Method for preparing zeolite from regenerated activated carbon and improving adsorption capacity of regenerated activated carbon

Abstract

The invention discloses a method for preparing zeolite from regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon. The production of zeolite mainly adopts pure chemical raw materials, the production of an active silicon-aluminum source needs to consume a large amount of energy, and an organic template agent often needs to be added, so that the synthesis cost of the zeolite is relatively high. As the activated carbon contains a large amount of silicon, aluminum and sodium elements and can provide basic elements for synthesis of the zeolite, the zeolite is synthesized by taking the regenerated activated carbon as a raw material without adding a template agent and adopting a hydrothermal synthesis technology, so that a new way is developed for synthesis of the zeolite molecular sieve; meanwhile, when the zeolite is prepared by using a hydrothermal synthesis technology, the problem of blockage of a secondary micropore pore channel of the regenerated activated carbon is solved, and the adsorption capacity of the secondary micropore pore of the regenerated activated carbon is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of zeolite preparation, and in particular relates to a method for preparing zeolite by using regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon with a longer service life. Background Art

[0002] Zeolite molecular sieve has a uniform pore structure, large specific surface area and pore volume, good thermal stability, and strong acidity. Its special structure enables it to have good performance in sieving molecules, adsorption, ion exchange, and catalysis. It has been widely used in petrochemical, environmental protection, bioengineering, food industry, pharmaceutical and chemical industries, etc.

[0003] At present, the production of zeolite is mostly based on purified chemical raw materials, including active silicon source, aluminum source, and sodium source. The production of active silicon and aluminum sources consumes a lot of energy, and often requires the addition of organic templates, resulting in a high cost for zeolite synthesis. Therefore, if zeolite can be produced directly with non-purified chemical raw materials, the production cost of zeolite can be effectively reduced.

[0004] Activated carbon is widely used in the field of water treatment. Due to its generally long service life, even activated carbon that has been regenerated still has problems with pollutant content (especially aluminum salts, silicate and other substances) and blockage of sub-micropore channels.

[0005] Therefore, if a method can be developed to directly prepare zeolite using regenerated activated carbon as raw material while also improving the adsorption capacity of the sub-micropores of the regenerated activated carbon, it will not only reduce the cost of zeolite production, but also maximize the utilization of the effective resources of regenerated activated carbon. Summary of the invention

[0006] The present invention aims to provide a method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon. Considering that activated carbon contains a large amount of silicon, aluminum and sodium elements, which can provide basic elements for zeolite synthesis, the regenerated activated carbon is used as a raw material, and no template is added. The zeolite is synthesized by hydrothermal synthesis technology, which develops a new way for the synthesis of zeolite molecular sieves. At the same time, when the zeolite is prepared by using the hydrothermal synthesis technology, the blockage problem of the sub-micropore channels of the regenerated activated carbon is also solved, thereby improving the adsorption capacity of the sub-micropores of the regenerated activated carbon.

[0007] The method of preparing zeolite by regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon of the present invention comprises the following steps:

[0008] Step 1: Use acid leaching to treat the regenerated activated carbon, so that the sodium silicate and part of the sodium aluminate in the regenerated activated carbon react with acid to generate silicic acid and aluminum chloride respectively, and make the pH value of the solution containing the regenerated activated carbon after the reaction within the range of 7 to 8.

[0009] Step 2: Add deionized water to the regenerated activated carbon solution treated by acid leaching in step 1 and heat it to react, so that silicic acid is hydrolyzed to generate silicon dioxide, and sodium aluminate and aluminum chloride are reacted to generate aluminum hydroxide; after the reaction is completed, separation and purification are performed to obtain a filtrate containing a mixture of silicon dioxide and aluminum hydroxide and regenerated activated carbon with impurities in the sub-microporous pore channels cleaned up.

[0010] Step 3: placing the filtrate obtained in step 2 in a closed space for crystallization reaction.

[0011] Step 4: Filter the reaction mixture obtained from the crystallization reaction in step 3 to obtain zeolite.

[0012] Preferably, the regenerated activated carbon taken in step one is obtained by regenerating saturated activated carbon through the following steps: drying the saturated activated carbon using a drying device, and then regenerating the dried saturated activated carbon to remove gas and adsorbate to obtain regenerated activated carbon.

[0013] More preferably, the drying time is 1.5 hours and the regeneration time is 50 minutes.

[0014] Preferably, the acid used in the acid leaching method in step 1 is hydrochloric acid, wherein the ratio of the amount of acid used to the amount of regenerated activated carbon used is 18 mL:10 g.

[0015] Preferably, in step 2, the mass ratio of the regenerated activated carbon solution to deionized water is 1:7, and the heating reaction conditions are: 90-150° C. and the time is 1-2 h.

[0016] Preferably, in step three, the crystallization temperature is 90-150°C.

