A method for preparing and using a dual catalytically active iron-based composite

Abstract

The application discloses a preparation method and application of a double-catalytic-activity iron-based composite material, relates to the technical field of modified materials, and has the technical scheme as follows: a preparation method of a double-catalytic-activity iron-based composite material, comprising the following steps: 1) dispersing minerals into anhydrous ethanol, adding soluble ferrous salt and thioacetamide, blending, and performing ultrasonic treatment for 0.5-1 hours; 2) transferring the mixture obtained in the step 1) into a hydrothermal synthesis reaction kettle, performing solvothermal synthesis on the mixture, centrifugally collecting the obtained product after being cooled to room temperature, and dispersively washing the product with anhydrous ethanol for 2-3 times; 3) collecting the washed sample through centrifugation, and then performing vacuum drying to obtain the iron-based composite material loaded with FeS2; and the iron-based composite material can be applied as a compost additive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of modified materials, and more particularly to a preparation method and application of a double-catalytic-activity iron-based composite material. BACKGROUND

[0002] The aerobic composting technology is a terminal treatment method for organic solid waste. Under the action of endogenous microorganisms and related enzymes, organic matter is converted into stable humic substances to prepare value-added products such as organic fertilizer. Traditional composting technology has some defects, such as slow degradation of lignocellulose, low humification degree, nitrogen loss, etc. In actual production process, the adjustment of raw materials and process conditions is relatively limited, and external additives are usually applied to solve the above problems.

[0003] Natural minerals are commonly used inorganic additives in the composting process, most of which exist in the natural environment, and have the characteristics of low cost, environmental friendliness, and large specific surface area. However, when natural minerals are used as additives, the activity is usually low, which increases the amount of addition, resulting in low organic matter content in the final compost product. Therefore, it is of great significance to develop a low-cost and effective material and method to overcome the limitations of natural minerals, expand the application range, and realize the potential value.

[0004] In recent years, some researchers have used Fenton or Fenton-like reactions to generate strong oxidative free radicals, initiate and propagate free radical chain reactions, accelerate the oxidation of lignocellulose and other difficult-to-degrade substances, and promote the generation of humus. The existing patent with publication number CN115043676B and the name of "a method for efficiently degrading lignocellulose by biological simulation Fenton-like reaction" discloses the use of inoculated hydrogen peroxide-producing bacteria to provide H2O2, followed by the addition of ferrous nanomaterials to catalyze the generation of ·OH, to accelerate the degradation of lignocellulose waste. However, due to the complexity of the method and the need for a two-stage composting process, the H2O2 produced in the first composting process is unstable and easily decomposed, which limits the application range. The existing patent with publication number CN114262135B and the name of "a method for strengthening composting and remediation of heavy metal contaminated sediment based on calcium peroxide Fenton" discloses the use of added calcium peroxide and ferroferric oxide nanoparticles to form a Fenton-like reaction to strengthen the humification degree in the co-composting of agricultural waste and sediment. However, calcium peroxide dissolved in water easily forms calcium hydroxide, which increases the pH value and is not conducive to the activity of composting microorganisms. SUMMARY

[0005] In view of the deficiencies of the prior art, the first purpose of the present application is to provide a preparation method of a double-catalytic-activity iron-based composite material, and the second purpose is to provide the application of the iron-based composite material in composting.

[0006] To achieve the first purpose, the application provides a preparation method of a double catalytic activity iron-based composite material, comprising the following steps:

[0007] 1) dispersing the mineral into anhydrous ethanol, adding soluble ferrous salt and thioacetamide, blending and performing ultrasonic treatment for 0.5-1 h;

[0008] 2) transferring the mixture obtained in step 1) to a hydrothermal synthesis reactor, performing solvothermal synthesis on the mixture, centrifuging the obtained product after cooling to room temperature, and washing the product with anhydrous ethanol for 2-3 times;

[0009] 3) collecting the washed sample by centrifugation, and then performing vacuum drying to obtain the iron-based composite material loaded with FeS2.

[0010] By adopting the above technical scheme, FeS2 is synthesized in situ on the surface of the natural mineral by one-pot hydrothermal method, the prepared composite material generates sulfur vacancies, the double catalytic activities of glutathione oxidase and catalase can be realized, and thus the physical and chemical properties or active sites of the mineral surface are changed, and the catalytic activity and microbial affinity of the mineral are increased.

[0011] Further, the mass ratio of the mineral, the soluble ferrous salt and the thioacetamide in step 1) is 2:1:(2-2.5).

