Preparation methods of tandem catalysts and their application in the degradation of organic matter in wastewater.

Abstract

This invention provides a method for preparing a tandem catalyst and its application in degrading organic matter in wastewater, belonging to the field of wastewater treatment technology. The tandem catalyst is prepared by co-precipitation of ferrous chloride, ferric chloride, and aluminum nitrate, followed by grinding and calcination with high-temperature kerosene and activated carbon. The tandem catalyst is then applied to degrade organic matter in wastewater. The tandem catalyst prepared by this invention comprises a hierarchical porous carbon support and a co-precipitate of iron(III) oxide and aluminum(III) oxide supported on the surface of the hierarchical porous carbon support. Using hierarchical porous carbon as the support and aluminum(III) oxide and iron(III) oxide in series as the catalyst facilitates the ozone decomposition of organic matter. The tandem catalyst of this invention can effectively degrade organic matter, achieving a degradation rate of over 95% for both total cyanide and ammonia nitrogen.

Description

Technical Field

[0001] This invention relates to a catalyst and its application in wastewater treatment, and more particularly to a method for preparing a tandem catalyst and its application in degrading organic matter in wastewater. Background Technology

[0002] The treatment of cyanide-containing wastewater has always been a key focus for gold mining companies. According to national standards, the total cyanide content in wastewater discharged by general enterprises should not exceed 0.5 mg / L. Incomplete statistics indicate that there are over 20 cyanide-containing wastewater treatment technologies both domestically and internationally. Early methods included chlorination oxidation, sulfur dioxide-gas oxidation, acidification recovery, Fenton oxidation, and metal ion complexation. In recent years, new technologies such as radiation oxidation, ultrasonic oxidation, supercritical water oxidation, biological oxidation, and photocatalytic oxidation have been developed. Each of these methods has its own characteristics. Homogeneous treatment methods are suitable for large-scale cyanide-containing wastewater treatment, as the reagents and wastewater system are mixed relatively evenly, accelerating the reaction rate and improving treatment efficiency. However, the reagents and system form a homogeneous phase that is difficult to separate, potentially causing secondary pollution. Heterogeneous treatment methods are suitable for treating low-concentration cyanide-containing wastewater, as the added reagents are easily separated without causing secondary pollution.

[0003] Heterogeneous catalytic ozone oxidation technology typically refers to a reaction system where the catalyst and the reaction system are in different phases, with the reaction generally occurring at the gas-liquid, gas-solid, liquid-solid, or gas-liquid-solid interface. The catalysts used are mostly solid-state and are primarily divided into supported and unsupported catalysts. Commonly used catalysts include molecular sieves, activated carbon, diatomaceous earth, activated alumina, and metals and their oxides supported on a carrier. Heterogeneous catalytic ozone oxidation technology effectively combines the adsorption and catalytic effects of the catalyst with the strong oxidizing power of ozone, thereby significantly improving wastewater treatment efficiency and reducing treatment costs. However, the performance of the catalyst not only affects the ozone oxidation capacity but also the efficiency and outcome of wastewater treatment. Finding more efficient catalysts has always been a hot topic in heterogeneous catalytic oxidation technology research. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing a tandem catalyst and its application in degrading organic matter in wastewater.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a tandem catalyst includes the following steps:

[0007] S1. Take ferrous chloride, ferric chloride, aluminum nitrate and dispersant and disperse them together in an ethanol aqueous solution. Add ammonia water dropwise to co-precipitate, filter and wash to obtain the coprecipitate.

[0008] S2. The co-precipitate is directly ground with high-temperature kerosene and activated carbon, and then calcined to obtain the tandem catalyst.

[0009] Furthermore, in step S1, the molar ratio of ferrous chloride, ferric chloride, and aluminum nitrate is 1:2 to 2.1:1.2 to 1.3.

[0010] Furthermore, the dispersant is polyethylene glycol.

[0011] Furthermore, in step S1, the weight ratio of ferrous chloride to dispersant is 1:0.1 to 0.15.

[0012] Furthermore, in step S2, the calcination is carried out at a heating rate of 5°C / min to 1000-1050°C for 3-3.2 hours.

[0013] Furthermore, the weight ratio of coal tar to ferrous chloride is 0.15 to 0.20:1.

