Method for preparing biological adsorbent for treating TVOC (Total Volatile Organic Compound) by using dandelion

Abstract

The invention discloses a method for preparing a biological adsorbent for treating TVOC (Total Volatile Organic Compound) by using dandelion, which comprises the following steps: soaking dandelion in a 0.5 mol / L sodium hydroxide solution for 1.32 hours, and washing with flowing water until the dandelion is neutral; drying the cleaned dandelion for later use; transferring a 0.077 mol / L sodium bicarbonate solution into a beaker, and carrying out water bath in a water bath box for 0.67 h; after the water bath is completed, the beaker is moved away, and the dandelion is washed clean; putting the cleaned dandelions into a drying oven, and bagging and storing after the dandelions are dried, so as to obtain the bio-adsorbent. According to the invention, dandelion is used as a raw material to prepare a novel pollution-free adsorbent, and transverse comparison with bamboo charcoal, activated carbon, diatomite, macroporous resin, optimized dandelion residue and original dandelion residue soil shows that the adsorption effect of chemically modified dandelion is better than that of the above materials through transverse experiments.

Description

Technical Field

[0001] The invention relates to the technical field of air purification, and specifically discloses a method for preparing a biosorbent for treating TVOC by using dandelion. Background Art

[0002] Indoor gas pollutants are divided into organic pollutants and inorganic pollutants: organic harmful gas pollutants mainly include volatile organic compounds (VOCs) S (Volatile Organic Compound), TVOC refers to volatile organic compounds, that is, a general term for various organic compounds that are emitted into the air in the form of water vapor at room temperature. It includes homologues of benzene, toluene, xylene, and more than 100 compounds such as phenols. TVOC includes: benzene, toluene, xylene and ether, which are commonly found in the polluted atmosphere released from solid wood furniture, composite wood flooring, density board, paint, adhesives and other materials. In indoor environments, the concentration level of TVOC is positively correlated with the degree of indoor air pollution. TVOC has a pungent odor. When the concentration of TVOC in indoor air reaches a certain level, people will feel uncomfortable and may even cause symptoms such as headaches and nausea. TVOC may cause humans to suffer from a variety of different hazards, including: changes in smell, irritant reactions, allergic reactions, liver diseases, neuropsychiatric disorders, and irritation of the skin and surrounding tissues. It is very harmful to human health. Long-term exposure to this environment will affect the central nervous system of the human body, and in severe cases, it can damage the liver and hematopoietic system.

[0003] At present, common preventive measures for TVOC include: opening windows for ventilation, choosing furniture made of environmentally friendly materials, washing with alkaline solutions or wiping furniture surfaces and walls with organic solvents, and using plants to purify the air. Studies have shown that plants such as green radish, spider plants, miniature coconuts, and monstera have a strong purification effect on indoor environmental pollutants. However, their adsorption effect is slow. These plants have the ability to absorb, remove, and decompose a variety of toxic and harmful gases, but their decomposition ability is greatly affected by environmental conditions and cannot usually be used alone as a purification material. During the growth process, the absorbed toxic and harmful gases are converted into non-toxic and harmless substances through photosynthesis, but toxic and harmful gases cannot be degraded into non-toxic and harmless substances. In addition to the adsorption effect on toxic and harmful gases such as benzene, toluene, and xylene, it has a decomposition effect on other toxic and harmful gases such as formaldehyde.

[0004] At present, my country's requirements for environmental quality are increasing day by day. At the same time, with the development of social economy, people pay more attention to the air quality of indoor residences. A large amount of TVOC will be generated in newly renovated houses, and the existing TVOC treatment technology is not mature enough. One is through ventilation through opening windows, and the other is through adsorption by activated carbon, but the treatment effect is not ideal. Therefore, seeking an efficient and multifunctional adsorbent is an important direction to solve the problem of air pollution. Dandelion, also known as dandelion or yellow flower agave, is a plant in the Asteraceae family. After chemical modification, biological adsorption materials are obtained to prepare high-performance, green and environmentally friendly recyclable biological adsorbents. Summary of the invention

[0005] In view of the above shortcomings, the present invention takes dandelion as the research object, and determines the optimal experimental conditions for dandelion modification through comprehensive analysis of slag making process, raw material cost and adsorption efficiency. The present invention is achieved through the following technical solutions:

[0006] The inventors conducted an optimal screening of three conditions that affect TVOC adsorption by sodium bicarbonate modification, including water bath time, sodium bicarbonate concentration and immersion time, set the three conditions to level 0, and drew a level coding table.

