A recycling technology for thermally responsive adsorbent materials

Abstract

The present invention belongs to the technical field of water pollution treatment, and discloses a recycling technology for heat-responsive adsorbent materials with high critical solution temperature characteristics. The recycling technology for heat-responsive adsorbent materials with high critical solution temperature characteristics comprises: preparing a mixed solution of sodium iodide and sodium hydroxide, placing the heat-responsive adsorbent material adsorbed with perfluorinated compounds in the mixed solution for heat treatment, collecting through filtration, and then washing with ultrapure water and ethanol alternately to complete the regeneration of the adsorbent material for the cyclic adsorption of pollutants. The regeneration and recycling technology developed by the present invention for heat-responsive adsorbent materials with high critical solution temperature characteristics has the advantages of strong desorption ability, good regeneration effect, high practical application value, etc. It can be used for the cyclic adsorption of hydrophobic pollutants represented by perfluorinated compounds in water bodies, and is a very promising regeneration treatment technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of water pollution treatment, and in particular relates to a recycling technology for thermally responsive adsorbent materials. Background Art

[0002] Perfluorinated chemical compounds (PFASs) have been widely used in industry for decades but are ubiquitous in the environment due to their chemical persistence. Exposure to PFASs poses serious health risks, such as liver and kidney cancer, and as a result, these compounds are now considered priority pollutants. Among the current methods for removing PFCs, adsorption is considered one of the most suitable technologies.

[0003] Currently, common adsorbents that can be used to remove perfluorinated compounds include carbon materials, resins, etc. However, adsorbents cannot be used continuously to remove perfluorinated compounds. As the adsorption time increases, a large number of adsorption sites are occupied by pollutants, and the effective adsorption sites continue to decrease, resulting in a decrease in the adsorption performance of the adsorbent. From the perspective of economic benefits, the adsorbent needs to be reusable to reduce the consumption of the adsorbent. The currently commonly used regeneration strategy for adsorbents for adsorbing fully fluorinated compounds is to use chemical reagents for regeneration, but the effect is poor. At the same time, a large amount of chemical reagents may also cause secondary pollution. Therefore, how to improve the efficient regeneration and recycling of adsorbents is of great significance for the effective removal of perfluorinated compounds.

[0004] Through the above analysis, the problems and defects of the existing technology are: after the adsorbent adsorbs the fully fluorinated compounds, it is difficult to desorb them efficiently, and the adsorbent cannot be recycled, resulting in high treatment costs for perfluorinated compounds.

[0005] The difficulty in solving the above problems and defects is that the current commonly used regeneration strategy for adsorbents for fully fluorinated compounds is to use chemical reagents, but the effect is poor. At the same time, large amounts of chemical reagents may also cause secondary pollution.

[0006] The significance of solving the above problems and defects is to help reduce the processing cost of perfluorinated compounds. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a regeneration and recycling technology for a thermally responsive adsorbent material having a high critical solution temperature characteristic.

[0008] The details are as follows:

[0009] Step 1: preparing a mixed solution of sodium iodide and sodium hydroxide;

[0010] Step 2: placing the thermally responsive adsorbent material adsorbed with the perfluorinated compound into the mixed solution in step 1;

[0011] Step 3, heating the mixed solution containing the heat-responsive adsorbent material adsorbing the perfluorinated compound in Step 2;

[0012] Step 4: Take out the heat-responsive adsorbent material that has been heated in step 3, and rinse it alternately with ultrapure water and ethanol.

[0013] In step 1, the mass volume ratio of sodium iodide to water in the mixed solution of sodium iodide and sodium hydroxide is 20 mg to 40 mg:100 mL, and the mass volume ratio of sodium hydroxide to water is 20 to 60 g:100 mL;

[0014] In step 2, the thermally responsive adsorbent material should have a high critical solution temperature characteristic, and the critical temperature is 40-60°C;

[0015] In step 3, the heating temperature is 45-65°C, the heating rate is 1-5°C / min, and the heating time is 4-12h;

[0016] In step 4, the ethanol concentration is 50%; the alternating flushing sequence is ultrapure water at a temperature of 45 to 65° C. - ethanol - ultrapure water at a temperature of 45 to 65° C. - ethanol - ultrapure water at room temperature.

