A method for preparing modified polyurethane filler

Abstract

This invention relates to the field of polymer carrier modification technology, and more particularly to a method for preparing modified polyurethane filler. The invention involves mixing a peroxide solution and a ferrous salt solution, adjusting the pH to obtain a mixed solution, and then immersing the polyurethane filler in the mixed solution for modification, ultimately obtaining the modified polyurethane filler. The novel polyurethane filler obtained by the modification method described in this invention exhibits significantly improved biocompatibility and a larger specific surface area compared to traditional polyurethane fillers. This promotes the adsorption and growth of microorganisms on the filler surface, forming a biofilm, and thus improves its efficiency in wastewater treatment using biofilm methods.

Description

Technical Field

[0001] This invention relates to the field of polymer carrier modification technology, and in particular to a method for preparing a modified polyurethane filler. Background Technology

[0002] Biofilm technology is a wastewater treatment technique that utilizes microorganisms growing on a carrier material for biological wastewater treatment. The main function of the carrier material is to provide a microenvironment for microbial survival, greatly enhancing their resistance to various pollutants. Compared to other similar materials, polyurethane fillers have a large specific surface area, enabling them to maintain a sufficient number of microorganisms while achieving good separation from water. However, its microbial immobilization is achieved solely through physical adsorption, leading to easy detachment of microbial cells. Therefore, modification treatment is necessary to increase its surface roughness and improve its biocompatibility.

[0003] Currently, filler modification includes bulk modification and surface modification. Bulk modification of polyurethane fillers mostly involves adding nanomaterials such as nano-SiO2, which can improve the filler's affinity for microorganisms and physicochemical stability. However, these methods are expensive and difficult to obtain, limiting their widespread application. Surface modification includes mechanical modification, suitable for fillers with metal coatings, and surface roughening methods, which require processing the filler in a mold and are not suitable for polyurethane fillers. Low-temperature plasma modification and high-energy radiation modification have low environmental pollution and short processing cycles, but their application conditions are relatively harsh, making them unsuitable for widespread application. Currently, the most widely used methods are liquid-phase chemical oxidation and surface grafting. The latter mainly uses sodium alginate and gelatin protein for grafting. After chemical oxidation, the material surface becomes rough. Many studies have added ion coating or surface grafting after oxidation to enhance the modification effect. For example, potassium permanganate oxidation-iron ion coating modification and potassium permanganate oxidation-gelatin protein grafting modification have shown that gelatin protein grafting modification after oxidation is more effective than Fe... 3+ Covering modification is slightly more effective, but Fe 3+ The modification process is less expensive.

[0004] Therefore, how to provide a low-pollution, convenient, and lower-cost modification method to modify the biocompatibility of polyurethane fillers, thereby accelerating the biofilm formation on the surface of polyurethane fillers and enhancing the stability of the biofilm and the filler, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing modified polyurethane fillers, which modifies the biocompatibility of polyurethane fillers, thereby accelerating the biofilm formation of microorganisms on the surface of polyurethane fillers and enhancing the stability of biofilms and fillers, thus solving the problems of long biofilm formation time and easy biofilm detachment in polyurethane fillers.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing modified polyurethane fillers, comprising the following steps:

[0008] (1) Mix the peroxide solution and the ferrous salt solution, and adjust the pH to obtain a mixed solution;

[0009] (2) The polyurethane filler is immersed in a mixed solution for modification to obtain the modified polyurethane filler.

[0010] Preferably, in step (1), a sodium hydroxide solution, a hydrochloric acid solution, or a sulfuric acid solution is used to adjust the pH; the concentration of the sodium hydroxide solution is 0.1–0.5 mol / L; the concentration of the hydrochloric acid solution is 0.1–0.5 mol / L; the concentration of the sulfuric acid solution is 0.1–0.5 mol / L; and the pH of the mixed solution is ≤3.

[0011] Preferably, the concentration of peroxide in the mixed solution of step (1) is 0.1 to 10 mmol / L.

[0012] Preferably, the concentration of ferrous salt in the mixed solution of step (1) is 0.1 to 10 mmol / L.

[0013] Preferably, the peroxide solution in step (1) comprises hydrogen peroxide solution, peracetic acid solution, or sodium persulfate solution.

[0014] Preferably, the ferrous salt solution in step (1) includes one or more of ferrous sulfate solution and ferrous chloride solution.

