Biodegradation-photocatalysis composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and discloses a biodegradable-photocatalytic composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a photocatalyst, sodium alginate and water to obtain gel containing the photocatalyst, then adding a photosynthetic bacteria concentrated solution, then adsorbing photosynthetic bacteria and the photocatalyst by using a carrier, and finally immobilizing in a calcium chloride solution to obtain the composite material. Photosynthetic bacteria are selected as microorganisms, and the method has the advantages of being flexible in metabolism mode, high in antibiotic tolerance, high in breeding speed, free of sludge treatment and the like. The photocatalyst and the photosynthetic bacteria are loaded on the polyurethane sponge, so that the photosynthetic bacteria are easily separated from water while being protected. The photocatalyst outside the carrier generates high-activity substances, and refractory antibiotics are converted into biodegradable intermediates. And a generated intermediate product is decomposed by microorganisms in the carrier, so that efficient degradation and mineralization of antibiotics in the sewage are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a biodegradation-photocatalysis composite material, a preparation method thereof and an application thereof. Background Art

[0002] Since the advent of penicillin in the 20th century, antibiotics have been widely used in the treatment of human diseases, animal husbandry and aquaculture. Antibiotics are mainly classified into sulfonamides, tetracyclines, β-lactams, quinolones, macrolides, chloramphenicols, lincomycins and other types of antibiotics according to their structural characteristics. The sources of antibiotics detected in the water environment at home and abroad are mainly: wastewater from antibiotic pharmaceutical enterprises, hospital sewage, sewage from aquaculture farms and livestock farms, etc. The medical antibiotics and veterinary antibiotics that enter the human body and animals cannot be completely decomposed and utilized, and most of them are directly discharged into the environment through feces and urine or enter the sewage treatment plant. Antibiotics have a strong inhibitory effect on the growth of microorganisms in wastewater biochemical treatment. Therefore, the current sewage treatment process cannot completely remove antibiotics, resulting in the continuous accumulation of antibiotics in the environment. In addition, if the human body is exposed to low-dose antibiotics in large quantities for a long time, drug resistance may occur, resulting in a decrease in the therapeutic effect of antibiotics. In addition, the accumulation of antibiotics in the environment may also lead to the emergence of super drug-resistant bacteria, endangering the biological community and posing a threat to biodiversity. In summary, developing a safe, efficient, low-consumption and economical method for treating antibiotics and reducing their ecological risks has important research significance and application value.

[0003] The removal effect of traditional sewage treatment on antibiotics is unstable because the treatment in conventional sewage treatment plants is not targeted at emerging pollutants such as antibiotics. Advanced treatment after conventional biological processes can improve the removal rate of antibiotics, but it increases the operation and maintenance costs. In current research, the treatment of antibiotics mainly includes physicochemical methods, biological methods, and advanced oxidation methods. Physicochemical methods include adsorption, membrane filtration, coagulation, flocculation, and precipitation, etc. Biological methods mainly include aerobic methods, anaerobic methods, photosynthetic bacteria, and microalgae and other technologies. However, physicochemical methods only achieve the enrichment of pollutants and do not truly achieve the degradation of antibiotics. The concentrated solid phase of pollutants needs to be continuously treated. To achieve the goal of completely degrading antibiotics, it needs to be combined with other methods, and the cost is relatively high. Aerobic biological methods have the advantages of stable removal effect, harmlessness, short hydraulic retention time, and good effluent quality, but their applicability is poor, and the wastewater must have the living conditions for organisms. Anaerobic biological methods have the advantages of high removal rate, less sludge production, and less energy consumption, but they also have the disadvantages of long hydraulic retention time, poor effluent quality, and small treatment capacity. Biodegradation methods are only applicable to the removal of easily biodegradable drugs, but the removal effect on antibiotics is limited. Currently, most of the research on antibiotic degradation focuses on the field of advanced oxidation, including ozone oxidation, Fenton oxidation, photocatalytic oxidation, supercritical water oxidation, electrochemical oxidation, etc. However, most of the research on the degradation of antibiotics by advanced oxidation lacks relevant information about the by-products formed during the oxidation process. The by-products may also have ecological toxicity. If advanced oxidation methods are to be used to treat antibiotics, it is necessary to consider controlling the entire oxidation process and monitoring the generation of potential toxic intermediate products. In addition, advanced oxidation technologies also have the disadvantages of poor mineralization effect on antibiotics, high equipment cost, and complex operation and maintenance. The Intimate coupling of photocatalysis and biodegradation (ICPB) technology is a new wastewater treatment technology that combines photocatalysis technology and biological treatment, with the advantages of low cost, environmental friendliness, and sustainability. It combines the advantages of photocatalytic degradation and biodegradation. The small molecular substances produced by photocatalytic degradation of antibiotics can be utilized by microorganisms, resulting in good degradation effect and good mineralization effect.

