A method for long-term remediation of groundwater contaminated by o-phenylenediamine using amphiphilic covalent organic polymers

Abstract

A method for long-term remediation of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer belongs to the technical field of site pollution control; the method comprises the following steps: step 1, preparation of a remediation agent, step 2, in-situ injection of the amphiphilic covalent organic polymer for long-term remediation of groundwater contaminated by o-phenylenediamine; the remediation agent of the present invention has a high OPD adsorption capacity, a rapid and simple synthesis process, and is suitable for large-scale production; the method is green and environmentally friendly, simple to operate, and low in cost, and can achieve long-lasting, rapid, and thorough treatment of aniline pollutants; the remediation agent prepared by the present invention has a low carbon footprint, further demonstrating its green sustainability in the remediation of OPD-contaminated groundwater.

Description

Technical Field

[0001] The invention belongs to the technical field of site pollution control, and in particular relates to a method for long-term repair of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer. Background Art

[0002] O-phenylenediamine (OPD), a typical aniline compound, is widely used in the dye and pesticide industries and is discharged into water bodies through industrial wastewater and agricultural water. OPD residues in water bodies pose a growing threat to human health and the ecological environment due to their bioaccumulation, persistence, and potential carcinogenicity. Furthermore, studies have shown that OPD is easily adsorbed by organic matter on porous media surfaces. Therefore, the development of efficient remediation methods for OPD-contaminated groundwater is urgent.

[0003] Traditional extraction and treatment technologies often fail to achieve ideal results due to the strong capillary force of aquifers and low mass transfer efficiency. In contrast, in-situ injection technology can achieve remediation in a relatively short period of time and in an efficient manner by injecting remediation agents directly into the aquifer. Although surfactants are widely used in in-situ remediation to alleviate the tailing-rebound phenomenon of pollutants, the large doses and high concentrations required to achieve ultra-low interfacial tension often lead to instability in the remediation process, increasing the difficulty of separating the agent from the pollutant after remediation. In contrast, adsorbents do not require large amounts of organic solvents or complex operating steps, and are an environmentally friendly and efficient solution for controlling OPD pollution in groundwater.

[0004] Covalent organic polymers (COPs) are an emerging class of porous materials assembled through strong covalent bonds. They possess a multi-level pore structure, abundant active sites, controllable synthesis technology, and excellent chemical stability, showing great potential in the field of adsorption. However, current COPs designs are mostly limited to two-component condensation systems, which to some extent limits their structural diversity and production efficiency. In addition, existing COPs are generally hydrophilic and are mainly used for gas adsorption or antibiotic adsorption, making them difficult to adapt to the remediation needs of aniline pollutants. They also have poor dispersion stability in aqueous phases and limited transport capacity, which weakens their application in complex formations. Therefore, the development of amphiphilic materials with both particle and surfactant properties has become an urgent need in current technology.

[0005] Despite their considerable potential for various applications, COPs are currently synthesized only on a laboratory scale. Before scaling up to pilot-scale production, the environmental burden of their synthesis must be assessed. In this context, life cycle assessment (LCA) can demonstrate and quantify the environmental impacts associated with material production. Therefore, comprehensive LCA studies of COP production, encompassing raw material extraction, manufacturing, use, disposal / recycling / reuse, and other aspects, are crucial. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the existing repair of o-phenylenediamine contaminated groundwater and provide a method for long-term repair of o-phenylenediamine contaminated groundwater using an amphiphilic covalent organic polymer.

[0007] A method for long-term remediation of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer comprises the following steps:

[0008] Step 1: Preparation of repair agent:

[0009] 1.1 Dissolve 0.20 mmol of benzene-1,3,5-trihydrazide, 0.30 mmol of 4,4'-diaminobiphenyl-3,3'-disulfonic acid, 0.06 mmol of 4-n-butylaniline, and 0.60 mmol of terephthalaldehyde in 5 mL of dimethyl sulfoxide (DMSO) and heat at 100°C for 30 minutes. After obtaining the reaction product, dialyze it against distilled water to remove the organic solvent, and then freeze-dry the product at -40°C to obtain an amphiphilic covalent organic polymer material.

