CN111087063A

CN111087063A - Medicament formula for degrading organic pollutants based on strengthening ferrous deposit activated molecular oxygen in aquifer and use method thereof

Info

Publication number: CN111087063A
Application number: CN201911299707.6A
Authority: CN
Inventors: 袁松虎; 谢雯静
Original assignee: China University of Geosciences
Current assignee: China University of Geosciences
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2020-05-01
Anticipated expiration: 2039-12-17
Also published as: CN111087063B

Abstract

The invention discloses a medicament formula for degrading organic pollutants based on strengthening ferrous deposit activated molecular oxygen in an aquifer and a using method thereof. The formulation of the medicament consists of inorganic ligand and organic ligand; the organic ligand at least comprises two carboxyl groups, the organic ligand has strong complexing ability with ferrous iron and ferric iron, and the complex formed by the organic ligand with the ferrous iron and the ferric iron has poor adsorbability on the sediment; the inorganic ligand is a phosphorus ligand, the complexing ability of the inorganic ligand with ferrous iron and ferric iron is strong, and the complex formed by the inorganic ligand with ferrous iron and ferric iron has strong adsorbability on sediments. The method utilizes the organic ligand and the inorganic ligand to cooperatively regulate the ferrous form of solid-liquid two phases in the aquifer and the electron transfer between the solid-liquid two phases, maximizes the yield and the yield of hydroxyl radicals, reduces the total dosage of the ligand, improves the degradation efficiency of organic pollutants, has the advantages of low cost, environmental friendliness and the like, and has great economic and social benefits in the fields of polluted sites and groundwater remediation.

Description

Medicament formula for degrading organic pollutants based on strengthening ferrous deposit activated molecular oxygen in aquifer and use method thereof

Technical Field

The invention relates to the technical field of underground water organic pollutant treatment, in particular to a medicament formula for degrading organic pollutants based on strengthening ferrous iron sediment activation molecular oxygen in an aquifer and a use method thereof.

Background

Groundwater is one of the most important fresh water resources on earth. However, along with the rapid development of economy, a large amount of groundwater and water resources are polluted, and 195 urban monitoring results in the whole country show that 97% of urban groundwater is polluted to different degrees, wherein 40% of urban groundwater pollution has a trend of increasing year by year.

Among various pollutions, the organic pollution of the underground water directly influences the human health, and the development of the remediation technology of the organic pollution of the underground water has great significance. The remediation technology for organic pollution caused by groundwater pollution mainly comprises in-situ remediation, ex-situ remediation, a natural attenuation monitoring technology and the like. The groundwater in-situ remediation technology is a technology for remedying the polluted groundwater in situ under the action of human intervention, and plays an important role in the groundwater remediation field by the advantages of low remediation cost, less human exposure, relatively short remediation time and the like. Among in-situ remediation technologies, the in-situ chemical oxidation method is considered to be one of the most effective methods for removing volatile organic pollutants in saturated soil and underground water due to the characteristics of realization of in-situ, high treatment speed, complete pollutant degradation and the like.

The existing in-situ chemical oxidation technology for the polluted site is mainly based on the generation of strong-oxidizing free radicals by oxidants such as activated hydrogen peroxide, persulfate and the like to oxidize and degrade pollutants. However, the hydrogen peroxide transportation, storage and other processes have great safety risks; hydrogen peroxide, persulfate and the like are too high in reactivity, and are decomposed quickly after being injected into an aquifer and are difficult to transmit for a long distance. Compared with hydrogen peroxide and persulfate, the oxidation technology based on molecular oxygen is a more environment-friendly and economic repair method. At present, an in-situ chemical oxidation repair method based on molecular oxygen is not considered, mainly because the oxidation capability of the molecular oxygen is weak, the efficiency of activating the molecular oxygen by reducing substances such as ferrous iron in an aqueous medium to generate hydroxyl radicals is low, and the degradation effect of pollutants caused by the low efficiency is not ideal.