[0017] Preferably, in step three, the crystallization time is 3 to 6 hours.

[0018] Preferably, there is further provided a step five of washing the regenerated activated carbon obtained in step two from which impurities in the sub-microporous pore channels have been cleaned.

[0019] More preferably, there is further provided a step six, measuring the methylene blue adsorption value of the regenerated activated carbon after washing in step five, and using the methylene blue adsorption value to characterize the adsorption capacity of the sub-micropores of the regenerated activated carbon.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention uses regenerated activated carbon as raw material to prepare zeolite using hydrothermal synthesis technology. It only consumes the substances adsorbed by the activated carbon without affecting its own adsorption characteristics. The used activated carbon can still be used in the adsorption field. Therefore, this method greatly reduces the cost of preparing zeolite and effectively realizes the resource utilization of activated carbon. In addition, the present invention does not use template structure guidance, which meets the development requirements of green chemistry. In the field of zeolite preparation, there is no precedent for successfully synthesizing zeolite using regenerated activated carbon as raw material.

[0022] 2. In the process of preparing zeolite of the present invention, the regenerated activated carbon is also subjected to acid washing and water bath heating treatment. The methylene blue adsorption value of the regenerated activated carbon after these treatments is more than twice that before the water bath heating treatment, and the adsorption performance is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart of the method of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the zeolite prepared in the embodiment of the present invention.

[0025] Figure 3 for Figure 2 Enlarged view of the dotted box part.

[0026] Figure 4 This is a comparison chart of the methylene blue adsorption values ​​of the regenerated activated carbon before and after water bath heating treatment in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be fully and detailed described below in conjunction with the accompanying drawings in the present invention.

[0028] like Figure 1 As shown, the method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon comprises the following steps:

[0029] Step 1, take saturated activated carbon and put it into a rotary drying device, dry it at 230 ° C for 1.5 hours, and after drying, regenerate the saturated activated carbon using a low-pressure arc regeneration device, wherein the regeneration temperature is set to 800 ° C, and the regeneration time is 50 minutes. During the regeneration process, the silicon and aluminum elements contained in the saturated activated carbon react with the sodium element contained to generate sodium silicate and sodium metaaluminate that are easily soluble in water, providing raw materials for synthetic zeolite. After regeneration is completed, the activated carbon to be regenerated is cooled to room temperature, and the regenerated activated carbon (the present embodiment retains part of the regenerated activated carbon for determination of the methylene blue adsorption value of the regenerated activated carbon without water bath heating) is put into an electric constant temperature drying oven, and the regenerated activated carbon is dried at 150 ° C for 2 hours.

[0030] Step 2: Treat the regenerated activated carbon obtained in step 1 with hydrochloric acid, so that the sodium silicate and part of the sodium aluminate in the regenerated activated carbon react with the hydrochloric acid to generate silicic acid and aluminum chloride, respectively. The ratio of hydrochloric acid to regenerated activated carbon is 18 mL: 10 g, so that the pH value of the solution containing the regenerated activated carbon after the reaction is within the range of 7 to 8. After this step, the solution is substantially free of alkaline substances.

[0031] Step 3: Evenly mix the solution containing regenerated activated carbon in step 2 and deionized water in a mass ratio of 1:7, and then place it in a resistance furnace for heating reaction at 95°C for 90 minutes, so that the silicic acid is hydrolyzed at high temperature to generate silicon dioxide, and sodium aluminate and aluminum chloride react to generate aluminum hydroxide under the action of high temperature and water; filter the reaction mixture into a conical flask to obtain a filtrate with an aluminum-silicon mixture (a mixture of silicon dioxide and aluminum hydroxide), and obtain regenerated activated carbon with impurities in the sub-microporous pore channels cleaned up.

[0032] Step 4: Place the filtrate obtained in step 3 in a closed space for crystallization reaction at a temperature of 90 to 150° C. for 3 to 6 hours.

[0033] Step 5: After the crystallization reaction is completed, the reaction mixture obtained in step 4 is filtered again to obtain zeolite. The scanning electron microscope image of the prepared zeolite is shown in FIG. Figure 2 and Figure 3 .

[0034] Step six, washing the regenerated activated carbon that has been treated with water bath heating (step three).

[0035] Step 7. The methylene blue adsorption value is a performance index to characterize the adsorption capacity of regenerated activated carbon. The diameter of methylene blue molecules is between 1.1 and 2.2 nm, and the sub-micropores of activated carbon are between 2 and 50 nm. Therefore, methylene blue molecules are easily adsorbed by the sub-micropores of regenerated activated carbon. According to the test method for coal-based granular activated carbon recorded in [National Standard GB / T7702.6--2008] - Determination of methylene blue adsorption value, the methylene blue adsorption values ​​of regenerated activated carbon that has not been heated in a water bath (the regenerated activated carbon retained in step 1 is dried at 150°C for 2 hours, and then treated in step 2 to obtain a solution containing regenerated activated carbon, and the solution is filtered to obtain regenerated activated carbon that has not been heated in a water bath) and regenerated activated carbon that has been heated in a water bath are measured and compared after washing with water.

