Filling material applied to underground permeable reactive barrier technology

Abstract

The invention discloses a filling material applied to an underground permeable reactive barrier technology, and particularly relates to an iron-carbon composite solid acid material which is used as the filling material for removing chlorinated organic matters in the underground permeable reactive barrier technology. The carbon composite solid acid material provided by the invention has a good removal effect on pollution of organic matters in underground water. The method for removing water pollutants by using a single material in the traditional PRB is replaced, the service life is prolonged, and the removal efficiency is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of the application of in-situ permeable reactive barrier technology for removing organic pollutants in water, and particularly relates to a filling material applied to in-situ permeable reactive barrier technology (PRB) prepared from an iron-carbon composite solid acid material. Background Art

[0003] Organic pollution of groundwater not only destroys the water body ecosystem but also directly affects human health. Long-term drinking of groundwater polluted by organic pollutants may cause serious consequences such as cancer, nervous system diseases, reproductive problems, and chronic poisoning. For example, chlorinated organic compounds such as trichloroethylene and tetrachloroethylene have been listed as potential carcinogens by the World Health Organization (WHO), and long-term exposure may cause liver and kidney damage. In addition, the toxicity of organic pollutants may be transmitted in the food chain, causing a more profound impact on the ecological environment. The restoration of polluted groundwater is extremely difficult. Once pollution occurs, pollutants may remain in the aquifer for a long time and are difficult to degrade naturally. Therefore, the adoption of efficient groundwater remediation technologies is the key to solving this environmental problem.

[0004] Traditional groundwater treatment methods such as Pump-and-Treat technology can control the spread of pollutants, but they are often costly, have a long treatment cycle, and are difficult to effectively remove deep-seated pollution. In contrast, in-situ permeable reactive barrier (PRB) technology has received extensive attention due to its high efficiency, economy, and sustainability. This technology constructs a permeable wall rich in reactive materials in the groundwater flow path, so that pollutants are removed when groundwater flows through the wall, thereby achieving the purpose of purifying groundwater.

[0005] An in-situ permeable reactive barrier filled with activated carbon and iron is a relatively mature remediation technology, which mainly utilizes the high adsorption capacity of activated carbon and the reduction and degradation effect of zero-valent iron to effectively remove organic pollutants in groundwater. Due to its large specific surface area and rich microporous structure, activated carbon can adsorb a variety of organic pollutants, such as chlorinated hydrocarbons, phenolic compounds, and polycyclic aromatic hydrocarbons, thereby reducing the migration and diffusion of pollutants in groundwater. At the same time, zero-valent iron can dechlorinate and degrade chlorinated organic pollutants into low-toxic or non-toxic substances through reduction reactions. For example, trichloroethylene can be reduced to ethylene or ethane. The combination of the two can significantly improve the removal efficiency of pollutants and reduce the secondary release of pollutants.

[0006] The advantages of the in-situ permeable reactive barrier (PRB) technology are not only reflected in its high efficiency in removing pollutants, but also include its long-term stable remediation effect and low maintenance cost. Compared with the traditional pumping and treatment method, this technology does not require continuous energy input, reduces operating costs, and can continuously conduct in-situ treatment of groundwater. Its passive remediation feature makes it particularly suitable for the treatment of long-term contaminated groundwater. Especially in cases where the pollution source is difficult to eliminate or the pollution range is wide, the in-situ permeable reactive barrier can serve as an effective prevention and control measure to reduce the spread of groundwater pollution.

[0007] In practical applications, the design of the in-situ permeable reactive barrier needs to comprehensively consider the hydraulic conditions of groundwater, pollutant types, pollution range, as well as the selection and filling method of reactive materials. Different polluted sites may require different material combinations to optimize the removal effect. For example, for chlorinated hydrocarbon pollution, a filling method combining zero-valent iron and activated carbon can be adopted, while for aromatic compound or phenolic pollution, biodegradable materials or oxidants can be added to enhance the removal ability. In addition, the long-term effectiveness of this technology and possible clogging problems are also important considerations in engineering design and operation management, and regular monitoring and maintenance are required.