Disclosure of Invention

The invention aims to provide a medicament formula for degrading organic pollutants based on activated molecular oxygen of ferrous iron sediments in an enhanced aquifer, which has high efficiency, low cost and environmental friendliness in treating the organic pollutants and a using method thereof aiming at the existing defects.

The purpose of the invention can be realized by the following technical scheme:

a formulation of an agent for degrading organic pollutants based on the enhanced ferrous deposit activated molecular oxygen in an aquifer, the agent comprising an inorganic ligand and an organic ligand; the organic ligand at least comprises two carboxyl groups, has strong complexing ability with ferrous iron and ferric iron, and has poor adsorbability of a complex formed by the organic ligand with the ferrous iron and the ferric iron on a deposit; the inorganic ligand is a phosphorus ligand, the complexing ability of the inorganic ligand with ferrous iron and ferric iron is strong, and the adsorbability of a complex formed by the inorganic ligand with ferrous iron and ferric iron on sediment is strong.

Preferably, the mass ratio of the organic ligand to the inorganic ligand is 1: 1 to 9.

Preferably, the mass ratio of the organic ligand to the inorganic ligand is 1: 3.

preferably, the organic ligand is one or more of sodium Ethylenediaminetetraacetate (EDTA), nitrilotriacetic acid (NTA), N' -ethylenediamine disuccinic acid (EDDS), ethylene glycol bis (2-aminoethyl ether) tetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DPTA), and citric acid.

Preferably, the inorganic ligand is one or more of tripolyphosphate, tetrapolyphosphate, hexapolyphosphate, polyphosphate, phosphate and pyrophosphate.

Preferably, the organic ligand is ethylenediaminetetraacetic acid (EDTA) and the inorganic ligand is triphenyl phosphate (TPP).

The use method of the medicament formula for degrading the organic pollutants based on the activated molecular oxygen of the ferrous deposits in the strengthened aquifer injects the medicament into the aquifer of the polluted site, the aquifer comprises the ferrous deposits, and oxygen is supplied to the aquifer to degrade the organic pollutants in the aquifer of the polluted site, and the method specifically comprises the following steps:

s1, setting a single-well, double-well or multi-well circulating well repairing mode according to the hydrogeological structure condition of a water-bearing stratum of a polluted site, and drilling a well;

s2, mixing the medicament with water to form a solution;

s3, providing oxygen into the well to dissolve molecular oxygen with certain concentration in the aquifer;

s4, conveying the solution formed in the step S2 to an aquifer through the hydraulic driving action of the circulating well. Divalent iron in the sediment of the aqueous layer and the organic ligand form a divalent iron organic ligand complex, the divalent iron organic ligand complex is desorbed from the sediment and transferred to a liquid phase, meanwhile, the inorganic ligand is complexed with divalent iron in the sediment to form a divalent iron inorganic ligand complex which is adsorbed on the surface of the sediment in the aqueous layer, the divalent iron organic ligand complex transferred to the liquid phase is oxidized by molecular oxygen to form a trivalent iron organic ligand complex, the divalent iron inorganic ligand complex adsorbed on the surface of the sediment transfers electrons to a trivalent iron organic ligand complex in the liquid phase, the trivalent iron organic ligand complex is reduced into the divalent iron organic ligand complex, the whole process maintains a certain concentration of divalent iron in the liquid phase, and the divalent iron is used for activating molecular oxygen to generate hydroxyl radicals so as to remove organic pollutants in the aqueous layer;

and S5, monitoring the concentrations of the organic pollutants and the organic ligands in the aquifer in the circulating well, adding a small amount of organic ligands again until the concentration of the organic pollutants in the water body meets the treatment requirement in the degradation process of the organic pollutants, wherein the concentration of the organic ligands is lower than a preset value.

