Attapulgite double-effect catalyst as well as preparation method and application thereof in degradation of VOCs (Volatile Organic Compounds)

Abstract

The invention belongs to the technical field of adsorption photocatalysis, and particularly relates to an attapulgite double-effect catalyst and a preparation method and application thereof in degradation of VOCs (volatile organic compounds), the preparation method comprises the following steps: S1, respectively fully dissolving attapulgite original soil and a dispersing agent in water, standing, and centrifugally separating to obtain a suspension; and S2, adding an ion exchange solution into the suspension, mixing and reacting, and sequentially stirring, centrifuging, drying, grinding and sieving to obtain the attapulgite double-effect catalyst. The attapulgite double-effect catalyst is formed by carrying out acid or alkali ion exchange treatment on the original attapulgite, the preparation cost is low, and the attapulgite double-effect catalyst has a large specific surface area, a rich pore structure and excellent adsorption performance, and realizes double-effect degradation of VOCs (Volatile Organic Compounds).

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption photocatalysis, and particularly relates to a palygorskite dual-effect catalyst, a preparation method thereof, and an application thereof in the degradation of VOCs. Background Art

[0002] The continuous release and accumulation of harmful pollutants in the atmosphere will not only damage the living environment but also endanger human health. VOCs organic waste gases originate from the combustion of fuels such as coal and petroleum, as well as the production processes of chemical products such as painting, coatings, and plastics. If these waste gases are discharged into the air without treatment, they will cause great harm to the environment. Volatile substances will combine with nitrogen dioxide in the air to form ozone, and the resulting photochemical smog and irritating odors will irritate the eyes and respiratory tract, and damage important human organs such as cardiopulmonary function and the liver. If people are exposed to volatile organic waste gases for a long time, it may even lead to the risk of cancer, posing a huge threat to human health. Therefore, eliminating and reducing VOCs in the atmospheric environment is a major problem to be solved at present.

[0003] Traditional methods for treating organic pollutants include catalytic combustion, biodegradation, electrochemical degradation, and room-temperature catalytic oxidation technology, etc.; most of these traditional methods use metal-based catalysts, but there are problems such as high preparation cost, low efficiency, and large environmental impact when using these metal-based catalysts; moreover, in the treatment process, the catalyst often tends to be poisoned or deactivated, resulting in poor degradation effect on VOCs.

[0004] Therefore, developing a VOCs degradation catalyst with low cost and high degradation performance is a hot issue in current research. Summary of the Invention

[0005] Aiming at the technical problems that the existing treatment of organic pollutants often has high cost and poor VOCs degradation effect, the present invention provides a palygorskite dual-effect catalyst, a preparation method thereof, and an application thereof in the degradation of VOCs.

[0006] The present invention forms a palygorskite dual-effect catalyst by simply treating the original palygorskite soil with acid or alkali. The preparation cost is low, and the palygorskite dual-effect catalyst has a large specific surface area, a rich pore structure, and excellent adsorption performance, realizing the dual-effect degradation of VOCs.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A preparation method of a palygorskite dual-effect catalyst, comprising the following steps:

[0009] S1. Respectively take the original palygorskite soil and a dispersant, fully dissolve them in water, stand still, and centrifuge to obtain a suspension;

[0010] S2. Add an ion exchange solution to the suspension in step S1. After mixing and reacting, stir, centrifuge, dry, grind, and sieve in sequence to obtain an attapulgite dual-effect catalyst; the mass-volume ratio of the attapulgite raw soil, dispersant, ion exchange solution, and water is (1-3) g:(0.1-0.5) g:(1-5) ml:(5-20) ml; the concentration of the ion exchange solution is 0.01 mol / L - 3 mol / L.

[0011] Further limit that the dispersant is sodium polymetaphosphate, sodium pyrophosphate, sodium metasilicate, or sodium disilicate.

[0012] Further limit that in step S1, before dissolution, the attapulgite raw soil needs to be soaked for 11-13 h for purification.

[0013] Further limit that in step S1, it is fully dissolved for 1-2 h, and the standing time is 12-24 h.

