CN112624508A - Immobilized enzyme-based slow-release Fenton-like system and method for in-situ remediation of groundwater pollution by using same - Google Patents

Immobilized enzyme-based slow-release Fenton-like system and method for in-situ remediation of groundwater pollution by using same Download PDF

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CN112624508A
CN112624508A CN202011506752.7A CN202011506752A CN112624508A CN 112624508 A CN112624508 A CN 112624508A CN 202011506752 A CN202011506752 A CN 202011506752A CN 112624508 A CN112624508 A CN 112624508A
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water
well
solution
reactor
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CN112624508B (en
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李孟
李泽丰
杜宁
张倩
李程威
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Wuhan University of Technology WUT
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/722—Oxidation by peroxides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/00—Nature of the contaminant
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    • C02F2101/20—Heavy metals or heavy metal compounds
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/30—Organic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06—Contaminated groundwater or leachate
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
    • C02F3/342—Biological treatment of water, waste water, or sewage characterised by the microorganisms used characterised by the enzymes used

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Abstract

The invention discloses a slow-release Fenton-like system based on immobilized enzyme and provides a method for in-situ remediation of groundwater pollution, which mainly comprises the following steps: 1) selecting a central well and a plurality of peripheral medicine adding wells in a pre-repaired underground water pollution area; 2) adding the green rust into the medicine adding well, pumping water into the central well, and recharging the water into underground water through the medicine adding well; pumping water continuously until green rust appears; 3) arranging an immobilized enzyme reactor in each medicine adding well, aerating, and introducing a glucose solution; pumping water with small water amount in the central well and recharging to underground water through the medicine adding well; pumping water until the concentration of the effluent pollutants reaches the standard. The slow-release Fenton-like system has a pH range close to the environment where underground water is located, can realize the lasting slow release of free radicals and the controllability of a degradation area in the whole process, can not introduce other pollutants into the underground water, and can realize non-toxicity and harmlessness.

Description

Immobilized enzyme-based slow-release Fenton-like system and method for in-situ remediation of groundwater pollution by using same
Technical Field
The invention belongs to the technical field of groundwater pollution remediation, and particularly relates to a slow-release Fenton-like system based on immobilized enzyme and a method for in-situ remediation of groundwater pollution by using the slow-release Fenton-like system.
Background
Water resources are one of the most important environmental resources of people, which not only affect the life and production of people, but also affect the health and life safety of people to a great extent. The stacking of harmful wastes generated in industrial production, the residue of a large amount of organic pesticide and fertilizer in soil in agricultural production, the accumulation of mining gangue and the like, and pollutants contained in the substances enter underground water in a large amount under the action of rainwater and underground runoff thereof. So that most cities in China face more or less groundwater pollution.
At present, the repair technology of groundwater pollution is mainly divided into in-situ repair and ex-situ repair, wherein the most widely applied in the in-situ repair technology is Permeable Reactive Barrier (PRB) technology, and in the engineering practice process, a PRB system may fail due to loss of activity of a reaction medium, change of hydraulic conditions, even errors in process design and other factors, and a blocking phenomenon is easily generated. The ectopic repair technology generally has the problems of high economic cost, complex operation management and the like.
The Fenton reaction utilizes Fe2+And H2O2The reaction generates hydroxyl free radical with strong oxidizing property, and the pollutant is decomposed into small molecular substance or is further mineralized and decomposed into CO under the action of the hydroxyl free radical2And H2And O. Meanwhile, a series of Fenton-like systems are generated in the subsequent development process, such as the change of an electron donor and H in reaction2O2In situ generation. In the Fenton reaction, reactants and products are friendly to the underground water environment, so that the Fenton reaction has certain potential in repairing underground water pollution.
Conventional Fenton reaction, due toThe characteristics of self reaction (a large amount of OH is generated simultaneously, the OH cannot be quickly and fully contacted with pollutants in underground water, and the OH quenches), reaction conditions and a reaction generating device are difficult to be applied to underground water pollution remediation. Chinese patent CN 106966484A discloses a method for utilizing Fe3O4/CaO2A method for degrading benzene series in underground water by a heterogeneous Fenton-like reaction system. The method comprises the steps of controlling the pH value to be 4-7 at normal temperature, and adding calcium peroxide and nano ferroferric oxide into benzene series polluted water. The method has the disadvantages that the reaction of the agent after contacting with water is too violent, the utilization efficiency of the agent is low, and the pH range of the method is difficult to realize in-situ groundwater remediation.
