Composite adsorption material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adsorption materials, and particularly relates to a composite adsorption material as well as a preparation method and application thereof. The composite adsorption material comprises an alkaline activated carbon layer, a molecular sieve layer and an indicator layer which are sequentially stacked, the alkaline activated carbon layer comprises activated carbon and alkaline substances loaded on the activated carbon. Through the combined action of the alkaline activated carbon layer and the molecular sieve layer, the adsorbent has a good adsorption effect on acidic substances, and has good chemical stability and mechanical strength. When the adsorbed acidic material reaches a certain concentration, the molecular sieve structure collapses, the acid liquid permeates into the indicator layer, the indicator layer can visually display the adsorption state, and if the indicator layer has corresponding color change, the adsorption material is invalid and needs to be replaced in time.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption materials, and in particular relates to a composite adsorption material and a preparation method and application thereof. Background Art

[0002] Acid is a common chemical reagent in laboratories. Laboratory acid storage environments, such as concentrated sulfuric acid tanks and hydrofluoric acid workstations, often generate acid mist. When strong acids are stored in acid or reagent cabinets and evaporate, the accumulated acid can adhere to the interior of the cabinet, corroding it and severely shortening its service life. Acid mist can also be harmful to the laboratory environment and human health.

[0003] To address these issues, conventional technologies use adsorbent materials to absorb acid mist. Activated carbon is a commonly used adsorbent, which has a certain adsorption capacity. However, conventional activated carbon used in existing technologies has a low adsorption capacity (less than 200 mg / g) and is sensitive to humidity. Studies have also used diatomaceous earth composites for adsorption, but at pH values ​​below 1, the structural disintegration rate of diatomaceous earth composites can reach as high as 35%, resulting in poor chemical stability and an inability to reliably address the issue of acid mist release. Furthermore, with current adsorption products, it's impossible to determine when their structure will fail, making it difficult to accurately determine when to replace the adsorption product, and consequently, unable to guarantee stable adsorption of acids from the environment.

[0004] Therefore, it is of great significance to provide a composite adsorption material with good adsorption capacity, chemical stability, and intuitive understanding of the adsorption state. Summary of the Invention

[0005] The present invention aims to address one or more of the above-mentioned technical problems in the prior art and to provide at least a beneficial alternative. Specifically, the present invention provides a composite adsorbent material having excellent adsorption capacity, chemical stability, and mechanical properties, and allowing intuitive monitoring of the adsorption status for timely replacement.

[0006] The inventive concept of the present invention: The composite adsorption material of the present invention comprises an alkaline activated carbon layer, a molecular sieve layer and an indicator layer stacked in sequence; the alkaline activated carbon layer comprises activated carbon and an alkaline substance loaded on the activated carbon. The alkaline activated carbon layer has a good adsorption effect on acidic substances, and the molecular sieve layer can play a buffering role in microporous adsorption of acidic molecules, delaying the penetration of acidic solution into the indicator layer, balancing the acid response speed and structural stability. The two work together to have a good adsorption effect on acidic substances, and have good chemical stability and mechanical strength. When the adsorbed acidic substance reaches a certain concentration, the molecular sieve structure collapses, allowing the acidic solution to penetrate into the indicator layer. The indicator layer can intuitively display the adsorption state. If the indicator layer undergoes a corresponding color change, it means that the adsorption material has failed, and the adsorption material needs to be replaced in time to avoid the adsorption material being in use after failure, thereby ensuring good adsorption of acid mist.

[0007] Therefore, a first aspect of the present invention provides a composite adsorbent material.

[0008] Specifically, the composite adsorption material includes an alkaline activated carbon layer, a molecular sieve layer and an indicator layer stacked in sequence;

[0009] The alkaline activated carbon layer includes activated carbon and alkaline substances supported on the activated carbon.

[0010] Preferably, the activated carbon includes at least one of coal-based activated carbon, coconut shell activated carbon and wood-based activated carbon.

[0011] Preferably, the alkaline substance includes at least one of Ca(OH)2, KOH, MgO and ZnO-Al2O3 complex.

[0012] Preferably, in the ZnO-Al2O3 composite, the mass ratio of Zn to Al is 1:(0.8-1.2); further preferably, in the ZnO-Al2O3 composite, the mass ratio of Zn to Al is 1:(0.9-1.1); further preferably, in the ZnO-Al2O3 composite, the mass ratio of Zn to Al is 1:1.

[0013] Preferably, the activated carbon is activated carbon that has been activated.

[0014] Preferably, the porosity of the activated carbon after activation treatment is ≥85%.

[0015] Preferably, the loading amount of the alkaline substance in the alkaline activated carbon layer is 10-25 wt %; further preferably, the loading amount of the alkaline substance in the alkaline activated carbon layer is 10-22 wt %.

[0016] Preferably, the molecular sieve layer includes acid-responsive molecular sieve.

[0017] Preferably, the molecular sieve is selected from at least one of the following:

[0018] a) Type A molecular sieve (LTA type, SiO2 / Al2O3=1-2);

[0019] b) X-type molecular sieve (FAU type, Si / Al=1.0-1.5);

[0020] c) M-type molecular sieves (ZSM-5 molecular sieve, MCM-41 mesoporous molecular sieve (pore size 3-5 nm)).

[0021] Specifically, when the A-type molecular sieve (LTA type) is in sulfuric acid or hydrochloric acid with a pH value less than 3, the Al-O bond of the skeleton breaks, resulting in structural collapse; when the X-type molecular sieve (FAU type) comes into contact with concentrated nitric acid, the cations (such as Ca 2+ ) dissolves and the skeleton collapses; when the wall thickness of M-type molecular sieves, such as ZSM-5 molecular sieves and mesoporous molecular sieves (such as MCM-41), is only 1-2nm, the condensation of silanol (Si-OH) under acidic conditions causes collapse.