[0008] In recent years, the in-situ permeable reactive barrier technology has been widely applied worldwide and has achieved remarkable results in the field of groundwater remediation. In North America, Europe, and some parts of China, this technology has been successfully applied to remediate groundwater contaminated by chlorinated hydrocarbons, polycyclic aromatic hydrocarbons, pesticides, and heavy metals. With the increasingly strict environmental protection regulations and the growing public concern about water resource security, this technology will still play an important role in the future and will continue to develop and optimize to meet a wider range of pollution remediation needs.

[0009] In summary, groundwater organic pollution has become a global environmental problem, seriously affecting the stability of the ecosystem and human health. Traditional treatment technologies have limitations such as high cost and low efficiency, while the in-situ permeable reactive barrier technology, as an efficient, economical, and sustainable groundwater remediation method, provides new possibilities for solving organic pollution problems. Through reasonable design and optimized material selection, this technology can effectively purify groundwater during long-term operation, ensure water resource security, and provide strong support for human health and ecological environmental protection.

[0010] However, most traditional PRB technologies use single materials. During the use of a single reaction medium, problems such as deactivation and clogging will occur, and the wall life is relatively short. The filling of composite materials can not only overcome the above problems, but also greatly improve the removal efficiency. Summary of the Invention

[0011] Object of the Invention: The technical problem to be solved by the present invention is to provide a filling material applied to the in-situ permeable reactive barrier technology in view of the deficiencies of the prior art.

[0012] To solve the above technical problems, the present invention discloses the following technical solutions:

[0013] In a first aspect, the present invention discloses an iron-carbon composite solid acid material.

[0014] In some embodiments, the iron-carbon composite solid acid material is made of activated carbon, solid acid, and zero-valent iron.

[0015] Among them, the solid acid is a molecular sieve solid acid, such as H-Y type molecular sieve solid acid and H-β molecular sieve solid acid.

[0016] Among them, in the H-Y type molecular sieve solid acid, the molar ratio of SiO 2 and Al 2 O 3 is 5.1 - 100, such as HY40, HY60, HY80, HY100, HY5.1(0.8), HY5.1(3.0). The 40 in HY40 represents that the molar ratio of SiO 2 and Al 2 O 3 is 40; the 60 in HY60 represents that the molar ratio of SiO 2 and Al 2 O 3 is 60; the 80 in HY80 represents that the molar ratio of SiO 2 and Al 2 O 3 is 80; the 100 in HY100 represents that the molar ratio of SiO 2 and Al 2 O 3 is 100. In the H-Y molecular sieve solid acid, when the molar ratio of SiO 2 and Al 2 O 3 is 5.1, the H-Y molecular sieve solid acid further contains 0.8%wt - 3.0%wt of Na 2 O, such as 5.1 in HY5.1(0.8) represents that the molar ratio of SiO 2 and Al 2 O 3 is 5.1, and 0.8%wt of Na 2 O is added; 5.1 in HY5.1(3.0) represents that the molar ratio of SiO 2 and Al 2 O 3 is 5.1, and 3%wt of Na 2 O is added.

[0017] Among them, in the H-β molecular sieve solid acid, the molar ratio of SiO 2 and Al2 O 3 The molar ratio of 25 - 40, such as Beta25, Beta30, Beta40, where 25 in Beta25 represents SiO 2 and Al 2 O 3 The molar ratio is 25; 30 in Beta30 represents SiO 2 and Al 2 O 3 The molar ratio is 30; 40 in Beta40 represents SiO 2 and Al 2 O 3 The molar ratio is 40.