[0012] Further, the mesh number of the mineral in step 1) is 500 meshes or more, and the mineral is one or more of palygorskite, halloysite, clinoptilolite or hydrotalcite.

[0013] Further, the mass concentration of the mineral dispersed into the anhydrous ethanol in step 1) is 0.5%-1.0% (w / v).

[0014] Further, the solvothermal synthesis condition in step 2) is heating at 160-220 ℃ for 8-12 h.

[0015] Further, the vacuum drying condition in step 3) is drying at 50-80 ℃ for 10-24 h.

[0016] Further, the purity of the soluble ferrous salt in step 1) is ≥99.0%, and the purity of the thioacetamide is ≥99.0%.

[0017] To achieve the second purpose, the application provides the following technical scheme:

[0018] The application of the above iron-based composite material as a compost additive comprises: fully mixing the iron-based composite material and reduced glutathione with compost raw materials at the beginning of composting, and performing aerobic fermentation to improve the humus degree of the compost.

[0019] Further, the additive amount of the iron-based composite material is 0.5% to 2.5% of the dry weight of the compost raw material, and the mass ratio of the iron-based composite material to reduced glutathione is 1:0.8 to 1:1.2.

[0020] Further, the compost raw material is a mixture of straw and livestock and poultry manure or vegetable waste, and the mixing ratio of the straw and livestock and poultry manure or vegetable waste is 1:3 to 1:4 by wet weight,

[0021] Further, the aerobic fermentation conditions are as follows: the initial carbon-nitrogen ratio is (25-30):1, the initial moisture content is 60% to 65%, the aeration rate is 0.2 to 0.3 L / min / kg dry weight, and the fermentation period is 40 days.

[0022] Further, the temperature control mode of the composting reaction is as follows: 0-5 days are the temperature rising period, the temperature rises from 30℃ to 55℃, and the temperature rises by 5℃ per day; 6-15 days are the thermophilic period, and the temperature is maintained at 55℃; 16-25 days are the temperature decreasing period, and the temperature decreases from 55℃ to 25℃, and the temperature decreases by 3℃ per day; and 25-40 days are the maturation period, and the temperature is maintained at 25℃.

[0023] In summary, the present application has the following advantages:

[0024] First, the present application synthesizes FeS2 in situ on the surface of natural minerals by one-pot hydrothermal method, and the prepared composite material generates sulfur vacancies, realizes the double catalytic activity of glutathione oxidase and catalase, constitutes a self-cascade platform, catalyzes the oxidation of reduced glutathione, and accompanies the generation of H2O2 and ·OH. The physical and chemical properties or active sites of the mineral surface are changed, the catalytic activity and microbial affinity of the mineral are increased, and the humification degree of the compost is improved.

[0025] Second, the method of the present application fully mixes the prepared iron-based composite material and reduced glutathione with the raw material before starting the composting, improves the conductivity value, cellulose degradation and polymerization degree of the compost particles in the composting process, and promotes the humification process of the compost. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the XRD detection diagram of the iron-based composite material FeS2 / Pal prepared in Example 1 of the present application and the original palygorskite Pal;

[0027] Figure 2 is the SEM diagram of the iron-based composite material FeS2 / Pal prepared in Example 1 of the present application and the original palygorskite Pal;

[0028] Figure 3 is the EPR result diagram of the iron-based composite material FeS2 / Pal prepared in Example 1 of the present application;

[0029] Figure 4is a plot of the change in conductivity during the aerobic composting process of Example 1 of the present application;

[0030] Figure 5 is a plot of the change in cellulose content during the aerobic composting process of Example 1 of the present application;

[0031] Figure 6 is a plot of the change in degree of polymerization during the aerobic composting process of Example 1 of the present application. DETAILED DESCRIPTION

[0032] The present application is further described in connection with the following examples. It will be understood that these examples are intended to illustrate the present application and are not intended to limit the scope of the present application. Furthermore, it will be understood that various modifications and changes can be made to the present application by those skilled in the art upon reading the contents of the present application. Such equivalent forms are intended to be within the scope of the appended claims.

[0033] The reagents used in the examples are commercially available unless otherwise specified.

