CN111389351B

CN111389351B - CuFeO 2/biochar composite magnetic material and preparation method thereof

Info

Publication number: CN111389351B
Application number: CN202010075203.2A
Authority: CN
Inventors: 辛言君; 陈清华; 邓智翰; 阎清华; 胡春光
Original assignee: Qingdao Agricultural University
Current assignee: Qingdao Agricultural University
Priority date: 2020-01-22
Filing date: 2020-01-22
Publication date: 2022-05-17
Anticipated expiration: 2040-01-22
Also published as: CN111389351A

Abstract

The invention relates to CuFeO₂A biochar/biochar composite magnetic material is prepared from ginger stalk through carbonizing, and Fe³⁺Salt and Cu²⁺Mixing salt in water, continuously adding a strong base solution under the stirring condition, transferring the solution into a hydrothermal reaction kettle, carrying out hydrothermal reaction at a certain temperature, naturally cooling a hydrothermal product, washing with deionized water, carrying out suction filtration, and drying to constant weight to obtain CuFeO₂Biological carbon composite magnetic material. CuFeO obtained by the invention₂Biological carbon composite material ratioThe surface area is large, the magnetic performance is certain, the preparation method does not need an additional reducing agent, the cost is low, the period is short, the purity is high, and the preparation method is suitable for mass preparation.

Description

CuFeO2Biological carbon composite magnetic material and preparation method thereof

Technical Field

The invention belongs toThe technical field of biochar preparation, in particular to CuFeO₂A biochar composite magnetic material and a preparation method thereof.

Background

CuFeO₂The copper-iron ore type oxide is one of delafossite type oxides, consists of Cu and Fe elements which are stored on the earth abundantly and are nontoxic, has a forbidden band width of 1.3-2.1eV, and is often used as a photocatalyst for hydrogen production under visible light, heavy metal reduction in water and organic dye degradation. Further, CuFeO₂Redox reaction between bimetallic Fe and Cu (Fe)²⁺/Fe³⁺And Cu⁺/Cu²⁺) Has synergistic effect on Fenton reaction, Cu⁺Can catalyze H at a wide pH₂O₂OH is generated and Fe is promoted³⁺The catalyst is also used as a heterogeneous Fenton catalyst to degrade organic pollutants in water. Thus, CuFeO with respect to the delafossite-type structure₂Research on material preparation is currently a focus.

Currently, CuFeO is prepared₂Common methods for biochar materials include sol-gel methods, solid-phase sintering methods, and hydrothermal methods. Wherein the hydrothermal method does not need sintering, which can avoid the defects of crystal grain growth, easy impurity mixing and the like in the sintering process and can greatly reduce the preparation of CuFeO₂Reaction temperature of the biochar material. Hydrothermal synthesis of CuFeO₂In the process of biochar, the selected copper sources are all Cu²⁺Adding a reducing agent in the reaction process to convert the Cu into Cu⁺The preparation cost is increased, and the method is not favorable for large-scale industrial production. Therefore, how to reduce CuFeO₂The preparation cost of the biochar catalyst and the improvement of the catalytic activity of the biochar catalyst become critical problems to be solved urgently.

Disclosure of Invention

Aiming at various defects of the prior art, the inventor researches and designs a CuFeO in long-term practice₂A biochar composite magnetic material and a preparation method thereof.

In order to achieve the purpose, the invention provides the following technical scheme:

CuFeO₂Preparation of biochar composite magnetic materialThe preparation method comprises the steps of carbonizing original ginger stalks at the temperature of 300-750 ℃ for 90min, and preparing ginger stalk biochar and Fe with the concentration of 10-30 mmol/L through carbonization³⁺The salt concentration is 10 mmol/L-30 mmol/LCu²⁺Mixing salt in water, continuously adding a sodium hydroxide solution with the concentration of 50-80 g/L or a potassium hydroxide solution with the concentration of 50-80 g/L under the stirring condition, transferring the solution into a hydrothermal reaction kettle, carrying out hydrothermal reaction at the temperature of 100-200 ℃ for 6-48 hours, naturally cooling a hydrothermal product to room temperature, washing the hydrothermal product with deionized water for 2-3 times, carrying out suction filtration, and finally drying the product after suction filtration in a blast drying oven at the temperature of 105 ℃ to constant weight to obtain CuFeO₂A biochar composite material.

Further, said Fe³⁺The salt is any one of ferric chloride, ferric nitrate nonahydrate, ferric sulfate or ferric oxalate pentahydrate.

Further, the Cu²⁺The salt is any one of copper chloride, copper nitrate trihydrate or copper sulfate pentahydrate.

