Modified highland barley straw as well as preparation method and application thereof
By assisting ethyl acetate to modify barley straw, it improves its adsorption ability to formaldehyde, solves the problems of poor effect of existing adsorbents and poor reuse effects, and achieves efficient and reusable formaldehyde adsorption effect.
Patent Information
- Application Number
- CN202411839724.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-02-25
AI Technical Summary
Existing formaldehyde adsorbents such as activated carbon and bamboo charcoal have poor adsorption effect on formaldehyde, and the reused effect is not ideal, so they cannot effectively remove formaldehyde in the air.
Ethyl acetate-assisted neutral protease to modify barley straw, improve its -OH, CH3 and carbon-containing single chain content, thereby increasing its adsorption ability to formaldehyde.
The adsorption rate of modified barley straw to formaldehyde reached 22.934%, which is significantly better than traditional adsorbents, and can be reused at least seven times.
Smart Images
Figure CN119500073A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of biosorbents, and in particular relates to modified highland barley straw and a preparation method and application thereof. Background Art
[0002] Formaldehyde is a naturally occurring organic compound, a colorless and irritating gas that is irritating to the eyes and nose and is listed as a known human carcinogen. Therefore, more and more attention is paid to the removal of formaldehyde, and the indoor air quality standard GB / T18883-2002 stipulates that the formaldehyde content should not exceed 0.08mg / m 3 At present, the main adsorbents for formaldehyde are activated carbon, bamboo charcoal, etc., but the above adsorbents have poor formaldehyde adsorption effects and unsatisfactory effects when reused.
[0003] Highland barley belongs to the genus Hordeum of the Poaceae family. It is a variant of barley and an annual or biennial herb. Highland barley has a short growth and development cycle. It is the main food crop, fuel and livestock feed for residents in Tibetan areas. It is also the raw material for the production of beer, medicines and health products. Highland barley straw is the general name for the stems and leaves (ears) of mature crops, and the flower spikes are yellow-brown. Tibet is the main highland barley growing area, and highland barley is widely planted in these areas, so the highland barley straw resources are very rich. At present, the way to use highland barley straw in life is often to feed livestock as feed and return it to farmland as nutrient. There is also the modification of highland barley straw with alkali solution to adsorb Cu in water. 2+ Or heavy metals in the soil. It can be seen that the modified highland barley straw obtained by the current modification method can only be used to treat heavy metals, and cannot achieve the adsorption of harmful substances in the air such as formaldehyde. Summary of the invention
[0004] In order to solve the above technical problems, the present invention provides a modified highland barley straw and a preparation method and application thereof. The highland barley straw is modified by ethyl acetate-assisted neutral protease, and the obtained modified highland barley straw can efficiently adsorb formaldehyde in the air.
[0005] To achieve the above objectives, the technical solutions of the present invention are specifically as follows.
[0006] The first aspect of the present invention provides a method for preparing modified highland barley straw, comprising the following steps:
[0007] After hot steaming, highland barley straw is soaked in an ethyl acetate solution for 21 to 39 minutes, added into a neutral protease solution to increase the content of -OH, CH3 and carbon-containing single chains in the highland barley straw, reacted at 50 to 55 degrees Celsius for 28 to 30 minutes, inactivated, dried, and crushed to obtain the modified highland barley straw; the modified highland barley straw is used for formaldehyde adsorption;
[0008] The concentration of the ethyl acetate solution is 0.02 mol / L to 0.18 mol / L;
[0009] The concentration of the neutral protease is 0.02 mol / L to 0.18 mol / L.
[0010] The invention soaks highland barley straw in an ethyl acetate solution with a concentration of 0.02 mol / L to 0.18 mol / L for 21 to 39 minutes, and reacts in a neutral protease solution with a concentration of 0.02 mol / L to 0.18 mol / L for 28 to 30 minutes at 50 to 55 degrees Celsius, thereby increasing the content of -OH, CH3, carbon-containing single chains, and the content of C and H elements in the highland barley straw, thereby making the obtained modified highland barley straw have a good adsorption effect on formaldehyde. Compared with the formaldehyde adsorption rates of 11.84% of activated carbon and 19.1227% of bamboo charcoal in the prior art, the formaldehyde adsorption rate of the modified highland barley straw prepared in the invention can reach 22.934%.
[0011] In another preferred embodiment, the particle size of the modified highland barley straw is 60 mesh to 100 mesh.
[0012] In another preferred embodiment, the mass volume ratio of the highland barley straw to the neutral protease solution is 10kg:50L-55L.
[0013] In another preferred embodiment, the enzyme inactivation temperature is 70°C to 73°C and the time is 8 min to 10 min.
[0014] In another preferred embodiment, the steaming time is 15 min to 20 min.
[0015] The second aspect of the present invention provides the modified highland barley straw.
[0016] The third aspect of the present invention provides the use of the modified highland barley straw in the preparation of formaldehyde scavengers.
[0017] The fourth aspect of the present invention provides a method for removing formaldehyde, which comprises placing the modified highland barley straw in a gas containing formaldehyde, and utilizing the modified highland barley straw to adsorb formaldehyde to remove formaldehyde from the gas.