[0007] Table 1 TVOC level coding table

[0008]

[0009] According to the factor level coding table, the DPS software was used to obtain a three-factor five-level quadratic orthogonal rotation combination design table. A total of 23 experiments were conducted, and the optimization experiment table was completed according to the quadratic regression table and the level coding table. The experimental conditions for each group of experiments were obtained according to the method of the sodium bicarbonate pretreatment experiment. Finally, the optimized residue was dried and crushed, and the residue prepared by 23 experiments was used to test the adsorption rate. The data was processed by DPS to obtain the optimal conditions of the three influencing factors. As shown in Table 2:

[0010] Table 2 Quadratic regression optimization experiment table

[0011]

[0012]

[0013] Single factor experiment for optimal experiment

[0014] Through the optimization experiment, a large amount of residue was prepared, and the experiment was further optimized. When other conditions remained unchanged, single-factor experiments were conducted on the residue particle size, addition amount and temperature of the modified dandelion, and the experimental results were analyzed.

[0015] a. Particle size of modified dandelion residue

[0016] After the optimal experiment was completed, the large amount of prepared residue was crushed with a grinder and sieved with 8-mesh, 18-mesh, 40-mesh, 60-mesh, and 80-mesh sieves. After obtaining different amounts of residue, 1g was weighed and placed in a petri dish. The adsorption of TVOC by modified dandelion was tested under the same conditions.

[0017] b. Temperature

[0018] Weigh 1 g of each of 5 optimized experimental samples and put them in a culture dish, and place them in an experimental box at five temperatures of 19°C, 21°C, 23°C, 25°C, and 27°C. Under the condition that other conditions are the same, the data of TVOC adsorption by modified dandelion are measured and analyzed.

[0019] c. Addition amount

[0020] Weigh 1g, 2g, 3g, 4g, and 5g of the obtained residue and put it in a culture dish, and put it in an experimental box for adsorption under the condition that other conditions remain unchanged, measure various data, and analyze them.

[0021] Adsorption isotherm

[0022] The ratio of the amount of gas adsorbed per unit area per unit time by a unit volume of adsorbate to the number of gas molecules is called the adsorption isotherm. The model used under constant temperature conditions is the Freundlich and Langmuir isotherms for fitting.

[0023] The expression of the Langmuir isotherm is: c / q = c / Q m +1 / Q m b

[0024] The expression of the Freundlich isotherm is: q = K·C n

[0025] Taking the logarithm of both sides of the above equation can turn it into a linear form: lgq=lgK+nlgc

[0026] Experimental steps: Make five closed empty boxes of the same size and sequence them. Ignite the pollution source in the five empty boxes. When the TVOC concentration in the five boxes is 1.5mg / m 3 , 1.6mg / m 3 , 1.7mg / m 3 , 1.8mg / m 3 , 1.9mg / m 3 When 1 g of material is added, the TVOC content in the box is continuously recorded after 30 minutes and then fitted with the isothermal curve.

[0027] Drawing of adsorption kinetic curve

[0028] In the study of adsorption kinetics, pseudo-first-order and pseudo-second-order kinetic equations are usually used to fit the experimental data to analyze the relationship between the adsorption performance and time and to design an efficient adsorption system.