[0004] Photosynthetic bacteria can carry out photoheterotrophic growth under anaerobic light conditions using low-molecular organic compounds such as lower fatty acids, alcohols, sugars, and carbon dioxide as electron donors for photosynthesis, and can carry out aerobic heterotrophic growth under microaerobic dark conditions using the above-mentioned organic compounds as respiratory substrates. In addition, photosynthetic bacteria also have the advantages of fast reproduction speed, low energy consumption, and no need for sludge disposal. Compared with activated sludge, it has a flexible metabolic mode and higher tolerance, and can more effectively remove organic pollutants in wastewater.

[0005] Therefore, how to effectively remove antibiotics from wastewater by advanced oxidation methods is an urgent problem to be solved at present. Summary of the Invention

[0006] The purpose of the present invention is to provide a biodegradation-photocatalysis composite material, its preparation method and application, to solve the above problems existing in the treatment of antibiotic wastewater by existing advanced oxidation methods.

[0007] In order to achieve the above invention purposes, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a biodegradation-photocatalysis composite material, comprising the following steps:

[0009] Mix a photocatalyst, sodium alginate and water to obtain a gel containing the photocatalyst;

[0010] Mix a photosynthetic bacteria concentrate and the gel containing the photocatalyst to obtain a gel containing microorganisms and the photocatalyst;

[0011] Use a polyurethane sponge as a carrier, add the carrier to the gel containing microorganisms and the photocatalyst for adsorption; after adsorption saturation, obtain a carrier loaded with microorganisms and the photocatalyst;

[0012] Fix the carrier loaded with microorganisms and the photocatalyst in a calcium chloride solution to form a biodegradation-photocatalysis composite material.

[0013] Preferably, in the above preparation method of a biodegradation-photocatalysis composite material, the photocatalyst is a composite of g-C3N4 and TiO2; the mass ratio of g-C3N4 to TiO2 is 0.5-3:1-2.

[0014] Preferably, in the above preparation method of a biodegradation-photocatalysis composite material, the mass concentration of the photocatalyst in the gel containing the photocatalyst is 6-60 g / L; the mass concentration of sodium alginate in the gel containing the photocatalyst is 10 g / L.

[0015] Preferably, in the above preparation method of a biodegradation-photocatalysis composite material, the photosynthetic bacteria concentrate is obtained by centrifuging the photosynthetic bacteria liquid and removing the supernatant; the absorbance A of the photosynthetic bacteria liquid 660 is 1.6-1.8.

[0016] Preferably, in the above preparation method of a biodegradation-photocatalysis composite material, the volume ratio of the photosynthetic bacteria liquid to the gel containing the photocatalyst is 1.5-12:1.

[0017] Preferably, in the above preparation method of a biodegradation-photocatalysis composite material, the adsorption time is 3-10 min.

[0018] Preferably, in the preparation method of the above-mentioned biodegradable-photocatalytic composite material, the mass fraction of calcium chloride in the calcium chloride solution is 1-3%.