[0022] Preferably, the molecular sieve layer may be one layer or multiple layers.

[0023] Preferably, the indicator layer comprises a substrate and an indicator located on the substrate.

[0024] Preferably, the substrate includes any one of a PP / PET composite non-woven fabric and a PET substrate.

[0025] Preferably, the indicator comprises a pH-sensitive indicator.

[0026] Preferably, the indicator comprises any one of a mixture of bromocresol purple and methyl red, a mixture of bromocresol green and methyl red, methyl orange, Alizarin Red S, and bromocresol purple.

[0027] Preferably, the thickness of the alkaline activated carbon layer is 3-5 mm.

[0028] Preferably, the pore size of the activated carbon in the alkaline activated carbon layer is 0.5-50 nm, including micropores (<2 nm) and mesopores (2-50 nm).

[0029] Preferably, the thickness of the molecular sieve layer is 60 μm-1 mm.

[0030] Specifically, the thickness of the molecular sieve layer must ensure its buffering function, and the specific value can be determined through routine experiments.

[0031] Preferably, the pore size of the molecular sieve in the molecular sieve layer is 0.4-5 nm.

[0032] Specifically, type A molecular sieve: 0.4 nm (LTA type, SiO2 / Al2O3=2, molar ratio);

[0033] X-type molecular sieve: 0.9 nm (FAU type, Si / Al=1.0, molar ratio);

[0034] MCM-41 mesoporous molecular sieve: pore size 3-5nm.

[0035] Preferably, the thickness of the indicator layer is 20-40 μm.

[0036] The second aspect of the present invention provides a method for preparing the composite adsorption material according to the first aspect of the present invention.

[0037] Specifically, the preparation method of the composite adsorption material comprises the following steps:

[0038] The alkaline activated carbon layer, the molecular sieve layer and the indicator layer are stacked in sequence to obtain the composite adsorption material.

[0039] Preferably, the preparation process of the alkaline activated carbon layer is as follows: the activated carbon is activated and then loaded with alkaline substances, and then laid to obtain the alkaline activated carbon layer.

[0040] Preferably, the activation treatment process is to mix the activating agent and activated carbon and then perform heat treatment.

[0041] Preferably, the activator includes at least one of carbon dioxide, KOH, and phosphoric acid.

[0042] Specifically, if the activated carbon is coal-based activated carbon, carbon dioxide is used as the activating agent; if the activated carbon is coconut shell activated carbon, KOH is used as the activating agent; if the activated carbon is wood-based activated carbon, phosphoric acid is used as the activating agent.

[0043] Preferably, the alkaline substance loading method includes any one of impregnation, atomic deposition, and sol-gel.

[0044] Preferably, when the activated carbon is coal-based activated carbon, the activation treatment process is to introduce CO2 into the coal-based activated carbon for activation.

[0045] Preferably, the activation temperature is 800-900°C, and the activation time is 3-5h; further preferably, the activation temperature is 820-880°C, and the activation time is 3.5-4.5h; even further preferably, the activation temperature is 850°C, and the activation time is 4h.

[0046] Specifically, the surface area of ​​coal-based activated carbon can be increased to 1100m 2 / g, improving its physical adsorption capacity.

[0047] Preferably, the process of loading the activated coal-based activated carbon with the alkaline substance is to immerse the activated coal-based activated carbon in the alkaline substance, dry it, and complete the loading.

[0048] Preferably, the alkaline substance comprises Ca(OH)2.

[0049] Preferably, when the activated carbon is coconut shell activated carbon, the activation treatment process is to mix KOH and coconut shell activated carbon and heat them to perform activation treatment.

[0050] Preferably, the mass ratio of KOH to coconut shell activated carbon is (2.5-3.5):1; further preferably, the mass ratio of KOH to coconut shell activated carbon is (2.7-3.3):1; further preferably, the mass ratio of KOH to coconut shell activated carbon is 3:1.

[0051] Preferably, the heating temperature is 650-750°C, and the heating time is 0.5-2.5h; further preferably, the heating temperature is 680-730°C, and the heating time is 1.0-2.0h; even further preferably, the heating temperature is 700°C, and the heating time is 1.5h.

[0052] Specifically, the coconut shell activated carbon can be significantly increased in specific surface area to 1250m 2 / g, thereby improving the adsorption performance.

[0053] Preferably, the process of loading the alkaline substance on the activated coconut shell activated carbon after the activation treatment is to load the alkaline substance on the surface of the activated coconut shell activated carbon by using an atomic deposition method.

[0054] Preferably, the alkaline substance includes MgO.

[0055] Preferably, after loading MgO, an MgO layer is obtained, and the thickness of the MgO layer is 1.8-3.3 nm; more preferably, the thickness of the MgO layer is 2-3 nm.

[0056] Preferably, when the activated carbon is wood activated carbon, the activation treatment process is to mix phosphoric acid and wood activated carbon, carbonize them, and complete the activation treatment.

[0057] Preferably, the liquid-solid ratio of the phosphoric acid and the wood activated carbon is (2.5-3.5):1; further preferably, the liquid-solid ratio of the phosphoric acid and the wood activated carbon is (2.7-3.3):1; further preferably, the liquid-solid ratio of the phosphoric acid and the wood activated carbon is 3:1.