[0034] Example 1

[0035] A method for preparing a dual catalytically active iron-based composite material, comprising the following steps:

[0036] 1) 0.30 g of palygorskite powder was weighed into a beaker, 60 mL of anhydrous ethanol was added for dispersion, then 0.15 g of FeCl2·4H2O and 0.337 g of thioacetamide were weighed separately, stirred uniformly, and ultrasonically treated for 1 h;

[0037] 2) The mixture in the beaker was transferred to a hydrothermal synthesis reaction kettle, sealed, and placed in a muffle furnace, and was heated by solvothermal method at 180℃ for 10 h. After cooling to room temperature, it was taken out, the mixture was centrifuged at 8000 rpm for 10 min, and after removing the supernatant, it was dispersed again with anhydrous ethanol and washed repeatedly for 3 times;

[0038] 3) The washed sample was centrifuged to collect the precipitate, and the collected black product was vacuum dried at 60℃ for 12 h, thereby obtaining a composite material loaded with FeS2, denoted as FeS2 / Pal.

[0039] Application of an iron-based composite material as a compost additive:

[0040] The iron-based composite material prepared according to the above Example 1 was applied as an additive to the aerobic composting process of cow dung and straw, the straw used was agricultural corn straw, the total solid content TS = 94.03%, and the organic matter content OM = 91.52%; the cow dung used was taken from a cattle farm, the total solid content TS = 16.61%, and the organic matter content OM = 62.96%; the straw and cow dung were mixed in a wet weight ratio of 1:4, and 2% of GSH and 2% of FeS2 / Pal were added by dry weight of the raw materials, denoted as FPG; raw palygorskite was used as an additive, 2% of GSH and 2% of Pal were added by dry weight of the raw materials, denoted as PG; the cow dung and straw without external additive were used as the raw material for composting as the control group, denoted as CK; the initial moisture content of the compost was adjusted to about 65%, the C / N was about 30, and the ventilation rate was 0.2 L / min / kg TS; the compost reactor was placed in a temperature control device to simulate the traditional composting temperature rising mode: 0-5 days for temperature rising period, the temperature rose from 30°C to 55°C, 5°C per day; 6-15 days for thermophilic period, maintaining 55°C; 16-25 days for temperature decreasing period, the temperature decreased from 55°C to 25°C, 3°C per day; 25-40 days for maturation period, maintaining 25°C.

[0041] Example 2

[0042] A preparation method of a dual catalytic activity iron-based composite material, comprising the following steps:

[0043] 1) 0.30 g of palygorskite powder was weighed into a beaker, 60 mL of anhydrous ethanol was added for dispersion, then 0.30 g of FeSO4·7H2O and 0.337 g of thioacetamide were weighed respectively, stirred uniformly, and ultrasonically treated for 1 h;

[0044] 2) The mixture in the beaker was transferred to a hydrothermal synthesis reaction kettle, sealed, and placed in a muffle furnace for solvothermal heating at 180°C for 10 h, then the reaction kettle was taken out after cooling to room temperature, the mixture was centrifuged at 8000 rpm for 10 min, and after removing the supernatant, the mixture was dispersed again with anhydrous ethanol and washed repeatedly for 3 times;

[0045] 3) The washed sample was centrifuged to collect the precipitate, and the collected black product was vacuum dried at 60°C for 12 h to obtain a composite material loaded with FeS2, denoted as FeS2 / Pal.

[0046] Application of an iron-based composite material as a compost additive:

[0047] The iron-based composite material prepared according to the above Example 2 was applied as an additive to the aerobic composting process of straw and kitchen waste. The straw and kitchen waste were mixed in a wet weight ratio of 1:3, and 2% GSH and 2% FeS2 / Pal of the dry weight of the raw materials were added. Raw materials were composted with original palygorskite as an additive, 2% GSH and 2% Pal of the dry weight of the raw materials were added. The kitchen waste and straw without the addition of exogenous additives were used as the control group. The initial moisture content of the compost was adjusted to about 65%, the C / N was about 30, the ventilation rate was 0.25 L / min / kg TS, and the compost reactor was placed in a temperature control device to simulate the traditional composting temperature rising mode: 0-5 days for the temperature rising period, the temperature rose from 30°C to 55°C, and the temperature rose by 5°C every day; 6-15 days for the thermophilic period, maintaining 55°C; 16-25 days for the temperature decreasing period, the temperature decreased from 55°C to 25°C, and the temperature decreased by 3°C every day; 25-40 days for the maturation period, maintaining 25°C.