Chinese patent CN 110759319A discloses a method for removing chlorohydrocarbons and benzene series in underground water by activating slow-release nano calcium peroxide with ferrous sulfide. The method takes calcium chloride, hydrogen peroxide with the mass fraction of 30 percent and ammonia water as raw materials, adds different dispersants, and then adds different macromolecular polymers such as polyethylene glycol 400(PEG400) and the like to lead the calcium chloride to be in nCaO2Forming a film on the surface to obtain the slow-release nano calcium peroxide advanced oxidation material embedded by the macromolecular polymer, and realizing the slow-release contact of the calcium peroxide and water to generate H2O2. However, this method introduces sulfides, as well as some macromolecular organics, into the groundwater.
Therefore, the current Fenton-like reaction system has a plurality of defects in the groundwater pollution remediation process, such as the introduction of other pollutants, H2O2Low utilization rate, low in-situ generation rate and the like, and has the problems that the movement of the underground water is random under the natural condition, the oxidant is difficult to control after being added and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a slow-release Fenton-like system based on immobilized enzyme and a method for in-situ remediation of groundwater pollution by using the slow-release Fenton-like system based on immobilized enzyme. The slow-release Fenton-like system of the immobilized enzyme has a pH (7.2-7.8) range closer to the environment where underground water is located, and the whole process can realize the lasting slow release of free radicals and the controllability of a degradation area; in addition, other pollutants can not be introduced into the underground water in the whole system, and the non-toxicity and harmless treatment can be realized.
The technical scheme adopted by the invention for solving the problems is as follows:
a slow-release Fenton-like system based on immobilized enzyme comprises sulfate patina GR (SO 4)2-) The glucose solution and the immobilized glucose oxidase.
According to the scheme, the immobilized glucose oxidase is gel particles, the diameter of the immobilized glucose oxidase is 2-4 mm, and the enzyme activity is 100-120U/g. Preferably, the preparation method of the immobilized glucose oxidase comprises the following steps: and (3) immobilizing the glucose oxidase by adopting an embedding method to obtain the immobilized glucose oxidase. The preparation method comprises the following steps:
(1) preparing a Glucose Oxidase (GOD) solution with a certain concentration range; the concentration of the GOD solution is 130-160U/ml;
(2) preparing a mixed solution A of sodium alginate and gellan gum with a certain concentration, stirring and dissolving in a boiling water bath, and cooling to room temperature; wherein the mass fraction of the sodium alginate in the mixed solution is 1.0-1.5%, and the fraction of the gellan gum is 0.4-0.7%;
(3) mixing the mixed solution A obtained in the step (2) with the GOD solution obtained in the step (1) according to a volume ratio of 1: 25-40 to obtain a mixed solution B;
(4) preparing CaCl with a certain concentration2A solution; CaCl2The mass fraction is 10-13%;
(5) dropping the mixed solution B into CaCl2And (3) standing the solution after the dropwise addition is finished to obtain gel beads, namely the immobilized glucose oxidase, and controlling the dropwise addition speed (for example, 5 drops/s) and the dropwise addition height (for example, the dropwise addition height is 15cm) to ensure that the diameter of the gel beads is 2-4 mm.
The method for in-situ remediation of groundwater pollution by adopting the immobilized enzyme-based slow-release Fenton-like system mainly comprises the following steps:
1) selecting a central well and a plurality of peripheral medicine adding wells in a pre-repaired underground water pollution area;
2) in the first stage, green rust is added into a medicine adding well, then a central well pumps water with a large amount (the pumping amount per minute is 1/400-1/2000 of the water amount in a pre-repaired underground water pollution area), and the water pumped by the central well is re-filled into underground water through the medicine adding well;
3) the water pumping in the step 2) is continued until the central well is rusted, and the central well is stopped to pump water;
4) in the second stage, an immobilized enzyme reactor is arranged in each medicine adding well, aeration is carried out on the immobilized enzyme reactor, and meanwhile, a glucose solution is introduced; pumping water with a small amount of water in a central well (the pumping amount per minute is 1/3000-1/6000 of the water amount in the underground water pollution area to be repaired), and recharging the water pumped by the central well to the underground water through a medicine feeding well;
5) and 4) in step 4), when the concentration of the pollutants in the effluent of the central well is below a target value, the reaction is terminated, and the remediation of the underground water polluted area is completed.
