CN103521515B - Method for restoring heavy metal contaminated soil through double-liquid-phase extraction - Google Patents
Method for restoring heavy metal contaminated soil through double-liquid-phase extraction Download PDFInfo
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- CN103521515B CN103521515B CN201310537438.9A CN201310537438A CN103521515B CN 103521515 B CN103521515 B CN 103521515B CN 201310537438 A CN201310537438 A CN 201310537438A CN 103521515 B CN103521515 B CN 103521515B
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Abstract
The invention discloses a method for restoring heavy metal contaminated soil through double-liquid-phase extraction. The restoring system of the method has two liquid phases, one liquid phase is a water phase formed by dissolving leaching agents in water, and the other liquid phase is an organic phase formed by dissolving acidic extractant in organic solvents. The method mainly comprises five basic steps that (1) the heavy metal contaminated soil is infiltrated; (2) heavy metal is separated through the double-liquid-phase extraction; (3) the heavy metal is recycled through reextraction; (4) the ammonia of the P204 organic phase is saponified; (5) the soil is washed. Citric acid and ammonium sulfate are used as the leaching agents, P204 is used as the extractant, and the removal rate of biological effective-state lead and biological effective-state cadmium can reach more than 90%. The method has the advantages of being high in restoring speed, high in restoring efficiency, high in use ratio of the leaching agents, high in restoring work efficiency and high in greenization degree, simultaneously recycling the heavy metal, being low in restoring cost and the like.
Description
Technical field
The present invention relates to the method for double liquid phase extraction restoration of soil polluted by heavy metal, particularly relate to the method for the collaborative restoration of soil polluted by heavy metal of leaching agent and extractant.
Background technology
Along with economic development, the particularly quickening of industrialization and urbanization process, heavy metal element constantly enters soil with sewage, atmospheric sedimentation, solid waste, material used for agriculture, causes heavy metal pollution of soil day by day serious.At present, the cultivated area of China's heavy metal pollution is about 1.5 hundred million mu; Nearly 1,200 ten thousand t of the annual contaminated by heavy metals grain in the whole nation, grain drop in production more than 1,000 ten thousand t that cause because of heavy metal pollution every year, economic loss adds up to and exceedes 30,000,000,000 yuan.
The restorative procedure of heavy-metal contaminated soil has numerous species.According to the difference of principle, heavy-metal contaminated soil reparation can be divided into physical restoration, chemical restoration and biological restoration.Although these restorative procedures respectively have advantage, also there are the various shortcomings that not yet overcome.For example, microorganism repairing method has shortcoming to be overcome below existing: remediation efficiency is low, and a kind of microorganism can only be worked to specific heavy metal element, and the enrichment finite capacity of microorganism to heavy metal element; Repairing effect is unstable, is subject to the impact of various environmental factors larger, microorganism exist genetic stability poor, easily morph, and must launch struggle for existence with indigenous microorganism group, finally likely objective microbe is eliminated because of competition failure; Heavy metal element reclaims difficult, and microorganism individuality is small, is difficult to separate from soil; Reparation speed is slow, although faster than phytoremediation, be much slower than chemical method.Generally speaking, the reparation of heavy-metal contaminated soil remains one of hot issue that current scientific and technological circle show great attention to.
Extraction (having another name called leaching method) is one of important chemical restoration, has the speed of reparation and remediation efficiency compared with advantages of higher.Extraction, taking acid, alkali, salt, complexing agent, surfactant etc. as leaching agent (extractant), makes soil repaired by the heavy metal in extract and separate soil.At present, the shortcoming of extraction has: inefficiency, because heavy metal is present in leachate, needs to implement to filter and repeatedly wash and just can make soil and heavy metal separate; The service efficiency of leaching agent is low, has no at present the process that leaching agent recycles, and therefore has the pollution of leaching agent to environment; Heavy metal element can not directly reclaim, and must separately set up technique, flow process complexity; Cost is high.Wherein, leaching agent can not recycle that can not directly to reclaim with heavy metal be to cause extraction to fail to move towards the main cause of practical application.
