A modified activated carbon, its preparation method and application

Abstract

This invention relates to the fields of environmental and chemical technology, specifically to a nitrogen-modified activated carbon adsorbent material, its preparation method, and its applications. The invention employs an ammonium chloride solution impregnation method combined with high-temperature activation under a nitrogen inert atmosphere to modify the surface of pretreated granular activated carbon, increasing the content of basic groups on the activated carbon surface, thus preparing a nitrogen-modified activated carbon adsorbent material. Experimental results show that the prepared nitrogen-modified activated carbon exhibits high adsorption efficiency for carboxylic acid drug pollutants such as naproxen, ibuprofen, and diclofenac. The preparation conditions of this invention are mild, the operation steps are simple, the required reagents are inexpensive, and the safety is relatively high, making it suitable for the treatment of drinking water, sewage, and medical wastewater.

Description

(I) Technical Field

[0001] This invention relates to a modified activated carbon, its preparation method, and its application, belonging to the field of environmental and chemical technology. (II) Background Technology

[0002] Carboxylic acid drugs typically possess high biological activity and pharmacological effects, and are widely used in the treatment of diseases affecting the immune, cardiovascular, and digestive systems. With the widespread use of carboxylic acid drugs, they are commonly detected in aquatic environments. Carboxylic acid drugs with high detection rates and quantities include ibuprofen, naproxen, and diclofenac. Naproxen and diclofenac, among others, often exhibit endocrine-disrupting effects and developmental toxicity. Residual drugs in water can affect microorganisms in the aquatic environment, disrupt the ecosystem balance, and can also be ingested by humans through drinking water, threatening human health.

[0003] Conventional wastewater and drinking water treatment processes such as activated sludge and coagulation sedimentation have limited effectiveness in removing carboxylic acid drugs. Activated carbon, due to its advantages of large specific surface area, well-developed pore structure, simple operation, and recyclability, shows promising application prospects in removing residual drugs and other micro-pollutants from water bodies. The mechanisms by which activated carbon adsorbs pollutants include hydrophobic interactions, hydrogen bonding, and electrostatic interactions. Because carboxylic acid drugs typically have high water solubility, activated carbon adsorption of these drugs suffers from slow adsorption rates and small adsorption capacities. Modification of activated carbon can be used to directionally improve its pollutant removal efficiency. Common modification methods include acid-base modification, metal / other element loading modification, surface oxidation modification, and surface reduction modification. Furthermore, high-temperature treatment can alter the surface acidity / alkalinity and pore structure of activated carbon. Recent studies have shown that targeted introduction of metal oxides, heteroatoms (S, N, etc.), and inorganic salts onto the activated carbon surface to form surface chemical groups, thereby altering the surface physicochemical properties of activated carbon, can improve the selectivity and efficiency of activated carbon in adsorbing pollutants. Introducing nitrogen-containing functional groups onto the surface of activated carbon can increase the content of basic groups on the activated carbon surface, enhance the electrostatic interaction between activated carbon and carboxylic acid drugs, and thus strengthen the selective adsorption of carboxylic acid drug pollutants by activated carbon. Current nitrogen modification of activated carbon often uses reagents such as nitric acid and ammonia, but safety issues during reagent use limit their application to some extent. Furthermore, high-temperature treatment (>700℃) under an inert gas atmosphere can reduce the content of acidic oxygen-containing groups on the activated carbon surface, thereby increasing the basicity of the activated carbon.

[0004] Therefore, this invention uses an ammonium chloride solution impregnation method to nitrogen-modify activated carbon, and further enhances the selective adsorption capacity of activated carbon for carboxylic acid drugs by high-temperature treatment under a nitrogen atmosphere. (III) Summary of the Invention

[0005] To address the shortcomings of existing activated carbon adsorption materials, this invention provides a method for preparing nitrogen-modified activated carbon using ammonium chloride impregnation and its application, which can produce modified activated carbon materials with good adsorption effects on carboxylic acid drugs such as naproxen, diclofenac, and ibuprofen.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a nitrogen-modified activated carbon adsorbent material, comprising the following steps:

[0008] (1) Pretreatment of activated carbon: Granular activated carbon was used as raw material, washed with deionized water, filtered and placed in a forced-air drying oven (105℃) for 24 hours to dry. The obtained activated carbon was placed in a desiccator for storage.

