TEPA-ZIF-8@ sulfate-reducing bacteria-cadmium sulfide hybrid system and preparation method and application thereof

Abstract

The application discloses a TEPA-ZIF-8@ sulfate reducing bacteria-cadmium sulfide hybrid system and a preparation method and application thereof, and belongs to the technical field of catalytic material synthesis. The TEPA-ZIF-8@ sulfate reducing bacteria-cadmium sulfide hybrid system comprises TEPA-ZIF-8 immobilized sulfate reducing bacteria loaded with cadmium sulfide; and the TEPA-ZIF-8 is ZIF-8 modified by tetraethylenepentamine. The ZIF-8 functionalized by TEPA is compounded with sulfate reducing bacteria for the first time, the amino group of TEPA is used to enhance the coordination adsorption capacity of ZIF-8 to heavy metals, and the biocompatibility of ZIF-8 to the cell wall of bacteria is improved; and the sulfide produced by the metabolism of sulfate reducing bacteria is in-situ biomineralized to generate CdS nanoparticles, a ternary composite structure is constructed, the separation and transmission of photo-generated carriers are effectively promoted, and the synergy of adsorption-biological reduction-photocatalysis is realized. The application has great application potential in efficient removal of azo dyes, sulfate ions and heavy metal ions in wastewater, and realization of wastewater purification and sulfur resource conversion.

Description

Technical Field

[0001] This invention belongs to the field of catalytic material synthesis technology, specifically relating to a TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, its preparation method, and its application. Background Technology

[0002] With the acceleration of industrialization and urbanization, heavy metal pollution has become increasingly serious, and the large-scale discharge of sulfate wastewater has also brought serious environmental hazards. Sulfate-reducing bacteria (SRB), as a type of anaerobic microorganism widely found in nature, can use sulfate as an electron acceptor to reduce it to hydrogen sulfide, simultaneously degrading organic pollutants and precipitating heavy metal ions, showing unique application potential in the fields of heavy metal pollution control and sulfate-containing wastewater treatment. However, traditional sulfate-reducing bacteria treatment systems suffer from problems such as easy loss of bacteria, poor environmental tolerance, limited electron transfer efficiency, and insufficient utilization of light energy, which seriously restrict their treatment efficiency and application scope.

[0003] In recent years, the construction of hybrid systems by coupling semiconductor materials with microorganisms has become a research hotspot in the field of environmental biotechnology. Cadmium sulfide (CdS), as a typical narrow bandgap semiconductor material, has excellent visible light response characteristics, effectively capturing light energy and generating photogenerated electrons, providing exogenous reducing power for microbial metabolism, thereby enhancing the metabolic activity of microorganisms. However, free CdS nanoparticles are prone to aggregation, have poor biocompatibility, and the interfacial electron transfer efficiency between them and microorganisms needs to be improved. Metal-organic frameworks (MOFs) have shown significant advantages in immobilizing microorganisms and serving as nanomaterial carriers due to their high specific surface area, tunable pore structure, and excellent biocompatibility. Among them, the zeolite imidazolate framework material ZIF-8 has good chemical stability and biocompatibility, making it an ideal carrier for immobilizing sulfate-reducing bacteria and providing a good platform for loading CdS nanoparticles.

[0004] However, while the abundant methylimidazolium ligands on the ZIF-8 surface can interact with functional groups on the surface of microbial cells, their interfacial affinity still needs further improvement. Studies have shown that amine functionalization modification of ZIF-8, such as the introduction of tetraethylenepentamine (TEPA), can significantly enhance the surface charge and the density of active functional groups, thereby strengthening the interfacial binding force with microbial cells through electrostatic and coordination interactions, improving immobilization efficiency and bioload. Simultaneously, the abundant amine functional groups in TEPA can form stable coordination complexes with cadmium ions, providing ideal sites for in-situ nucleation and growth of cadmium sulfide, which is beneficial for constructing a structurally stable, tightly integrated, and optimized multi-component hybrid system.

