1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing MGDA and acetic acid, and the concentration ratio of the MGDA to the acetic acid is 4: 9, the pH value of the compound eluting agent is 5, and the temperature is controlled at 30 ℃ and 250 r.min-1Is stirred for 60min and under the same conditions, a separate rinse is performed with MGDA (same as the amount of MGDA in the formulated rinse) and acetic acid (same as the amount of acetic acid in the formulated rinse) in the same amounts as the individual components in the formulated rinse. The leaching rates of the leaching agents on arsenic, cadmium and lead in the polluted soil are calculated and shown in the table 5:
TABLE 5 removal rate of As, Cd and Pb in field soil by different eluents
| Arsenic removal Rate (%) | Cadmium removal Rate (%) | Lead removal (%) | |
| MGDA | 3.94％ | 32.79％ | 7.58％ |
| Acetic acid | 8.77％ | 14.33％ | 7.82％ |
| Compound eluting agent | 36％ | 61.88％ | 66.53％ |
Adding calcium sulfide into the leachate at a liquid-solid ratio of 40:1, stirring at 30 deg.C for 60min, filtering and separating to obtain Realgar, CdS precipitate, PbS precipitate and tail liquid, wherein the recovery rates of arsenic, cadmium and lead in the leachate are 89%, 76% and 83%, respectively, and the obtained tail liquid is reused.
The inventors found that, when MGDA and acetic acid are used alone or in combination with a leaching agent to treat contaminated soil, the change of arsenic, cadmium and lead forms is shown in FIGS. 5(a), (b) and (c), and it is found that, when MGDA is used alone, arsenic in an obligatory adsorption state, a binding state of iron and aluminum oxide with weak crystallization, and a binding state of iron and aluminum oxide with crystallization is reduced by 18.73 mg/kg, respectively, as compared with the original soil-1、9.17mg·kg-1And 5.42mg kg-1The cadmium in acid extractable state, reducible state and residue state is respectively reduced by 32.58 mg.kg-1、7.65mg·kg-1And 75.15mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 792.62 mg/kg-1、129.65mg·kg-1And 35.43mg kg-1After acetic acid is independently washed, the arsenic in an obligatory adsorption state, a combined state of weak crystal hydrated iron-aluminum oxide and a combined state of crystal hydrated iron-aluminum oxide is respectively reduced by 7.79 mg/kg-1、30.56mg·kg-1And 23.16mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 27.79 mg/kg-1、10.63mg·kg-1And 32.52mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 636.15 mg/kg-1、235.63mg·kg-1And 168.72mg kg-1After the MGDA and acetic acid are combined and washed, the mixture is in an obligatory adsorption state, a weak crystal hydrated iron-aluminum oxide binding state and a crystal hydrated iron-aluminum oxide binding stateThe arsenic content of the iron-aluminum oxide combined state is reduced by 32.45 mg/kg-1、187.47mg·kg-1And 61.72mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 113.24 mg/kg-1、27.36mg·kg-1And 86.22mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1208.30 mg/kg-1、4922.80mg·kg-1And 3080.03mg kg-1。
Example 6
The sample is taken from soil near a certain lead-zinc smelting plant in Hunan province, is naturally air-dried, is screened and is uniformly mixed for later use. The content of arsenic, cadmium and lead in the soil sample is measured to be 974.80 mg-kg-1、410.50mg·kg-1And 14730mg kg-1Far exceeding the control value of soil pollution risk of building site of the second kind in the standard of soil environmental quality control Standard (trial) of soil pollution risk of building site of GB36600-2018 (arsenic 140 mg/kg)-1Cadmium 172 mg/kg-1And lead 2500 mg/kg-1。
According to the liquid-solid ratio of 20:1, adding a compound eluent into soil, wherein the compound eluent is formed by mixing IDSA and oxalic acid, and the concentration ratio of IDSA to oxalic acid is 3: 7, preparing the eluting agent with the pH value of 3 at the temperature of 25 ℃ at 200 r.min-1Is stirred for 75min and under the same conditions, the individual rinses are washed with the same amounts of IDSA (same amount of IDSA as the combined rinse, code I1), oxalic acid (same amount of oxalic acid as the combined rinse, code C1) as the individual components of the combined rinse, and with the same amounts of IDSA (same sum of IDSA and oxalic acid as the combined rinse, code I2), oxalic acid (same sum of IDSA and oxalic acid as the combined rinse, code C2) as the combined rinse. The leaching rates of the leaching agents on arsenic, cadmium and lead in the polluted soil are calculated and shown in the table 6:
TABLE 6 removal rate of As, Cd and Pb in field soil by different eluents
| Arsenic removal Rate (%) | Cadmium removal Rate (%) | Lead removal (%) | |
| IDSA(I1) | 7.56％ | 18.66％ | 8.75％ |
| Oxalic acid (C1) | 9.35％ | 23.63％ | 15.74％ |
| IDSA(I2) | 9.00％ | 33.68％ | 9.53％ |
| Oxalic acid (C2) | 7.17％ | 36.21％ | 17.88％ |
| Compound eluting agent | 39.88％ | 62.63％ | 62.97％ |
Adding barium sulfide into the leachate according to the liquid-solid ratio of 15:1, stirring for 45min at 30 ℃, filtering and separating to obtain realgar, CdS precipitate, PbS precipitate and tail liquid, wherein the recovery rates of arsenic, cadmium and lead in the leachate are respectively 86%, 82% and 79%, and the obtained tail liquid is returned for reuse.
