CN109721044B

CN109721044B - Preparation method and application of three-dimensional porous biochar derived from cones

Info

Publication number: CN109721044B
Application number: CN201811582877.0A
Authority: CN
Inventors: 颜美; 王睿文; 果崇申
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2018-12-24
Filing date: 2018-12-24
Publication date: 2022-02-15
Anticipated expiration: 2038-12-24
Also published as: CN109721044A

Abstract

The invention discloses a preparation method and application of three-dimensional porous biochar derived from cones, wherein the preparation method of the three-dimensional porous biochar comprises the following steps: (1) cleaning up impurities on the surfaces of the collected cones, and then drying the impurities; (2) and (3) carrying out high-temperature heat treatment carbonization on the dried cones in the atmosphere of inert gas to form the multi-heteroatom-doped biochar. The three-dimensional porous biochar derived from cones prepared by the method can be used as an anode of a microbial fuel cell. The invention obtains the multi-heteroatom doped porous biochar with a three-dimensional independent structure by carbonizing cones through simple heat treatment in an inert atmosphere. The porous biochar derived from cones serving as an independent anode can quickly start a microbial fuel cell, can obtain voltage and power density which are obviously higher than those of commercial three-dimensional materials, and has the advantages of wide sources, low price, simple preparation method and capability of realizing quantitative production.

Description

Preparation method and application of three-dimensional porous biochar derived from cones

Technical Field

The invention belongs to the fields of environment, materials and energy, and relates to a preparation method of three-dimensional porous biochar and application of the three-dimensional porous biochar as an anode of a microbial fuel cell.

Background

With the development of modern society, more and more waste water is generated. However, the conventional sewage treatment process is a high-energy-consumption process, and a large amount of chemical energy is stored in organic matters of the wastewater, so that the process has economic and ecological benefits if the energy in the wastewater can be recycled. Microbial Fuel Cells (MFCs) are an emerging technology that can regenerate wastewater into an energy source. The microorganisms generate electrons by using organic matters, and the electrons reach the cathode through an external circuit under the drive of potential difference so as to generate current. The anode material is the most important part of the MFC, and complex interaction between solution, bacteria and an electrode exists on the solid-liquid interface of the anode: the surface properties and hydrophobicity of the anode material affect the adhesion of bacteria and the composition of the anode microbial community; the specific surface area affects the total biomass attached; the pore structure affects the transport and diffusion of substrates and products; the electrochemical properties of the material directly affect the electron transfer between the bacterial electrodes and thus the performance of the battery. Therefore, the design of the anode material is important as an important component of MFC. Current commercial materials generally have a small specific surface area and thus can carry a low amount of biomass; biocompatibility is general and therefore priming is slow; the impedance is large and the power density is therefore limited. In summary, it is imperative to develop new MFC battery anodes that are inexpensive, easy to manufacture, and have excellent performance.

Disclosure of Invention

Aiming at the problems, the invention provides a preparation method and application of three-dimensional porous biochar derived from cones. The invention obtains the multi-heteroatom doped porous biochar with a three-dimensional independent structure by carbonizing cones through simple heat treatment in an inert atmosphere. The porous biochar derived from cones serving as an independent anode can quickly start a microbial fuel cell, can obtain voltage and power density which are obviously higher than those of commercial three-dimensional materials, and has the advantages of wide sources, low price, simple preparation method and capability of realizing quantitative production.

The purpose of the invention is realized by the following technical scheme:

a preparation method of three-dimensional porous biochar derived from cones comprises the following steps:

(1) cleaning up impurities on the surfaces of the collected cones, and then drying the impurities;

(2) and (3) carrying out high-temperature heat treatment carbonization on the dried cones in the atmosphere of inert gas to form multi-heteroatom-doped biochar which has an independent three-dimensional porous structure and certain mechanical strength.

The three-dimensional porous biochar derived from cones prepared by the method can be used as an anode of a microbial fuel cell.

In the present invention, the cones are hard wood cones of Pinaceae or Cupressaceae or other gymnosperms.

In the invention, the drying mode of the cones is normal temperature drying or vacuum drying.

In the invention, before the cones are dried, the cones can be soaked in a precursor solution of iron salt (such as ferric chloride) or zinc salt (such as zinc acetate) for 1-3 hours to improve biocompatibility.

In the invention, the high-temperature heat treatment carbonization temperature is 700-1000 ℃, and the reaction time is 2-6 h.