Preferably, in step S4, the total concentration of the pharmaceutical agent in the aqueous layer forming a dissolved state is 0.1 to 2 mmol/L.

Preferably, the total concentration of the pharmaceutical agent in the aqueous layer to form a dissolved state is 1 mmol/L.

According to the medicament formula for degrading the organic pollutants based on the strengthening of the divalent iron sediment activated molecular oxygen in the aquifer, the divalent iron form in the solid-liquid two phases of the aquifer and the electron transfer process between the solid-liquid two phases are regulated and controlled through the synergistic effect of the organic ligand and the inorganic ligand, so that the efficiency of activating the molecular oxygen by the aquifer components to generate hydroxyl radicals and the degradation effect on the organic pollutants are improved; firstly, the yield of hydroxyl radical generated by activating molecular oxygen is improved by regulating and controlling the forms of water-phase ferrous iron directly acting with the molecular oxygen and part of ferrous iron desorbed from sediments by complexing ferrous iron with organic ligands; and the second is to reduce the ferric iron in the liquid phase by the electron transfer effect of the ferrous iron inorganic ligand complex adsorbed on the sediment, so as to improve the concentration of the ferrous iron in the liquid phase, thereby improving the total amount of hydroxyl radicals generated by activating molecular oxygen. The invention relates to two types of ligands, wherein an organic ligand is used for improving the efficiency of generating hydroxyl radicals by activating molecular oxygen with ferrous in an aqueous phase, an inorganic ligand is adsorbed on the surface of a sediment to promote a solid phase medium to transfer electrons to the liquid phase so as to promote iron circulation and improve the yield of the hydroxyl radicals, and the yield of the hydroxyl radicals are maximized through the synergistic effect of the two types of ligands, and meanwhile, the total dosage of the ligands can be reduced, and the high-efficiency degradation of pollutants is realized.

Compared with the prior art, the use method of the medicament formula for degrading the organic pollutants based on the activation of molecular oxygen by ferrous iron sediments in the strengthened aquifer has the following beneficial effects:

(1) the activated oxidant is molecular oxygen, and the molecular oxygen is more green, environment-friendly and easily available and has low cost;

(2) because ferrous deposits are widespread in the subsurface environment, the method is less costly to operate and less disturbing to the environment;

(3) utilizing the synergistic effect of the organic ligand and the inorganic ligand, the inorganic ligand and ferrous iron are complexed and adsorbed on the sediment, the ferrous iron on the sediment is complexed with the organic ligand and migrates to a liquid phase, and the ferrous iron is oxidized and converted into complex ferric iron in the process of activating molecular oxygen to generate hydroxyl free radical with strong oxidizing property; transferring electrons to the complexing ferric iron in the liquid phase by the ferrous inorganic ligand complex adsorbed on the sediment, reducing the complexing ferric iron in the liquid phase into complexing ferrous iron, transferring the electrons to the liquid phase by the structural state Fe (II) on the sediment, reducing the ferric iron in the liquid phase into ferrous iron, continuously circulating the low-concentration complexing ferrous iron formed by the synergistic action of the inorganic ligand and the organic ligand to efficiently activate molecular oxygen to generate hydroxyl radical oxidation pollutants, and removing the pollutants;

(4) the ferrous iron in the sediment in the water-containing layer is rarely released into water, and the ferric iron released into the solution can be complexed by the inorganic ligand again along with the consumption of the organic ligand, is adsorbed on the surface of the sediment and can be recycled;

(5) by utilizing the synergistic effect of the organic ligand and the inorganic ligand, compared with a single organic ligand or inorganic ligand, the concentration of the added medicament is lower, and the effect of treating organic pollutants is better;

(6) the concentrations of the organic ligand and the inorganic ligand in the added medicament are low, the organic ligand in the liquid phase can be degraded in the degradation process of organic pollutants, and the inorganic ligand can be adsorbed on the surface of sediments and slightly disturbs the water environment.