[0018] Among them, the mass ratio of the activated carbon, solid acid and zero-valent iron is 2 - 4:0.5 - 5:1, preferably 3:1 - 4:1, such as 3:4:1; 3:3:1; 3:1:1, preferably 3:3:1. In some embodiments, the mass range of the activated carbon is 1.5 - 3 g, the mass range of the solid acid is 0.5 - 4 g, and the mass range of the iron is 0.5 - 1 g. For example, the mass of the activated carbon is 1.5 g, the mass of the solid acid is 1.5 g, and the mass of the iron is 0.5 g.

[0019] Among them, the pore size range of the activated carbon is 100 mesh.

[0020] Among them, the zero-valent iron is iron powder, and the pore size range of the iron powder is 200 mesh.

[0021] Among them, the activated carbon, solid acid and zero-valent iron are made by ball milling, such as ball milling for 4 - 8 h, such as ball milling for 6 h.

[0022] In a second aspect, the present invention discloses the application of the iron-carbon composite solid acid material described in the first aspect above in removing chlorinated organic compounds.

[0023] In some embodiments, the chlorinated organic compounds include trichloroethylene (TCE), tetrachloroethylene (PCE), dichloroethylenes (DCEs), chloroform, and chlorobenzene. Among them, the chlorobenzene includes 1,4-dichlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene.

[0024] In some embodiments, the iron-carbon composite solid acid material is used as a filling material in the in-situ permeable reactive barrier technology to remove chlorinated organic compounds; in some embodiments, the iron-carbon composite solid acid material, quartz sand and cotton are used together as a filling material in the in-situ permeable reactive barrier technology to remove chlorinated organic compounds.

[0025] Furthermore, the preparation method of the filling material is as follows:

[0026] (1) Weigh a certain mass of quartz sand and load it into the bottom of the plexiglass tube, then shake it evenly to serve as the fifth layer;

[0027] (2) Weigh a certain mass of cotton and load it into the plexiglass tube, covering the quartz sand. Then use a glass rod to press the cotton tightly to form the fourth layer;

[0028] (3) Weigh a certain mass of the iron-carbon composite solid acid material and load it into the plexiglass tube, covering the cotton, and shake it evenly to form the third layer;

[0029] (4) Weigh a certain mass of cotton and load it into the plexiglass tube, covering the iron-carbon composite solid acid material. Use a glass rod to press the cotton tightly to make the iron-carbon composite solid acid material more compact to form the second layer;

[0030] (5) Weigh a certain mass of quartz sand and load it into the plexiglass tube, then shake it evenly to serve as the first layer.

[0031] Among them, the thickness range of the quartz sand layer is 2 - 3 cm, the thickness range of the cotton layer is 1 - 2 cm, and the thickness range of the iron-carbon composite solid acid layer is 5 - 6 cm.

[0032] Among them, the pore size range of the quartz sand is 8 - 16 mesh.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention provides a new filling material for PRB - the iron-carbon composite solid acid, which can effectively remove trichloroethylene pollution in groundwater while reducing the iron content, and has a fast degradation rate.

[0035] (2) The filling material used in the method provided by the present invention has the advantages of being non-toxic, biodegradable, and low-cost; and the filled device has the advantages of high removal efficiency and high reuse rate.

[0036] (3) The method provided by the present invention uses the technology of the in-situ permeable reactive barrier, fills the composite material into the plexiglass tube, has a wide application environment, is not affected by the environment, and is suitable for the treatment of water pollution in industrial production. Description of the Drawings

[0037] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0038] Figure 1 It is the infrared spectrum diagram of different solid acids and the iron-carbon composite solid acid material made therefrom.

[0039] Figure 2 It is the electron microscope image of the iron-carbon composite solid acid material.

[0040] Figure 3 It is the infrared spectrum of the iron-carbon composite material.

[0041] Figure 4 It is the device diagram of the present invention. Specific implementation manners

[0042] According to the following embodiments, the present invention can be better understood. However, those skilled in the art can easily understand that the content described in the embodiments is only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0043] In the following embodiments, unless otherwise specified, the experimental methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be obtained from commercial channels.