[0014] Further limit that in step S2, the ion exchange solution is an acidic solution or an alkaline solution; the concentration of the acidic solution is 0.1 mol / L - 3 mol / L; the concentration of the alkaline solution is 0.01 mol / L - 0.2 mol / L.

[0015] Further limit that in step S2, stir for 12-24 h and sieve through a 100-mesh sieve.

[0016] The attapulgite dual-effect catalyst prepared by the preparation method of the attapulgite dual-effect catalyst described above.

[0017] Application of the attapulgite dual-effect catalyst in degrading VOCs gas.

[0018] The attapulgite dual-effect catalyst is applied in degrading toluene through adsorption-photocatalysis coupling.

[0019] Further limit that during the application, in a closed system, the toluene concentration is 2000 ppm, the dosage of the attapulgite dual-effect photocatalyst is 20 mg - 120 mg, without light-dark reaction at 65 °C for 60 min, and then photocatalytic reaction for 120 min.

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

[0021] 1. In the present invention, the attapulgite raw soil is simply treated with acid and alkali to form an attapulgite dual-effect catalyst. Under simulated sunlight irradiation, the attapulgite is photoexcited to generate photoinduced e - -h +Yes, further redox reactions occur to produce active substances. Correspondingly, the attapulgite dual-effect catalyst performs dual-effect degradation on VOCs by first adsorbing and then photocatalyzing; that is, VOCs are concentrated by the adsorption technology first, and then the concentrated VOCs are decomposed and removed in the photocatalytic oxidation device, especially the degradation and removal of toluene.

[0022] 2. The present invention uses the original attapulgite soil to prepare the catalyst. Preferably, the original attapulgite soil is red soil, and the specific surface area of the red soil is 78.99 m 2 / g; the specific surface area after acid treatment is 125.227 m 2 / g; the specific surface area after alkali treatment is 93.33 m 2 / g. The finally formed attapulgite dual-effect catalyst has a large specific surface area, a rich pore structure and excellent adsorption performance, enabling VOCs to be adsorbed, degraded and converted into harmless substances.

[0023] 3. The present invention optimizes the conditions for the attapulgite dual-effect catalyst to degrade toluene. In a closed system, the toluene concentration is 2000 ppm, the dosage of the attapulgite dual-effect photocatalyst is 20 mg - 120 mg, and without light and dark reaction for 60 min at 65°C, and then under light irradiation for 120 min, the toluene has a relatively high degradation rate; and the degradation rate of the acid-modified attapulgite dual-effect catalyst for toluene is as high as 92%, and the adsorption and photocatalytic performance are better.

[0024] 4. For the attapulgite dual-effect catalyst obtained by the present invention, the removal rate of toluene is still above 80% after five cycles, and the attapulgite dual-effect catalyst shows good cycle stability.

[0025] 5. When preparing the catalyst in the present invention, the raw materials used are the original attapulgite soil (red soil), dispersants (sodium metaphosphate, sodium pyrophosphate, sodium metasilicate or sodium disilicate), and ion exchange solutions (acidic solution and alkaline solution). The types of raw materials are few and easy to obtain; the preparation method has the characteristics of simple operation, simple process and environmental friendliness, and is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Scanning electron microscope (SEM) photos of attapulgite red soil (ATP), acid-modified (HCl-ATP), and alkali-modified (NaOH-ATP);

[0027] Figure 2 Schematic diagrams of X-ray diffraction (XRD) of attapulgite red soil (ATP), acid-modified (HCl-ATP), and alkali-modified (NaOH-ATP);

[0028] Figure 3Schematic diagram of Fourier transform infrared spectroscopy (FT-IR) of attapulgite red soil (ATP), acid-modified (HCl-ATP), and alkali-modified (NaOH-ATP);

[0029] Figure 4 Transient photocurrent (IT) and electrochemical impedance (EIS) tests of attapulgite red soil (ATP) and acid-modified (HCl-ATP) and alkali-modified (NaOH-ATP) attapulgite;

[0030] Figure 5 Comparison chart of toluene degradation rates of attapulgite red soil (ATP), acid-modified (HCl-ATP), alkali-modified (NaOH-ATP) and different test conditions;

[0031] Figure 6 Comparison chart of toluene degradation rates of raw attapulgite and dual-functional attapulgite catalysts with different treatment methods;

[0032] Figure 7 Result chart of the stability of the dual-functional catalyst after acid modification of attapulgite; Detailed implementation mode

[0033] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] The present invention provides a preparation method of a dual-functional attapulgite catalyst, which includes the following steps:

[0035] S1. Respectively take raw attapulgite and a dispersant and fully dissolve them in water, let it stand, and centrifugally separate to obtain a suspension.