[0005] Currently, existing studies have reported the applications of sulfate-reducing bacteria immobilized on metal-organic frameworks (MOFs), semiconductor material-microbial hybrid systems, or amine-functionalized MOFs in environmental remediation. However, there are no reports on the organic combination of TEPA-functionalized ZIF-8, sulfate-reducing bacteria, and cadmium sulfide to construct a multi-component hybrid system with synergistic effects. In existing technologies, the combination of microorganisms and semiconductor materials is mostly through physical mixing or surface adsorption, which suffers from problems such as weak interfacial bonding, low electron transfer efficiency, and poor system stability, making it difficult to fully leverage the synergistic effect of microbial metabolic activity and semiconductor photocatalytic properties. Therefore, developing a hybrid system that can achieve efficient bacterial immobilization, enhanced interfacial electron transfer, and synergistic utilization of light energy to promote sulfate reduction and heavy metal removal is of great significance for improving the treatment efficiency of sulfate-reducing bacteria in complex environmental media and expanding their applications in pollution control and bioenergy conversion. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system to address the shortcomings of the prior art.

[0007] Another technical problem to be solved by the present invention is to provide a method for preparing the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system.

[0008] The final technical problem to be solved by this invention is to provide the application of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in the photocatalytic removal of heavy metal ions and / or sulfates and / or dyes from wastewater.

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0010] The first aspect of the present invention provides a TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, comprising TEPA-ZIF-8 immobilized sulfate-reducing bacteria loaded with cadmium sulfide; wherein the TEPA-ZIF-8 is a tetraethylenepentamine-modified ZIF-8.

[0011] In some embodiments, the sulfate-reducing bacteria are Desulfobacter sp. SRB-1, its classification name is Desulfobacter sp . The strain number is SRB-1, which was deposited on January 28, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 46917. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0012] The second aspect of this invention provides a method for preparing the aforementioned TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, comprising the following steps:

[0013] The sulfate-reducing bacteria seed culture is inoculated into a first culture medium for a first culture to obtain a first culture solution. Sulfate and TEPA-ZIF-8 are added to the first culture solution for a second culture to obtain a second culture solution. Cadmium salt is added to the second culture solution for a third culture to obtain the final product.

[0014] The method for preparing the sulfate-reducing bacteria seed culture includes the following steps: after activating the sulfate-reducing bacteria, inoculate them into Postgate medium and incubate them under anaerobic conditions at 35-37°C for 24-48 h; the inoculation amount of the sulfate-reducing bacteria seed culture in the first medium is 5-10% v / v.

[0015] Specifically, the amount of sulfate added is controlled to the amount of SO4 in the culture medium. 2- The concentration of TEPA-ZIF-8 is 1-2 g / L; the amount of TEPA-ZIF-8 added is controlled so that the content of TEPA-ZIF-8 in the culture medium is 150-300 mg / L; the amount of cadmium salt added is controlled so that the content of Cd in the culture medium is 150-300 mg / L. 2+ The concentration is 0.009 ~ 0.013 mg / L.

[0016] In some embodiments, the amount of sulfate added to the culture medium is controlled to SO4 2- The concentration of TEPA-ZIF-8 was 2 g / L; the amount of TEPA-ZIF-8 added was controlled so that the content of TEPA-ZIF-8 in the culture medium was 150 mg / L; the amount of cadmium salt added was controlled so that the content of Cd in the culture medium was 150 mg / L. 2+ The concentration was 0.013 mg / L.

[0017] In some embodiments, the cadmium salt is added to the second culture medium in the form of an aqueous solution.

[0018] In some embodiments, the cadmium salt is cadmium chloride.

[0019] In some embodiments, the cadmium salt is added to the second culture medium in the form of an aqueous cadmium chloride solution; the concentration of the aqueous cadmium chloride solution is 20 mg / L.

[0020] The first culture medium is SO4-free. 2- or SO4 2-The first culture was carried out under anaerobic conditions at 35-37°C for 24-48 hours; the second culture was carried out under anaerobic conditions at 120-200 rpm for 2 hours; and the third culture was carried out under anaerobic conditions at 35-37°C for 24-48 hours.

[0021] In some embodiments, the Postgate medium comprises the following components: 0.5 g / L dipotassium hydrogen phosphate, 1 g / L ammonium chloride, 2 g / L anhydrous sodium sulfate, 0.16 g / L anhydrous magnesium sulfate, 0.1 g / L anhydrous calcium chloride, 5 g / L 70 wt% sodium lactate, 1 g / L yeast extract, 0.1 g / L ascorbic acid, and a pH of 6.5 to 7.5.