[0014] Furthermore, the weight ratio of the activated carbon to the ferrous chloride is 9.4 to 9.6:1.

[0015] The application of the tandem catalyst prepared by the above preparation method in the degradation of organic matter in wastewater.

[0016] Furthermore, the application involves taking wastewater and introducing ozone under the catalytic action of the series catalysts to degrade the organic matter in the wastewater.

[0017] Furthermore, after ozone was introduced, the concentration of ozone in the resulting system was maintained at 2.5–3.0 mg / L, and the degradation time was maintained at more than 1 hour.

[0018] After degradation, the degradation rates of total cyanide and ammonia nitrogen in the wastewater were both above 95%.

[0019] The beneficial effects of the preparation method of the tandem catalyst of the present invention and its application in the degradation of organic matter in wastewater are as follows:

[0020] In the application of the tandem catalyst of the present invention, the Fe active component and the Al active component can simultaneously adsorb H2O molecules to form surface hydroxyl groups, thereby promoting the decomposition of O3 molecules into more oxidizing ·OH, which then undergoes an oxidation reaction with the organic matter adsorbed on the catalyst surface.

[0021] In the application of the tandem catalyst of the present invention, organic matter can be first adsorbed onto the surface of the tandem catalyst, and then... 2+ Fe 3+ And Al 3+The inductive effect of the coordination electron pairs forms a complex, which is then directly attacked by O3 molecules and oxidized and decomposed.

[0022] The tandem catalyst of the present invention comprises a hierarchical porous carbon support (i.e., activated carbon) and a co-precipitate of iron oxide and aluminum oxide supported on the surface of the hierarchical porous carbon support. Using hierarchical porous carbon as a support and aluminum oxide and iron oxide in series as a catalyst is beneficial to the ozone decomposition of organic matter.

[0023] This invention employs a co-precipitation method of iron oxide and aluminum oxide, which enables iron oxide to be uniformly loaded onto the surface of aluminum oxide. The co-precipitate is then loaded onto the surface of activated carbon through grinding. By using a series loading method, organic matter to be degraded is adsorbed, and the electron transfer ability between metal ions of different valence states in the series is used to promote the decomposition of O3 and generate active oxygen substances, thereby improving the removal efficiency of organic pollutants.

[0024] The tandem catalyst of this invention can effectively degrade organic matter, and the degradation rate of total cyanide and ammonia nitrogen can reach more than 95%. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Example 1: A method for preparing a tandem catalyst and its application in degrading organic matter in wastewater.

[0027] I. Preparation methods of tandem catalysts

[0028] This embodiment describes a method for preparing a tandem catalyst, and the specific preparation process includes the following steps:

[0029] S1. Take 0.1 mol (12.7 g) ferrous chloride, 0.2 mol (54.1 g) ferric chloride hexahydrate (equivalent to 2 mol ferric chloride) and 0.12 mol (18.2 g) aluminum nitrate nonahydrate (equivalent to 1.2 mol aluminum nitrate) and add them to 2 L of ethanol aqueous solution with a concentration of 10-15 wt% (in this example, the concentration of ethanol aqueous solution is 10 wt%). Then add 1.27 g polyethylene glycol as a dispersant and stir at room temperature to mix. While maintaining room temperature stirring, add saturated ammonia dropwise to coprecipitate. During the addition of saturated ammonia, particles are generated. Stop adding when no particles are generated in the solution. At this time, the system is neutral (i.e., the pH of the system is about 7). Filter, wash with deionized water, filter again to obtain the coprecipitate.

[0030] S2. The obtained coprecipitate does not need to be dried. It is directly ground with 1.95g of high-temperature coal tar and 120g of activated carbon at a pressure of 0.03-0.05MPa and a speed of 10-15m / s for 5-8min (in this embodiment, the grinding pressure is 0.05MPa, the speed is 10m / s, and the time is 5min). The resulting ground material is placed in a tube furnace and heated to 1000-1050℃ at a heating rate of 5℃ / min for 3-3.2h (in this embodiment, the calcination temperature is 1000℃ and the time is 3h) to obtain the tandem catalyst, labeled M1.

