Adsorbent for treating high-concentration COD (Chemical Oxygen Demand) biochemical tail water as well as preparation method and application of adsorbent

Abstract

The invention belongs to the technical field of wastewater treatment materials, and relates to an adsorbent, in particular to an adsorbent for high-concentration COD biochemical tail water treatment and a preparation method and application thereof.The preparation method comprises the following steps that S1, activated carbon is subjected to nitrogen doping treatment, and nitrogen-doped activated carbon is obtained; s2, carrying out oxidation treatment on the nitrogen-doped activated carbon to obtain oxidized-nitrogen-doped activated carbon; s3, treating the oxidized-nitrogen-doped activated carbon under oxygen-enriched and low-pressure conditions to obtain the adsorbent. The adsorbent provided by the invention not only improves the adsorption effect, but also has high oxygen carrying performance, is used for treating high-concentration COD biochemical tail water, not only can efficiently adsorb suspended particulate matters so as to avoid adverse effects on a subsequent membrane treatment device, but also can release oxygen into the tail water so as to improve the oxygen content in the tail water, so that the treatment effect of the high-concentration COD biochemical tail water is improved. The activity of microorganisms in the aerobic biochemical treatment process is enhanced, so that the treatment effect is improved.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment materials technology, and relates to an adsorbent, specifically an adsorbent for treating high-concentration COD biochemical tailwater, its preparation method and application. Background Technology

[0002] With the continuous innovation and upgrading of industrial production technology, industrial organic wastewater has become increasingly diverse in terms of organic matter, concentration, toxicity, salt content, and composition, resulting in poorer biodegradability. At the same time, the pollution of the environment and the impact on human health caused by industrial wastewater have received increasing attention.

[0003] In wastewater treatment, adsorption is usually performed first, often requiring the use of adsorbents to remove suspended solids and other contaminants. Activated carbon is a commonly used adsorbent. However, the adsorption effect of activated carbon alone is limited. To further improve the adsorption effect, new adsorbent materials are constantly emerging in existing technologies. For example, CN108295823A discloses a special adsorbent for textile wastewater treatment. The adsorbent, expressed by weight, comprises 50-60 parts polyacrylamide, 10-15 parts calcium oxide, 8-10 parts polyaluminum sulfate, 3-5 parts photoinitiator, 6-8 parts catalyst, 2-3 parts surfactant, and 3-5 parts stabilizer. The adsorbent is activated carbon.

[0004] This approach aims to enhance the adsorption capacity of polyacrylamide by inducing its absorption, and simultaneously improves the surface activity of polyacrylamide through surfactants, further enhancing the adsorption capacity of the adsorbent and thus meeting the application requirements for textile wastewater treatment. Another example is an adsorbent for treating dye and printing and dyeing wastewater disclosed in CN108993429A. This adsorbent is composed of a two-component mixture of activated carbon and cross-linked cationic starch, or a two-component mixture of activated carbon and cross-linked cationic polyvinyl alcohol, or a three-component mixture of activated carbon, cross-linked cationic starch, and cross-linked cationic polyvinyl alcohol, to address the problem of insufficient adsorption capacity of existing adsorbents when treating dye and printing and dyeing wastewater.

[0005] One approach to treating high-concentration COD biological wastewater is the biological method, which utilizes eutrophic or anaerobic reactions of microbial communities to consume the soluble COD in the wastewater. Considering the treatment effect, treatment cost, and environmental friendliness, this method can be considered the preferred approach for treating high-concentration COD biological wastewater.

[0006] The existing adsorbents mentioned above mostly focus on their basic adsorption effect without linking the wastewater treatment steps to the adsorption effect. As a result, the use of these adsorbents does not bring direct positive effects on COD removal. Summary of the Invention

[0007] The purpose of this invention is to provide an adsorbent for treating high-concentration COD biochemical wastewater and its preparation method, in order to solve the technical problem that existing adsorbents have limited COD removal efficiency when used in biological treatment of biochemical wastewater containing high concentrations of COD.

