An integrated water treatment process coupling contaminant mineralization and sorbent production

Abstract

This invention discloses an integrated water treatment process coupling pollutant mineralization and adsorbent preparation, comprising the following steps: 1) Wastewater passes through a PCPs-based carbon material adsorption layer to remove dissolved pollutants; 2) Purified water is discharged from the outlet; 3) After adsorption saturation, the PCPs-based carbon material is regenerated with a regeneration solution, and high-concentration pollutants are discharged with the regeneration solution; 4) Organic ligands and metal solutions are added to the regeneration solution, and PCPs are generated through coordination polymerization, adsorbing dissolved pollutants and encapsulating them inside the PCPs, which then enter a sedimentation tank; 5) The effluent from the sedimentation tank is recycled as a regeneration solution, and the pollutant-containing PCPs are collected through a funnel; 6) The collected PCPs are dried and pyrolyzed to mineralize the pollutants and convert them into PCPs-based carbon material, which can be reused as an adsorbent. This invention proposes a novel water treatment process concept with broad application prospects for treating recalcitrant organic pollutants in wastewater.

Description

Technical Field

[0001] This invention relates to the field of water treatment, and more specifically to an integrated water treatment process that couples pollutant mineralization and adsorbent preparation. Background Technology

[0002] Perfluorinated and polyfluoroalkyl compounds (PFAS) are known as permanent chemicals because their molecules contain extremely stable CF bonds, making them difficult to degrade naturally. PFAS entering the aquatic environment pose a significant risk to human health, leading to increased research focus on PFAS treatment technologies in water. Adsorption methods can effectively remove PFAS from water, but saturated adsorbents merely transfer the PFAS from the aqueous phase. Even with solvent regeneration after adsorption saturation, the resulting regenerated solvent contains a high concentration of PFAS, requiring further treatment. These methods do not completely eliminate the health risks posed by PFAS, necessitating further treatment to fully mineralize them. However, directly thermally treating the regenerated reagent has drawbacks such as high energy consumption and resource depletion.

[0003] Pyrolysis of saturated adsorbents is currently recognized as an effective and stable degradation technology for PFAS. However, the pyrolysis process also has potential drawbacks such as adsorbent mass loss, pore structure collapse, and deterioration of adsorption performance. Porous coordination polymers (PCPs) are excellent precursors for porous carbon materials. During pyrolysis, they form a porous carbon framework, loading metal sites while possessing a well-developed microporous structure and defects, making them particularly suitable for the deep removal of PFAS from water. Notably, if the PCP formation site is located in the regeneration wastewater to be treated, PFAS in the regeneration solution can be adsorbed during PCP formation and encapsulated within the PCPs. Subsequently, the PCPs containing a high concentration of PFAS are collected and pyrolyzed, simultaneously achieving PFAS mineralization and the preparation of PCPs-based carbon materials. Compared to the traditional method of adding the finished carbon material adsorbent to the wastewater followed by pyrolysis regeneration, this approach is more economical and effective, and avoids the negative impact of frequent pyrolysis regeneration on the adsorbent's pore structure. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated water treatment process that couples pollutant mineralization and adsorbent preparation, thereby solving the problem that existing technologies lack a low-cost and effective wastewater treatment process for recalcitrant organic pollutants.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] An integrated water treatment process coupling pollutant mineralization and adsorbent preparation is provided, comprising the following steps: 1) Wastewater enters the adsorption tower through the inlet and flows through the adsorption layer using PCPs-based carbon material as the adsorbent, removing dissolved pollutants in the wastewater through adsorption; 2) After purification by the PCPs-based carbon material layer, the wastewater flows out from the purified water outlet; 3) The PCPs-based carbon material is regenerated by adding a regeneration solution, and the regeneration solution carrying a high concentration of pollutants flows out from the regeneration solution outlet; 4) An organic ligand solution and a metal solution are added simultaneously or sequentially to the outflowing regeneration solution. The process involves coordination polymerization to generate PCPs, which adsorb dissolved pollutants in the regeneration solution and encapsulate them inside the PCPs. After the reaction is complete, the PCPs enter the sedimentation tank. 5) The effluent from the sedimentation tank is reused as a regeneration solution. Meanwhile, PCPs containing high concentrations of organic pollutants are collected through a funnel at the bottom. 6) The collected PCPs are processed through a dryer and a pyrolysis machine. A pore-forming agent or activator that promotes the formation of pore structures is added. During the pyrolysis process, the adsorbed organic pollutants are mineralized into inorganic small molecules, and PCPs-based carbon materials are formed to be used as adsorbents in the adsorption tower.

