CN113388644A

CN113388644A - PDA protected electroactive biomembrane reduction Ag+Method for synthesizing AgNPs

Info

Publication number: CN113388644A
Application number: CN202110669703.3A
Authority: CN
Inventors: 王鑫; 廖承美; 赵倩
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2021-06-17
Filing date: 2021-06-17
Publication date: 2021-09-14
Anticipated expiration: 2041-06-17
Also published as: CN113388644B

Abstract

The invention discloses a method for reducing Ag by using polydopamine to protect an electroactive biomembrane⁺Method for synthesizing AgNPs. Adopts a single-chamber two-electrode system to acclimate an electroactive biomembrane and utilizes the oxidative self-polymerization capacity of dopamine to wrap a layer of polydopamine protective cover to resist Ag⁺The toxicity of AgNPs is imminent. First, a method for reducing Ag is constructed⁺Synthesis of electroactive biofilms of AgNPs: (1) building a single-chamber two-electrode microbial electrochemical system; (2) inoculating sewage or MFC reactor effluent to culture the electroactive biomembrane. Secondly, the electric active biological membrane is coated with polydopamine and is used for reducing Ag with different concentrations⁺And (5) synthesizing AgNPs. The present invention provides a new method to recover Ag in potentially useful AgNPs form and use effective PDA protection against Ag⁺Organisms of the reduction processToxicity. The technology is simple, economic and eco-friendly, can easily enlarge the yield and/or the production scale, and has good application prospects in the aspects of green synthesis of nano materials, biotoxicity wastewater treatment and sustainable biocatalysis.

Description

PDA protected electroactive biomembrane reduction Ag+Method for synthesizing AgNPs

Technical Field

The invention relates to the field of microbial electrochemical synthesis, in particular to a method for acclimating an anodic electroactive biomembrane (EABs) by a microbial electrochemical system wrapped by Polydopamine (PDA) and applying the method to silver ions (Ag)⁺) Research on reduction synthesis of nano silver particles (AgNPs).

Background

Metallic silver (Ag) and silver salts are widely used as effective antibacterial agents in various fields such as textile, medicine, daily chemical, special polymer materials, and industrial production, and have been used up to nowUsed for centuries. However, with the rapid development of modern industry, the discharge of Ag-containing consumer products from different fields into waste water poses a great threat to the stability of the ecosystem and to human health, since they are not as readily biodegradable as organic pollutants, and Ag, which has not been well treated, is also transported along the food chain at the nutrient level and accumulates in the biota. In addition, Ag is a precious metal and a rare precious resource, so that the recovery of Ag has more ecological and economic benefits than the removal of Ag, and the recovery of Ag has more ecological and economic benefits than the removal of Ag⁺Reduction to silver nanoparticles (AgNPs) is one of the most efficient and valuable recovery methods. Studies have shown that the biosynthesis of metal Nanoparticles (NPs) is an environmentally friendly metal recovery process that relies primarily on the respiration of active microorganisms. Many bacteria have been isolated and demonstrated to be able to reduce metal ions on the cell surface to form extracellular NPs, or to synthesize NPs by embedding metal ions inside the cell. Compared with microbial intracellular synthesis, extracellular synthesis is beneficial to large-scale production, and the downstream treatment process is simpler, so that the method has a wide application prospect. For example, Ag can be produced by Fe (III) -reducing bacteria Geobacter sp⁺Extracellular reduction to AgNPs, in which the electrons required for metal reduction come from oxidation of organic matter and then through Fe in the cytochrome²⁺Heme and Fe³⁺Heme interconversion transfers electrons from the inner membrane to the outer membrane of microorganisms, Ag⁺Reduced to AgNPs at the cell surface. It has been reported that such functional bacteria can also transfer electrons to electrodes, i.e., electrogenic bacteria.

