CN108722356B - Preparation method of nano zero-valent iron-loaded hydrophilic porous biochar composite material - Google Patents

Preparation method of nano zero-valent iron-loaded hydrophilic porous biochar composite material Download PDF

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CN108722356B
CN108722356B CN201810599359.3A CN201810599359A CN108722356B CN 108722356 B CN108722356 B CN 108722356B CN 201810599359 A CN201810599359 A CN 201810599359A CN 108722356 B CN108722356 B CN 108722356B
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biochar
valent iron
hydrophilic porous
nano zero
porous biochar
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CN108722356A (en
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杨帆
张帅帅
李天霄
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Northeast Agricultural University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
    • B01J20/0225—Compounds of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt
    • B01J20/0229—Compounds of Fe
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28064—Surface area, e.g. B.E.T specific surface area being in the range 500-1000 m2/g
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/4825—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds

Abstract

A preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite relates to a preparation method of a hydrophilic porous biochar composite. The invention aims to solve the problems that the existing matrix loaded with metal particles is high in cost, nano zero-valent iron is unstable and easy to agglomerate, and the performance is lower in the process of removing heavy metals by adsorption. The method comprises the following steps: firstly, biomass pyrolysis molten salt activation; secondly, preparing a hydrophilic porous biochar material; and thirdly, loading the nano zero-valent iron to obtain the nano zero-valent iron loaded hydrophilic porous biochar composite. The specific surface area of the nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the invention can reach 603.4m2·g‑1. Because the corn straws are agricultural wastes with low cost and wide sources, the corn straws are pyrolyzed to be used as a matrix material, so that the cost of the synthesis process is reduced. The nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the invention is used in the field of environmental pollutant remediation.

Description

Preparation method of nano zero-valent iron-loaded hydrophilic porous biochar composite material
Technical Field
The invention relates to a preparation method of a hydrophilic porous biochar composite material.
Background
The nanometer zero-valent iron is an environment-friendly material and has the advantages of small particle size, large surface area, strong reduction capability, high reaction speed and the like. Therefore, the nano zero-valent iron is widely applied to the field of water body restoration. However, the nano zero-valent iron has poor stability in air and high storage difficulty, and is easy to react with water or oxygen in a surrounding medium, so that an oxide layer is formed to inhibit further reaction with pollutants. In addition, due to the high surface energy, the nano zero-valent iron is easy to agglomerate into larger particles, so that the reaction activity is reduced, and therefore, the utilization rate of the nano zero-valent iron is low.
In recent years, the stability of the nano zero-valent iron can be effectively improved by using materials such as silicon dioxide, polymers, clay minerals, activated carbon, graphene and carbon nanotubes as carriers. However, these carriers are costly and have been used for adsorption removal of heavy metalsThe performance in the process is lower. Studies have reported the removal of heavy metals Pb from groundwater by using sepiolite-loaded nanoscale zero-valent iron2+The maximum adsorption capacity is 44.05 mg/g; zero-valent iron is loaded on SiC nano particles and used for Pb in aqueous solution2+The maximum adsorption capacity of the material to lead is 178.57 mg/g.
Disclosure of Invention
The invention aims to solve the problems that the existing matrix loaded with metal particles is high in cost, nano zero-valent iron is unstable and easy to agglomerate, and the performance is lower in the process of removing heavy metals by adsorption, and provides a preparation method of a nano zero-valent iron loaded hydrophilic porous biochar composite material.
A preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material comprises the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning the biochar raw material for 5-10 times by using distilled water, drying the biochar raw material at the temperature of 70-90 ℃, and sieving the dried biochar raw material by using a 100-200-mesh sieve to obtain fine biochar raw material powder;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing inert gas into the tubular furnace, heating the tubular furnace to 700-900 ℃ under the protection of the inert gas, and then pyrolyzing the reactant at the temperature of 700-900 ℃ for 1-3 h under the protection of the inert gas atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the inert gas in the first step is nitrogen or argon;
the mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is (1-10) to 1;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 5 to 10 times, drying at the temperature of between 70 and 90 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 3 to 24 hours, taking out the product, washing the product with distilled water for 5 to 10 times, and drying at the temperature of between 70 and 90 ℃ to obtain a hydrophilic porous biochar material;
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 2-10 h at the stirring speed of 1000-1500 r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 2-10 h, then performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 50-70 ℃ to obtain the nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the inert gas in the third step is nitrogen or argon;
the mass ratio of the ferric salt in the ferric salt water solution to the reducing agent in the reducing solution in the third step is 1 (0.1-0.5).