[0019] Preferably, in the preparation method of the above-mentioned biodegradable-photocatalytic composite material, the temperature of the fixed molding is 4°C; the time of the fixed molding is 18-24 h.

[0020] The present invention also provides a biodegradable-photocatalytic composite material prepared by the preparation method of the biodegradable-photocatalytic composite material.

[0021] The present invention also provides an application of the biodegradable-photocatalytic composite material in treating antibiotic wastewater.

[0022] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The microorganism of the present invention selects photosynthetic bacteria, which has the advantages of flexible metabolic mode, high tolerance to antibiotics, fast reproduction speed, and no need for sludge disposal.

[0024] (2) The present invention loads the photocatalyst and photosynthetic bacteria on the polyurethane sponge carrier, which protects the photosynthetic bacteria and is also easy to separate from water. The photocatalyst generates highly active substances, converts the refractory antibiotics into biodegradable intermediates. The generated intermediate products are then decomposed by the microorganisms inside the carrier, thereby realizing the efficient degradation and mineralization of antibiotics in sewage. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art.

[0026] Figure 1 For the degradation results of tetracycline hydrochloride of the biodegradable-photocatalytic composite materials in Examples 1-3;

[0027] Figure 2 For the degradation results of tetracycline hydrochloride of the biodegradable-photocatalytic composite materials in Examples 4-7;

[0028] Figure 3 For the degradation results of tetracycline hydrochloride in Application Example 1, Application Comparative Examples 1-3;

[0029] Figure 4 For the mineralization results of Application Example 1, Application Comparative Examples 1-3. Detailed Embodiments

[0030] The present invention provides a method for preparing a biodegradable-photocatalytic composite material, comprising the following steps:

[0031] Mix a photocatalyst, sodium alginate, and water to obtain a gel containing the photocatalyst;

[0032] Mix the photosynthetic bacteria concentrate and the gel containing the photocatalyst to obtain a gel containing microorganisms and the photocatalyst;

[0033] Use a polyurethane sponge as a carrier, add the carrier to the gel containing microorganisms and the photocatalyst for adsorption; after adsorption for a certain time, obtain a carrier loaded with microorganisms and the photocatalyst;

[0034] Fix the carrier loaded with microorganisms and the photocatalyst in a calcium chloride solution to form a biodegradable-photocatalytic composite material.

[0035] In the present invention, the photocatalyst is preferably a composite of g-C3N4 and TiO2; the mass ratio of g-C3N4 to TiO2 is preferably 0.5-3:1-2, more preferably 1-3:1.5-2, and still more preferably 3:2.

[0036] In the present invention, the method for preparing the photocatalyst is as follows: Mix 0.5-3 g of g-C3N4 and 1-2 g of TiO2 in 100 mL of absolute ethanol, place it on a magnetic stirrer and stir for 5 h, then ultrasonicate for 1 h, and then place it in an oven at 70 °C and dry for 36 h to obtain the photocatalyst.

[0037] In the present invention, the mass concentration of the photocatalyst in the gel containing the photocatalyst is preferably 6-60 g / L, more preferably 15-45 g / L, and still more preferably 15 g / L; the mass concentration of sodium alginate in the gel containing the photocatalyst is preferably 10 g / L.

[0038] In the present invention, the method for mixing the photocatalyst, sodium alginate, and water is as follows: First, ultrasonically mix sodium alginate and water for 30 min to form a gel, and then add the photocatalyst and ultrasonically mix for 30 min.

[0039] In the present invention, the photosynthetic bacteria concentrate is preferably obtained by centrifuging the photosynthetic bacteria liquid to remove the supernatant; the absorbance A of the photosynthetic bacteria liquid 660 is preferably 1.6-1.8, more preferably 1.65-1.8, and still more preferably 1.79; the rotation speed of the centrifugation is preferably 8000-10000 rpm, more preferably 8500-9500 rpm, and still more preferably 9000 rpm; the centrifugation time is preferably 10-15 min, more preferably 11-13 min, and still more preferably 12 min.

