Method for selectively separating and recycling organic matters
The use of a water-soluble carbon nitride with hydrophilic groups and CO2/organic acids for reversible sol-gel transformation addresses the challenges of organic pollutant recovery in wastewater, achieving efficient purification and recycling of organic matter while reducing environmental impact.
Patent Information
- Application Number
- CN202411331039.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2024-12-27
AI Technical Summary
Existing wastewater purification technologies face challenges such as unstable treatment efficiency, secondary pollution, difficulty in material recovery and regeneration, and high operating costs when dealing with difficult-to-biodegrade organic pollutants, and traditional adsorption methods hinder the recovery of organic matter due to the contradiction between adsorption and desorption processes.
A method using a water-soluble carbon nitride with hydrophilic groups, prepared via an ionothermal process, forms a hydrogel with CO2 or organic acids as cross-linking agents, enabling reversible sol-gel transformation for selective adsorption and desorption of organic matter, allowing for efficient recovery.
The method achieves efficient wastewater purification and recovery of value-added organic matter, reducing carbon resource waste and greenhouse gas emissions, with high adsorption and desorption efficiencies, and the carbon nitride can be recycled for reuse.
Smart Images
Figure CN119192097A_ABST
Abstract
Description
Technical Field
[0001] The invention discloses a method for selectively separating and recovering organic matter, and belongs to the technical field of wastewater purification and treatment in environmental protection. Background Art
[0002] Since more than a quarter of the world's population still lacks access to clean drinking water, drinking water purification technologies that remove pollutants from water (especially toxic organic pollutants that are difficult to biodegrade) are of great significance for alleviating the shortage of freshwater resources. In recent decades, researchers have been committed to the development of efficient wastewater purification technologies. However, the concept of treating organic matter in water as pollutants often limits us to degrading mineralized pollutants through various advanced oxidation technologies (AOPs). Although significant progress has been made, there are still disadvantages in actual wastewater purification, such as unstable treatment efficiency (caused by complex wastewater matrices), secondary pollution (caused by incomplete mineralization of organic matter), difficulty in material recovery and regeneration, and / or high operating costs. Therefore, there is an urgent need to break through traditional ideas and explore more effective and environmentally friendly methods to purify water bodies contaminated by difficult-to-biodegrade organic matter in an economical, efficient and low-carbon manner.
[0003] Organic matter, especially toxic chemicals in water, are often regarded as pollutants, and these chemicals are often indispensable intermediates in certain chemical synthesis fields. So why not change our perspective and recover these organics from wastewater? Selectively separating and recovering these organics from wastewater can not only provide valuable intermediates for chemical synthesis, but also provide solutions to water pollution problems. However, the key to achieving the goal of "killing two birds with one stone" lies in exploring new technologies for selectively separating and recovering organic matter from wastewater. Traditional adsorption methods use electrostatic attraction and / or hydrogen bonds between adsorbents and adsorbates to achieve adsorption and separation of adsorbates. However, electrostatic attraction or hydrogen bond formation is not conducive to the desorption process of adsorbates, hindering the recovery of adsorbates and the regeneration of adsorbents. In general, the contradiction between the adsorption and desorption processes of organic matter makes the recovery of organic matter in wastewater still a huge challenge.
[0004] Inspired by molecular imprinting using cross-linking agents to selectively adsorb organic matter, the present invention proposes a method for reversibly adsorbing and desorbing organic matter in wastewater using a cross-linking agent, thereby achieving selective separation and recovery of organic matter in wastewater. The present invention introduces a cross-linking agent to adsorb and separate organic matter, removes the cross-linking agent to desorb and recover organic matter, and provides a technical reference for efficient wastewater purification and recovery of value-added organic matter. Summary of the invention
[0005] In view of the above shortcomings, the purpose of the present invention is to provide a method for selective separation and recovery of organic matter, which solves the problems of carbon resource waste and greenhouse gas emissions caused by the prior art in treating organic matter in wastewater, and is low-cost, simple to operate, and reproducible. The present invention uses a simple ionothermal method to prepare a water-soluble carbon nitride with surface functionalized hydrophilic groups amino and hydroxyl groups, and selectively adsorbs and desorbs organic matter by adding and removing a cross-linking agent to trigger a hydrogen bond-mediated sol-gel reversible transformation of the water-soluble carbon nitride, thereby achieving efficient wastewater purification and recovery of value-added organic matter.