[0029] The Lagergren pseudo-first-order kinetic model expression is: lg(Qq) = lgQ-k1t / 2.303

[0030] Ho pseudo-second-order kinetic model expression is: t / q = 1 / (k2×Q) + t / Q

[0031] Experimental steps: Make five empty boxes of the same size, put the petri dish with the pollution source ignited in each of them, and when the TVOC content in the box stabilizes at 1.95mg / m 3 Five portions of 1g modified material were taken and placed in a box, and the data of TVOC detector were read at 30min, 50min, 70min, 90min and 110min. The adsorption rate at different times was calculated, and the pseudo-first-order kinetic model and pseudo-second-order kinetic model were used to fit the experimental data.

[0032] Comparison of experimental temperatures

[0033] Depend on Figure 1 It can be obtained that when the temperature is 27°C, the adsorption rate reaches 26.84%, which has the best adsorption effect on TVOC. As the experimental temperature increases, the adsorption rate increases accordingly.

[0034] Table 3 Thermodynamic parameters

[0035]

[0036] Depend on Figure 2 The correlation coefficient R of TVOC adsorption of dandelion was optimized. 2 It is 0.9847, close to 1. Analysis shows that the process is an endothermic process, indicating that the reaction is spontaneous. The free energy (ΔG) is less than zero, and the adsorption entropy (ΔS) is greater than zero, indicating that the adsorption process conforms to the thermodynamic model.

[0037] Adsorption isotherm study analysis

[0038] The curve drawn according to the isotherm formula is shown in Figure 3 ,according to Figure 3 Fitting isotherm curve, see Figure 4 and Figure 5 .

[0039] Table 4 Isotherm parameters

[0040]

[0041] Depend on Figure 4-5From Table 4, we can get the Freundlich isotherm curve R 2 is 0.988 and the Langmuir isotherm curve R 2 is 0.9126. The Freundlich equation fits better than the Langmuir equation. This shows that the adsorption of TVOC by modified dandelion is multi-molecular layer and multi-site adsorption.

[0042] Adsorption kinetics analysis

[0043] Modified dandelion adsorption kinetics curve, see Figure 6 .

[0044] Depend on Figure 6 It can be seen that the adsorption amount increases with the increase of time. The pseudo-first-order and pseudo-second-order kinetic curves are fitted according to the kinetic parameters at each level. Figure 7 and Figure 8 As shown:

[0045] Table 5 Kinetic parameters

[0046]

[0047] The experimental data were fitted with dynamics to obtain Figure 7-8 and Table 5, where the pseudo-primary power R 2 is 0.9683, quasi-secondary power R 2 It is 0.9976. 0.9976 is closer to 1, which conforms to the pseudo-second-order kinetic equation, indicating that the adsorption process is mainly chemical adsorption and supplemented by physical adsorption.

[0048] According to the above experiments, the present invention has obtained the best experimental method, which is as follows:

[0049] The present invention first discloses a method for preparing a biosorbent for treating TVOC using dandelion, comprising the following steps:

[0050] (1) Soak dandelions in a sodium hydroxide solution and then wash with running water until they are neutral;

[0051] (2) Dry the washed dandelions for later use;

[0052] (3) Transfer the sodium bicarbonate solution to a beaker and place it in a water bath;

[0053] (4) After the water bath is finished, remove the beaker and rinse the dandelions;

[0054] (5) Put the washed dandelions into a drying oven, and after the dandelions are dried, pack them into bags for storage, thereby obtaining a biosorbent.

[0055] Furthermore, in step (1), the sodium hydroxide concentration is 0.4-0.6 mol / L, and the soaking time is 1.2-1.5 h.

[0056] Furthermore, the sodium hydroxide concentration is 0.5 mol / L, and the soaking time is 1.32 h.

[0057] Furthermore, in step (3), the concentration of the sodium bicarbonate solution is 0.06-0.08 mol / L, and the water bath time is 0.5-1.0 h.

[0058] Furthermore, the concentration of the sodium bicarbonate solution is 0.077 mol / L, and the water bath time is 0.67 h.

[0059] The invention also discloses a biosorbent prepared according to the preparation method.