[0010] 1.2 Weigh the amphiphilic covalent organic polymer obtained in step 1.1 and dissolve it in water. Ultrasonicate for more than 15 minutes to ensure that the material is evenly dispersed in the aqueous solution to obtain a repair agent.

[0011] Step 2: In-situ injection of amphiphilic covalent organic polymer for long-term remediation of o-phenylenediamine contaminated groundwater:

[0012] 2.1 In areas near groundwater pollution sources, several injection wells should be installed upstream of the groundwater flow, perpendicular to the groundwater flow direction. Several extraction wells should be installed downstream of the injection wells, at the edge of the pollution plume. Monitoring wells should be installed every 3-5 meters downstream of the injection wells. The depth of the injection wells, extraction wells, and monitoring wells should all reach the bottom of the aquifer.

[0013] 2.2 The concentration of the remediation agent is determined according to the formation conditions. The remediation agent is injected at a preset concentration using a pressure pulse device. When the remediation agent migrates to the extraction well, the extraction pump is activated to form a hydraulic gradient, achieving directional migration of the remediation agent and the formation of an adsorption reaction zone. The bottom section of the injection well and the section of the aeration zone are sealed, and water outlet holes are evenly distributed in the aquifer section.

[0014] 2.3 Monitor the OPD concentration in real time during the injection process and stop the injection when the desired effect is achieved.

[0015] Preferably, the concentration of the OPD is no greater than 20 mg / L; 0.1-0.3 g of the covalent organic polymer is uniformly dispersed in 1 L of distilled water to prepare a repair agent; the injection flow rate is controlled by a peristaltic pump in the range of 1.59-3.18 cm / min, and the formation medium is a coarse sand medium of 0.5-1.0 mm.

[0016] The working process and working principle of the present invention:

[0017] The extended alkyl chain and aromatic chain in the amphiphilic covalent organic polymer prepared in step 1 impart hydrophobicity to one side, while the other side remains hydrophilic due to the presence of amide chains and sulfonic acid groups. It possesses both hydrophilic and lipophilic amphiphilic properties, providing more possibilities for the application of COPs in aquifers.

[0018] Life cycle assessment (LCA) of remediation agents:

[0019] The LCA boundary encompasses the steps from commercial monomer production to the preparation of remediation agents, with the functional unit being 1.0 kg of remediation agent. The terrestrial acidification potential (TAP), global warming potential (GWP), terrestrial ecotoxicity potential (TETP), freshwater eutrophication potential (FEP), human toxicity potential (HTP), particulate matter formation potential (PMFP), and water depletion potential (WCP) were selected, quantified, and analyzed in detail.

[0020] Beneficial effects of the present invention:

[0021] 1. Traditionally, the remediation of aniline-contaminated aquifers is typically achieved through the injection of surfactants (such as Tween 80). However, this method requires high concentrations of surfactants, which can chemically interfere with the aquifer and results in low removal efficiency. The in-situ injection method proposed in this paper utilizes an amphiphilic covalent organic polymer for long-term remediation of o-phenylenediamine-contaminated groundwater, overcoming the high concentration requirements and low efficiency of traditional surfactants. This polymer possesses both particle activity and surfactant functionality, demonstrating excellent competitive adsorption capacity and achieving a pollutant removal rate exceeding 80%. Furthermore, by regulating the flow field through an injection-extraction mode to create a hydraulic gradient, the directional migration of the remediation agent can be significantly enhanced, enabling further filtration, separation, and recycling of the agent.

[0022] 2. The remediation agent of the present invention has a highly efficient OPD adsorption capacity, a fast and simple synthesis process, and is suitable for large-scale production. The method is environmentally friendly, simple to operate, and low-cost, and can achieve a long-lasting, rapid, and thorough treatment of aniline pollutants.