[0006] To achieve the above object, the present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0007] (1) melamine and alkali metal hydroxide are mixed, ground evenly and added into a crucible with a cover, and then the crucible is placed in a muffle furnace, heated and calcined in an air atmosphere, and naturally cooled to room temperature to obtain a yellow-brown solid powder;
[0008] (2) dispersing and dissolving the yellow-brown solid powder in water, dialyzing it to neutrality with a dialysis bag, and then evaporating the solution to dryness in a forced air drying oven to obtain a yellow solid powder of water-soluble carbon nitride;
[0009] (3) adding water-soluble carbon nitride to an aqueous solution containing organic matter and dissolving it by ultrasonication to form a sol;
[0010] (4) introducing CO2 into the sol or adding a small molecule organic acid as a cross-linking agent, mixing and letting stand for 10 min, the sol is transformed into a hydrogel;
[0011] (5) mechanically squeezing or centrifuging the hydrogel to obtain a supernatant and a dehydrated gel;
[0012] (6) passing Ar or adding alkaline solution into the dehydrated gel to remove the crosslinking agent, mixing and standing for 10 min, and the dehydrated gel is converted into a sol;
[0013] (7) filtering or centrifuging the sol to obtain a concentrated organic solution and a solid powder (catalyst);
[0014] (8) Exposing the solid powder (catalyst) to light to remove organic matter remaining on the surface, and then drying and recovering it for recycling;
[0015] (9) The organic matter removal efficiency and recycling efficiency are calculated using the following formula:
[0016]
[0017]
[0018] Where C0 and V0 are the initial concentration (mg / L) and volume (L) of organic matter in the simulated wastewater to be treated, respectively;
[0019] C1 and V1 are the concentration of organic matter in the supernatant after dehydration (mg / L) and the volume of the supernatant (L), respectively;
[0020] C2 and V2 are the concentration of organic matter (mg / L) and the volume of the supernatant (L) after the second separation treatment, respectively.
[0021] Furthermore, the alkali metal hydroxide in step (1) is a mixture of KOH and NaOH in a molar ratio of 10:5.
[0022] Furthermore, the dialysis bag in step (2) is a regenerated cellulose membrane with a molecular weight cutoff of 3.5 kDa.
[0023] Furthermore, in step (3), the organic matter concentration is 5 to 100 mg / L, and the water-soluble carbon nitride concentration is 0.5 to 5 mg / mL.
[0024] Furthermore, in step (4), the concentration of the cross-linking agent is not less than 2 mg / mL, and the organic acid includes but is not limited to: formic acid, acetic acid, and oxalic acid.
[0025] Furthermore, the alkaline solution in step (6) includes but is not limited to sodium hydroxide and potassium hydroxide solution.
[0026] Furthermore, the operating temperature of steps (2) to (7) is 25°C.
[0027] In combination with the above technical solutions, the beneficial effects of the present invention are:
[0028] (1) In the present invention, CO2 molecules and organic small molecule acids can be used as cross-linking agents to form hydrogels by hydrogen bonding with water-soluble carbon nitride and water molecules. The sol can be restored by introducing Ar or adding an alkaline solution to remove the introduced cross-linking agent, thereby achieving a reversible sol-gel transformation.
[0029] (2) The sol-gel reversible transformation strategy of the present invention realizes the selective separation and recovery of organic matter, solves the problems of carbon resource waste and "greenhouse effect" caused by the degradation of organic matter by the existing technology, and has good application prospects.
[0030] (3) The water-soluble carbon nitride prepared by the present invention is recyclable and can be reused. As the number of uses increases, the organic matter remaining on the surface can be removed by simple light irradiation, and its adsorption capacity can return to the initial level. (4) The method for selective separation and recovery of organic matter of the present invention is a low-cost, low-carbon, environmentally friendly, simple to operate, and reusable method for selective separation of organic matter, which can efficiently purify wastewater and recover value-added organic matter.
[0031] The surface of the water-soluble carbon nitride prepared by the present invention is functionally modified with hydrophilic groups amino and hydroxyl groups. CO2 molecules and organic small molecule acids such as acetic acid can act as crosslinking agents to trigger the water-soluble carbon nitride water-dispersed organic sol to form a hydrogel, and the hydrogel can be restored to the initial sol state by passing Ar or adding an alkaline solution to remove the introduced crosslinking agent. This CO2 molecule or organic small molecule triggers the hydrogen bond-mediated sol-gel reversible transformation of water-soluble carbon nitride to selectively adsorb and desorb organic matter, achieving efficient wastewater purification and recovery of value-added organic matter. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 It is an organic matter adsorption removal efficiency diagram of a method for selective separation and recovery of organic matter of the present invention;
[0033] Figure 2 It is an organic matter desorption recovery efficiency diagram of a method for selective separation and recovery of organic matter of the present invention;
[0034] Figure 3 The present invention is a method for selectively separating and recovering organic matter, and the schematic diagram of the operation of using water-soluble carbon nitride to purify methylene blue wastewater and recover methylene blue at the same time. DETAILED DESCRIPTION
[0035] The present invention is further described below with reference to the accompanying drawings and specific implementation examples.