[0040] In the present invention, the volume ratio of the photosynthetic bacteria liquid to the gel containing the photocatalyst is preferably 1.5 to 12:1, more preferably 3 to 9:1, and still more preferably 3:1.

[0041] In the present invention, the type of photosynthetic bacteria in the photosynthetic bacteria concentrate is preferably Rhodopseudomonas palustris.

[0042] In the present invention, the hydrophilic polyurethane sponge is purchased from Zhengzhou Yuanquan Water Treatment Filler Company. The sponge specification is 2×2×2 cm, and the volume of 3 polyurethane sponges adsorbing the gel containing microorganisms and photocatalyst is 15 mL.

[0043] In the present invention, the adsorption time is preferably 3 to 10 min, more preferably 5 to 10 min, and still more preferably 10 min.

[0044] In the present invention, the mass fraction of calcium chloride in the calcium chloride solution is preferably 1 to 3%, more preferably 1.5 to 3%, and still more preferably 2%.

[0045] In the present invention, the temperature of the fixed molding is preferably 4°C; the time of the fixed molding is preferably 18 to 24 h, more preferably 19 to 22 h, and still more preferably 20 h.

[0046] The present invention also provides a biodegradable-photocatalytic composite material prepared by a preparation method of a biodegradable-photocatalytic composite material.

[0047] The present invention also provides an application of the biodegradable-photocatalytic composite material in treating antibiotic wastewater.

[0048] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Example 1

[0050] This example provides a biodegradable-photocatalytic composite material, and its preparation method includes the following steps:

[0051] (1) Mix 3 g of g-C3N4 and 2 g of TiO2 in 100 mL of absolute ethanol, place it on a magnetic stirrer and stir for 5 h, then ultrasonicate for 1 h, and then place it in an oven at 70°C and dry for 36 h to obtain a photocatalyst;

[0052] 0.1 g of sodium alginate and 10 mL of water were ultrasonically mixed for 30 min to form a gel, and then 0.15 g of photocatalyst was added and ultrasonically mixed for 30 min to obtain a gel containing the photocatalyst;

[0053] (2) 30 mL of photosynthetic bacteria broth with an absorbance A 660 of 1.79 was centrifuged at 9000 rpm for 12 min, and then the supernatant was removed to obtain 5 mL of concentrated photosynthetic bacteria solution;

[0054] The concentrated photosynthetic bacteria solution was added to the gel containing the photocatalyst and mixed evenly to obtain 15 mL of gel containing microorganisms and the photocatalyst;

[0055] (3) Using hydrophilic polyurethane sponge as a carrier, 3 carriers with dimensions of 2×2×2 cm were added to the gel containing microorganisms and the photocatalyst for adsorption; the total adsorption amount of the 3 carriers was 15 mL to obtain a carrier loaded with microorganisms and the photocatalyst;

[0056] (4) The carrier loaded with microorganisms and the photocatalyst was added to a calcium chloride solution with a mass fraction of 2%, refrigerated at 4 °C in a refrigerator for 20 h to be fixed and formed, and then washed 3 times with ultrapure water to obtain a biodegradation-photocatalysis composite material (this biodegradation-photocatalysis composite material consists of 3 carriers loaded with microorganisms and the photocatalyst), denoted as 0.5 g / L BC / P25 (0.5 g / L BC / P25 refers to the concentration of the photocatalyst in the wastewater to be treated).

[0057] Example 2

[0058] This example provides a biodegradation-photocatalysis composite material. Specifically, refer to Example 1. The difference is that the addition amount of the photocatalyst in step (1) is 0.3 g, and the obtained biodegradation-photocatalysis composite material is denoted as 1.0 g / L BC / P25.

