Biological filler for sewage treatment and method for its production

Abstract

This invention discloses a biological filler for wastewater treatment and its preparation method. The biological filler comprises the following raw materials by mass percentage: 65-85% polymer, 5-15% functional filler, 2-10% hydroxyapatite, 1-10% bagasse, and 2-10% iron(III) oxide. Compared with existing technologies, the biological filler prepared by this invention for wastewater treatment has the advantages of good hydrophilicity, good microbial biofilm formation, and good adsorption of pollutants.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a biological packing material for wastewater treatment and its preparation method. Background Technology

[0002] Biological packing material refers to a solid medium or carrier installed in a contact oxidation tank to provide a habitat and growth environment for microorganisms, while also immobilizing them. Therefore, biological packing material has the following functions: 1) providing a stable living environment for microbial growth and reproduction; 2) providing a place for microorganisms to fully contact and degrade pollutants with wastewater; 3) increasing the contact area between wastewater and biological packing material, improving pollutant removal efficiency; 4) significantly increasing biomass within the reactor and maintaining microbial activity. Biological packing material is part of the biological contact oxidation process. As a carrier for microbial growth and reproduction, it is one of the core technologies of membrane water treatment. Its material composition and surface properties directly affect the attachment, growth, reproduction, and activity of microorganisms on the packing surface, thus affecting microbial biofilm formation and wastewater degradation efficiency. Traditional plastic biological packing material often suffers from slow microbial biofilm formation, low biofilm activity, and low water treatment efficiency due to insufficient hydrophilicity and poor toxicity resistance, especially when treating high concentrations of toxic and recalcitrant substances. Currently, commonly used plastic biological packing materials lack sufficient biocompatibility, hydrophilicity, and activity, and the biological treatment efficiency of wastewater needs further improvement.

[0003] The invention patent with application number 200310105501.8 discloses a preparation process of a biological packing material for water treatment. The biological packing material is made from diatomaceous earth containing SiO2 and Al2O3 as raw material. After crushing, screening and high-temperature activation treatment, microbial growth promoters are introduced and modified. Finally, it is dried. The biological packing material has a good treatment effect on sewage, but its hydrophilicity and biofilm formation effect are not good.

[0004] Patent application number 201511004650.4 discloses a novel core-shell structured biological filler and its preparation method. The raw materials for preparing this biological filler include activated sludge, deodorizing bacteria, bamboo charcoal powder, iron oxide, calcium oxide, and silicate inorganic gel. The activated sludge, deodorizing bacteria, and 15-35% of the total silicate inorganic gel are mixed, extruded and granulated, then air-dried to obtain aggregate. The bamboo charcoal powder, iron oxide, calcium oxide, and the remaining silicate inorganic gel are mixed evenly to obtain powder. The aggregate is placed in a pelletizing disc, and while the disc rotates, the powder is sprinkled in and water is sprayed, causing the powder to gradually coat the surface of the aggregate, thus obtaining the initial-stage core-shell filler. After curing, the novel core-shell structured biological filler is obtained. It has the advantages of a short biological start-up cycle, strong acid-base buffering capacity, and fast biochemical reaction rate; however, this biological filler is not lightweight enough. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a biological packing material with good biofilm formation effect.

[0006] To achieve the above objectives, the present invention provides a biological packing material for wastewater treatment, comprising the following raw materials by mass percentage: 65-85% polymer, 5-15% functional packing material, 2-10% hydroxyapatite, 1-10% bagasse, and 2-10% iron(III) oxide.

[0007] The preparation method of the biological filler for sewage treatment is as follows: the polymer is heated and softened, and then functional fillers, hydroxyapatite, iron oxide, and bagasse are added. The mixture is stirred evenly at 300-500 rpm, and then extruded on a twin-screw injection molding machine according to conventional technical means to obtain the biological filler for sewage treatment.

[0008] Preferably, the polymer is a mixture of high-density polyethylene and modified polyvinyl chloride in a mass ratio of 1:0.5 to 1.5.