[0018] In another preferred embodiment, the ratio of the amount of highland barley straw used to the amount of formaldehyde adsorbed is 3g:0.42mg-0.45mg.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] (1) The modified highland barley straw prepared by the present invention with the assistance of ethyl acetate neutral protease has a good adsorption effect on formaldehyde. The use of ethyl acetate to assist neutral protease can effectively increase the content of -OH, CH3, carbon-containing single chains, and the content of C and H elements in highland barley straw, and electron microscopic analysis shows that the crushed surface area of the modified highland barley straw is increased, which is more conducive to the adsorption of formaldehyde; through the BET experiment, the specific surface area, pore volume, etc. are measured, and the specific surface area parameters obtained can intuitively illustrate that the pore size of the modified highland barley straw surface is larger than that of the unmodified highland barley straw surface. Therefore, the modified highland barley straw can provide adsorption sites, thereby achieving efficient adsorption of formaldehyde. The modified highland barley straw prepared by the method of the present invention only requires 3g, and at a formaldehyde concentration of 1.8mg / m 3 Under the conditions, the adsorption rate of formaldehyde can reach 24.17% in 150 minutes.
[0021] (2) The formaldehyde adsorption performance of the modified highland barley straw in the present invention is significantly better than that of diatomaceous earth, activated carbon, resin, bamboo charcoal and the original material. The modified highland barley straw can be recycled at least seven times. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a 3D diagram of the two-factor interaction effect of neutral protease concentration and ethyl acetate concentration on formaldehyde removal rate.
[0023] Figure 2 This is the graph showing the adsorption capacity and formaldehyde removal rate of alkaline heat-treated modified highland barley straw.
[0024] Figure 3 The adsorption capacity and formaldehyde removal rate of modified highland barley straw after citric acid-assisted cellulase treatment.
[0025] Figure 4 The adsorption capacity and formaldehyde removal rate of highland barley straw after modification with ethyl acetate-assisted neutral protease.
[0026] Figure 5 This is the result graph of the adsorption amount and formaldehyde removal rate after calcium chloride-assisted hemicellulase modification of highland barley straw.
[0027] Figure 6 This is a graph showing the effect of different particle sizes on the adsorption performance of modified highland barley straw.
[0028] Figure 7 This is a graph showing the effect of the amount of modified highland barley straw added on the adsorption performance of modified highland barley straw.
[0029] Figure 8 This is a diagram showing the effect of adsorption temperature on the adsorption performance of modified highland barley straw.
[0030] Fig. 9 This is a graph showing the effect of formaldehyde concentration on the adsorption performance of modified highland barley straw.
[0031] Fig.10 This is a graph showing the effect of adsorption time on the adsorption performance of modified highland barley straw.
[0032] Fig.11 These are infrared spectra of different highland barley straws, where a is the original highland barley straw, b is the modified highland barley straw, and c is the modified highland barley straw after adsorption.
[0033] Fig.12 These are electron microscope pictures of the adsorption materials; A is the original highland barley straw, B is the modified highland barley straw, and C is the highland barley straw after adsorption.
[0034] Fig.13 This is the effect of concentration on adsorption effect.
[0035] Fig.14 This is the result of Langmuir analysis.
[0036] Fig.15 This is the result of Freundlich analysis.
[0037] Fig.16 This is the adsorption kinetic curve result diagram.
[0038] Fig.17 This is the result graph of the pseudo-first-order rate equation curve.
[0039] Fig.18 This is the result graph of the pseudo-second-order rate equation curve.
[0040] Fig.19 This is a comparison of the formaldehyde adsorption performance of different materials.
[0041] Fig. 20 This is the adsorption result graph of modified highland barley straw. DETAILED DESCRIPTION
[0042] The following will be combined with the specific implementation of the present invention to clearly and completely describe the technical solution in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0043] The methods described in the embodiments of the present invention are conventional methods unless otherwise specified. The materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified.
[0044] In daily life, straw is often used as feed for livestock and as nutrients in farmland. At present, the main air purification technologies include indoor plant purification, physical adsorption, chemical adsorption, photocatalytic purification technology, and the establishment of a joint prevention and control mechanism for air pollution. The current research status of highland barley straw is that it can absorb Cu in water after being modified with alkali solution. 2+ Or heavy metals in the soil. It can be seen that the modified highland barley straw obtained by the current modification method can only be used to treat heavy metals, and cannot achieve the adsorption of harmful substances in the air such as formaldehyde.
[0045] The invention uses farmland waste highland barley straw as raw material, performs modification and optimization on it, and uses it to prepare a biological adsorbent for adsorbing formaldehyde. Through a specific modification method of acetic acid assisted neutral protease, the modified highland barley straw has a good adsorption effect on formaldehyde, which is far superior to adsorbents such as bamboo charcoal and activated carbon in the prior art, and has a good adsorption effect after repeated cycles for 7 times.
[0046] The following is a detailed description of a modified highland barley straw and its preparation method and application.
[0047] The highland barley straw in the following embodiments was collected in Tibet.
[0048] Ethyl acetate, sodium hydroxide, citric acid, activated carbon, bamboo charcoal, and diatomaceous earth were purchased from Tianjin Ruijinte Chemical Co., Ltd., neutral protease was purchased from Tianjin Yongda Chemical Reagent Co., Ltd., cellulase and hemicellulase were purchased from Tianjin Damao Chemical Reagent Factory, macroporous adsorption resin AB-8 was purchased from Donghong Chemical Co., Ltd., and calcium chloride was purchased from Luoyang Haohua Chemical Reagent Co., Ltd.
[0049] Example 1
[0050] A method for preparing modified highland barley straw comprises the following steps:
[0051] S1. Weigh 10 g of highland barley straw and steam it in boiling water for 15 min to obtain treated highland barley straw.