CuFeO₂The biochar composite magnetic material is prepared by the preparation method, and has large specific surface area and good adsorption effect.

The invention has the beneficial effects that:

the preparation method does not need an additional reducing agent, has low cost, short period and high purity, is suitable for mass preparation and is convenient for industrial production; the obtained CuFeO₂The biological carbon composite material improves CuFeO₂Compared with pure CuFeO₂And the specific surface area of the biochar is improved, and the prepared composite material has certain magnetism, so that the biochar has good application prospects in the fields of adsorption, photoelectrocatalysis, advanced oxidation and the like.

Drawings

FIG. 1 is a thermogravimetric analysis chart of crushed and dried ginger stalks at 30-700 ℃;

FIG. 2 is a graph showing the yield of ginger stalks at 300, 450, 600 and 750 ℃ carbonization temperatures;

FIG. 3 shows the results of scanning electron microscopy of biochar and its magnetic composite;

FIG. 4 shows CuFeO under different preparation conditions₂XRD pattern of biochar;

FIG. 5 is CuFeO₂XPS spectra of biochar.

Detailed Description

In order that those skilled in the art will better understand the technical solutions of the present invention, the present invention will be further described with reference to the following preferred embodiments.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Although methods and materials similar or equivalent to those described herein can be used in experimental or practical applications, the materials and methods are described below. In case of conflict, the present specification, including definitions, will control, and the materials, methods, and examples are illustrative only and not intended to be limiting.

The biochar has obvious influence on the volume weight of the red soil, and can effectively improve the water content and the total amount of particles of the soil with lower fertility. The biochar can not only adjust the pH of the soil and increase the organic matters of the soil, but also obviously enhance the NH of the soil by the large specific surface area and the large negative charges on the surface₄ ⁺、NO₃ ^-. The absorption of nutrients such as organic phosphorus and the like improves the soil fertility preserving capability. Physical adsorption is generated between the biochar and heavy metal ions, and ion exchange adsorption can also be generated on the surface of the biochar.

The ginger belongs to the Zingiberaceae plant, the origin is India, and the ginger is introduced into European and American areas, and the planting history of the ginger in China is long and the variety is more. Wherein, per 100g of ginger, the water content is removed, the dry matter content accounts for 13.2-15.5g, the soluble saccharide accounts for 2.02-5.35g, the cellulose accounts for 5.23-5.95g, the lipid accounts for 5.7-14.5g, the protein accounts for 7.98-10.04g, the starch accounts for 5.78-8.86g, and the vitamin C accounts for 1.84-3.34 mg.

The ginger stalks are rich in carbon and oxygen elements, wherein the content of the carbon element accounts for more than half of the content of the carbon element, so that the ginger stalks are good raw materials for preparing the biochar.

Example 1:

CuFeO₂The preparation method of the biochar composite magnetic material comprises the following steps:

at room temperature as Fe: weighing 10mmol/L Cu (NO) with Cu molar ratio of 1:1₃)₂·3H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 60ml of deionized water, carrying out ultrasonic treatment for 5-10 minutes until the solid is completely dissolved, adding 1.0g of original ginger stalk biochar into the solution, adding 50g/L of NaOH which plays a role of a mineralizer, continuously stirring for about 10 minutes until the solid is completely dissolved, transferring the mixed solution to a hydrothermal reaction kettle, placing the hydrothermal reaction kettle in a homogeneous reactor for hydrothermal reaction, and reacting for 12 hours at the temperature of 160 ℃. And after the reaction is finished, naturally returning the hydrothermal product to room temperature, washing the hydrothermal product for 2-3 times by using deionized water, performing suction filtration, and finally drying the suction-filtered product in a blast drying oven at 105 ℃ to constant weight to obtain a reaction product.

The preparation method of the original ginger stalk biochar comprises the following steps: firstly, naturally dried ginger stalks are taken, washed by water, dried at the temperature of 101 ℃, crushed and sieved by a 100-mesh sieve; setting the initial temperature to be 0 ℃, controlling the heating rate to be 5 ℃/min, staying for 90min at the carbonization temperature of 300 ℃, then adopting a natural cooling mode, after the temperature is recovered to the room temperature, washing for 2 times by using water, drying, grinding by using a mortar and sieving by using a 100-mesh sieve to obtain the original ginger stalk biochar.