[0060] The beneficial effects of the present invention are:

[0061] The present invention uses dandelion as raw material to prepare a new type of pollution-free adsorbent, and studies its mechanism of adsorbing TVOCs. First, four different pretreatments are performed on dandelion, and combined with factors such as the difficulty and cost of the production process, it is obtained that the best process with a good absorption effect on TVOC is sodium bicarbonate modification. Then, by using a quadratic regression orthogonal rotation combination experiment, the selected method is further optimized to achieve a better effect, so that the best experimental conditions are determined to be: when the concentration of sodium bicarbonate reaches 0.077 mol / L, the standing time of sodium hydroxide is 1.32 h, and the water bath time is 0.67 h. It is obtained that the predicted adsorption rate of TVOC is 26.70%, the measured value is 25.13%, and the ratio is close to 1, indicating that the prediction is reasonable and the model is also credible. Then, the role of these factors in the experiment is analyzed. A horizontal comparison is made with bamboo charcoal, activated carbon, diatomaceous earth, macroporous resin, optimized dandelion residue and original dandelion residue. Through horizontal experiments, it can be concluded that the chemically modified dandelion has a better adsorption effect than the above materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is the effect of temperature on the adsorption effect;

[0063] Figure 2 is the adsorption thermodynamic curve;

[0064] Figure 3 is the effect of concentration on adsorption;

[0065] Figure 4 is L-isotherm;

[0066] Figure 5 is the F-isotherm;

[0067] Figure 6is the adsorption kinetic curve;

[0068] Figure 7 It is a pseudo-first-order kinetic curve;

[0069] Figure 8 It is a pseudo-second-order kinetic curve;

[0070] Fig. 9 A comparison diagram of the adsorbent prepared by the present invention and other adsorbent materials;

[0071] Fig.10 The results of scanning electron microscopy observations of different dandelions are shown below, where A is the original dandelion and B is the modified dandelion.

[0072] Fig.11 Infrared spectrum; a is the modified dandelion, b is the original dandelion and c is the dandelion after adsorption

[0073] Fig.12 It is a potential and particle size analyzer; among them: a is the original dandelion, b is the adsorbed dandelion, and c is the modified dandelion;

[0074] Fig.13 This is the desorption regeneration diagram. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0076] Unless otherwise defined, the technical or scientific terms used herein shall have the common meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "an" do not indicate quantity restrictions, but indicate the existence of at least one.

[0077] Example 1

[0078] A method for preparing a biosorbent for treating TVOC using dandelion:

[0079] (1) Soak dandelions in 0.5 mol / L sodium hydroxide solution for 1.32 h, and then wash with running water until they are neutral;

[0080] (2) Dry the washed dandelions for later use;

[0081] (3) Transfer 0.077 mol / L sodium bicarbonate solution into a beaker and place in a water bath for 0.67 h;

[0082] (4) After the water bath, remove the beaker and rinse the dandelions;

[0083] (5) Put the washed dandelions into a drying oven, and after the dandelions are dried, pack them into bags for storage, thereby obtaining a biosorbent.

[0084] Comparative Example 1

[0085] Microwave-assisted treatment of dandelion with ethyl acetate

[0086] (1) Processing raw materials: Wash the collected dandelions with running water to remove dust on the surface, dry them to constant weight, and weigh 100 g; boil the dandelions in boiling water for 30 minutes;

[0087] (2) Rinse: rinse with running water for a while;

[0088] (3) Ethanol immersion and water bath: Prepare five ethanol solutions with different volume ratios, with a volume ratio of 1:2; immerse the materials in equal amounts in the five solutions, and then place them in a constant temperature water bath at 80°C for 60 min;

[0089] (4) Rinse: Rinse with running water until the pH value is neutral as tested by pH paper;

[0090] (5) Microwave-assisted ethyl acetate treatment: Equal amounts of dandelions were soaked in ethyl acetate with an equal volume concentration of 20% and microwaved for 15 min;

[0091] (6) Rinse: Rinse with running water until neutral;

[0092] (7) Drying: Place the cleaned neutral dandelions in a forced air drying oven and dry at a constant temperature (temperature of 80° C.) until constant weight is reached;

[0093] (8) Grinding and sieving: Grind the dried dandelions with a grinder, pass through a 40-mesh sieve, weigh, and put into a plastic bag for later use.