According to the scheme, a central well is selected in the center of the area of the pre-repaired underground water pollution area in the step 1), the central well is used as the center of a circle, medicine adding wells are approximately distributed on the periphery of the repair area, the wells are all complete wells (namely, the wells are drilled to a water-resisting bottom layer), and the size of the wells meets the actual water pumping requirement. Preferably, in practical engineering, the pre-remediated groundwater pollution area should be less than 0.25km2Every 0.03km2A medicine feeding well is arranged in the repair area, and the repair area can be divided into a plurality of blocks for repair when the area of the repair area is large.
According to the scheme, the adding amount of the patina in the step 2) is 0.15-0.3 mol/m3The addition amount of the ferrous iron equivalent (calculated as ferrous iron) of the green rust is 0.15-0.3 mol per cubic meter of the water amount in the underground water polluted area to be repaired, and the addition amount is preferably in the form of solution.
According to the scheme, the immobilized enzyme reactor is a reactor loaded with immobilized glucose oxidase; the reactor is provided with a hollow cavity, an upper and lower alternative guide plate is arranged in the hollow cavity and used for circulating reflux of liquid in the hollow cavity (ensuring the hydraulic retention time (generally more than 30min) of glucose solution in the hollow cavity), a stainless steel filter screen is arranged in the middle of the outer side wall of the reactor, a three-phase separator is arranged at the outlet of the hollow cavity of the reactor, an aerator is arranged at the end part inside the reactor, a gas discharge pipe is inserted into the three-phase separator, and a glucose adding pipe and the head part of the aerator pipe are inserted into the hollow cavity through the three-phase separator.
According to the scheme, the aeration rate in the step 4) is 3-4 m calculated according to the volume of the solution in the reactor3/(m3H), the ratio of the flow rate of the glucose solution fed to the central well pumping in step 4) is 1: 20 to 30. Preferably, the concentration range of the glucose solution is 0.05-0.2 mol/L.
The working principle of the invention mainly comprises the following two stages:
in the first stage, the green rust is added into the peripheral drug adding wells, and large-water-volume water pumping is carried out through the central well, so that the directional migration of the green rust in the water-containing layer is realized, the added green rust is ensured to reach the position of the preset water-containing layer, and the pumped water is re-pumped to the underground water through the peripheral wells. The process is shown in figure 5. When the central well has the green rust, the green rust is indicated to be fully distributed in the aquifer, and the water pumping of the central well is stopped. The patina can realize the adsorption of a large amount of organic pollutants through the adsorption effect of the patina in the movement stage, realize the enrichment and directly provide basic guarantee for the high efficiency of the subsequent degradation and oxidation.
And in the second stage, the immobilized enzyme reactor is arranged in a peripheral medicine adding well, aeration is realized through an aeration pipe respectively, and a glucose adding pipe is used for adding a glucose solution. And pumping water with small water amount by using the central well (pumping water and recharging by using peripheral wells). The enriched contaminants are fixed within the intercalation layer of patina by the adsorption of the first stage patina. In this case, the glucose is oxidized by enzyme catalysis to release H2O2Under the action of free diffusion and water flow movement generated by pumping small amount of water, the Fe (II) in the structure state in the green rust is in contact with the green rust for H2O2Activating to generate OH, oxidizing and degrading pollutants in situ to mineralize. The gluconic acid generated by the reaction can react with iron ions to form a complex, and natural adsorption is carried out in the water-containing layer,And (4) settling. In the whole reaction process, the non-toxicity of the externally-added reagent is realized.
Patina acts as a layered double metal hydroxide (LDH) and thus patina has good adsorptive capacity, which can adsorb contaminants by ligand exchange and surface complexation or anion exchange. In low concentration solutions, internal anion exchange occurs predominantly in a high proportion of adsorbate/LDH. Furthermore, the patina interlayer contains many exchangeable anions, and thus can adsorb heavy metal cations, organic anions, and inorganic ions to form an inner layer complex on the patina. In the case of micro-pollution of groundwater, the adsorption enrichment of pollutants can be realized by the green rust in the migration process in the above.