[0017] In combination with all the above-mentioned technical solutions, the advantages and positive effects of the present invention are as follows: the regeneration and recycling technology for heat-responsive adsorbent materials with high critical solution temperature characteristics provided by the present invention. In the present invention, the heat-responsive adsorbent material with high critical solution temperature characteristics is made to respond to changes in temperature through heat treatment, and its chain conformation undergoes drastic changes, showing hydrophilicity, thereby destroying the hydrophobic interaction between the adsorbent and the perfluorinated compound. In addition, the use of a mixed solution of sodium iodide and sodium hydroxide to inhibit the electrostatic attraction between the adsorbent and the perfluorinated compound can promote the desorption of the perfluorinated compound, which is beneficial to the regeneration of the adsorbent. The regeneration and recycling technology developed by the present invention for heat-responsive adsorbent materials with high critical solution temperature characteristics has the advantages of strong desorption ability, good regeneration effect, high practical application value, etc. It can be used for the cyclic adsorption of hydrophobic pollutants represented by perfluorinated compounds in water bodies, and is a very promising regeneration treatment technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1It is a flow chart of the recycling technology for thermally responsive adsorbent materials;

[0020] Figure 2 This is the adsorption effect of the adsorbent regenerated by Example 2 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] In view of the problems existing in the prior art, the present invention provides a recycling technology for thermally responsive adsorbent materials. The present invention is described in detail below with reference to the accompanying drawings.

[0023] The recycling technology for thermally responsive adsorbent materials provided in an embodiment of the present invention includes the following steps:

[0024] S101, preparing a mixed solution of sodium iodide and sodium hydroxide;

[0025] S102, placing a thermally responsive adsorbent material adsorbing a perfluorinated compound into the mixed solution in step 1;

[0026] S103, heating the mixed solution containing the heat-responsive adsorbent material adsorbing the perfluorinated compound in step 2;

[0027] S104, taking out the heat-responsive adsorbent material that has been heated in step 3, and washing it alternately with ultrapure water and ethanol.

[0028] The thermally responsive adsorbent materials used in the following examples were homemade, and the remaining materials and instruments were commercially available. In the examples of the present invention, unless otherwise specified, the processes and equipment used were conventional, and the data obtained were the average of more than three tests.

[0029] The technical solution of the present invention is further described below in conjunction with embodiments.

[0030] Example 1

[0031] The recycling technology for the thermally responsive adsorbent material in the above embodiment provided by the embodiment of the present invention includes the following steps:

[0032] (1) The sawdust was washed with deionized water and then dried at 70 °C for 24 hours. The dried sawdust was crushed and sieved (0.15 mm to 0.25 mm) and then placed in a tubular furnace for pyrolysis and firing. During the pyrolysis process, the quartz tube of the tubular furnace was kept sealed and nitrogen was introduced into the tube at a flow rate of 200 mL / min to maintain anaerobic conditions throughout the pyrolysis process. The heating program of the tubular furnace was set as follows: heating from room temperature to 600 °C at a heating rate of 3 °C / min, and pyrolysis was continued at this temperature for 2 hours, and then a natural cooling process was started. During the cooling process, nitrogen was continuously introduced at the same flow rate. After cooling to room temperature, the raw biochar was taken out and obtained. Prepare 100 mL of a mixed solution of acrylamide and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, with a mass ratio of acrylamide to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide of 10 g:15 g. Add 5 g of biochar to the above mixed solution, stir at 35°C at a speed of 150 rpm for 12 hours, introduce N2 into the solution at a flow rate of 100 mL / min, and stir at 35°C at a speed of 180 rpm for 1 hour to obtain a black suspension. Add 5 mg of ammonium persulfate to the above black suspension, stir at 60°C at a speed of 120 rpm for 12 hours, collect the solid by filtration, and dry the solid to obtain a thermally responsive adsorbent material.

[0033] (2) The heat-responsive adsorbent material prepared in step (1) and water (aqueous solution containing perfluoro compounds) were mixed at a mass-to-volume ratio of 0.1 g:1 L. Four portions of the heat-responsive adsorbent material prepared in step (1) were weighed and added to a solution containing perfluorooctane sulfonic acid (hereinafter referred to as PFOS) and perfluorooctanoic acid (hereinafter referred to as PFOA) at a concentration of 10 mg / L (the volume of the solution was 100 mL). The mixture was uniformly mixed and subjected to constant temperature oscillation treatment at a speed of 180 rpm and a temperature of 25° C. for 24 h to complete the adsorption treatment of the aqueous solution containing perfluoro compounds.