[0052] S2, soaking the treated highland barley straw in an ethyl acetate solution with a concentration of 0.1 mol / L for 30 min, mixing the highland barley straw with a neutral protease solution with a concentration of 0.1 mg / mL according to a solid-liquid ratio of 10 g:50 mL, and bathing the mixture in a constant temperature water bath at 50° C. for 30 min to obtain enzyme-treated highland barley straw.
[0053] S3. Soaking the enzyme-treated highland barley straw in a constant temperature water bath at 70° C. for 10 min to inactivate the neutral protease, thereby obtaining enzyme-inactivated highland barley straw.
[0054] S4. Rinse the enzyme-inactivated highland barley straw with distilled water until it becomes neutral, dry it in a constant temperature forced air drying oven at 80° C., and grind it to obtain 60-mesh modified highland barley straw.
[0055] Example 2
[0056] A method for preparing modified highland barley straw comprises the following steps:
[0057] S1. Weigh 10 g of highland barley straw and steam it in boiling water for 18 min to obtain treated highland barley straw.
[0058] S2, soaking the treated highland barley straw in an ethyl acetate solution with a concentration of 0.02 mol / L for 30 min, mixing the highland barley straw with a neutral protease solution with a concentration of 0.02 mg / mL according to a solid-liquid ratio of 10 g:55 mL, and bathing the mixture in a constant temperature water bath at 55° C. for 28 min to obtain enzyme-treated highland barley straw.
[0059] S3. Soaking the enzyme-treated highland barley straw in a constant temperature water bath at 70° C. for 10 min to inactivate the neutral protease, thereby obtaining enzyme-inactivated highland barley straw.
[0060] S4. Rinse the enzyme-inactivated highland barley straw with distilled water until it becomes neutral, dry it in a constant temperature forced air drying oven at 80° C., and grind it to obtain 80-mesh modified highland barley straw.
[0061] Example 3
[0062] A method for preparing modified highland barley straw comprises the following steps:
[0063] S1. Weigh 10 g of highland barley straw and steam it in boiling water for 20 min to obtain treated highland barley straw.
[0064] S2, soaking the treated highland barley straw in an ethyl acetate solution with a concentration of 0.18 mol / L for 30 min, mixing the highland barley straw with a neutral protease solution with a concentration of 0.18 mg / mL according to a solid-liquid ratio of 10 g:50 mL, and bathing the mixture in a constant temperature water bath at 55° C. for 28 min to obtain enzyme-treated highland barley straw.
[0065] S3. Soaking the enzyme-treated highland barley straw in a constant temperature water bath at 70° C. for 10 min to inactivate the neutral protease, thereby obtaining enzyme-inactivated highland barley straw.
[0066] S4. Rinse the enzyme-inactivated highland barley straw with distilled water until it becomes neutral, dry it in a constant temperature forced air drying oven at 80° C., and grind it to obtain 100-mesh modified highland barley straw.
[0067] To further illustrate the adsorption effect of the modified hulless barley straw in the present invention, the following experiments were conducted.
[0068] 1. Optimization of preparation conditions for modified hulless barley straw
[0069] 1) The optimal conditions for the three main influencing factors were at the zero level. A level coding table for hulless barley straw was compiled, as shown in Table 1. Referring to the three-factor five-level coding table, the DPS software was used to obtain the three-factor five-level quadratic orthogonal rotational combination design table. According to its combination table, modified hulless barley straw was prepared and then used for adsorption.
[0070] Table 1 Factor level table of hulless barley straw
[0071]
[0072] According to the factor level coding table, the quadratic regression orthogonal rotational combination scheme of hulless barley straw obtained by using the DPS software is shown in Table 2. Twenty-three kinds of modified hulless barley straw were prepared according to Table 2 and used for the adsorption test of formaldehyde, and the removal rate was calculated.
[0073] Table 2 Quadratic regression orthogonal rotational combination scheme of modified hulless barley straw
[0074]
[0075]
[0076] 2) One-way analysis of variance: The one-way analysis of variance table of the modified hulless barley straw processed by the DPS software is shown in Table 3.
[0077] Table 3 One-way analysis of variance table of modified hulless barley straw
[0078] Sources of variation SS df MS F P <![CDATA[X1]]> 0.8222 1 0.8222 1.5621 0.2334 <![CDATA[X2]]> 5.01 1 5.01 9.519 0.0087 <![CDATA[X3]]> 0.0676 1 0.0676 0.1285 0.7258 <![CDATA[X1 2 ]]> 6.1027 1 6.1027 11.595 0.0047 <![CDATA[X2 2 ]]> 0.7514 1 0.7514 1.4276 0.2535 <![CDATA[X3 2 ]]> 4.1806 1 4.1806 7.943 0.0145 <![CDATA[X1X2]]> 4.0186 1 4.0186 7.6353 0.0161 <![CDATA[X1X3]]> 0.0406 1 0.0406 0.0772 0.7856 <![CDATA[X2X3]]> 0.505 1 0.505 0.9595 0.3452 return 21.6237 9 2.4026 F2＝4.565 0.0141 Remaining 6.8422 13 0.5263 - - Lack of Fit 4.4471 5 0.8894 F1＝2.971 0.0528 error 2.3951 8 0.2994 - - sum 28.4659 22 - - -
[0079] Note: SS represents the sum of squared deviations, df represents the degrees of freedom, MS represents the mean square, F represents the ratio of the mean square between groups to the mean square within groups, P represents the significant difference, - indicates that this item is not included, and the meanings appearing in the following tables are the same as this.