[0048] Example 3

[0049] A method for preparing a dual catalytic activity iron-based composite material, comprising the following steps:

[0050] 1) 0.30 g of halloysite (Hal) powder was weighed into a beaker, 60 mL of anhydrous ethanol was added for dispersion, then 0.15 g of FeCl2·4H2O and 0.375 g of thioacetamide were weighed respectively, stirred uniformly, and ultrasonically treated for 1 h;

[0051] 2) The mixture in the beaker was transferred to a hydrothermal synthesis reaction kettle, sealed, and placed in a muffle furnace for solvothermal heating at 200°C for 9 h. After cooling to room temperature, the reaction kettle was taken out, the mixture was centrifuged at 8000 rpm for 10 min, and after removing the supernatant, the mixture was dispersed again with anhydrous ethanol and washed repeatedly for 3 times;

[0052] 3) The washed sample was centrifuged to collect the precipitate, and the black product collected was vacuum dried at 70°C for 12 h to obtain a composite material loaded with FeS2, denoted as FeS2 / Hal.

[0053] Application of an iron-based composite material as a compost additive:

[0054] The iron-based composite material prepared according to the above Example 3 was applied as an additive to the aerobic composting process of cow dung and straw, the straw and cow dung were mixed according to a wet weight ratio of 1:4, and 1.5% of GSH and 1.5% of FeS2 / Hal of the dry weight of the raw materials were added; the original palygorskite was used as an additive, 1.5% of GSH and 1.5% of Hal of the dry weight of the raw materials were added; the cow dung and straw without adding exogenous additives were used as the raw material for composting as the control group, the initial moisture content of the compost was adjusted to about 65%, the C / N was about 30, the ventilation rate was 0.2 L / min / kg TS, the compost reactor was placed in a temperature control device, and the traditional composting temperature rising mode was simulated: 0-5 days for temperature rising period, the temperature rose from 30°C to 55°C, 5°C per day; 6-15 days for thermophilic period, maintaining 55°C; 16-25 days for temperature decreasing period, the temperature decreased from 55°C to 25°C, 3°C per day; 25-40 days for maturation period, maintaining 25°C.

[0055] Performance detection test

[0056] The FeS2 / Pal composite material prepared in Example 1 and the unmodified original palygorskite control were subjected to XRD, SEM and EPR analysis, and the analysis results are shown in Figures 1 to 3 .

[0057] The X-ray diffractometer (D8 Advance, Bruker, Germany) was used to characterize the phase composition of the original palygorskite and the FeS2 / Pal composite material, and the results are shown in Figure 1 . The hydrothermal treatment at 180°C had no significant effect on the mineral composition, and active FeS2 was generated in situ on the surface of the palygorskite. The broadened peaks at 27.5°, 33.0°, 36.9°, 40.6°, 47.5° and 56.3° can be judged to correspond to the (1 1 1), (2 0 0), (2 1 0), (2 1 1), (2 2 0) and (3 1 1) planes of FeS2, respectively. The results show that the supported iron-based composite material is successfully prepared.

[0058] The surface morphology of the original palygorskite Pal and the composite material FeS2 / Pal is shown in Figure 2 , wherein Figure 2 a, 2b and 2c are SEM results of Pal at 2 μm, 1 μm and 200 nm scales, respectively, Figure 2 d, 2e and 2f are SEM results of FeS2 / Pal at the same magnification, it can be found that compared with the relatively smooth surface of Pal, more small particle materials appear on the surface of FeS2 / Pal, indicating that FeS2 is successfully synthesized on the surface of the mineral.

[0059] The free radical signal was detected by electron paramagnetic resonance (EPR) spectrometer (EMX nano, Bruker, Germany) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as electron capture agent under the following conditions: 1 mM H2O2, 10 mg FeS2 / Pal. Figure 3 As shown, the ·OH signal was detected within 5 to 10 min, confirming that FeS2 / Pal had catalase activity and catalyzed the production of ·OH.

[0060] The iron-based composite material of Example 1 was used as a compost additive. Samples were taken on days 0, 3, 15, 25, and 40 to measure compost indicators. Water-soluble indicators such as electrical conductivity (EC) were determined using the compost extract. Lignocellulose was digested by two-step hydrolysis with sulfuric acid and then analyzed by high-performance liquid chromatography. Humic matter was extracted with 0.1 M NaP2O7·10H2O and NaOH, and fulvic acid (FA) and humic acid (HA) were separated using 3 M H2SO4 and 0.05 M NaHCO3, respectively. The organic carbon content (C) of HA and FA was determined using a total organic carbon analyzer (multi N / C 3100, Analytik Jena). HA and C FA The degree of polymerization is calculated as DP = C HA / C FA .

