CN104450790A - Biological method of preparing p-ferrite-modified n-hematite heterostructure - Google Patents

Abstract

The present invention relates to a biological method for preparing p-ferrite modified n-hematite heterostructure by using Shewanella putrefaciens MR-1, the method develops p-type iron with pn junction and ohmic layer through biosynthesis technology The ferrite-n-type hematite heterostructure is divided into two steps. The first step is to prepare A-Zn (A=Mg, Mn or Ni) modified goethite (FeOOH) with a particle size of about 50 nm by peptization and reflux technology. Powder; the second step: cultivating Shewanella putrefaciens MR-1 under anaerobic conditions at room temperature to reduce part of the ferric iron to obtain (A-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction. Compared with the existing technology, this method has the advantages of simple process, less pollution, low energy consumption, easy scale-up, high recovery rate, etc. The (A-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction obtained by this method Low surface defects, less agglomeration, uniform particle size, and good photothermal and magnetic properties.

Description

A biological method for preparing p-ferrite modified n-hematite heterostructure

technical field

The invention relates to a biological method for preparing p-ferrite modified n-hematite heterogeneous structure by utilizing Shewanella putrefaciens MR-1, which belongs to the field of inorganic materials.

Background technique

The n-type semiconductor hematite (Fe ₂ O ₃ ; band gap: 2eV) is an important semiconductor material in the field of catalysts, which has been applied to photoelectric materials, photocatalysis and magnetic storage media. However, poor carrier mobility (0.2cm ² ·V ^-1 ·s ^-1 ) and ultrafast recombination of photogenerated carriers (~10ps) limit its large-scale application. The current research on surface design and preparation of controllable Fe ₂ O ₃ -based heterostructures can significantly improve the efficiency of photogenerated electrons and holes, and emerge new properties that the original components do not have in physical mixing. For example, Fe ₂ O ₃ is used to conjugate p-type spinel ferrite (band gap: 1.9-2.7eV) to form a pn structure. The incorporation of magnetic nanocrystals can not only enhance the photocatalytic efficiency, but also recover the catalysts through magnetic separation under mild magnetic field, which is very attractive for photocatalytic applications. In 2008, Pailhe' et al. reported the special magnetic and photoluminescent properties of zinc-doped ferrites. Subsequently, the research groups of Lee, Sutka, Klimkiewicz and others successively prepared the p-type ferrite-n-type hematite heterostructure by means of spray pyrolysis deposition, one-step chemical synthesis and liquid phase thermal synthesis, and reported that the original components New parameters such as magnetism, surface photovoltage, and hollow structure that do not exist. Therefore, pn-type ceramics are considered as novel composite materials for exploring various nanostructures of iron-rich oxides, which will facilitate the optoelectronic properties of the multifunctional materials for application integration.

It is difficult to avoid the surface defects caused by high temperature annealing by traditional physical or chemical methods, therefore, new researches focus on the preparation and biosynthesis of said nanomaterials. Recently, researchers have studied the synthesis of nano-scale spinel using different microorganisms. The specific reaction process is as follows: lactic acid (Lactate ^- ) + 4Fe ³⁺ + 2H ₂ O→1,1-diethoxyethane (acetat ^- )+HCO ^- +4Fe ²⁺ +5H ⁺ ; A ²⁺ +2Fe(OH) ₃ → AFe ₂ O ₄ +2H ₂ O+2H ⁺ (A=Fe, Mg, Zn, Mn, Ni, Ca, etc.) .

Contents of the invention

The purpose of the present invention is to provide a biological method for preparing p-ferrite-modified n-hematite heterostructure, which develops a p-type ferrite-n-type red hematite with pn junction and ohmic layer through biosynthesis technology. The heterogeneous structure of iron ore is carried out in two steps. The first step: A-Zn (A=Mg, Mn or Ni) modified goethite (FeOOH) powder with a particle size of about 50nm is prepared by peptizing reflux technology; the second step: Shewanella putrefaciens MR-1 was cultured under anaerobic conditions at room temperature to reduce part of ferric iron to obtain (A-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction. Compared with the prior art, the method has the advantages of simple process, little pollution, low energy consumption, easy amplification, high recovery rate and the like. The (A-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction obtained by the method has low surface defects, less agglomeration, uniform particle size and good photothermomagnetic properties.