[0009] (2) Add the pretreated activated carbon to the ammonium chloride solution with a concentration of 2-200 g / L. After mixing, place it in a forced-air drying oven for immersion (105℃) for 24 h. Remove the immersed activated carbon from the forced-air drying oven, filter it, wash it with deionized water until the filtrate is neutral, and place it in a forced-air drying oven for drying (105℃, 24 h).

[0010] (3) Place the dried activated carbon in a tube furnace and heat it under the protection of nitrogen inert atmosphere. Finally, place the nitrogen-modified activated carbon sample in a desiccator for storage.

[0011] According to the present invention, preferably, in step (1), the particle size range of the granular activated carbon is 20-50 mesh.

[0012] According to the present invention, preferably, in step (2), the concentration of ammonium chloride solution is 15-25 g / L, and the mass ratio of activated carbon particles to ammonium chloride is 15-30 g / g.

[0013] According to the present invention, preferably, in step (3), the heating rate of the tubular activation furnace is 10℃ / min, the heat treatment temperature is 700-800℃, and the activation treatment time is 1-3h.

[0014] The raw materials for this invention, granular activated carbon and ammonium chloride, are both commercially available products.

[0015] The nitrogen-modified activated carbon prepared by this invention is an adsorption material, preferably used for the adsorption and removal of carboxylic acid drug pollutants in the treatment of drinking water, sewage, and medical wastewater.

[0016] Compared with existing technologies, this invention modifies activated carbon using an ammonium chloride impregnation method combined with high-temperature treatment under an inert nitrogen atmosphere. By increasing the content of basic groups on the activated carbon surface, it enhances the interaction between activated carbon and negatively charged carboxylic acid drug pollutants, thereby strengthening the adsorption of carboxylic acid drug pollutants by activated carbon. The modified activated carbon material prepared by this invention has mild preparation conditions, simple operation steps, inexpensive reagents, and high safety. Experimental results show that compared with unmodified activated carbon, the modified activated carbon material obtained by this invention has a stronger adsorption capacity for carboxylic acid drug pollutants such as naproxen, ibuprofen, and diclofenac, and can improve the removal of carboxylic acid drug pollutants by activated carbon adsorption processes. (iv) Description of the attached drawings

[0017] Figure 1 This study compares the adsorption effects of nitrogen-modified activated carbon and unmodified activated carbon on naproxen at an initial concentration of 10 mg / L, under a dosage of 100 mg / L.

[0018] Figure 2 This study compares the adsorption effects of nitrogen-modified activated carbon and unmodified activated carbon on ibuprofen at an initial concentration of 10 mg / L under a dosage of 100 mg / L.

[0019] Figure 3 This study compares the adsorption effects of nitrogen-modified activated carbon and unmodified activated carbon on diclofenac at an initial concentration of 10 mg / L under a dosage of 100 mg / L. (V) Detailed Implementation

[0020] The specific embodiments of the present invention are as follows:

[0021] Example

[0022] (1) Activated carbon pretreatment: Coal-based granular activated carbon with a particle size of 20-50 mesh was used as the modified raw material. It was washed with deionized water, filtered, and then placed in a forced-air drying oven (105℃) for 24 hours to dry. The obtained activated carbon was then placed in a desiccator for storage.

[0023] (2) Weigh 1g of ammonium chloride and dissolve it in 50mL of deionized water. Add 20g of cleaned activated carbon to the above ammonium chloride solution, stir and mix, and then place it in a forced-air drying oven for soaking (105℃) for 24h. Take out the soaked activated carbon from the forced-air drying oven, filter it, wash it with deionized water until the filtrate is neutral, and place it in a forced-air drying oven for drying (105℃, 24h).

[0024] (3) Place the dried activated carbon in a tube furnace and heat it to 750°C at a rate of 10°C / min under the protection of nitrogen inert atmosphere. Activate it at 750°C for 2 hours. After activation, store the nitrogen-modified activated carbon sample in a desiccator for later use.

[0025] Application Examples

[0026] The nitrogen-modified activated carbon prepared in the examples was used to treat simulated water samples containing naproxen, ibuprofen, and diclofenac, respectively, and unmodified coal-based activated carbon was used as a control for data comparison and analysis.

