A catalyst for ozone catalytic oxidation and degradation of coal chemical wastewater and a preparation method thereof

Abstract

This invention discloses a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation and its preparation method. The catalyst utilizes a sodium hydroxide-modified composite support of γ-alumina and Y-type molecular sieves, with iron / bismuth co-doped components as the active components, and is prepared using a hydrothermal method. Sodium hydroxide solution modification optimizes the support loading capacity, iron / bismuth co-doping increases active sites, and the addition of sucrose and urea provides synergistic catalysis, improving ozone catalytic efficiency and accelerating the degradation of organic matter and COD in coal wastewater. The catalyst prepared by this invention has a simple preparation process, good catalytic oxidation effect, and no secondary pollution, showing broad market prospects in wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of catalyst synergistic degradation of coal chemical wastewater, and particularly to a catalyst for ozone catalytic oxidation synergistic degradation of coal chemical wastewater and its preparation method. Background Technology

[0002] Wastewater discharged from coal chemical enterprises is mainly high-concentration coal gas washing wastewater, which contains a large amount of organic matter such as phenols, ammonia nitrogen, furan, and pyridine, as well as heavy metal ions. It is an industrial wastewater containing recalcitrant organic compounds, which can cause great harm to the environment, water sources, animals and plants, and human health.

[0003] Currently, biochemical methods are mainly used in China to treat coal chemical wastewater. However, these methods are complex and have significant limitations, and they are ineffective at treating recalcitrant organic matter, making it difficult for the CODcr levels of coal chemical industry wastewater to meet discharge standards. Therefore, a series of methods have been developed, including coagulation, membrane separation, Fenton oxidation, and heterogeneous catalytic ozone oxidation, which can degrade recalcitrant organic matter in wastewater.

[0004] Heterogeneous catalytic ozone oxidation technology shows the greatest potential in the treatment of coal chemical wastewater, being a highly efficient, clean, and low-cost technology. The catalysts used in heterogeneous catalytic ozone oxidation technology have been extensively studied. Ozone is a strong oxidant; during oxidation, ozone molecules can directly oxidize organic matter, and they can also first decompose in water to generate highly oxidizing free radicals, which then react with organic matter. The ozone oxidation of organic matter is very rapid and of great research value, thus leading to a series of advanced oxidation technologies aimed at promoting ozone decomposition and generating ·OH, including UV / O3, UV / TiO2 / O3, and UV / H2O2 / O3.

[0005] Chinese patent CN 106540706 B discloses an ozone oxidation catalyst supported on transition metals and rare earth metals. Rare earth elements are scarce and difficult to mine, resulting in high catalyst preparation costs. Chinese patent CN 117735697 A discloses a method for ozone catalytic oxidation degradation of wastewater containing high concentrations of isopropanol. This technology uses magnesium oxide as a catalyst to catalyze ozone, effectively removing isopropanol from industrial wastewater in a short time. However, due to the single active component of the catalyst, the degradation efficiency decreases significantly when the types of pollutants in the wastewater are complex.

[0006] Therefore, it is particularly important to provide a catalyst that is simple to prepare, low in cost, and highly efficient in catalyzing the degradation of pollutants by ozone. Summary of the Invention

[0007] This invention provides a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation and its preparation method. The invention uses alumina and molecular sieves as a composite support, modifies the support with sodium hydroxide, loads iron / bismuth dual-doped active sites, and adds sucrose and urea for synergistic catalysis to improve ozone catalytic efficiency, thus preparing a highly efficient and clean catalyst with multiple active sites; the alumina is γ-alumina, and the molecular sieve is a Y-type molecular sieve.

[0008] To achieve the above objectives, the present invention provides a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation. The catalyst uses modified alumina and molecular sieve as a composite support, and supports iron / bismuth dual doping as the active component; sucrose and urea are added for synergistic catalysis; the alumina is γ-alumina, and the molecular sieve is Y-type molecular sieve.

