CN111560255A - Agent for in-situ chemical oxidation remediation of soil or underground water and use method thereof - Google Patents

Abstract

The invention provides a medicament for restoring soil and underground water by in-situ chemical oxidation and a using method thereof, wherein the medicament comprises 1) an enzyme preparation or a pseudo-enzyme preparation, 2) an oxidant which can be at least used as an electron acceptor for oxidizing a polluted substrate together with the enzyme preparation or the pseudo-enzyme preparation, and the adding mass concentration ratio of the oxidant to the enzyme preparation is 1 (0.1-1 × 10)⁶) Oxygen, oxygenThe molar concentration ratio of the reagent to the pseudoenzyme preparation is 1 (0.001-1 × 10)³). The medicament using method comprises the following steps: proportionally mixing the enzyme preparation or the mimic enzyme preparation with an oxidant and injecting the mixture into polluted soil underground water; or injecting the enzyme preparation or the mimic enzyme preparation into the ground and then injecting the oxidant; or the oxidizing agent is injected into the polluted soil underground water firstly, and then the enzyme preparation or the mimic enzyme preparation is injected. The agent does not need an iron-containing activating agent, has mild use conditions, efficiently removes underground pollutants, has no secondary pollution, and has small disturbance to the ground or underground ecological environment.

Description

Agent for in-situ chemical oxidation remediation of soil or underground water and use method thereof

Technical Field

The invention belongs to the field of environmental pollution treatment, and particularly relates to a medicament for in-situ chemical oxidation remediation of soil or underground water and a use method thereof.

Background

With the deep promotion of industrialization and urbanization processes and the upgrading and adjustment of industrial structures, China is exposed to more and more environmental pollution problems. Among them, the unorganized discharge of industrial "three wastes", the unreasonable application of pesticides and the random stacking of domestic wastes cause organic pollutants or heavy metals to directly or indirectly enter the environment, resulting in serious soil/groundwater pollution. Soil pollution can not only destroy soil quality and reduce land productivity, but also cause underground water and atmospheric pollution through forms of rainwater leaching, surface runoff, atmospheric sedimentation and the like, and seriously threatens the physical health of residents, the safe production of crops and even the ecological environment. Environmental pollution has been a great concern to national governments and social circles, and a series of policy and regulations are put out in succession to effectively guide environmental remediation and treatment. The soil pollution prevention and treatment method of the people's republic of China has been implemented in 2019, and the prevention, treatment and remediation of soil pollution are in accordance with the law.

The green sustainable remediation of the polluted site is one of the hotspots and difficulties of research. According to different treatment modes, the polluted site restoration technology is divided into ectopic restoration and in-situ restoration. Among them, in-situ repair is approved and advocated by the U.S. environmental protection agency (USEPA) of authoritative institutions and researchers in the industry due to its numerous advantages of high repair performance, small ground disturbance, strong sustainability, small public impact and the like. Among the numerous remediation technologies, In Situ Chemical Oxidation (ISCO) is recognized as a cost-effective site remediation technology that can rapidly and efficiently remediate high concentrations of organic contaminants in contaminated sites. The repairing process is a process of injecting an oxidation medicament prepared into a liquid state or a slurry state into a polluted area through a pump, then enabling the medicament and pollutants in soil and underground water to have physical, chemical or biological effects, reducing the content of the pollutants through fixing, transferring, absorbing, degrading or converting and the like, and converting the pollutants into low toxicity or non-toxicity.

Conventional in situ chemical oxidation remediation techniques inject an oxidizing or reducing agent and its activator into the contaminated soil area as a remediation agent by mixing the agent with the agent and allowing the activator to catalyze the oxidizing or reducing agent to generate active radical species to attack the contaminants in the soil. However, when the oxidant is injected into the ground, only a small part of the oxidant can generate a free radical chain reaction with the surface of iron minerals in the soil, and most of the oxidant can be subjected to ineffective decomposition by the iron and manganese minerals in the soil to generate oxygen and water, so that a large amount of waste is caused, and the residual oxidant cannot support the generation of active species in a large radius range. In addition, the common activating agent in the conventional method is a metal compound such as an iron-based compound, cannot be fully utilized in neutral soil, is difficult to remove pollutants efficiently, and is easy to generate secondary pollutants such as iron mud and the like which are difficult to treat. To increase iron availability, acids are typically injected into the ground for pH adjustment, areas with too large a buffering capacity for the aquifer do not effectively acidify the iron-based compounds, and the peracid environment risks disturbing the original ecosystem in the ground.

