A composite ceramsite, its preparation method and application

Abstract

The present invention provides a composite ceramsite, a preparation method thereof and an application thereof. The preparation method of the composite ceramsite is as follows: granulation is carried out after doping CoFe-LDH powder into a ceramsite matrix containing fly ash, and then calcination is carried out to obtain the composite ceramsite. The present invention uses CoFe-LDH powder and a ceramsite matrix as raw materials together. On the one hand, the metal elements contained in the fly ash in the ceramsite matrix and the CoFe-LDO powder formed after calcination of the CoFe-LDH powder respectively have a catalytic effect on DBDP. On the other hand, the ceramsite matrix serves as a carrier for the CoFe-LDH powder. After calcination, the synergistic effect of the two can efficiently activate the DBDP system, further improve the removal rate of diuron in the DBDP system, and at the same time, the discharge time of the DBDP system can be shortened, the energy consumption can be reduced, and the energy utilization rate can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide wastewater treatment, and particularly relates to a composite ceramsite, a preparation method thereof, and an application thereof. Background Art

[0002] Diuron is a broad-spectrum and systemic herbicide that weeds by inhibiting ATP synthesis and interfering with plant photosynthesis. As an energy metabolism inhibitor drug, diuron can also interfere with the human endocrine system when it comes into contact with the human body, and has hazards such as carcinogenicity and mutagenicity. Plasma is a partially or completely ionized gas, macroscopically neutral, and an aggregate composed of electrons, free radicals, ions, and neutral particles. Dielectric barrier discharge plasma (DBDP) generates plasma by means of dielectric barrier discharge. In dielectric barrier discharge, a dielectric (such as glass, quartz, ceramics, mica, and alumina) is used to block the discharge gap of the electrode, which not only prevents the generation of electric sparks but also reduces the electrode corrosion problem and makes the discharge uniform throughout the electrode. In the DBDP system, high-energy electrons can collide with background molecules such as N2, H2O, or O2 to generate secondary electrons, photons, ions, oxidants ( 1 O2, O3, and H2O2) and free radicals (·OH, ·O2 - ) and other active species. In addition, when the background is water, plasma will generate ultraviolet light due to the collision of electrons and molecules. Making full use of the active substances in the system can effectively oxidize and degrade organic pollutants in the water body. At present, the single DBDP system can effectively degrade diuron. However, it takes 15 minutes of discharge for the removal rate of diuron to reach more than 95%, and the removal rate is 0.2495 min –1 . Therefore, the existing technology needs to be further developed. By adding a catalyst to the system, the degradation performance of the system for pollutants can be effectively improved. The metal elements (Co and Fe) contained in the composite ceramsite can effectively catalyze active species such as H2O2 through valence cycling, promote the transformation of active species, release the oxidation potential of DBDP, and enable a variety of active substances to synergistically degrade organic pollutants and improve the overall energy utilization rate of the system. The synchronous calcination of the catalyst and the ceramsite increases the stability of the composite ceramsite, reduces the dissolution of metal ions, and reduces the environmental pollution risk. Summary of the Invention

[0003] In view of various deficiencies of the prior art, to solve the above problems, a composite ceramsite, a preparation method thereof, and an application thereof are now proposed, and the following technical solutions are provided:

[0004] A preparation method of a composite ceramsite, which comprises doping CoFe-LDH powder into a ceramsite matrix containing fly ash, granulating, and calcining to obtain the composite ceramsite.

[0005] Further, by mass parts, the ceramsite matrix is 85 - 95 parts, and the CoFe-LDH powder is 5 - 15 parts.

[0006] Further, the ceramsite matrix further includes clay, and the mass ratio of the clay to the fly ash is 1:3 - 5.

[0007] Further, during the granulation process, a sodium silicate solution is sprayed onto the ceramsite matrix doped with CoFe-LDH powder to form spherical particles with a diameter of 3 - 8 mm.

[0008] Further, after the spherical particles roll for 0.5 - 1 h, they are dried at 100 - 110 °C for 10 - 12 h and then calcined.

[0009] Further, the calcination temperature is 450 - 550 °C, the heating rate during calcination is 8 - 12 °C·min -1 , and the calcination time is 2 - 4 h.

[0010] Further, the preparation process of the CoFe-LDH powder includes: mixing Fe(NO3)3·9H2O, Co(NO3)2·6H2O and urea and dissolving them in deionized water, carrying out a pressurized reaction at 110 - 130 °C for 15 - 20 h, then alternately rinsing with deionized water and absolute ethanol, and drying to obtain the CoFe-LDH powder.