[0044] In the following embodiments, the method for detecting trichloroethylene is to measure the concentration of TCE in the filtrate by a gas chromatography / mass spectrometry (GC-MS) equipped with a purge and trap injector with reference to the Chinese standard HJ 686-2014.

[0045] In the following embodiments, the calculation method of the space-time efficiency is as follows:

[0046] Space-time efficiency = (Cinitial - Cresidual) × flow rate / Veffective volume;

[0047] Wherein, Cinitial is the concentration of TCE in the pre-prepared TCE aqueous solution, Cresidual is the concentration of TCE in the sample after removal by the iron-carbon composite solid acid material, and Veffective volume is the volume of the iron-carbon composite solid acid material.

[0048] In the following embodiments, the calculation method of the trichloroethylene removal efficiency is as follows:

[0049] Removal efficiency = (Cinitial - Cresidual) / Cinitial × 100%;

[0050] Wherein, Cinitial is the concentration of TCE in the pre-prepared TCE aqueous solution, and Cresidual is the concentration of TCE in the sample after removal by the iron-carbon composite solid acid material.

[0051] In the following embodiments, unless otherwise specified, the iron material is 200-mesh iron powder (zero-valent iron).

[0052] Example 1: Preparation of nine iron-carbon composite solid acid materials with different ratios.

[0053] A series of solid acids, activated carbon, and iron materials were accurately weighed and ground and mixed evenly to prepare an iron-carbon composite solid acid material; the solid acids were Beta25, Beta30, Beta40, HY40, HY60, HY80, HY100, HY5.1(0.8) (briefly referred to as HY0.8), and HY5.1(3.0) (briefly referred to as HY3.0); in the iron-carbon composite solid acid material, the mass ratio of activated carbon, solid acid, and iron material was 3:4:1, 3:3:1, and 3:1:1; the specific process of grinding and mixing evenly was as follows: activated carbon, iron, and solid acid materials were weighed according to the mass ratio, ball-milled, an appropriate amount of the mixture was put into each small can, 20 small steel balls, 200 r / min, stopped for 10 min every half hour, rotated forward for 30 min and then rotated in the reverse direction for 30 min, and the total timing was 6 h to obtain the iron-carbon composite solid acid material.

[0054] The chemical bonds within a compound molecule are related to the specific vibrational energy that causes the component atoms to vibrate. Therefore, the absorption of electromagnetic energy at a specific frequency produces an infrared spectrum. The vibrational spectrum is a unique characteristic of the molecule, and the functional group properties of the compound can be identified and determined by comparing the previously recorded reference spectrum through Fourier transform infrared spectroscopy. As Figure 1 shown, materials with different ratios have absorption peaks of different intensities. From the infrared spectra of the iron-carbon composite solid acid materials (Beta type and HY type), the broad absorption peak appearing at 3735–3600 cm-1 belongs to the O–H stretching vibration on the surface and in the framework of the molecular sieve, mainly corresponding to acidic hydroxyl groups (such as Si–OH–Al) and isolated Si–OH; the absorption peak appearing at 1200–950 cm-1 belongs to the asymmetric stretching vibration peaks of Si–O–Si and Si–O–Al in the molecular sieve framework; 800–500 cm-1 belongs to the Si–O bending vibration, which can illustrate the stability of the three-dimensional framework of the molecular sieve. From the figure, this part of the absorption peak is relatively clear, indicating that the ball-milling mixing method did not damage the framework structure. The scanning electron microscope (SEM) of the iron-carbon composite solid acid material is as Figure 2 shown, and the iron-carbon composite solid acid material was successfully synthesized by the ball-milling mixing method, indicating that the activated carbon, solid acid, and iron materials were mixed evenly.

[0055] Example 2: Removal of trichloroethylene in water

[0056] Weigh 2 g of the iron-carbon composite solid acid material (prepared in Example 1) and transfer it to a brown glass bottle, and set up a control experiment. In the first group, no material was added. In the second group, 2 g of an iron-carbon mixture (the mass ratio of activated carbon to iron material was 3:1, and the infrared spectrum was as Figure 3 shown) was added. In the third group, 2 g of pure iron material was added.