[0058] Preferably, the carbonization temperature is 400-500°C, and the carbonization time is 2-4h. Further preferably, the carbonization temperature is 430-480°C, and the carbonization time is 2.5-3.5h. Even more preferably, the carbonization temperature is 450°C, and the carbonization time is 3h.

[0059] Specifically, the wood activated carbon can be significantly increased in specific surface area by heating and activation treatment, so that the specific surface area of ​​the wood activated carbon reaches 850m 2 / g, thereby improving the adsorption performance.

[0060] Preferably, the process of loading the alkaline substance on the activated wood activated carbon after the activation treatment is to load the alkaline substance on the surface of the activated wood activated carbon by a sol-gel method.

[0061] Preferably, the alkaline substance comprises a ZnO-Al2O3 complex.

[0062] Preferably, the molecular sieve layer is prepared by spraying the molecular sieve on the alkaline activated carbon layer to obtain the molecular sieve layer.

[0063] Specifically, for type A molecular sieve or type M molecular sieve, in-situ crystallization treatment is required to optimize the crystal structure; for multilayer composite molecular sieve, direct spraying can meet the performance requirements due to the presence of a PEG sacrificial layer between the layers.

[0064] Preferably, when coal-based activated carbon is used, the molecular sieve in the molecular sieve layer is selected from type A molecular sieve, and the type A molecular sieve needs to undergo in-situ crystallization treatment.

[0065] Preferably, the sprayed molecular sieve is placed in a tube furnace for heating and heat preservation to perform the in-situ crystallization treatment and optimize the crystal structure of the molecular sieve.

[0066] Preferably, the heating temperature rise rate is 4-6°C / min, further preferably, the heating temperature rise rate is 4.5-5.5°C / min; further preferably, the heating temperature rise rate is 5°C / min.

[0067] Preferably, the holding temperature is 350-450°C for 3-4 hours; more preferably, the holding temperature is 380-430°C for 3.5-4.5 hours; and even more preferably, the holding temperature is 400°C for 4 hours. In-situ crystallization is performed by holding at a certain temperature, and nitrogen protection is used during the holding process.

[0068] Preferably, the molecular sieve precursor solution is sprayed on the surface of the alkaline activated carbon layer, and the loading amount of the molecular sieve after spraying is 15-25wt% (relative to the mass of the alkaline activated carbon layer); further preferably, the loading amount of the molecular sieve after spraying is 18-22wt%; further preferably, the loading amount of the molecular sieve after spraying is 20wt%.

[0069] Preferably, when coconut shell activated carbon is used, the molecular sieve layer comprises three layers: the upper, middle, and lower molecular sieves are M-type, X-type, and A-type molecular sieves, respectively. The upper layer is first sprayed onto the alkaline activated carbon layer. Different types of molecular sieves have different pore sizes and adsorption properties. Their combination can adsorb pollutants of varying sizes and properties.

[0070] Preferably, the three molecular sieves are sprayed in sequence by a layer-by-layer spraying method to obtain three molecular sieve layers, and polyethylene glycol (PEG) is used as a sacrificial layer between the layers, so as to ensure the relative independence and stability of each layer.

[0071] Preferably, the thickness of each of the three molecular sieve layers is 20-50 μm.

[0072] Preferably, the loading amount of the molecular sieve is 15-25 wt%; further preferably, the loading amount of the molecular sieve is 18-22 wt%; further preferably, the loading amount of the molecular sieve is 20 wt% to ensure that the molecular sieve layer has good adsorption performance.

[0073] Preferably, when wood activated carbon is used, the molecular sieve in the molecular sieve layer is selected from M-type molecular sieve.

[0074] Preferably, the molecular sieve layer is prepared by pre-treating the M-type molecular sieve, adding the coupling agent, heating in a water bath, centrifuging, taking the solid, spraying it on the alkaline activated carbon layer, and in-situ crystallizing to obtain the molecular sieve layer.

[0075] Preferably, the pretreatment temperature is 90-130°C for 1-3 hours, and more preferably, the pretreatment temperature is 100-120°C for 1.5-2.5 hours. Pretreatment removes adsorbed water on the surface of the molecular sieve and improves its reactivity with the coupling agent.

[0076] Preferably, the coupling agent is a coupling agent solution, and the usage ratio of the M-type molecular sieve to the coupling agent solution is 1g:(8-12)mL; further preferably, the usage ratio of the M-type molecular sieve to the coupling agent solution is 1g:(9-11)mL; even further preferably, the usage ratio of the M-type molecular sieve to the coupling agent solution is 1g:10mL.

[0077] Preferably, the water bath heating temperature is 50-70°C, and the water bath heating time is 25-35 minutes; further preferably, the water bath heating temperature is 55-65°C, and the water bath heating time is 27-33 minutes; further preferably, the water bath heating temperature is 60°C, and the water bath heating time is 30 minutes.

[0078] Preferably, stirring is performed during the water bath heating process, and the stirring speed is 180-330 rpm; further preferably, the stirring speed is 200-300 rpm.

[0079] Preferably, stirring is performed by magnetic stirring or mechanical stirring.

[0080] Preferably, after the spraying, the loading amount of the molecular sieve is 10-20%; further preferably, the loading amount of the molecular sieve is 13-17%; further preferably, the loading amount of the molecular sieve is 15%.

[0081] Preferably, the in-situ crystallization process is the same as the in-situ crystallization process of the above-mentioned type A molecular sieve.

[0082] Preferably, the indicator layer is prepared by coating the indicator on the substrate to obtain the indicator layer.