[0015] Preferably, the modification temperature in step (2) is 15-25°C and the time is 1-4 hours.

[0016] Preferably, after the modification in step (2) is completed, the material is dried to obtain the modified polyurethane filler; the drying temperature is 100-120℃ and the drying time is 40-60min.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention provides a modification method for polyurethane fillers, applicable to aquatic biological treatment, which utilizes hydroxyl radicals and iron ions generated during an advanced oxidation reaction with ferrous ions as catalysts and peroxides as oxidants to modify polyurethane fillers. This method is characterized by low pollution, convenience, rapid reaction, and good modification effect.

[0019] The present invention provides a method for modifying the surface structure of polyurethane fillers. By using hydroxyl radicals generated during the advanced oxidation reaction to oxidize the filler surface, the surface roughness of the filler is increased, thereby increasing the specific surface area of ​​the filler. Since the surface of microbial cell membranes is mostly negatively charged, the iron ions generated by the reaction are used to modify the filler surface, thereby changing the surface potential of the filler and improving the biocompatibility of the filler, which is beneficial to the enrichment and immobilization of microorganisms.

[0020] The polyurethane packing material prepared by the modification method of the present invention has a larger specific surface area than traditional polyurethane packing materials. It promotes the adsorption and growth of microorganisms on the packing surface to form a biofilm and can be applied to the biofilm method to improve the treatment efficiency of wastewater. Attached Figure Description

[0021] Figure 1 This is a graph showing the change in biofilm loading over time before and after modification of the polyurethane filler in Example 1 of the present invention.

[0022] Figure 2 This is a graph showing the change in ammonia nitrogen removal rate over time before and after modification of the polyurethane filler in Example 1 of the present invention.

[0023] Figure 3 This is a graph showing the change in COD removal rate over time before and after modification of the polyurethane filler in Example 1 of the present invention. Detailed Implementation

[0024] This invention provides a method for preparing modified polyurethane fillers, comprising the following steps:

[0025] (1) Mix the peroxide solution and the ferrous salt solution, and adjust the pH to obtain a mixed solution;

[0026] (2) The polyurethane filler is immersed in a mixed solution for modification to obtain the modified polyurethane filler.

[0027] In this invention, in step (1), sodium hydroxide solution, hydrochloric acid solution or sulfuric acid solution is used to adjust the pH, preferably hydrochloric acid solution or sulfuric acid solution is used to adjust the pH;

[0028] The concentration of the sodium hydroxide solution is 0.1–0.5 mol / L, preferably 0.2–0.4 mol / L, and more preferably 0.25–0.35 mol / L; the concentration of the hydrochloric acid solution is 0.1–0.5 mol / L, preferably 0.2–0.4 mol / L, and more preferably 0.25–0.35 mol / L; the concentration of the sulfuric acid solution is 0.1–0.5 mol / L, preferably 0.2–0.4 mol / L, and more preferably 0.25–0.35 mol / L.

[0029] The pH of the mixed solution is ≤3, preferably ≤2.5, more preferably ≤2, and even more preferably ≤1.5.

[0030] In this invention, the concentration of peroxide in the mixed solution of step (1) is 0.1-10 mmol / L, preferably 1-8 mmol / L, more preferably 2-6 mmol / L, and even more preferably 4-5 mmol / L.

[0031] In this invention, the concentration of ferrous salt in the mixed solution of step (1) is 0.1-10 mmol / L, preferably 1-8 mmol / L, more preferably 2-6 mmol / L, and even more preferably 4-5 mmol / L.

[0032] In this invention, the concentration of peroxide solution and ferrous ions in the mixed solution in step (1) are equal.

[0033] In this invention, the peroxide solution in step (1) includes hydrogen peroxide solution, peracetic acid solution or sodium persulfate solution, preferably hydrogen peroxide solution or peracetic acid solution, and more preferably peracetic acid solution.

[0034] In this invention, the ferrous salt solution in step (1) includes one or more of ferrous sulfate solution and ferrous chloride solution, preferably ferrous sulfate solution.

[0035] In this invention, the modification temperature in step (2) is 15-25°C, preferably 16-24°C, more preferably 18-22°C, and even more preferably 20°C; the time is 1-4h, preferably 1.5-3.5h, more preferably 2-3h, and even more preferably 2.5h.