[0007] Preferably, in step 3), the regeneration solution is a mixed solution of water and organic solvent that has been adjusted for acidity and alkalinity, with the organic solvent accounting for 0-80% of the volume and the acidity and alkalinity adjustment range being neutral to alkaline.

[0008] Preferably, in step 4), the metal salt includes: zinc nitrate, zinc acetate, copper sulfate, copper nitrate, ferric nitrate, ferric chloride, ferrous sulfate, ferric acetate, cobalt nitrate, cobalt acetate, nickel nitrate, nickel acetate, manganese nitrate, manganese chloride, etc.

[0009] Preferably, the organic ligand includes: 2-methylimidazole, terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 5-methylisophthalic acid, 4,4'-biphenyldicarboxylic acid, pyromellitic acid, and pyridine derivatives.

[0010] Preferably, the dosage of metal salt and organic ligand is 0.01 g / L to 10 g / L.

[0011] Preferably, the molar ratio of metal to organic ligand is metal:organic ligand = 1:1 to 1:8.

[0012] Preferably, the combination of metal salt and organic ligand can be selected from: pyromellitic acid + ferric nitrate, 2-methylimidazole + copper sulfate.

[0013] Preferably, in step 6), pyrolysis is performed at 400–1000°C for 1–3 hours to achieve the mineralization and decomposition of organic pollutants.

[0014] According to a preferred embodiment of the present invention, in step 6), the collected PCPs are pyrolyzed and formed into granular carbon, which is then added to the adsorption tower for use as an adsorbent.

[0015] Preferably, the pore-forming agent or activator can be selected from ammonium bicarbonate or potassium hydroxide.

[0016] Preferably, the organic pollutant is a perfluorinated and polyfluoroalkyl compound, and by way of example and not limitation, the perfluorinated and polyfluoroalkyl compound is perfluorooctanoic acid (PFOA).

[0017] It should be understood that the purpose of this invention is to provide an integrated water treatment process that couples pollutant mineralization and adsorbent preparation. The embodiments specifically relate to a cyclical treatment approach for recalcitrant organic pollutants: PCPs-based carbon materials in the adsorption tower adsorb and remove organic pollutants from the water, generating a regeneration solution containing a high concentration of organic matter during regeneration; the organic pollutants in the regeneration solution are then adsorbed and encapsulated in situ during the PCPs formation process, thus entering the PCPs solid phase; finally, through pyrolysis of the PCPs, PCPs-based carbon materials are formed while mineralizing the organic pollutants, and these materials are reused as adsorbents in the adsorption tower. However, this invention is not limited to the cyclical treatment of recalcitrant organic pollutants and can be extended to other types of wastewater treatment.

[0018] Based on the in-situ adsorption and encapsulation characteristics of pollutants during PCP formation, the main objective of this invention is to provide a wastewater treatment process. However, considering that the in-situ adsorption and encapsulation process of pollutants during PCP formation may lead to unsatisfactory performance due to the complex composition of wastewater, and that incomplete coordination reactions may cause secondary pollution, this invention innovatively provides an integrated water treatment process that couples pollutant mineralization and adsorbent preparation. The PCP formation process is set within a regeneration solution containing pollutants, allowing for the recovery and reuse of the treated regeneration solution and unreacted reagents. Moreover, this process is particularly effective against recalcitrant organic pollutants such as PFAS, achieving stable removal and degradation at a relatively low cost.

[0019] Specifically, this invention uses PCPs-based carbon materials as adsorbents in an adsorption tower for the advanced treatment of recalcitrant organic pollutants such as PFAS in water. After the PCPs-based carbon materials become saturated, they are regenerated, desorbing high-concentration recalcitrant organic pollutant wastewater. Subsequently, dissolved pollutants in the regeneration solution are adsorbed and encapsulated within the PCPs during the PCPs formation process. The PCPs containing high-concentration pollutants are then pyrolyzed to simultaneously mineralize the pollutants and prepare the PCPs-based carbon materials. Finally, the PCPs-based carbon materials are used to fill the adsorption tower. This invention couples and simultaneously completes the mineralization of pollutants and the preparation of adsorbents, enhancing the economic efficiency of PCPs-based carbon materials in the adsorption process and demonstrating significant application potential in the treatment of recalcitrant organic wastewater.