[0036] In the present invention, the dispersant is sodium polymetaphosphate, sodium pyrophosphate, sodium metasilicate or sodium disilicate.

[0037] In the present invention, the raw attapulgite is red soil.

[0038] In step S1 of the present invention, it is fully dissolved for 1 h to 2 h, and the standing time is 12 h - 24 h. Before dissolution, the raw attapulgite also needs to be soaked for 11 h - 13 h for purification.

[0039] S2. Add hydrochloric acid to the suspension in step S1, and after stirring, centrifuging, drying, grinding and sieving, obtain a dual-functional attapulgite catalyst.

[0040] S3. Add an ion exchange solution to the suspension in step S1, after mixing and reacting, successively stir, centrifuge, dry, grind and sieve to obtain a dual-functional attapulgite catalyst.

[0041] In the present invention, the mass-volume ratio of attapulgite raw soil, dispersant, ion exchange solution and water is (1-3) g : (0.1-0.5) g : (0.1-1) g, (1-5) ml : (5-20) ml.

[0042] Preferably, the ion exchange solution is an acidic solution or a basic solution; the concentration of the acidic solution is 0.1 mol / L - 3 mol / L; the concentration of the basic solution is 0.01 mol / L - 0.2 mol / L.

[0043] More preferably, the acidic solution is hydrochloric acid with a concentration of 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L; the basic solution is sodium hydroxide solution with a concentration of 0.01 mol / L, 0.05 mol / L, 0.15 mol / L or 0.2 mol / L.

[0044] In step S2 of the present invention, stir for 12 h - 24 h and pass through a 100 - 200 mesh sieve.

[0045] In step S2 of the present invention, when the ion exchange solution is an acidic solution, treating with the acidic solution has the following advantages: more acidic sites (such as Lewis acid sites or Bronsted acid sites) are generated on the surface of attapulgite, promoting the exchange of cations (such as sodium ions, calcium ions) originally present in attapulgite with hydrogen ions, further increasing the number and strength of acidic sites; the metal oxides contained in attapulgite can form a more active state under acidic conditions, thereby improving the catalytic ability of the catalyst; treating with strong acid causes partial destruction of the structure of attapulgite, especially the weak bonds between layers will break, increasing the interlayer spacing, which helps to improve its adsorption performance; through acid treatment, in the catalytic degradation of the catalyst, toluene is more easily oxidized in an acidic environment, and is also easily ionized or forms compounds that are easily captured by the photocatalyst, thereby improving the treatment efficiency of toluene.

[0046] In step S2 of the present invention, when the ion exchange solution is a basic solution, treating with the basic solution has the following advantages: when treating with the basic solution, alkali metal ions (such as Na + , K + ) enter the interlayer region, increasing the interlayer electrostatic repulsion, causing the interlayer to expand, increasing the interlayer distance of attapulgite, which helps to further improve its adsorption performance; treating with the basic solution causes the cations inside attapulgite to exchange, and more alkali metal ions or alkaline earth metal ions are introduced as cocatalysts, thereby increasing the polarity on the surface of the adsorbent or changing its charge distribution, thereby improving the degradation ability of VOCs.

[0047] The present invention uses attapulgite as a raw material to form a dual-effect catalyst through simple ion-exchange solution treatment. The catalyst has a large specific surface area, a rich pore structure, and excellent adsorption performance, and can well adsorb VOCs first and then photocatalytically degrade and convert them into harmless substances. The treatment process is simple and has good cycle stability, and has a good degradation effect on VOCs, realizing environmental friendliness.

[0048] Application of the attapulgite dual-effect catalyst of the present invention in the degradation of VOCs; preferably, the attapulgite dual-effect catalyst is applied in the degradation of toluene through adsorption-photocatalysis coupling. In a specific application, in a closed degradation system, the toluene concentration is 1500-2000 ppm, and the dosage of the attapulgite raw soil dual-effect photocatalyst is 0.1 g.