[0036] In this invention, after the modification in step (2) is completed, the product is dried to obtain the modified polyurethane filler; the drying temperature is 100-120℃, preferably 102-115℃, and more preferably 105-110℃; the drying time is 40-60 min, preferably 45-55℃, more preferably 48-53℃, and even more preferably 50℃.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] Peracetic acid solution and ferrous sulfate solution were mixed, and the pH of the resulting mixed solution was adjusted to 3 using 0.1 mol / L H2SO4 solution. The concentrations of peracetic acid and ferrous sulfate in the mixed solution were 1.0 mmol / L and 1.0 mmol / L, respectively. The polyurethane filler was completely immersed in the mixed solution at 20°C for 2 hours for modification. After modification, the filler was dried at 105°C for 60 minutes to obtain the modified polyurethane filler.

[0040] Example 2

[0041] Peracetic acid solution and ferrous sulfate solution were mixed, and the pH of the resulting mixed solution was adjusted to 3 using 0.1 mol / L H2SO4 solution. The concentrations of peracetic acid and ferrous sulfate in the mixed solution were 0.1 mmol / L and 0.1 mmol / L, respectively. The polyurethane filler was completely immersed in the mixed solution at 20°C for 1 hour for modification. After modification, the filler was dried at 105°C for 60 minutes to obtain the modified polyurethane filler.

[0042] Example 3

[0043] Peracetic acid solution and ferrous sulfate solution were mixed, and the pH of the resulting mixed solution was adjusted to 3 using 0.1 mol / L H2SO4 solution. The concentrations of peracetic acid and ferrous sulfate in the mixed solution were 10 mmol / L. The polyurethane filler was completely immersed in the mixed solution at 20°C for 4 hours for modification. After modification, the filler was dried at 105°C for 60 minutes to obtain the modified polyurethane filler.

[0044] Test case

[0045] Experimental methods:

[0046] Artificial water was prepared using glucose as the carbon source and ammonium bicarbonate as the nitrogen source, with a COD of 340 mg / L and an ammonia nitrogen concentration of 22 mg / L. The modified packing material prepared in Example 1 and the unmodified packing material were respectively loaded into two identical reactors (effective volume 1 L) at a packing / solution filling ratio (packing volume / solution volume) of 5%.

[0047] Biofilm formation stage: Inoculate equal amounts of sludge from the aeration tank of the wastewater treatment plant, aerate and mix thoroughly, then let stand for 24 hours. After 24 hours, remove the sludge, completing the inoculation process. Re-add water and aerate, controlling dissolved oxygen at 6-8 mg / L. Change the water every 24 hours. The biofilm formation stage ends after 3 days.

[0048] Sampling Phase: After biofilm formation, a wastewater treatment performance test was conducted using the packing material. Dissolved oxygen was controlled at 6–8 mg / L, with an operating cycle of 24 hours, including 23 hours of aeration, 50 minutes of settling, and 10 minutes of water exchange. At the end of each operating cycle, the COD and ammonia nitrogen values ​​of the effluent from both reactors were measured during water exchange. Simultaneously, modified and unmodified packing materials were taken for testing the biofilm quantity.

[0049] Analysis method:

[0050] (1) Biofilm quantity test method: The removed biofilm packing material (packing material weight W1, g) was placed in a weighing bottle lined with tin foil and dried in an oven at 105℃ for 60 min. After cooling, it was weighed (W2, g). The packing material was removed and placed in a 1 mol / L NaOH solution. It was heated in a water bath at 70℃ for 1 h, and then treated with 40 Hz ultrasound for 1 h. After washing with water several times until the detached biofilm was washed away, the packing material was put back into the weighing bottle for drying, cooling, and weighing (W3, g). The dry weight of the biofilm on the unit mass of packing material (mg / g) was calculated as (W2-W3)*1000 / W1.

[0051] (2) COD removal rate test method: The COD of the influent and effluent is measured by the potassium dichromate method. The COD removal rate is obtained by dividing the COD removal amount by the COD of the influent.

[0052] (3) Test method for ammonia nitrogen removal rate: The ammonia nitrogen in the influent and effluent is measured by Nessler's reagent photometric method. The ammonia nitrogen removal rate is obtained by dividing the amount of ammonia nitrogen removed by the amount of ammonia nitrogen in the influent.

[0053] Table 1. Comparison of biomodulus, COD removal rate, and ammonia nitrogen removal rate within 6 days before and after polyurethane filler modification in Example 1.

