A permeable reactive wall filler and its preparation method and application

Abstract

The present invention provides a permeable reactive wall filler, its preparation method, and its application, relating to the field of in-situ groundwater remediation technology. The invention utilizes a solvothermal method to load (BiO)2CO3 onto the surface of coconut shell charcoal. This filler, used as a permeable reactive wall filler, not only has high iodine removal efficiency, is environmentally friendly and economical, and is simple to operate, but can also be implemented and applied in underground aquifers, enriching the practical application of high-iodine groundwater remediation.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater in-situ remediation, and in particular to a permeable reaction wall filler and a preparation method and application thereof. Background Art

[0002] As iodine deficiency and living conditions improve, the problem of excessive iodine intake has become increasingly prominent in some areas. The technical indicator for high-iodine areas in GB / T10380-2003, "Demarcation of Waterborne High-Iodine Areas and Endemic High-Iodine Goiter Areas," has been adjusted from "drinking water iodine content exceeding 150 μg / L" to "areas with a median iodine content in drinking water exceeding 100 μg / L are considered waterborne high-iodine areas."

[0003] Natively high-iodine groundwater puts some countries and regions around the world at risk of excessive iodine intake, particularly in arid and semi-arid regions where groundwater is the primary source of drinking water. Excessive iodine intake can affect thyroid function and increase the risk of hypertension and diabetes. Furthermore, iodine readily forms iodinated disinfection byproducts during drinking water disinfection, which are highly cytotoxic and genotoxic.

[0004] Currently, research on iodine-rich groundwater primarily focuses on developing iodine removal materials and improving methods using static batch adsorption experiments. The application scenarios are unclear, and actual remediation research and application are even rarer. Potentially applicable technologies for iodine-rich groundwater remediation include extraction and treatment, electrokinetic remediation, in-situ injection remediation, and permeable reactive barriers (PRBs).

[0005] The "wall" of the permeable reactive wall technology can be combined with various existing iodine ion removal methods to carry out in-situ remediation of high-iodine groundwater. Moreover, it does not involve the extraction of groundwater, avoiding the problems of traditional extraction-treatment technology, such as large groundwater pumping and treatment engineering consumption, high costs, and the need for regular maintenance and monitoring. Moreover, as an in-situ passive system that utilizes the effect of natural hydraulic gradients, it does not require external power. Compared with electric remediation technology, it can further reduce operation and maintenance costs, and can also effectively circumvent the transmission diffusion resistance and agent release problems of in-situ injection remediation technology. It is the most feasible and cost-effective in-situ remediation technology that may be applied to high-iodine groundwater remediation technology.

[0006] However, research on the application of permeable reactive wall technology in the remediation of high-iodine groundwater is limited. Realizing its application requires overcoming key challenges, such as selecting appropriate reactive fillers based on the specific characteristics of high-iodine groundwater, anticipating specific application scenarios, and determining the optimal application scenarios. Furthermore, existing PRB fillers generally exhibit a significant decrease in permeability after treating high-iodine groundwater, further limiting their application in this area.

[0007] Therefore, it is necessary to develop a PRB filler suitable for the treatment of high-iodine groundwater to achieve green, economical and efficient high-iodine groundwater remediation. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a permeable reaction wall filler. As a permeable reaction wall reaction filler, the filler not only has high iodine removal efficiency, is green and economical, and is easy to operate, but also can be carried out in underground aquifers for engineering practice and application promotion, enriching the practical application of high-iodine groundwater remediation.

[0009] The preparation method of the permeable reactive wall filler of the present invention comprises the following steps:

[0010] S1. Soak coconut shell charcoal in deionized water for 24 hours, filter, wash and dry;

[0011] S2, mixing Bi(NO3)3·5H2O, urea, and ethylene glycol to obtain a mixed solution, adding dried coconut shell charcoal to the mixed solution and stirring uniformly;

[0012] S3, transferring the stirred mixture into a stainless steel reactor with a polytetrafluoroethylene liner for reaction;

[0013] S4. After the reaction is completed, the reactants are cooled to room temperature, the solid phase is fully washed with pure water and then dried to obtain a permeable reaction wall filler.

[0014] Furthermore, the drying temperature is 60° C. and the drying time is 12 hours.

[0015] Furthermore, the molar ratio of Bi(NO3)3·5H2O to urea is 1:10.

[0016] Furthermore, the concentration of Bi(NO3)3·5H2O in the mixed solution is 0.05M.

[0017] Furthermore, the added amount of the dried coconut shell charcoal is (0.0125-0.1) g / mL.

[0018] Furthermore, the reaction temperature is 150° C. and the reaction time is 12 h.

[0019] Furthermore, the drying temperature is 60° C. and the drying time is 12 hours.