[0080] Through the variance analysis in Table 3, F1 = 2.971 < F0.05(5,8) = 4.82, that is, it did not reach the significant level, indicating that the influence of unknown factors on the experiment is very small and can be ignored; F2 = 4.565 > F0.01(9,13) = 4.19, reaching the extremely significant level, which means that the predicted value of the model is consistent with the actual situation and the model is established.
[0081] Model establishment and verification: Using DPS software to analyze the experimental results, it can be obtained that the regression equation between the neutral protease concentration X1, ethyl acetate concentration X2, ethyl acetate soaking time X3 and the removal rate Y of modified highland barley straw is:
[0082] Y=18.30676-0.24536X1+0.60568X2+0.07036X3+0.62482X 12 +0.22530X 22 +0.51
[0083] 875X 32 -0.70875X1X2-0.07125X1X3-0.25125X2X3.
[0084] 3) Quadratic ANOVA
[0085] Eliminate the insignificant items at the α = 0.10 level, and conduct quadratic ANOVA on the remaining items of the modified highland barley straw. The simplified regression equation is:
[0086] Y=18.30676+0.60568X2+0.62482X 12+ 0.51875X 32- 0.70875X1X2.
[0087] The quadratic ANOVA table of modified highland barley straw is shown in Table 4.
[0088] Table 4 Quadratic variance analysis table of modified highland barley straw
[0089] Sources of variation SS df MS F P <![CDATA[X2]]> 5.01 1 5.01 9.519 0.0089 <![CDATA[X1 2 ]]> 6.1027 1 6.1027 11.595 0.0047 <![CDATA[X3 2 ]]> 4.1806 1 4.1806 7.943 0.0145 <![CDATA[X1X2]]> 4.0186 1 4.0186 7.6353 0.0161 return 21.6237 9 2.4026 F2＝4.565 0.0141 Remaining 6.8422 13 0.5263 - - sum 28.4659 22 - - -
[0090] 4) Single factor effect
[0091] When exploring the impact of a single factor on the experimental results, other factors are set to zero level. The results in Table 5 and Figure 1 Shown
[0092] Table 5 Single factor effect of highland barley straw
[0093]
[0094]
[0095] 5) Analysis of two-factor interaction effect
[0096] Among the three two-factor interaction groups X1X2, X1X3, and X2X3, the two-factor interaction of X1X2 was more significant. The effects of neutral protease concentration and ethyl acetate concentration on formaldehyde removal rate Y are shown in Table 6.
[0097] Table 6 Effect of neutral protease concentration and ethyl acetate concentration on formaldehyde removal rate
[0098]
[0099] Through the analysis of Table 6, it is found that when the concentration of ethyl acetate remains unchanged, the concentration of neutral protease gradually increases, and the removal rate of formaldehyde by the modified highland barley straw gradually decreases; when the concentration of neutral protease remains unchanged, as the concentration of ethyl acetate gradually increases, the adsorption performance of modified highland barley straw for formaldehyde shows a trend of gradual increase. Figure 1 It can be seen that the removal rate is the highest, reaching 21.35%, at the horizontal point (-1.682, 1.682), that is, when the ethyl acetate concentration is 0.15 mol / L and the neutral protease concentration is 0.05 mg / mL.
[0100] Optimization analysis and verification: According to the data analysis processed by DPS software, when the Y value is the largest, X1 = -1.682, X2 = 1.682, X3 = -1.682, so the horizontal position of the three factors is (-1.682, 1.682, -1.682), that is, the concentration of neutral protease is 0.02mg / mL, the concentration of ethyl acetate is 0.18mol / L, and the immersion time of ethyl acetate is 21.5min. At this time, the predicted removal rate is 24.56%. Under this adsorption condition, the actual adsorption value measured in the experiment is 23.18%, and the measured value / predicted value is 94.38%, which is close to 1, so the combination is reliable.
[0101] 2. Adsorption effect of different enzyme-modified highland barley straw
[0102] 1) Alkali heat treatment method
[0103] Weigh 10g of highland barley straw and boil it in boiling water for 30min; put the boiled highland barley straw on a filter plate and rinse it with tap water until it is neutral; put the rinsed highland barley straw on a filter plate to control the water, and then divide it into five equal parts; use a conical flask to prepare five different concentrations of sodium hydroxide solution, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L respectively; add five equal parts of highland barley straw to five different concentrations of sodium hydroxide solution, and stir for several seconds. Place the highland barley straw in a constant temperature water bath for 30 minutes at 60°C; take out highland barley straw from five conical flasks and place them in a sieve, rinse them in tap water until they are neutral, and weigh them; drain the rinsed highland barley straw, spread them flat on a culture dish, stick label paper on them, and put them in a constant temperature blast drying oven for drying at 80°C; when the highland barley straw reaches a constant weight, take out the dry highland barley straw from the constant temperature blast drying oven, weigh it with a balance, crush it, pass it through a 60-mesh sieve, weigh it again after sieving, and then put them into sealed bags for storage.