[0011] Further, the mass usage ratio of Fe(NO3)3·9H2O, Co(NO3)2·6H2O and urea is 2:5:3.

[0012] In addition, the present invention also provides the composite ceramsite prepared by the above method.

[0013] The present invention also provides the application of the above composite ceramsite. The composite ceramsite is used as a catalyst in the process of removing diuron in the DBDP system.

[0014] Beneficial effects:

[0015] 1. The present invention uses CoFe-LDH powder and ceramsite matrix as raw materials. On the one hand, the metal elements contained in the fly ash in the ceramsite matrix and the CoFe-LDH powder respectively have a catalytic effect on DBDP. On the other hand, the ceramsite matrix serves as the carrier of the CoFe-LDH powder. After calcination, the two act synergistically to efficiently activate the DBDP system, further improving the removal rate of diuron in the DBDP system. At the same time, the discharge time of the DBDP system can be shortened, the energy consumption can be reduced, and the energy utilization rate can be improved.

[0016] 2. During the calcination process of the present invention, the CoFe-LDH powder turns into CoFe-LDO, while generating water and carbon dioxide, which makes holes appear on the surface of the composite ceramsite, improving the catalytic effect on DBDP. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the performance graph of the removal of diuron by activated DBDP in Example 1, Comparative Example 1, and without adding a catalyst;

[0018] Figure 2 It is the rate graph of the removal of diuron by activated DBDP in Example 1, Comparative Example 1, and without adding a catalyst;

[0019] Figure 3 It is the graph of the change of the removal rate of diuron with time under different dosages of the composite ceramsite in Example 1.

[0020] Figure 4 It is the rate graph of the removal of diuron under different dosages of the composite ceramsite in Example 1.

[0021] Figure 5 It is the graph of the influence of the reuse of the composite ceramsite in Example 1 on the removal of diuron in the DBDP system;

[0022] Figure 6 It is the XRD graph of fly ash, CoFe-LDO, and composite ceramsite;

[0023] Figure 7 It is the FTIR characterization graph of fly ash, CoFe-LDO, and composite ceramsite;

[0024] Figure 8 It is the schematic diagram of the coaxial DBDP reaction device;

[0025] Figure 9 It is the graph of the change of the removal rate of diuron with time under different ratios of clay and fly ash;

[0026] Figure 10 It is the rate graph of the removal of diuron under different ratios of clay and fly ash;

[0027] Figure 11 It is the graph of the change of the removal rate of diuron with time under different ratios of ceramsite matrix and CoFe-LDH;

[0028] Figure 12 It is the rate graph of the removal of diuron under different ratios of ceramsite matrix and CoFe-LDH.

[0029] Among them, the above-mentioned drawings include the following reference numerals:

[0030] 1. DBDP generating device; 2. Reactor. DETAILED DESCRIPTION OF THE INVENTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making any creative work should all fall within the scope of protection of this application.

[0032] According to an embodiment of the present invention, a method for preparing composite ceramsite is provided, wherein a mixture of clay and fly ash is used as a ceramsite matrix, CoFe-LDH powder is doped into the ceramsite matrix, and then granulation is performed, and calcination is performed to obtain composite ceramsite. After the CoFe-LDH powder and the ceramsite matrix are mixed and calcined simultaneously, the obtained composite ceramsite can efficiently activate the DBDP system, further improve the removal rate of diuron by the DBDP system, and at the same time, shorten the discharge time of the DBDP system, reduce energy consumption, and improve energy utilization. CoFe-LDH powder is a CoFe layered double metal hydroxide, and the CoFe-LDH powder becomes CoFe-LDO after calcination, and CoFe-LDO is a CoFe layered bimetallic oxide.

[0033] Example 1 Preparation method of composite ceramsite

[0034] (1) Preparation of CoFe-LDH: 2 parts of Fe(NO3)3·9H2O, 5 parts of Co(NO3)2·6H2O and 3 parts of urea were mixed and dissolved in 60 parts of deionized water, stirred thoroughly and placed in a polytetrafluoroethylene liner and transferred to a high-pressure reactor. The reactor was placed in an oven and the temperature was adjusted to 120°C and maintained for 18 hours. After cooling to room temperature, the powder material was taken out and rinsed alternately with deionized water and anhydrous ethanol for 10 times, and finally placed in a vacuum oven at 60°C for drying to obtain orange CoFe-LDH powder for standby use.