[0083] A third aspect of the present invention provides an adsorption system.

[0084] Specifically, the adsorption system includes the composite adsorption material described in the first aspect of the present invention.

[0085] Preferably, the adsorption system further comprises a housing.

[0086] Preferably, the shell wraps the composite adsorption material as a whole, and a hole is provided on the shell corresponding to one side of the alkaline activated carbon layer in the composite adsorption material.

[0087] Preferably, the shell corresponding to one side of the indicator layer is colorless and transparent to facilitate observation.

[0088] The acid mist first enters the alkaline activated carbon layer through the pores, where it comes into contact with the alkaline activated carbon layer and adsorbs the acid mist. The molecular sieve layer then balances the acid response speed with structural stability, acting as a buffer and assisting adsorption. Together, these two layers achieve full adsorption of the acidic substance. When the adsorbed acid reaches a certain concentration, the molecular sieve structure collapses, allowing the acid to penetrate into the indicator layer. If the indicator layer changes color accordingly, it indicates that the adsorption material has failed and needs to be replaced promptly.

[0089] Preferably, a polytetrafluoroethylene (PTFE) hydrophobic membrane is further provided between the alkaline activated carbon layer and the corresponding shell, and the PTFE hydrophobic membrane is provided with holes.

[0090] Preferably, the pores on the PTFE hydrophobic membrane have a smaller pore size than the pores on the shell, so that the acidic substances entering the shell can slowly and fully contact with the alkaline activated carbon layer, thereby completing sufficient adsorption.

[0091] Preferably, the assembly method of the adsorption system is: hot-pressing and compounding the alkaline activated carbon layer, molecular sieve layer and indicator layer to form an adsorption module, and then placing the adsorption module in a shell, and sealing the shell and the adsorption module by ultrasonic welding to prevent acid mist leakage and ensure the overall performance of the adsorption module.

[0092] Preferably, the hot pressing temperature is 170-190°C, and the hot pressing pressure is 2.5-3.5 MPa; further preferably, the hot pressing temperature is 175-185°C, and the hot pressing pressure is 2.7-3.3 MPa; even more preferably, the hot pressing temperature is 180°C, and the hot pressing pressure is 3 MPa.

[0093] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0094] (1) The alkaline activated carbon layer of the present invention has a good adsorption effect on acidic substances. The molecular sieve layer can play a buffering role in microporous adsorption of acidic molecules, delaying the penetration of acid into the indicator layer, balancing the acid response speed and structural stability, and has a good adsorption effect on acidic substances. It also has good chemical stability and mechanical strength. When the adsorbed acidic substance reaches a certain concentration, the molecular sieve structure collapses, allowing the acid to penetrate into the indicator layer. The indicator layer can intuitively display the adsorption state. If the indicator layer undergoes a corresponding color change, it means that the adsorption material has failed and needs to be replaced in time.

[0095] (2) The present invention can utilize different types of activated carbon (coal slag, coconut shell, wood), combined with various molecular sieves (H-ZSM-5, MCM-41, Ca-X, NaA) and indicators (bromocresol purple, methyl orange, bromocresol green, methyl red, etc.), providing a variety of options for adsorption and indication functions in different application scenarios. In addition, coal slag-based activated carbon is a relatively inexpensive material, which can achieve adsorption function while reducing costs, making it suitable for large-scale applications.

[0096] (3) The composite adsorption material and adsorption system of the present invention are compatible with many brands of acid cabinets or fume hoods without the need to modify the infrastructure; and can be replaced in a manner similar to that of ordinary storage boxes. When the composite adsorption material fails, the composite adsorption material can be directly replaced, which is easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1 Schematic diagram of the structure of the adsorption system of Example 1.

[0098] Among them, 1 is the upper cover, 2 is the base, 3 is the alkaline activated carbon layer, 4 is the molecular sieve layer, and 5 is the indicator layer. DETAILED DESCRIPTION

[0099] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0100] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0101] Example 1

[0102] A composite adsorption material, comprising a Ca(OH)2-loaded coal slag-based activated carbon layer, a NaA-type molecular sieve layer, and an indicator layer stacked sequentially from top to bottom;

[0103] The thickness of the Ca(OH)2-loaded coal slag-based activated carbon layer was 3.0 mm, and the Ca(OH)2 loading was 20 wt%;

[0104] The thickness of the NaA type molecular sieve layer is 0.5 mm, and the SiO2 / Al2O3 in the molecular sieve layer is 2 (molar ratio);

[0105] The indicator layer consists of a substrate and an indicator, bromocresol purple is the indicator, the substrate is a PET substrate, and the thickness is 30 μm.

[0106] Example 1 A method for preparing a composite adsorption material comprises the following steps:

[0107] (1) Preparation of alkaline activated carbon layer:

[0108] S1: Material selection: coal slag activated carbon (coal-based activated carbon) is selected, with a fixed carbon content of 85% and a particle size of 200 mesh. The particle size of 200 mesh can ensure a suitable specific surface area and adsorption channels;

[0109] S2: Activation treatment, using CO2 activation method, the coal slag activated carbon is placed in a specific environment with a CO2 flow rate of 50mL / min, and activated continuously at 850℃ for 4h. This process can significantly increase the specific surface area of ​​the coal slag activated carbon to 1100m 2 / g, improving its physical adsorption capacity;