Based on the above, there is a need for a formulation that can be used under wide pH conditions and that can efficiently remediate contaminated site soils and groundwater. Enzyme preparations can meet this need. In nature, many oxidases from bacteria, fungi and plants play an important role in waste treatment applications. Peroxidase or phenol oxidizing enzyme can act on specific stubborn pollutants, and the pollutants are converted into other products such as humus and the like in a precipitation, nucleophilic attack, oxidative coupling or rearrangement mode, so that final treatment with more environmental benefits is obtained. The mechanism is, for example, peroxidase, which can be in H₂O₂Or under the condition of existence of small molecular organic peroxide, firstly oxidizing and opening a polluted substrate to form free radicals, oxidizing substrate molecules to form the free radicals, and then forming corresponding polymers and compounds in modes of rearrangement, coupling and the like, thereby achieving the purposes of reduction and harmlessness of pollutants. The enzyme catalysis process has the characteristics of mild reaction conditions, specificity, high efficiency and the like, can be realized only by trace oxidant, greatly reduces the repair cost of polluted sites, also reduces the safety risk of the oxidant such as hydrogen peroxide during ground transportation and application, and finally forms humus products which can increase the water absorption and fertilizer retention capacity of soil and improve the physical and chemical properties of the soil.

Disclosure of Invention

Based on the above, there is a need to provide an in-situ chemical oxidation agent that has low risk of secondary pollution, has little disturbance to the underground ecological environment, and can efficiently remove organic pollutants in soil and underground water.

In order to solve the existing problems of oxidation remediation, the invention discloses a formula and a use method of a medicament for in-situ chemical oxidation remediation of soil or underground water.

The invention is realized by the following technical scheme:

an agent for in-situ chemical oxidation remediation of soil or groundwater, wherein the agent formulation comprises: (1) an enzyme preparation or a pseudoenzyme preparation;

(2) an oxidizing agent which can act at least in conjunction with the enzyme preparation or the mimic enzyme preparation as an electron acceptor for oxidizing the contaminated substrate;

the adding mass concentration ratio of the oxidant to the enzyme preparation is 1 (0.1-1 × 10)⁶) The molar concentration ratio of the oxidant to the pseudoenzyme preparation is 1 (0.001-1 × 10)³)。

The enzyme preparation is one or a mixture of more of peroxidase, superoxide enzyme, laccase, tyrosinase and polyphenol oxidase;

the enzyme preparation is a mixture of one or more of a nonmetal compound, a metal oxide and a metal complex which can perform a color reaction with an enzyme substrate in the presence of an oxidant, and a mixture of one or more of a modified substance of the above substances;

the oxidant comprises one or a mixture of more of hydrogen peroxide, ozone, oxygen, persulfate, percarbonate, potassium permanganate and dissolved oxygen in water.

The enzyme preparation is preferably one of manganese dioxide, manganese oxyhydroxide, copper oxide, copper hydroxide, nano ferroferric oxide, nano cobaltosic oxide, ferric oxychloride, gold nanoclusters and graphene oxide.

The modifier of the pseudoenzyme preparation is a simple substance or a compound which can still perform color reaction with an enzyme substrate after the physical property and the chemical property of the substance are changed by means of loading, doping, intercalation, complexation or modification.

The concentration of the oxidant is 1 × 10^-5M to 10M;

the enzyme activity of the enzyme preparation is 1-1 × 10⁶U/mg, concentration in contaminant of 0.01unit/ml to 1 × 10^-5unit/ml；

The concentration of the pseudoenzyme preparation in the pollutant is 1 × 10^-5M to 10M.

The invention also provides a use method of the medicament.

The use method of the agent for restoring soil or underground water by in-situ chemical oxidation is characterized in that the enzyme preparation or the mimic enzyme preparation is mixed with an oxidant according to the proportion and then injected into the polluted soil or underground water;

or, firstly, injecting the enzyme preparation or the mimic enzyme preparation into the polluted soil or underground water, and then injecting the oxidant;

or, the oxidizing agent is injected into the polluted soil or underground water, and then the enzyme preparation or the mimic enzyme preparation is injected.