[0035] (2) Preparation of composite ceramsite by doping CoFe-LDH with fly ash: 18.4 parts of clay and 73.6 parts of fly ash were fully mixed as the ceramsite matrix, 8 parts of LDH powder were doped into the evenly mixed ceramsite matrix and fully mixed, and then the mixture was transferred to a granulator, and 30 parts of sodium silicate solution were sprayed in batches until the powder was rolled into spherical particles with a diameter of 5 mm. After being formed, it was rolled for 0.5 hours until the spherical structure was solid and then taken out to obtain spherical particles. The spherical particles were transferred to a forced air drying oven and dried at 105°C for 12 hours. Finally, the fully dried spherical particles were transferred to a porcelain boat and placed in a tubular furnace. The ceramsite matrix and CoFe-LDH were calcined simultaneously at 10°C·min –1 The temperature is raised to 460°C at a heating rate of , and calcined for 2 hours. After cooling, the ceramsite is taken out to obtain composite ceramsite.

[0036] Preparation Method of Composite Ceramsite in Example 2

[0037] (1) Preparation of CoFe-LDH: Dissolve 2 parts of Fe(NO3)3·9H2O, 5 parts of Co(NO3)2·6H2O and 3 parts of urea in 60 parts of deionized water. After stirring well, transfer it into a polytetrafluoroethylene inner liner and then transfer it into a high-pressure reaction kettle. Place the reaction kettle in an oven, adjust the temperature to 110 °C, and keep it for 20 h. After cooling to room temperature, take out the powder material, rinse it alternately with deionized water and absolute ethanol, and finally dry it in a vacuum oven at 60 °C to obtain orange CoFe-LDH powder for use.

[0038] (2) Preparation of composite ceramsite by doping CoFe-LDH with fly ash: Mix 21.25 parts of clay and 63.75 parts of fly ash as the ceramsite matrix. Dope 15 parts of LDH powder into the uniformly mixed ceramsite matrix and mix well. Then transfer the mixture to a granulator, and spray 25 parts of sodium silicate solution batch by batch until the powder rolls into spherical particles with a diameter of 5 mm. After forming, roll for another 0.8 h until the spherical structure is firm, and then take it out to obtain spherical particles. Transfer the spherical particles to a blast drying oven and dry them at 100 °C for 10 h. Finally, transfer the spherical particles to a porcelain boat, place it in a tube furnace, and calcine the ceramsite matrix and CoFe-LDH synchronously. Heat it up to 450 °C at a heating rate of 8 °C·min –1 and keep it for 4 h. After cooling, take out the ceramsite to obtain the composite ceramsite.

[0039] Preparation Method of Composite Ceramsite in Example 3

[0040] (1) Preparation of CoFe-LDH: Dissolve 2 parts of Fe(NO3)3·9H2O, 5 parts of Co(NO3)2·6H2O and 3 parts of urea in 60 parts of deionized water. After stirring well, transfer it into a polytetrafluoroethylene inner liner and then transfer it into a high-pressure reaction kettle. Place the reaction kettle in an oven, adjust the temperature to 130 °C, and keep it for 15 h. After cooling to room temperature, take out the powder material, rinse it alternately with deionized water and absolute ethanol, and finally dry it in a vacuum oven at 60 °C to obtain orange CoFe-LDH powder for use.

[0041] (2) Preparation of composite ceramsite by doping CoFe-LDH and fly ash: 15.83 parts of clay and 79.17 parts of fly ash were fully mixed as the ceramsite matrix. 5 parts of LDH powder were doped into the well-mixed ceramsite matrix and fully mixed. Then the mixture was transferred to a granulator, and sodium silicate solution was sprayed batchwise until the powder rolled into spherical particles with a diameter of 5 mm. After forming, it was rolled for 1 h until the spherical structure was firm and then taken out to obtain spherical particles. The spherical particles were transferred to a forced-air drying oven and dried at 110 °C for 11 h. Finally, the spherical particles were transferred to a porcelain boat and placed in a tubular furnace. The ceramsite matrix and CoFe-LDH were calcined synchronously, and the temperature was raised to 550 °C at a heating rate of 12 °C·min –1 and calcined for 3 h. After cooling, the ceramsite was taken out to obtain the composite ceramsite.

[0042] Comparative Example 1

[0043] Compared with Example 1, CoFe-LDH was not added, and other steps were exactly the same.

[0044] Comparative Example 2

[0045] Compared with Example 1, the ceramsite matrix was 80 parts and the CoFe-LDH powder was 20 parts.

[0046] The composite ceramsites obtained in Examples 1-3 and Comparative Examples 1-2 were respectively tested for the removal of diuron by activated DBDP.

