Composite carbon source additive and preparation method thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a composite carbon source additive and a preparation method thereof. The composite carbon source additive comprises the following components in parts by weight: 30-40 parts of bagasse, 8-12 parts of a polyvinyl alcohol derivative, 2-4 parts of a functional filler, 5-8 parts of potassium citrate and 5-8 parts of sodium pyruvate, the preparation process of the polyvinyl alcohol derivative comprises the following steps: adding polyvinyl alcohol, 1, 3, 5-benzene trisulfonic acid, triethylamine and 4-dimethylaminopyridine into dichloromethane to react, filtering, washing and drying; the polyvinyl alcohol derivative is obtained. The composite carbon source additive can be slowly released in the denitrification process and continuously and stably provide a carbon source, the denitrification process is promoted, and the denitrification efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a composite carbon source additive and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization and urbanization, a large amount of nitrogen-containing pollutants enter water bodies through agricultural runoff, domestic sewage and industrial wastewater, resulting in a significant increase in the nitrogen content in water sources. The significant increase in the nitrogen content in water sources will promote the massive reproduction of algae such as cyanobacteria and green algae. The excessive growth of algae will reduce the dissolved oxygen in water bodies and produce toxins, ultimately leading to water quality deterioration and causing serious harm to aquatic organisms and human health. Nitrogen in sewage mainly exists in the forms of ammonia nitrogen, organic nitrogen, nitrite and nitrate. Biological denitrification is the process of converting nitrogen-containing pollutants into nitrogen gas and releasing it into the air; its basic principle includes three steps: ammonification is the conversion of organic nitrogen into ammonia nitrogen; nitrification is the conversion of ammonia nitrogen into nitrate; denitrification is the reduction of nitrate to nitrogen gas and release. During the denitrification process, sufficient carbon source is required to provide nutrients and energy for heterotrophic microorganisms to efficiently complete assimilation and dissimilation, so as to achieve the purpose of removing nitrogen-containing pollutants in sewage.

[0003] Denitrification is a key step in traditional nitrogen removal processes, but currently this process faces many challenges, such as insufficient carbon source, high energy consumption and possible secondary pollution problems. During the biochemical treatment of sewage, the carbon sources available for denitrifying bacteria mainly include the original carbon source in sewage and the added carbon source. Among them, the use of added carbon source is of great significance for improving denitrification efficiency. At present, common added carbon sources are methanol, acetic acid, etc. However, these traditional carbon sources have certain limitations in practical applications. On the one hand, they may not be able to achieve good denitrification effects on the premise of being non-toxic, harmless and environmentally friendly; on the other hand, their cost performance also needs to be improved.

[0004] Therefore, there is an urgent need for a composite carbon source additive that can promote the rapid progress of the denitrification reaction, improve the denitrification efficiency and reduce the treatment cost while meeting the requirements of green environmental protection. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, one of the purposes of the present invention is to provide a composite carbon source additive. The composite carbon source additive of the present invention can be quickly started and continuously and stably provide carbon source during denitrification, strengthen the denitrification effect and improve the denitrification efficiency.

[0006] One of the purposes of the present invention is achieved by adopting the following technical solutions:

[0007] A composite carbon source additive, by weight, comprises the following components: 30-40 parts of bagasse, 8-12 parts of polyvinyl alcohol derivative, 2-4 parts of functional filler, 5-8 parts of potassium citrate, and 5-8 parts of sodium pyruvate;

[0008] The preparation process of the polyvinyl alcohol derivative is as follows: polyvinyl alcohol, 1,3,5-benzenetrisulfonic acid, triethylamine, and 4-dimethylaminopyridine are added to dichloromethane for reaction, followed by filtration, washing, and drying to obtain the polyvinyl alcohol derivative.

[0009] Further, the mass ratio of polyvinyl alcohol, 1,3,5-benzenetrisulfonic acid, triethylamine, 4-dimethylaminopyridine, and dichloromethane is 1:(3-4):(3-3.5):(0.2-0.3):50.

[0010] Further, the reaction time is 8-12 h.