[0022] In some embodiments, the SO4-free 2- The Postgate medium contains the following components: 0.5 g / L dipotassium hydrogen phosphate, 1 g / L ammonium chloride, 0.16 g / L anhydrous magnesium chloride, 0.1 g / L anhydrous calcium chloride, 5 g / L 70 wt% sodium lactate, 1 g / L yeast extract, 0.1 g / L ascorbic acid, and a pH of 6.5 to 7.5.

[0023] In some embodiments, the SO4 2- Postgate medium with a concentration not exceeding 0.2 g / L contains the following components: 0.5 g / L dipotassium hydrogen phosphate, 1 g / L ammonium chloride, 0.2 g / L anhydrous magnesium sulfate, 0.1 g / L anhydrous calcium chloride, 5 g / L 70 wt% sodium lactate, 1 g / L yeast extract, and 0.1 g / L ascorbic acid, with a pH of 6.5 to 7.5.

[0024] The TEPA-ZIF-8 is prepared by a method comprising the following steps:

[0025] Tetraethylenepentamine, zinc ion solution and 2-methylimidazole solution are mixed to carry out the first reaction to obtain the first reaction solution. After standing and aging, solid and liquid are separated, the solid is collected, washed and dried to obtain TEPA-ZIF-8 with a particle size of 150~250 nm.

[0026] The amounts of tetraethylenepentamine, zinc ion solution, and 2-methylimidazole solution added are controlled such that the molar ratio of tetraethylenepentamine, zinc ions, and 2-methylimidazole is (1~2):1:12; the first reaction is carried out under the condition of stirring at room temperature for 15~30 min; and the aging time is at least 24 h.

[0027] In some embodiments, the mixing method of the tetraethylenepentamine, zinc ion solution and 2-methylimidazole solution is as follows: the tetraethylenepentamine and zinc ion solution are added to the 2-methylimidazole solution in sequence and mixed evenly; the zinc ion solution is added completely within 20 to 30 seconds.

[0028] In some embodiments, the amounts of tetraethylenepentamine, zinc ion solution, and 2-methylimidazole solution added are controlled such that the molar ratio of tetraethylenepentamine, zinc ions, and 2-methylimidazole is 1:1:12.

[0029] In some embodiments, the static aging period is 24 h to 48 h.

[0030] In some embodiments, the solvent for both the zinc ion solution and the 2-methylimidazole solution is water; the concentration of the zinc ion solution is 0.27 M; and the concentration of the 2-methylimidazole solution is 3.28 M.

[0031] In some embodiments, the washing is washing with water; the drying is performed at 50°C for 2 hours.

[0032] The third aspect of this invention provides the application of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in the photocatalytic removal of heavy metal ions and / or sulfates and / or dyes from wastewater.

[0033] The heavy metal ions mentioned above are those capable of reacting with S. 2- The reaction produces precipitated heavy metal ions; the dye is an azo dye.

[0034] Heavy metal ions and S 2- The reaction produces a precipitate, which is removed from the wastewater. The precipitated heavy metal ions can be further recycled. Sulfate-reducing bacteria reduce sulfate in the wastewater to sulfur. 2- It can be further recycled.

[0035] In some embodiments, the dye is Congo red.

[0036] In some embodiments, the heavy metal ion is Pb. 2+ Cd 2+ Ag + Cu 2+ Hg 2+ Fe 2+ Mn 2+ Zn 2+ Ni 2+ Co 2+ Bi 3+ Sb 3+ Sb 5+ Sn2+ Sn 4+ As 3+ As 5+ Mo 5+ and Mo 6+ Any one or more combinations thereof.

[0037] In some embodiments, the heavy metal ion is Pb. 2+ and / or Cd 2+ .

[0038] In some embodiments, the wavelength of the light is 380 ~ 840 nm; the power density of the light is 30 ~ 100 W / m². 2 .