A biological method for preparing p-ferrite modified n-hematite heterostructure according to the present invention, the method uses Shewanella putrefaciens MR-1 to prepare p-ferrite modified n-hematite heterostructure The specific operation is carried out according to the following steps:

a. The raw material MgCl ₂ , MnCl ₂ or NiCl ₂ and ZnCl ₂ and FeCl ₃ · 6H ₂ O in molar ratio Mg ²⁺ , Mn ²⁺ or Ni ²⁺ : Zn ²⁺ : Fe ³⁺ =0.5:0.5:2 Add to the nitric acid aqueous solution with a pH value of 2, reflux at a temperature of 85°C for 2 hours, let stand, and dry at a vacuum temperature of 50°C for 20 hours to obtain Mg ²⁺ , Mn ²⁺ or Ni ²⁺ , and Zn ²⁺ modified FeOOH powder body;

b. Cultivate 30g·L ^-1 of Shewanella putrefaciens MR-1 in liquid tryptone soybean broth medium to obtain a cell concentration of 2.3×10 ⁸ cells·ml ^-1 , and centrifuge at a temperature of 5°C under freezing conditions Shewanella putrefaciens MR-1 strains, added to the mineralization medium, and then added the modified FeOOH powder obtained in step a to prepare Mg ²⁺ , Mn ²⁺ or Ni ²⁺ with a concentration of 90mM, and Zn ²⁺ modified FeOOH solution, adjust the pH value of the solution to 6-8, and simultaneously add 1,4-piperazine diethanesulfonic acid and anthraquinone 2,6-bissulfonate to relieve the contact of cells with FeOOH solution, Accelerate the reduction reaction of Fe ³⁺ ;

c. Seal the reaction solution in step b anaerobically, store it in the dark at a temperature of 30°C for 45 days, centrifuge it, and dry it under vacuum at a temperature of 70°C for 48 hours to obtain a p-ferrite-modified n-hematite heterostructure.

The mineralization medium composition in step b is (NH ₄ ) ₂ SO ₄ 9.0mM, K ₂ HPO ₄ 5.7mM, KH ₂ PO ₄ 3.3mM, NaHCO ₃ 2.0mM, MgSO ₄ 7H ₂ O 1.01mM, CaCl _{( _ _ _ _ _ _ _ _} SO ₄ ) ₂ 5.0 μM, Na ₂ MoO ₄ 3.87 μM, Na ₂ SeO ₄ 1.5 μM, MnSO ₄ 1.26 μM, ZnSO ₄ 1.04 μM, CuSO ₄ 0.2 μM, arginine 20 mg·L ^-1 , glutamic acid 20 mg· L ^-1 and serine 20mg·L ^-1 .

The biological method for preparing p-ferrite modified n-hematite heterogeneous structure according to the present invention, the involved Shewanella putrefaciens MR-1 (Gram-negative, facultative anaerobic bacteria) In order to purchase the product, provided by the research group of Dong Hailiang, University of Miami, China University of Geosciences, and Southwest University of Science and Technology, the genome of Shewanella putrefaciens MR-1 is cytochrome 42c, and the cytochrome of the extracellular matrix (trypsin pigment A-OmcA , trypsin C-MtrC and trypsin B-MtrB) and iron hydrogenase are localized at different locations in the inner and outer membranes, forming a "molecular wire" configuration that provides insoluble electron acceptors and electron movement in and out of the cell access. These genomic sequences provide a key step in the reduction (and bioremediation) of divalent metal ions and provide a new avenue for the study of the modification of _Fe2O3 with divalent transition metal ions on the _surface .

According to the biological method for preparing p-ferrite modified n-hematite heterogeneous structure of the present invention, the liquid TSB medium involved in the method is tryptone soybean broth medium.

Description of drawings

Fig. 1 is the powder X-ray diffraction peak shape of the final product obtained by the present invention through 45 days of MR-1 microbial mineralization treatment, wherein -□-represents the phase of Fe ₃ O ₄ , the phase of -▽-Fe ₂ O ₃ , ( 1) XRD pattern of Fe ₃ O ₄ and Fe ₂ O ₃ ; (2) XRD pattern of Zn-Mg co-doped Fe ₃ O ₄ -Fe ₂ O ₃ ; (3) Zn-Mn co-doped Fe XRD pattern of ₃ O ₄ -Fe ₂ O ₃ ; (4) XRD pattern of Zn-Ni co-doped Fe ₃ O ₄ -Fe ₂ O ₃ ;

Fig. 2 is the powder Raman spectrum of the final product that the present invention obtains through microbial mineralization treatment, wherein Represents the Raman spectrum of Fe ₃ O ₄ -Fe ₂ O ₃ ; Raman spectrum representing Zn-Mg co-doped FeFe ₃ O ₄ -Fe ₂ O ₃ ; Represents Zn-Mn co-doped Fe ₃ O ₄ -Fe ₂ O ₃ Raman spectrum; Represents Zn-Ni co-doped Fe ₃ O ₄ -Fe ₂ O ₃ Raman spectrum; it can be seen from the figure that the reactant is AZnFe ₂ O ₄ composite Fe ₂ O ₃ powder (Fe-O peak: 200～300cm ^{- 1} ), compared with the original reactants, the composite phase contains Fe ²⁺ -Fe ³⁺ composite bonds, which are the main reaction sites of the pn junction.