[0011] Further, the preparation process of the functional filler is as follows: sepiolite, 1-bromoheptane, sodium carbonate, and potassium iodide are added to dioxane, heated for reaction, followed by filtration, washing, and drying to obtain the functional filler.

[0012] Further, the mass ratio of sepiolite, 1-bromoheptane, sodium carbonate, potassium iodide, and dioxane is 3:(1-2):(2-4):(0.1-0.2):80.

[0013] Further, the temperature of the heating reaction is 90-100 °C, and the time is 3-5 h.

[0014] Further, the preparation process of the bagasse is as follows: the waste bagasse is dried to constant weight at 50 °C, added to a 2 wt% sodium hydroxide aqueous solution and soaked for 10-12 h, washed with water until neutral, and then dried to constant weight at 50 °C to obtain the bagasse.

[0015] Further, the dosage ratio of the waste bagasse to the sodium hydroxide aqueous solution is 0.05-0.10 g:1 mL.

[0016] The second object of the present invention is to provide a preparation method of the composite carbon source additive. The method is simple, efficient, and highly feasible.

[0017] The second object of the present invention is achieved by the following technical solution:

[0018] The preparation method of the above composite carbon source additive comprises the following steps: dispersing bagasse, functional filler, potassium citrate, and sodium pyruvate in water, then adding the polyvinyl alcohol derivative thereto, mixing evenly to obtain a mixture; performing 3 freeze-thaw cycles, and drying after the last thawing to obtain the product.

[0019] Further, the freeze-thaw cycle is as follows: freezing the mixture at -20°C to -15°C for 18 to 24 hours; then thawing at room temperature, which is recorded as 1 freeze-thaw cycle; the mass ratio of bagasse to water is (3 - 4):10.

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

[0021] 1. The present invention provides a composite carbon source additive, which is prepared by scientifically proportioning pretreated bagasse, polyvinyl alcohol derivative, functional filler, potassium citrate, and sodium pyruvate. The composite carbon source additive can slowly release and continuously and stably provide carbon source during the denitrification process, improving the sewage denitrification efficiency.

[0022] (1) The present invention introduces a polyvinyl alcohol derivative, which introduces a sulfonic acid group onto polyvinyl alcohol. It can not only provide more active sites for the carbon source, promote the utilization of the carbon source by microorganisms, and thus improve the efficiency of the denitrification process; but also avoid the rapid decomposition of the carbon source in water, so that the composite carbon source additive can slowly and stably release in water. (2) After introducing a hydrophobic aliphatic chain on the surface of sepiolite, a functional filler is obtained. Its surface hydrophobicity is enhanced, and it can better adsorb hydrophobic organic substances, such as the organic substances in bagasse (such as lignin and fatty acids), avoiding the rapid release of the carbon source at the initial stage of input, improving the release stability and bioavailability of the carbon source. At the same time, the modified sepiolite has a larger specific surface area and a more abundant pore structure, which can improve its adsorption capacity and the attachment ability to microorganisms, thereby promoting the denitrification process.

[0023] 2. The present invention provides a preparation method of the above composite carbon source additive. This method is simple, efficient, and feasible, and helps to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the infrared spectrum of the polyvinyl alcohol derivative obtained in Example 1 of the present invention;

[0025] Figure 2 It is the infrared spectrum of the functional filler obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] Next, in combination with the drawings and specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following described embodiments or technical features can be arbitrarily combined to form new embodiments. The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0027] Example 1

[0028] A composite carbon source additive, by weight, comprises the following components: 35 parts of bagasse, 10 parts of polyvinyl alcohol derivative, 3 parts of functional filler, 7 parts of potassium citrate, and 7 parts of sodium pyruvate;

[0029] The preparation process of the bagasse is as follows: The waste bagasse is dried to a constant weight at 50 °C, added to a 2 wt% sodium hydroxide aqueous solution and soaked for 11 h, with a solid-liquid ratio of 0.06 g / mL; after washing with water until neutral, it is dried to a constant weight at 50 °C to obtain the bagasse.