Summary of the invention
The object of the invention is to overcome the shortcoming of extraction restoration of soil polluted by heavy metal, give full play to the advantage of extraction, provide a kind of fast, the new method of efficient, greenization restoration of soil polluted by heavy metal.
The present invention is taking water-soluble citric acid and ammonium sulfate mixture as leaching agent, taking water-fast two (2 – ethylhexyl) phosphoric acid (being P204) as extractant.Citric acid and ammonium sulfate water-soluble and form water; Acidic extractant P204 is dissolved in sulfonated kerosene and forms organic phase, thereby sets up the method for double liquid phase extraction restoration of soil polluted by heavy metal.The effect of leaching agent is the biologically effective state heavy metal in leaching soil, makes heavy metal move up into water from soil transfer.Acidic extractant P204 has multiple effect, and the first extracts the heavy metal that enters water into organic phase.It two is to move by balance the speed of accelerating ammonium sulfate leaching heavy metal.It three is synergies of extractant P204 and leaching agent and improve the leaching rate of heavy metal.Acidic extractant P204 organic phase is in use with the suitable saponification of ammoniacal liquor, and object is to improve the extraction yield of heavy metal.It four is directly to extract some heavy metals in biologically effective state, such as the hydroxide of heavy metal, carbonate, acylate etc.Biologically effective state comprises weak acid solubilised state, reducible state and oxidable state.In the various forms of heavy metal, weak acid solubilised state is the most easily absorbed by plants, to people's potential threat maximum.Therefore, the soil key of repairing heavy metal pollution is the biologically effective state heavy metal of removing in soil, especially will remove the weak acid solubilised state heavy metal in soil.
The method of double liquid phase extraction restoration of soil polluted by heavy metal of the present invention specifically realizes by following process program.
Double liquid phase extraction reparation system of the present invention has two liquid phases, and one of them liquid phase is the water-soluble and water that forms of leaching agent, and another liquid phase is that acidic extractant is dissolved in organic solvent and the organic phase that forms; Leaching agent is the mixture of citric acid and ammonium sulfate, and acidic extractant is P204.
(1) infiltration of heavy-metal contaminated soil
Under field conditions (factors) that heavy-metal contaminated soil is air-dry, clap broken rear mistake 2 mm and sieve to remove foreign material; Citric acid taking mass percentage concentration as 0.1% and 0.1% ammonium sulfate solution are as leaching liquid, the mass ratio of controlling dry heavy-metal contaminated soil and leaching liquid is 1:5, under room temperature, the soil of heavy metal pollution and leaching liquid are fully uniformly mixed to 15 min, obtain the mixture of leaching liquid and soil;
(2) double liquid phase extraction separating beavy metal
The mass ratio of controlling dry heavy-metal contaminated soil and saponification P204 organic phase is 2:1, adds the P204 sulfonated kerosene organic phase that ammonia saponification rate is 50%, mass concentration is 15% in the mixture of leaching liquid and soil, is fully uniformly mixed 120 min under room temperature; After stratification, the acidic extractant organic phase that upper strata is loaded with heavy metals, reclaims heavy metal operation for stripping; Middle level is that the water that contains leaching agent ammonium sulfate is leaching liquid, is cycled to used in the infiltration operation of heavy-metal contaminated soil; Lower floor is wet soil earth to be washed, for soil washing procedure;
P204 organic phase is the sulfonated kerosene of P204, and wherein the concentration of P204 is 15%;
(3) strip and reclaim heavy metal
In the P204 of loaded with heavy metals organic phase, adding concentration is the sulfuric acid of 2 mol/L, controls to compare to be about O/A=10:1, is fully uniformly mixed 5 min under room temperature; After stratification, upper strata is the P204 organic phase of having regenerated, for ammonia saponification; Lower floor is the water that contains heavy metal, by the heavy metal ion in ammonium bicarbonate precipitation water, filters, be precipitated as the mixture of heavy metal, filtrate, after sulfuric acid acidation is removed excessive precipitating reagent carbonic hydroammonium and regulated pH to be about 6.5 with ammonia neutralization, becomes ammonium sulfate, for preparing leaching liquid;