[0009] Preferably, the modified polyvinyl chloride is prepared by the following method, in parts by weight: Under a nitrogen atmosphere, polyvinyl chloride (PVC) was added to N,N-dimethylacetamide, followed by dimethylaminoethyl methacrylate, pentamethyldiethylenetriamine, and cuprous chloride. The mixture was stirred at 300-500 rpm for 20-45 minutes at -1 to 4°C under a nitrogen atmosphere, and then stirred at 300-500 rpm for 45-90 minutes at 60-70°C under a nitrogen atmosphere. Heating was then stopped, and the mixture was cooled to 15-30°C. Tetrahydrofuran was added for dilution chromatography, and the precipitate was obtained in a 45-55% ethanol aqueous solution. The mixture was then filtered to obtain modified PVC.

[0010] Preferably, the mass and volume ratio of the polyvinyl chloride to N,N-dimethylacetamide is 25~75g:500~1500mL.

[0011] Preferably, the mass ratio of polyvinyl chloride, dimethylaminoethyl methacrylate, pentamethyldiethylenetriamine, and cuprous chloride is 25~75:62.5~187.5:0.68~2.05:0.38~1.17.

[0012] Preferably, the preparation method of the functional filler is as follows: The filler was added to a 10-15 wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride and stirred at 300-500 rpm for 5-10 minutes. The pH was then adjusted to 1.98-2.01 with a 0.5-1.5 wt% aqueous solution of formic acid. Anhydrous sodium sulfate was then added, and the mixture was refluxed and stirred at 300-500 rpm at 25-35°C for 2-4 hours. Then, under a nitrogen atmosphere at 55-65°C, a 3.8-4.5 wt% aqueous solution of cerium ammonium nitrate was added dropwise at a rate of 0.3-0.8 mL / min. The mixture was then refluxed and stirred at 300-500 rpm at 55-65°C under a nitrogen atmosphere for 3-6 hours. The mixture was cooled to 15-30°C, filtered, and the solid was collected. The solid was washed with water until the filtrate was neutral. The solid was then vacuum dried at 55-70°C for 22-28 hours, ground, and passed through a 150-250 mesh sieve to obtain the functional filler.

[0013] Preferably, the filler comprises one or more of activated carbon, starch, fly ash, attapulgite, and oyster shell powder.

[0014] Preferably, the mass and volume ratio of the filler to the aqueous solution of methacryloyloxyethyltrimethylammonium chloride is 10~30g:250~750mL.

[0015] Preferably, the mass ratio of the filler to anhydrous sodium sulfate is 10~30: 1.2~3.6.

[0016] Preferably, the mass and volume ratio of the filler to the cerium ammonium nitrate aqueous solution is 0~30g:50~150mL.

[0017] Preferably, the above-mentioned filters are all 0.22~0.8 micron filter membranes.

[0018] Preferably, the biological packing material used for wastewater treatment can be of any shape.

[0019] This invention uses polyethylene and modified polyvinyl chloride (PVC) as polymer base materials, and adds functional fillers, hydroxyapatite, bagasse, and ferric oxide (Fe3O4), then mixes and extrudes to obtain a biological filler for wastewater treatment. The resulting biological filler exhibits good hydrophilicity and excellent microbial biofilm formation. Modified PVC is prepared by grafting dimethylaminoethyl methacrylate (DMME) onto the PVC backbone via atom transfer radical polymerization. DMME improves the hydrophilicity and biocompatibility of the modified PVC. The functional filler is prepared by in-situ synthesis of polymethacryloyloxyethyltrimethylammonium chloride on the filler, which enhances microbial biofilm formation and improves the adsorption of pollutants by the biological filler, thereby increasing the treatment efficiency of the microorganisms. During the extrusion molding process, the addition of bagasse provides an internal framework for the polymer, improving the mechanical properties of the biological filler.