[0030] The preparation process of the polyvinyl alcohol derivative is as follows: 1 part of polyvinyl alcohol, 3.5 parts of 1,3,5-benzenetrisulfonic acid, 3.2 parts of triethylamine, and 0.25 part of 4-dimethylaminopyridine are added to 50 parts of dichloromethane, and the reaction is carried out at room temperature for 10 h, followed by filtration, washing with deionized water, and drying in an oven at 100 °C to obtain the polyvinyl alcohol derivative.

[0031] The preparation process of the functional filler is as follows: 3 parts of sepiolite, 1.5 parts of 1-bromoheptane, 3 parts of sodium carbonate, and 0.15 part of potassium iodide are added to 80 parts of dioxane, and the reaction is carried out at 100 °C for 4 h, followed by filtration, washing with deionized water, and drying in an oven at 100 °C to obtain the functional filler.

[0032] The preparation method of the above composite carbon source additive comprises the following steps: The bagasse, functional filler, potassium citrate, and sodium pyruvate are dispersed in water, where the mass ratio of bagasse to water is 3.5:10; then the polyvinyl alcohol derivative is added thereto and mixed evenly, and the mixture is frozen at -18 °C for 20 h; then it is thawed at room temperature, which is recorded as 1 freeze-thaw cycle; this cycle is repeated 3 times, and after the last thawing, it is dried to obtain the product.

[0033] Example 2

[0034] A composite carbon source additive, by weight, comprises the following components: 30 parts of bagasse, 8 parts of polyvinyl alcohol derivative, 2 parts of functional filler, 5 parts of potassium citrate, and 5 parts of sodium pyruvate;

[0035] The preparation process of the bagasse is as follows: The waste bagasse is dried to a constant weight at 50 °C, added to a 2 wt% sodium hydroxide aqueous solution and soaked for 10 h, with a solid-liquid ratio of 0.05 g / mL; after washing with water until neutral, it is dried to a constant weight at 50 °C to obtain the bagasse.

[0036] The preparation process of the polyvinyl alcohol derivative is as follows: 1 part of polyvinyl alcohol, 3 parts of 1,3,5-benzenetrisulfonic acid, 3 parts of triethylamine, and 0.2 part of 4-dimethylaminopyridine are added to 50 parts of dichloromethane, and the reaction is carried out at room temperature for 8 h, followed by filtration, washing with deionized water, and drying in an oven at 100 °C to obtain the polyvinyl alcohol derivative.

[0037] The preparation process of the functional filler is as follows: Add 3 parts of sepiolite, 1 part of 1-bromoheptane, 2 parts of sodium carbonate, and 0.1 part of potassium iodide to 80 parts of dioxane, react at 100 °C for 3 h, then filter, wash with deionized water, and dry in an oven at 100 °C to obtain the functional filler.

[0038] The preparation method of the above composite carbon source additive includes the following steps: Disperse bagasse, functional filler, potassium citrate, and sodium pyruvate in water, where the mass ratio of bagasse to water is 3:10; then add a polyvinyl alcohol derivative thereto, mix evenly, freeze the mixture at -20 °C for 18 h; then thaw at room temperature, which is recorded as 1 freeze-thaw cycle; repeat this cycle 3 times, and dry after the last thawing to obtain the product.

[0039] Example 3

[0040] A composite carbon source additive, by weight, includes the following components: 40 parts of bagasse, 12 parts of polyvinyl alcohol derivative, 4 parts of functional filler, 8 parts of potassium citrate, and 8 parts of sodium pyruvate;

[0041] The preparation process of the bagasse is as follows: Dry the waste bagasse at 50 °C to constant weight, add it to a 2 wt% aqueous sodium hydroxide solution and soak for 12 h, with a solid-liquid ratio of 0.10 g / mL; wash with water to neutrality and then dry at 50 °C to constant weight to obtain the bagasse.

[0042] The preparation process of the polyvinyl alcohol derivative is as follows: Add 1 part of polyvinyl alcohol, 4 parts of 1,3,5-benzenetri-sulfonic acid, 3.5 parts of triethylamine, and 0.3 part of 4-dimethylaminopyridine to 50 parts of dichloromethane, react at room temperature for 12 h, filter, wash with deionized water, and dry in an oven at 100 °C to obtain the polyvinyl alcohol derivative.

