Synthesis method of heterocyclic chelating resin and application of heterocyclic chelating resin in mercury-containing waste gas

Abstract

The invention discloses a nitrogen-containing heterocyclic chelating resin, a synthesis method thereof and an application of the nitrogen-containing heterocyclic chelating resin in treatment of mercury-containing waste gas. The resin is prepared by taking chloromethylated polystyrene as a framework and grafting a nitrogen heterocyclic ring functional group through a one-step method. The method has the advantages that the synthesis method is simple, the condition is mild, the cost is low, the product has extremely high adsorption capacity and selectivity on mercury ions, elemental mercury and oxidation-state mercury in industrial mercury-containing waste gas can be effectively removed, the resin can be regenerated through chemical elution, recovery of mercury and recycling of the resin are achieved, and the method is suitable for industrial production. The method has a good application prospect in the field of environmental governance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for synthesizing a heterocyclic chelating resin with high selective adsorption capacity for mercury ions, and the application of the resin in the removal and recovery of industrial mercury-containing waste gas. Background Technology

[0002] Mercury and its compounds are highly toxic pollutants, primarily originating from coal-fired power plants and waste incineration.

[0003] Waste gas generated during non-ferrous metal smelting and chlor-alkali industries. Mercury in the waste gas is mainly elemental mercury (Hg). 0 ), oxidized mercury (Hg) 2+ Mercury exists in the form of mercury and particulate mercury, among which elemental mercury is the most difficult to remove due to its high volatility and poor water solubility.

[0004] The invention patent with patent number CN201810714316.5 provides a method for purifying tail gas from mercury-contaminated soil through indirect thermal desorption. The method includes six steps. By coordinating a multi-stage spray tower group, a condensation device, a gas-liquid separation device, a tail gas treatment device, a circulating water reuse device, and a wastewater treatment device, the temperature in the tail gas can be gradually reduced, thus reducing energy consumption. Placing the tail gas treatment device in a later step can reduce the load on the tail gas treatment device, allowing it to be recycled.

[0005] The invention patent with patent number 202110557056.7 discloses a mercury-containing waste gas purification and mercury recovery system and treatment method. In this invention, after the mercury-containing waste gas enters the spray absorption tower, the elemental mercury in the waste gas is oxidized into ionic mercury and dissolved in the absorption liquid under the combined action of the absorption liquid and the catalytic packing. The absorption liquid is regenerated and recycled by anodic oxidation in the electrocatalytic reactor. The ionic mercury is reduced to elemental mercury by the cathode of the electrocatalytic reactor and is enriched on the cathode surface. When the amount of elemental mercury attached to the cathode surface reaches a certain amount, the cleaning device is activated to clean it, and then the mercury is filtered, separated and recovered.

[0006] Currently, the main methods for treating mercury-containing waste gas include adsorption, absorption, and catalytic oxidation. Activated carbon injection technology is a relatively mature adsorption technology, but it has problems such as limited adsorption capacity, poor adsorption selectivity, high operating costs, and the potential for secondary pollution from spent activated carbon.

[0007] Chelating resins are polymers with specific functional groups that can form stable coordination bonds with specific metal ions, thereby achieving highly selective adsorption and enrichment of target metal ions. Nitrogen-containing heterocyclic compounds (such as imidazoles, triazoles, and tetraazoles) contain nitrogen atoms with lone pairs of electrons, which can bind with Hg... 2+They form stable complexes with soft acid-based metal ions. Therefore, introducing nitrogen-containing heterocyclic groups into the polymer backbone to prepare high-performance mercury adsorption chelating resins has significant research value and application prospects.

[0008] Therefore, developing a novel chelating resin with a simple synthesis method, large adsorption capacity, high selectivity, and suitability for treating mercury-containing waste gas is particularly necessary for environmental governance. Summary of the Invention

[0009] The purpose of this invention is to provide a method for synthesizing heterocyclic chelating resins and their application in mercury-containing waste gas.