[0061] The electrical conductivity value (EC) reflects the electrical conductivity of the compost system, such as Figure 4 As shown in the figure, the EC values ​​of the three treatment groups increased by 37.37%, 23.84%, and 51.58%, respectively. This indicates that the addition of the iron-based composite material improves the conductivity of the system, which helps accelerate the transfer of electrons between compost material particles, thereby improving the efficiency of the biological redox process and promoting the utilization of O2.

[0062] Changes in cellulose Figure 5 As shown, the majority of cellulose degradation occurred during the first 15 days of the thermophilic phase. After 15 days, degradation slowed and differences in degradation efficiency began to emerge between the groups. Addition of palygorskite and GSH led to sustained cellulose degradation, which was further enhanced by the addition of FeS2 / Pal and GSH. On day 40, the cellulose contents in CK, PG, and FPG were 12.90%, 11.43%, and 9.98%, respectively, with total degradation rates of 40.66%, 47.17%, and 52.54%, respectively. The addition of the iron-based composite material enhanced the degradation of macromolecular cellulose.

[0063] The changes in the degree of polymerization of compost particles were evaluated by calculating the ratio of humic acid to fulvic acid. Figure 6The degree of polymerization of CK decreased in the first 25 days, and then increased in the last 25-40 days. The degree of polymerization of PG showed a slow increasing trend during the whole composting process, and the degree of polymerization of FPG showed a more obvious increasing trend. At the end of composting, the degree of polymerization of CK, PG and FPG were 0.79, 0.99 and 1.18, respectively, indicating that the composting system with FeS2 / Pal added contained more macromolecular polymers, thereby improving the stability of humus.

[0064] The embodiments are only used to explain the present application, and are not used to limit the present application. Those skilled in the art can make modifications to the embodiments without creative contribution, as long as the modifications are within the scope of the present application.

Claims

1. An application of an iron-based composite material, characterized in that: The iron-based composite material is used as a compost additive. The iron-based composite material and reduced glutathione are fully mixed with compost raw materials at the start of composting to perform aerobic fermentation. The mass ratio of the iron-based composite material to reduced glutathione is 1:0.8 to 1:1.

2. By fully mixing the prepared iron-based composite material and reduced glutathione with the raw materials before composting is started, the conductivity value, cellulose degradation and polymerization degree of compost particles during the composting process are improved. The preparation method of the iron-based composite material comprises the following steps: 1) Disperse the mineral in anhydrous ethanol, add soluble ferrous salt and thioacetamide, blend and ultrasonicate for 0.5-1h; 2) transferring the mixture obtained in step 1) to a hydrothermal synthesis reactor, performing solvothermal synthesis on the mixture, heating the mixture at 160-220° C. for 8-12 hours, cooling the obtained product to room temperature, collecting the product by centrifugation, and dispersing and washing the product with anhydrous ethanol 2-3 times; 3) The washed sample is collected by centrifugation and then vacuum dried to obtain an FeS2-loaded iron-based composite material; The prepared iron-based composite material has sulfur vacancies, which can realize the dual catalytic activity of glutathione oxidase and catalase, forming a self-cascade platform to catalyze the oxidation of reduced glutathione accompanied by the generation of H2O2 and ·OH.

2. The use of the iron-based composite material according to claim 1, characterized in that: The mass ratio of the mineral, soluble ferrous salt and thioacetamide described in step 1) is 2:1:(2-2.5).

3. The use of the iron-based composite material according to claim 1, characterized in that: The mineral mesh number in step 1) is 500 mesh or more, and the mineral is one or more of palygorskite, halloysite, clinoptilolite or hydrotalcite.

4. The use of the iron-based composite material according to claim 1, characterized in that: In step 3), the vacuum drying condition is 50-80° C. for 10-24 hours.

5. The use of the iron-based composite material according to claim 1, characterized in that: The purity of the soluble ferrous salt in step 1) is ≥99.0%, and the purity of thioacetamide is ≥99.0%.

6. The use of the iron-based composite material according to claim 1, characterized in that: The added amount of the iron-based composite material is 0.5% to 2.5% of the dry weight of the compost raw material.

7. The use of the iron-based composite material according to claim 1, characterized in that: Aerobic fermentation conditions are as follows: initial carbon-nitrogen ratio of (25-30):1, initial water content of 60%-65%, aeration rate of 0.2-0.3 L / min / kg dry weight, and fermentation period of 40 days.

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