[0104] 2) Citric acid treated cellulase
[0105] Weigh 10g highland barley straw and cook it in boiling water for 20min; prepare 0.15mol / L citric acid solution and put it in a 100mL beaker, then soak the cooked highland barley straw in the solution for 30min; prepare 0.1mg / mL, 0.2mg / mL, 0.3mg / mL, 0.4mg / mL, and 0.5mg / mL cellulase solutions respectively, divide the soaked highland barley straw into equal parts and put them into the cellulase solutions; put it in a digital constant temperature water bath for 30min, and the temperature is set to 50℃; then adjust the temperature of the digital constant temperature water bath to 70℃ to inactivate the enzyme for 10min; rinse with distilled water until neutral, put it in a culture dish and mark it, put it in a constant temperature blast drying oven at 80℃ to dry it, then weigh and record it; crush the dried highland barley straw through a 60-mesh sieve and record it again, then put it into sealed bags, label it and store it.
[0106] 3) Ethyl acetate-assisted neutral protease
[0107] Weigh 10g highland barley straw and cook it in boiling water for 20min; prepare 0.1mol / L ethyl acetate and put it in a 100mL beaker, then put the cooked highland barley straw into the beaker and soak it for 30min; prepare 0.1mg / mL, 0.2mg / mL, 0.3mg / mL, 0.4mg / mL, and 0.5mg / mL neutral protease solutions respectively, divide the highland barley straw into equal parts and put them into the neutral protease solution; put it into a digital display constant temperature water bath for a water bath for 30min, and the temperature is set to 50℃; then adjust the temperature of the digital display constant temperature water bath to 70℃ and soak it for 10min to inactivate the enzyme; rinse it with distilled water until it is neutral, put it in a culture dish and mark it, put it in a constant temperature blast drying oven at 80℃ to dry it, then weigh and record it; crush the dried highland barley straw through a 60-mesh sieve, weigh and record it again, and then put it into sealed bags, mark it, and store it.
[0108] 4) Calcium chloride treatment of hemicellulase
[0109] Weigh 10g highland barley straw and cook it in boiling water for 20min; put the cooked highland barley straw through a sieve to control water, and then divide it into 5 equal parts; prepare 5 parts of 0.1mol / L calcium chloride solution respectively, and then put the five equal parts of highland barley straw into the five solutions and soak them for 30min; prepare hemicellulase solutions with concentrations of 0.1g / L, 0.2g / L, 0.3g / L, 0.4g / L and 0.5g / L respectively, and put the highland barley straw soaked in the calcium chloride solution into the 5 hemicellulase solutions; Place the treated highland barley straw in a digital constant temperature water bath for 30 minutes, and set the temperature to 40°C; then adjust the temperature of the digital constant temperature water bath to 70°C and bathe for 20 minutes to inactivate the enzyme; take out the highland barley straw, rinse it under tap water until it is neutral, start to drain the water, put it in a culture dish, mark it, and put it in a constant temperature blast drying oven at 80°C to dry; when the highland barley straw reaches a constant weight, take it out, weigh it on a balance and record the data, then crush it through a 60-mesh sieve, weigh it again and record it, and then put it into sealed bags, mark it, and store it.
[0110] The highland barley straw is modified according to the above four methods and steps.
[0111] A cubic closed box was made with a 45cm long steel pipe to simulate the indoor space, and a diluted formaldehyde solution was placed in it to simulate the indoor formaldehyde pollution environment.
[0112] Place the diluted formaldehyde solution in a petri dish, then place the petri dish in the middle of the sealed box for 8 seconds, let it sit for ten minutes to allow the gas to evenly fill the entire box, and then use a formaldehyde detector to test. If the instrument detects formaldehyde concentration of 1.80 mg / m 3 When the gas concentration is floating around, the different highland barley straw adsorbents obtained by the above four methods are spread on the culture dish and put into the box for adsorption. After adsorption for 30 minutes, the concentration is detected by the detector and recorded. Otherwise, the diluted formaldehyde solution is continued to be put into the box to adjust the gas concentration until the concentration is 1.80 mg / m 3 Floating around. Calculate the adsorption of formaldehyde under different adsorbents, the results are as follows Figure 2 to Figure 5 shown.
[0113] from Figure 2 to Figure 5 It can be seen that the order of formaldehyde adsorption by the four methods is: ethyl acetate assisted neutral protease > calcium chloride assisted hemicellulase > citric acid assisted cellulase > alkaline heat treatment. It can be seen that the best modification method for highland barley straw is ethyl acetate assisted neutral protease.
[0114] 3. Analysis of formaldehyde removal rate
[0115] There are many factors that affect the removal rate of formaldehyde. Formaldehyde adsorption experiments were conducted on five factors: modified highland barley straw particle size, addition amount, ambient temperature, adsorption time, and pollutant concentration.
[0116] 1) Effect of different modified highland barley straw particle sizes on formaldehyde adsorption
[0117] Select 18 mesh, 40 mesh, 60 mesh, 80 mesh, and 100 mesh sieves, and stack them in order from small to large mesh, with the largest mesh sieve at the bottom. Take the modified highland barley straw and grind and sieve until there is 1g of powder in each mesh of the highland barley straw, and then stop sieving.
[0118] Take 1g of modified highland barley straw after sieving at each mesh size and 22℃ and formaldehyde concentration of 1.8±0.05mg / m 3 Under the condition of , start adsorption for 30min, record relevant data, calculate removal rate, repeat the above experiment three times, calculate the average value, and then get the best slag particle size. The results are as follows Figure 6 shown.