The inventors found that arsenic, cadmium and lead were changed in the form after treating the contaminated soil with IDSA and oxalic acid alone or in combination with an eluting agent as shown in FIGS. 6(a), (b) and (c), and it was found that arsenic in the form of obligate adsorption, bound iron aluminum oxide with weak crystallinity and bound iron aluminum oxide with crystalline crystallinity was reduced by 23.57 mg/kg, respectively, in the form of bound iron aluminum oxide with weak crystallinity after eluting IDSA alone, as compared with the original soil-1、50.82mg·kg-1And 3.56mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 43.32 mg/kg-1And a reduction of 20.25 mg/kg-1And an increase of 2.55mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 844.74 mg/kg-1、136.53mg·kg-1And 289.72mg kg-1After oxalic acid is washed independently, arsenic in an obligatory adsorption state, a combined state of iron-aluminum oxide hydrate with weak crystallization and a combined state of iron-aluminum oxide hydrate with crystallization is reduced by 18.10 mg/kg-1、48.180mg·kg-1And 11.86mg kg-1The cadmium in acid extractable state, reducible state and residue state is respectively reduced by 38.17 mg.kg-1And a reduction of 28.64 mg/kg-1And an increase of 0.37 mg/kg-1The amount of acid-extractable, reducible and residual lead was reduced by 768.14 mg/kg-1、1997.55mg·kg-1And 156.34mg kg-1After the IDSA and the oxalic acid are combined for washing, the arsenic in an obligatory adsorption state, a weak-crystallization iron-aluminum oxide hydrate combination state and a crystallization iron-aluminum oxide hydrate combination state is respectively reduced by 50.57 mg/kg-1、268.74mg·kg-1And 156.16mg kg-1The acid extractable cadmium, the reducible cadmium and the residual cadmium are respectively reduced by 193.44 mg/kg-1、38.60mg·kg-1And 95.75mg kg-1The amount of acid-extractable, reducible and residual lead was reduced by 1959.61 mg/kg-1、5332.32mg·kg-1And 2568.17mg kg-1。
Claims (7)
1. A method for removing arsenic, cadmium and lead in field soil by using a combined eluent in a synergistic manner is characterized by comprising the following steps: the biodegradable chelating agent and the low-molecular organic acid are combined to obtain a combined eluent, and then the combined eluent is applied to site soil for ectopic treatment so as to remove arsenic, cadmium and lead in the site soil.
2. The method for removing arsenic, cadmium and lead from field soil by using a compound eluent as claimed in claim 1, wherein the compound eluent comprises the following steps: the concentration ratio of the biodegradable chelating agent to the low-molecular organic acid is 1: 5-2: 1, the pH value of the formulated eluent is 3-7.
3. The method for removing arsenic, cadmium and lead from field soil by using a combined eluent in a synergistic way as claimed in claim 1 or 2, wherein the method comprises the following steps: the biodegradable chelating agent is selected from one or more of EDDS, MGDA, GLDA, HIDS and IDSA.
4. The method for removing arsenic, cadmium and lead from field soil by using a combined eluent in a synergistic way as claimed in claim 1 or 2, wherein the method comprises the following steps: the low molecular organic acid is selected from one or more of formic acid, acetic acid, malonic acid, citric acid, ascorbic acid, oxalic acid, tartaric acid and fumaric acid.
5. The method for removing arsenic, cadmium and lead from field soil by using a combined eluent in a synergistic way as claimed in claim 1 or 2, wherein the method comprises the following steps: the liquid-solid ratio of the compound eluting agent to the field soil is 10-25: 1, the ectopic treatment is mixing and stirring at a speed of 100--1The time is 30-120min, and the temperature is 10-50 ℃.
6. The method for removing arsenic, cadmium and lead from field soil by using a combined eluent in a synergistic way as claimed in claim 1 or 2, wherein the method comprises the following steps: adding a vulcanizing agent into leachate obtained by separating mud and water after the ectopic treatment is finished, wherein the liquid-solid ratio of the leachate to the vulcanizing agent is 10-50:1, and stirring for 15-120min at the temperature of 10-50 ℃ for precipitating arsenic, cadmium and lead in the leachate.
7. The method for removing arsenic, cadmium and lead from field soil by using a compound eluent as claimed in claim 6, wherein the compound eluent comprises the following steps: the vulcanizing agent is selected from one or more of potassium sulfide, sodium sulfide, aluminum sulfide, barium sulfide and calcium sulfide.
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| CN102500612A (en) * | 2011-10-28 | 2012-06-20 | 中南大学 | Chemical leaching restoring method for soil polluted by heavy metals |
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| CN101362146A (en) * | 2008-09-12 | 2009-02-11 | 中山大学 | Chemical leaching repairing method for removing heavy metal and arsenic from soil |
| CN102500612A (en) * | 2011-10-28 | 2012-06-20 | 中南大学 | Chemical leaching restoring method for soil polluted by heavy metals |
| CN103084384A (en) * | 2013-01-08 | 2013-05-08 | 四川农业大学 | Application of oxalic acid in removal of soil cadmium pollution |
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