Fig. 3 is the ultraviolet-visible _diffuse reflectance DRS figure of (A-Zn) _Fe2O4 - _Fe2O3 heterojunction obtained through microbial treatment in the present _invention , wherein Represents the UV-Vis diffuse reflectance diagram of Zn-Mn co-doped Fe ₃ O ₄ -Fe ₂ O ₃ ; Represents the UV-Vis diffuse reflectance diagram of Zn-Mg co-doped Fe ₃ O ₄ -Fe ₂ O ₃ ; Represents the UV-Vis diffuse reflectance diagram of Zn-Ni co-doped Fe ₃ O ₄ -Fe ₂ O ₃ ; Represents the UV-Vis diffuse reflectance diagram of Fe ₃ O ₄ -Fe ₂ O ₃ ; it can be seen from the figure that the product belongs to the pn-type heterojunction structure, the p-type energy gap is 1.42-1.84eV, and the n-type energy gap is 2.46 ~2.69eV. Particularly noteworthy is the emergence of a transition gap (2.76eV) in the (Ni-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction, which can serve as a transit region for efficient electron and efficient hole transport. Compared with conventional pn junctions, the photoelectron transport and capture efficiency is faster.

Detailed ways

Example 1

a. The molar ratio is Mg ²⁺ : Zn ²⁺ : Fe ³⁺ = 0.5: 0.5: 2. Weigh the raw materials MgCl ₂ , ZnCl ₂ and FeCl ₃ ·6H ₂ O, add an aqueous solution of nitric acid with a pH value of 2, and Reflux at 85°C for 2 hours, and the reactant will undergo a peptization reflux reaction, and the solution will change from colorless and transparent to a khaki suspension. After 2 hours of reaction, the solid-liquid layer will be separated after standing, and a khaki powder product will be obtained. After washing with water until the by-product ammonium chloride is removed, dry at a vacuum temperature of 50°C for 20 hours to obtain Mg ²⁺ and Zn ²⁺ modified FeOOH powder;

b. Cultivate 30g·L ^-1 Shewanella putrefaciens MR-1 in liquid tryptone soybean broth medium to obtain a cell concentration of 2.3×10 ⁸ cells·ml ^-1 , and centrifuge at 5°C under freezing conditions Putting Shewanella putrefaciens MR-1 strains, adding Shewanella putrefaciens MR-1 strains to the mineralization medium as (NH ₄ ) ₂ SO ₄ 9.0mM, K ₂ HPO ₄ 5.7mM, KH ₂ PO ₄ 3.3mM, NaHCO ₃ 2.0mM, MgSO ₄ 7H ₂ O 1.01mM, CaCl ₂ 2H _{2 O} 0.485mM, sodium ferric EDTA 67.2μM, H ₃ BO ₃ 56.6μM, NaCl 10.0μM, FeSO ₄ 7H ₂ O 5.4 μM, CoSO ₄ 5.0 μM, Ni(NH ₄ ) ₂ (SO ₄ ) ₂ 5.0 μM, Na ₂ MoO ₄ 3.87 μM, Na ₂ SeO ₄ 1.5 μM, MnSO ₄ 1.26 μM, ZnSO ₄ 1.04 μM, CuSO ₄ 0.2μM, arginine 20mg·L ^-1 , glutamic acid 20mg·L ^-1 and serine 20mg·L ^-1 , and then add the modified FeOOH powder obtained in step a to prepare Mg with a concentration of 90mM ²⁺ -Zn ²⁺ modified FeOOH solution, adjusted the pH value to 8, and added 1,4-piperazine diethanesulfonic acid (PIPES) and anthraquinone 2,6-disulphonic acid salt (AQDS) at the same time, relieved the cell and The contact of FeOOH solution accelerates the reduction reaction of Fe ³⁺ ;

c. Seal the reaction solution in step b anaerobically, and store it in the dark for 45 days at a temperature of 30°C. The reactant will undergo a microbial Fe ³⁺ -Fe ²⁺ reduction reaction, and the surface color will change from earthy yellow powder to yellowish brown suspension. Cloudy liquid, dark brown powder was obtained after the reaction, centrifuged, and dried under vacuum at 70°C for 48 hours to obtain (Mg-Zn)Fe ₂ O ₄ -Fe ₂ O ₃ heterojunction with a recovery rate of 88.57%.