[0027] The experimental water samples were prepared as follows: 10 mg of naproxen was weighed into 800 mL of deionized water, an appropriate amount of sodium hydroxide was added, and the mixture was magnetically stirred for 24 hours, then diluted to 1 L to prepare a 10 mg / L naproxen stock solution. 10 mg of ibuprofen was weighed into 800 mL of deionized water, an appropriate amount of sodium hydroxide was added, and the mixture was magnetically stirred for 24 hours, then diluted to 1 L to prepare a 10 mg / L ibuprofen stock solution. 10 mg of diclofenac sodium was weighed into 800 mL of deionized water, and the mixture was magnetically stirred for 24 hours, then diluted to 1 L to prepare a 10 mg / L diclofenac stock solution. During the adsorption experiment, 5 mM borate buffer was added to adjust the pH of the naproxen, ibuprofen, and diclofenac solutions to 8.0 ± 0.1, respectively, to obtain simulated water samples of naproxen, ibuprofen, and diclofenac.

[0028] The nitrogen-modified activated carbon and unmodified activated carbon prepared in the examples were applied to adsorption experiments on simulated water samples containing naproxen, ibuprofen, and diclofenac. The experimental results are shown in Table 1 and Appendix. Figure 1 , 2 As shown in Figure 3.

[0029] Table 1. Pseudo-first-order rate constants for the adsorption of naproxen, ibuprofen, and diclofenac by nitrogen-modified and unmodified activated carbon.

[0030]

[0031] Appendix Figure 1 , 2 The results showed that the adsorption efficiency of nitrogen-modified activated carbon was superior to that of unmodified activated carbon. After 24 hours, the adsorption removal rates of naproxen, ibuprofen, and diclofenac by nitrogen-modified activated carbon (dosage: 100 mg / L) were 88.4%, 46.3%, and 70.2%, respectively, which were 43.8%, 43.1%, and 29.2% higher than those of unmodified activated carbon. Table 1 summarizes the pseudo-first-order rate constants (adsorption time: 8 h) for the adsorption of naproxen, ibuprofen, and diclofenac by nitrogen-modified and unmodified activated carbon. As shown in Table 1, the pseudo-first-order rate constants for the adsorption of naproxen, ibuprofen, and diclofenac by nitrogen-modified activated carbon were 1.9, 1.7, and 1.5 times that of unmodified activated carbon, respectively. These results indicate that the nitrogen-modified activated carbon adsorbent material prepared in this invention has excellent adsorption efficiency for carboxylic acid drug pollutants.

Claims

1. A nitrogen-modified activated carbon for adsorbing carboxylic acid drug pollutants, characterized in that, It consists of a carrier and a loading material; the carrier is activated carbon, and the loading material is ammonium chloride.

2. The nitrogen-modified activated carbon material according to claim 1, characterized in that, The loading amount of the loading material relative to the activated carbon is 0.005-0.5 g / g, preferably 0.03-0.07 g / g.

3. The nitrogen-modified activated carbon material according to claim 1, characterized in that, Ammonium chloride was loaded using the impregnation method (105℃, 24h).

4. The nitrogen-modified activated carbon material according to claim 1, characterized in that, After impregnation, the product is activated by high-temperature treatment. Preferably, the temperature is raised under the protection of a nitrogen inert atmosphere. The heating rate of the tube activation furnace is 10℃ / min, the heat treatment temperature is 700-800℃, and the activation treatment time is 1-3h.

5. A method for preparing nitrogen-modified activated carbon for adsorbing carboxylic acid drug pollutants, comprising the following steps: (1) Using granular activated carbon as raw material, wash with deionized water, filter and dry in a forced-air drying oven (105℃) for 24 hours, and store in a desiccator for later use. (2) Add the activated carbon obtained in step (1) to an ammonium chloride solution with a concentration of 15-25 g / L and a mass ratio of activated carbon particles to ammonium chloride of 15-30 g / g. After mixing, place the activated carbon in a forced-air drying oven for immersion (105℃) for 24 h. Remove the immersed activated carbon from the forced-air drying oven, filter it, wash it with deionized water until the filtrate is neutral, and dry it in a forced-air drying oven (105℃, 24 h). (3) Place the activated carbon obtained in step (2) in a tube furnace and heat it under the protection of nitrogen inert atmosphere. The heating rate of the tube furnace is 10℃ / min, the heat treatment temperature is 700-800℃, the activation treatment time is 1-3h, and finally, place the nitrogen-modified activated carbon sample in a desiccator for storage.

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