[0023] 3. The remediation agent prepared by the present invention has a low carbon footprint, further proving its green sustainability in the remediation of OPD-contaminated groundwater. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Comparison of the competitive adsorption capacity between the amphiphilic covalent organic polymer repair agent prepared in the present invention and Tween 80;

[0025] Figure 2A schematic diagram of a simulation column according to an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the OPD breakthrough curve when 0.1 g / L of the repair agent is used to repair 20 mg / L of OPD at an injection flow rate of 3.18 cm / min;

[0027] Figure 4 Schematic diagram of the OPD breakthrough curve when 0.3 g / L of the remediation agent is used to remediate 20 mg / L of OPD at an injection flow rate of 3.18 cm / min;

[0028] Figure 5 A schematic diagram of a two-dimensional simulation tank according to an embodiment of the present invention;

[0029] Figure 6 The removal effect of 0.1 g / L remediation agent on 10 mg / L OPD in a two-dimensional simulation tank.

[0030] 1 Quartz sand simulation column; 2 Water inlet; 3 Water outlet; 4 Peristaltic pump; 5 Water distribution plate; 6 Two-dimensional organic simulation tank; 61 Simulation tank water inlet; 62 Simulation tank water outlet; 63 Simulation tank peristaltic pump; 64 Simulation tank water distribution plate; 65 Simulation tank water injection well; 66 Sand box; 67 Sampling port. DETAILED DESCRIPTION

[0031] See also Figures 1 to 6 Shown is an embodiment of the present invention. Example 1

[0032] A method for long-term remediation of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer comprises the following steps:

[0033] Step 1: Preparation of repair agent:

[0034] 1.1 Dissolve 0.20 mmol of benzene-1,3,5-trihydrazide, 0.30 mmol of 4,4'-diaminobiphenyl-3,3'-disulfonic acid, 0.06 mmol of 4-n-butylaniline, and 0.60 mmol of terephthalaldehyde in 5 mL of dimethyl sulfoxide (DMSO) and heat at 100°C for 30 minutes. After obtaining the reaction product, dialyze it against distilled water to remove the organic solvent, and then freeze-dry the product at -40°C to obtain an amphiphilic covalent organic polymer material.

[0035] 1.2 Weigh 0.1-0.3 g of the amphiphilic covalent organic polymer obtained in step 1.1 and disperse it evenly in 1 L of distilled water. Ultrasonicate for at least 15 minutes to ensure that the material is evenly dispersed in the aqueous solution to obtain the repair agent.

[0036] Step 2: In-situ injection of amphiphilic covalent organic polymer for long-term remediation of o-phenylenediamine contaminated groundwater:

[0037] 2.1 In areas near groundwater pollution sources, several injection wells should be installed upstream of the groundwater flow, perpendicular to the groundwater flow direction. Several extraction wells should be installed downstream of the injection wells, at the edge of the pollution plume. Monitoring wells should be installed every 3-5 meters downstream of the injection wells. The depth of the injection wells, extraction wells, and monitoring wells should all reach the bottom of the aquifer.

[0038] 2.2 The concentration of the repair agent is determined according to the formation conditions. The repair agent of the preset concentration is injected using a pressure pulse device. When the repair agent migrates to the extraction well, the extraction pump is started to form a hydraulic gradient, achieving directional migration of the repair agent and the formation of an adsorption reaction zone. The bottom section of the injection well and the section of the aeration zone are closed, and water outlet holes are evenly arranged in the aquifer section. The injection flow rate is controlled by a peristaltic pump in the range of 1.59-3.18 cm / min. The formation medium is a coarse sand medium with a thickness of 0.5-1.0 mm.