For microbial extracellular synthesis of AgNPs, obtaining sufficient metal-reducing bacteria, such as electrogenic bacteria, is the first challenge because of their stringent growth conditions and difficulty in maintaining their dominance in the microbial community after long-term succession. Whereas the bioelectrochemical systems (bes) were reported to screen for abundant electrogenic bacteria from various environments (sediments, soils or wastewater) within a few days and for stable passage for many years, thus providing a useful and simple method for collecting and stabilizing electrogenic bacteria. The second challenge is Ag⁺And the biotoxicity of AgNPs. Ag in solution⁺He XinThe formed AgNPs can prevent the metabolism of microorganisms and inhibit the synthesis of the microorganisms. Previous studies have mostly focused on the reduction of Ag using suspended metal reducing bacteria⁺Forming AgNPs. However, since Extracellular Polymeric Substances (EPS) can accumulate on biofilms to protect them, microorganisms have higher tolerance to AgNPs than planktonic cells in the form of biofilms. Coincidently, BESs can form compact electroactive biofilms (EABs) on electrodes in the process of enriching electrogenic bacteria, and play a natural protection role. In addition, in 2017, a topic group reports that a biocompatible natural material Polydopamine (PDA) has a function equivalent to that of EPSs, and can provide an additional protective cover on the basis of the EPSs to help the electrogenic microorganisms to live in a severe environment.

Disclosure of Invention

The invention aims to solve the problems and provide Ag for effectively protecting electrochemically domesticated EABs and PDA (personal digital assistants) packages⁺The method for reducing the nano-material into AgNPs protects bacteria from being inhibited by toxic metal ions, and has wide application prospect in the aspects of green synthesis of nano-materials, biotoxicity wastewater treatment, sustainable biocatalysis and the like.

The purpose of the invention is realized by the following technical scheme: PDA-wrapped electroactive biomembrane reduction Ag⁺The method of synthesizing AgNPs employs single-chamber three-electrode BESs to provide a stable redox environment on the anode.

The domestication step of the electrochemical biological membrane comprises the following steps:

1) building of BESs for domesticating EABs

The reactor used was a cylindrical chamber 5cm long, 5cm in diameter, 100mL in effective volume, tightly sealed with a Teflon cap to maintain an anaerobic environment. Domesticating with two electrode system, anode being graphite rod, effective immersion area being 15cm². The cathode is a stainless steel mesh (1 cm. times.1 cm).

2) Domestication of EABs

The reactor inoculum source was the effluent of a Microbial Fuel Cell (MFC) operating stably (for more than 2 years) with sodium acetate as the carbon source. AnodeAfter biofilm formation, the inoculum was switched to a buffer containing 50mM phosphate buffer (PBS: Na)₂HPO₄，4.576g/L；NaH₂PO₄，2.132g/L；NH₄Cl, 0.31 g/L; KCl, 0.13g/L), 12.5mL/L trace minerals, 5mL/L vitamin solution and 1g/L sodium acetate. Applying 0.5-0.9V voltage between the cathode and anode, and exposing to N when the current is lower than 0.1mA and the culture solution is replaced₂To remove dissolved oxygen and record the process as a cycle. Mature electroactive biofilms (EABs) were formed after 3-5 cycles of sequencing batch operation. All reactors were run in a thermostatted incubator at 25. + -. 1 ℃.

3) The PDA wrapped EABs for Ag⁺And (3) reduction:

the packaging method for PDA was referred to a previous laboratory study. Mature EABs (acclimated for about 5 cycles) were immersed in polydopamine solution formed by oxidative auto-polymerization of 5g/L dopamine, and after 10min, the EABs were thoroughly washed with PBS to remove residual solution. EABs without PDA encapsulation were prepared and soaked in PBS buffer for 10min as a control to compare the protective effect of PDA on anode microorganisms. After the biomembrane recovers for 2 cycles, the biomembrane with or without PDA encapsulation is respectively soaked in 0.2g/L Ag and 1.0g/L Ag⁺Open-loop treatment in solution for 12 h. And then replacing fresh electrolyte, and connecting a potentiostat to record current.

Advantageous effects

1. Domestication of BESs to form EABs and Ag⁺Recovered in the form of AgNPs by reduction of the unique extracellular electron transfer capacity of the electrogenic bacteria, and EABs are used for Ag⁺Has stronger recovery capability. At a concentration of 0.2g/L and 1.0g/LAg⁺In solution of (A), EABs vs. Ag⁺The removal rate of the catalyst can reach 67 percent and 94 percent respectively.

PDA wrapped EABs better resist Ag⁺And extreme aggression of AgNPs, PDA to Ag⁺Has strong protection effect. In the presence of 0.2g/L and 1.0g/L Ag⁺In solution of (3), PDA encapsulated EABs vs Ag⁺The removal rate of the nano-particles can reach 79 percent and 99 percent respectively, and the biological reduction efficiency can be improved by 18 percent (0.2g/L) and 5 percent (1.0g/L) respectively by PDA (personal digital assistant) wrapping.