[0039] Beneficial effects:

[0040] This invention is the first to combine TEPA-functionalized ZIF-8 with sulfate-reducing bacteria. The molecular sieving effect and photoelectron shielding of TEPA-ZIF-8 protect the metabolic activity of SRBs and improve the biocompatibility of ZIF-8 with the bacterial cell wall. Furthermore, the amino groups of TEPA enhance the coordination adsorption capacity of ZIF-8 for heavy metals, prompting SRBs to continuously generate bio-sulfides through dissimilar sulfate reduction, which then react in situ with cadmium ions to generate cadmium sulfide nanoparticles (CdS), ultimately forming a ternary hybrid system with both bio-metabolic function and photocatalytic activity. This effectively promotes the separation and transport of photogenerated charge carriers, achieving a synergistic effect of adsorption-bioreduction-photocatalysis. Through the synergistic mechanism of heavy metal chelation at the amino sites of TEPA, SRB-mediated bio-sulfide precipitation, and CdS photocatalytic reduction, this system can selectively function under visible light according to application requirements: on the one hand, it efficiently degrades azo dyes such as Congo red; on the other hand, it photocatalytically reduces sulfate ions to sulfide ions and simultaneously removes Pb. 2+ Using heavy metal ions, it achieves the dual goals of wastewater purification and sulfur resource conversion, and has significant advantages such as simple process, low cost, environmental friendliness and no secondary pollution. Attached Figure Description

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0042] Figure 1 The images show SEM images of sulfate-reducing bacteria and TEPA-ZIF-8@SRB in Example 1; where image A is the SEM image of sulfate-reducing bacteria and image B is the SEM image of TEPA-ZIF-8@SRB.

[0043] Figure 2The fluorescence spectra of sulfate-reducing bacteria and TEPA-ZIF-8@SRB in Example 1 are shown.

[0044] Figure 3 The UV-Vis spectra of sulfate-reducing bacteria and TEPA-ZIF-8@SRB in Example 1 are shown.

[0045] Figure 4 The images show actual photographs of the sulfate-reducing bacteria culture and the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in Example 1; where Figure A is an actual photograph of the sulfate-reducing bacteria culture and Figure B is an actual photograph of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system.

[0046] Figure 5 The image shows the electrochemical it curve of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in Example 2.

[0047] Figure 6 The Pb content of the sulfate-reducing bacteria and TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in Example 3 is... 2+ With SO4 2- Removal rate statistics chart.

[0048] Figure 7 The curves showing the change in Congo red residue rate over time for the TEPA-ZIF-8@SRB-CdS-light group, the TEPA-ZIF-8@SRB-CdS-dark group, and the SRB-CdS-light group in Example 4 are shown.

[0049] Figure 8 The removal rate of Congo red dye by the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in Example 5 under repeated use. Detailed Implementation

[0050] The present invention will be further described below with reference to the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0051] The Postgate C medium used in the following examples has the following formulation: dipotassium hydrogen phosphate 0.5 g / L, ammonium chloride 1 g / L, anhydrous sodium sulfate 2 g / L, anhydrous magnesium sulfate 0.2 g / L, anhydrous calcium chloride 0.1 g / L, 70 wt% sodium lactate (70% w / w in water) 5 g / L, yeast extract 1 g / L, and ascorbic acid 0.1 g / L.

[0052] The following examples use SO4-free materials. 2-The Postgate medium contains the following components: 0.5 g / L dipotassium hydrogen phosphate, 1 g / L ammonium chloride, 0.16 g / L anhydrous magnesium chloride, 0.1 g / L anhydrous calcium chloride, 5 g / L 70 wt% sodium lactate (70% w / w in water), 1 g / L yeast extract, and 0.1 g / L ascorbic acid, with a pH of 6.5 ~ 7.5.

[0053] Example 1

[0054] (1) Synthesis of TEPA-ZIF-8: 1.5 g of zinc acetate dihydrate and 6.73 g of 2-methylimidazole were dissolved in 25 mL of deionized water to prepare aqueous solutions of zinc acetate and 2-methylimidazole. 1.29 g of tetraethylenepentamine (TEPA) and the above-mentioned zinc acetate aqueous solution were added to the above-mentioned 2-methylimidazole aqueous solution and mixed evenly (the zinc acetate aqueous solution was added within 30 s). The resulting mixture was stirred at 750 rpm for 30 min at room temperature. After the reaction was completed, it was allowed to stand at room temperature for 24 h to precipitate. The precipitate was collected by centrifugation at 9000 rpm for 15 min, washed three times with deionized water, and dried at 50 °C for 2 h.