[0039] 2.3 Monitor the OPD concentration in real time during the injection process. The OPD concentration should not exceed 20 mg / L. Stop the injection when the desired effect is achieved. Example 2

[0040] In order to simulate the saturated conditions of the underground aquifer, the experiment in this example set the soil-water ratio to 1:2. 5.0 g of sand was mixed with 10.0 mL of an OPD solution with a concentration of 1.0 g / L in six centrifuge tubes and shaken at 25 ° C for 24 hours to ensure that the system reached equilibrium. After draining the liquid sample from the centrifuge tube, the solid phase sample was rinsed with 10.0 mL of distilled water and shaken again for 24 hours to remove residual OPD. Subsequently, 50.0 mL of a remediation agent with a concentration of 1.0 g / L was added to three centrifuge tubes, and Tween 80 solution of the same concentration was added to the other three centrifuge tubes, and the shaking continued for 24 hours to compare the OPD removal effects of the two. Figure 1 This is a comparison chart of the competitive adsorption amount of residual OPD on the medium surface between the repair agent and Tween 80. Example 3

[0041] like Figure 2 As shown in the figure, a quartz sand simulation column 1 with an inner diameter of 2 cm and a height of 20 cm and a filling particle size of 0.5-1 mm is established. The water inlet 2 and the water outlet 3 are respectively set at the bottom and top of the quartz sand simulation column 1, and the flow rate is controlled by a peristaltic pump 4.

[0042] The contaminated sample solution was prepared by dissolving 20 mg of OPD in 1 L of distilled water. The remediation agent was then prepared by dispersing 0.1 g of an amphiphilic covalent organic polymer in 1 L of distilled water. The organic glass column was first saturated with water. In the first stage, 5 PV of the prepared 20 mg / L OPD sample solution was injected at 1 mL / min. In the second stage, 18 PV of distilled water was injected at 1 mL / min. In the third stage, 29 PV of the prepared 0.1 g / L remediation agent was injected at 3.18 cm / min. In the fourth stage, 7 PV of distilled water was injected at 3.18 cm / min.

[0043] like Figure 3 As shown, after the second stage, no OPD was detected in the effluent. In the third stage, the remediation agent migrated in the direction of the water flow and, through competitive adsorption, desorbed some OPD from the aquifer surface onto the remediation agent. As the remediation agent migrated to outlet 3, the total recovery rate of OPD in the effluent reached 84.98%. This shows that the remediation agent in the system can effectively remove OPD from the aquifer. Example 4

[0044] The contaminated sample solution was prepared by dissolving 20 mg of OPD in 1 L of distilled water. The remediation agent was then prepared by dispersing 0.3 g of an amphiphilic multicomponent covalent organic polymer in 1 L of distilled water. The organic glass column was first saturated with water. In the first stage, 5 PV of the prepared 20 mg / L OPD sample solution was injected at 1 mL / min. In the second stage, 18 PV of distilled water was injected at 1 mL / min. In the third stage, 29 PV of the prepared 0.3 g / L remediation agent was injected at 3.18 cm / min. In the fourth stage, 7 PV of distilled water was injected at 3.18 cm / min.

[0045] like Figure 4 As shown, after the second stage, no OPD was detected in the effluent. In the third stage, the remediation agent migrated in the direction of the water flow and, through competitive adsorption, desorbed some OPD from the aquifer surface onto the agent's surface. As the agent migrated to the outlet, the total recovery rate of OPD in the effluent reached 88.48%. This indicates that the remediation agent in the system effectively removed OPD from the aquifer. Example 5

[0046] like Figure 5As shown, a two-dimensional organic simulation tank 6 measuring 30 cm long, 2 cm wide, and 22 cm high was constructed. The filling medium was 0.5-1 mm quartz sand. A sandbox 66 was located in the middle of the two-dimensional organic simulation tank 6. The water inlet 61 and outlet 62 were located at the bottom on the left side and top on the right side of the two-dimensional organic simulation tank 6, respectively. A peristaltic pump 63 was used to control the flow rate. A water injection well 65 with an inner diameter of 2 cm and a height of 37 cm was located 11 cm from the left side of the simulation tank water distribution plate 64. The bottom of the well was sealed. The sandbox 66 was equipped with 20 sampling ports 67 for sample collection.