[0119] Depend on Figure 6 It can be seen that the highland barley straw adsorbent has the best formaldehyde removal effect when the particle size is 60 mesh, and the formaldehyde removal rate reaches 22.8% (F=1936.233, P<0.01). The effect of 18 mesh is the worst, so the subsequent experiments will be carried out using 60 mesh.
[0120] 2) Effect of different amounts of modified highland barley straw on formaldehyde adsorption
[0121] When the particle size of modified highland barley straw was 60 mesh and the formaldehyde concentration was 1.8±0.05 mg / m 3 Under the condition of 3 Then, 1g, 1.5g, 2g, 2.5g, and 3g of modified highland barley straw were added to the sealed box for adsorption for 30 minutes. The relevant data were recorded and the removal rate was calculated. The experiment was repeated three times, the average value was calculated, and the optimal amount of modified highland barley straw was selected. The results are as follows: Figure 7 shown.
[0122] from Figure 7 It can be seen that with the increase in the amount of modified highland barley straw added, the formaldehyde removal rate shows an upward trend. When 3g is added, the adsorption performance is the strongest, and the removal rate is 23.98% (F=209.706, P<0.01).
[0123] 3) Effect of different adsorption temperatures on formaldehyde adsorption
[0124] Based on the experiments 1) and 2), the modified highland barley straw was heated to formaldehyde at a concentration of 1.8 ± 0.05 mg / m at temperatures of 22 °C, 23 °C, 24 °C, 25 °C, and 26 °C. 3 Adsorb for 30 minutes, record relevant data and calculate adsorption amount and removal rate. Repeat the experiment three times, calculate the average value, and select the most suitable temperature. The results are as follows: Figure 8 shown.
[0125] from Figure 8 It can be seen that with the increase in the amount of modified highland barley straw added, the formaldehyde removal rate shows an upward trend. When the temperature is 26°C, the adsorption performance is the strongest, and the removal rate is 22.58% (F=182.414, P<0.01).
[0126] 4) Effect of different pollutant concentrations on formaldehyde adsorption
[0127] On the basis of experiments 1), 2), and 3), the concentration of formaldehyde in the five sealed boxes was adjusted by placing a petri dish containing diluted formaldehyde. When the concentration of formaldehyde in the five sealed boxes was stabilized at 0.8±0.05 mg / m 3 1.2±0.05mg / m 3 1.6±0.05mg / m 3 , 2±0.05mg / m 3 2.4±0.05mg / m 3 5 portions of 3g of modified highland barley straw were weighed into culture dishes of the same size, and the culture dishes were placed in the center of the sealed box, and the box was sealed tightly for adsorption for 30 minutes; the formaldehyde concentration was measured with a formaldehyde detector and the removal rate under different concentration conditions was calculated. The results are as follows: Fig. 9 shown.
[0128] from Fig. 9 It can be seen that the removal effect of modified highland barley straw on formaldehyde is at a concentration of 1.6 mg / m 3 The adsorption effect was the best, and the removal rate of formaldehyde reached 22.03% (F = 62.237, P < 0.01). 3 The worst adsorption effect was 16.96%.
[0129] 5) Effect of different adsorption times on formaldehyde adsorption
[0130] Place a petri dish with diluted formaldehyde in a sealed box until the concentration reaches 1.8 mg / m 3When floating, 3g of modified highland barley straw was placed in a closed box, and the formaldehyde concentration values were recorded at 30min, 60min, 90min, 120min, and 150min, respectively. The adsorption amount in different time periods was calculated, the adsorption kinetic curve was drawn, and the time required for the concentration to reach the national safety standard was recorded. The results are as follows: Fig.10 shown.
[0131] from Fig.10 It can be seen that the removal effect of modified highland barley straw on formaldehyde gradually increased before 90 minutes, and then gradually stabilized with the increase of time. The best removal effect was 24.17% at 150 minutes (F=117.21, P<0.01).
[0132] 4. Characterization analysis and adsorption mechanism analysis
[0133] 1) Elemental analysis
[0134] The modified highland barley straw prepared by the above optimal method, the unmodified highland barley straw and the modified highland barley straw after adsorbing formaldehyde were subjected to elemental analysis, and the results are shown in Table 7.
[0135] Table 7 Elemental analysis
[0136] type N element C element H Element S element N％ C％ H％ S％ Original highland barley straw 347 21898 9268 93 0.463 43.18 6.043 0.3851 Modified highland barley straw 338 22847 9761 8 0.436 43.85 6.215 0.032 Adsorption of highland barley straw 367 22992 9802 7 0.48 44.18 6.245 0.0262
[0137] According to the analysis in Table 7, the original highland barley straw contains a large amount of C and H elements, and the S element has the least content. After treatment with ethyl acetate-assisted neutral protease, the contents of C and H elements increased slightly, and the S and N elements decreased slightly. After adsorption, the C element showed a significant upward trend, the H element increased slightly, and the N and S elements decreased significantly, indicating that the modified highland barley straw adsorbed a large amount of formaldehyde after adsorption.
[0138] 2) Infrared spectroscopy analysis
[0139] Add potassium bromide to the grinding mortar, take 5 mg of the original highland barley straw powder and put it in the grinding mortar, grind it thoroughly with potassium bromide, slowly pour the mixed material into the tablet, press it under the powder tablet press for 1 minute, and when it becomes a transparent tablet, put it in the Fourier infrared spectrometer for infrared scanning and measure its spectrum. Take 5 mg of modified highland barley straw and highland barley straw after adsorption and repeat the experiment according to the above operation, measure its spectrum, and judge the adsorption properties of highland barley straw before and after modification according to the spectrum. The results are as follows: Fig.11 shown.