Example 2:

at room temperature as Fe: weighing 30mmol/L Cu (NO) with Cu molar ratio of 1:1₃)₂·3H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 60ml of deionized water, carrying out ultrasonic treatment for 5-10 minutes until the solid is completely dissolved, adding 1.0g of original ginger stalk biochar into the solution, adding 80g/L of NaOH which plays a role of a mineralizer, continuously stirring for about 20 minutes until the solid is completely dissolved, transferring the mixed solution to a hydrothermal reaction kettle, placing the hydrothermal reaction kettle in a homogeneous reactor for hydrothermal reaction, and reacting for 6 hours at the temperature of 100 ℃. After the reaction is finished and the water is heatedAnd naturally recovering the product to room temperature, washing the product for 2-3 times by using deionized water, performing suction filtration, and finally drying the product subjected to suction filtration in a blast drying oven at 105 ℃ to constant weight to obtain a reaction product.

The preparation method of the original ginger stalk biochar comprises the following steps: firstly, naturally dried ginger stalks are taken, washed by water, dried at the temperature of 101 ℃, crushed and sieved by a 100-mesh sieve; setting the initial temperature to be 0 ℃, controlling the heating rate to be 5 ℃/min, staying for 90min at the carbonization temperature of 750 ℃, then adopting a natural cooling mode, after the temperature is recovered to the room temperature, washing for 2 times by using water, drying, grinding by using a mortar and sieving by using a 100-mesh sieve to obtain the original ginger stalk biochar.

Example 3:

at room temperature as Fe: weighing 20mmol/L Cu (NO) with Cu molar ratio of 1:1₃)₂·3H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 60ml of deionized water, carrying out ultrasonic treatment for 5-10 minutes until the solid is completely dissolved, adding 1.0g of original ginger stalk biochar into the solution, adding 65g/L of potassium hydroxide which plays a role of a mineralizer, continuously stirring for about 10 minutes until the solid is completely dissolved, transferring the mixed solution to a hydrothermal reaction kettle, placing the hydrothermal reaction kettle in a homogeneous reactor for hydrothermal reaction, and reacting for 48 hours at the temperature of 200 ℃. And after the reaction is finished, naturally returning the hydrothermal product to room temperature, washing the hydrothermal product for 2-3 times by using deionized water, performing suction filtration, and finally drying the suction-filtered product in a blast drying oven at 105 ℃ to constant weight to obtain a reaction product.

The preparation method of the original ginger stalk biochar comprises the following steps: firstly, naturally dried ginger stalks are taken, washed by water, dried at the temperature of 101 ℃, crushed and sieved by a 100-mesh sieve; setting the initial temperature to be 0 ℃, controlling the heating rate to be 5 ℃/min, staying for 90min at the carbonization temperature of 600 ℃, then adopting a natural cooling mode, after the temperature is recovered to the room temperature, washing for 2 times by using water, drying, grinding by using a mortar and sieving by using a 100-mesh sieve to obtain the original ginger stalk biochar.

Example 4

at room temperature as Fe: weighing 10mmol/L Cu (NO) with Cu molar ratio of 1:1₃)₂·3H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 60ml of deionized water, carrying out ultrasonic treatment for 5-10 minutes until the solid is completely dissolved, adding 1.0g of original ginger stalk biochar into the solution, adding 75g/L of NaOH which plays a role of a mineralizer, continuously stirring for about 20 minutes until the solid is completely dissolved, transferring the mixed solution to a hydrothermal reaction kettle, placing the hydrothermal reaction kettle in a homogeneous reactor for hydrothermal reaction, and reacting for 12 hours at the temperature of 160 ℃. And after the reaction is finished, naturally returning the hydrothermal product to room temperature, washing the hydrothermal product for 2-3 times by using deionized water, performing suction filtration, and finally drying the suction-filtered product in a blast drying oven at 105 ℃ to constant weight to obtain a reaction product.

The preparation method of the original ginger stalk biochar comprises the following steps: firstly, naturally dried ginger stalks are taken, washed by water, dried at the temperature of 101 ℃, crushed and sieved by a 100-mesh sieve; setting the initial temperature to be 0 ℃, controlling the heating rate to be 5 ℃/min, staying for 90min at the carbonization temperature of 450 ℃, then adopting a natural cooling mode, after the temperature is recovered to the room temperature, washing for 2 times by using water, drying, grinding by using a mortar and sieving by using a 100-mesh sieve to obtain the original ginger stalk biochar.