3. After a recovery period of time, PDA-encapsulated EABs activity was fully restored, indicating that the technique is not a disposable product. After one stimulation, the microorganism pairs Ag⁺No resistance developed. But with increased feedback of resistance to adverse environmental factors, subsequent Ag⁺The recovery period after recovery can be greatly shortened, which is an incomparable advantage of other technologies.

4. This study provides a method for recovering Ag⁺As a potentially useful method of AgNPs and using effective PDA protection against Ag⁺Biotoxicity of the reduction process. The technology is simple, economical and environment-friendly, and can easily enlarge the yield and/or the production. Has wide application prospect in the aspects of green synthesis of nano materials, biotoxic wastewater treatment, sustainable biocatalysis and the like.

Drawings

FIG. 1 schematic diagram of three-electrode single-chamber BESs bioreactor

Current densities (A) of the BESs in FIG. 2 include acclimation of mature electroactive biofilm, PDA encapsulation and Ag⁺Biological reduction process, and Ag⁺And (B) restoring the current for the first period. Cyclic Voltammograms (CVs) of different processes of BESs include mature biofilm (C), PDA-wrapped biofilm (D), Ag⁺A reduction prophase (E) and a recovery anaphase (F). The reference electrode was Ag/AgCl (4.0M KCl,0.201V vs. SHE).

FIG. 3 removal efficiency of Ag + from solution (A). Structural characterization and spectral identification of AgNPs deposited on the surface of an electroactive biomembrane, including Transmission Electron Microscope (TEM) image (B), high-resolution TEM image (C), XPS spectrum (D) and typical XRD spectrum (E) of coryneform bacteria on which AgNPs are deposited.

Detailed Description

The invention is further described below with reference to the following figures and specific examples.

Example 1

The bes were assembled as described previously, the EABs were acclimated, and the anode with a mature electroactive biofilm (approximately 5 cycles) was immersed in a polydopamine solution formed by oxidative auto-polymerization of 5g/L dopamine for 10min before the EABs were thoroughly washed with PBS to remove residual solution. EABs were prepared without PDA encapsulation and soaked in PBS buffer for 10min was used as a control to compare the protective effect of PDA on anode microorganisms. After 2 cycles of biofilm recovery, the biofilm without PDA encapsulation was soaked in 0.2g/L Ag⁺In the solution, the product is C-0.2. The open-circuit treatment was carried out for 12 hours each time. Then replacing the solution with new electrolyte, and connecting a potentiostat to record current; CV testing was performed on BESs at various stages of treatment, including mature biofilm (C), PDA-wrapped biofilm (D), Ag⁺Pre-reduction (E) and post-recovery (F), FIG. 2-C-0.2. Measuring residual Ag in solution by atomic absorption spectrometer⁺Calculating Ag within 12h⁺The reduction efficiency was 67%, fig. 3A.

Example 2

The bes were assembled as described previously, the EABs were acclimated, and the anode with a mature electroactive biofilm (approximately 5 cycles) was immersed in a polydopamine solution formed by oxidative auto-polymerization of 5g/L dopamine for 10min before the EABs were thoroughly washed with PBS to remove residual solution. EABs without PDA encapsulation were prepared and soaked in PBS buffer for 10min as a control to compare the protective effect of PDA on anode microorganisms. After 2 cycles of biofilm recovery, the biofilm without PDA encapsulation was soaked in 1.0g/L Ag⁺In the solution, the product is C-1.0. The open-circuit treatment was carried out for 12 hours each time. Then replacing the solution with new electrolyte, and connecting a potentiostat to record current; CV testing was performed on BESs at various stages of treatment, including mature biofilm (C), PDA-wrapped biofilm (D), Ag⁺Pre-reduction (E) and post-recovery (F), FIG. 2-C-1.0. Measuring residual Ag in solution by atomic absorption spectrometer⁺The reduction efficiency of silver over 12h was calculated to be 94%, fig. 3A.

Embodiment 3

The bes were assembled as described previously, the EABs were acclimated, and the anode with a mature electroactive biofilm (approximately 5 cycles) was immersed in a polydopamine solution formed by oxidative auto-polymerization of 5g/L dopamine for 10min before the EABs were thoroughly washed with PBS to remove residual solution. EABs without PDA encapsulation were prepared and soaked in PBS buffer for 10min as a control to compare the protective effect of PDA on anode microorganisms. After the biofilm recovers for 2 cycles, the biofilm with PDA encapsulation is soaked in 0.2g/L Ag⁺In the solution, the PDA-0.2 is obtained. The open-circuit treatment was carried out for 12 hours each time. Then replacing the solution with new electrolyte, and connecting a potentiostat to record current; CV testing was performed on BESs at various stages of treatment, including mature biofilm (C), PDA-wrapped biofilm (D), Ag⁺Pre-reduction (E) and post-recovery (F), FIG. 2-PDA-0.2. Measuring residual Ag in solution by atomic absorption spectrometer⁺The reduction efficiency of silver over 12h was calculated to be 79%, fig. 3A.