[0043] The preparation process of the functional filler is as follows: Add 3 parts of sepiolite, 2 parts of 1-bromoheptane, 4 parts of sodium carbonate, and 0.2 part of potassium iodide to 80 parts of dioxane, react at 100 °C for 5 h, then filter, wash with deionized water, and dry in an oven at 100 °C to obtain the functional filler.

[0044] The preparation method of the above composite carbon source additive includes the following steps: Disperse bagasse, functional filler, potassium citrate, and sodium pyruvate in water, where the mass ratio of bagasse to water is 4:10; then add a polyvinyl alcohol derivative thereto, mix evenly, freeze the mixture at -15 °C for 24 h; then thaw at room temperature, which is recorded as 1 freeze-thaw cycle; repeat this cycle 3 times, and dry after the last thawing to obtain the product.

[0045] Comparative Example 1

[0046] This comparative example is basically the same as Example 1, the difference being that the polyvinyl alcohol derivative is replaced by polyvinyl alcohol.

[0047] Comparative Example 2

[0048] This comparative example is basically the same as Example 1, except that the functional filler is replaced with sepiolite.

[0049] Test Example 1

[0050] Figure 1 and Figure 2 are the infrared spectra of the polyvinyl alcohol derivative and the functional filler obtained in Example 1, respectively.

[0051] It can be seen from Figure 1 that the peak shape at 3600 cm -1 has a slight change, which proves that some hydroxyl groups of polyvinyl alcohol are replaced by sulfonic acid groups; the absorption peak at 1170 cm -1 has a change, indicating the presence of sulfonate groups, and the absorption peaks at 750 - 860 cm -1 show the substitution characteristic peaks of the benzene ring, indicating that the polyvinyl alcohol derivative has been successfully prepared.

[0052] Figure 2 It can be seen that the characteristic peaks of methylene appear at 2915 - 2845 cm -1 indicating the successful compounding of 1-bromoheptane and sepiolite.

[0053] Test Example 2

[0054] In order to explore the carbon release ability of the composite carbon source additives obtained in Examples 1 - 3 and Comparative Examples 1 - 2, the following tests were carried out: The composite carbon source additives obtained in Examples 1 - 3 and Comparative Examples 1 - 2 were respectively put into 350 mL of deionized water, 9 g in each group, sealed and oscillated at 120 rpm at room temperature. Samples were taken at 12 h, 48 h, and 120 h respectively, and the COD cr concentration of each group of samples was measured. The results are shown in Table 1.

[0055] Table 1

[0056]

[0057] From the test results in Table 1, it can be seen that Examples 1 - 3 of the present invention can slowly and stably release carbon sources within 120 h. Compared with Example 1, in Comparative Example 1 (replacing the polyvinyl alcohol derivative with polyvinyl alcohol), the CODcr content is higher in the initial stage of release. This may be because the introduced polyvinyl alcohol derivative and the filler act together to prevent the carbon source from being rapidly decomposed at the initial stage of input, resulting in its excessive consumption.

[0058] In addition, compared with Example 1, the composite carbon source of Comparative Example 2 (where the functional filler was replaced with sepiolite) had a higher carbon release rate in the initial stage and a lower carbon release rate in the later stage. This indicates that the functional filler in the composite carbon source additive of the present invention can introduce hydrophobic aliphatic chains on the surface of sepiolite, which can better adsorb the carbon source in bagasse and also provide more carbon sources.