[0055] (2) Preparation of TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid material: The sulfate-reducing bacteria that have been frozen are prepared by... Desulfobacter After activation, sp. SRB-1 (CGMCC No. 46917) was inoculated into anaerobic Postgate C medium. High-purity nitrogen (N2, 99.999%) was bubbled into the inoculated Postgate C medium for 10 min, then sealed with a rubber stopper. The medium was then incubated statically at 37°C for 24 h to obtain… Desulfobacter Sp. SRB-1 seed culture. The seed culture was inoculated into 100 mL of fresh Postage C medium without anhydrous sodium sulfate at an inoculation rate of 10% v / v. After 48 h of static incubation in an anaerobic incubator at 37°C, anhydrous sodium sulfate (the concentration of sodium sulfate in the culture medium was controlled at 2 g / L) and 15 mg of pre-synthesized TEPA-ZIF-8 were added. After 2 h of anaerobic incubation in a shaker at 200 rpm at 37°C, 0.1 mL of 20 mg / L cadmium chloride aqueous solution was added. After 24 h of static incubation under anaerobic conditions at 37°C, the solution turned bright yellow, which is the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system.

[0056] Figure 1SEM images of sulfate-reducing bacteria (SRB) and the TEPA-ZIF-8@sulfate-reducing bacteria hybrid system (TEPA-ZIF-8@SRB, with culture medium components removed) prepared in this example are shown. As can be seen from the images, TEPA-ZIF-8 was successfully adsorbed onto the surface of sulfate-reducing bacteria (SRB). Figure 2 The fluorescence spectra of SRB and the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system (TEPA-ZIF-8@SRB-CdS, with the culture medium components removed) prepared in this example are shown in the figure. As can be seen from the figure, compared with SRB, the fluorescence intensity of TEPA-ZIF-8@SRB-CdS is significantly enhanced after the introduction of cadmium sulfide (CdS). Figure 3 The UV-Vis spectra of SRB and TEPA-ZIF-8@SRB-CdS (with culture medium components removed) are shown. The spectroscopic results indicate that an absorption peak appears at 485 nm after the introduction of CdS. Figure 4 Photographs of SRB bacterial culture and the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system (TEPA-ZIF-8@SRB-CdS) prepared in this example.

[0057] Example 2

[0058] Detection of photocatalytic performance of TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system.

[0059] The TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system prepared in Example 1 was centrifuged to remove culture medium components, washed three times with deionized water, and then freeze-dried. 5 mg of the completely dried sample was taken and added to 200 μL of 60 vol% ethanol aqueous solution, mixed thoroughly, and the mixture was pipetted onto a glassy carbon electrode. After drying, another drop was added to spread the mixture evenly over the entire glassy carbon electrode. After complete drying, this mixture was used as the working electrode in a three-electrode circuit, with Pt as the auxiliary electrode and Ag / AgCl as the reference electrode. The above three-electrode circuit was placed in a 20 mL electrolytic cell containing 0.1 M Na₂SO₄ and operated at 3000 W / m². 2 Using a xenon lamp as the light source, simulated light and dark conditions for 800 seconds, switching the lamp on and off every 30 seconds to cycle through the simulated light and dark conditions. The instantaneous photocurrent response was tested using the CHI 660E electrochemical workpiece to select the it curve.

[0060] Figure 5The transient photocurrent response of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system is shown. The stable photocurrent under illumination is -0.29 μA, and the stable photocurrent under darkness is -0.34 μA. This indicates that the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system can generate photoelectrons and has good photosensitivity.

[0061] Example 3

[0062] TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system for Pb removal 2+ .

[0063] Centrifuge 100 mL of SRB bacterial culture and 100 mL of TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system prepared in Example 1 at 5000 rpm for 10 min respectively. Wash the precipitates with Postage C medium and add them to fresh 100 mL of Postage C medium respectively (the purpose is to prevent S from entering the original hybrid system). 2- With Pb 2+ The reaction eliminates S from the original hybrid system. 2- For Pb 2+ (Effect of removal rate), adding 20 mg / L of Pb 2+ Then, it was placed at a wavelength of 380 ~ 840 nm and a power density of 30 W / m. 2 Irradiation was performed under a light source, and samples were taken to measure Pb in the culture medium after 48 hours. 2+ The concentration of SO4 2- concentration.