The principle and the advantages of the invention are as follows:
the nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by taking biochar raw materials as raw materials and adopting the combination of molten salt assistance and chemical reduction has a large specific surface area, and the specific surface area of the nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the method can reach 603.4m2·g-1. The nano zero-valent iron can be highly and uniformly dispersed on the surface of the hydrophilic porous charcoal material, so that the utilization efficiency of the nano zero-valent iron in the environment is improved;
secondly, when the hydrophilic porous charcoal material is mixed with ferrous ions, the ferrous ions are adsorbed on the surface of the hydrophilic porous charcoal material by the oxygen-containing functional groups on the surface of the hydrophilic porous charcoal material, so that the dispersity of the generated nano zero-valent iron on the surface of the porous charcoal material is improved. The synergistic effect of the nano zero-valent iron and the porous charcoal material improves the utilization efficiency of the nano zero-valent iron in the environment;
and thirdly, the raw material of the biochar is used as cheap and easily-obtained agricultural waste, and the biochar is pyrolyzed to be used as a matrix material, so that the synthesis cost is reduced. The nano zero-valent iron-loaded hydrophilic porous charcoal composite material is prepared by a method combining the nano zero-valent iron with metal salt mixing pyrolysis and chemical reduction, so that the dispersity of the nano zero-valent iron is effectively improved, and the utilization value of the nano zero-valent iron in the field of environmental remediation is improved;
fourthly, the nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the invention removes heavy metal Pb2+The adsorption amount of (B) was 174.5mg g-1～195.0mg·g-1(ii) a Removal of heavy metals Cu2+The adsorption amount of (B) was 68.8mg g-1～161.9mg·g-1Removal of the heavy metal Zn2+The adsorption amount of (B) was 62.1mg g-1～109.7mg·g-1；
And fifthly, the preparation method is simple and convenient, and the raw materials are cheap and easy to obtain, so that the preparation method is suitable for large-batch synthesis and preparation.
The nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the invention is used in the field of environmental pollutant remediation.
Drawings
FIG. 1 is a scanning electron microscope image of a nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in step three of the example;
FIG. 2 is a transmission electron microscope image of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in step three of the example;
FIG. 3 is an XRD spectrum of the nano zero-valent iron-supported hydrophilic porous biochar composite prepared in step three of the example;
FIG. 4 is a diagram of N of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment2Adsorption-desorption spectra.
Detailed Description
The technical solution of the present invention is not limited to the following specific embodiments, but includes any combination of the specific embodiments.
The first embodiment is as follows: the embodiment is a preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material, which is specifically completed according to the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning the biochar raw material for 5-10 times by using distilled water, drying the biochar raw material at the temperature of 70-90 ℃, and sieving the dried biochar raw material by using a 100-200-mesh sieve to obtain fine biochar raw material powder;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing inert gas into the tubular furnace, heating the tubular furnace to 700-900 ℃ under the protection of the inert gas, and then pyrolyzing the reactant at the temperature of 700-900 ℃ for 1-3 h under the protection of the inert gas atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the inert gas in the first step is nitrogen or argon;
the mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is (1-10) to 1;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 5 to 10 times, drying at the temperature of between 70 and 90 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 3 to 24 hours, taking out the product, washing the product with distilled water for 5 to 10 times, and drying at the temperature of between 70 and 90 ℃ to obtain a hydrophilic porous biochar material;
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 2-10 h at the stirring speed of 1000-1500 r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 2-10 h, then performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 50-70 ℃ to obtain the nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the inert gas in the third step is nitrogen or argon;
the mass ratio of the ferric salt in the ferric salt water solution to the reducing agent in the reducing solution in the third step is 1 (0.1-0.5).
The first step of the embodiment is to perform pyrolysis: the metal salt is melted at high temperature to activate the biomass to prepare the porous biochar, and the porous biochar material obtained after pyrolysis has an obvious hierarchical porous structure.