[0020] The present invention also provides a bismuth-based permeable reactive wall filler prepared according to the above method.

[0021] Another object of the present invention is to provide a method for applying the bismuth-based permeable reactive wall filler, wherein the method comprises:

[0022] The quartz sand is soaked in deionized water for 24 hours, filtered, washed and dried, and the washed quartz sand and the permeable reaction wall filler are used to fill the PRB column reactor. The high-iodine groundwater is pumped into the PRB column reactor to perform deiodination treatment of the high-iodine groundwater.

[0023] Furthermore, the drying temperature is 60° C. and the drying time is 12 hours.

[0024] Furthermore, the particle size of the quartz sand is 40-70 mesh.

[0025] Furthermore, the PRB column reactor is made of acrylic, and the specifications of the PRB column reactor are: height 150 mm, inner diameter 30 mm, and total volume 106 mL.

[0026] Furthermore, the PRB column reactor is provided with a water outlet and a water inlet at the top and bottom, respectively. The materials filled from the water inlet to the water outlet are 10 cm of quartz sand, 2 cm of bismuth-based permeable reaction wall filler, and 3 cm of quartz sand.

[0027] Furthermore, a peristaltic pump was used to connect the water inlet at the bottom of the PRB column reactor to the input bottle of high-iodine groundwater, and the water outlet of the column reactor was connected to the outflow bottle. The peristaltic pump was turned on to pump the high-iodine groundwater into the PRB column reactor for deiodination treatment.

[0028] The technical principles involved in the deiodination treatment of high-iodine groundwater of the present invention are as follows:

[0029]

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The invention utilizes a solvent thermal method to load (BiO)2CO3 onto the surface of coconut shell charcoal, thereby reducing the preparation cost of the filler and greatly improving the removal rate of the filler for iodide ions.

[0032] The bismuth-based permeable reactive wall filler of the present invention removes iodide ions in high-iodine groundwater by adsorption, with a removal rate of up to 99.99%. No bismuth is leached during the adsorption process, and no secondary pollution problem is caused.

[0033] After the PRB column reactor using the filler of the present invention treats high-iodine groundwater, the permeability is not affected, thus overcoming the problem of reduced permeability of the filler in the permeable reaction wall technology.

[0034] The high-iodine groundwater treatment method provided by the present invention can be expanded and applied to the in-situ remediation of high-iodine groundwater in underground aquifers. According to the water flow field characteristics of the regional high-iodine groundwater, a bismuth-based permeable reaction wall filler is established as a permeable reaction wall with a reaction filler in the form of well filling and continuous trenching. Under the action of the natural hydraulic gradient, the high-iodine groundwater flowing through is efficiently treated, providing a new and feasible design idea for the in-situ remediation of high-iodine groundwater. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Figure 1 This is a schematic structural diagram of the in-situ remediation device for high-iodine groundwater according to the present invention;

[0037] Figure 2 This is a schematic diagram of the principle of in-situ remediation of high-iodine groundwater according to the present invention;

[0038] Explanation of the accompanying symbols: 1-acrylic column reactor, 2-bismuth-based permeable reaction wall filler, 3-quartz sand, 4-acrylic raising platform. DETAILED DESCRIPTION

[0039] The technical solution provided by the present invention is further described below in conjunction with embodiments.

[0040] Example 1

[0041] Place coconut shell charcoal and quartz sand in two clean large beakers respectively, add deionized water to cover the solid phase by 2-3 cm, stir thoroughly and seal with sealing film, soak for 24 hours and then discard the liquid phase, rinse with deionized water three times and dry in an oven at 60℃ for 12 hours;

[0042] Then, the pretreated coconut shell charcoal was used to prepare a bismuth-based permeable reaction wall filler: 0.97g Bi(NO3)3·5H2O and 1.2g CH4N2O were weighed and added to a 100mL beaker, followed by 40mL (CH2OH)2 being poured into the beaker, and finally 1g of pretreated coconut shell charcoal was added and stirred thoroughly. After stirring evenly, the mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner, placed in an oven at 150°C for 12h, cooled to room temperature, and the solid phase was thoroughly washed with pure water and then dried to obtain the desired bismuth-based permeable reaction wall filler.

[0043] The washed 70-mesh quartz sand and the prepared bismuth-based permeable reaction wall filler were then loaded into the PRB column reactor. The PRB column reactor was made of acrylic, with a height of 150 mm, an inner diameter of 30 mm, and a total volume of 106 mL. A water outlet and a water inlet were provided at the top and bottom, respectively. The materials filled from the water inlet to the water outlet were quartz sand (10 cm), bismuth-based permeable reaction wall filler (2 cm), and quartz sand (3 cm), respectively. After filling, the PRB column reactor was wrapped with aluminum foil to simulate the dark environment of groundwater.