[0110] S3: Alkaline loading, immersing the activated coal slag carbon in a 15% (mass fraction) Ca(OH)2 solution (pH = 12) to load Ca(OH)2 on the surface of the activated coal slag carbon, then drying at 120°C, and passing through a 200-mesh sieve to ensure that the coal slag activated carbon particles are uniform and have a good loading effect. Alkaline loading can enhance the neutralization ability of acidic substances; using mercury intrusion testing to test the porosity of the activated carbon, ensure that it reaches 85%, ensuring that it has sufficient pores for adsorbing acid mist; finally, the treated activated carbon is laid into an alkaline activated carbon layer with a thickness of 3 mm;

[0111] (2) Preparation of molecular sieve layer:

[0112] S4: Molecular sieve selection and spraying, NaA type molecular sieve (Si / Al=1.0, unmodified) is selected, sodium silicate (Na2SiO3·9H2O) and sodium aluminate (NaAlO2) are dissolved in deionized water according to the molar ratio of SiO2 / Al2O3, and stirred until clarified to obtain a NaA type molecular sieve precursor solution; this molecular sieve has a suitable pore size and adsorption performance, and the above-mentioned NaA type molecular sieve precursor solution is sprayed on the surface of the alkaline activated carbon layer using a high-pressure airless spraying device (nozzle diameter 0.5mm, pressure 0.3MPa). Relative to the mass of the alkaline activated carbon layer, the molecular sieve load of the first spraying is 15wt%, and the secondary spraying is supplemented to 20wt%, and the film thickness is controlled at 0.5mm to ensure uniform loading;

[0113] S5: In-situ crystallization treatment: the sprayed molecular sieve is crystallized in a tube furnace at 400 °C for 4 h, with a heating rate of 5 °C / min and N2 protection;

[0114] S6: Collapse condition test: Detect the collapse time of the molecular sieve at pH = 2.5. The collapse time is required to be less than 10 seconds to ensure timely response in a strong acid environment and allow the acid to penetrate into the indicator layer;

[0115] (3) Preparation of indicator layer:

[0116] S7: Formula preparation: 0.1% (mass fraction) bromocresol purple is mixed with 2% (mass fraction) agar. Bromocresol purple is used as an indicator and changes color under specific pH conditions. Agar acts as a gel fixator.

[0117] S8: coating, the mixed solution obtained in step S7 is heated to 80° C. to form a sol, and then coated on a PET substrate with a film thickness of 30 μm to ensure that the indicator layer can effectively play an indicating role;

[0118] (4) The alkaline activated carbon layer, the molecular sieve layer and the indicator layer are stacked in sequence to obtain a composite adsorption material.

[0119] An adsorption system, comprising a shell and the composite adsorption material of Example 1, wherein the shell is made of polypropylene (PP) and the composite adsorption material is entirely coated on the shell;

[0120] The shell consists of two parts: an upper cover 1 located above the alkaline activated carbon layer and a base 2 for placing the composite adsorption material; the upper cover 1 is provided with circular holes using laser drilling technology, with a hole diameter of 0.8 mm and a hole spacing of 0.8 mm, allowing acidic substances to enter the alkaline activated carbon layer side of the composite adsorption material in the adsorption system, thereby completing the adsorption of acidic substances and subsequent display; the base 2 is an acid-resistant transparent shell with a groove structure, which is convenient for placing the composite adsorption material and observing changes in the indicator layer.

[0121] The alkaline activated carbon layer 3, the molecular sieve layer 4 and the indicator layer 5 are hot-pressed and composited at 180°C and 3 MPa to form an adsorption module. The adsorption module is then placed in a housing. The housing and the adsorption module are sealed by ultrasonic welding to prevent leakage of acid mist and ensure the overall performance of the adsorption module, thereby obtaining an adsorption system.

[0122] The structural diagram of the adsorption system of Example 1 is as follows Figure 1 shown.

[0123] Example 2

[0124] A composite adsorption material, comprising a coconut shell activated carbon layer loaded with MgO, a composite molecular sieve layer and an indicator layer stacked in sequence from top to bottom;

[0125] The thickness of the coconut shell activated carbon layer loaded with MgO was 5 mm, and the loading amount of MgO was 10 wt%;

[0126] The composite molecular sieve layer consists of an upper layer of MCM-41 (wall thickness 1.5 nm, collapsed at pH = 1.0), a middle layer of Ca-X molecular sieve (collapsed at pH = 1.5), and a lower layer of NaA molecular sieve (collapsed at pH = 2.0). The thickness of each layer is controlled at 50 μm.

[0127] The indicator layer consists of a substrate and an indicator located on the substrate. The substrate is a PP / PET composite non-woven fabric with a gram weight of 80g / m 2 The indicator is 0.1% (mass fraction) bromocresol green and 0.3% (mass fraction) methyl red, with a volume ratio of 2:1; the thickness of the indicator layer is 20 μm.

[0128] Example 2 A method for preparing a composite adsorption material comprises the following steps:

[0129] (1) Preparation of alkaline activated carbon layer:

[0130] S1: Raw material preparation: coconut shell activated carbon with a particle size of 200 mesh and an ash content of 2.5% is selected as the basic raw material. Coconut shell activated carbon has a rich pore structure and a large specific surface area, which is conducive to the adsorption of pollutants;

[0131] S2: Activation treatment, using KOH activation method, KOH and coconut shell activated carbon are mixed in a mass ratio of 3:1, and heated at 700 ° C for 1.5 hours to make the specific surface area of ​​coconut shell activated carbon reach 1250m 2 / g, thereby improving the adsorption performance;

[0132] S3: Alkaline loading: Nano-MgO was loaded onto the surface of activated coconut shell activated carbon using atomic layer deposition (ALD) technology. The number of cycles was set to 200, resulting in a 2nm thick MgO layer with a coverage of 98%. ALD technology can precisely control the thickness and coverage of the loading layer, ensuring that the activated carbon surface is evenly loaded with MgO, enhancing its adsorption capacity for specific pollutants. Finally, the treated activated carbon was laid into a 5mm thick alkaline activated carbon layer.