[0059] Example 3

[0060] This example provides a biodegradation-photocatalysis composite material. Specifically, refer to Example 1. The difference is that the addition amount of the photocatalyst in step (1) is 0.45 g, and the obtained biodegradation-photocatalysis composite material is denoted as 1.5 g / L BC / P25.

[0061] Example 4

[0062] This example provides a biodegradation-photocatalysis composite material. Specifically, refer to Example 1. The difference is that the volume of the photosynthetic bacteria broth in step (2) is 15 mL, and the obtained biodegradation-photocatalysis composite material is denoted as 5% PSB (5% PSB refers to the percentage of the volume of the photosynthetic bacteria broth in the volume of the wastewater to be treated).

[0063] Example 5

[0064] This example provides a biodegradable-photocatalytic composite material. For details, refer to Example 1. This example is the same as Example 1, except that it is renamed 10% PSB according to the addition amount of photosynthetic bacteria.

[0065] Example 6

[0066] This example provides a biodegradable-photocatalytic composite material. For details, refer to Example 1. The difference is that the volume of the photosynthetic bacteria liquid in step (2) is 60 mL, and the obtained biodegradable-photocatalytic composite material is denoted as 20% PSB.

[0067] Example 7

[0068] This example provides a biodegradable-photocatalytic composite material. For details, refer to Example 1. The difference is that the volume of the photosynthetic bacteria liquid in step (2) is 90 mL, and the obtained biodegradable-photocatalytic composite material is denoted as 30% PSB.

[0069] Perform the degradation experiment of tetracycline hydrochloride on the biodegradable-photocatalytic composite materials prepared in Examples 1-7. The specific method is as follows: Add the biodegradable-photocatalytic composite material (this biodegradable-photocatalytic composite material consists of 3 carriers loaded with microorganisms and photocatalysts) to 300 mL of a tetracycline hydrochloride solution with a concentration of 20 mg / L to obtain a mixed solution. Place the mixed solution under the light source of a halogen lamp (220 - 240 V, 300 W) and irradiate for 96 h. Every 12 h, transfer 8 mL of the mixed solution from the mixed solution to a centrifuge, centrifuge at a speed of 10000 rpm for 5 min, take the supernatant, and measure the absorbance at 357 nm using a UV-visible spectrophotometer to calculate the concentration of tetracycline hydrochloride in the mixed solution. The results are as Figures 1 to 2 shown. From Figure 1 , Figure 2 it can be seen that the biodegradable-photocatalytic composite material can degrade tetracycline hydrochloride. Different addition amounts of the photocatalyst and photosynthetic bacteria will result in different effects on the degradation of tetracycline hydrochloride.

[0070] Comparative Example 1

[0071] This comparative example provides a photocatalytic material. For details, refer to Example 6. The difference is that no photosynthetic bacteria concentrate is added, that is, step (2) is not carried out.

[0072] Comparative Example 2

[0073] This comparative example provides a biodegradable material. For details, refer to Example 6. The difference is that no photocatalyst is added, that is, no photocatalyst is added in step (1).

[0074] Application Example 1

[0075] The biodegradable-photocatalytic composite material of Example 6 was used for the degradation of tetracycline hydrochloride. The specific method was as follows: The biodegradable-photocatalytic composite material (which consisted of 3 carriers loaded with microorganisms and photocatalysts) was added to 300 mL of a tetracycline hydrochloride solution with a concentration of 10 mg / L to obtain a mixed solution. The mixed solution was irradiated under a halogen lamp (220 - 240 V, 300 W) for 120 h. Every 12 h, 8 mL of the mixed solution was taken from the mixed solution and placed in a centrifuge, centrifuged at a speed of 10,000 rpm for 5 min, the supernatant was taken, and the absorbance was measured at 357 nm using a UV-visible spectrophotometer to calculate the concentration of tetracycline hydrochloride in the mixed solution. The COD was determined by the potassium dichromate method. The results were as Figures 3 to 4 shown.