[0008] The first aspect of the present invention provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0009] S1. Nitrogen doping treatment is applied to activated carbon to obtain nitrogen-doped activated carbon;

[0010] S2. The nitrogen-doped activated carbon is oxidized to obtain oxidized nitrogen-doped activated carbon;

[0011] S3. The nitrogen oxide-doped activated carbon is subjected to treatment under oxygen-rich and low-pressure conditions to obtain an adsorbent.

[0012] In the above scheme, activated carbon is subjected to nitrogen doping, oxidation, and oxygen collection treatment. The adsorbent after this treatment, when used for the treatment of high-concentration COD biological wastewater, can not only remove suspended solids and metal ions through adsorption via the pores of the adsorbent, but also release the oxygen accumulated in the oxygen collection treatment into the wastewater. This provides sufficient oxygen for the aerobic biological treatment to remove organic matter from the wastewater, creating a favorable environment for aerobic bacteria and greatly improving the removal efficiency of organic matter.

[0013] Nitrogen doping, by introducing nitrogen into activated carbon, alters its electronic structure, thereby enhancing its oxygen adsorption capacity. The presence of nitrogen atoms creates new active sites, which positively influence the physisorption of oxygen.

[0014] The specific surface area and total pore volume of activated carbon after surface oxidation modification decreased to varying degrees, with the degree of reduction being directly proportional to the severity of the oxidation modification conditions. The reason for this reduction is speculated to be the strong corrosion of the pores on the inner surface of the activated carbon by the oxidant, leading to pore collapse and blockage of the micropores, thus reducing the specific surface area and total pore volume.

[0015] In this scheme, after nitrogen doping treatment, oxidation modification treatment is carried out. This not only overcomes the reduction in specific surface area and total pore volume caused by oxidation treatment, but also helps nitrogen doping treatment to further increase the oxygen adsorption and carrying capacity of activated carbon.

[0016] Preferably, the nitrogen doping treatment involves mixing activated carbon with a nitrogen source reagent, adding anhydrous ethanol, magnetically stirring and mixing, heating and refluxing in a constant temperature water bath for 3–20 hours, filtering, washing with deionized water, drying, and then calcining under nitrogen protection.

[0017] Preferably, the oxidation treatment involves subjecting nitrogen-doped activated carbon to high-temperature treatment in an ozone atmosphere at a temperature of 120°C to 130°C.

[0018] Preferably, in step S3, low pressure refers to a pressure value of 0.1 atm to 0.5 atm.

[0019] Preferably, in step S3, oxygen enrichment means that the oxygen concentration reaches 60% or more.

[0020] Preferably, the constant temperature condition is 60°C to 75°C.

[0021] In a second aspect, the present invention provides an adsorbent obtained by the preparation method described above.

[0022] In a third aspect, the present invention provides the application of the above-mentioned adsorbent for the treatment of high-concentration COD biochemical effluent.

[0023] A fourth aspect of the present invention provides a method for treating high-concentration COD biological wastewater, comprising the following steps:

[0024] S-1. High-concentration COD biochemical effluent is passed through a container filled with the above-mentioned adsorbent for adsorption and oxygenation treatment.

[0025] S-2. The effluent treated in step S-1 is sent to an aerobic tank for aerobic biochemical treatment, and microbial agents are added to the aerobic tank at the same time.

[0026] S-3. The effluent after step S-2 is subjected to deep filtration through a membrane treatment device to obtain treated effluent.

[0027] Preferably, in step S-1, the temperature inside the container is controlled to be above 50°C and below 70°C, and the pressure is below one standard atmosphere.

[0028] By implementing the above technical solution, the present invention has the following beneficial effects:

[0029] The adsorbent provided by this invention, in addition to improving its own adsorption effect, also has high oxygen carrying capacity. When used for the treatment of high-concentration COD biological wastewater, it can not only efficiently adsorb suspended particulate matter to avoid adverse effects on subsequent membrane treatment devices, but also release oxygen into the wastewater to increase the oxygen content in the wastewater, enhance the activity of microorganisms in the aerobic biological treatment process, and thus improve the treatment effect. Detailed Implementation

[0031] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

[0032] Example 1

[0033] This embodiment provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0034] S1. Activated carbon and melamine were mixed at a mass ratio of 1:4. After mixing, anhydrous ethanol was added at a volume of 20 ml / g. After stirring evenly, the mixture was heated and refluxed in a 60°C water bath for 20 h. Then, it was filtered, washed with deionized water, dried, and calcined at 550°C under nitrogen protection to obtain nitrogen-doped activated carbon.