[0031] II. Application of Tandem Catalysts in the Degradation of Organic Matter in Wastewater

[0032] The series catalyst M1 was loaded into the heterogeneous catalytic ozone oxidation device. At room temperature, conventionally treated cyanide-containing wastewater (i.e., sewage) was fed into the heterogeneous catalytic ozone oxidation device at an influent flow rate of 1.2 m³ / h. 3 / h, and with the ozone concentration introduced into the ozone maintenance system at 2.5-3.0 mg / L (3.0 mg / L in this embodiment), ozone oxidation degradation is carried out for more than 1 hour (that is, the residence time of cyanide-containing wastewater in the heterogeneous catalytic ozone oxidation device is maintained for more than 1 hour, and the residence time is 1 hour in this embodiment), thus obtaining the degraded water.

[0033] The total cyanide concentration in the conventionally treated cyanide-containing wastewater was 8.6 mg / L, the ammonia nitrogen concentration was 265 mg / L, and the COD concentration was 1076 mg / L.

[0034] The total cyanide concentration in the degraded water was 0.41 mg / L, the ammonia nitrogen concentration was 10.4 mg / L, and the COD concentration was 74.2 mg / L. The degradation rates of total cyanide, ammonia nitrogen, and COD were 95.23%, 96.08%, and 93.10%, respectively.

[0035] In this embodiment, the total cyanide concentration was determined according to the standard GB / T7486-1987, "Determination of Cyanide in Water - Part 1: Determination of Total Cyanide".

[0036] The concentration of ammonia nitrogen was determined according to the Nessler's reagent colorimetric method for the determination of ammonium in water (GB / T7479-1987).

[0037] The COD concentration was determined according to the standard "Determination of Chemical Oxygen Demand in Water - Dichromate Method" (HJ828-2017).

[0038] Examples 2-5: Preparation methods of tandem catalysts and their application in the degradation of organic matter in wastewater.

[0039] Examples 2-5 illustrate a method for preparing a tandem catalyst and its application in degrading organic matter in wastewater. The steps are essentially the same as in Example 1, differing only in the amount of raw materials and process parameters. See Table 1 for details.

[0040] Table 1. Summary of process parameters in Examples 2-5

[0041]

[0042] The contents of other parts of Examples 2 to 5 are the same as those of Example 1, and will not be repeated here.

[0043] Comparative Example

[0044] Comparative Examples 1-5 are comparative experiments on the preparation process of the tandem catalyst in Example 1 and its application in the degradation of organic matter in wastewater. The only difference is that:

[0045] In step S1 of Comparative Example 1, instead of adding aluminum nitrate nonahydrate, 0.13 mol of ferrous chloride and 0.28 mol of ferric chloride hexahydrate were added for co-precipitation. The prepared tandem catalyst was labeled DM1. The tandem catalyst DM1 was used to degrade organic matter in conventionally treated cyanide-containing wastewater. The total cyanide concentration in the conventionally treated cyanide-containing wastewater was 8.4 mg / L, the ammonia nitrogen concentration was 257 mg / L, and the COD concentration was 1094 mg / L. After degradation, the total cyanide concentration in the water was 3.64 mg / L, the ammonia nitrogen concentration was 174.6 mg / L, and the COD concentration was 759.8 mg / L. The degradation rates were 56.67%, 32.06%, and 30.55%, respectively.

[0046] In step S1 of Comparative Example 2, ferrous chloride and ferric chloride hexahydrate were not added. Instead, 0.42 mol of aluminum nitrate nonahydrate was added for co-precipitation, and the prepared tandem catalyst was labeled DM2. The organic matter in the conventionally treated cyanide-containing wastewater was degraded using the tandem catalyst DM2. The total cyanide concentration in the conventionally treated cyanide-containing wastewater was 8.0 mg / L, the ammonia nitrogen concentration was 274 mg / L, and the COD concentration was 1066 mg / L. After degradation, the total cyanide concentration in the water was 5.62 mg / L, the ammonia nitrogen concentration was 234.2 mg / L, and the COD concentration was 897.4 mg / L. The degradation rates were 29.75% for total cyanide, 14.53% for ammonia nitrogen, and 15.82% for COD.