The principle of the invention is that the enzyme preparation or the pseudo-enzyme preparation firstly oxidizes the polluted substrate into free radicals, then the free radicals are continuously coupled with the polluted substrate to form stable humus, the toxicity of the pollutants is removed, and the polluted substrate is separated from the underground water body. It has the obvious advantages that: (1) the soil conditioner does not contain an iron-based activator, has low risk of generating secondary pollution (2) can be applied to stubborn pollutants, can be operated under the conditions of wide pH, temperature and salinity (3) has small disturbance on underground environment, humic acid contained in soil can promote the agent to convert pollutants sometimes, and the process is easy to control.

Drawings

FIG. 1 is a graph of the change in absorbance of a reaction of a pseudoenzyme preparation with an enzyme substrate in specific example 1;

FIG. 2 is a graph showing the concentration ratio of aniline converted to contaminant removal by the reagent in example 1;

FIG. 3 is a pseudo first order reaction (-ln (C/C) for conversion of the agent to remove contaminant aniline in specific example 1₀) Time) diagram from which K can be derived_obs；

FIG. 4 is a graph showing the variation of the concentration ratio of hydroquinone for the conversion and removal of contaminants in the case of embodiment 2;

FIG. 5 is a graph showing the concentration ratio of aniline as a contaminant for conversion and elimination of the chemical in example 3;

FIG. 6 is a pseudo first order reaction (-ln (C/C) of the agent conversion to eliminate aniline as a contaminant in example 3₀) Time) diagram from which K can be derived_obs；

Detailed Description

The present invention is further explained with reference to the drawings and the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

In the embodiment, a laboratory simulation underground water tank is used as a treatment background. Birnessite (-MnO) is to be adopted₂) Taking 10mg of birnessite to disperse in 10ml of deionized water, performing ultrasonic treatment for 30min to uniformly disperse, taking pyrogallol as an enzyme substrate, preparing a reaction solution with the concentration of 3mM, simultaneously containing a PIPES-NaOH buffer solution with the pH value of 7, taking 2ml of the reaction solution, putting the reaction solution into a quartz cuvette with the length of 1 × 1 × 4cm, adding 1ml of birnessite dispersion solution, slightly shaking, putting the mixture into an ultraviolet spectrophotometer, detecting the absorbance change at the maximum absorption wavelength of 420nm of the pyrogallol reactant, replacing the birnessite reaction solution with the deionized water to repeat the steps, and taking a blank control test, wherein the result (shown in figure 1) shows that the absorbance of the reaction group containing the birnessite has a remarkable rising trend along with the change of the absorption wavelength of 420nm, thereby indicating that the birnessite and the enzyme substrate can generate a color reaction.

The results prove that the birnessite has the pseudoenzyme activity and can be used as a pseudoenzyme preparation for later use. Therefore, in the embodiment, birnessite dispersion liquid is used as the pseudoenzyme preparation in the medicament formula, dissolved oxygen in system water is used as the oxidant in the formula, and the molar concentration ratio of the oxidant to the pseudoenzyme preparation is 1 (10-18). The reaction systems described below were performed in triplicate, the results were averaged, and error bars were calculated, as shown in the figure.

(1) 50mg of birnessite was dispersed in 10ml of deionized water for use. Preparing 50mg/L aniline solution, adjusting pH to 7 with PIPES-NaOH buffer solution, simulating aniline pollution to groundwater in near neutral state, and introducing O₂Keeping the concentration of dissolved oxygen in water at 10-20 mg/L, and using the dissolved oxygen in water as a reaction oxidant. All reactions are carried out at normal temperature;

(2) taking 18ml of aniline reaction liquid, putting 2ml of prepared pseudoenzyme preparation into the reaction liquid, and reacting for 60min, wherein the concentration of the pseudoenzyme preparation is 500 mg/L;

(3) menstrual disorderSampling is carried out at the same time, a polyethersulfones pes membrane filter head with the pore diameter of 0.22 mu m is used for filtering, and birnessite in the pseudo-enzyme preparation is filtered out to stop the reaction. Measuring the concentration change of the aniline by liquid chromatography, and recording the peak area value of the unreacted aniline stock solution as A₀Comparing the peak area A measured by each sampling point with the original solution, A/A₀Approximate to aniline concentration ratio C/C₀The change in aniline concentration was further analyzed by equality, and the apparent rate constant of the reaction was calculated.