[0133] (2) Preparation of molecular sieve layer:

[0134] S4: Molecular sieve preparation: MCM-41 (wall thickness 1.5 nm, pH = 1.0 collapse), Ca-X molecular sieve (pH = 1.5 collapse), and NaA molecular sieve (pH = 2.0 collapse) are prepared as raw materials for the upper, middle, and lower layers. Different types of molecular sieves have different pore sizes and adsorption properties, and can adsorb pollutants of different sizes and properties;

[0135] S5: MCM-41, Ca-X type, and NaA type molecular sieves were respectively dispersed in an ethanol-water mixed solvent (volume ratio of 1:1), ultrasonically treated for 30 minutes to form a stable dispersion, and the three molecular sieve dispersions were sprayed in sequence by a layer-by-layer spraying method. The spraying order was: first spray MCM-41 (upper layer, 0.05 mm) → Ca-X type (middle layer, 0.05 mm) → NaA type (lower layer, 0.05 mm); total thickness: 0.15 mm; spraying layer by layer, using polyethylene glycol (PEG) as a sacrificial layer between layers to ensure the relative independence and stability between layers, and the loading amount was set to 20 wt% to ensure that the molecular sieve layer had good adsorption performance, thereby obtaining a molecular sieve layer; after layer-by-layer spraying, since the composite molecular sieve layer (MCM-41 / Ca-X / NaA) was separated by a PEG sacrificial layer, and each layer of molecular sieve already had acid response characteristics, no additional in situ crystallization treatment was required.

[0136] (3) Preparation of indicator layer:

[0137] S6: formula preparation, mixing bromocresol green (mass fraction 0.1%) and methyl red (mass fraction 0.03%) in a volume ratio of 2:1, and preparing an indicator solution by mixing with 95% ethanol. This indicator can produce color changes according to changes in the environment during the adsorption process, thereby indicating the adsorption state;

[0138] S7: Coating, using PP / PET composite non-woven fabric as the carrier, with a gram weight of 80g / m 2 The non-woven fabric has good air permeability and flexibility and is suitable as a carrier of the indicator layer. The indicator solution obtained in step S6 is coated on the non-woven fabric using a spin coating method. The rotation speed is set to 3000 rpm and the time is 30 s. The film thickness reaches 20 μm. The spin coating method can ensure that the indicator layer is evenly coated on the non-woven fabric, thereby improving the accuracy of the indication effect, thereby obtaining an indicator layer.

[0139] (4) The alkaline activated carbon layer, the molecular sieve layer and the indicator layer are stacked in sequence to obtain a composite adsorption material.

[0140] An adsorption system differs from Example 1 only in that the composite adsorption material of Example 2 is used, and the rest is the same as Example 1.

[0141] Example 3

[0142] A composite adsorption material, comprising a ZnO-Al2O3 loaded pine forest activated carbon layer, a molecular sieve layer and an indicator layer stacked in sequence from top to bottom;

[0143] The thickness of the ZnO-Al2O3 loaded pine forest activated carbon layer is 4 mm, and the loading amount of ZnO-Al2O3 is 18 wt%;

[0144] The molecular sieve in the molecular sieve layer is MCM-41 treated with silane coupling agent KH550, with a thickness of 0.3 mm;

[0145] The indicator layer consists of a substrate and an indicator located on the substrate. The substrate is a PP / PET composite non-woven fabric with a gram weight of 80g / m 2 The indicator is bromocresol purple (mass fraction 0.05%) and methyl red (mass fraction 0.03%), with a volume ratio of 1:1; the thickness of the indicator layer is 0.02 mm.

[0146] Example 3 The preparation method of the composite adsorption material comprises the following steps:

[0147] (1) Preparation of alkaline activated carbon layer:

[0148] S1: Raw material preparation, using pine forest activated carbon, with fiber length controlled at 50-100μm;

[0149] S2: Activation treatment, using 40% H3PO4 to activate, H3PO4 and pine forest activated carbon were mixed with a liquid-solid ratio of 3:1, and then carbonized at 450 ° C for 3 hours to make the specific surface area of ​​pine forest activated carbon reach 850m 2 / g;

[0150] S3: Alkaline loading, using the sol-gel method to load ZnO-Al2O3, the specific loading process is to dissolve zinc nitrate and aluminum nitrate in ethanol at a Zn:Al=1:1 (molar ratio) to form a precursor solution; immerse the pine forest activated carbon in the precursor solution and stir at 60°C until gelation; after drying, calcinate at 400°C for 2h to form a ZnO-Al2O3 composite; the specific surface area of ​​the loaded pine forest activated carbon reaches 800m 2 / g, then oxygen plasma cleaning was performed for 5 min at a power of 100 W and an O2 flow rate of 20 sccm, and finally the treated pine forest activated carbon was laid into an alkaline activated carbon layer with a thickness of 4 mm;

[0151] (2) Molecular sieve layer production:

[0152] S4: Solution preparation and molecular sieve pretreatment: Silane coupling agent KH550 and anhydrous ethanol are mixed in a volume ratio of 1:99 and stirred thoroughly until uniform to obtain a 1% by volume KH550 ethanol solution; thick-walled MCM-41 molecular sieves are dried at 110°C for 2 hours to remove surface adsorbed water and enhance the reaction activity of the coupling agent;

[0153] S5: Surface modification reaction: The pretreated MCM-41 molecular sieve was added to the KH550 ethanol solution with a solid-liquid ratio of 1:10. The surface modification reaction was then carried out in a constant temperature water bath at 60°C (error ±1°C) for 30 min. During this process, mechanical stirring at a speed of 250 rpm was performed to ensure that the molecular sieve was evenly dispersed and in full contact with the solution.