[0094] Test Example 1

[0095] Comparison of the adsorption of TVOC by the dandelion adsorbents prepared in Example 1 and Comparative Example 1

[0096] Determination of TVOC empty box leakage rate: Light the mosquito coil, put it into the sealed box, burn it for 1 minute, take out the pollution source, quickly seal the sealed box, wait for 5 minutes, so that the TVOC in the air in the box can be evenly diffused. Put it into the detector, when the value is between 1.8-1.97, record the data, wait for 0.5 hours, put it into the detector, and read the data C after the instrument value is stable. Leakage rate calculation formula: P = (C0-C) × 100% / C0

[0097] Determination of TVOC adsorption by dandelion: Same as the leakage rate determination, light the mosquito coil, put it into the detector, and record the data (C0) when the value is between 1.8-1.97. Pour the treated residue into 2 culture dishes, put them into the airtight box, and quickly seal it. Wait for 30 minutes, put it into the detector, and read the data and remove the residue after the instrument value stabilizes.

[0098] According to the above method, the adsorption rates of the two kinds of residues prepared by the treatment of Example 1 and Comparative Example 1 were measured respectively to judge the adsorption effects of the two methods on TVOC.

[0099] The calculation formula of the adsorption rate of modified dandelion to TVOC is: (C0-C)×100% / C0-P

[0100] The specific results are shown in Table 6. It can be seen that the dandelion sample prepared by the process of the present invention has a better effect on the adsorption rate of TVOC than the technical means of Comparative Example 1 (using microwave-assisted ethyl acetate to treat dandelion), and can obtain a higher TVOC adsorption rate in a shorter time.

[0101] Table 6

[0102] TVOC adsorption rate / time 30min 50min 70min 90min 110min Example 1 25.0％ 31.5％ 36.2％ 39.8％ 43.7％ Comparative Example 1 19.8％ 22.6％ 26.5％ 30.6％ 35.9％

[0103] Test Example 2

[0104] Commercially available adsorbent materials were compared with the original residue and the optimized residue for the adsorption of TVOC.

[0105] Weigh 1g of resin, modified sample, diatomaceous earth, original sample, bamboo charcoal, and activated carbon and place them in a petri dish. Make 6 closed empty boxes of the same size. Light the pollution source and place it in the six empty boxes. When the TVOC content in the box is 1.95mg / m 3 After stabilization, the six samples were placed in six boxes for adsorption for 0.5 h respectively, and the instrument data were read and analyzed. Fig. 9 It is a comparison of the adsorption rate of modified dandelion and other commercially available adsorption materials. Within a certain period of time, it was found that modified dandelion was better than other adsorption materials, among which macroporous resin and bamboo charcoal had the worst adsorption effects, diatomaceous earth had an adsorption effect lower than that of modified dandelion, but higher than other materials, followed by activated carbon.

[0106] Test Example 3

[0107] Characterization and analysis of modified dandelion

[0108] a. Scanning electron microscopy

[0109] The adsorbed and original dandelion residues were observed with an electron microscope and then microscopically analyzed with four common adsorption materials to observe their microscopic morphology, physical structure, etc., so as to obtain the surface microscopic characteristics of the samples.

[0110] b. Element Analyzer

[0111] The original dandelion residue, the optimized dandelion residue and the adsorbed dandelion residue were ground through a 100-mesh sieve using an elemental analyzer, and the contents of C, N, H and S in the three residues were detected using an elemental analyzer.

[0112] c. Zeta potential and particle size analyzer

[0113] Potential analyzer is a method to determine the surface potential of materials. It can accurately measure the Zeta potential of the material surface and calculate the average particle size, zeta potential, surface charge density, etc. of the material.

[0114] Zeta potential refers to the surface potential of a material to water molecules or cations (such as NH4 + , KCl) adsorption capacity. Usually, we believe that the concentration of ions generated by water molecules acting on the particle surface can be used to determine the size of the particles. When measuring the particle size of a material, this instrument is mainly used to determine the potential and surface charge density of the material surface.