[0036] The present invention provides a method for selective separation and recovery of organic matter, which adopts an ionothermal method to synthesize a water-soluble carbon nitride (S-CN) functionalized with a hydrophilic group, and uses CO2 or a small molecule organic acid as a crosslinking agent to crosslink water molecules, organic matter and S-CN, and the organic solution is transformed from a sol after adding S-CN into a hydrogel, and a supernatant and a dehydrated gel are obtained by mechanical extrusion or centrifugation, and then Ar is introduced into the dehydrated gel or an alkaline solution is added to remove the crosslinking agent and transform it into a sol, and the adsorbed organic matter is desorbed, and the organic concentrate and S-CN are recovered by filtration or centrifugation. The specific implementation steps are as follows:
[0037] (1) Melamine and alkali metal hydroxide (KOH, NaOH) are mixed in a molar ratio of 12:10:5, ground evenly, and added to a covered crucible. The crucible is then placed in a muffle furnace, heated to 330° C. in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature to obtain a yellow-brown solid.
[0038] (2) The yellow-brown solid obtained in (1) was dispersed and dissolved in water, and dialyzed to neutrality using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa. The solution was then placed in a forced air drying oven and evaporated to dryness at 80°C. The resulting yellow solid was the catalyst S-CN.
[0039] (3) dispersing and dissolving S-CN in an organic solution to form a mixed solution of S-CN and organic matter; wherein the organic matter includes: methylene blue, azure B, acriflavine, sulfamethoxazole, tetracycline and rhodamine B.
[0040] (4) CO2 is introduced into (3) or a small molecule organic acid is added, and the mixture is allowed to stand for 10 minutes, and the sol is converted into a hydrogel; wherein the concentration of CO2 or the small molecule organic acid is not less than 2 mg / mL.
[0041] (5) Mechanically squeeze or centrifuge the gel obtained in (4) to obtain a supernatant and a dehydrated gel, and calculate the organic matter removal efficiency based on the concentration of organic matter in the supernatant.
[0042] (6) Ar or alkaline solution is introduced into the dehydrated gel in (5), mixed evenly and allowed to stand for 10 min. The gel is converted into a sol and the adsorbed organic matter is desorbed. The recovery rate of the organic matter is calculated.
[0043] (7) Filtering or centrifuging (6) to recover the concentrated organic matter and S-CN; wherein the S-CN after desorbing the organic matter can be irradiated with light to remove the organic matter remaining on the surface and can be reused.
[0044] Example 1
[0045] The present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0046] 1.5 g of melamine, 0.56 g of KOH and 0.2 g of NaOH (molar ratio of 12:10:5) were ground evenly, added into a covered crucible and placed in a muffle furnace, heated to 330°C at 8°C / min in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature after calcination to obtain a yellow-brown solid powder; the obtained powder was dispersed and dissolved in 100 mL of ultrapure water, dialyzed to neutrality in ultrapure water using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa, and the solution was placed in a forced air drying oven and evaporated to dryness at 80°C to obtain S-CN; 20 mg of S-CN was dispersed and dissolved in 8 mL A sol is formed in a 100ppm methylene blue aqueous solution, and CO2 is introduced or a small molecule organic acid is added. After standing for 10 minutes, the sol is transformed into a hydrogel; the hydrogel is mechanically squeezed or centrifuged to obtain a supernatant and a dehydrated gel, wherein the removal efficiency of organic matter in the supernatant reaches 93.8%; Ar is then introduced into the dehydrated gel or an alkaline solution is added, the mixture is mixed evenly and the solution is allowed to stand for 10 minutes, the gel is transformed into a sol, and the adsorbed organic matter is desorbed; the sol is filtered or centrifuged to recover the concentrated organic matter and S-CN, wherein the recovery rate of the organic matter reaches 83.8%; the organic matter remaining on the surface of the recovered S-CN can be further removed by light to achieve the recycling of the catalyst.