[0047] Take 200 mL of 1 mg·L –1 diuron solution and place it in a dielectric barrier discharge plasma (DBDP) reactor. The reaction device is as Figure 8 shown. And put 20 g of the composite ceramsite to be tested into the solution in reactor 2. The DBDP generating device 1 generates active species such as hydrogen peroxide, ozone and free radicals. Start the water pump and air pump until the solution flows through the whole reaction system. Then adjust the voltage to 16 kV to start the catalytic degradation reaction, and sample at specific time intervals. Pass through a 0.22 μm water-based filter membrane and store it in an ice bath at 0 °C for testing.

[0048] The concentration of diuron was detected by high performance liquid chromatography. The mobile phase was water / acetonitrile (40 / 60, V / V), the flow rate was 0.1 mL / min, and the detection wavelength was 214 nm. The standard curve was obtained, and the removal rate of diuron was calculated according to the measured peak area.

[0049] Table 1 Removal rates of diuron by activated DBDP of the composite ceramsites obtained in Examples 1-3 and Comparative Examples 1-2

[0050] Removal rate Example 1 <![CDATA[0.4868min –1 > Example 2 <![CDATA[0.4114min –1 > Example 3 <![CDATA[0.4062min –1 > Comparative Example 1 <![CDATA[0.2999min -1 > Comparative Example 2 <![CDATA[0.3024min -1 >

[0051] The tests are shown in Table 1. The removal rates of diuron in Examples 1-3 are significantly higher than those in Comparative Examples 1-2, indicating that using CoFe-LDH powder and ceramsite matrix as raw materials simultaneously and through calcination, the synergistic effect of the two can efficiently activate the DBDP system and further improve the removal rate of diuron by the DBDP system. According to Figure 1 and Figure 2 It can be found that the single DBDP system can effectively degrade diuron. However, it takes 15 minutes of discharging to achieve a removal rate of more than 95% for diuron, and the removal rate is 0.2495 min –1 . When the ceramsite matrix is added, that is, in Comparative Example 1, the removal rate is increased to 0.2999 min –1 , indicating that the metal elements in fly ash waste residue have a catalytic effect on DBDP. However, the improvement effect of degradation is not significant. Compared with the ceramsite matrix, the composite ceramsite has higher catalytic efficiency for DBDP, increasing the removal rate of diuron by the system to 0.4868 min –1 , and a removal rate higher than 95% is obtained at 10 minutes, which can shorten the discharging time of the system, reduce energy consumption, improve energy utilization rate, and meet the low-carbon application of DBDP. Therefore, the experimental results show that compared with pure fly ash ceramsite, the composite ceramsite can efficiently activate DBDP and can significantly improve the removal rate of diuron and reduce energy consumption.

[0052] Then, taking the composite ceramsite obtained in Example 1 as an example, the relationship between the dosage of the composite ceramsite and the removal rate of diuron by the DBDP system was explored.

[0053] The dosages of the composite ceramsite are 0 g·L -1 , 50 g·L -1 , 100 g·L -1 , 150 g·L -1 , 200 g·L -1 , respectively. The influence of its dosage on the removal of diuron by the DBDP system is shown in Figure 3 and Figure 4 . As the dosage of the composite ceramsite increases, the removal rate of diuron gradually increases, from 0.2495 min –1 to 0.4868 min –1 (the catalyst dosage increases from 0 g·L -1 to 100 g·L -1 ). When the catalyst dosage continues to increase (>150 g·L -1 ), the improvement of the removal rate and removal efficiency of diuron is not obvious, which may be due to the accumulation of excessive ceramsite affecting the distribution of air flow and water flow, and excessive filling amount cannot be effectively utilized.

[0054] The composite ceramsite obtained in Example 1 was subjected to a stability test. After being reused seven times, relevant tests were carried out, and the test results are as follows Figure 5 shown. After being reused seven times, the removal rate of diuron by the system remained above 98%. The dissolution concentration of metal ions first increased and then decreased, and finally gradually decreased steadily after the 7th use. During the whole process of using the catalyst, the concentrations of Co and Al ions did not exceed 0.35 mg / L -1 , and the concentration of Fe ions was lower than 0.1 mg / L -1 , meeting the limit values of the environmental quality standards for surface water (GB3838-2002) (Fe 0.3 mg / L -1 , Co 1.0 mg / L -1 ). The experiment shows that the prepared catalyst has good stability and reusability.