[0115] d. FTIR analysis Fourier transform infrared spectroscopy

[0116] It can detect and analyze the vibration of chemical bonds. Its principle is that the infrared spectrum of the substance can analyze the functional groups of the compound and check the change rules of its chemical structure. FTIR is used to observe the unmodified material, modified material and adsorbed material to analyze its adsorption mechanism.

[0117] Characterization analysis results

[0118] 1. Scanning electron microscope observation

[0119] The optimized dandelions and original dandelions were dried at 85°C for more than 14 hours to remove the moisture inside the materials and avoid the appearance of water molecules under microscopic scanning. Fig.10 A and Fig.10B concluded that the optimized dandelion is looser than the original dandelion residue, which means that the modified dandelion opens the microscopic molecules of the original material, increases the adsorption area of ​​the modified dandelion, increases the adsorption rate, and can better adsorb pollutants.

[0120] 2. Infrared spectroscopy analysis

[0121] Depend on Fig.11 It can be seen that there are three curves, a for the optimized dandelion material, b for the original dandelion and c for the dandelion after adsorption. The image generated by the spectrometer shows that the optimized dandelion has fluctuations and peaks in certain groups, at 3412cm -1 、1639cm -1 、1400cm -1 and 1060cm -1 There are fluctuations. This indicates that certain groups play a certain role in optimizing dandelion adsorption.

[0122] 4. Elemental analysis

[0123] Table 7 Elemental analysis

[0124]

[0125] From Table 7, it can be concluded that the carbon content of the three materials is about 40%, among which the carbon content of the dandelion residue after adsorption is the highest. The sulfur content of the optimized dandelion is lower than that of the original dandelion, while the content of hydrogen and carbon elements after optimization is higher than that of the original. In conclusion, the optimized dandelion can remove pollutants in the environment.

[0126] 5. Zeta potential and particle size analyzer

[0127] Depend on Fig.12 It can be seen that the particle size and dispersion coefficient of the three materials are different. From left to right, a is the original dandelion, b is the adsorbed dandelion, and c is the optimized dandelion. The dispersion coefficient of the optimized dandelion decreases, the potential also changes, and the dispersion coefficient after adsorption also changes, indicating that the adsorption effect is achieved.

[0128] Test Example 4

[0129] Desorption regeneration

[0130] Depend on Fig.13 It was found that with the increase in the number of experimental repetitions, the adsorption rate of TVOC by the optimized dandelion continued to decrease. After the fourth desorption, the adsorption rate of TVOC by the optimized dandelion was greatly reduced, indicating that the optimized dandelion can be reused.

[0131] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0132] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This description method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a biosorbent for treating TVOC using dandelion, comprising the following steps: (1) Soak dandelions in sodium hydroxide solution and wash with running water until they are neutral; (2) Dry the washed dandelions for later use; (3) Transfer the sodium bicarbonate solution to a beaker and place it in a water bath; (4) After the water bath, remove the beaker and rinse the dandelions; (5) Put the washed dandelions into a drying oven, and after the dandelions are dried, pack them into bags for storage, thereby obtaining a biosorbent.

2. The method according to claim 1, wherein: The sodium hydroxide concentration in step (1) is 0.4-0.6 mol / L, and the soaking time is 1.2-1.5 h.

3. The method according to claim 2, wherein: The sodium hydroxide concentration is 0.5 mol / L, and the soaking time is 1.32 h.

4. The method according to claim 1, wherein: The concentration of the sodium bicarbonate solution in step (3) is 0.06-0.08 mol / L, and the water bath time is 0.5-1.0 h.

5. The method according to claim 4, wherein: The concentration of the sodium bicarbonate solution is 0.077 mol / L, and the water bath time is 0.67 h.

6. A biosorbent prepared according to the method of any one of claims 1 to 5.

7. Use of the biosorbent according to claim 6 in treating TVOC.

Images