[0020] Compared with the prior art, this invention has the following advantages due to the adoption of the above technical methods: 1) Grafting dimethylaminoethyl methacrylate onto the polyvinyl chloride main chain improves the hydrophilicity and biocompatibility of the modified polyvinyl chloride, and at the same time improves the biofilm formation effect; 2) Modifying the packing material with polymethacryloyloxyethyltrimethylammonium chloride improves the biofilm formation effect of microorganisms, and at the same time improves the adsorption of pollutants by the biological packing material and the treatment efficiency of pollutants by microorganisms; 3) The addition of bagasse improves the mechanical properties of the biological packing material. Detailed Implementation

[0021] Raw material sources for the examples and comparative examples: High-density polyethylene: Suzhou Feikai Plastics Co., Ltd., Item No.: DMDB-8902.

[0022] Polyvinyl chloride: Dongguan Baida Plastic Raw Materials Co., Ltd., Item No.: MP7151.

[0023] Activated carbon: Xiamen Tongke Activated Carbon Co., Ltd., particle size: 200 mesh.

[0024] Example 1 A method for preparing a biological packing material for wastewater treatment is as follows: Mix 35g of high-density polyethylene and 40g of modified polyvinyl chloride, heat to soften, then add 10g of functional filler, 5g of hydroxyapatite, 5g of bagasse, and 5g of ferric oxide. Stir evenly at 400 rpm, and then extrude on a twin-screw injection molding machine according to conventional technology to obtain biological filler for sewage treatment.

[0025] The modified polyvinyl chloride is prepared as follows: Under a nitrogen atmosphere, 50 g of polyvinyl chloride was added to 1000 mL of N,N-dimethylacetamide, followed by 125 g of dimethylaminoethyl methacrylate, 1.36 g of pentamethyldiethylenetriamine, and 0.775 g of cuprous chloride. The mixture was stirred at 400 rpm for 30 minutes at 2 °C under a nitrogen atmosphere, and then stirred at 400 rpm for another 60 minutes at 65 °C under a nitrogen atmosphere. Heating was stopped, and the mixture was cooled to 25 °C. Tetrahydrofuran was then added for dilution chromatography, and the precipitate was obtained in a 50% aqueous ethanol solution. The precipitate was filtered through a 0.45 μm filter membrane to obtain modified polyvinyl chloride.

[0026] The preparation method of the functional filler is as follows: 20g of activated carbon was added to 500mL of a 12wt% aqueous solution of methacryloyloxyethyltrimethylammonium chloride and stirred at 400 rpm for 8 minutes. The pH was then adjusted to 2 with a 1.1vt% aqueous solution of formic acid. 2.4g of anhydrous sodium sulfate was added, and the mixture was refluxed at 400 rpm for 3 hours at 30℃. Then, under a nitrogen atmosphere at 60℃, 100mL of a 4wt% aqueous solution of cerium ammonium nitrate was added dropwise at a rate of 0.5mL / min. The mixture was refluxed at 400 rpm for 4 hours under a nitrogen atmosphere at 60℃. After cooling to 25℃, the mixture was filtered through a 0.45-micron filter membrane, and the solid was collected. The solid was washed with water until the filtrate was neutral. The solid was then vacuum dried at 60℃ for 24 hours, ground, and passed through a 200-mesh sieve to obtain the functional filler.

[0027] Comparative Example 1 A method for preparing a biological packing material for wastewater treatment is as follows; 75g of high-density polyethylene was heated and softened, then 10g of functional filler, 5g of hydroxyapatite, 5g of bagasse, and 5g of ferric oxide were added. The mixture was stirred evenly at 400 rpm and then extruded on a twin-screw injection molding machine using conventional techniques to obtain a biological filler for wastewater treatment.

[0028] The preparation method of the functional filler is the same as that in Example 1.

[0029] Comparative Example 2 A method for preparing a biological packing material for wastewater treatment is as follows: Mix 35g of high-density polyethylene and 40g of modified polyvinyl chloride, heat to soften, then add 10g of activated carbon, 5g of hydroxyapatite, 5g of bagasse, and 5g of iron oxide. Stir evenly at 400 rpm, and then extrude into shape on a twin-screw injection molding machine using conventional techniques to obtain a biological packing material for sewage treatment.