[0020] The integrated water treatment process combining pollutant mineralization and adsorbent preparation provided by the present invention has the following advantages over the prior art:

[0021] 1) This invention combines the in-situ adsorption and encapsulation characteristics of pollutants during the formation of PCPs with reliable pyrolysis technology, thereby reducing treatment costs while achieving good PFAS degradation effect.

[0022] 2) By first adsorbing, then eluting, and then using the PCPs formation process to adsorb and encapsulate pollutants in situ, compared with direct pyrolysis to treat the regenerated solution, the amount of treatment and energy consumption costs are greatly reduced.

[0023] 3) This invention fully realizes resource recycling and is more environmentally friendly;

[0024] 4) This invention is not limited to the effective and low-cost treatment of PFAS, but is also applicable to various other wastewater treatment scenarios.

[0025] In summary, the integrated water treatment process for coupling pollutant mineralization and adsorbent preparation provided by this invention is based on the adsorption capacity of PCPs-based carbon materials. First, the PCPs-based carbon materials remove pollutants from wastewater through adsorption. Then, the in-situ adsorption and encapsulation during the PCP formation process remove pollutants from the regeneration solution. Subsequently, the newly obtained PCPs-based carbon materials are added to the PCPs-based carbon material layer of the adsorption tower. This achieves both the degradation of organic pollutants and the resource utilization of pyrolysis products. With a single pyrolysis energy input, the objectives of pollutant mineralization and adsorbent preparation are achieved simultaneously, successfully realizing low-cost and effective treatment of recalcitrant organic pollutants in wastewater. Attached Figure Description

[0026] Figure 1A flow chart of an integrated water treatment process that couples pollutant mineralization and adsorbent preparation according to the present invention is shown.

[0027] Figure 2 The in-situ encapsulation adsorption of pyromellitic acid + ferric nitrate during the PCPs formation process is shown to exhibit the adsorption performance of a simulated regenerated solution containing a high concentration of PFOA.

[0028] Figure 3 The in-situ encapsulation adsorption of 2-methylimidazole + copper sulfate during PCPs formation was demonstrated, showing the adsorption performance of a simulated regenerated solution containing a high concentration of PFOA. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the techniques used in the embodiments are conventional practices in the art, or experimental methods recommended by the instrument manufacturer. Unless otherwise specified, the reagents and materials used in the embodiments are commercially available.

[0030] Please see Figure 1 , Figure 1 The present invention provides a flowchart of an integrated water treatment process coupling pollutant mineralization and adsorbent preparation, as shown in the figure. The method includes the following steps:

[0031] 1) Wastewater enters the core treatment unit through the inlet at the top of the adsorption tower. The packing material here is PCPs-based carbon material, which adsorbs and removes pollutants in the wastewater. After being purified by the PCPs-based carbon material layer, the wastewater flows out from the purified water outlet.

[0032] 2) When the system has been running for a period of time and the PCPs-based carbon material has reached the adsorption saturation, the PCPs-based carbon material is regenerated through the regeneration solution inlet, and then the regeneration solution flows out from the top.

[0033] In step 2), for example, to regenerate and elute PFOA, a mixed solution of methanol and deionized water can be used.

[0034] 3) The regenerated solution flowing out from the top serves as the influent for the in-situ encapsulation adsorption unit in the PCPs formation process, and often contains high concentrations of organic pollutants. The in-situ encapsulation adsorption steps in the PCPs formation process are given as an example, not a limitation. Organic ligand solutions and metal solutions can be added to the wastewater sequentially, allowing metal ions to undergo coordination polymerization with the organic ligands to generate PCPs, which adsorb the organic pollutants in the wastewater. After sufficient adsorption, the PCPs enter the sedimentation tank. The preferred dosage of metal salts and organic ligands is 0.01 g / L to 10 g / L.