[0034] (3) preparing a mixed solution of sodium iodide and sodium hydroxide, wherein the mass volume ratio of sodium iodide to water is 30 mg:100 mL, and the mass volume ratio of sodium hydroxide to water is 40 g:100 mL;

[0035] (4) placing the thermally responsive adsorbent material adsorbing the perfluorinated compound in the mixed solution of step (3), heating the mixed solution to 65° C. at a heating rate of 5° C. / min, and heating for 12 h;

[0036] (5) After the mixed solution in step (4) is heated, the thermally responsive adsorbent material is collected by filtration;

[0037] (6) using ultrapure water at a temperature of 65° C., ethanol, ultrapure water at a temperature of 65° C., ethanol, and ultrapure water at room temperature to sequentially rinse the thermally responsive adsorbent material collected in step (5), thereby completing the adsorption regeneration of the thermally responsive adsorbent material;

[0038] (7) The thermally responsive adsorbent material obtained in step (6) was subjected to an adsorption treatment on the aqueous solution containing perfluorinated compounds according to the method of step (2) to complete the cyclic adsorption of the aqueous solution containing perfluorinated compounds; after the oscillation treatment, the solution was allowed to settle, and the supernatant was taken and the concentration of perfluorinated compounds was determined by HPLC-HRMS / MS, and the adsorption amount of perfluorinated compounds by the hydrophobic biochar composite material was calculated based on the above, and the results are shown in Table 1;

[0039] (8) As a comparison, the thermoresponsive adsorbent material in step (2) was impregnated with 50% ethanol for 12 h, and then the thermoresponsive adsorbent material was collected by filtration. The perfluorinated compound aqueous solution was adsorbed according to the method of step (2) to complete the cyclic adsorption of the perfluorinated compound aqueous solution.

[0040] Table 1 Adsorption removal rate of perfluorinated compounds after adsorbent regeneration by different technologies

[0041] PFOS PFOA 50% ethanol regeneration technology 26.9％ 20.5％ Recycling technology for thermally responsive adsorbent materials 96.2％ 94.3％

[0042] As shown in Table 1, compared with the currently common ethanol regeneration scheme, the recycling technology for the thermally responsive adsorbent material provided by the present invention can achieve better regeneration effect. After regeneration, the adsorption removal rate of the adsorbent for PFOS and PFOA increased from less than 30% to more than 94%, a significant improvement.

[0043] Example 2

[0044] The application of the recycling technology for thermally responsive adsorbent materials provided in the embodiments of the present invention, specifically the application of thermally responsive adsorbent materials in desorption and regeneration after adsorption of perfluorinated compounds in water, includes the following steps:

[0045] Using the self-made thermal responsive adsorbent material in Example 1, refer to steps (2 to 7) in Example 1 and repeat 4 times. After the oscillation treatment, the mixture was allowed to settle and the supernatant was taken and the concentration of perfluorinated compounds was determined by HPLC-HRMS / MS. The adsorption amount of perfluorinated compounds by the hydrophobic biochar composite material was calculated based on the above results. Figure 2 shown.

[0046] according to Figure 1The results show that after five cycles, the removal rate of the adsorbent material remained at approximately 81%. This indicates that the recycling technology for thermally responsive adsorbent materials provided by the present invention is beneficial for improving the regeneration performance of adsorbent materials and expanding their application in contaminated water bodies. It has high application value in the treatment of contaminated water bodies and has broad application prospects.

[0047] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for regenerating and recycling a thermally responsive adsorbent material having a high critical solution temperature, as follows: Step 1: Prepare a mixed solution of sodium iodide and sodium hydroxide; the mass volume ratio of sodium iodide to water in the mixed solution of sodium iodide and sodium hydroxide is 20 mg to 40 mg:100 mL, and the mass volume ratio of sodium hydroxide to water is 20 to 60 g:100 mL; Step 2: placing a heat-responsive adsorbent material adsorbing a perfluorinated compound into the mixed solution of step 1; the heat-responsive adsorbent material should have a high critical solution temperature characteristic, with a critical temperature of 40 to 60° C.; Step 3: heating the mixed solution containing the heat-responsive adsorbent material adsorbing the perfluorinated compound in step 2; the heating temperature is 45 to 65° C., the heating rate is 1 to 5° C. / min, and the heating time is 4 to 12 hours; Step 4: Take out the heat-responsive adsorbent material that has been heated in step 3 and rinse it alternately with ultrapure water and ethanol; the ethanol concentration is 50%; the alternating rinsing order is ultrapure water at a temperature of 45 to 65°C - ethanol - ultrapure water at a temperature of 45 to 65°C - ethanol - ultrapure water at room temperature.

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