[0047] Example 2
[0048] The present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0049] 1.5 g of melamine, 0.56 g of KOH and 0.2 g of NaOH (molar ratio of 12:10:5) were ground evenly, added into a covered crucible and placed in a muffle furnace, heated to 330°C at 8°C / min in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature after calcination to obtain a yellow-brown solid powder; the obtained powder was dispersed and dissolved in 100 mL of ultrapure water, dialyzed to neutrality in ultrapure water using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa, and the solution was placed in a forced air drying oven and evaporated to dryness at 80°C to obtain S-CN; 20 mg of S-CN was dispersed and dissolved in 8 mL A sol is formed in a 100 ppm azure B aqueous solution, CO2 is introduced or a small molecule organic acid is added, and the solution is allowed to stand for 10 minutes, and the sol is converted into a hydrogel; the hydrogel is mechanically squeezed or centrifuged to obtain a supernatant and a dehydrated gel, wherein the removal efficiency of organic matter in the supernatant reaches 95.4%; Ar is then introduced into the dehydrated gel or an alkaline solution is added, and the mixture is mixed evenly for 10 minutes, and the gel is converted into a sol, and the adsorbed organic matter is desorbed; the sol is filtered or centrifuged to recover the concentrated organic matter and S-CN, wherein the recovery rate of the organic matter reaches 86.1%; the organic matter remaining on the surface of the recovered S-CN can be further removed by light to achieve the recycling of the catalyst.
[0050] Example 3
[0051] The present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0052] 1.5 g of melamine, 0.56 g of KOH and 0.2 g of NaOH (molar ratio of 12:10:5) were ground evenly, added into a covered crucible and placed in a muffle furnace, heated to 330°C at 8°C / min in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature after calcination to obtain a yellow-brown solid powder; the obtained powder was dispersed and dissolved in 100 mL of ultrapure water, dialyzed to neutrality in ultrapure water using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa, and the solution was placed in a forced air drying oven and evaporated to dryness at 80°C to obtain S-CN; 20 mg of S-CN was dispersed and dissolved in 8 mL A sol is formed in a 100ppm acridinium yellow aqueous solution, CO2 is introduced or a small molecule organic acid is added, and the solution is allowed to stand for 10 minutes, and the sol is converted into a hydrogel; the hydrogel is mechanically squeezed or centrifuged to obtain a supernatant and a dehydrated gel, wherein the removal efficiency of organic matter in the supernatant reaches 98.5%; Ar is then introduced into the dehydrated gel or an alkaline solution is added, the mixture is mixed evenly and the solution is allowed to stand for 10 minutes, the gel is converted into a sol, and the adsorbed organic matter is desorbed; the sol is filtered or centrifuged to recover the concentrated organic matter and S-CN, wherein the recovery rate of the organic matter reaches 90.8%; the organic matter remaining on the surface of the recovered S-CN can be further removed by light to achieve the recycling of the catalyst.
[0053] Example 4
[0054] The present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0055] 1.5 g of melamine, 0.56 g of KOH and 0.2 g of NaOH (molar ratio of 12:10:5) were ground evenly, added into a covered crucible and placed in a muffle furnace, heated to 330°C at 8°C / min in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature after calcination to obtain a yellow-brown solid powder; the obtained powder was dispersed and dissolved in 100 mL of ultrapure water, dialyzed to neutrality in ultrapure water using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa, and the solution was placed in a forced air drying oven and evaporated to dryness at 80°C to obtain S-CN; 20 mg of S-CN was dispersed and dissolved in 8 mL A sol is formed in a 20ppm sulfamethoxazole aqueous solution, CO2 is introduced or a small molecule organic acid is added, and the sol is allowed to stand for 10 minutes, and the sol is converted into a hydrogel; the hydrogel is mechanically squeezed or centrifuged to obtain a supernatant and a dehydrated gel, wherein the removal efficiency of organic matter in the supernatant reaches 95.0%; Ar is then introduced into the dehydrated gel or an alkaline solution is added, the mixture is mixed evenly and allowed to stand for 10 minutes, the gel is converted into a sol, and the adsorbed organic matter is desorbed; the sol is filtered or centrifuged to recover the concentrated organic matter and S-CN, wherein the recovery rate of the organic matter reaches 83.1%; the organic matter remaining on the surface of the recovered S-CN can be further removed by light to achieve the recycling of the catalyst.