[0036] The specific implementation steps for measuring the methylene blue adsorption value of the regenerated activated carbon that has not been heated in a water bath or the regenerated activated carbon that has been heated in a water bath and washed with water are as follows:

[0037] (i) Take 10g of the regenerated activated carbon sample, grind it to the extent that more than 90% can pass through a 0.045mm test sieve, mix the sieve residue with it (other parts except the sieve residue), dry it in an electric constant temperature drying oven at 150±5℃ for 2h, and place it in a desiccator to cool.

[0038] (ii) Weigh 0.1 g of the sample treated in step (i) to an accuracy of 0.0001 g and place it in a 100 mL conical flask. Use a burette to add 7 mL of methylene blue solution, cover the flask tightly with the stopper, and place it in a water bath constant temperature oscillator for 30 min.

[0039] (iii) filtering the methylene blue solution adsorbed by the sample in step (ii) into a colorimetric tube, mixing well, and obtaining a filtrate.

[0040] (iv) Using a 10 mm cuvette at a wavelength of 665 mm and water as a reference solution, measure the absorbance of the filtrate. If the difference between the absorbance of the filtrate and the absorbance of the copper sulfate standard solution is within the range of ±0.020, directly proceed to step (vi); otherwise, proceed to step (v).

[0041] (V) Return to step (B) and adjust the volume of the methylene blue solution added during step (B).

[0042] (VI) Calculate the methylene blue adsorption value as follows:

[0043]

[0044] Wherein: E is the adsorption value of methylene blue, in milligrams per gram; ρ is the concentration of methylene blue solution, in milligrams per milliliter; V is the volume of methylene blue solution consumed by the test sample, in milliliters; m is the mass of the sample weighed in step (ii), in grams.

[0045] According to the above-mentioned measurement of the methylene blue adsorption value of the regenerated activated carbon without water bath heating and the regenerated activated carbon heated in a water bath after washing, the calculated results of the methylene blue adsorption value of the two regenerated activated carbons are compared as shown in Figure 4 .

Claims

1. A method for preparing zeolite by regenerated activated carbon and improving the adsorption capacity of the regenerated activated carbon, characterized in that: The specific steps are as follows: Step 1: Treat the regenerated activated carbon by acid leaching, so that the sodium silicate and part of the sodium aluminate in the regenerated activated carbon react with the acid to generate silicic acid and aluminum chloride, respectively, and make the pH value of the solution containing the regenerated activated carbon after the reaction be in the range of 7 to 8; Step 2: mixing deionized water into the regenerated activated carbon solution treated by the acid leaching method in step 1 and heating the solution to hydrolyze silicic acid to generate silicon dioxide, and react sodium aluminate and aluminum chloride to generate aluminum hydroxide; after the reaction is completed, separation and purification are performed to obtain a filtrate containing a mixture of silicon dioxide and aluminum hydroxide and regenerated activated carbon with impurities in the sub-micropore channels cleaned; Step 3, placing the filtrate obtained in step 2 in a closed space for crystallization reaction; Step 4: Filter the reaction mixture obtained from the crystallization reaction in step 3 to obtain zeolite.

2. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: Step 1: The regenerated activated carbon is obtained by regenerating the saturated activated carbon through the following steps: drying the saturated activated carbon using a drying device, and then regenerating the dried saturated activated carbon to remove gas and adsorbate to obtain regenerated activated carbon.

3. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 2, characterized in that: The drying time is 1.5 hours, and the regeneration time is 50 minutes.

4. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: The acid used in the acid leaching method in step 1 is hydrochloric acid, wherein the ratio of the amount of acid used to the amount of regenerated activated carbon used is 18 mL: 10 g.

5. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: In step 2, the mass ratio of the regenerated activated carbon solution to deionized water is 1:7, and the heating reaction conditions are: 90-150° C. and the time is 1-2 hours.

6. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: In step three, the crystallization temperature is 90-150°C.

7. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: In step 3, the crystallization time is 3 to 6 hours.

8. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 1, characterized in that: There is also a step five of washing the regenerated activated carbon obtained in step two from which impurities in the sub-micropore channels have been cleaned.

9. The method for preparing zeolite with regenerated activated carbon and improving the adsorption capacity of regenerated activated carbon according to claim 8, characterized in that: There is also a step six, measuring the methylene blue adsorption value of the regenerated activated carbon after washing in step five, and using the methylene blue adsorption value to characterize the adsorption capacity of the sub-micropores of the regenerated activated carbon.

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