[0035] S2. The nitrogen-doped activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain nitrogen oxide-doped activated carbon;

[0036] S3. The oxide-nitrogen doped activated carbon is treated under conditions where the oxygen concentration reaches 60% (volume ratio) or higher and 0.1 atm to obtain an adsorbent.

[0037] Example 2

[0038] This embodiment provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0039] S1. Activated carbon and melamine are mixed at a mass ratio of 1:3. After mixing, anhydrous ethanol is added at a volume of 20 ml / g. After stirring evenly, the mixture is heated and refluxed in a 60°C water bath for 20 h. Then, it is filtered, washed with deionized water, dried, and calcined at 550°C under nitrogen protection to obtain nitrogen-doped activated carbon.

[0040] S2. The nitrogen-doped activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain nitrogen oxide-doped activated carbon;

[0041] S3. The oxide-nitrogen doped activated carbon is treated under conditions where the oxygen concentration reaches 70% (volume ratio) and 0.2 atm to obtain an adsorbent.

[0042] Example 3

[0043] This embodiment provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0044] S1. Activated carbon and melamine were mixed at a mass ratio of 1:4. After mixing, anhydrous ethanol was added at a volume of 20 ml / g. After stirring evenly, the mixture was heated and refluxed in a 60°C water bath for 20 h. Then, it was filtered, washed with deionized water, dried, and calcined at 550°C under nitrogen protection to obtain nitrogen-doped activated carbon.

[0045] S2. The nitrogen-doped activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain nitrogen oxide-doped activated carbon;

[0046] S3. The oxide-nitrogen doped activated carbon is treated under conditions where the oxygen concentration reaches 65% (volume ratio) and 0.1 atm to obtain an adsorbent.

[0047] Example 4

[0048] This embodiment provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0049] S1. Activated carbon and melamine were mixed at a mass ratio of 1:4. After mixing, anhydrous ethanol was added at a volume of 20 ml / g. After stirring evenly, the mixture was heated and refluxed in a 60°C water bath for 20 h. Then, it was filtered, washed with deionized water, dried, and calcined at 550°C under nitrogen protection to obtain nitrogen-doped activated carbon.

[0050] S2. The nitrogen-doped activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain nitrogen oxide-doped activated carbon;

[0051] S3. The oxide-nitrogen doped activated carbon is placed in a nitrogen-oxygen (volume ratio 3:7) mixed gas and treated at 0.1 atm to obtain an adsorbent.

[0052] Comparative Example 0

[0053] This comparative example provides activated carbon, the raw material of Example 1, as an adsorbent.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing an adsorbent, comprising the following steps:

[0056] S1. Activated carbon and melamine are mixed at a mass ratio of 1:4. After mixing, anhydrous ethanol is added at a rate of 20 ml / g. The mixture is stirred evenly and then heated under reflux in a 60°C water bath for 20 h. After filtration, washing with deionized water, drying, and then calcining at 550°C under nitrogen protection, nitrogen-doped activated carbon adsorbent is obtained.

[0057] Comparative Example 2

[0058] This comparative example provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0059] S1. Activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain oxidized activated carbon;

[0060] S2. The oxide-nitrogen doped activated carbon is subjected to treatment under conditions where the oxygen concentration reaches 60% (volume ratio) or higher and 0.1 atm to obtain an adsorbent.

[0061] Comparative Example 3

[0062] This comparative example provides a method for preparing an adsorbent for treating high-concentration COD biochemical wastewater, comprising the following steps:

[0063] S1. Activated carbon and melamine were mixed at a mass ratio of 1:4. After mixing, anhydrous ethanol was added at a volume of 20 ml / g. After stirring evenly, the mixture was heated and refluxed in a 60°C water bath for 20 h. Then, it was filtered, washed with deionized water, dried, and calcined at 550°C under nitrogen protection to obtain nitrogen-doped activated carbon.