[0035] It should be understood that the organic ligand solution and the metal solution can be added to the wastewater sequentially, or the order can be reversed, or the organic ligand solution and the metal solution can be added simultaneously. This invention does not limit the order of addition. However, their performance may differ because the process of reacting to form PCPs crystals is affected by the concentrations of the metal and ligands, as well as other factors. Optimal results require exploration and optimization based on actual conditions. Alternatively, the organic ligand solution and the metal solution can be mixed and reacted first before being added to the wastewater to prevent the concentrations of the organic ligand solution and the metal solution from being too low, which could affect the coordination reaction, or to avoid interference from other components in the wastewater.

[0036] 4) The effluent from the sedimentation tank is collected and reused as a regeneration solution or backwash liquid; meanwhile, PCPs containing high concentrations of organic pollutants are collected through the lower funnel.

[0037] 5) The collected PCPs are first dried in a dryer to remove moisture, and then fed into a pyrolysis machine. During pyrolysis, organic pollutants are mineralized and decomposed, while the PCPs are carbonized and activated into porous carbon materials. The PCPs-based carbon materials prepared after pyrolysis can be shaped and used in adsorption towers to achieve resource recycling.

[0038] The pyrolysis conditions are those that can completely mineralize the adsorbed target pollutants. For example, the PFOA we studied here can be completely mineralized by pyrolysis at 600℃ for 2 hours. If there are other types of pollutants, it is necessary to test the mineralization temperature and time of these pollutants first, and then determine the pyrolysis conditions based on the test results.

[0039] As an example, the embodiments of the present invention below selected ferric nitrate and copper sulfate as metal salts, pyromellitic acid and 2-methylimidazole as organic ligands, and PFOA as a dissolved pollutant. The in-situ encapsulation adsorption performance of two combinations, pyromellitic acid + ferric nitrate and 2-methylimidazole + copper sulfate, during the PCPs formation process was tested. The removal performance was compared with that of a PFOA solution containing 20% ​​methanol and 200 μg / L, simulating a regeneration solution with a high concentration of PFOA. Next, the PCPs after adsorbing the high-concentration PFOA solution were collected, subjected to pyrolysis, eluted, and the PFOA content in the eluent was detected.

[0040] Example 1

[0041] The in-situ encapsulation adsorption process during PCP formation was used to remove PFOA from the regeneration solution. In a 100 mL PP beaker, 20 mL of methanol, 10 mL of PFOA solution (2 mg / L), and 70 mL of deionized water were added. The mixture was stirred for 5 min, and a sample was taken as the initial value. The solution was then discarded, rinsed, and 20 mL of methanol and 10 mL of PFOA solution (2 mg / L) were added again. Two separate 50 mL beakers were prepared, and 35 mL of deionized water was added to each beaker to dissolve equal masses of ferric nitrate and trimesic acid (0.108, 0.216, 0.432, and 0.864 g, respectively). After dissolution, the solutions were mixed and stirred in a 100 mL glass beaker for 30 min to generate PCPs. The generated PCPs were then added to the system under stirring conditions, and the mixture was stirred for 60 min. A sample was taken from the supernatant for analysis.

[0042] Experimental results are as follows Figure 2 As shown, when the dosage of metal and organic ligands is 1.08 g / L, the removal rate of PFOA can reach 94.2%. With the increase of dosage, the removal rate tends to 100%, which verifies the feasibility of in-situ encapsulation adsorption during the formation of PCPs for the removal of high concentrations of PFOA in the regeneration solution.

[0043] Example 2

[0044] The in-situ encapsulation adsorption process during PCP formation was used to remove PFOA from the regeneration solution. In a 100 mL PP beaker, 20 mL of methanol, 10 mL of PFOA solution (2 mg / L), and 70 mL of deionized water were added. The mixture was stirred for 5 min, and a sample was taken as the initial value. The solution was then discarded, rinsed, and 20 mL of methanol and 10 mL of PFOA solution (2 mg / L) were added again. Two separate 50 mL beakers were prepared, and 35 mL of deionized water was added to each beaker to dissolve equal masses of copper sulfate and 2-methylimidazole (0.108, 0.216, 0.432, and 0.864 g, respectively). After dissolution, the solutions were mixed and stirred in a 100 mL glass beaker for 30 min to generate PCPs. The generated PCPs were then added to the system under stirring conditions, and the mixture was stirred for 60 min. A sample was taken from the supernatant for analysis.