[0049] The following uses several specific examples to explain in detail the treatment and performance of the catalyst of the present invention.

[0050] It should be noted that the operations adopted in the following examples are all conventional operations in the art without special instructions. The pharmaceutical reagents and the like adopted in the following examples are all purchased from the market.

[0051] Example 1

[0052] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0053] S1. Put 1 g of attapulgite raw soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture. Let the mixture stand at room temperature for 24 hours to allow the attapulgite raw soil to fully absorb the active substances in the solution.

[0054] S2. Centrifuge the mixture, separate the suspension and the solid, take out the suspension and add 10 ml of 0.5 mol / L hydrochloric acid, stir again for 24 h, and then perform centrifugal drying treatment. The dried solid is ground and filtered through a 100-mesh sieve to obtain an acid-modified attapulgite dual-effect catalyst, labeled as sample 1.

[0055] Example 2

[0056] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0057] S1. Put 1 g of attapulgite raw soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0058] S1. The same as in Example 1 (the difference is that 10 ml of 2.0 mol / L hydrochloric acid is added) to obtain an acid-modified attapulgite dual-effect catalyst, labeled as sample 2.

[0059] Example 3

[0060] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0061] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0062] S2. The same as Example 1 (the difference is adding 10 ml of 1.0 mol / L hydrochloric acid) to obtain the acid-modified attapulgite dual-effect catalyst, labeled as Sample 3.

[0063] Example 4

[0064] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0065] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0066] S2. The same as Example 1 (the difference is adding 10 ml of 1.5 mol / L hydrochloric acid) to obtain the acid-modified attapulgite dual-effect catalyst, labeled as Sample 4.

[0067] Example 5

[0068] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0069] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0070] S2. The same as Example 1 (the difference is adding 10 ml of 2.5 mol / L hydrochloric acid) to obtain the acid-modified attapulgite dual-effect catalyst, labeled as Sample 5.

[0071] Example 6

[0072] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0073] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium polymetaphosphate, and add 20 ml of deionized water to fully dissolve the mixture. Let the mixture stand at room temperature for 24 hours to allow the raw attapulgite soil to fully absorb the active substances in the solution.

[0074] S2. Place the mixture in a centrifuge for centrifugation to separate the suspension from the solid. Take out the suspension and add 10 ml of 0.05 mol / L sodium hydroxide solution, stir for another 24 h, and then perform centrifugal drying. Grind the dried solid and filter it through a 100-mesh sieve to obtain the attapulgite acid-modified dual-effect catalyst, labeled as Sample 6.

[0075] Example 7

[0076] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0077] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium metaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0078] S1. The same as in Example 1 (the difference is adding 10 ml of 0.1 mol / L sodium hydroxide solution) to obtain the attapulgite acid-modified dual-effect catalyst, labeled as Sample 7.

[0079] Example 8

[0080] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0081] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium metaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0082] S2. The same as in Example 1 (the difference is adding 10 ml of 0.15 mol / L sodium hydroxide solution) to obtain the attapulgite acid-modified dual-effect catalyst, labeled as Sample 8.

[0083] Example 9

[0084] The preparation method of the attapulgite dual-effect catalyst provided in this example includes the following steps:

[0085] S1. Put 1 g of raw attapulgite soil (specifically red soil) into a container, add 0.2 g of sodium metaphosphate, and add 20 ml of deionized water to fully dissolve the mixture.

[0086] S2. The same as in Example 1 (the difference is adding 10 ml of 0.2 mol / L sodium hydroxide solution) to obtain the attapulgite acid-modified dual-effect catalyst, labeled as Sample 9.

[0087] The sodium metaphosphate in the above examples can also be replaced with sodium pyrophosphate, sodium metasilicate or sodium disilicate.

[0088] The attapulgite double-effect catalyst prepared in the above embodiments can be applied to the environmental treatment of adsorbing-photocatalytic degradation of organic pollutants.

[0089] Experiment 1

[0090] In this experiment, scanning electron microscopy (SEM) testing technology was used to explore the microscopic morphology of the original attapulgite soil; the SEM model was JSM-6701F.