[0064] The method for preparing 100 mL of SRB bacterial solution used in this embodiment differs from the method for preparing the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system in Example 1 only in that TEPA-ZIF-8 and cadmium chloride are not added.

[0065] Experimental results are as follows Figure 6 As shown, it can be seen that compared with sulfate-reducing bacteria, the Pb content of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system is lower. 2+ and SO4 2- The removal rates increased by 10.39% and 18.5%, respectively.

[0066] Under visible light irradiation, in the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, CdS quantum dots are excited to generate photogenerated electron-hole pairs. These photoelectrons are transferred via the TEPA-ZIF-8 framework to the surface of the sulfate-reducing bacteria, and then enter the cell via the extracellular electron transport system, driving the sulfate-reducing bacteria to convert SO42-. 2- Restore to S 2-Meanwhile, TEPA-ZIF-8 enriches Pb through coordination adsorption of imidazole rings and amino groups. 2+ S produced by bacterial metabolism 2- With Pb 2+ The in-situ reaction produces a highly insoluble PbS precipitate. The ZIF-8 shell physically isolates the CdS quantum dots from the SRB cells, preventing photogenerated holes from directly contacting the bacteria and causing oxidative damage, while allowing electrons and substrate / product molecules to diffuse and transfer. The photogenerated holes are then consumed by the oxidation of water or other sacrificial agents, thus achieving Pb... 2+ and SO4 2- synergistic and efficient removal.

[0067] Example 4

[0068] The TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system degrades Congo red dye.

[0069] The TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system prepared in Example 1 was centrifuged at 5000 rpm for 10 min. The precipitate was washed with Postage C medium and then added to a fresh 100 mL of Postage C medium for Congo red degradation experiments. Congo red solution was added to the reaction system to achieve an initial concentration of 80 mg / L and the mixture was incubated at 30 W / m². 2 The samples were irradiated under a light source and reacted under constant conditions for 30 minutes, with the residual rate of the Congo red dye measured every 5 minutes. This experimental group was named the TEPA-ZIF-8@SRB-CdS-light group.

[0070] Two control groups, TEPA-ZIF-8@SRB-CdS-dark and SRB-CdS-light, were set up. The setup method of the TEPA-ZIF-8@SRB-CdS-dark group differed from that of the TEPA-ZIF-8@SRB-CdS-light group only in that there was no light source. The setup method of the SRB-CdS-light group differed from that of the TEPA-ZIF-8@SRB-CdS-light group only in that SRB-CdS was used to replace the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system of the TEPA-ZIF-8@SRB-CdS-light group.

[0071] The preparation method of SRB-CdS is as follows: sulfate-reducing bacteria that have been frozen and preserved are... DesulfobacterAfter activation, sp. SRB-1 (CGMCC No. 46917) was inoculated into anaerobic Postgate C medium. High-purity nitrogen (N2, 99.999%) was bubbled into the inoculated Postgate C medium for 10 min, then sealed with a rubber stopper. The medium was then incubated statically at 37°C for 24 h to obtain… Desulfobacter Sp. SRB-1 seed culture. The seed culture was inoculated into 100 mL Postage C medium at an inoculation rate of 10% v / v, and then 0.1 mL of 20 mg / L cadmium chloride aqueous solution was added. After static incubation at 37℃ under anaerobic conditions for 24 h, the culture was obtained.

[0072] Experimental results are as follows Figure 7 As shown, the degradation rate of Congo red in the TEPA-ZIF-8@SRB-CdS-light group was significantly better than that in the TEPA-ZIF-8@SRB-CdS-dark group and the SRB-CdS-light group. Moreover, the Congo red residue rate in the TEPA-ZIF-8@SRB-CdS-light group was close to 0 within 30 min, which was significantly lower than that in the TEPA-ZIF-8@SRB-CdS-dark group and the SRB-CdS-light group. In particular, the Congo red in the TEPA-ZIF-8@SRB-CdS-dark group was hardly degraded.

[0073] Example 5

[0074] The effect of TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system on the removal of Congo red dye under repeated use.