[0140] from Fig.11 It can be seen that the original highland barley straw is a, the modified highland barley straw is b, and the modified highland barley straw after adsorption is c. -1The stretching vibration peak of -OH appeared nearby. The transmittance of the absorption peak of the modified highland barley straw decreased significantly and the peak shifted slightly to the left, indicating that the number and activity of -OH in highland barley straw were enhanced after treatment with ethyl acetate-assisted neutral protease. -1 There is -CH3 nearby, at 1735.10cm -1 Nearby is the absorption peak of C=O, at 1054.82 cm -1 The telescoping motion of the nearby carbon-containing single chain also plays a role.
[0141] 3) Scanning electron microscopy analysis
[0142] The modified highland barley straw prepared by the above optimal method, the original highland barley straw and the modified highland barley straw after adsorption of formaldehyde were analyzed by scanning electron microscope. The results are as follows: Fig.12 As shown. Fig.12 It can be seen that Figure A is an electron micrograph of the original barley straw, and Figure B is an electron micrograph of the modified barley straw. It can be seen that compared with the original barley straw, the modified barley straw has a larger crushed surface area, which is more conducive to the adsorption of formaldehyde. Figure C is an electron micrograph of the modified barley straw after adsorption, and it can be seen that the barley straw after adsorption is filled.
[0143] 4) Specific surface area and pore size analyzer analysis
[0144] The specific surface area and pore volume of the modified highland barley straw prepared by the above optimal method were measured to obtain the specific surface area parameters of the material, which can intuitively illustrate that the larger pore size of the modified highland barley straw can provide adsorption sites. The results are shown in Table 8.
[0145] Table 8 Specific surface area and pore size analysis
[0146] Test items Modified highland barley straw <![CDATA[Specific surface area (m 2 / g)]]> 1.881 <![CDATA[Pore volume (cm 3 / g)]]> 0.004 Pore size analysis (μm) 3.055
[0147] 5) Adsorption mechanism analysis
[0148] Under constant temperature conditions, the curve of equilibrium adsorption amount changing with the change of ambient gas concentration is the adsorption isotherm, which reflects the adsorption characteristics of solid samples, single molecule uniform adsorption or non-uniform multilayer adsorption. The commonly used Langmuir isotherm is shown in formula (1) and the Freundlich isotherm is shown in formula (2).
[0149] C / Qm+1 / Qmb=C / Q Formula (1);
[0150] K×C n =qFormula (2).
[0151] Taking the logarithm on both sides of the equation, we can transform it into a linear form:
[0152] lgK+nlgC=lgq formula (3).
[0153] Where C is the equilibrium concentration in μg / m 3 ; q is the equilibrium adsorption capacity, the unit is μg / g; Qm is the saturated adsorption capacity, the unit is μg / g; b is the adsorption equilibrium constant, which indicates the magnitude of the adsorption force for the adsorbate binding force; K is the Friedrich constant; n is the adsorption index.
[0154] Analyze and organize the data on initial concentration and adsorption amount obtained from the single factor experiment, and draw the adsorption isotherm Fig.13 As shown, Fig.13 The obtained data were analyzed and collated, and fitted with the Langmuir and Freundlich isotherms to obtain Fig.14 , Fig.15 . And find out the corresponding parameters, as shown in Table 9.
[0155] Table 9 Langmuir and Freundlich model parameters
[0156]
[0157] Analyze the data in Table 9 and obtain the Freundlich isotherm R 2 As high as 0.9582. The degree of fit with the corresponding experimental data is better, and it also proves that the adsorption behavior of modified highland barley straw to formaldehyde is multi-molecular layer, multi-active site adsorption, 1 / n is used as an adsorption intensity index, 1 / n=0.7130<1 proves that the reaction is relatively easy to occur.
[0158] 6) Adsorption kinetics
[0159] The pseudo-first-order kinetic equation is shown in formula (4):
[0160] lg(q e -q t ) = lgq e -k1t / 2.303 formula (4).
[0161] The pseudo-second-order kinetic equation is shown in equation (5):
[0162]
[0163] Where: t represents time, the unit is min; q t Refers to the adsorption amount at time t, in mg / g; q e represents the equilibrium adsorption capacity, in mg / g; k1 represents the first-order adsorption kinetic constant, in min -1 , k2 represents the secondary adsorption kinetic constant, in g·mg-1 ·min -1 .
[0164] Combine the relevant data of equilibrium adsorption amount and adsorption time when the single factor is time, and use it as the horizontal and vertical coordinates to draw the kinetic curve, such as Fig.16 As shown. Fig.16 It can be seen that the adsorption time and adsorption amount are linear, and the longer the time, the greater the adsorption amount; the data in the figure are consistent with the pseudo-first-order kinetic equation and the pseudo-second-order kinetic equation. Fig.17 , 18 And the corresponding parameters are calculated, as shown in Table 10.
[0165] Table 10 Pseudo-first-order and pseudo-second-order kinetic parameters
[0166]
[0167] The fitting results of the kinetic curve show that the fitting degree with the mathematical model of the pseudo-secondary kinetic curve is higher, reaching R 2 =0.9999, which proves that chemical reaction plays a leading role in the adsorption process. The experimental results show that the formaldehyde concentration increased from 2.40 mg / m 3 Reduced to 0.75 mg / m 3 , in national safety standards <0.80mg / m 3 the following.