Fe (II) in the patina is structural divalent iron, and compared with dissolved divalent iron, the patina surface has electrons flowing at a high speed, so that the electron flowing efficiency is enhanced, the electron transfer is promoted, and the patina surface has higher catalytic activity. Meanwhile, because the content of Fe (II) in the green rust is higher, the efficiency of catalytically generating active intermediate products (hydroxyl free radicals, superoxide radical and high-valence iron species) can be greatly improved, and the catalytic oxidation system has higher degradation rate.
Compared with the prior art, the invention has the following beneficial effects:
(1) the slow-release Fenton-like system based on the immobilized enzyme has a pH value range closer to the environment where underground water is located, and the whole process can realize the lasting slow release of free radicals and the controllability of a degradation region. In addition, other pollutants can not be introduced into the underground water in the whole system, and the non-toxicity and harmless treatment can be realized. Meanwhile, the invention combines well group water pumping to realize the control of degradation area, and carries out in-situ removal on underground water pollutants, thereby realizing the mineralization degradation of organic pollutants and converting the organic pollutants into H2O and CO2And other pollutants for polluting water bodies are not introduced in the whole process.
(2) The directional migration of the underground water is realized by using a well group pumping test as a starting material, so that the added medicament can migrate in a water-containing layer towards a designated area and direction and reach a designated position, and meanwhile, the area range of the reaction can be controlled.
(3) The invention adopts a glucose-glucose oxidase system to produce H2O2: no external energy initiation is required; producing H in situ with other groundwater2O2Compared with the prior art, the substances involved in the system have the characteristics of no toxicity and no harm. In addition, the glucose oxidase has high specificity, can avoid side reaction with other substances in underground water, and can efficiently and gradually convert glucose into H2O2。
(4) The immobilized enzyme reactor adopted in the invention can realize the repeated utilization of enzyme and provide proper guarantee for economy. Glucose oxidase catalytically oxidizes glucose in the presence of oxygen to produce H2O2The process has the characteristic of continuous and mild property, and the slow release property effectively avoids the generation of H at local part due to the addition or medicament reaction2O2Too high concentration results in locally too high OH concentration, resulting in self-quenching.
Drawings
FIG. 1 is a longitudinal sectional view of an immobilized enzyme reactor;
FIG. 2 is a schematic cross-sectional view taken in the direction 2-2 of FIG. 1;
FIG. 3 is a schematic cross-sectional view taken in the direction 3-3 of FIG. 1;
FIG. 4 is a schematic plan view of a well group arrangement;
FIG. 5 is a schematic diagram of green rust migration;
FIG. 6 is a schematic diagram of the reaction stage.
Wherein, the first step is a glucose adding pipe; secondly, an aeration pipe; thirdly, a gas discharge pipe; fourthly, a three-phase separator; fifthly, fixing and supporting; sixthly, immobilized glucose oxidase; seventhly, a stainless steel filter screen with the aperture of 0.1 mm; eighthly, an aeration head; ninthly, a central well; the charge well is at the charge well;
Figure BDA0002845148220000051
is an immobilized enzyme reactor;
Figure BDA0002845148220000052
is the added patina;
Figure BDA0002845148220000053
a contaminant.
Detailed Description
In order to better understand the present invention, the following examples are further illustrative, but the present invention is not limited to the following examples.
In the following examples, sulfate patina having suitable adsorbability and reducing power was selected while satisfying both the requirements of adsorbability and electron-donating ability. Preparing wet green rust GR (SO 4) by coprecipitation method2-) The method comprises the following specific steps:
1) weighing a certain amount of Fe by using an analytical balance2(SO4)3And FeSO4·7H2The quantity ratio of O (Fe (II) to Fe (III) is 2:1), and the O (II) and the Fe (III) are respectively and fully dissolved in oxygen-free deionized water to prepare Fe2(SO4)3And FeSO4The solution is ready for use;
2) under the condition of no oxygen, taking a three-neck flask as a reactor, and adding FeSO4Putting the solution into a three-neck flask; will produce Fe2(SO4)3Transferring the solution and the 1.0mol/L NaOH solution into a constant pressure funnel, and arranging the constant pressure funnel at two side openings of the flask; to FeSO simultaneously4Dripping Fe into the solution2(SO4)3And NaOH solution, and performing magnetic stirring; the pH value of the reaction is maintained to be about 7.8-8.2 by adjusting the dropping speed of the NaOH solution; after the dropwise addition, the pH value is stabilized at 8.0, and the stirring is continued for 1 h; after stirring, placing the obtained serous fluid in a serum bottle and sealing;
3) and aging the prepared liquid patina in a constant-temperature water bath box for 12 hours at 40 ℃, keeping the liquid patina under an anaerobic condition, sealing and storing the liquid patina, and using the liquid patina in subsequent embodiments, wherein the water content is 96.0-96.9%.