Example 4

The bes were assembled as described previously, the EABs were acclimated, and the anode with a mature electroactive biofilm (approximately 5 cycles) was immersed in a polydopamine solution formed by oxidative auto-polymerization of 5g/L dopamine for 10min before the EABs were thoroughly washed with PBS to remove residual solution. EABs without PDA encapsulation were prepared and soaked in PBS buffer for 10min as a control to compare the protective effect of PDA on anode microorganisms. After the biofilm recovered for 2 cycles, the biofilm with PDA encapsulation was soaked in 1.0g/L Ag⁺In the solution, the PDA-1.0 is obtained. The open-circuit treatment was carried out for 12 hours each time. Then replacing the solution with new electrolyte, and connecting a potentiostat to record current; CV testing was performed on BESs at various stages of treatment, including mature biofilm (C), PDA-wrapped biofilm (D), Ag⁺Pre-reduction (E) and post-recovery (F), FIG. 2-PDA-1.0. Measuring residual Ag in solution by atomic absorption spectrometer⁺The reduction efficiency of silver over 12h was calculated to be 99%, fig. 3A.

Example 5

Structural characterization and spectral characterization of the AgNPs deposited on the surface of the electroactive biofilm included Transmission Electron Microscopy (TEM) of the coryneform bacteria on which the AgNPs were deposited (fig. 3B), high resolution TEM image (fig. 3C), XPS spectrum (fig. 3D), and typical XRD spectrum (fig. 3E).

Claims

1. PDA-wrapped electroactive biomembrane reduction Ag⁺The method for synthesizing AgNPs is characterized by comprising the following steps:

1) reduction of Ag⁺Culture of electroactive biofilms for synthesis of AgNPs

The reactor is 3-9cm long and 3-6cm in diameterA cylindrical glass anaerobic chamber with the volume of 20-250 mL. Domesticating with two electrode system, anode being graphite electrode, effective immersion area being 1-30cm². The cathode is stainless steel mesh, the inoculation source is domestic sewage of a sewage treatment plant or effluent of a stably-running Microbial Fuel Cell (MFC), 0.5-0.9V voltage is applied between the cathode and the anode, and mature electroactive biofilms (EABs) are formed after the sequencing batch operation for 3-5 periods;

2) polydopamine (PDA) wrapped EABs reduced Ag⁺Synthetic AgNPs

Mature EABs were treated with polydopamine solution formed by oxidative auto-polymerization of 5-10 g/L dopamine, and after 10-30 min, the EABs were thoroughly washed with PBS to remove residual solution. After EABs successfully wrapped with PDA are re-inoculated into the reactor for 2-5 cycles, the reactor is soaked in 0.05-2.0g/L Ag⁺And opening the circuit in the solution for 6-24 h.

2. The PDA encapsulated electroactive biofilm reduced Ag of claim 1⁺The method for synthesizing AgNPs is characterized in that mature electroactive biomembranes (EABs) domesticated by a microbial electrochemical system are adopted to reduce Ag⁺The synthesized AgNPs have stronger reducing capability than suspended microorganisms.

3. The PDA encapsulated electroactive biofilm reduced Ag of claim 1⁺The method for synthesizing AgNPs is characterized in that mature electroactive biomembranes (EABs) coated by PDA are used for reducing Ag⁺Synthetic AgNPs with Ag stronger than simple EABs⁺AgNPs biotoxicity tolerance capability.

4. The PDA encapsulated electroactive biofilm reduced Ag of claim 1⁺A method for synthesizing AgNPs, characterized in that the method reduces Ag⁺The concentration of the complex is not limited to 0.05-2.0g/L, and the EABs with larger area cultured by the microbial electrochemical system through the amplification treatment can be applied to higher Ag⁺Recovering AgNPs with concentration. For different concentrations of Ag⁺Waste water, accessible adjusting reactor and cathode and anode electrode rulerAnd optimizing the recovery effect according to the experiment parameters such as cun and the like.