Example 5

Pure CuFeO₂The preparation method comprises the following steps: at room temperature as Fe: weighing 15mmol/L Cu (NO) with Cu molar ratio of 1:1₃)₂·3H₂O and Fe (NO)₃)₃·9H₂Dissolving O in 70ml of deionized water, carrying out ultrasonic treatment for 5-10 minutes until the solid is completely dissolved, adding 5ml of ethylene glycol into the solution to serve as a reducing agent, adding 70g/L of NaOH which plays a role of a mineralizer, continuously stirring for about 10-15 minutes until the solid is completely dissolved to form a hydrothermal reaction precursor, transferring the hydrothermal reaction precursor to a hydrothermal reaction kettle, carrying out hydrothermal reaction in a homogeneous reactor, and reacting for 20 hours at the temperature of 180 ℃. Cooling the reaction kettle after reaction to room temperature, and carrying out hydrothermal reactionThe obtained product is sequentially centrifugally washed to be neutral by absolute ethyl alcohol, 0.5mol/L dilute nitric acid and deionized water, and the centrifuged product is dried in a drying oven for 10 hours at the temperature of 80 ℃ to obtain pure CuFeO₂A material.

Example 6

Thermogravimetric analysis of ginger stalk

Thermogravimetric analysis is carried out on the crushed and dried ginger stalks at the temperature of 30-700 ℃, and the test result is shown in figure 1. The results of calculating the yield of the ginger stalks at the carbonization temperatures of 300 ℃, 450 ℃, 600 ℃ and 750 ℃ are shown in FIG. 2.

As can be seen from FIG. 1, the ginger stalk carbonization process is mainly carried out in three stages. Firstly, in the drying stage, at about 100 ℃, the water in the ginger stalks absorbs heat, at the moment, the enthalpy value is 3.50, the weight loss of the sample is 0.48mg, and the weight loss rate is 4.84%. As the temperature increased, the sample entered the volatile pyrolysis stage, at which point the extrapolated onset temperature was 223.13 ℃, the weight loss was 6.30mg, and the weight loss rate was 63.36%. At the moment, the internal thermal decomposition reaction of the main ginger stalks, the rearrangement and the breakage of most chemical bonds occur, a large amount of organic matters volatilize, and the DTA curve shows that the stage is an exothermic reaction, the enthalpy value is 33.15, because the volatilized gaseous organic matters undergo static osmotic diffusion combustion under the anoxic condition, and heat is provided for the volatilization of the organic matters to support the decomposition. The last stage is a comprehensive carbonization stage, and the TG curve shows that the weight loss rate of the ginger stalks begins to increase when the temperature is 393.18 ℃, the extrapolated termination point temperature is 450 ℃, the weight loss amount is 2.75mg, and the weight loss rate is 27.65 percent. The quality of the ginger stalks is not changed along with the rise of the temperature, so that the temperature of 450 ℃ is the lowest complete carbonization temperature of the ginger stalks, and the carbonization temperatures of 300 ℃, 450 ℃, 600 ℃ and 750 ℃ are selected in the test respectively.

As can be seen from fig. 2, when the carbonization temperature is 300 ℃, the yield is the highest, and can reach 46.7%, and when the carbonization temperature is 750 ℃, the yield is only 28.1%, the experimental result is consistent with the conclusion of fig. 3-1, when the temperature is lower, the organic matter is incompletely carbonized, the product is a mixture of incompletely carbonized organic carbon and highly carbonized organic carbon, and the biochar is in a "rubbery state", but the content ratio of the highly carbonized organic carbon is increased with the increase of the carbonization temperature, and the biochar gradually transits to the "glassy state" carbon. The raw carbon retention in biochar was found to be very considerable, and in particular the raw carbon retention was strongly related to the precursor material of the biochar. In the temperature rising process, a large amount of organic matters volatilize to form porous matters, so that the yield of the biochar is reduced as the carbonization temperature for preparing the biochar is increased.

Example 7

CuFeO₂Morphology analysis of biochar

The results of scanning electron microscopy of biochar and its magnetic composite are shown in FIG. 3, CuFeO₂The EDS of the biochar is shown in FIG. 4. As can be seen from (a) and (b) in fig. 3, under the same magnification (5000 times), the biochar made of the ginger stalks with the carbonization temperature of 450 ℃ is larger in particle size and keeps the original shape relatively intact, while the biochar made of the ginger stalks with the carbonization temperature of 600 ℃ is smaller in particle size and relatively larger in specific surface area due to the fact that the biochar is higher in carbonization temperature and less in residual organic matters, and the original components are damaged to a great extent.