[0091] The original attapulgite soil (red soil, denoted as ATP), the acid-modified attapulgite red soil (i.e., Sample 2, HCl-ATP), and the alkali-modified attapulgite red soil (i.e., Sample 7, NaOH-ATP) were selected as samples, and SEM analysis was performed on the samples respectively to obtain electron microscope photos. The results are as Figure 1 shown. (a, b) are red soil, and the corresponding scale lengths are 1 μm and 200 nm respectively; (c, d) are the attapulgite soil treated with sodium hydroxide, and the corresponding scale lengths are 1 μm and 5 μm respectively; (e, f) are the attapulgite soil treated with hydrochloric acid, and the corresponding scale lengths are 2 μm and 5 μm respectively.

[0092] See Figure 1 . From (a, b), it can be seen that the attapulgite red soil is rod-shaped, but there are massive structures in the red soil. After observation, it is judged that this part may be dolomite; from (c, d), it can be seen that the attapulgite red soil treated with sodium hydroxide has a more uniform rod-shaped structure and also contains a small amount of quartz impurities, etc.; from (e, f), it can be seen that the attapulgite red soil treated with hydrochloric acid has a finer rod-shaped structure and fewer quartz impurities.

[0093] Experiment 2

[0094] Samples: The original attapulgite soil (red soil, denoted as ATP), the acid-modified attapulgite red soil (i.e., Sample 2, denoted as HCl-ATP), and the alkali-modified attapulgite red soil (i.e., Sample 7, NaOH-ATP) were selected.

[0095] The test method was X-ray Diffraction, abbreviated as XRD. It is an important means to characterize the crystal structure. An appropriate amount of powder was ground, compacted, and fixed. The instrument model was D / max2200PC, and the test conditions were: Cu-Kα ray, working voltage 40 KV, working current 40 mA, and scanning range 5-80°. As Figure 2 shown, are the XRD patterns of the original attapulgite soil, Sample 2, and Sample 7.

[0096] See Figure 2It can be seen that there are 6 weak diffraction peaks at 2θ = 19.8°, 27.8°, 35.6°, 35.8°, 42.8° and 61.6°, which is consistent with the previous report on attapulgite (ATP) (JCPDS No. 82-1873), and there is no obvious change in the peaks on the XRD diagram after acid modification and alkali modification.

[0097] Test 3

[0098] Samples: original attapulgite (red soil, denoted as ATP), acid-modified attapulgite red soil (ie, sample 2, HCl-ATP), and alkali-modified attapulgite red soil (ie, sample 7, NaOH-ATP) were selected.

[0099] The test method is to use Fourier-infrared spectrometer (FT-IR) to qualitatively analyze the functional groups of materials, observe infrared spectra, and analyze and identify substances. The instrument detection model is Nicolet-6700. The specific operation of the test is: dry the experimental sample and KBr, fully grind them at a mass ratio of 1:100, dry them, press them into thin sheets, and test them. Figure 3 shown.

[0100] See also Figure 3 It can be seen that the adsorption band is at 3612 cm -1 The center is the OH stretching mode in Al-Al-OH. -1 The strong band at 3410 cm -1 and 3428cm -1 The broad adsorption band at corresponds to the OH stretching vibration of physically adsorbed water on the material surface.

[0101] Test 4

[0102] Samples: original attapulgite (red soil, denoted as ATP), acid-modified attapulgite red soil (ie, sample 2, HCl-ATP), and alkali-modified attapulgite red soil (ie, sample 7, NaOH-ATP) were selected.

[0103] The test method is: use a platinum electrode as the counter electrode, a silver electrode as the reference electrode, an iron electrode as the working electrode, and a 0.1M Na 2 SO 4 The aqueous solution is used as the electrolyte solution to form a three-electrode system. The test process is as follows: First, ultrasonically clean the 10×10mm FTO glass with acetone, anhydrous ethanol and distilled water for 30 minutes, then rinse it repeatedly with distilled water, and then dry it. The above samples are dispersed into suspensions with anhydrous ethanol, a small amount of naphthol is added, and the ultrasonically dispersed solution is dripped on the conductive surface of the FTO glass, dried and set aside; perform photocurrent test and impedance test, such as Figure 4as shown; Figure 4 (a) shows the photocurrent test results, Figure 4 (b) shows the impedance test (the impedance test environment is with the light source on). The frequency range of the photocurrent test is 10k - 0.1Hz, and the bias voltage is 2.0V.