[0047] In step S1 of Comparative Example 3, ferrous chloride, ferric chloride hexahydrate, and aluminum nitrate nonahydrate were co-precipitated in a molar ratio of 1:2:2 (the total molar number of ferrous chloride, ferric chloride hexahydrate, and aluminum nitrate nonahydrate remained at 4.2 mol). The prepared tandem catalyst was labeled DM3. The tandem catalyst DM3 was used to degrade organic matter in conventionally treated cyanide-containing wastewater. The total cyanide concentration in the conventionally treated cyanide-containing wastewater was 7.8 mg / L, the ammonia nitrogen concentration was 252 mg / L, and the COD concentration was 1057 mg / L. After degradation, the total cyanide concentration in the water was 1.27 mg / L, the ammonia nitrogen concentration was 58.1 mg / L, and the COD concentration was 189.3 mg / L. The degradation rates were 83.72%, 76.94%, and 82.09%, respectively.

[0048] In step S1 of Comparative Example 4, ferrous chloride, ferric chloride hexahydrate, and aluminum nitrate nonahydrate were co-precipitated in a molar ratio of 1:2:0.5 (the total molar number of ferrous chloride, ferric chloride hexahydrate, and aluminum nitrate nonahydrate remained at 4.2 mol). The prepared tandem catalyst was labeled DM4. The tandem catalyst DM4 was used to degrade organic matter in conventionally treated cyanide-containing wastewater. The total cyanide concentration in the conventionally treated cyanide-containing wastewater was 8.5 mg / L, the ammonia nitrogen concentration was 273 mg / L, and the COD concentration was 1073 mg / L. After degradation, the total cyanide concentration in the water was 1.25 mg / L, the ammonia nitrogen concentration was 56.7 mg / L, and the COD concentration was 167.4 mg / L. The degradation rates were 85.29%, 79.23%, and 84.40%, respectively.

[0049] In step S2 of Comparative Example 5, the calcination temperature was 800℃, and the prepared tandem catalyst was labeled DM5. The tandem catalyst DM5 was used to degrade organic matter in conventionally treated cyanide-containing wastewater. The conventionally treated wastewater contained 8.7 mg / L of total cyanide, 284 mg / L of ammonia nitrogen, and 1082 mg / L of COD. After degradation, the wastewater contained 1.23 mg / L of total cyanide, 55.9 mg / L of ammonia nitrogen, and 164.1 mg / L of COD, with degradation rates of 85.86%, 80.32%, and 84.83% for total cyanide, ammonia nitrogen, and COD.

[0050] By comparing the degradation results of the application process of the embodiments of the present invention with the degradation results of the comparative examples, it can be seen that the tandem catalyst prepared by the present invention can better treat organic matter in wastewater.

[0051] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. The application of a tandem catalyst in the degradation of organic matter in wastewater, characterized in that, The application involves taking wastewater and introducing ozone under the catalytic action of the series catalysts to degrade the organic matter in the wastewater. The preparation method of the tandem catalyst includes the following steps: S1. Ferrous chloride, ferric chloride, aluminum nitrate, and polyethylene glycol are dispersed together in an ethanol aqueous solution. Ammonia water is added dropwise for co-precipitation. The mixture is filtered and washed to obtain the coprecipitate. The molar ratio of ferrous chloride, ferric chloride, and aluminum nitrate is 1:2~2.1:1.2~1.

3. The weight ratio of ferrous chloride to polyethylene glycol is 1:0.1~0.

15. S2. The coprecipitate is directly ground with high-temperature coal tar and activated carbon, and then calcined to obtain the tandem catalyst. The calcination is carried out by heating to 1000~1050℃ at a heating rate of 5℃ / min and calcining for 3~3.2h; The tandem catalyst includes an activated carbon support.

2. The application according to claim 1, characterized in that, The weight ratio of the high-temperature coal tar to ferrous chloride is 0.15~0.20:

1.

3. The application according to claim 1, characterized in that, The weight ratio of activated carbon to ferrous chloride is 9.4~9.6:

1.

4. The application according to claim 1, characterized in that, After ozone was introduced, the concentration of ozone in the resulting system was maintained at 2.5~3.0 mg / L, and the degradation time was maintained at more than 1 hour.

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