In the second step of the embodiment, the hydrophilic capacity of the porous biochar material is enhanced by immersing the porous biochar material in an acidic oxidant solution, so that the porous biochar material can be better dissolved in water; and the number of oxygen-containing functional groups on the surface of the porous biochar material can be increased by the treatment in the process, so that the application range of the material is favorably enlarged.
The purpose of dropping the reducing solution in step three of the present embodiment is: reducing ferrous iron adsorbed on the surface of the hydrophilic porous charcoal material to zero-valent iron in situ, and highly dispersing the reduced nano zero-valent iron on the surface of the hydrophilic porous charcoal material.
The principle and advantages of the embodiment are as follows:
according to the embodiment, a biological carbon raw material is used as a raw material, the nano zero-valent iron-loaded hydrophilic porous biological carbon composite material prepared by combining molten salt assistance and chemical reduction has a large specific surface area, and the specific surface area of the nano zero-valent iron-loaded hydrophilic porous biological carbon composite material prepared by the embodiment can reach 603.4m2·g-1. The nano zero-valent iron can be highly and uniformly dispersed on the surface of the hydrophilic porous charcoal material, so that the utilization efficiency of the nano zero-valent iron in the environment is improved;
secondly, when the hydrophilic porous charcoal material is mixed with ferrous ions, the ferrous ions are adsorbed on the surface of the hydrophilic porous charcoal material by the oxygen-containing functional groups on the surface of the hydrophilic porous charcoal material, so that the dispersity of the generated nano zero-valent iron on the surface of the porous charcoal material is improved. The synergistic effect of the nano zero-valent iron and the porous charcoal material improves the utilization efficiency of the nano zero-valent iron in the environment;
and thirdly, the raw material of the biochar is used as cheap and easily-obtained agricultural waste, and the biochar is pyrolyzed to be used as a matrix material, so that the synthesis cost is reduced. The nano zero-valent iron-loaded hydrophilic porous charcoal composite material is prepared by a method combining the nano zero-valent iron with metal salt mixing pyrolysis and chemical reduction, so that the dispersity of the nano zero-valent iron is effectively improved, and the utilization value of the nano zero-valent iron in the field of environmental remediation is improved;
and fourthly, the preparation method is simple and convenient, and the raw materials are cheap and easy to obtain, so that the method is suitable for large-batch synthesis and preparation.
The nano zero-valent iron-loaded hydrophilic porous biochar composite material prepared by the embodiment is used for the field of environmental pollutant remediation.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the biochar raw material in the first step is one or a mixture of more of corn straw, wheat straw, soybean straw, rice straw and rice hull. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the metal salt in the first step is KHCO3Or NaHCO3. The other is the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: step one, the temperature rise rate of the middle-tube furnace is 8-11 ℃/min when the temperature rises to 700-900 ℃. The others are the same as in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: grinding and mixing fine biochar raw material powder and metal salt to obtain a reactant; and putting the reactants in a tubular furnace, introducing inert gas into the tubular furnace, heating the tubular furnace to 700-800 ℃ under the protection of the inert gas, and pyrolyzing the tubular furnace for 1-2 hours at the temperature of 700-800 ℃ under the protection of the inert gas atmosphere to obtain the pyrolyzed and carbonized porous biochar material. The other is the same as one of the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: the mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is (1-5): 1. The other is the same as one of the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the temperature of the water bath heating in the second step is 50-70 ℃. The other is the same as one of the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: the acidic oxidant solution in the second step is (NH)4)2S2O8And 10-20% sulfuric acid; in the acidic oxidizing agent solution (NH)4)2S2O8And H2SO4The molar ratio of (1) to (5). The other is the same as one of the first to seventh embodiments.
The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: the ferric salt aqueous solution in the third step is ferrous nitrate, ferrous sulfate solution or ferrous chloride, and the concentration of the ferric salt aqueous solution is 0.02 mol.L-1～0.2mol·L-1. The rest is the same as the first to eighth embodiments.
The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: the reducing solution in the third step is NaBH4The concentration of the solution, the reducing solution is 0.1 mol.L-1～1mol·L-1。
The other is the same as one of the first to ninth embodiments.