[0009] This invention also provides a method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation, comprising:

[0010] γ-alumina and Y-type molecular sieve were mixed and added to a sodium hydroxide solution, and then ultrasonically dispersed to obtain solution A;

[0011] Polydiethanol, urea, and iron salt are stirred and mixed evenly, and then added dropwise to solution A. The mixture is stirred at room temperature for 1-2 hours to obtain solution B.

[0012] Sucrose and bismuth salt were added to solution B under stirring. After hydrothermal reaction, washing and centrifugation were performed, and the solution was transferred to a tube furnace for calcination to obtain the target catalyst.

[0013] Preferably, the iron salt is ferrous sulfate (FeSO4·7H2O), the polyethylene glycol is polyethylene glycol-200 (PEG-200), and the bismuth salt is bismuth nitrate pentahydrate (Bi(NO3)3·5H2O).

[0014] Preferably, the mass ratio of alumina to molecular sieve is 1:(0.51 to 0.88).

[0015] Preferably, the sodium hydroxide solution has a concentration of 0.1–0.2 mol / L and a volume of 30–40 mL.

[0016] Preferably, the mass ratio of polyethylene glycol to urea and iron salt is 1:(0.02):(0.6-0.7).

[0017] Preferably, the mass ratio of sucrose to bismuth salt is 1:(4.5-5.3).

[0018] Preferably, the hydrothermal reaction temperature is 180–240°C, and the reaction time is 8–12 h.

[0019] Preferably, the calcination temperature is increased to 500-650°C at a programmed rate of 5°C / min, and the calcination time is 1-3 hours.

[0020] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0021] (1) The present invention uses a composite support of sodium hydroxide-modified γ-alumina and Y-type molecular sieve. γ-alumina has basic, neutral and acidic sites, while Y-type molecular sieve has strong acidic sites. The composite support can provide acidic, neutral and basic sites at the same time, which is beneficial to the catalytic reaction. At the same time, Y-type molecular sieve can provide additional thermal stability, and the skeleton structure of γ-alumina can provide good mechanical support, making the composite material more stable at high temperature.

[0022] (2) The active component of the catalyst prepared in this invention is an iron / bismuth bimetallic doped component. 2+ and Bi 3+ A synergistic effect is generated during the catalytic process of the system, improving the catalytic oxidation efficiency of ozone. Iron is a bandgap metal with abundant d electrons, which can participate in a variety of redox reactions. Bismuth doping can change its own electronic structure. The combination of the two metals forms a richer band structure, which helps the catalyst provide suitable energy levels in the catalytic reaction. At the same time, it modulates the surface band structure of the catalyst, enhances the adsorption and activation performance of the catalyst, and improves the adsorption capacity and catalytic activity of reactants.

[0023] (3) Sucrose and urea are added to the catalyst prepared in this invention. Sucrose is an organic carbon source that provides carbon to the catalyst. Sucrose is chosen because it has good solubility, is green and non-toxic, and can reduce the use of organic solvents. At the same time, sucrose can provide active sites in the catalytic reaction, shortening the reaction time. Urea, as a nitrogen-containing compound, provides nitrogen to the catalyst and forms coordination bonds at the active sites of the catalyst, increasing the activity of the catalyst. The intramolecular interactions of sucrose and urea can affect the structure and performance of the catalyst through hydrogen bonds, van der Waals forces, etc. The pyrolysis during the catalyst preparation process can form different carbon materials and release nitrogen gas. It can also participate in electron transfer or sharing, thereby regulating the reducing and oxidizing properties of the catalyst. Attached Figure Description

[0024] Figure 1 The content and removal rate of COD in coal chemical wastewater after 4 hours of catalyst treatment. Detailed Implementation

[0025] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0026] Example 1

[0027] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation includes the following steps:

[0028] (1) Accurately weigh 10g of γ-alumina and 5.1g of Y-type molecular sieve and add them to 40ml of 0.1mol / L sodium hydroxide aqueous solution. Disperse the mixture by ultrasonication for 15-30min to obtain the modified carrier solution.

[0029] (2) Accurately weigh 5.56g of FeSO4·7H2O, 0.16g of urea and 7ml of PEG-200, mix them evenly, stir at room temperature for 10-20min, add the modified carrier solution dropwise, and stir at room temperature for 1-2h to obtain the mixed solution.