[0047] The contaminated sample solution was prepared by dissolving 10 mg of OPD in 1 L of distilled water. The remediation agent was prepared by dispersing 0.1 g of an amphiphilic covalent organic polymer in 1 L of distilled water. A 10 mg / L OPD solution was continuously injected at a flow rate of 0.25 m / d. Based on preliminary experiments, 1 L of the remediation agent was injected into the simulated tank injection well 65 at a pulse rate of 59 mL / min. Figure 6 As shown, when the remediation agent was injected, the OPD concentration was uniformly distributed at 10.0 mg / L. One hour after injection, the OPD content at both the proximal and distal ends of the simulated tank injection well 65 decreased significantly due to the dilution and adsorption effects of the remediation agent. With continued injection, the OPD concentration in the direction of groundwater flow gradually decreased. The remediation agent was able to effectively remediate the entire OPD-contaminated aquifer within 24 hours. Affected by the competition of coexisting ions in actual groundwater, the adsorption capacity of the adsorbent for OPD was 76.96 mg / g. After 48 hours, the downstream OPD concentration exceeded 5.0 mg / L, indicating that the remediation agent began to gradually lose its effectiveness in the aquifer. Example 6

[0048] A 1 kg remediation agent was prepared and its impacts were quantified and compared across the following categories: terrestrial acidification potential (TAP), global warming potential (GWP), terrestrial ecotoxicity potential (TETP), freshwater eutrophication potential (FEP), human toxicity potential (HTP), particulate matter formation potential (PMFP), and water depletion potential (WCP). The environmental impact results showed that 1.00 kg of SLEL-4 could adsorb 0.383 kg of OPD over five cycles, thereby avoiding the HTP impact of 0.047 kg of 1,4-DCB-eq. The GWP impact of the remediation agent was quantitatively calculated to be 12.32 kg of CO2-eq. From an environmental perspective, the remediation agent has the potential to be green and environmentally friendly.

Claims

1. A method for long-term remediation of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer, characterized by: The steps include: Step 1: Preparation of repair agent: 1.1 Dissolve 0.20 mmol of benzene-1,3,5-trihydrazide, 0.30 mmol of 4,4'-diaminobiphenyl-3,3'-disulfonic acid, 0.06 mmol of 4-n-butylaniline, and 0.60 mmol of terephthalaldehyde in 5 mL of dimethyl sulfoxide (DMSO) solvent and heat at 100°C for 30 minutes. After obtaining the reaction product, dialyze it against distilled water to remove the organic solvent, and then freeze-dry the product at -40°C to obtain an amphiphilic covalent organic polymer material. 1.2 Weigh the amphiphilic covalent organic polymer obtained in step 1.1 and dissolve it in water. Ultrasonicate for more than 15 minutes to ensure that the material is evenly dispersed in the aqueous solution to obtain a repair agent. Step 2: In-situ injection of amphiphilic covalent organic polymer for long-term remediation of o-phenylenediamine contaminated groundwater: 2.1 In areas near groundwater pollution sources, several injection wells should be installed upstream of the groundwater flow, perpendicular to the groundwater flow direction. Several extraction wells should be installed downstream of the injection wells, at the edge of the pollution plume. Monitoring wells should be installed every 3-5 meters downstream of the injection wells. The depth of the injection wells, extraction wells, and monitoring wells should all reach the bottom of the aquifer. 2.2 The concentration of the remediation agent is determined according to the formation conditions. The remediation agent is injected at a preset concentration using a pressure pulse device. When the remediation agent migrates to the extraction well, the extraction pump is activated to form a hydraulic gradient, achieving directional migration of the remediation agent and the formation of an adsorption reaction zone. The bottom section of the injection well and the section of the aeration zone are sealed, and water outlet holes are evenly distributed in the aquifer section. 2.3 Monitor the OPD concentration in real time during the injection process and stop the injection when the desired effect is achieved.

2. The method for long-term remediation of groundwater contaminated by o-phenylenediamine using an amphiphilic covalent organic polymer according to claim 1, characterized in that: The OPD concentration was no more than 20 mg / L. A remediation agent was prepared by uniformly dispersing 0.1–0.3 g of a covalent organic polymer in 1 L of distilled water. The injection flow rate was controlled by a peristaltic pump within the range of 1.59–3.18 cm / min, and the formation medium was a coarse sand medium with a thickness of 0.5–1.0 mm.

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