As can be seen from (a) and (c), under the load of CuFeO₂Then, more crystals in an ellipsoid shape are formed on the surface of the biochar, and the crystals may be CuFeO₂And the crystal is large in load amount, good in load effect and possibly good in adsorption effect when observed from the surface. As can be seen from (c) and (d), CuFeO was adjusted₂CuFeO on the surface of the biochar after the adding ratio of the biochar to the biochar is changed from 2:1 to 1:5₂The density is obviously reduced, the adsorption synergistic effect of the two is possibly weakened, and the adsorption effect is poor. Microscopically, CuFeO₂The ellipsoidal shape of the film is formed by a large amount of flaky CuFeO₂The experiment adopts a hydrothermal method to prepare CuFeO₂The oxidation-reduction reaction time is longer, and the uniform ellipsoidal CuFeO is formed₂Good conditions of (1).

Example 8

CuFeO₂Crystal structure analysis of biochar

XRD patterns of samples under different preparation conditions are shown in FIG. 4, and CuFeO exists in the samples₂(JSPF No.75-2146) and Fe₂O₃(JSPF No. 89-0599). CuFeO prepared by different doping ratios₂CuFeO in biochar₂From the obvious difference, when the doping ratio is 5:1, CuFeO₂The characteristic peak of (A) is not obvious, but follows CuFeO₂Increased doping ratio, CuFeO₂The characteristic peak of (a) becomes gradually apparent. CuFeO prepared from biochar with different carbonization temperatures₂CuFeO in/BC₂The characteristic peak of the alloy also has certain difference, the characteristic peak at the carbonization temperature of 450 ℃ is obviously superior to the characteristic peak at the carbonization temperature of 600 ℃, CuFeO₂The more pronounced the synergistic effect with biochar may be, the better the adsorption effect may be.

Example 9

CuFeO₂XPS analysis of biochar

For further exploring CuFeO₂Chemical composition of/BC surface and valence state of each element to CuFeO₂XPS spectrum analysis of biochar showed the results in FIG. 5.

XPS spectrum results show that CuFeO₂The biochar contains Cu, Fe, C, O and other elements, and after being corrected by the standard binding energy of carbon element 284.6eV, the binding energy of O1s at the peak position is near 531eV, the binding energy of C1s at the peak position is near 287eV, and both elements are CuFeO₂Basic elements in/BC. The characteristic peaks of Cu element appear at 934.7eV (Cu2 p)_3/2) And 953.3eV (Cu2 p)_1/2) In the vicinity, the difference between the two binding energies was 18.6 eV. The characteristic peaks of Fe respectively appear at 711.25eV (Fe2 p)_3/2) And 724eV (Fe2 p)_1/2) In the vicinity, the difference between the binding energies was 12.75eV, and it was confirmed that CuFeO may be contained in the sample₂The atomic number of Cu element is 29, its outstanding auger line is LMM series, its electron layer for generating initial hole and electron layer for filling initial hole are L layer and M layer respectively, and the electron layer for emitting auger electron is M layer, its Cu element can be storedIn two valence states, i.e. Cu¹⁺And Cu²⁺And the test result further verifies CuFeO₂Is present.

The above detailed description is only for the preferred embodiment of the present invention, and the present invention should not be limited to the embodiment, i.e. all equivalent changes and modifications should be made within the scope of the present invention.

Claims

1. CuFeO₂The preparation method of the biochar/biochar composite magnetic material is characterized in that original ginger stalks are carbonized at the temperature of 300-750 ℃ for 90min, and the biochar of the ginger stalks prepared by carbonization and Fe with the concentration of 10 mmol/L-30 mmol/L³⁺The salt concentration is 10 mmol/L-30 mmol/LCu²⁺Mixing salt in water, continuously adding a sodium hydroxide solution with the concentration of 50-80 g/L or a potassium hydroxide solution with the concentration of 50-80 g/L under the stirring condition, transferring the solution into a hydrothermal reaction kettle, carrying out hydrothermal reaction at the temperature of 100-200 ℃ for 6-48 hours, naturally cooling a hydrothermal product to room temperature, washing the hydrothermal product with deionized water for 2-3 times, carrying out suction filtration, and finally drying the product after suction filtration in a blast drying oven at the temperature of 105 ℃ to constant weight to obtain CuFeO₂A biochar composite material.

2. CuFeO according to claim 1₂The preparation method of the biochar composite magnetic material is characterized in that Fe³⁺The salt is any one of ferric chloride, ferric nitrate nonahydrate, ferric sulfate or ferric oxalate pentahydrate.

3. CuFeO according to claim 1₂The preparation method of the/biochar composite magnetic material is characterized in that the Cu²⁺The salt is any one of copper chloride, copper nitrate trihydrate or copper sulfate pentahydrate.

4. CuFeO₂The/biochar composite magnetic material is characterized by being prepared according to the methodThe preparation method of any one of claims 1 to 3, which has a large specific surface area and a good adsorption effect.