Example 2

a. The molar ratio is Mn ²⁺ : Zn ²⁺ : Fe ³⁺ = 0.5: 0.5: 2. Weigh the raw materials MnCl ₂ , ZnCl ₂ and FeCl ₃ ·6H ₂ O, add them into the nitric acid aqueous solution with a pH value of 2, and Peptization and reflux at 85°C for 2 hours, the solution changed from colorless and transparent to a light yellow suspension. After 2 hours of reaction, the solid-liquid layer was separated and dried at a vacuum temperature of 50°C for 20 hours to obtain brown-yellow Mn ²⁺ -Zn ²⁺ modified FeOOH powder;

b. Cultivate 30g·L ^-1 of Shewanella putrefaciens MR-1 in liquid tryptone soybean broth medium to obtain a cell concentration of 2.3×10 ⁸ cells·ml ^-1 , and centrifuge at a temperature of 5°C under freezing conditions Putting Shewanella putrefaciens MR-1 strains, adding Shewanella putrefaciens MR-1 strains to the mineralization medium as (NH ₄ ) ₂ SO ₄ 9.0mM, K ₂ HPO ₄ 5.7mM, KH ₂ PO ₄ 3.3mM, NaHCO ₃ 2.0mM, MgSO ₄ 7H ₂ O 1.01mM, CaCl ₂ 2H _{2 O} 0.485mM, sodium ferric edetate 67.2μM, H ₃ BO ₃ 56.6μM, NaCl 10.0μM, FeSO ₄ 7H ₂ O 5.4 μM, CoSO ₄ 5.0 μM, Ni(NH ₄ ) ₂ (SO ₄ ) ₂ 5.0 μM, Na ₂ MoO ₄ 3.87 μM, Na ₂ SeO ₄ 1.5 μM, MnSO ₄ 1.26 μM, ZnSO ₄ 1.04 μM, CuSO ₄ 0.2 μM, 20 mg·L ^-1 of arginine, 20 mg·L ^-1 of glutamic acid and 20 mg·L ^-1 of serine, and then add the modified FeOOH powder obtained in step a to prepare Mn ² with a concentration of 90 mM ⁺ -Zn ²⁺ modified FeOOH solution, adjusted the pH value to 7, and added 1,4-piperazine diethanesulfonic acid (PIPES) and anthraquinone 2,6-disulphonic acid salt (AQDS) at the same time to relieve the cells from interacting with FeOOH The contact of the solution accelerates the reduction reaction of Fe ³⁺ ;

c. Seal the reaction solution in step b anaerobically, and store it in the dark at a temperature of 30°C for 45 days. The surface color of the reactant changes from a khaki powder to a yellowish-brown suspension. After the reaction, a reddish-brown powder is obtained, centrifuged, Drying at a vacuum temperature of 70° C. for 48 hours to obtain a (Mn—Zn)Fe ₂ O ₄ —Fe ₂ O ₃ heterojunction with a recovery rate of 94.28%.

Example 3

a. The molar ratio is Ni ²⁺ : Zn ²⁺ : Fe ³⁺ = 0.5: 0.5: 2. Weigh the raw materials NiCl ₂ , ZnCl ₂ and FeCl ₃ ·6H ₂ O, add them into the nitric acid aqueous solution with a pH value of 2, and Refluxed at 85°C for 2 hours, the solution changed from colorless and transparent to a light yellow-green suspension. After standing still, the solid-liquid layer was separated, and dried at a vacuum temperature of 50°C for 20 hours to obtain light yellow Ni ²⁺ -Zn ²⁺ modified FeOOH powder;