The following examples are given to illustrate the present invention, and the following examples are carried out on the premise of the technical solution of the present invention, and give detailed embodiments and specific procedures, but the scope of the present invention is not limited to the following examples.
The first embodiment is as follows: a preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material comprises the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning for 7 times by using distilled water, drying at the temperature of 80 ℃, and sieving the dried biochar raw material by using a 100-mesh sieve to obtain fine biochar raw material powder;
the biochar raw material in the first step is corn straw;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing nitrogen into the tubular furnace, heating the tubular furnace to 800 ℃ under the protection of the nitrogen, and pyrolyzing the reactant for 2 hours at the temperature of 800 ℃ under the protection of nitrogen atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the metal salt in the first step is KHCO3；
The mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is 1: 1;
step one, the temperature rise rate of the middle-tube furnace is 10 ℃/min when the temperature rises to 800 ℃;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 7 times, drying at the temperature of 80 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 8 hours, taking out the product, washing the product with distilled water for 7 times, and drying at the temperature of 80 ℃ to obtain a hydrophilic porous charcoal material;
the temperature of the water bath heating in the second step is 60 ℃;
the acidic oxidant solution in the second step is (NH)4)2S2O8And 17.5 percent of sulfuric acid by mass; in the acidic oxidizing agent solution (NH)4)2S2O8And H2SO4In a molar ratio of 1: 2;
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 4 hours at the stirring speed of 1200r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 5 hours, performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 60 ℃ to obtain a nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the inert gas in the third step is nitrogen;
the ferric salt aqueous solution in the third step is ferrous sulfate solution, and the concentration of the ferric salt aqueous solution is 0.075 mol.L-1；
The reducing solution in the third step is NaBH4The concentration of the solution, the reducing solution is 0.3 mol.L-1；
The mass ratio of the ferric salt in the ferric salt aqueous solution in the third step to the reducing agent in the reducing solution is 1: 0.27.
In the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment, the mass ratio of the nano zero-valent iron to the hydrophilic porous biochar material is 1: 1.
The scanning electron microscope photo of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the example is shown in fig. 1;
the transmission electron microscope photograph of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the example is shown in fig. 2.
FIG. 1 is a scanning electron microscope image of a nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in step three of the example;
as can be seen from fig. 1, the nano zero-valent iron particles are uniformly dispersed on the surface of the hydrophilic porous biochar material.
FIG. 2 is a transmission electron microscope image of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in step three of the example;
as can be seen from FIG. 2, the nano zero-valent iron particles have no agglomeration phenomenon, and have an average particle size of about 100nm and are uniformly dispersed on the surface of the hydrophilic porous biochar material;
FIG. 3 is an XRD spectrum of the nano zero-valent iron-supported hydrophilic porous biochar composite prepared in step three of the example;
from fig. 3, the crystal properties of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the example can be analyzed. The broad and weak diffraction peak centered at 21.6 ° in the XRD pattern is attributed to carbon element and exists mainly in amorphous form.The sample shows three strong diffraction peaks of 44.7 degrees, 65.0 degrees and 82.3 degrees, which respectively correspond to the nanometer zero-valent iron (Fe)0) (JCPDS, NO.87-0721)) of (100), (200) and (211). These results indicate that the well-crystallized nano zero-valent iron has been successfully loaded on the surface of the hydrophilic porous biochar material.
FIG. 4 is a diagram of N of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment2Adsorption-desorption spectra.
As can be seen from FIG. 4, the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the example has the characteristics of type II isotherm under medium relative pressure (P/P)00.4-0.95) generated by capillary condensation, and an H4 type hysteresis loop exists, indicating that the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the example has a micropore and mesopore structure.