[0057] Accurately pipette 70 mL of an aqueous solution of TCE with an initial concentration of 200 mg / L into a brown glass bottle, and place it in a constant temperature shaker (150 rpm, 25 °C) to shake well. Set the reaction time to 2 h. At the set time point, use a disposable syringe filter to filter the reaction solution through a 0.22 μm filter head, and transfer the filtrate to a brown injection vial to measure the TCE concentration in the filtrate.

[0058] As shown in Table 1 - Table 4, the iron-carbon mixture can remove TCE. Compared with the iron-carbon mixture, the iron-carbon composite solid acid can further improve the TCE removal efficiency. In addition, it can be seen that at the same time and concentration, when the mass ratio of activated carbon, solid acid, and iron material is 3:3:1, the removal efficiency is the highest, and it can be obtained that the ability of HY to remove TCE at this time is the best, up to 98.93%. Therefore, HY60 is selected for subsequent experiments.

[0059] Table 1 Removal of trichloroethylene in water in the control group experiment

[0060]

[0061] Table 2 Removal of trichloroethylene in water by nine iron-carbon composite solid acid materials at a ratio of 3:4:1

[0062]

[0063] Table 3 Removal of trichloroethylene in water by nine iron-carbon composite solid acid materials at a ratio of 3:3:1

[0064]

[0065]

[0066] Table 4 Removal of trichloroethylene in water by nine iron-carbon composite solid acid materials at a ratio of 3:1:1

[0067]

[0068] Example 3: Removal of trichloroethylene in water by filling an organic glass tube with an iron-carbon composite solid acid at different flow rates.

[0069] Weigh activated carbon, solid acid HY60, and iron material according to a mass ratio of 3:3:1 and carry out ball milling. Put an appropriate amount of the mixture, 20 small steel balls, into each small jar, rotate at 200 r / min, stop for 10 min every half hour, rotate forward for 30 min and then rotate in the reverse direction for 30 min, with a total timing of 6 h to obtain the iron-carbon composite solid acid material.

[0070] As Figure 4As shown in the figure, cotton - quartz sand - iron - carbon composite solid acid material - quartz sand - cotton are filled from bottom to top in the plexiglass tube. Among them, the iron - carbon composite solid acid material is 2 g, the quartz sand is 1 g each on the upper and lower parts, and the cotton is about 0.5 g each on the upper and lower parts.

[0071] The flow rate of the contaminated liquid is controlled by a peristaltic pump. The pre - configured TCE aqueous solution (200 mg / L) is introduced into the filled plexiglass tube, with the flow direction from bottom to top. The flow rate gradients are set as 0.2 ml / min, 0.5 ml / min, 0.8 ml / min, 1 ml / min, 2 ml / min, 3 ml / min, 5 ml / min, 7 ml / min, 9 ml / min. The TCE aqueous solution flows upward from the bottom of the plexiglass tube at a rate of 0.2 ml / min. After equilibrium, samples are taken from the outlet to detect the content of TCE in the samples; the flow rate is adjusted to 0.5 ml / min, and after equilibrium, samples are taken to detect the content of TCE in the samples; the flow rate is adjusted successively according to the aforementioned flow rates, and samples are taken for detection.

[0072] Samples taken at each flow rate are passed through a 0.22 - um organic filter membrane and then filled into test bottles to detect the content of trichloroethylene and calculate the space - time efficiency. As shown in Table 5, the degradation ability of the iron - carbon composite solid acid at different flow rates is considerable. The lower the flow rate, the longer the residence time of the TCE aqueous solution passing through the iron - carbon composite solid acid, so the lower the concentration of trichloroethylene in the samples taken from the outlet. From the perspective of the removal efficiency, the removal efficiency can reach 98.89% at 2 ml / min, which is almost the same as the treatment effect at the lowest flow rate, and the space - time efficiency is also as high as 83.987 mg / (L min).