[0055] XRD tests and infrared tests were respectively carried out on the composite ceramsite of Example 1, fly ash, and CoFe-LDO. The test results are as follows Figure 6 and Figure 7 shown. From Figure 6 , it can be seen that on the surface of the composite ceramsite, there are mainly strong diffraction peaks of calcium silicophosphate (14.98°), which may be formed after the fusion and sintering of sodium silicate solution and clay. The strong diffraction peaks of the fly ash components SiO2 (26.56°) and the diffraction peak of Al3O2 (35.82°) also appear on the surface of the composite ceramsite. However, due to the low doping amount of CoFe-LDO and the lower surface content, the characteristic diffraction peaks of its main components are covered up. Figure 7 shows the infrared spectrum. From the figure, it can be seen that the characteristic peak of the metal-oxygen bond M—O appears in the composite ceramsite, indicating that CoFe-LDO is successfully doped in the ceramsite matrix.

[0056] The composite ceramsite is spherical and is easy to separate and recycle. In addition, the use of fly ash has a low cost and can efficiently activate DBDP at the same time.

[0057] In addition, the influence of the mass ratio between clay and fly ash on the removal rate of diuron was explored. Experiments were respectively set up without adding clay and fly ash, only adding clay, clay / fly ash = 4 / 1, clay / fly ash = 3 / 2, clay / fly ash = 2 / 3, and clay / fly ash = 1 / 5 for testing. The ceramsite matrix prepared from different mass ratios of clay and fly ash was used as a catalyst to test the removal rate of diuron. The test results are as follows Figures 9 - 10 and Table 2 below.

[0058] Table 2 Influence of the ratio between clay and fly ash on the removal rate of diuron

[0059]

[0060] Secondly, the effect of the mass ratio between the ceramsite matrix and CoFe-LDH on the removal rate of diuron was investigated. Experiments were set up with 96 parts of the ceramsite matrix and 4 parts of CoFe-LDH, 94 parts of the ceramsite matrix and 6 parts of CoFe-LDH, 94 parts of the ceramsite matrix and 6 parts of CoFe-LDH, 92 parts of the ceramsite matrix and 8 parts of CoFe-LDH, and 90 parts of the ceramsite matrix and 10 parts of CoFe-LDH for testing. The preparation method of Example 1 was used, with the difference being the mass ratio between the ceramsite matrix and CoFe-LDH. The test results are as Figures 11 - 12 shown in Table 3 below.

[0061] Table 3 Effect of the ratio between the ceramsite matrix and CoFe-LDH on the removal rate of diuron

[0062]

[0063] From the study of the mass ratio between the ceramsite matrix and CoFe-LDH above, it can be seen that the mass ratio between the ceramsite matrix and CoFe-LDH has a great influence on the final removal rate of diuron. Through multiple experiments, it can be seen that when there are 92 parts of the ceramsite matrix and 8 parts of CoFe-LDH, the removal rate of diuron reaches 0.4868 min –1 .

[0064] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of composite ceramsite, characterized in that, After doping CoFe-LDH powder into the ceramsite matrix containing fly ash, granulation is carried out, and then calcination is performed to obtain composite ceramsite; By mass, the ceramsite matrix is 85-95 parts, and the CoFe-LDH powder is 5-15 parts; The ceramsite matrix further includes clay, and the mass ratio of the clay to the fly ash is 1:3-5; The calcination temperature is 450 - 550 °C, and the heating rate during calcination is 8 - 12 °C·min –1 , and the calcination time is 2 - 4 h.

2. The preparation method of the composite ceramsite according to claim 1, characterized in that During the granulation process, sodium silicate solution is sprayed onto the ceramsite matrix doped with CoFe-LDH powder to form spherical particles with a diameter of 3-8 mm.

3. The preparation method of the composite ceramsite according to claim 2, wherein After the spherical particles roll for 0.5-1 h, they are dried at 100-110 °C for 10-12 h and then calcined.

4. The preparation method of the composite ceramsite according to claim 1, characterized in that, The preparation process of the CoFe-LDH powder includes: mixing Fe(NO3)3‧9H2O, Co(NO3)2‧6H2O and urea and dissolving them in deionized water, carrying out a pressurized reaction at 110-130 °C for 15-20 h, and then alternately rinsing with deionized water and absolute ethanol. After drying, CoFe-LDH powder is obtained.

5. The preparation method of the composite ceramsite according to claim 4, characterized in that, The mass dosage ratio of Fe(NO3)3‧9H2O, Co(NO3)2‧6H2O and urea is 2:5:

3.

6. A composite ceramsite, characterized in that, Prepared by the preparation method of the composite ceramsite according to any one of claims 1-5.

7. Use of the composite ceramsite according to claim 6, characterized in that, The composite ceramsite is used as a catalyst in the process of removing diuron in the DBDP system.

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