[0054] Comparison items Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Biofilm content of modified filler (mg / g) 39.45 60.90 83.85 104.40 127.05 189.50 Biofilm content of unmodified filler (mg / g) 25.20 40.65 47.55 63.00 80.10 148.05 COD removal rate (%) of modified packing 53.96 56.64 60.97 67.84 81.21 86.19 COD removal rate (%) of unmodified packing material 22.26 26.32 31.7 38.33 41.4 48.46 Ammonia nitrogen removal rate (%) of modified packing material 52.42 55.91 61.64 69.33 73.42 84.8 Ammonia nitrogen removal rate (%) of unmodified packing material 21.08 26.13 32.72 38.74 45.5 60.81

[0055] According to the present invention Figure 1 As shown in Table 1, the biofilm amount and growth rate of the modified packing were higher than those of the unmodified packing. On the 6th day of measurement, the biofilm amount per 1g of modified packing was 189.50mg and that of the unmodified packing was 148.05mg, respectively; the average daily growth of the biofilm per 1g of modified packing was 31.6mg / d and that of the unmodified packing was 24.7mg / d, respectively. The average daily growth of the biofilm in the modified packing increased by 28.0%, and the biofilm growth rate was higher.

[0056] According to the present invention Figure 2 As shown in Table 1, the modified packing material has a significantly better effect on ammonia nitrogen treatment in wastewater than the unmodified packing material. The modified packing material has an ammonia nitrogen removal rate of 84.8%, while the unmodified packing material has an ammonia nitrogen removal rate of only 60.81%.

[0057] According to the present invention Figure 3As shown in Table 1, the modified packing material has a significantly better COD removal effect on wastewater than the unmodified packing material. The modified packing material has a COD removal rate of 86.19%, while the COD removal rate of the unmodified packing material is only 48.46%.

[0058] The differences in the removal efficiency of the two types of packing materials for COD and ammonia nitrogen in wastewater can be attributed to several factors, including... Figure 1 The significant difference in biofilm quantity between the two is also related to the Fe2O3 coating on the surface of the modified filler. Its weak magnetic field effect can promote microbial life activities, and at the same time, it can also promote intracellular enzymatic reactions and accelerate the flow of nutrients in the cell water.

[0059] As can be seen from the above embodiments, the present invention provides a modification method for polyurethane packing material applicable to aquatic biological treatment, which utilizes hydroxyl radicals and iron ions generated during an advanced oxidation reaction with ferrous ions as a catalyst and peroxide as an oxidant to modify the packing material. The novel packing material prepared using the modification method of the present invention has a larger specific surface area than traditional polyurethane packing material, promoting the adsorption and growth of microorganisms on the packing surface to form a biofilm. It can be applied in biofilm methods to improve wastewater treatment efficiency.

[0060] 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 principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified polyurethane filler, characterized in that, Includes the following steps: (1) Mix the peroxide solution and the ferrous salt solution, and adjust the pH to obtain a mixed solution; (2) The polyurethane filler is immersed in a mixed solution for modification to obtain the modified polyurethane filler; The pH of the mixed solution is ≤3; The concentration of peroxide in the mixed solution of step (1) is 0.1~10 mmol / L; The concentration of ferrous salt in the mixed solution of step (1) is 0.1~10 mmol / L; In step (1), the concentrations of peroxide and ferrous ions in the mixed solution are equal; The peroxide solution in step (1) includes hydrogen peroxide solution, peracetic acid solution or sodium persulfate solution.

2. The method for preparing a modified polyurethane filler according to claim 1, characterized in that, In step (1), the pH is adjusted using sodium hydroxide solution, hydrochloric acid solution or sulfuric acid solution; the concentration of the sodium hydroxide solution is 0.1~0.5 mol / L; the concentration of the hydrochloric acid solution is 0.1~0.5 mol / L; the concentration of the sulfuric acid solution is 0.1~0.5 mol / L.

3. The method for preparing a modified polyurethane filler according to claim 1, characterized in that, The ferrous salt solution in step (1) includes one or more of ferrous sulfate solution and ferrous chloride solution.

4. A method for preparing a modified polyurethane filler according to claim 1, 2, or 3, characterized in that, The modification temperature in step (2) is 15~25℃ and the time is 1~4h.

5. The method for preparing a modified polyurethane filler according to claim 4, characterized in that, After the modification in step (2) is completed, the modified polyurethane filler is dried to obtain the modified polyurethane filler; the drying temperature is 100~120℃ and the time is 40~60min.

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