The specific surface area of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment can reach 603.4m2·g-1。
Example two: a preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material comprises the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning for 7 times by using distilled water, drying at the temperature of 80 ℃, and sieving the dried biochar raw material by using a 100-mesh sieve to obtain fine biochar raw material powder;
the biochar raw material in the first step is corn straw;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing nitrogen into the tubular furnace, heating the tubular furnace to 800 ℃ under the protection of the nitrogen, and pyrolyzing the reactant for 2 hours at the temperature of 800 ℃ under the protection of nitrogen atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the metal salt in the first step is KHCO3；
The mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is 1: 1;
step one, the temperature rise rate of the middle-tube furnace is 10 ℃/min when the temperature rises to 800 ℃;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 7 times, drying at the temperature of 80 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 8 hours, taking out the product, washing the product with distilled water for 7 times, and drying at the temperature of 80 ℃ to obtain a hydrophilic porous charcoal material;
the temperature of the water bath heating in the second step is 60 ℃;
the acidic oxidant solution in the second step is (NH)4)2S2O8And 17.5 percent of sulfuric acid by mass; in the acidic oxidizing agent solution (NH)4)2S2O8And H2SO4In a molar ratio of 1: 2;
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 4 hours at the stirring speed of 1200r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 5 hours, performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 60 ℃ to obtain a nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the inert gas in the third step is nitrogen;
the ferric salt aqueous solution in the third step is ferrous sulfate solution, and the concentration of the ferric salt aqueous solution is 0.035 mol.L-1；
The reducing solution in the third step is NaBH4The concentration of the solution, the reducing solution is 0.15 mol.L-1；
The mass ratio of the ferric salt in the ferric salt aqueous solution in the third step to the reducing agent in the reducing solution is 1: 0.27.
In the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the second step and the third step of the embodiment, the mass ratio of the nano zero-valent iron to the hydrophilic porous biochar material is 1: 2.
Example three: a preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material comprises the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning for 7 times by using distilled water, drying at the temperature of 80 ℃, and sieving the dried biochar raw material by using a 100-mesh sieve to obtain fine biochar raw material powder;
the biochar raw material in the first step is corn straw;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing nitrogen into the tubular furnace, heating the tubular furnace to 800 ℃ under the protection of the nitrogen, and pyrolyzing the reactant for 2 hours at the temperature of 800 ℃ under the protection of nitrogen atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the metal salt in the first step is KHCO3；
The mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is 1: 1;
step one, the temperature rise rate of the middle-tube furnace is 10 ℃/min when the temperature rises to 800 ℃;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 7 times, drying at the temperature of 80 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 8 hours, taking out the product, washing the product with distilled water for 7 times, and drying at the temperature of 80 ℃ to obtain a hydrophilic porous charcoal material;
the temperature of the water bath heating in the second step is 60 ℃;
the acidic oxidant solution in the second step is (NH)4)2S2O8And 17.5 percent of sulfuric acid by massThe mixed solution of (1); in the acidic oxidizing agent solution (NH)4)2S2O8And H2SO4In a molar ratio of 1: 2;
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 4 hours at the stirring speed of 1200r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 5 hours, performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 60 ℃ to obtain a nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the inert gas in the third step is nitrogen;
the ferric salt aqueous solution in the third step is ferrous sulfate solution, and the concentration of the ferric salt aqueous solution is 0.15 mol.L-1；
The reducing solution in the third step is NaBH4The concentration of the solution, the reducing solution is 0.6 mol.L-1；
The mass ratio of the ferric salt in the ferric salt aqueous solution in the third step to the reducing agent in the reducing solution is 1: 0.27.
The mass ratio of the nanoscale zero-valent iron to the hydrophilic porous biochar material in the nanoscale zero-valent iron-loaded hydrophilic porous biochar composite material prepared in the third step of the embodiment is 2: 1.
Example three steps of preparation of nano zero-valent iron-loaded hydrophilic porous biochar composite for removing heavy metal Pb2+、Cu2+And Zn2+The adsorption capacity is 192.8mg g-1，125.4mg·g-1And 73.8mg g-1And the porous charcoal material obtained in the first step of the embodiment after pyrolysis and carbonization is used for adsorbing heavy metal Pb2+、Cu2+And Zn2+The adsorption capacity is respectively 108.1mg g-1，50.8mg·g-1And 33.5mg g-1And the adsorption effect is obviously lower than that of the nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment.