In this example, a conventional in-situ chemical oxidation method is added to a pollutant system to prepare a common medicament formula: hydrogen peroxide and its iron-based activator (gamma-FeOOH or Fe)₂O₃) The mixture of (a) was subjected to pollutant degradation as a performance comparison of the pollutant removal efficiency of the present invention. Control experiments were performed in triplicate and the results were averaged. The specific operation is as follows:

(1) 10mg of an iron-based activator gamma-FeOOH or Fe₂O₃Mixed with 1ml of 1M hydrogen peroxide and put into 20ml of an aniline simulated contamination system with a concentration of 50 mg/L. The reaction system further contained 2mM buffer solution (PIPES-NaOH) with pH 7, and maintained a reaction environment that simulated groundwater to be nearly neutral.

(2) Samples were taken at different time points, 1ml of the reaction solution was aspirated and the iron-based activator was filtered off with a polyethersulfone membrane filter having a pore size of 0.22 μm, and an equal amount of methanol was added to the sampled samples to quench the reactive oxygen species generated by the reaction, thereby stopping the reaction.

(3) Measuring the concentration change of the aniline by liquid chromatography, and recording the peak area value of the unreacted aniline stock solution as A₀Comparing the peak area A measured by each sampling point with the original solution, A/A₀Approximate to aniline concentration ratio C/C₀The change in aniline concentration was further analyzed by equality, and the apparent rate constant of the reaction was calculated.

Example 2 this example uses birnessite (-MnO)₂) The enzyme preparation is formulated, and hydrogen peroxide is the oxidizing agent. Hydroquinone is used as a remediation target organic pollution substrate in simulated underground water. Mixing oxidant and pseudoenzyme preparation, and adding into simulated polluted underground waterThe adding molar concentration ratio is about 1 (0.5-1), and the specific operation is as follows:

(4) 5mg of birnessite is put into 5ml of 20mM hydrogen peroxide solution to be fully mixed, and the mixed solution is put into 15ml of hydroquinone simulated pollution system with the concentration of 30 mg/L. The reaction system further contained a 2mM buffer solution (PIPES-NaOH) with pH 6.8, and maintained a reaction environment that simulated groundwater to be nearly neutral.

(5) The mixture was added to the simulation system and immediately sampled, as reaction 0, and then sampled every time interval at the same time. When sampling, a disposable syringe is used for sucking 1ml of reaction liquid, and a polyethersulfone membrane filter head with the aperture of 0.22 mu m is used for filtering the birnessite to stop the reaction.

(6) Measuring the content change of hydroquinone in the sample by liquid chromatography, and recording the peak area of hydroquinone at the reaction 0 point as A₀Comparing the peak area A measured by each sampling point with the original solution, A/A₀Approximate to the hydroquinone concentration ratio C/C₀And the content change of the pollutant hydroquinone is further analyzed.

Example 3

The enzyme preparation is prepared by taking tyrosinase as a formula, the enzyme activity is 4000U/mg, and the enzyme preparation is applied at the concentration of 40 unit/ml. The oxidant is dissolved in water, and the concentration of the oxidant is about 10-20 mg/L. The adding mass concentration ratio of the oxidant to the enzyme preparation is 1 (500-1000). The system without tyrosinase was used as a control. The reaction systems described below were performed in triplicate, the results were averaged, and error bars were calculated, as shown in the figure.

(1) 0.03mM of 4-chloroaniline solution was prepared and the pH was adjusted to 6 with acetic acid-sodium acetate buffer solution to simulate underground contaminated water. Introduction of O into the simulation System₂Keeping the concentration of dissolved oxygen in water at 10-20 mg/L, and taking the dissolved oxygen in water as a reaction oxidant, and carrying out all reactions at normal temperature;

(2) reacting in a reaction system of 10ml, adding the enzyme preparation into 4-chloroaniline reaction solution, adding the enzyme preparation into the reaction system with the concentration of 40unit/ml for reacting for 12 hours;

(3) the sampling is carried out over different time periods,0.15ml of concentrated nitric acid was added to stop the reaction. The change in the concentration of 4-chloroaniline was tested using high performance liquid chromatography and the apparent rate constant of the reaction was calculated. Measuring the concentration change of the aniline by liquid chromatography, and recording the peak area value of the unreacted aniline stock solution as A₀Comparing the peak area A measured by each sampling point with the original solution, A/A₀Approximate to aniline concentration ratio C/C₀The change in aniline concentration was further analyzed by equality, and the apparent rate constant of the reaction was calculated.