[0104] See Figure 4 , Figure 4 (a) indicates that the photocurrent response of HCl - ATP is higher than that of ATP and NaOH - ATP, and the current density can promote the separation of e - -h + , proving that it can carry out photocatalytic reaction degradation. Figure 4 (b) indicates that HCl - ATP shows a smaller arc radius, indicating that the process of charge transfer and separation is the fastest, which is consistent with the above conclusion about inhibiting electron - hole recombination.

[0105] Experiment 5

[0106] To explore the photocatalytic conditions of the dual - effect catalyst, the catalytic degradation of VOCs gas is carried out under simulated sunlight. Through a series of comparative experiments, the purpose is to explore the photocatalytic performance of the dual - effect catalyst under different conditions, so as to find the appropriate catalytic conditions.

[0107] The samples are: attapulgite raw soil (red soil, denoted as ATP), acid - modified attapulgite red soil (i.e., sample 2, HCl - ATP), and alkali - modified attapulgite red soil (i.e., sample 7, NaOH - ATP).

[0108] Toluene detection conditions: The instrument model is the Zhongjiao Jinyuan GC7920 full - automatic system gas chromatograph. The carrier gas is nitrogen (N 2 ), the fuel gas is hydrogen (H 2 ). When hydrogen is ignited, it is 0.2MPa, and after ignition, it is 0.15MPa. The detector of the chromatograph is at 150°C, the injector temperature is 180°C, and the temperature of the methane conversion furnace is 360°C.

[0109] Preparation of the photocatalytic reaction sample dish: Weigh 0.1g of the above - mentioned samples respectively into glass quartz dishes with a diameter of 2cm, and make the samples evenly disperse at the bottom of the petri dish, then dry them in an oven at 60°C. Place them in a customized 220mL airtight quartz reaction vessel, inject 3μL of analytical - grade liquid toluene into the vessel, and let it stand for 1h to completely volatilize the toluene in the vessel into gas and reach the adsorption - desorption equilibrium with the catalyst. Use a gas injection syringe to extract 600μL of gas and inject it into the gas chromatograph to detect the toluene concentration, which is used as the initial concentration of toluene. The initial concentration of toluene is approximately 2000ppm. Then turn on the 300W xenon lamp, measure the toluene concentration every 15 minutes, and use the methane conversion furnace to detect CO 2 .

[0110] The photocatalytic degradation tests were set up for the above three samples in the following groups.

[0111] Group 1: Without light irradiation in a closed system, reacting at 65 °C for 180 min, with the toluene injection amount being about 2000 ppm.

[0112] Group 2: Only with light irradiation in a closed system, reacting at 65 °C for 180 min, with the toluene injection amount being about 2000 ppm.

[0113] Group 3: Without light irradiation for a dark reaction for 60 min at 65 °C in a closed system, then with light irradiation for 120 min, with the toluene injection amount being about 2000 ppm.

[0114] Take toluene with an original concentration C 0 of about 2000 ppm, and conduct tests according to the types and addition amounts of the catalysts in the above groups. Degrade toluene for 180 min, and measure the concentration of toluene and CO 2 concentration in the closed system every 15 min, calculate the ratio of C / C 0 , and calculate the change curve of the degradation rate with time. The results are as Figure 5 shown.

[0115] See Figure 5 , where (a) is the toluene adsorption curves of ATP, HCl - ATP, and NaOH - ATP without light irradiation in a closed system. It can be seen that the change in toluene concentration is not significant; (b) is the toluene adsorption curves of ATP, HCl - ATP, and NaOH - ATP with only light irradiation in a closed system. It can be seen that under the assistance of simulated sunlight, the removal rate of toluene by HCl - ATP is 73%; the removal rate of toluene by HCl - ATP is 70%; (c) is the toluene adsorption curves of ATP, HCl - ATP, and NaOH - ATP in a closed system at 65 °C with a dark reaction for 60 min without light first and then a simulated light irradiation reaction for 120 min. It can be seen that the removal rate of toluene by HCl - ATP reaches 92%. This is mainly because after toluene is adsorbed through the dark reaction first; then under simulated sunlight irradiation, the substances in attapulgite will have a rapid recombination of photogenerated charges, causing the toluene adsorbed on the surface of attapulgite to be released, thus increasing the removal rate of toluene.