[0010] To achieve the objectives of this invention, the technical solution is as follows:

[0011] A method for synthesizing a heterocyclic chelating resin includes the following steps:

[0012] (a) Provide chloromethylated polystyrene resin and pre-treat it with an organic solvent for 2-4 hours to induce swelling; (b) React the pre-treated resin with an excess of a small-molecule nitrogen-containing heterocyclic compound and an inorganic base catalyst in...

[0013] React in an organic solvent at 60-100℃ for 16-24 hours;

[0014] (c) After the reaction is complete, the product is filtered, washed and dried to obtain the heterocyclic chelate resin; preferably, the degree of crosslinking of the chloromethylated polystyrene resin in step (a) is 4%-8%.

[0015] Preferably, the organic solvent in step (a) is N,N-dimethylformamide.

[0016] Preferably, the small molecule nitrogen-containing heterocyclic compound in step (b) is selected from one or more of imidazole, 1,2,4-triazole, and benzimidazole.

[0017] Preferably, the inorganic base catalyst in step (b) is potassium carbonate, sodium carbonate, or sodium hydroxide.

[0018] Preferably, in step (b), the molar ratio of chloromethylated polystyrene resin to small-molecule nitrogen-containing heterocyclic compound is 1:3 to 1:8.

[0019] Based on the same inventive concept, the present invention also provides an application of heterocyclic chelating resin in the treatment of mercury-containing waste gas.

[0020] Preferably, the application of a heterocyclic chelating resin in the treatment of mercury-containing waste gas is as follows: the heterocyclic chelating resin is packed into a fixed-bed adsorption column, and the mercury-containing waste gas is passed through the adsorption column.

[0021] Preferably, the space velocity of the mercury-containing waste gas passing through the adsorption column is 4000-5000 h⁻¹. -¹ .

[0022] Preferably, the resin after adsorption saturation is regenerated by a chemical eluent, wherein the chemical eluent is an acidic solution containing thiourea, an acidic aqueous solution containing thiourea of ​​5-10%, and hydrochloric acid with a concentration of 1 mol / L HCl.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) High selectivity and stability: The nitrogen atom on the imidazole ring in the resin has a lone pair of electrons, while mercury ions (Hg²⁺) and elemental mercury (Hg) 0 All of these are typical soft Lewis acids. According to the soft-hard acid-base theory, they have a very strong affinity for the imidazole nitrogen atom, which is a soft base, and can form stable coordinate bonds.

[0025] (2) High adsorption capacity: By introducing high-density nitrogen-containing heterocyclic groups into the resin skeleton through chemical bonding, a large number of mercury coordination sites are provided, and its saturated adsorption capacity for mercury can reach more than 200 mg / g.

[0026] (3) The resin of the present invention has an excellent collection effect on Hg²⁺ generated after pre-oxidation with an oxidant, and its porous structure also has a good collection effect on Hg in the gas phase. 0 It also has certain physical adsorption and catalytic oxidation adsorption effects, and can effectively treat low-concentration mercury-containing waste gas.

[0027] (4) The synthesis method is simple: the synthesis route is simple, the conditions are mild, the raw materials are readily available, and it is suitable for large-scale production.

[0028] (5) Recyclable: The saturated resin can be regenerated by a simple chemical elution method. It has a long service life, low processing cost, and can enrich and recover mercury, which has good environmental and economic benefits. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments and comparative examples, but these are not intended to limit the present invention.

[0030] Example 1

[0031] 10.0 g (containing approximately 8.0 mmol of chloromethyl) of chloromethylated polystyrene resin (white spheres, 6% crosslinking degree) pre-swollen in DMF for 4 hours was weighed into a 250 mL three-necked flask. 3.0 g (44 mmol) of imidazole and 1.5 g of potassium carbonate were added, followed by 100 mL of DMF as a solvent. The reaction was carried out under nitrogen protection in an oil bath at 80 °C with mechanical stirring for 12 hours. After the reaction, the mixture was cooled and filtered. The resulting resin was washed thoroughly with DMF, deionized water, 1 mol / L HCl, deionized water, and ethanol sequentially. Finally, it was vacuum dried at 60 °C for 12 hours to obtain a pale yellow spherical resin. This resin was used to treat mercury-containing waste gas at a space flow rate of 5000 h⁻¹. -1 The inlet mercury concentration was 1-10 mg / m³, and after treatment by the resin tower, the outlet concentration was 0.003 mg / m³, with a mercury removal rate of more than 99.9%. After the resin was saturated with adsorption, it was eluted with a 1 mol / L HCl solution containing 5% thiourea. After 5 adsorption-desorption cycles, the adsorption capacity of the resin for mercury could still maintain more than 90% of the initial capacity, indicating that it has good regeneration stability.