[0064] S2. The nitrogen-doped activated carbon is subjected to high-temperature treatment at 120°C in an ozone atmosphere to obtain nitrogen oxide-doped activated carbon adsorbent.

[0065] Comparative Example 4

[0066] An adsorbent for textile wastewater treatment, disclosed in CN108295823A.

[0067] Comparative Example 5

[0068] Weigh 50 grams of powdered activated carbon that has been pulverized and passed through an 80-mesh sieve, and weigh 50 grams of cross-linked cationic starch that has also been pulverized and passed through an 80-mesh sieve. Mix the two thoroughly to obtain an adsorbent A for treating dye and printing / dyeing wastewater. The activated carbon is obtained by pulverizing block activated carbon and passing it through an 80-mesh sieve; its specific surface area is 386 m². 2 / g; Cross-linked cationic starch is cross-linked cationic starch with a cationic substituent group of 3-trimethylamino-2-hydroxypropyl and a cationic substitution degree of 0.43; cross-linked cationic polyvinyl alcohol is cross-linked cationic polyvinyl alcohol with a cationic substituent group of 3-trimethylamino-2-hydroxypropyl and a cationic substitution degree of 0.26; The simulated dye wastewater used in the examples was prepared by Reactive Black 5 dye and deionized water, wherein the concentration of Reactive Black 5 dye was 500 mg / L; The simulated printing and dyeing wastewater used in the examples was prepared by Reactive Black 5 dye, corn starch, polyvinyl alcohol (PVA-1799) and deionized water, wherein the concentration of Reactive Black 5 dye was 500 mg / L, the concentration of corn starch was 100 mg / L, and the concentration of polyvinyl alcohol was 100 mg / L. (Adsorbent disclosed in Example 1 of CN108993429A)

[0069] Example 5

[0070] This embodiment provides a method for treating high-concentration COD biochemical effluent. Taking the treatment of dyeing and printing wastewater from a certain factory as an example, the method includes the following steps:

[0071] S-1. High-concentration COD biochemical effluent is passed through a container filled with adsorbent. The temperature inside the container in step S-1 is controlled at 60±2℃ and the pressure is controlled at 0.07–0.09 MPa to form a slightly negative pressure environment for adsorption and oxygenation treatment. The hydraulic retention time is 45 minutes.

[0072] S-2. The effluent from step S-1 is sent to an aerobic tank, where aerobic activated sludge is used for aerobic biological treatment. Simultaneously, commercially available compound Bacillus water purification agent is added to the aerobic tank (50 mg / L dry powder for initial startup, followed by weekly supplementation of 10–20 mg / L based on sludge activity). The aerobic biological treatment conditions are: water temperature 35±2℃, pH 7.2–7.8 (with automatic NaHCO3 addition for adjustment), and hydraulic retention time of 16 hours.

[0073] S-3. The effluent after step S-2 is subjected to deep filtration through a PVDF ultrafiltration membrane treatment device to obtain the treated effluent.

[0074] The adsorbent used in step S-1 is the same as the adsorbent used in the above embodiments and comparative examples.

[0075] The CODcr content of the effluent before and after aerobic biological treatment was measured, and the CODcr removal rate was calculated using the potassium dichromate method (GBT11914-89). The results are shown in Table 1.

[0076] Adsorbent CODcr (mg / L) of the treated effluent CODcr (mg / L) of the treated effluent CODcr removal rate (%) Example 1 980 46 95.3% Example 2 995 44 95.6% Example 3 976 65 93.3% Example 4 990 30 97.0% Comparative Example 0 996 462 53.6% Comparative Example 1 980 347 64.6% Comparative Example 2 985 395 59.9% Comparative Example 3 970 220 77.3% Comparative Example 4 976 269 72.4% Comparative Example 5 982 234 76.2%

[0077] As can be seen from Table 1, the CODcr removal rates of the biochemical effluent treated by the adsorbents provided in the embodiments of the present invention are quite ideal, reaching over 93% after aerobic biochemical treatment. In contrast, the CODcr removal rates of the adsorbents provided in Comparative Examples 1-5 are lower compared to the embodiments.