Cultivate 30g·L ^-1 Shewanella putrefaciens MR-1 in liquid tryptone soybean broth medium to obtain a cell concentration of 2.3×10 ⁸ cells·ml ^-1 , centrifuge putrefaction bacteria at 5°C Warnerella MR-1 strains, put Shewanella putrefaciens MR-1 strains into the mineralization medium as (NH ₄ ) ₂ SO ₄ 9.0mM, K ₂ HPO ₄ 5.7mM, KH ₂ PO ₄ 3.3mM , NaHCO ₃ 2.0mM, MgSO ₄ 7H ₂ O 1.01mM, CaCl ₂ 2H _{2 O} 0.485mM, sodium ferric EDTA 67.2μM, H ₃ BO ₃ 56.6μM, NaCl 10.0μM, FeSO ₄ 7H ₂ O 5.4 μM, CoSO ₄ 5.0 μM, Ni(NH ₄ ) ₂ (SO ₄ ) ₂ 5.0 μM, Na ₂ MoO ₄ 3.87 μM, Na ₂ SeO ₄ 1.5 μM, MnSO ₄ 1.26 μM, ZnSO ₄ 1.04 μM, CuSO ₄ 0.2 μM, 20mg·L ^{-1 of} arginine, 20mg·L ^-1 of glutamic acid and 20mg·L ^-1 of serine, and then add the modified FeOOH powder obtained in step a to prepare Ni ²⁺ - with a concentration of 90mM Zn ²⁺ modified FeOOH solution, adjusted the pH value to 6, and added 1,4-piperazine diethanesulfonic acid (PIPES) and anthraquinone 2,6-disulphonate (AQDS) at the same time to relieve the cells from the FeOOH solution. Contact, accelerate the reduction reaction of Fe ³⁺ ;

c. Seal the reaction solution in step b anaerobically, and store it in the dark at a temperature of 30°C for 45 days. The surface color of the reactant changes from a khaki powder to a yellow-green suspension. After the reaction, a dark brown powder is obtained, centrifuged, Dry at 70° C. for 48 hours under vacuum to obtain (Ni—Zn)Fe ₂ O ₄ —Fe ₂ O ₃ heterojunction with a recovery rate of 87.14%.

Claims (2)

1. prepare the biological method that p-ferrite modifies n-rhombohedral iron ore heterojunction structure, it is characterized in that the method utilizes Shewanella putrefaciens MR-1 to prepare p-ferrite and modifies n-rhombohedral iron ore heterojunction structure, concrete operations follow these steps to carry out:

A, by raw material MgCl ₂, MnCl ₂or NiCl ₂with ZnCl ₂and FeCl ₃6H ₂o is Mg in molar ratio ²⁺, Mn ²⁺or Ni ²⁺: Zn ²⁺: Fe ³⁺=0.5: 0.5: 2, adding pH value is in the aqueous nitric acid of 2, and temperature 85 DEG C backflow 2 hours, leave standstill, true temp 50 DEG C of dryings 20 hours, obtained Mg ²⁺, Mn ²⁺or Ni ²⁺, and Zn ²⁺the FeOOH powder modified;

B, by 30gL ^-1shewanella putrefaciens MR-1 is in liquid pancreas peptone soybean broth culture medium culturing, and obtaining cell concn is 2.3 × 10 ⁸cells/ml ^-1, under temperature 5 DEG C of freezing conditions centrifugal go out Shewanella putrefaciens MR-1 bacterial classification, then join in Mineralized Culture base by Shewanella putrefaciens MR-1 bacterial classification, the FeOOH powder then adding the modification obtained by step a is mixed with the Mg that concentration is 90 mM ²⁺, Mn ²⁺or Ni ²⁺, and Zn ²⁺the FeOOH solution modified, regulator solution pH value is 6-8, and adds Isosorbide-5-Nitrae-piperazine two ethyl sulfonic acid and anthraquinone 2,6-disulfonate simultaneously, alleviates the contact of cell and FeOOH solution, accelerates Fe ³⁺reduction reaction;

C, by reaction solution anaerobic sealing of step b, keep in Dark Place 45 days under temperature 30 DEG C of conditions, centrifugal, true temp 70 DEG C of dryings 48 hours, obtain p-ferrite and modify n-rhombohedral iron ore heterojunction structure.

2. method according to claim 1, is characterized in that the Mineralized Culture base component in step b is (NH ₄) ₂sO ₄9.0 mM, K ₂hPO ₄5.7 mM, KH ₂pO ₄3.3 mM, NaHCO ₃2.0 mM, MgSO ₄7H ₂o 1.01 mM, CaCl ₂2H ₂o 0.485 mM, Sytron 67.2 μMs, H ₃bO ₃56.6 μMs, NaCl 10.0 μMs, FeSO ₄7H ₂o 5.4 μMs, CoSO ₄5.0 μMs, Ni (NH ₄) ₂(SO ₄) ₂5.0 μMs, Na ₂moO ₄3.87 μMs, Na ₂seO ₄1.5 μMs, MnSO ₄1.26 μMs, ZnSO ₄1.04 μMs, CuSO ₄0.2 μM, arginase 12 0 mgL ¹, L-glutamic acid 20 mgL ¹with Serine 20 mgL ¹.