[0154] S6: Post-treatment: After the reaction, the solid product was collected by centrifugation at 5000 rpm for 5 min, washed three times with anhydrous ethanol to remove unreacted KH550 and by-products, and then dried under vacuum at 60°C for 12 h to obtain KH550-modified MCM-41;

[0155] S7: KH550-modified MCM-41 was added to an ethanol solution containing 0.5% hydroxyethyl cellulose and ultrasonically dispersed to form a uniform spray solution. The spray solution was sprayed onto the activated carbon layer at a loading of 15 wt% using a high-pressure airless sprayer (nozzle diameter 0.5 mm, pressure 0.3 MPa). The sprayed sample was then placed in a tube furnace at 400°C with a heating rate of 5°C / min under N2 protection to obtain a molecular sieve layer with a thickness of 0.3 mm.

[0156] (3) Preparation of indicator layer:

[0157] S8: Prepare a double indicator by using 95% ethanol as a solvent to prepare bromocresol purple (mass fraction 0.05%) and methyl red (mass fraction 0.03%), and mix them in a volume ratio of 1:1;

[0158] S9: Base material selection, choose PP / PET composite non-woven fabric as the base material, with a gram weight of about 80g / m 2 The dual indicator was then coated on the substrate using a slit coater (accuracy ±1 μm). The drying conditions were controlled by gradient, first drying at 40°C for 2 h and then drying at 80°C for 1 h to obtain an indicator layer with a thickness of 20 μm.

[0159] (4) The alkaline activated carbon layer, the molecular sieve layer and the indicator layer are stacked in sequence to obtain a composite adsorption material.

[0160] An adsorption system, which differs from Example 1 only in that the composite adsorption material of Example 3 is used, and the rest is the same as Example 1.

[0161] Comparative Example 1

[0162] Compared with Example 1, Comparative Example 1 does not contain a molecular sieve layer, and other aspects are the same as Example 1.

[0163] Performance Testing

[0164] 1. Pore structure test

[0165] The pore structures of the composite adsorption materials of Example 1 and Comparative Example 1 were tested, and the test items and test methods were as follows:

[0166] Specific surface area: calculated using the BET method in accordance with GB / T 19587-2017;

[0167] Micropore ratio: HK method is used for test calculation;

[0168] Pore ​​size distribution: Non-local density functional theory (NLDFT) was used for test calculation.

[0169] Example 1 and Comparative Example 1 The pore structures of the composite adsorption materials are shown in Table 1.

[0170] Table 1: Pore structure of composite adsorption materials of Example 1 and Comparative Example 1

[0171] parameter Example 1 Comparative Example 1 <![CDATA[Specific surface area (m 2 / g)]]> 980±50 1200±80 Micropore ratio 45％ 65％ Pore ​​size distribution range (nm) 0.5-50 0.3-30

[0172] As can be seen from Table 1, the specific surface area of ​​the composite adsorbent material of Example 1 is lower than that of Comparative Example 1. The molecular sieve layer introduces mesopores (2-50nm), which partially blocks the activated carbon micropores (comparative data: the proportion of micropores in Comparative Example 1 is 65%, and that in Example 1 is 45%). The proportion of micropores in the composite adsorbent material of Example 1 is lower than that in Comparative Example 1. This is because the lack of the molecular sieve layer leads to a reduction in mesopores, and the micropores provide high specific surface area adsorption sites. The pore size distribution range in the composite adsorbent material of Example 1 is different from that of Comparative Example 1. The mesopores of the molecular sieve in the molecular sieve layer of Example 1 can delay the diffusion of acid solution and improve structural stability.

[0173] 2. Adsorption performance test

[0174] The adsorption performance of the composite adsorption materials of Example 1 and Comparative Example 1 was tested, and the specific test items and test methods are as follows:

[0175] Adsorption capacity: Tested according to GB / T 12496-2022, 98% H2SO4 mist, 25°C;

[0176] Adsorption rate: 0-60min was measured using the pseudo-second-order model;

[0177] Humidity sensitivity: adsorption capacity loss at 80% relative humidity (80% RH) (compared to dry conditions).

[0178] The adsorption performance test results of the composite adsorption materials of Example 1 and Comparative Example 1 are shown in Table 2.

[0179] Table 2: Adsorption properties of composite adsorption materials of Example 1 and Comparative Example 1

[0180]

[0181] As shown in Table 2, the adsorption capacity, adsorption rate, and humidity sensitivity of Example 1 are superior to those of Comparative Example 1. Due to the lack of a molecular sieve layer, the micropore selective adsorption of the molecular sieve is lost, resulting in a lower adsorption capacity for Comparative Example 1 than for Example 1. At the same time, alkaline activated carbon has a fast macropore diffusion rate and is easily saturated. In the absence of the micropore selective adsorption of the molecular sieve layer, the adsorption rate is higher. Furthermore, the molecular sieve layer acts as a physical barrier to block water molecules, which can reduce the deactivation of the activated carbon hydroxyl groups and indirectly increase the apparent adsorption rate (increase the K2 value).