[0116] It can be seen from this that the dual - effect catalyst formed based on the original attapulgite (red soil) of the present invention has a higher degradation rate for toluene under the photocatalytic conditions of a dark reaction for 60 min without light first and then a light irradiation reaction for 120 min at 65 °C in a closed system.

[0117] Experiment 6

[0118] This experiment mainly studies the degradation effect of catalysts formed under different concentrations of acidic solutions, different alkaline solutions, different catalyst dosages, and different calcination temperatures on toluene.

[0119] 6.1. Study on the performance of catalysts with different concentrations of acidic solutions

[0120] Samples: Attapulgite double-effect catalysts (Samples 1 - 5) treated with different concentrations of acidic solutions prepared in Examples 1 - 5, and original attapulgite soil (red soil, denoted as ATP).

[0121] Take 100 mg of each of the above samples in a quartz glass dish, add 2000 ppm of toluene in a closed system, and carry out the adsorption-photocatalytic reaction with reference to the photocatalytic conditions of the third group in Test 7.

[0122] See Figure 6 , where (a) is the degradation curve of the catalyst under different concentrations of acidic solutions. It can be seen that when the hydrochloric acid concentration is 2.0 mol / L, the degradation removal rate of toluene reaches about 92%.

[0123] 6.2. Comparison of the degradation rate of toluene with different catalyst dosages

[0124] Samples: Attapulgite double-effect catalyst of Example 2 (i.e., Sample 2).

[0125] Testing method: Take 20 mg, 40 mg, 60 mg, 80 mg, 100 mg, and 120 mg of the sample respectively, place them in a quartz glass dish, and then add 2000 ppm of toluene in a closed system, and carry out the adsorption-photocatalytic reaction with reference to the photocatalytic conditions of the third group in Test 7.

[0126] See Figure 6 , where (b) is the degradation curve of toluene under different catalyst dosages. It is found that when the catalyst dosage is 100 mg, the degradation removal rate of toluene reaches more than 90%.

[0127] 6.3. Degradation rate of toluene by catalysts calcined at different temperatures

[0128] Samples: Original attapulgite soil (red soil, denoted as ATP).

[0129] Testing method: Take 1 g of the sample in a crucible, then place it in a muffle furnace for calcination. Heat it to 300 °C, 400 °C, and 500 °C at a heating rate of 5 °C / min respectively, keep it warm for 2 h at each temperature, and let it cool naturally in the furnace to obtain the calcined attapulgite; take 100 mg of the calcined attapulgite in a quartz glass dish, add 2000 ppm of toluene in a closed system, and carry out the adsorption-photocatalytic reaction with reference to the photocatalytic conditions of the third group in Test 7.

[0130] See Figure 6 , where (c) is the toluene degradation curve of the samples at different calcination temperatures. It is found that the removal rate reaches 82% when calcined at 400 °C.

[0131] 6.4 Degradation effect of catalysts formed by alkaline solutions with different concentrations on toluene

[0132] Samples: Attapulgite dual-effect catalysts (Samples 6 - 8) obtained by treating attapulgite with sodium hydroxide solutions of different concentrations in Examples 6 - 8, and original attapulgite soil (red soil, denoted as ATP).

[0133] Test method: Take 100 mg of each of the above samples in a quartz glass dish, add 2000 ppm of toluene in a closed system, and carry out adsorption-photocatalytic reaction with reference to the third group of photocatalytic conditions in Test 7.

[0134] See Figure 6 , where (d) is the toluene degradation curve of the dual-effect catalysts obtained with alkaline solutions of different concentrations. It is found that after treatment with 0.1 mol / L sodium hydroxide solution, the degradation removal rate of the attapulgite dual-effect catalyst for toluene reaches 85%, and the degradation efficiency is relatively high.