[0044] Use a peristaltic pump to connect the water inlet at the bottom of the PRB column reactor to the input bottle of high-iodine groundwater, and the water outlet of the column reactor to the outflow bottle. Turn on the peristaltic pump and pump the high-iodine groundwater with an iodine concentration of 2 mg / L into the PRB column reactor in an upward flow at a flow rate of 4 mL / min. This allows the high-iodine groundwater to react with the surface-loaded (BiO)2CO3, completing the deiodination treatment by adsorption.

[0045] After penetration, the iodine and bismuth concentrations in the effluent were both below the detection limits of an inductively coupled plasma mass spectrometer (0.2 μg / L for iodine and 0.03 μg / L for bismuth), meeting the requirements of the National Standard for Drinking Water Quality (GB5749-2022). The iodine ion removal rate reached 99.99%, with virtually no leaching of bismuth and no secondary contamination. The permeability of the PRB column reactor was unaffected after deiodination treatment.

[0046] Example 2

[0047] Same as Example 1, except that the particle size of the quartz sand is 40 mesh.

[0048] After penetration, the iodine and bismuth concentrations in the effluent were both below the detection limits of inductively coupled plasma mass spectrometry (0.2 μg / L for iodine and 0.03 μg / L for bismuth), meeting the requirements of the National Standard for Drinking Water Quality (GB5749-2022). The iodine ion removal rate reached 99.99%, with virtually no leaching of bismuth and no secondary contamination. The permeability of the PRB column reactor was unaffected after deiodination treatment.

[0049] Example 3

[0050] Same as Example 1, except that the pump flow rate is set to 8 mL / min.

[0051] After penetration, the iodine and bismuth concentrations in the effluent were both below the detection limits of inductively coupled plasma mass spectrometry (0.2 μg / L for iodine and 0.03 μg / L for bismuth), meeting the requirements of the National Standard for Drinking Water Quality (GB5749-2022). The iodine ion removal rate reached 99.99%, with virtually no leaching of bismuth and no secondary contamination. The permeability of the PRB column reactor was unaffected after deiodination treatment.

[0052] Comparative Example 1

[0053] The same as Example 1, except that: in the preparation process of the permeable reactive wall filler, only pre-treated coconut shell charcoal without bismuth-based modification is used.

[0054] After penetration, the iodine concentration in the effluent was 642.8 μg / L, and the iodine ion removal rate was 67.5%.

[0055] Comparative Example 2

[0056] The same as Example 1, except that: during the preparation of the permeable reactive wall filler, only pretreated coconut shell charcoal was used, and the pump flow rate was set to 8 mL / min.

[0057] After penetration, the iodine concentration in the effluent was 1154.5 μg / L, and the iodine ion removal rate was 41.66%.

[0058] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for preparing a permeable reactive wall filler, characterized in that: The following steps are involved: S1. Soak coconut shell charcoal in deionized water for 24 h, filter, wash and dry; S2. Mix Bi(NO3)3•5H2O, urea, and ethylene glycol to obtain a mixed solution, add dried coconut shell charcoal to the mixed solution, and stir evenly; S3, transferring the stirred mixture into a stainless steel reactor with a polytetrafluoroethylene liner for reaction; S4. After the reaction is completed, the reactants are cooled to room temperature, the solid phase is fully washed with pure water and then dried to obtain a permeable reaction wall filler; The drying temperature is 60°C and the drying time is 12 h; The molar ratio of Bi(NO3)3•5H2O to urea is 1:10; The concentration of Bi(NO3)3•5H2O in the mixed solution is 0.05M; The added amount of the dried coconut shell charcoal is (0.0125-0.1) g / mL; The reaction temperature is 150° C. and the reaction time is 12 h.

2. A bismuth-based permeable reactive wall filler, characterized in that: Prepared by the method of claim 1.

3. The use of the bismuth-based permeable reactive wall filler according to claim 2, characterized in that: Here’s how: The quartz sand is soaked in deionized water for 24 hours, filtered, washed and dried, and the washed quartz sand and the permeable reaction wall filler are used to fill the PRB column reactor. The high-iodine groundwater is pumped into the PRB column reactor to perform deiodination treatment of the high-iodine groundwater.

4. The use according to claim 3, characterized in that The PRB column reactor is made of acrylic, and the specifications of the PRB column reactor are: height 150 mm, inner diameter 30 mm, and total volume 106 mL.

5. The use according to claim 3, characterized in that The PRB column reactor is provided with a water outlet and a water inlet at the top and bottom, respectively. The materials filled from the water inlet to the water outlet are 10 cm of quartz sand, 2 cm of bismuth-based permeable reaction wall filler, and 3 cm of quartz sand.

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