Drawings

FIG. 1 is a graph showing the effect of an agent of EDTA and TPP complex ligand in promoting the activation of dioxygen by ferrous deposits to generate hydroxyl radicals in an example of the present invention;

FIG. 2 is a graph showing the effect of EDTA and TPP complexing ligand agents in promoting the degradation of trichloroethylene by molecular oxygen in ferrous deposits according to an embodiment of the present invention;

FIG. 3 is a graph showing the change of the concentration of EDTA in the solution during the degradation of trichloroethylene with time according to an embodiment of the present invention;

FIG. 4 is a graph showing the time course of the TPP concentration in the solution during the degradation of trichloroethylene in the example of the present invention;

fig. 5 is a schematic diagram of the agent of organic and inorganic ligands promoting ferrous deposits to activate molecular oxygen to generate hydroxyl radicals to degrade organic pollutants in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings.

s2, mixing the medicament with water to form a solution so as to fully dissolve the solid medicament and facilitate the addition of subsequent medicaments;

s3, providing oxygen into the well, wherein the oxygen can be provided in a mode of aeration, water electrolysis or peroxide addition, so that molecular oxygen with a certain concentration is dissolved in the aquifer;

s4, conveying the solution formed in the step S2 to an aqueous layer through the hydraulic driving action of a circulating well, so that the total concentration of the medicament in a dissolved state in the aqueous layer is 0.1-2mmol/L, ferrous iron in the sediment of the aqueous layer forms a ferrous iron organic ligand complex with an organic ligand, the ferrous iron organic ligand complex is desorbed from the sediment and transferred to a liquid phase, and simultaneously an inorganic ligand is complexed with ferrous iron in the sediment, the ferrous iron inorganic ligand complex is adsorbed on the surface of the sediment in the aqueous layer, the ferrous iron organic ligand complex transferred to the liquid phase is oxidized by molecular oxygen to form a ferric iron organic ligand complex, the ferrous iron inorganic ligand complex adsorbed on the surface of the sediment transfers electrons to the ferric iron organic ligand complex in the liquid phase, and the ferric iron organic ligand complex is reduced into the ferrous iron organic ligand complex, the liquid phase is maintained to contain a certain concentration of ferrous iron in the whole process, and the ferrous iron is used for activating molecular oxygen to generate hydroxyl radicals so as to remove organic pollutants in the aquifer;

Examples

Trichloroethylene is a widely occurring chlorinated organic contaminant in ground water. Because of high toxicity and great harm to human and biological health safety, a medicament and a method for efficiently treating trichloroethylene wastewater must be found. In order to investigate the degradation effect of the divalent iron sediment activated molecular oxygen on organic pollutants by the inorganic ligand and the inorganic ligand in the medicament, a case test is carried out by taking trichloroethylene as a target pollutant.

Directly collecting field actual clay deposit containing iron (iron content is 5.2%) but low in organic matter content (1.5%), performing anaerobic drying in a glove box, mashing until the average particle size is less than 0.25cm, and collecting ferrous deposit for later use.

The degradation test is carried out in a 120mL anaerobic glass bottle, 4g ferrous sediment is added, 2mg/L trichloroethylene is added, 80mL aerobic water containing 1mmol/L medicament is added, the pH of the reaction system is 7.0 +/-0.1, the concentration of EDTA is 0.25mmmol/L, the concentration of TPP is 0.75mmol/L, the glass bottle is sealed and is placed in a shaking table at 220rpm and 25 ℃, the reaction is finished after 6 hours, and the hydroxyl radical test is carried out by adding 20mmol/L sodium benzoate as a trapping agent of hydroxyl radicals.

The procedure in the degradation test was the same as above except that the initial EDTA concentration added to the reaction system was 0.5mmol/L and the TPP concentration was 0.5 mmol/L.

The procedure in the degradation test was the same as above except that the initial EDTA concentration added to the reaction system was 0.75mmol/L and the TPP concentration was 0.25 mmol/L.