[0030] (3) Accurately weigh 3.16g Bi(NO3)3·5H2O and 0.6g sucrose and add them to the mixed solution. Stir for 20-30 min and hydrothermally react at 180-240℃ for 8-12 h. After washing and centrifuging, transfer to a tube furnace and calcine at 500-650℃ for 1-3 h at a rate of 5℃ / min to obtain the catalyst.

[0031] Example 2

[0032] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation includes the following steps:

[0033] (1) Accurately weigh 10g of γ-alumina and 7.2g of Y-type molecular sieve and add them to 40ml of sodium hydroxide aqueous solution with a concentration of 0.15mol / L. Disperse the mixture by ultrasonication for 15-30min to obtain the modified carrier solution.

[0034] (2) Accurately weigh 6.32g of FeSO4·7H2O, 0.16g of urea and 7ml of PEG-200, mix them evenly, stir at room temperature for 10-20min, add the modified carrier solution dropwise, and stir at room temperature for 1-2h to obtain the mixed solution.

[0035] (3) Accurately weigh 2.37g Bi(NO3)3·5H2O and 0.6g sucrose and add them to the mixed solution. Stir for 20-30 min and perform hydrothermal reaction at 180-240℃ for 8-12 h. After washing and centrifugation, transfer the mixture to a tube furnace and calcine at 500-650℃ for 1-3 h at a rate of 5℃ / min to obtain the catalyst.

[0036] Example 3

[0037] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation includes the following steps:

[0038] (1) Accurately weigh 10g of γ-alumina and 8.8g of Y-type molecular sieve and add them to 40ml of sodium hydroxide aqueous solution with a concentration of 0.2mol / L. Disperse the mixture by ultrasonication for 15-30min to obtain the modified carrier solution.

[0039] (2) Accurately weigh 4.87g of FeSO4·7H2O, 0.16g of urea and 7ml of PEG-200, mix them evenly, stir at room temperature for 10-20min, add the modified carrier solution dropwise, and stir at room temperature for 1-2h to obtain the mixed solution.

[0040] (3) Accurately weigh 2.68g Bi(NO3)3·5H2O and 0.6g sucrose and add them to the mixed solution. Stir for 20-30 min and hydrothermally react at 180-240℃ for 8-12 h. After washing and centrifuging, transfer the solution to a tube furnace and calcine at 500-650℃ for 1-3 h at a rate of 5℃ / min to obtain the catalyst.

[0041] Comparative Example 1

[0042] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation is different from Example 1 in that Bi(NO3)3·5H2O is not added in step (2).

[0043] Comparative Example 2

[0044] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation is different from Example 1 in that sucrose is not added in step (2).

[0045] Comparative Example 3

[0046] A method for preparing a catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation is different from Example 1 in that the sodium hydroxide solution in step (1) is replaced with anhydrous ethanol.

[0047] Catalyst activity test:

[0048] (1) COD removal rate test: The test device included an oxygen tube, an ozone generator, a reaction glass column, and a tail gas recovery device. The glass column contained 600 mL of coal chemical wastewater. The total COD was 2140 mg / L. A sampling port was provided in the middle of the glass column. The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were loaded into the device. The flow rate of the ozone generator was set to 0.5 L / min, and samples were taken at 1-hour intervals. The COD of the samples was analyzed using a water quality analyzer. The results are shown in Table 1.

[0049] (2) Phenol removal rate test: The experimental setup was the same as that for the COD removal rate test, except that a laboratory-prepared phenol solution with a concentration of 600 mg / L was placed in a glass column to simulate coal chemical wastewater, and the ozone generator flow rate was 0.5 L / min. After 0.5 h of ozone catalytic reaction, the phenol content of the sample was analyzed using a water quality analyzer. The results are shown in Table 1.

[0050] Table 1. Content and removal rate of COD and phenol in coal chemical wastewater after 4 hours of catalyst treatment.