In the following examples, the preparation of immobilized glucose oxidase comprises the following steps:
(1) preparing 150U/ml Glucose Oxidase (GOD) solution;
(2) preparing a mixed solution A of sodium alginate and gellan gum, stirring and dissolving in a boiling water bath, and cooling to room temperature; wherein the mass fraction of the sodium alginate in the mixed liquid is 1.2 percent, and the fraction of the gellan gum is 0.5 percent;
(3) mixing the mixed solution A obtained in the step (2) with the GOD solution obtained in the step (1) according to a volume ratio of 1: 30 to obtain a mixed solution B;
(4) preparing 10 percent of CaCl by mass fraction2A solution;
(5) putting the mixed liquid B into a constant-pressure funnel, and fixing the funnel to ensure that the opening of the funnel is spaced from CaCl2Dripping CaCl into the solution beaker at a speed of 5 drops/s at a liquid level of about 15cm2In solution; after the dropwise addition is finished, standing the gel for 1 h; filtering, washing the gel beads by using deionized water; absorbing the surface moisture with absorbent paper, and storing in a refrigerator at 4 ℃ to obtain immobilized glucose oxidase; wherein the size of the gel bead is 2-4 mm, and the enzyme activity is 100-120U/g.
In the following examples, the immobilized enzyme reactors are shown in FIGS. 1 to 3. The immobilized enzyme reactor is a cylinder made of stainless steel, and a stainless steel filter screen covers an opening on the side wall to realize outflow of reaction mixed liquid; loading immobilized glucose oxidase in the cylinder; a cylindrical up-down alternating guide plate is arranged in the cylinder body, and the circulating reflux is realized under the action of aeration pushing force; a fixed support is arranged between the guide plate and the outer wall of the cylinder body; the three-phase separator (IV) is arranged at an outlet at the center of the top of the cylinder body, and separated gas is discharged into the external environment; the aeration pipe and the glucose feeding pipe are introduced into the bottom of the barrel through a three-phase separator.
In the following examples, a aquifer-underground model was constructed using a scale (length scale: 350: 1) and glass fiber reinforced plastic as materials according to the platinum-han's theorem, and regional groundwater distribution was simulated by the model to perform a degradation test of pollutants. The model is in a cubic structure, the bottom waterproof bottom layer is clay, and the clay is tamped with fine sand for paving; and filling coarse crushed stones in the middle to serve as a water-bearing stratum, paving fine crushed stones on the tops of the coarse crushed stones, paving fine sand on the tops of the fine crushed stones, paving clay on the tops of the fine sand and tamping, reserving a central well and peripheral medicine feeding wells at the center and the periphery, filling water containing pollutants in the model water-bearing stratum by using trichloroethylene as pollutants (the concentration of the trichloroethylene is 5 mg/L).
The experimental process is divided into two stages, wherein in the first stage, the patina is added into the medicine adding well, then the central well performs large-water-volume water pumping (the water pumping volume per minute is 1/400-1/2000 of the water volume in the repaired area), and the water pumped by the central well is refilled to the underground water through the medicine adding well; arranging an immobilized enzyme reactor in each medicine adding well, aerating the immobilized enzyme reactor, and introducing a glucose solution; and pumping water with small water volume (the water pumping volume per minute is 1/3000-1/6000 of the water volume in the repaired area) to the central well, and recharging the water pumped by the central well to the underground water through the medicine feeding well.
The slow-release Fenton-like system of the immobilized enzyme is used for carrying out pollutant simulated degradation experiments in a designed underground water simulation device so as to prove the method and the function of the system for in-situ remediation of underground water pollution.
Example 1
A slow-release Fenton-like system based on immobilized enzyme comprises three parts, namely sulfate patina, a glucose solution and immobilized glucose oxidase; wherein the sulfate patina is in a wet state (the water content is 96.0-96.9%), and is added in a liquid state when in use; the concentration range of the glucose solution is 0.1 mol/L; the diameter of the immobilized glucose oxidase gel particles is 2-4 mm, and the enzyme activity is 100-120U/g.