[0076] Application of Comparative Example 1

[0077] The photocatalytic material of Comparative Example 1 was used for the degradation of tetracycline hydrochloride. For the specific method, refer to Application Example 1. The concentration of tetracycline hydrochloride in the mixed solution and the results of COD determination by the potassium dichromate method were as Figures 3 to 4 shown.

[0078] Application of Comparative Example 2

[0079] The biodegradable material of Comparative Example 2 was used for the degradation of tetracycline hydrochloride. For the specific method, refer to Application Example 1. The concentration of tetracycline hydrochloride in the mixed solution and the results of COD determination by the potassium dichromate method were as Figures 3 to 4 shown.

[0080] Application of Comparative Example 3

[0081] Using the degradation of tetracycline hydrochloride without adding the biodegradable-photocatalytic composite material as a blank control. For the specific method, refer to Application Example 1. The concentration of tetracycline hydrochloride in the mixed solution and the results of COD determination by the potassium dichromate method were as Figures 3 to 4 shown.

[0082] From Figure 3 , Figure 4 it can be seen that the degradation effect of using the biodegradable-photocatalytic composite material to degrade tetracycline hydrochloride is better than that of the single photocatalytic system and the single photosynthetic bacteria system. The degradation rate can reach 66.05% at 120 h, and the mineralization rate is also higher than that of the single photocatalytic system and the single photosynthetic bacteria system, reaching 62.3%.

[0083] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a biodegradable-photocatalytic composite material, characterized in that: The following steps are involved: Mixing a photocatalyst, sodium alginate and water to obtain a gel containing the photocatalyst; Mixing the concentrated solution of photosynthetic bacteria and the gel containing the photocatalyst to obtain a gel containing microorganisms and the photocatalyst; Using polyurethane sponge as a carrier, adding the carrier into a gel containing microorganisms and photocatalysts for adsorption; after adsorption, a carrier loaded with microorganisms and photocatalysts is obtained; The carrier loaded with microorganisms and photocatalysts is fixed and formed in a calcium chloride solution to obtain a biodegradable-photocatalytic composite material.

2. The method for preparing a biodegradable-photocatalytic composite material according to claim 1, characterized in that: The photocatalyst is a composite of g-C3N4 and TiO2; the mass ratio of g-C3N4 to TiO2 is 0.5-3:1-2.

3. The method for preparing a biodegradable-photocatalytic composite material according to claim 2, characterized in that: The mass concentration of the photocatalyst in the gel containing the photocatalyst is 6-60 g / L; the mass concentration of the sodium alginate in the gel containing the photocatalyst is 10 g / L.

4. The method for preparing a biodegradable-photocatalytic composite material according to claim 1 or 3, characterized in that: The photosynthetic bacteria concentrate is obtained by removing the supernatant from the photosynthetic bacteria solution after centrifugation; the absorbance A of the photosynthetic bacteria solution is 660 It is 1.6 to 1.

8.

5. The method for preparing a biodegradable-photocatalytic composite material according to claim 4, characterized in that: The volume ratio of the photosynthetic bacteria liquid to the gel containing the photocatalyst is 1.5-12:

1.

6. The method for preparing a biodegradable-photocatalytic composite material according to claim 5, characterized in that: The adsorption time is 3 to 10 minutes.

7. The method for preparing a biodegradable-photocatalytic composite material according to claim 6, characterized in that: The mass fraction of calcium chloride in the calcium chloride solution is 1-3%.

8. The method for preparing a biodegradable-photocatalytic composite material according to claim 5 or 7, characterized in that: The temperature of the fixing and molding is 4° C.; the time of the fixing and molding is 18 to 24 hours.

9. A biodegradable-photocatalytic composite material obtained by the method for preparing a biodegradable-photocatalytic composite material according to any one of claims 1 to 8.

10. Use of the biodegradation-photocatalytic composite material according to claim 9 in treating antibiotic wastewater.

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