[0030] The preparation method of the modified polyvinyl chloride is the same as that in Example 1.

[0031] Comparative Example 3 A method for preparing a biological packing material for wastewater treatment is as follows: Mix 35g of high-density polyethylene and 40g of modified polyvinyl chloride, heat to soften, then add 10g of functional filler, 5g of hydroxyapatite and 5g of iron oxide, stir evenly at 400 rpm, and then extrude on a twin-screw injection molding machine according to conventional technology to obtain biological filler for sewage treatment.

[0032] The preparation methods for the modified polyvinyl chloride and the functional fillers are the same as in Example 1.

[0033] Test Example 1 Hydrophilicity test: The surface hydrophilicity of the biological packing material prepared in this invention was tested using the lying drop method. The test method was as follows: 1 μL of pure water was dropped onto the surface of the biological packing material, and the contact angle was measured by a contact angle meter. After 2 minutes, the contact angle was measured again. Five parallel tests were performed for each sample, and the average value was taken. The test results are shown in Table 1.

[0034] Table 1 Contact Angle Test Results Example 1 35 23 Comparative Example 1 41 30 Comparative Example 2 39 27 Comparative Example 3 36 24 (Note: The smaller the contact angle, the better the hydrophilicity.) A comparison of Example 1 with Comparative Examples 1-3 reveals that Example 1 exhibits better hydrophilicity. This is likely because the dimethylaminoethyl methacrylate grafted onto the polyvinyl chloride backbone in Example 1 enhances the hydrophilicity of the modified polyvinyl chloride. Furthermore, the modification of the filler with polymethacryloyloxyethyltrimethylammonium chloride also improves its hydrophilicity.

[0035] Test Example 2 Biofilm quantity test: First, a biofilm was formed on the biological packing material. The steps are as follows: Add 20L of nutrient solution (a mixture of 6.3g glucose, 2.52g sodium acetate, 0.945g ammonium chloride, 0.21g disodium hydrogen phosphate, 0.015g ferrous sulfate heptahydrate, 0.252g calcium chloride, 0.273g magnesium sulfate, and 21L water) to 1L of activated sludge in the sludge return tank of a wastewater treatment plant. Mix thoroughly to obtain the biofilm forming medium. Aerate at 1L / min for 2 days. Place the prepared biological packing material into the aerated biofilm forming medium, with the biological packing material occupying 20% ​​of the biofilm forming medium volume. Continue aeration for 15 days. Filter out the biological material and wash twice with 0.88wt% physiological saline to obtain the biofilm-formed biological packing material. Refer to the journal article (Preparation and Application of Modified Polypropylene Biological Packing Material, Author: Haijing) for further details. (Chemical and Environmental Protection, 2006) The biofilm content of the biological packing material prepared by this invention was tested. The test method is as follows: Before biofilm formation, the biological packing material prepared by this invention was dried at 105℃ to constant weight. After cooling, the mass of the biological packing material before biofilm formation was recorded as m0 (g). The prepared biological packing material containing biofilm was dried at 105℃ to constant weight. After cooling, it was weighed and recorded as m1 (g). Then, the dried packing material was taken out from the weighing bottle and immersed in a 1 mol / L sodium hydroxide aqueous solution. It was stirred at 70℃ at 400 rpm for 60 minutes, then sonicated for 60 minutes with an ultrasonic power of 50W. It was washed with water until the detached biofilm was washed away. It was dried at 105℃ to constant weight. After cooling, it was weighed and recorded as m2 (g). The dry weight of biofilm on a unit mass of packing material was calculated using Equation 1. The results are shown in Table 2.

[0036] Biofilm mass on a unit mass of packing material (g / g) = (m1-m2) / m0 Equation 1 Test Example 3 Impact toughness test: The impact toughness of the polymer biofilm carrier prepared in this invention was tested in accordance with the People's Republic of China National Standard GB / T2567-2021 "Test Methods for Performance of Resin Castings". The biofiller was a standard V-notch specimen with a size of 80mm×10mm×4mm. Five parallel samples were made for each specimen, and the average value was taken. The results are shown in Table 2.