Compared with the prior art, the invention has the following advantages:

1. in the invention, the cones are carbonized through simple heat treatment in the inert gas atmosphere, so that the multi-atom doped porous biochar with an independent three-dimensional structure is obtained. The micron-sized pore canal of the cone is still reserved after carbonization, so that the cone has a larger specific surface area and is beneficial to the growth of microorganisms. The main component of the cone is carbon, and meanwhile, the cone contains various elements such as nitrogen, phosphorus, sulfur and the like, and the cone is doped in the biochar in situ in the carbonization process, so that the attachment of microorganisms is facilitated, and the Extracellular Electron Transfer (EET) process can be promoted.

2. The method is simple and easy to implement, the raw materials are sufficient and widely available, the raw materials are not well utilized in other commercialization at present, meanwhile, the prepared anode can accelerate the starting of the microbial fuel cell and promote EET, higher voltage and power density are obtained, under the condition of no microorganism loading, the electron transfer impedance is as low as 2.23 omega, the electron transfer impedance after the biological membrane loading is lower and is 1.39 omega, and the conductivity and the extracellular electron transfer capability of the biological membrane attached to the surface of the anode are higher.

3. The cone-derived three-dimensional porous biochar prepared by the method has a developed pore structure and good biocompatibility, has good electrochemical activity when being used as an electrode, can be used as an anode of various microbial fuel cells, and is suitable for the adhesion growth of mixed flora and various extracellular electricigen pure bacteria.

4. The invention obtains three-dimensional porous biochar as an MFC anode through heat treatment of the cones, and the cones are very suitable to be used as anode materials of microbial fuel cells due to the characteristics of rich pore passages of the cones, better biocompatibility brought by heteroatom doping, lower impedance of the biochar, independent three-dimensional structure and the like, and can improve the performance of the microbial fuel cells: reduce the electron transfer impedance of the anode, accelerate the start of the microbial fuel cell and improve the output power.

Drawings

FIG. 1 is an X-ray diffraction pattern of porous biochar derived from pinus tabulaeformis (biochar obtained by carbonizing cones at 800 deg.C, 900 deg.C, 1000 deg.C for ST-800, ST-900, ST-1000, respectively);

FIG. 2 is an X-ray photoelectron spectrum of porous biochar formed by 900 ℃ carbonized pinus tabulaeformis cones;

FIG. 3 is a scanning electron microscope image of porous biochar formed from 900 ℃ carbonized pine cones;

FIG. 4 is a scanning electron microscope image of biofilm attached to porous biochar formed from 900 ℃ carbonized pine cones;

FIG. 5 is a graph of AC impedance after attachment of biofilm to the prepared anode (biochar obtained by carbonizing strobilus Pini at 800 deg.C, 900 deg.C, 1000 deg.C, ST-800, ST-900, ST-1000, respectively, and CF being a commercial material carbon felt);

FIG. 6 is a voltage curve for battery start-up after inoculation of prepared anode with microorganisms (ST-800, ST-900, ST-1000 are biochar obtained by carbonizing strobilus Pini at 800 deg.C, 900 deg.C, 1000 deg.C, respectively, and CF is a commercial material carbon felt);

FIG. 7 is a power density curve of an assembled battery (biochar obtained by carbonizing strobilus pini at 800 deg.C, 900 deg.C, 1000 deg.C, respectively, ST-800, ST-900, ST-1000).

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Example 1:

(1) and cleaning impurities on the surface of the collected pine cone, and drying for 12 hours at room temperature.

(2) And (3) placing the dried Chinese pine cones into a tube furnace, heating to 800 ℃ at a heating rate of 1.5 ℃/min in the nitrogen atmosphere, maintaining for 2h, naturally cooling to room temperature, and taking out the Chinese pine cones to obtain the three-dimensional porous biochar material.

(3) The three-dimensional porous biochar material is washed in a water and ethanol solution for a plurality of times and wound by using a titanium wire to be used as an MFC anode material, and the anode material is suitable for microbial fuel cells inoculated with pure bacteria and mixed bacteria and is not limited by the configuration of the cell and a cathode-anode electrolyte.

Example 2:

this example differs from example 1 in that: drying the cleaned cones in vacuum for 30 min, putting the dried cones into a tube furnace, heating to 900 ℃ at a heating rate of 1.5 ℃/min in the nitrogen atmosphere, maintaining for 4h, naturally cooling to room temperature, and taking out.

Example 3:

this example differs from example 1 in that: the temperature rise rate was 5 ℃/min.