[0078] Specifically, Comparative Examples 4 and 5 used adsorbents from existing technologies, with CODcr removal rates of around 70%, significantly lower than the adsorbent of this invention. Comparative Example 1 directly used activated carbon as the adsorbent, achieving a CODcr removal rate of 53.6%.

[0079] Compared to Example 1, Comparative Example 1 did not perform steps S2 and S3, only nitrogen doping was performed, and the CODcr removal rate was only 64.6%. Compared to Example 1, Comparative Example 2 did not perform step S1, i.e., no nitrogen doping was performed, and the CODcr removal rate was only 59.9%. Compared to Example 1, Comparative Example 3 did not perform step S3, i.e., no nitrogen doping was performed, and the CODcr removal rate was only 77.3%, which is still significantly different from Example 1.

[0080] In summary, nitrogen doping is fundamental to improving the adsorption function of activated carbon. However, nitrogen doping alone does not significantly improve the CODcr removal rate compared to existing adsorbents. Without nitrogen doping or subsequent oxidation treatment, the improvement in CODcr removal rate is not substantial.

Claims

1. A method for preparing an adsorbent for high-concentration COD biochemical tail water treatment, characterized by, It comprises the following steps: S1. Activated carbon is subjected to nitrogen doping treatment to obtain nitrogen-doped activated carbon; S2. The nitrogen-doped activated carbon is subjected to oxidation treatment to obtain oxidation-nitrogen-doped activated carbon; S3. The oxidation-nitrogen-doped activated carbon is placed in an oxygen-rich, low-pressure condition for treatment to obtain an adsorbent.

2. The method for preparing an adsorbent for treating high-concentration COD biochemical tail water according to claim 1, characterized in that, The nitrogen doping treatment is that activated carbon is mixed with a nitrogen source reagent, anhydrous ethanol is added, magnetic stirring is performed, and heating reflux is performed in a constant temperature water bath for 3-20 h, followed by filtration, deionized water washing, drying, and calcination in a nitrogen protection environment.

3. The method for preparing the adsorbent for treating high-concentration COD biochemical tail water according to claim 1, characterized in that, The oxidation treatment is that nitrogen-doped activated carbon is subjected to high-temperature treatment in an ozone atmosphere, and the treatment temperature is 120-130°C.

4. The method for preparing the adsorbent for treating high-concentration COD biochemical tail water according to claim 1, characterized in that, In step S3, the low pressure refers to a pressure value of 0.1-0.5 atm.

5. The method for preparing the adsorbent for biochemical tail water treatment of high concentration COD according to claim 1, characterized in that, In step S3, the oxygen-rich refers to an oxygen concentration of more than 60%.

6. The method for preparing the adsorbent for treating high-concentration COD biochemical tail water according to claim 2, characterized in that, The constant temperature condition is 60-75°C.

7. A kind of adsorbent for high concentration COD biochemical tail water treatment, it is characterized in that, The preparation method is obtained by using any one of claims 1-6.

8. Use of the adsorbent according to claim 7, characterized in that, It is used for treating high-concentration COD biochemical tail water.

9. A method for treating high-concentration COD biochemical tail water, characterized in that, It comprises the following steps: S-1. High-concentration COD biochemical tail water is subjected to adsorption oxygen extraction treatment by passing through a container containing the adsorbent of claim 7; S-2. The tail water after step S-1 treatment is sent to an aerobic tank for aerobic biochemical treatment, and a microbial preparation is added to the aerobic tank; S-3. The tail water after step S-2 treatment is subjected to deep filtration treatment by a membrane treatment device to obtain treated tail water.

10. The method according to claim 9, wherein the COD concentration of the effluent is 1000 mg / L or more. The temperature in the container in step S-1 is controlled to be above 50°C and below 70°C, and the pressure is lower than one standard atmosphere.