(4) the ammonia saponification of P204 organic phase
Controlling ammonia saponification rate is 50%, and in the acidic extractant organic phase after reextraction heavy metal, adding concentration is the ammoniacal liquor of 5 mol/L, is fully uniformly mixed 10 min under room temperature; After stratification, upper strata is saponification P204 organic phase, for double liquid phase extraction separating beavy metal operation; Lower floor is water;
(5) soil washing
Be 1:1 according to the mass ratio of dry ground earth and water, in the soil to be washed obtaining, add water after the layering of double liquid phase extraction separating beavy metal operation, under room temperature, fully stir 10 min; After stratification, upper strata is the water that contains a small amount of leaching agent, can be used for the infiltration of heavy-metal contaminated soil; Lower floor is the soil of repairing.
The present invention has the following advantages: 1) reparation speed is fast, and extractant P204 extracts heavy metal element into organic phase, thereby significantly accelerates the speed of leaching agent leaching heavy metal.The time of double liquid phase extraction is 120 min, and the total length of time that has been dosed into its reparation from soil is about 3 hours.2) remediation efficiency is high, and acidic extractant P204 can directly extract the heavy metal element in hydroxide, carbonate, and because the synergy of P204 and leaching agent can improve the leaching rate of biologically effective state heavy metal.The clearance of biologically effective state heavy metal of the present invention can reach more than 90%
.3) utilization rate of leaching agent is high, by recycling of leaching liquid, has not only improved the utilization rate of leaching agent, and the discharge capacity of leaching agent is significantly reduced, and has eliminated the adverse effect of leaching agent to environment.4) operating efficiency of repairing is high, and extractant P204 extracts heavy metal element into organic phase, has avoided the filtration of soil; In order to improve the utilization rate of leaching agent, only need soil to carry out 1 washing.5) green degree is high, and agents useful for same is nontoxic green reagent, and has realized recycling of extractant P204, leaching agent citric acid and ammonium sulfate, and whole repair process is close to " zero pollutes ".6) in rehabilitating soil, realized the recovery of heavy metal.Only need strip and be carried on the heavy metal in P204 organic phase with sulfuric acid, then use the heavy metal in ammonium bicarbonate precipitation solution, filtration can obtain recovery heavy metal, simple process.And it is, after ammonia neutralization adjust pH is 6～7, to can be used for preparing leaching liquid that filtrate is removed excessive precipitating reagent through sulfuric acid acidation.7) rehabilitation cost is low, and the price of chemical reagent used is lower, and has set up utilization process; Improve operating efficiency, also reduced rehabilitation cost.
Brief description of the drawings
Fig. 1 is the method schematic diagram of double liquid phase extraction restoration of soil polluted by heavy metal;
Extractant P204, leaching agent citric acid and ammonium sulfate all can recycle; Filtrate when water, the precipitation of heavy metals of washing soil all can be used for preparing cleaning solution.
Detailed description of the invention
Below in conjunction with specific embodiment, the method for double liquid phase extraction restoration of soil polluted by heavy metal of the present invention is further described.
embodiment 1:
(1) infiltration of heavy-metal contaminated soil
Under field conditions (factors) that heavy-metal contaminated soil is air-dry, clap gently broken rear mistake 2 mm and sieve to remove foreign material.In extractor, to add dry weight be 100 kilograms, the heavy-metal contaminated soil of the impurity elimination of sieving, adding 500 kilogram-mass percentage concentrations is the aqueous solution of 0.1% citric acid and 0.1% ammonium sulfate, under room temperature, the soil of heavy metal pollution and leaching liquid (i.e. 0.1% citric acid and 0.1% ammonium sulfate solution) are fully uniformly mixed to 15 min, obtain the mixture of leaching liquid and soil.