As shown in FIG. 1, in order to study the efficiency of generating hydroxyl radicals by the synergistic effect of the organic ligand and the inorganic ligand, a control experiment was performed by adding 1mmol/L EDTA alone and 1mmol/L TPP alone, and a blank control experiment was performed without adding any agent, and the other operation steps were the same as above. 20mmol/L sodium benzoate is added into the reaction system as a hydroxyl radical trapping agent, and as can be seen from figure 1, the efficiency of promoting the divalent iron sediment to activate molecular oxygen and generate hydroxyl radicals by using the agent with the total concentration of 1mmol/L composite ligand consisting of EDTA and TPP is higher than that of singly adding 1mmol/L EDTA or TPP or not adding any ligand. The effect of activating molecular oxygen to generate hydroxyl radicals by ferrous deposits is very slight when no ligand is added, and the single organic ligand EDTA or the single inorganic ligand TPP improves the efficiency of activating molecular oxygen to generate hydroxyl radicals by ferrous deposits, but the effect is not obvious; the composite ligand consisting of the organic ligand EDTA and the inorganic ligand TPP maximizes the efficiency of the ferrous deposit activating molecular oxygen to generate hydroxyl radicals, and the efficiency of the composite ligand agents with different proportions activating molecular oxygen to generate hydroxyl radicals is relatively close.

As shown in FIG. 2, in order to study the effect of the synergistic effect of the organic ligand EDTA and the inorganic ligand TPP on the removal of organic pollutants, a control experiment was performed by adding 1mmol/L EDTA alone and 1mmol/L TPP alone, and a blank control experiment was performed without adding any medicament, and the other operation steps were the same as above. From fig. 2, it can be seen that 1mmol/L of the agent with a total concentration of 1mmol/L of EDTA and TPP (EDTA: TPP ═ 1: 3) achieves a removal rate of 70% of trichloroethylene at 2mg/L in 360 minutes, and the removal rate of trichloroethylene is the highest, and from fig. 2, it can be seen that the efficiency of the composite ligand consisting of organic ligand EDTA and inorganic ligand TPP for promoting the divalent iron sediment to activate molecular oxygen to remove organic pollutants increases with the increase of the mass ratio of TPP.

As shown in FIG. 3, in order to study the degradation of EDTA by the composite ligand composed of organic ligand and inorganic ligand, meanwhile, the comparison tests of separately adding 0.75mmol/L EDTA, separately adding 0.5mmol/L EDTA and separately adding 0.25mmol/L EDTA are carried out, and it can be obtained from FIG. 3 that the concentration of EDTA in the reaction system solution decreases with the increase of the reaction time, because the organic ligand EDTA mainly exists in the liquid phase, the organic ligand EDTA is consumed in the degradation reaction process of the trichloroethylene, and the composite ligand agent consisting of the organic ligand EDTA and the inorganic ligand TPP has synergistic effect in the process of removing organic pollutants, the removal rate of EDTA is higher than that of a single EDTA ligand, which shows that the composite ligand medicament can further accelerate the degradation of EDTA, further reduce the residual of EDTA in the water body and avoid the secondary pollution of the water body caused by the EDTA organic ligand.

As shown in figure 4, in order to study the concentration change of TPP in a solution in the process of degrading organic pollutants by a composite ligand consisting of organic ligand EDTA and inorganic ligand TPP, 0.75mmol/L of TPP is independently added, 0.5mmol/L of TPP is independently added, and 0.25mmol/L of TPP is independently added as a comparison test, as can be seen from figure 4, along with the increase of reaction time, the concentration of TPP in the solution is reduced, the inorganic ligand TPP is mainly adsorbed on the surface of a sediment, and the inorganic ligand is not easily decomposed in a reaction system, which indicates that the adsorption amount of the inorganic ligand TPP on the surface of the sediment is increased, the added inorganic ligand TPP is complexed with ferrous iron or ferric iron in the solution and is adsorbed on the surface of the sediment, so that the secondary pollution of a water body caused by the inorganic ligand TPP entering a liquid phase is avoided, and the environmental protection is facilitated.