[0056] Example 5
[0057] The present invention provides a method for selectively separating and recovering organic matter, comprising the following steps:
[0058] 1.5 g of melamine, 0.56 g of KOH and 0.2 g of NaOH (molar ratio of 12:10:5) were ground evenly, added into a covered crucible and placed in a muffle furnace, heated to 330°C at 8°C / min in an air atmosphere, calcined for 2 h, and naturally cooled to room temperature after calcination to obtain a yellow-brown solid powder; the obtained powder was dispersed and dissolved in 100 mL of ultrapure water, dialyzed to neutrality in ultrapure water using a regenerated cellulose membrane dialysis bag with a molecular weight cutoff of 3.5 kDa, and the solution was placed in a forced air drying oven and evaporated to dryness at 80°C to obtain S-CN; 20 mg of S-CN was dispersed and dissolved in 8 mL A sol is formed in a 100 ppm tetracycline aqueous solution, CO2 is introduced or a small molecule organic acid is added, and the solution is allowed to stand for 10 minutes, and the sol is converted into a hydrogel; the hydrogel is mechanically squeezed or centrifuged to obtain a supernatant and a dehydrated gel, wherein the removal efficiency of organic matter in the supernatant reaches 96.7%; Ar is then introduced into the dehydrated gel or an alkaline solution is added, the mixture is mixed evenly and the solution is allowed to stand for 10 minutes, and the gel is converted into a sol, and the adsorbed organic matter is desorbed; the sol is filtered or centrifuged to recover the concentrated organic matter and S-CN, wherein the recovery rate of the organic matter reaches 85.6%; the organic matter remaining on the surface of the recovered S-CN can be further removed by light irradiation to achieve the recycling of the catalyst.
[0059] according to Figure 1 and Figure 2 The results show that water-soluble carbon nitride has good adsorption removal and desorption recovery performance for hydrophilic organic matter, such as methylene blue, azure B, acridine yellow, sulfamethoxazole and tetracycline. The organic matter adsorption removal rate is above 90%, and the desorption recovery rate is higher than 80%, indicating that this method has high efficiency in purifying and recovering wastewater contaminated by hydrophilic organic matter.
[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.
Claims
1. A method for selective separation and recovery of organic matter, comprising the following steps: A catalyst is added to an organic aqueous solution, ultrasonically dissolved, and then a cross-linking agent is added to mix and stand, and then a pure aqueous solution and a dehydrated gel are obtained by mechanical extrusion or centrifugation, and then the cross-linking agent in the dehydrated gel is removed to release the adsorbed organic matter and return to a sol state, and the sol is filtered or centrifuged to separate the material, and the organic concentrate is collected and the catalyst is recovered for recycling; wherein: The organic substances are methylene blue, acriflavine, azure B, sulfamethoxazole and tetracycline; The catalyst is water-soluble carbon nitride; The cross-linking agent is CO2 or a small molecule organic acid; The method for removing the crosslinking agent in the dehydrated gel is to introduce Ar into the dehydrated gel or add an alkaline solution.
2. The method according to claim 1, wherein: The organic acid includes: formic acid, acetic acid, oxalic acid; The alkaline solution includes: sodium hydroxide solution and potassium hydroxide solution.
3. The method according to claim 1, wherein: The water-soluble carbon nitride is prepared by the following method: (1) mixing melamine and alkali metal hydroxide, grinding them evenly and adding them into a crucible, then placing the crucible into a muffle furnace and sealing it, heating and calcining them in an air atmosphere, and naturally cooling them to room temperature to obtain a first mixture; (2) Dispersing and dissolving the first mixture in water, dialyzing it to neutrality using a dialysis bag, and then evaporating the solution in a forced air drying oven to dryness to obtain a water-soluble carbon nitride with surface functionalized hydrophilic groups amino and hydroxyl.
4. The method according to claim 3, wherein: The molar ratio of melamine to alkali metal hydroxide in step (1) is 12:15; The calcination temperature is 330° C. and the calcination time is 2 h.
5. The method according to claim 4, wherein: The alkali metal hydroxide is a mixture of KOH and NaOH in a molar ratio of 10:
5.
6. The method according to claim 3, wherein: The dialysis bag in step (2) is a regenerated cellulose membrane with a molecular weight cutoff of 3.5 kDa.
7. The method according to claim 1, wherein: The organic matter concentration is 5-100 mg / L, the catalyst concentration is 0.5-5 mg / mL, and the cross-linking agent concentration is not less than 2 mg / mL.
8. The method according to claim 1, wherein: The cross-linking agent is added, mixed and allowed to stand for 10 minutes, and the reaction temperature is 25°C; The operation of removing the cross-linking agent in the dehydrated gel is: mixing and mixing and standing for 10 minutes, and the reaction temperature is 25°C.
9. The method according to claim 1, wherein: The recovered catalyst is irradiated with light to remove residual organic matter on the surface, thereby achieving recycling.