[0059] Test Example 3

[0060] To explore the denitrification ability of the composite carbon source additives obtained in Examples 1-3 and Comparative Examples 1-2, the following tests were conducted:

[0061] Take 200 mL of deionized water, add potassium nitrate and potassium dihydrogen phosphate (N:P = 5:1), and prepare a nitrate solution with a concentration of 30 mg / L to simulate wastewater. It was divided into groups of Examples 1-3 and Comparative Examples 1-2. In each group, 0.3 g of denitrifying bacteria and 10 g of the composite carbon source additive were added. After sealing, it was oscillated at 120 rpm and continuously cultured for 15 days, and the NO3 - -N removal rate and NO2 - -N removal rate were calculated, and the results are shown in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] From the test results in Table 2, it can be seen that Examples 1-3 of the present invention had a removal rate of NO3 - -N and NO2 - -N both higher than 90%. This indicates that the composite carbon source additive obtained in the present invention has good denitrification, because under anoxic conditions, denitrifying bacteria use the carbon source as an electron donor to reduce nitrate (NO3 - ) and nitrite (NO2 - ) to nitrogen gas (N2), thereby achieving nitrogen removal. In addition, the composite carbon source additive in the present invention can adjust the carbon-nitrogen ratio (C / N). The C / N ratios of many wastewaters are relatively low and are not sufficient to support the denitrification reaction. By adding an external carbon source, the C / N ratio in the wastewater can be increased, thereby promoting denitrification.

[0066] Comparative Examples 1 and 2 had poor removal rates of NO3 - -N and NO2 - -N, which indicates that polyvinyl alcohol derivatives and functional fillers can enhance the denitrification of the composite carbon source additive and improve the sewage treatment effect.

[0067] The above embodiments are only preferred embodiments of the present invention, and the scope of protection of the present invention cannot be limited thereby. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A composite carbon source additive, characterized in that, By weight parts, it includes the following components: 30-40 parts of bagasse, 8-12 parts of polyvinyl alcohol derivative, 2-4 parts of functional filler, 5-8 parts of potassium citrate, 5-8 parts of sodium pyruvate; The preparation process of the polyvinyl alcohol derivative is as follows: Add polyvinyl alcohol, 1,3,5-benzenetrisulfonic acid, triethylamine, 4-dimethylaminopyridine into dichloromethane for reaction, filter, wash, and dry to obtain the polyvinyl alcohol derivative.

2. The composite carbon source additive according to claim 1, characterized in that, The mass ratio of the polyvinyl alcohol, 1,3,5-benzenetrisulfonic acid, triethylamine, 4-dimethylaminopyridine, and dichloromethane is 1:(3-4):(3-3.5):(0.2-0.3):

50.

3. The composite carbon source additive according to claim 1, wherein The reaction time is 8-12 h.

4. The composite carbon source additive according to claim 1, wherein, The preparation process of the functional filler is as follows: Add sepiolite, 1-bromoheptane, sodium carbonate, potassium iodide into dioxane, heat and react, then filter, wash, and dry to obtain the functional filler.

5. The composite carbon source additive according to claim 4, wherein The mass ratio of the sepiolite, 1-bromoheptane, sodium carbonate, potassium iodide, and dioxane is 3:(1-2):(2-4):(0.1-0.2):

80.

6. The composite carbon source additive according to claim 4, wherein The temperature of the heating reaction is 90-100 °C, and the time is 3-5 h.

7. The composite carbon source additive according to claim 1, characterized in that, The preparation process of the bagasse is as follows: Dry the waste bagasse at 50 °C to constant weight, add it to a 2 wt% sodium hydroxide aqueous solution and soak for 10-12 h, wash with water until neutral, and then dry at 50 °C to constant weight to obtain the bagasse.

8. The composite carbon source additive according to claim 7, wherein The dosage ratio of the waste bagasse to the sodium hydroxide aqueous solution is 0.05-0.10 g:1 mL.

9. The preparation method of the composite carbon source additive according to any one of claims 1 to 8, characterized in that, It includes the following steps: Disperse the bagasse, functional filler, potassium citrate, and sodium pyruvate in water, then add the polyvinyl alcohol derivative thereto, mix evenly to obtain a mixture; perform 3 freeze-thaw cycles, and dry after the last thawing to obtain the product.

10. The preparation method of the composite carbon source additive according to claim 9, wherein The freeze-thaw cycle is as follows: Place the mixture at -20 °C to -15 °C and freeze for 18-24 h; then thaw at room temperature, which is recorded as 1 freeze-thaw cycle; the mass ratio of the bagasse to water is (3-4):10.

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