As shown in figure 5, the invention uses the composite medicament consisting of the organic ligand and the inorganic ligand, and jointly regulates and controls the ferrous form of ferrous deposit in an aquifer through the synergistic action of the organic ligand and the inorganic ligand, so that the efficiency of activating molecular oxygen to generate hydroxyl radical is maximized, the high-efficiency degradation of organic pollutants is achieved, meanwhile, the organic ligand is oxidized and removed by the hydroxyl radical, the inorganic ligand is adsorbed on the surface of the deposit, and the secondary pollution of the water body caused by the residual organic ligand and the inorganic ligand in the added composite ligand in the water body is avoided.

The agent can efficiently activate molecular oxygen to degrade pollutants, transfers solid-phase electrons in sediments to liquid phase by utilizing the complexation of inorganic ligand, improves the efficiency of generating hydroxyl free radicals by activating molecular oxygen with ferrous iron in sediments, simultaneously utilizes the synergistic action of added organic ligand and inorganic ligand, can reduce the use concentration of the agent, has the advantages of high treatment speed, high efficiency, low cost, environmental protection and the like, and generates great economic benefit and social benefit in the fields of polluted sites and groundwater remediation.

The above is not relevant and is applicable to the prior art.

The features of the embodiments and embodiments described herein above may be combined with each other without conflict.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A formulation for degrading organic pollutants based on the enhanced ferrous deposit activated molecular oxygen in an aquifer, wherein the formulation comprises an inorganic ligand and an organic ligand; the organic ligand at least comprises two carboxyl groups, has strong complexing ability with ferrous iron and ferric iron, and has poor adsorbability of a complex formed by the organic ligand with the ferrous iron and the ferric iron on a deposit; the inorganic ligand is a phosphorus ligand, the complexing ability of the inorganic ligand with ferrous iron and ferric iron is strong, and the adsorbability of a complex formed by the inorganic ligand with ferrous iron and ferric iron on sediment is strong.

2. The formulation of claim 1, wherein the mass ratio of the organic ligand to the inorganic ligand is 1: 1 to 9.

3. The formulation of claim 2, wherein the mass ratio of the organic ligand to the inorganic ligand is 1: 3.

4. the formulation of claim 3, wherein said organic ligand is one or more of sodium ethylenediaminetetraacetate, nitrilotriacetic acid, N' -ethylenediaminedisuccinic acid, ethyleneglycol bis (2-aminoethyl ether) tetraacetic acid, diethylenetriaminepentaacetic acid, and citric acid.

5. The formulation of claim 4, wherein said inorganic ligand is one or more of tripolyphosphate, tetrapolyphosphate, hexapolyphosphate, polyphosphate, phosphate, and pyrophosphate.

6. The formulation of claim 5, wherein the organic ligand is ethylenediaminetetraacetic acid and the inorganic ligand is triphenyl phosphate.

7. The method of using the formulation of claims 1-6 based on the enhancement of ferrous deposit activation molecular oxygen degradation organic pollutants in an aquifer, wherein the aquifer contains ferrous deposits, comprising the steps of:

s2, preparing a medicament solution;

s4, conveying the solution formed in the step S2 to a water-bearing layer through the hydraulic driving action of the circulating well;

8. The method of using the formulation of claim 7 for the treatment of organic pollutants by activating molecular oxygen based on ferrous iron deposits in the aquifer, wherein the total concentration of the formulation in the aqueous layer in the dissolved state is 0.1-2mmol/L in step S4.

9. The method of claim 8 wherein the total concentration of the pharmaceutical agent in the aqueous layer that forms a dissolved state is 1 mmol/L.