The concentration changes of the aniline and 4-chloroaniline as the contaminating substrates in the examples were determined by high performance liquid chromatography. Aniline recorded data at 230nm of its uv maximum absorption wavelength, hydroquinone at 285nm, and 4-chloroaniline at 254 nm. According to the data of the application example 1, fig. 2 and fig. 3 are obtained, which are the first-order fit of the absorbance change curve, the aniline concentration change curve and the degradation kinetics of the reaction of birnessite and the enzyme substrate, respectively. The results show that the pseudoenzyme preparation can efficiently degrade the organic polluted substrate under the neutral condition, the apparent rate constant of the pseudoenzyme preparation is 0.047/min, and the pseudoenzyme preparation contains an iron-based activator (gamma-FeOOH or Fe)₂O₃) The mixture with the oxidizing agent was 20 and 142 times higher, respectively. FIG. 4 is a graph showing the change of the concentration ratio of the formulation in example 2 to remove hydroquinone, showing that the removal rate of hydroquinone is more than 95% after 2 hours of reaction. FIG. 5 and FIG. 6 are the first-order fits (R) of the concentration profile and degradation kinetics of 4-chloroaniline in application example 3²>0.92) and the result shows that the medicament formula can convert the organic pollutant 4-chloroaniline by about 90 percent after the reaction is carried out for 10 hours. The medicament formula of the invention is proved to be capable of effectively converting organic pollutants under near-neutral conditions.

Claims (6)

1. An agent for in-situ chemical oxidation remediation of soil or groundwater, wherein the agent formulation comprises: (1) an enzyme preparation or a pseudoenzyme preparation;

(2) an oxidizing agent which can act at least in conjunction with the enzyme preparation or the mimic enzyme preparation as an electron acceptor for oxidizing the contaminated substrate;

the oxidant and the enzyme preparation are addedThe mass concentration ratio of the additive is 1 (0.1-1 × 10)⁶) The molar concentration ratio of the oxidant to the mimic enzyme preparation is 1 (0.001-1 × 10)³)。

2. The medicament of claim 1, wherein the enzyme preparation is one or more selected from the group consisting of peroxidase, superoxide enzyme, laccase, tyrosinase, and polyphenol oxidase;

the enzyme preparation is a mixture of one or more of a nonmetal compound, a metal oxide and a metal complex which can perform a color reaction with an enzyme substrate in the presence of an oxidant, and a mixture of one or more of a modified substance of the above substances;

the oxidant is one or a mixture of more of hydrogen peroxide, ozone, oxygen, persulfate, percarbonate, potassium permanganate and dissolved oxygen in water.

3. The medicament of claim 1, wherein said oxidizing agent has a concentration of 1 × 10^-5M～10M；

The enzyme activity of the enzyme preparation is 1-1 × 10⁶U/mg, concentration in contaminant of 0.01unit/ml to 1 × 10^{- 5}unit/ml；

The concentration of the pseudoenzyme preparation in the pollutant is 1 × 10^-5M to 10M.

4. The medicament of claim 2, wherein the pseudoenzyme preparation is one selected from manganese dioxide, manganese oxyhydroxide, copper oxide, copper hydroxide, nano-ferroferric oxide, nano-tricobalt tetroxide, ferric oxychloride, gold nanoclusters, and graphene oxide.

5. The agent according to claim 2, wherein the modified substance of the pseudoenzyme preparation is a simple substance or a compound which can still perform a color reaction with an enzyme substrate after the physical and chemical properties of the substance are changed by loading, doping, intercalation, complexation or modification means.

6. A method of using the agent of claims 1-5, wherein the enzyme preparation or pseudoenzyme preparation is mixed with an oxidizing agent and injected into contaminated soil or groundwater in the ratio;

or, firstly, injecting the enzyme preparation or the mimic enzyme preparation into the polluted soil or underground water, and then injecting the oxidant;

or, the oxidizing agent is injected into the polluted soil or underground water, and then the enzyme preparation or the mimic enzyme preparation is injected.

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