[0073] Table 5 Removal of trichloroethylene in water by iron - carbon composite solid acid material at different flow rates

[0074]

[0075] Example 4: Removal of trichloroethylene in water by filling the plexiglass tube with iron - carbon composite solid acid under different time gradients.

[0076] In the plexiglass tube, cotton - quartz sand - iron - carbon composite solid acid material (prepared in Example 3) - quartz sand - cotton are filled from bottom to top. Among them, the iron - carbon composite solid acid material is 2 g, the quartz sand is 1 g each on the upper and lower parts, and the cotton is about 0.5 g each on the upper and lower parts.

[0077] The flow rate of the contaminated liquid is controlled by a peristaltic pump to be 2 ml / min. The pre - configured TCE aqueous solution (200 mg / L) is introduced into the filled plexiglass tube, with the flow direction from bottom to top. The sampling times are set as 0.5 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, 7 h, 9 h, 10 h, 12 h, 24 h, 30 h, 2 days, 5 days, 10 days, 20 days, 30 days.

[0078] For each time gradient, the sample is taken and filtered through a 0.22-μm organic filter membrane, then put into a detection bottle to detect the content of trichloroethylene, and the trichloroethylene removal efficiency is calculated. The results are shown in Table 6 and Table 7. Under the corresponding flow rate at this time, the outlet liquid concentration can be considered as the completely removed concentration within the detection time. The degradation of trichloroethylene is completed continuously within 30 days, and the performance does not decay, and the removal ability is extremely strong, with very high water treatment application value, fully qualitatively proving the effectiveness of the selected substance, laying a theoretical foundation and source of significance for subsequent experiments.

[0079] Table 6 Removal of trichloroethylene in water by iron-carbon composite solid acid material at different times

[0080]

[0081] Table 7 Removal of trichloroethylene in water by iron-carbon composite solid acid material at different days

[0082]

[0083]

[0084] The present invention provides a filling material applied to the technology of in-situ permeable reactive barrier (PRB), which is prepared from an iron-carbon composite solid acid material. The above-mentioned embodiments only represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An iron-carbon composite solid acid material, characterized in that: Made of activated carbon, solid acid and zero-valent iron.

2. The iron-carbon composite solid acid material according to claim 1, characterized in that: The solid acid is a molecular sieve solid acid.

3. The iron-carbon composite solid acid material according to claim 1, characterized in that: The solid acid is HY molecular sieve solid acid or H-β molecular sieve solid acid.

4. The iron-carbon composite solid acid material according to claim 3, characterized in that: The molar ratio of SiO2 to Al2O3 in the HY molecular sieve solid acid is 5.1-100; the molar ratio of SiO2 to Al2O3 in the H-β molecular sieve solid acid is 25-40.

5. The iron-carbon composite solid acid material according to claim 3, characterized in that: In the HY molecular sieve solid acid, when the molar ratio of SiO2 to Al2O3 is 5.1, the HY molecular sieve solid acid further contains 0.8%wt-3.0%wt Na2O.

6. The iron-carbon composite solid acid material according to any one of claims 1 to 5, characterized in that: The mass ratio of the activated carbon, the solid acid and the zero-valent iron is 2-4:0.5-5:1, preferably 3:1-4:1, preferably 3:3:

1.

7. The iron-carbon composite solid acid material according to claim 1, characterized in that: Activated carbon, solid acid and zero-valent iron are prepared by ball milling.

8. Use of the iron-carbon composite solid acid material according to any one of claims 1 to 7 in removing chlorinated organic matter.

9. The use according to claim 8, characterized in that: The iron-carbon composite solid acid material is used as a filling material in underground permeable reaction wall technology to remove chlorinated organic matter.

10. The use according to claim 8, characterized in that: The chlorinated organic substances include trichloroethylene, tetrachloroethylene, dichloroethylene, chloroform and chlorobenzene.

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