The method for in-situ remediation of groundwater pollution by adopting the immobilized enzyme-based slow-release Fenton-like system mainly comprises the following steps:
1) the water filling amount in the underground water simulation device is 2m3Selecting a central well at the center of the simulator, taking the central well as the center of a circle, and arranging a medicine adding well at the periphery of a restoration area (the area of the pre-restored underground water pollution area is 2 m)2Calculating according to the Kingham theorem, setting 8 medicine adding wells in total, wherein the water wells are all complete wells (namely, the wells are drilled to a water-proof bottom layer);
2) adding green rust into the drug adding well, then pumping water with large water volume from the central well at the rate of 5L/min, and recharging the water pumped from the central well to underground water through the drug adding well; the total content of ferrous iron of green rust added is 0.5mol, and the green rust is added at one time;
3) the water pumping in the step 2) is continued until the central well is rusted, and the central well is stopped to pump water; at the moment, the water pumping time is 3 hours;
4) an immobilized enzyme reactor is arranged in each medicine adding well (wherein 2000g of immobilized glucose oxidase gel particles in the immobilized enzyme reactor, the enzyme content is calculated by enzyme activity, and the total amount is 2.0 multiplied by 105U), aerating the immobilized enzyme reactor, and simultaneously pumping 0.1mol/L glucose solution at a speed of 15ml/min (the effective volume of the reactor is 5L to ensure that the hydraulic retention time of the reaction solution is more than 30 min); pumping water by a central well at a small water amount of 0.5L/min until the reaction is finished, and recharging the water pumped by the central well to underground water through a medicine adding well;
5) and (3) after 1h, 3h, 6h, 12h, 24h, 48h, 72h, 96h and 168h start in the step 4) (namely when the reaction time is respectively 1h, 3h, 6h, 12h, 24h, 48h, 72h, 96h and 168 h), respectively monitoring the concentration of pollutants in the water pumped from the small water volume of the central well, wherein the test result is shown in table 1, and the time when the water pumped from the central well reaches the corresponding groundwater quality standard is taken as the reaction finishing time, namely the remediation of the groundwater pollution area is finished.
TABLE 1 degradation Rate Change of trichloroethylene
Figure BDA0002845148220000071
Example 2
The difference from example 1 is that: the green rust is added according to the content of Fe (II), and the total content of ferrous iron of the green rust added is 0.10mol, 0.25mol, 0.50mol and 1.00mol respectively.
At the reaction time of 168h, the concentration of the pollutants in the water pumped out from the small water volume of the central well was monitored, and the test results are shown in Table 2.
TABLE 2 Effect of Rust addition Total on trichloroethylene degradation
Figure BDA0002845148220000072
Figure BDA0002845148220000081
Example 3
The difference from example 1 is that: the total enzyme content in the immobilized enzyme reactor is 1.0 × 10 in terms of enzyme activity5U、1.5×105U、2.0×105U、2.5×105U, monitoring the pollutant concentration of the water extracted from the small water volume of the central well at the reaction time of 24h, 72h and 168h under the condition of the total enzyme amount, and the test result is shown in Table 3.
TABLE 3 Effect of enzyme amount on trichloroethylene degradation
Figure BDA0002845148220000082
The results in table 1 show that the Fenton-like system established by the invention can effectively realize degradation in 7 days aiming at underground water pollution caused by low-concentration trichloroethylene. The data result in table 2 shows that the high-efficiency degradation of trichloroethylene can be realized when the adding amount of the green rust reaches a certain degree. The results in Table 3 show that the amount of enzyme in the immobilized enzyme reactor affects the degradation rate of the contaminant, and that the increasing tendency of the degradation rate shows a decreasing state as the amount of enzyme increases.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and changes can be made without departing from the inventive concept of the present invention, which falls into the protection scope of the present invention.

Claims (10)

1. A slow-release Fenton-like system based on immobilized enzyme is characterized by comprising three parts, namely sulfate patina, a glucose solution and immobilized glucose oxidase.
2. The slow-release Fenton-like system based on immobilized enzyme according to claim 1, wherein the immobilized glucose oxidase is gel particles with the diameter of 2-4 mm and the enzyme activity of 100-120U/g; the preparation method comprises the following steps: and (3) fixing the glucose oxidase by adopting an embedding method to obtain the immobilized glucose oxidase.