[0135] In summary, treating the original attapulgite soil with an ion exchange solution can improve the degradation effect on toluene; preferably, the dual-effect catalyst formed by ion exchange treatment of attapulgite with an acidic solution has a toluene degradation rate as high as 92%, and its adsorption and photocatalytic performance is better.

[0136] Test 7

[0137] Samples: The dual-effect catalyst prepared in Example 2, i.e., Sample 2.

[0138] Test method: Take 100 mg of the sample in a quartz glass dish, add 2000 ppm of toluene in a closed system, first carry out adsorption without light for 60 min at 65 °C, then carry out photocatalytic reaction under light irradiation for 120 min to carry out adsorption-photocatalytic reaction; repeat the above method for multiple adsorption-photocatalytic reactions to study the catalytic performance of the sample. The results are as Figure 7 shown.

[0139] From Figure 7 it can be seen that the attapulgite dual-effect catalyst has excellent stability, and its catalytic activity does not decrease significantly after five cyclic stability tests.

[0140] The above performance tests were carried out using the attapulgite dual-effect catalysts prepared in some examples. When using the attapulgite dual-effect catalysts prepared in other examples, they can all exhibit the same or similar catalytic performance.

[0141] In summary, the present invention forms a palygorskite dual-effect catalyst by simply treating the original palygorskite with acid or alkali. The preparation cost is low, and the palygorskite dual-effect catalyst has a large specific surface area, a rich pore structure, and excellent adsorption performance. The palygorskite dual-effect catalyst can degrade VOCs through adsorption and photocatalytic oxidation, that is, first concentrate the VOCs through adsorption, and then carry out photocatalytic oxidation decomposition on the concentrated VOCs, greatly improving the removal efficiency of VOCs and reducing energy consumption.

[0142] It should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a attapulgite dual-effect catalyst, characterized in that: The following steps are involved: S1. Take attapulgite and dispersant and fully dissolve them in water, let them stand, and centrifuge to obtain a suspension; S2. Add an ion exchange solution to the suspension of step S1, mix and react, and then stir, centrifuge, dry, grind and sieve in sequence to obtain a attapulgite dual-effect catalyst; the mass volume ratio of the attapulgite original soil, dispersant, ion exchange solution and water is (1-3) g: (0.1-0.5) g: (1-5) ml: (5-20) ml; the concentration of the ion exchange solution is 0.01 mol / L-3 mol / L.

2. The method for preparing the attapulgite dual-effect catalyst according to claim 1, characterized in that: In the step S1, the dispersant is sodium polymetaphosphate, sodium pyrophosphate, sodium metasilicate or sodium disilicate.

3. The method for preparing the attapulgite dual-effect catalyst according to claim 1, characterized in that: In the step S1, the attapulgite original soil is soaked for 11h-13h for purification before dissolving.

4. The method for preparing the attapulgite dual-effect catalyst according to claim 1, characterized in that: In the step S1, the solution is fully dissolved for 1 h to 2 h, and the standing time is 12 h to 24 h.

5. The method for preparing the attapulgite dual-effect catalyst according to claim 1, characterized in that: In step S2, the ion exchange solution is an acidic solution or an alkaline solution; the concentration of the acidic solution is 0.1 mol / L-3 mol / L; the concentration of the alkaline solution is 0.01 mol / L-0.2 mol / L.

6. The method for preparing the attapulgite dual-effect catalyst according to claim 1, characterized in that: In the step S2, the mixture is stirred for 12 h to 24 h and passed through a 100-200 mesh sieve.

7. The attapulgite dual-effect catalyst prepared by the method for preparing the attapulgite dual-effect catalyst according to claim 1.

8. Use of the attapulgite dual-effect catalyst as claimed in claim 7 in degrading VOCs gas.

9. The attapulgite dual-effect catalyst as claimed in claim 7 is used in the degradation of toluene through adsorption-photocatalytic coupling.

10. The use according to claim 9, characterized in that: In the application, in a closed system, the toluene concentration is 2000ppm, the dosage of the attapulgite dual-effect photocatalyst is 20mg-120mg, the reaction is carried out at 65°C without light for 60min, and then the reaction is carried out under light irradiation for 120min.

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