[0168] 5. Adsorption effect of different adsorbents on formaldehyde
[0169] Place a petri dish filled with diluted formaldehyde solution in a sealed box to simulate the indoor formaldehyde environment. Place the petri dish in the center of the sealed box and leave it there for 15 seconds. Take out the petri dish, seal the sealed box tightly and wait for 10 minutes. Then use a formaldehyde detector to test the formaldehyde concentration in the sealed box. If the formaldehyde concentration is 1.8±0.05mg / m 3 When the concentration reaches 1.8±0.05mg / m3, the concentration of formaldehyde in the box should be adjusted. If the concentration reaches 1.8±0.05mg / m3, the concentration of formaldehyde in the box should be adjusted. 3. Under the same experimental conditions, activated carbon, bamboo charcoal, diatomaceous earth, resin, original highland barley straw and modified highland barley straw were taken and the experiment was repeated according to the above steps. Among them, the particle size of macroporous adsorption resin AB-8 is 18 mesh, the particle size of activated carbon is 60 mesh, the particle size of diatomaceous earth is 325 mesh, the particle size of bamboo charcoal is 60 mesh, the particle size of modified highland barley straw is 60 mesh, and the particle size of original highland barley straw is 60 mesh. Then, the adsorption conditions of 60min, 90min, 120min and 150min were detected in turn according to the above steps, and the relevant removal rates were calculated for comparative analysis. The results are as follows Fig.19 shown.
[0170] At room temperature of 21°C, different materials have different adsorption effects on formaldehyde, and the results are shown in Tables 11 and 12. The modified highland barley straw has a significant advantage in the adsorption performance of formaldehyde. The adsorption performance of the six materials for formaldehyde is from large to small: modified highland barley straw> bamboo charcoal> diatomaceous earth> activated carbon> resin> original highland barley straw. The modified highland barley straw is very significant compared with other materials.
[0171] Table 11 Difference analysis of formaldehyde adsorption performance of different materials
[0172] Sources of variation SS df MS F p Material 3611.919 5 722.3839 4683.543 0.0001 time 30.7103 4 7.6776 49.777 0.0001 Material x Time 3.0848 20 0.1542 10.202 0.0001 error 0.9071 60 0.0151 - - Total variation 3646.621 89 - - -
[0173] Table 12 Multiple comparisons of formaldehyde adsorption performance of different materials
[0174]
[0175]
[0176] 6. Cycle adsorption times
[0177] The adsorbed highland barley straw was soaked in the sun and exposed to high temperature for 2 hours to allow the formaldehyde adsorbed in the modified highland barley straw to fully volatilize; the desorbed highland barley straw residue was used for repeated adsorption for 30 minutes, and the number of adsorptions was recorded to qualitatively analyze the adsorption performance of highland barley straw. The results are as follows: Fig. 20 shown.
[0178] from Fig. 20 It can be seen that the most primitive exposure method was used to desorb and regenerate the modified highland barley straw. The results of the first five repeated experiments showed that the adsorption performance of the modified highland barley straw for formaldehyde had a significant difference F=593.38, P<0.01, and the adsorption effect was relatively stable. From the sixth to the seventh adsorption, the adsorption effect of the highland barley straw began to weaken significantly, but it can be seen that after seven cycles of use, the modified highland barley straw still has a certain adsorption effect.
[0179] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.
[0180] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.
Claims
1. A method for preparing modified highland barley straw, characterized in that: The following steps are involved: After hot steaming, highland barley straw is soaked in an ethyl acetate solution for 21 to 39 minutes, a neutral protease solution is added to increase the content of -OH, CH3 and carbon-containing single chains in the highland barley straw, the highland barley straw is reacted at 50 to 55 degrees Celsius for 28 to 30 minutes, the enzyme is inactivated, the highland barley straw is dried, and the highland barley straw is crushed to obtain the modified highland barley straw; The modified highland barley straw is used for adsorbing formaldehyde; The concentration of the ethyl acetate solution is 0.02 mol / L to 0.18 mol / L; The concentration of the neutral protease is 0.02 mol / L to 0.18 mol / L.
2. The method for preparing modified highland barley straw according to claim 1, characterized in that: The particle size of the modified highland barley straw is 60 meshes to 100 meshes.
3. The method for preparing modified highland barley straw according to claim 1, characterized in that: The mass volume ratio of the highland barley straw to the neutral protease solution is 10kg:50L-55L.
4. The method for preparing modified highland barley straw according to claim 1, characterized in that: The temperature for inactivating the enzyme is 70° C. to 73° C., and the time is 8 min to 10 min.
5. The method for preparing modified highland barley straw according to claim 1, characterized in that: The steaming time is 15 to 20 minutes.
6. Modified highland barley straw prepared by the method for preparing modified highland barley straw according to any one of claims 1 to 5.
7. Use of the modified highland barley straw according to claim 6 in preparing a formaldehyde scavenger.
8. A method for removing formaldehyde, characterized in that: The modified highland barley straw described in claim 6 is placed in a gas containing formaldehyde, and the modified highland barley straw is used to adsorb the formaldehyde to remove the formaldehyde in the gas.
9. The method for removing formaldehyde according to claim 8, characterized in that: The ratio of the amount of highland barley straw used to the amount of formaldehyde adsorbed is 3g:0.42mg-0.45mg.