(2) double liquid phase extraction separating beavy metal
Filling in the extractor of 600 kilograms " mixtures of leaching liquid and soil ", add the P204 sulfonated kerosene organic phase that 50 kilograms of ammonia saponification rates are 50%, concentration is 15%, under room temperature, be fully uniformly mixed 120 min; After stratification, the acidic extractant organic phase that upper strata is loaded with heavy metals, reclaims heavy metal operation for stripping; Middle level is that the water that contains leaching agent ammonium sulfate is leaching liquid, is cycled to used in the infiltration operation of heavy-metal contaminated soil; Lower floor is wet soil earth to be washed.
(3) strip and reclaim heavy metal
In the extractor of P204 organic phase that fills 50 kg load heavy metals, adding 5 L concentration is the sulfuric acid of 2 mol/L, is fully uniformly mixed 5 min under room temperature; After stratification, upper strata is the P204 organic phase of having regenerated, for ammonia saponifying process; Lower floor is the water that contains heavy metal, by the heavy metal ion in ammonium bicarbonate precipitation water, filters, be precipitated as the mixture of heavy metal, filtrate, after sulfuric acid acidation is removed excessive precipitating reagent carbonic hydroammonium and regulated pH to be about 6.5 with ammonia neutralization, becomes ammonium sulfate, for preparing leaching liquid.
(4) the ammonia saponification of P204 organic phase
In the extractor of P204 organic phase that fills 50 kilograms of regeneration, adding 2 L concentration is the ammoniacal liquor of 5 mol/L, is fully uniformly mixed 10 min under room temperature; After stratification, upper strata is that ammonia saponification rate is 50% saponification P204 organic phase, for double liquid phase extraction separating beavy metal operation; Lower floor is water.
(5) soil cleans
Be 100 kilograms of wet soil earth to be washed filling dry weight, add double centner water, under room temperature, fully stir 10 min; After stratification, upper strata is the water that contains a small amount of leaching agent, for the infiltration operation of heavy-metal contaminated soil; Lower floor is the soil of repairing.
(6) repairing effect
Before reparation, the total content of Lead In Soil is 304 mg/kg, and wherein the lead of biologically effective state is 274 mg/kg, and the lead of residual form (biological invalid state) is 30.3 mg/kg.After adopting method of the present invention to repair, the total content of Lead In Soil is reduced to 34.2 mg/kg, and lower than country, about Limited Doses plumbous in soil quality standard, plumbous clearance (extraction yield) is 88.8%; The lead of biologically effective state reduces most 5.3 mg/kg, and the clearance (extraction yield) of biologically effective state is 98.1%.Biologically effective state is weak acid solubilised state, reducible state and oxidable state sum.Total content is biologically effective state and residual form sum.
Before reparation, the total content of Cadmium in Soil is 2.71 mg/kg, and wherein the cadmium of biologically effective state is 2.67 mg/kg, and the cadmium of residual form (biological invalid state) is 0.038 mg/kg.After adopting method of the present invention to repair, the total content of Cadmium in Soil is reduced to 0.15 mg/kg, the cadmium Limited Doses lower than country about soil quality standard, and the clearance (extraction yield) of cadmium is 94.5%; The cadmium of biologically effective state reduces most 0.11 mg/kg, and the clearance (extraction yield) of biologically effective state cadmium is 95.9%.