Example two-step three-prepared nano zero-valent iron-loaded hydrophilic porous biochar compositeRemoval of heavy metals Pb2+、Cu2+And Zn2+The adsorption capacity is respectively 174.5mg g-1，68.8mg·g-1And 62.1mg g-1。
The nano zero-valent iron-loaded hydrophilic porous biochar composite prepared in the third step of the embodiment removes heavy metal Pb2+、Cu2+And Zn2+The adsorption capacity is 195.0mg g-1，161.9mg·g-1And 109.7mg g-1。

Claims (7)

1. A preparation method of a nano zero-valent iron-loaded hydrophilic porous biochar composite material is characterized in that the preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material is specifically completed according to the following steps:
firstly, biomass pyrolysis molten salt activation:
cutting and crushing a biochar raw material, cleaning the biochar raw material for 5-10 times by using distilled water, drying the biochar raw material at the temperature of 70-90 ℃, and sieving the dried biochar raw material by using a 100-200-mesh sieve to obtain fine biochar raw material powder;
secondly, grinding and mixing fine powder of the raw biochar material and metal salt to obtain a reactant; placing the reactant in a tubular furnace, introducing inert gas into the tubular furnace, heating the tubular furnace to 700-900 ℃ under the protection of the inert gas, and then pyrolyzing the reactant at the temperature of 700-900 ℃ for 1-3 h under the protection of the inert gas atmosphere to obtain a pyrolyzed and carbonized porous biochar material;
the inert gas in the first step is nitrogen or argon;
the mass ratio of the fine powder of the biochar raw material to the metal salt in the first step is (1-10) to 1;
secondly, putting the porous biochar material subjected to pyrolysis carbonization into distilled water for cleaning, and taking out the porous biochar material subjected to pyrolysis carbonization;
secondly, repeating the second step for 5 to 10 times, drying at the temperature of between 70 and 90 ℃, immersing the dried product into an acidic oxidant solution, heating in a water bath for 3 to 24 hours, taking out the product, washing the product with distilled water for 5 to 10 times, and drying at the temperature of between 70 and 90 ℃ to obtain a hydrophilic porous biochar material;
the acidic oxidant solution in the second step is (NH)4)2S2O8And 10-20% sulfuric acid; in the acidic oxidizing agent solution (NH)4)2S2O8And H2SO4The molar ratio of (1) to (5);
thirdly, under the protection of inert gas, soaking the hydrophilic porous biochar material in an iron salt aqueous solution, stirring for 2-10 h at the stirring speed of 1000-1500 r/min, keeping the stirring speed unchanged, dropwise adding a reducing solution, continuously stirring for reaction for 2-10 h, then performing centrifugal separation, and performing vacuum drying on solid matters obtained by centrifugal separation at the temperature of 50-70 ℃ to obtain the nano zero-valent iron-loaded hydrophilic porous biochar composite material;
the ferric salt aqueous solution in the third step is ferrous nitrate, ferrous sulfate solution or ferrous chloride, and the concentration of the ferric salt aqueous solution is 0.02 mol.L-1～0.2mol·L-1；
The reducing solution in the third step is NaBH4The concentration of the solution, the reducing solution is 0.1 mol.L-1～1mol·L-1；
The inert gas in the third step is nitrogen or argon;
the mass ratio of the ferric salt in the ferric salt water solution to the reducing agent in the reducing solution in the third step is 1 (0.1-0.5).
2. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1, characterized in that the biochar raw material in the first step is one or a mixture of several of corn straw, wheat straw, soybean straw, rice straw and rice hull.
3. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1The method is characterized in that the metal salt in the first step is KHCO3Or NaHCO3。
4. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1, characterized in that the heating rate of the first step of heating the medium-tube furnace to 700-900 ℃ is 8-11 ℃/min.
5. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1, characterized in that in the first step, fine biochar raw material powder and metal salt are ground and mixed to obtain a reactant; and putting the reactants in a tubular furnace, introducing inert gas into the tubular furnace, heating the tubular furnace to 700-800 ℃ under the protection of the inert gas, and pyrolyzing the tubular furnace for 1-2 hours at the temperature of 700-800 ℃ under the protection of the inert gas atmosphere to obtain the pyrolyzed and carbonized porous biochar material.
6. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1, wherein the mass ratio of the biochar raw material fine powder to the metal salt in the first step is (1-5): 1.
7. The preparation method of the nano zero-valent iron-loaded hydrophilic porous biochar composite material according to claim 1, characterized in that the temperature of water bath heating in the second step is 50-70 ℃.
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