[0075] The TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system prepared in Example 1 was centrifuged at 5000 rpm for 10 min. The precipitate was washed with Postage C medium and then added to a fresh 100 mL of Postage C medium for ten consecutive cycles of Congo red degradation experiments. In each cycle, Congo red solution was added to the reaction system to achieve an initial concentration of 80 mg / L and the system was incubated at 30 W / m 2 The dye was irradiated under a light source and reacted for 30 minutes under constant conditions. The removal rate of the dye during this cycle was then measured. Subsequently, Congo red was added to restore the concentration in the reaction system to 80 mg / L, and the degradation experiment for the next cycle was immediately carried out. This process was repeated for ten cycles.

[0076] Figure 8The graph shows the number of cycles of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system for degrading Congo red dye. It can be seen that under light conditions, the degradation rate of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system can reach 84% within ten cycles. With increasing cycle count, the removal efficiency decreases to some extent, but still remains above 80%. This may be related to the accumulation of sulfide deposits on the material surface, thus affecting the photoelectron transfer process.

[0077] This invention provides a TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system, characterized in that, It contains TEPA-ZIF-8 immobilized sulfate-reducing bacteria loaded with cadmium sulfide; the TEPA-ZIF-8 is a tetraethylenepentamine-modified ZIF-8.

2. The TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system according to claim 1, characterized in that, The sulfate-reducing bacteria are Desulfobacter sp. SRB-1.

3. The method for preparing the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system according to claim 1 or 2, characterized in that, Includes the following steps: The seed culture of the sulfate-reducing bacteria is inoculated into a first culture medium for a first culture to obtain a first culture solution. Sulfate and TEPA-ZIF-8 are added to the first culture solution for a second culture to obtain a second culture solution. Cadmium salt is added to the second culture solution for a third culture to obtain the final product.

4. The preparation method according to claim 3, characterized in that, The preparation method of the sulfate-reducing bacteria seed culture includes the following steps: after activating the sulfate-reducing bacteria, inoculate them into Postgate medium and incubate them under anaerobic conditions at 35-37℃ for 24-48 h; the inoculation amount of the sulfate-reducing bacteria seed culture in the first medium is 5-10% v / v.

5. The preparation method according to claim 3, characterized in that, Controlling the amount of sulfate added to the culture medium SO4 2- The concentration of TEPA-ZIF-8 is 1-2 g / L; the amount of TEPA-ZIF-8 added is controlled so that the content of TEPA-ZIF-8 in the culture medium is 150-300 mg / L; the amount of cadmium salt added is controlled so that the content of Cd in the culture medium is 150-300 mg / L. 2+ The concentration is 0.009 ~ 0.013 mg / L.

6. The preparation method according to claim 3, characterized in that, The first culture medium is SO4-free. 2- or SO4 2- The first culture is carried out in Postgate medium with a concentration not exceeding 0.2 g / L; the second culture is carried out in anaerobic conditions at 35-37°C for 24-48 h; the third culture is carried out in anaerobic conditions at 120-200 rpm for 2 h; the fourth culture is carried out in anaerobic conditions at 35-37°C for 24-48 h.

7. The preparation method according to claim 3, characterized in that, The TEPA-ZIF-8 is prepared by a method comprising the following steps: Tetraethylenepentamine, zinc ion solution, and 2-methylimidazole solution are mixed and subjected to the first reaction to obtain the first reaction solution. The solution is allowed to stand and age, and the solid and liquid are separated. The solid is collected, washed, and dried to obtain the final product.

8. The preparation method according to claim 7, characterized in that, The amounts of tetraethylenepentamine, zinc ion solution, and 2-methylimidazole solution added are controlled such that the molar ratio of tetraethylenepentamine, zinc ions, and 2-methylimidazole is (1~2):1:12; the zinc ion solution is zinc acetate solution; the first reaction is carried out under the condition of stirring at room temperature for 15~30 min; the aging time is at least 24 h.

9. The application of the TEPA-ZIF-8@sulfate-reducing bacteria-cadmium sulfide hybrid system according to claim 1 or 2 in the photocatalytic removal of heavy metal ions and / or sulfates and / or dyes from wastewater.

10. The application according to claim 9, characterized in that, The heavy metal ions mentioned are those that can react with S 2- The reaction produces precipitated heavy metal ions; the dye is an azo dye.

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