[0045] Experimental results are as follows Figure 3 As shown, 2-methylimidazole + copper sulfate achieved similar results to trimesic acid + ferric nitrate. With the increase of dosage, the removal rate tended to 100%, verifying the feasibility of other combinations for removing high concentrations of PFOA in the regeneration solution.

[0046] Example 3

[0047] Feasibility of pyrolysis mineralization of PFOA: 10 mL of PFOA solution (2 mg / L) was added to a 100 mL PP beaker, followed by 40 mL of deionized water and 0.054 g of pyromellitic acid. In another beaker, 50 mL of deionized water and 0.054 g of ferric nitrate were added and stirred for 60 min. The solution was then centrifuged, dried, and milled to obtain the original PCPs product containing PFOA. The product was pyrolyzed in a tube furnace at 600 °C for 2 h. The pyrolysis product was placed in an ion exchange tube, 50 mL of 20% methanol solution was added, and the supernatant was sampled and analyzed after centrifugation.

[0048] The results showed that PFOA could not be detected in the elution supernatant, confirming that pyrolysis had a good mineralization effect on PFOA.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. An integrated water treatment process coupling pollutant mineralization and adsorbent preparation, characterized in that, Includes the following steps: 1) Wastewater enters the adsorption tower through the inlet and flows through the adsorption layer with PCPs-based carbon material as the adsorbent, removing dissolved pollutants from the wastewater through adsorption. 2) The wastewater flows out from the purified water outlet after being purified through the PCPs-based carbon material layer; 3) PCPs-based carbon materials are regenerated by adding a regeneration solution, which carries a high concentration of dissolved pollutants and flows out from the regeneration solution outlet; 4) Add organic ligand solution and metal salt solution simultaneously or sequentially to the outflowing regeneration solution to generate PCPs through coordination polymerization. PCPs adsorb dissolved pollutants in the regeneration solution and encapsulate them inside the PCPs. After the reaction is complete, the PCPs enter the sedimentation tank. 5) The effluent from the sedimentation tank is reused as a regeneration solution; meanwhile, PCPs containing high concentrations of organic pollutants are collected through the lower funnel. 6) The collected PCPs are processed through a dryer and a pyrolysis machine. A pore-forming agent or activator that is conducive to the formation of pore structures is added. During the pyrolysis process, the adsorbed organic pollutants are mineralized into inorganic small molecules, and at the same time, PCPs-based carbon materials are formed to be used as adsorbents in the adsorption tower.

2. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, In step 3), the regeneration solution is a mixed solution of water and organic solvent that has been adjusted for acidity and alkalinity. The volume percentage of organic solvent is 0-80%, and the acidity and alkalinity adjustment range is from neutral to alkaline.

3. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, In step 4), the metal salt includes: zinc nitrate, zinc acetate, copper sulfate, copper nitrate, ferric nitrate, ferric chloride, ferrous sulfate, ferric acetate, cobalt nitrate, cobalt acetate, nickel nitrate, nickel acetate, manganese nitrate, or manganese chloride.

4. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, In step 4), the organic ligand includes: 2-methylimidazolium, terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 5-methylisophthalic acid, 4,4'-biphenyldicarboxylic acid, pyromellitic acid, or pyridine derivatives.

5. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, The dosage of both metal salts and organic ligands ranged from 0.01 g / L to 10 g / L.

6. The integrated water treatment process coupling pollutant mineralization and adsorbent preparation according to claim 1, characterized in that, The molar ratio of metal salt to organic ligand is metal salt:organic ligand = 1:1 to 1:

8.

7. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, The combination of organic ligand and metal salt can be selected from: trimellitic acid + ferric nitrate, trimellitic acid + ferrous acetate, 2-methylimidazole + ferric nitrate, 2-methylimidazole + ferrous sulfate, 2-methylimidazole + ferrous acetate, 2-methylimidazole + copper sulfate, trimellitic acid + zinc nitrate, and 2-methylimidazole + zinc nitrate.

8. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, In step 6), pyrolysis is carried out at 400~1000℃ for 1h~3h to achieve mineralization and decomposition of organic pollutants.

9. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 1, wherein, The dissolved contaminants are perfluorinated and polyfluorinated alkyl compounds.

10. The integrated water treatment process coupling contaminant mineralization and sorbent production of claim 9, wherein, The perfluorinated and polyfluoroalkyl compounds include perfluorooctanoic acid.

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