Claims (1)
1. the method for a double liquid phase extraction restoration of soil polluted by heavy metal, it is characterized in that: reparation system has two liquid phases, one of them liquid phase is the water-soluble and water that forms of leaching agent, and another liquid phase is that acidic extractant is dissolved in organic solvent and the organic phase that forms; Leaching agent is the mixture of citric acid and ammonium sulfate, and acidic extractant is P204; Specifically realize by following process program: the infiltration of (1) heavy-metal contaminated soil
Under field conditions (factors) that heavy-metal contaminated soil is air-dry, clap the broken rear 2mm of mistake and sieve to remove foreign material; Citric acid taking mass percentage concentration as 0.1% and 0.1% ammonium sulfate solution are as leaching liquid, the mass ratio of controlling dry heavy-metal contaminated soil and leaching liquid is 1:5, under room temperature, the soil of heavy metal pollution and leaching liquid are fully uniformly mixed to 15min, obtain the mixture of leaching liquid and soil;
(2) double liquid phase extraction separating beavy metal
The mass ratio of controlling dry heavy-metal contaminated soil and saponification P204 organic phase is 2:1, adds the P204 sulfonated kerosene organic phase that ammonia saponification rate is 50%, mass concentration is 15% in the mixture of leaching liquid and soil, is fully uniformly mixed 120min under room temperature; After stratification, the acidic extractant organic phase that upper strata is loaded with heavy metals, reclaims heavy metal operation for stripping; Middle level is that the water that contains leaching agent ammonium sulfate is leaching liquid, is cycled to used in the infiltration operation of heavy-metal contaminated soil; Lower floor is wet soil earth to be washed, for soil washing procedure;
P204 organic phase is the sulfonated kerosene of P204, and wherein the concentration of P204 is 15%;
(3) strip and reclaim heavy metal
In the P204 of loaded with heavy metals organic phase, adding concentration is the sulfuric acid of 2mol/L, controls and is in a ratio of O/A=10:1, is fully uniformly mixed 5min under room temperature; After stratification, upper strata is the P204 organic phase of having regenerated, for ammonia saponifying process; Lower floor is the water that contains heavy metal, by the heavy metal ion in ammonium bicarbonate precipitation water, filters, be precipitated as the mixture of heavy metal, filtrate, after sulfuric acid acidation is removed excessive precipitating reagent carbonic hydroammonium and regulated pH to be 6.5 with ammonia neutralization, becomes ammonium sulfate, for preparing leaching liquid;
(4) the ammonia saponification of P204 organic phase
Controlling ammonia saponification rate is 50%, and in the acidic extractant organic phase after reextraction heavy metal, adding concentration is the ammoniacal liquor of 5mol/L, is fully uniformly mixed 10min under room temperature; After stratification, upper strata is saponification P204 organic phase, for double liquid phase extraction separating beavy metal operation; Lower floor is water;
(5) soil washing
Be 1:1 according to the mass ratio of dry ground earth and water, in the soil to be washed obtaining, add water after the layering of double liquid phase extraction separating beavy metal operation, under room temperature, fully stir 10min; After stratification, upper strata is the water that contains a small amount of leaching agent, can be used for the infiltration of heavy-metal contaminated soil; Lower floor is the soil of repairing.
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| CN105602568B (en) * | 2015-12-22 | 2018-12-25 | 陕西理工学院 | A kind of heavy metal pollution place slip casting renovation agent and preparation method thereof |
| CN108746186A (en) * | 2018-05-21 | 2018-11-06 | 天津理工大学 | A kind of bionics prosthesis method of heavy-metal contaminated soil |
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| JP4550731B2 (en) * | 2005-12-16 | 2010-09-22 | 興和株式会社 | Purification method of cadmium contaminated soil |
| CN1872377B (en) * | 2006-01-04 | 2010-08-18 | 有研稀土新材料股份有限公司 | Method for saponifying extraction agent |
| CN100529123C (en) * | 2007-12-13 | 2009-08-19 | 东北大学 | Method of acidic extractant complexing extraction separation rare-earth element |
| CN100577830C (en) * | 2008-07-11 | 2010-01-06 | 广州有色金属研究院 | Process for recovering rare earth element in waste florescent lamps |
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