[0182] 3. Chemical stability test

[0183] The chemical stability of the composite adsorption materials of Example 1 and Comparative Example 1 was tested, and the test was divided into two tests. The first test was to place the adsorption systems of Example 1 and Comparative Example 1 in an environment with pH = 0.5 for 240 h, and test the disintegration rate (pore collapse of the alkaline activated carbon layer and the molecular sieve layer as a whole). The test method was the mass loss method (refer to GB / T 12496-2022); the second test was to place the adsorption systems of Example 1 and Comparative Example 1 in 98% sulfuric acid for 7 days, and test the disintegration rate. The results are shown in Table 3.

[0184] Table 3: Chemical stability of composite adsorption materials in Example 1 and Comparative Example 1

[0185] Test conditions Example 1 Disintegration rate Comparative Example 1 Disintegration rate Place in an environment with pH = 0.5 <5％ 12-18％ 98% sulfuric acid soak Structural integrity Pore ​​collapse 20%

[0186] As can be seen from Table 3, the composite adsorbent material of Example 1 of the present invention has good chemical stability. This is because the molecular sieve framework has stronger acid corrosion resistance. When the molecular sieve layer is missing, the overall acid corrosion resistance of the composite adsorbent material is reduced, and the functional groups on the activated carbon surface dissociate in the presence of acid, making the pores easily collapse.

[0187] 4. Mechanical strength test

[0188] The mechanical strength of the composite adsorption materials of Example 1 and Comparative Example 1 was tested, and the test items and test methods were as follows:

[0189] Compressive strength: Tested in accordance with GB / T 30202-2013 "Activated carbon for desulfurization and denitrification";

[0190] Flexibility: Refer to GB / T 1040-2018 "Determination of tensile properties of plastics".

[0191] The mechanical strengths of the composite adsorption materials of Example 1 and Comparative Example 1 are shown in Table 4.

[0192] Table 4: Mechanical strength of composite adsorption materials of Example 1 and Comparative Example 1

[0193] Test items Example 1 Comparative Example 1 Compressive strength (MPa) 28.5±1.2 15.3±2.1 Flexibility (bending angle) 45° no break Cracks appear at 25°

[0194] As can be seen from Table 4, the mechanical strength of the composite adsorbent material of Example 1 of the present invention is superior to that of Comparative Example 1. Comparative Example 1 lacks a molecular sieve layer, which lacks the rigid support function of the molecular sieve layer, resulting in poor flexibility and the inability to exert the molecular sieve-carbon fiber composite reinforcement effect, resulting in reduced compressive strength.

[0195] In addition, due to the complex preparation process of molecular sieves, although the absence of a molecular sieve layer can reduce costs by about 30%, due to the poor regeneration performance of the activated carbon, the service life of the composite adsorption material of Comparative Example 1 is 8-12 months, while the service life of the composite adsorption material of Example 1 is 18-24 months, and the service life of Comparative Example 1 is shortened by about 50%.

[0196] In summary, the present invention, through the combined action of the alkaline activated carbon layer and the molecular sieve layer, exhibits excellent adsorption of acidic substances, along with good chemical stability and mechanical strength. When the adsorbed acid reaches a certain concentration, the molecular sieve structure collapses, allowing the acid to penetrate into the indicator layer, which visually displays the adsorption status. A corresponding color change in the indicator layer indicates that the adsorption material has failed and requires prompt replacement.

[0197] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite adsorption material, characterized in that: It comprises an alkaline activated carbon layer, a molecular sieve layer and an indicator layer which are stacked in sequence; The alkaline activated carbon layer includes activated carbon and alkaline substances supported on the activated carbon.

2. The composite adsorption material according to claim 1, characterized in that The activated carbon includes at least one of coal-based activated carbon, coconut shell activated carbon and wood-based activated carbon; and / or the alkaline substance includes at least one of Ca(OH)2, KOH, MgO and ZnO-Al2O3 complex.

3. The composite adsorption material according to claim 2, characterized in that: The activated carbon is activated carbon that has been activated.

4. The composite adsorption material according to claim 3, characterized in that In the alkaline activated carbon layer, the loading amount of the alkaline substance is 10-25 wt %; and / or the porosity of the activated carbon after activation treatment is ≥85%.

5. The composite adsorption material according to claim 1, characterized in that The molecular sieve in the molecular sieve layer includes an acid-responsive molecular sieve; and / or the indicator layer includes a substrate and an indicator located on the substrate.

6. The composite adsorption material according to any one of claims 1 to 5, characterized in that: The thickness of the alkaline activated carbon layer is 3-5 mm; and / or the thickness of the molecular sieve layer is 60 μm-1 mm; and / or the thickness of the indicator layer is 20-40 μm.

7. The method for preparing the composite adsorption material according to any one of claims 1 to 6, characterized in that: The following steps are involved: The alkaline activated carbon layer, the molecular sieve layer and the indicator layer are stacked in sequence to obtain the composite adsorption material.

8. The preparation method according to claim 7, characterized in that The preparation process of the alkaline activated carbon layer is as follows: the activated carbon is activated and then loaded with alkaline substances, and then laid to obtain the alkaline activated carbon layer; And / or, the molecular sieve layer is prepared by spraying the molecular sieve on the alkaline activated carbon layer to obtain the molecular sieve layer; And / or, the indicator layer is prepared by coating the indicator on the substrate to obtain the indicator layer.

9. The preparation method according to claim 8, characterized in that The activation treatment process is to mix the activating agent and the activated carbon and then perform heat treatment.

10. An adsorption system, characterized in that: The composite adsorption material comprises the composite adsorption material according to any one of claims 1 to 6.

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