3. The slow-release Fenton-like system based on immobilized enzyme according to claim 2, wherein the preparation method of the immobilized glucose oxidase comprises the following steps:
(1) preparing a glucose oxidase solution with a certain concentration range;
(2) preparing a mixed solution A of sodium alginate and gellan gum with a certain concentration, stirring and dissolving in a boiling water bath, and cooling to room temperature;
(3) mixing the mixed solution A obtained in the step (2) with the glucose oxidase solution obtained in the step (1) to obtain a mixed solution B;
(4) preparing CaCl with a certain concentration2A solution;
(5) dropping the mixed solution B into CaCl2And (3) standing the solution after the dropwise addition is finished to obtain gel beads with the diameter of 2-4 mm, namely the immobilized glucose oxidase.
4. The slow-release Fenton-like system based on immobilized enzyme according to claim 3, wherein in the step (1), the concentration of the glucose oxidase solution is 130-160U/ml; in the step (2), the mass fraction of sodium alginate in the mixed solution is 1.0-1.5%, and the fraction of gellan gum is 0.4-0.7%; in the step (3), the volume ratio of the mixed solution A to the glucose oxidase solution is 1: 25-40 mixing; in step (4), CaCl2The mass fraction is 10-13%.
5. The method for in-situ remediation of groundwater pollution by using the immobilized enzyme-based slow-release Fenton-like system according to claim 1 is characterized by mainly comprising the following steps:
1) selecting a central well in a pre-repaired underground water pollution area, and arranging a plurality of medicine feeding wells around the central well;
2) in the first stage, sulfate green rust is added into a medicine adding well, then large-water-volume water pumping is carried out on a central well, and water pumped by the central well is re-filled into underground water through the medicine adding well; stopping pumping water to the central well when the water pumping is continued until the central well is rusted;
3) in the second stage, arranging an immobilized enzyme reactor in each medicine adding well, aerating the immobilized enzyme reactor, and introducing a glucose solution; pumping small water quantity to the central well, and recharging the water pumped by the central well to the underground water through the medicine feeding well; pumping water until the concentration of the effluent pollutants of the central well reaches a target value or below, and taking the reaction as a reaction end point to finish the remediation of the underground water polluted area.
6. The method for remediating groundwater pollution in situ as claimed in claim 5, wherein in the step 2), when large-amount water is pumped, the pumping amount per minute is 1/400-1/2000 of the water amount in the groundwater pollution area to be remediated; in the step 3), when small water amount is pumped, the water pumping amount per minute is 1/3000-1/6000 of the water amount in the underground water pollution area to be repaired.
7. A method of in situ remediation of groundwater contamination according to claim 5, characterised in that the pre-remediated groundwater contamination area is less than 0.25km2Every 0.02-0.04 km2A medicine feeding well is arranged in the area of the repair area; the pre-remediated groundwater contaminated area is greater than 0.25km2Sometimes, it is divided into multiple repairs.
8. The method for remediating groundwater pollution in situ as claimed in claim 5, wherein the amount of green rust added in step 2) is 0.15 to 0.3mol/m3The ferrous equivalent of (a) is added in the form of a solution.
9. A method of in situ remediation of groundwater contamination according to claim 5, characterised in that the immobilised enzyme reactor is a reactor loaded with immobilised glucose oxidase; the reactor is provided with a hollow cavity, an upper and lower alternative guide plate is arranged in the hollow cavity and used for circulating reflux of liquid in the hollow cavity, a filter screen is arranged in the middle of the outer side wall of the reactor, a three-phase separator is arranged at the outlet of the hollow cavity of the reactor, an aerator is arranged at the end part inside the reactor and provided with an aerator head, a gas discharge pipe is inserted into the three-phase separator, and a glucose adding pipe and the head part of the aerator pipe are inserted into the hollow cavity through the three-phase separator.
10. A method for in situ remediation of groundwater pollution as claimed in claim 5, wherein the aeration rate in step 3) is 3 to 4m calculated on the volume of the solution in the reactor3/(m3H) the ratio of the flow rate of the glucose solution introduced to the central well pumping flow rate in step 3) is 1: 20-30, the concentration range of the glucose solution is 0.05-0.2 mol/L, and the enzyme activity requirement in the reactor is 7-9 multiplied by 104U/L。
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