[0051]

[0052] According to the data in Table 1, the catalysts prepared in Examples 1-3 showed significant catalytic ozone synergistic degradation of coal chemical wastewater, with removal rates of COD and phenol exceeding 80%. Example 1 showed the best results, with removal rates of COD and phenol exceeding 90%. This was attributed to the modification of the carrier surface with sodium hydroxide, the addition of sucrose, and the loading of iron / bismuth dual-doped metal active components in the examples.

[0053] Compared with Example 1, Comparative Example 1 did not add Bi(NO3)3·5H2O. The effect of the prepared catalyst on synergistic degradation of wastewater was significantly reduced. The removal rate of COD and phenol in the wastewater was only about 40%. This is because the active component loaded is only iron. The activity of a single metal is low and there is a lack of synergistic effect with other metal elements. Furthermore, a single metal is prone to oxidation in complex catalytic reaction processes, which reduces catalytic activity.

[0054] Compared to Example 1, Comparative Example 2 did not add sucrose, resulting in a decrease in the activity of the prepared catalyst. The synergistic degradation rates of COD and phenol in the wastewater were 51.72% and 47.31%, respectively. In the catalytic reaction, sucrose and urea synergistically provided active sites for the catalyst, shortened the reaction time, and regulated the catalytic process. The catalyst without added sucrose had reduced activity, required a relatively longer activation time, and thus reduced degradation efficiency.

[0055] Compared to Example 1, Comparative Example 3 did not use sodium hydroxide modification on the support. Sodium hydroxide can increase the specific surface area of ​​the support and increase the active functional groups on the support surface, which is beneficial for loading more active components, thereby improving its loading capacity and catalytic performance. In Comparative Example 3, no sodium hydroxide modification was used, resulting in a reduced support loading capacity and a decrease in the number of active components loaded, thereby reducing catalytic activity and synergistic catalytic ability. The removal rates of COD and phenol in the wastewater were only 53.83% and 43.68%, respectively.

[0056] In summary, using a sodium hydroxide-modified composite support, iron / bismuth bimetallic doped active components, and adding sucrose and urea to provide carbon and nitrogen sources, as well as synergistic catalysis, are effective means to improve the activity of catalysts for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered as protection of the present invention.

Claims

1. A catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation, characterized in that, The catalyst uses modified alumina and molecular sieve as a composite support, with iron / bismuth dual doping as the active component loaded on the composite support; sucrose and urea are added for synergistic catalysis; the alumina is γ-alumina, and the molecular sieve is Y-type molecular sieve; the modification method of the modified alumina is as follows: γ-alumina and Y-type molecular sieve are mixed and added to sodium hydroxide solution, and ultrasonically dispersed to obtain a modified alumina dispersion; the method of loading the composite support with iron / bismuth dual doping as the active component is as follows: polyethylene glycol, urea, and iron salt are stirred and mixed evenly, and added dropwise to the modified alumina dispersion, stirred at room temperature for 1-2 h, sucrose and bismuth salt are added while stirring, and hydrothermally reacted at 180-240℃ for 8-12 h, the obtained solid product is washed, centrifuged and transferred to a tube furnace, the temperature is programmed to rise to 500-650℃ at 5℃ / min, and calcined for 1-3 h to obtain the target catalyst.

2. The catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation according to claim 1, characterized in that, The iron salt is ferrous sulfate, the polyethylene glycol is polyethylene glycol 200, and the bismuth salt is bismuth nitrate pentahydrate.

3. The catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation according to claim 1, characterized in that, The mass ratio of γ-alumina to Y-type molecular sieve is 1:(0.51~0.88).

4. The catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation according to claim 1, characterized in that, The sodium hydroxide solution has a concentration of 0.1~0.2 mol / L and a volume of 30~40 mL.

5. The catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation according to claim 1, characterized in that, The mass ratio of polyethylene glycol, urea, and iron salt is 1:(0.02):(0.6~0.7).

6. The catalyst for the synergistic degradation of coal chemical wastewater by ozone catalytic oxidation according to claim 1, characterized in that, The mass ratio of sucrose to bismuth salt is 1:(4.5~5.3).

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