Example 4:

this example differs from example 1 in that: the inert gas chosen was argon.

Example 5:

this example differs from example 1 in that: the heat treatment time is 6 h.

Example 6:

this example differs from example 1 in that: before the cones were dried and carbonized, the cones were soaked in a 0.1M ferric nitrate solution for 2 h.

Example 7:

this example differs from example 1 in that: the temperature was raised to 1000 ℃.

Example 8:

this example differs from example 1 in that: the strobilus Pini is strobilus Pini.

The method adopts a RIGAKU D/Max 3400X-ray diffractometer to analyze the crystal structure and phase of a sample, adopts a PHI 5700 ESCA X-ray photoelectron spectrometer and a Hitachi S-4800 Scanning Electron Microscope (SEM) to observe the morphology and the pore structure of the porous biochar, and adopts an SI1287 electrochemical workstation of AMETEK Solartron and an SI1260 impedance meter to measure the alternating current impedance of an electrode; and a Keithley 2700 type data acquisition unit is adopted for acquiring and recording the voltage of the battery. The results are shown in FIGS. 1 to 7.

As can be seen from fig. 1: the pine cone carbonized at different temperatures is 22^oAnd 44^oTwo broad peaks respectively correspond to (002) crystal faces and (100) crystal faces of carbon, which indicates that the pinus tabulaeformis cones after heat treatment are partially graphitized, so that the conductivity is improved; as shown in FIG. 2, the 900 ℃ carbonized pinus massoniana cones successfully realize the doping of various heteroatoms, so that the pinus massoniana cones have better biocompatibility compared with a simple carbon material, wherein the N doping is favorable for improving the extracellular electron transfer rate, and the existence of functional groups containing P and O is favorable for increasing the hydrophilicity of the material and the attachment of microorganisms, thereby further promoting the EET process; as can be seen from FIG. 3, the carbonized pine cone has micron-sized macroporous channels abundant insideThe device is suitable for the growth of the biological membrane and the transmission of electrolyte without worrying about the blockage of the pore channel caused by the attachment of the biological membrane; as can be seen from FIG. 4, the thick biofilm is attached to the inner wall of the carbonized pinecone pore canal, which shows that the electrode has good biocompatibility and is easy for the attachment of microorganisms; as can be seen from fig. 5, the electron transfer resistance of the carbonized pinus tabulaeformis after the growth of the biofilm is lower than that of the commercial material carbon felt (9.39 Ω), wherein the temperature of 900 ℃ is the lowest and is only 1.39 Ω, which indicates that the biofilm attached to the surface of the carbonized pinus tabulaeformis at 900 ℃ has good conductivity, faster extracellular electron transfer rate and excellent electrochemical performance; as can be seen from fig. 6, the pine cone is used as the anode, the voltage of the battery after inoculation is rapidly increased, the battery is started obviously faster than that of a carbon felt anode, the carbon felt anode needs 8 days to start, and the fastest starting time of the carbonized pine cone only needs 3 days, which indicates that the surface is easy to be attached by electrogenic bacteria; as can be seen from FIG. 7, the carbonized pine cones used as anodes had the highest power density of 10.88W/m at 900 ℃ when carbonized³The volume of the anode chamber is 100 mL which is 2.2 times of the electricity generation power of the carbon felt anode microbial fuel cell, which shows that the carbonized pinus tabulaeformis has excellent performance as the MFC anode, the manufacturing cost is low, the manufacturing is simple, the quantitative production can be realized, and the application potential in the field of microbial fuel cells is huge.

Claims

1. The application of the three-dimensional porous biochar derived from cones as the anode of the microbial fuel cell is characterized in that the preparation method of the three-dimensional porous biochar comprises the following steps:

(2) and carrying out high-temperature heat treatment carbonization on the dried cones in the atmosphere of inert gas to form multi-heteroatom-doped biochar, wherein the high-temperature heat treatment carbonization temperature is 700-1000 ℃, and the reaction time is 2-6 h.

2. Use of the cone-derived three-dimensional porous biochar as anode for microbial fuel cells according to claim 1, characterized in that the cones are hard wood cones.

3. The use of the cone-derived three-dimensional porous biochar as a microbial fuel cell anode according to claim 1, characterized in that the cone is dried at normal temperature or in vacuum.

4. The application of the cone-derived three-dimensional porous biochar as the anode of the microbial fuel cell according to claim 1 or 3, wherein the cones are soaked in a solution of iron salt or zinc salt for 1-3 hours before being dried.