[0037] Table 2 Results of biomodulus test Example 1 0.36 11.1 Comparative Example 1 0.24 9.3 Comparative Example 2 0.32 9.5 Comparative Example 3 0.33 7.9 (Note: The greater the biofilm, the better the biofilm formation effect.) A comparison of Example 1 with Comparative Examples 1-3 reveals that Example 1 exhibits superior biofilm formation and impact toughness compared to Comparative Examples 1-3. This may be because grafting dimethylaminoethyl methacrylate onto the polyvinyl chloride backbone in Example 1 enhances the hydrophilicity and biocompatibility of the modified polyvinyl chloride, thereby improving the biofilm formation effect of microorganisms. Furthermore, the modification of the filler using polymethacryloyloxyethyltrimethylammonium chloride further enhances the biofilm formation effect. Additionally, the addition of bagasse during extrusion molding provides an internal framework for the polymer, further improving the impact toughness of the biological filler.

[0038] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A biological packing material for wastewater treatment, characterized in that, The raw materials include the following percentages by weight: 65-85% polymer, 5-15% functional filler, 2-10% hydroxyapatite, 1-10% bagasse, and 2-10% iron oxide; The polymer is a mixture of high-density polyethylene and modified polyvinyl chloride in a mass ratio of 1:0.5~1.5; The modified polyvinyl chloride is prepared as follows: Under a nitrogen atmosphere, polyvinyl chloride (PVC) was added to N,N-dimethylacetamide, followed by dimethylaminoethyl methacrylate, pentamethyldiethylenetriamine, and cuprous chloride. The mixture was stirred at -1 to 4°C under a nitrogen atmosphere for 20 to 45 minutes, then stirred again at 60 to 70°C under a nitrogen atmosphere for 45 to 90 minutes. Heating was stopped, the mixture was cooled, and tetrahydrofuran was added for dilution chromatography. The precipitate was collected in an ethanol-water solution and filtered to obtain modified PVC. The mass-to-volume ratio of PVC to N,N-dimethylacetamide was 25 to 75 g: 500 to 1500 mL. The mass ratio of PVC, dimethylaminoethyl methacrylate, pentamethyldiethylenetriamine, and cuprous chloride was 25 to 75: 62.5 to 187.5: 0.68 to 2.05: 0.38 to 1.

17. The preparation method of the functional filler is as follows: The filler was added to an aqueous solution of methacryloyloxyethyltrimethylammonium chloride and stirred. The pH was then adjusted to 1.98-2.01 with formic acid solution. Anhydrous sodium sulfate was added, and the mixture was refluxed and stirred at 25-35°C for 2-4 hours. Then, under a nitrogen atmosphere at 55-65°C, an aqueous solution of cerium ammonium nitrate was added dropwise. The mixture was refluxed and stirred under a nitrogen atmosphere at 55-65°C for 3-6 hours. After cooling, the mixture was filtered, and the solid was collected. The solid was washed with water until the filtrate was neutral, dried, ground, and passed through a 150-250 mesh sieve to obtain the functional filler. The mass-to-volume ratio of the filler to the aqueous solution of methacryloyloxyethyltrimethylammonium chloride was 10-30 g: 250-750 mL; the mass ratio of the filler to anhydrous sodium sulfate was 10-30: 1.2-3.6; and the mass-to-volume ratio of the filler to the aqueous solution of cerium ammonium nitrate was 0-30 g: 50-150 mL. The filler is activated carbon; The concentration of the aqueous solution of methacryloyloxyethyltrimethylammonium chloride is 12 wt%. The concentration of the cerium ammonium nitrate aqueous solution is 4 wt%.

2. The method for preparing biological packing material for wastewater treatment as described in claim 1, characterized in that, The process includes the following steps: heating and softening the polymer, then adding functional fillers, hydroxyapatite, ferric oxide, and bagasse, stirring evenly, and then extruding the mixture on a twin-screw injection molding machine using conventional techniques to obtain a biological filler for wastewater treatment.