[0032] Example 2

[0033] 10.0 g (containing approximately 8.0 mmol of chloromethyl) of chloromethylated polystyrene resin (white spheres, 6% crosslinking degree) pre-swollen in DMF for 4 hours was weighed into a 250 mL three-necked flask. 3.0 g (44 mmol) of 1,2,4-triazole and 1.5 g of potassium carbonate were added, followed by 100 mL of DMF as a solvent. The reaction was carried out under nitrogen protection in a 90 °C oil bath with mechanical stirring for 16 hours. After the reaction, the mixture was cooled and filtered. The resulting resin was washed thoroughly with DMF, deionized water, 1 mol / L HCl, deionized water, and ethanol sequentially. Finally, it was vacuum dried at 60 °C for 12 hours to obtain a pale yellow spherical resin. This resin was used to treat mercury-containing waste gas at a space flow rate of 4000 h⁻¹. -1 The inlet mercury concentration was 5-20 mg / m³, and after treatment by the resin tower, the outlet concentration was 0.004 mg / m³, with a mercury removal rate of more than 99.9%. After the resin was saturated with adsorption, it was eluted with a 1 mol / L HCl solution containing 10% thiourea. After 6 adsorption-desorption cycles, the adsorption capacity of the resin for mercury could still maintain more than 90% of the initial capacity, indicating that it has good regeneration stability.

Claims

1. A method for synthesizing a heterocyclic chelating resin, characterized in that, Includes the following steps: (a) Provide chloromethylated polystyrene resin and pre-treat it with an organic solvent for 2-4 hours to induce swelling; (b) Mix the pre-treated resin with an excess of a small-molecule nitrogen-containing heterocyclic compound in an organic solvent. (c) After the reaction is completed, the product is filtered, washed and dried to obtain heterocyclic chelate resin.

2. The method for synthesizing a heterocyclic chelating resin according to claim 1, characterized in that, In step (a), the degree of crosslinking of the chloromethylated polystyrene resin is 4%-8%.

3. The method for synthesizing a heterocyclic chelating resin according to claim 1, characterized in that, The organic solvent in step (a) is N,N-dimethylformamide.

4. The method for synthesizing a heterocyclic chelating resin according to claim 1, characterized in that, The small molecule nitrogen-containing heterocyclic compound mentioned in step (b) is selected from one or more of imidazole, 1,2,4-triazole, and benzimidazole.

5. The method for synthesizing a heterocyclic chelating resin according to claim 1, characterized in that, In step (b), the inorganic base catalyst is potassium carbonate, sodium carbonate, or sodium hydroxide.

6. The method for synthesizing a heterocyclic chelating resin according to claim 1, characterized in that, In step (b), the molar ratio of chloromethylated polystyrene resin to small molecule nitrogen-containing heterocyclic compound is 1:3 to 1:

8.

7. The application of the heterocyclic chelating resin according to claims 1-6 in the treatment of mercury-containing waste gas.

8. The application according to claim 7, characterized in that, The application method is as follows: the heterocyclic chelating resin is packed into a fixed bed adsorption column, and mercury-containing waste gas is passed through the adsorption column.

9. The application according to claim 7, characterized in that, The space velocity of the mercury-containing waste gas passing through the adsorption column is 4000-5000 h⁻¹. - ¹.

10. The application according to claim 9, characterized in that, The resin after adsorption saturation is regenerated by a chemical eluent, which is an acidic aqueous solution containing thiourea (5-10%) and hydrochloric acid (1 mol / L HCl).