Pretreated biomass charcoal loaded vulcanized nano zero-valent iron material as well as preparation method and application thereof

Abstract

The invention provides a pretreated biomass charcoal loaded vulcanized nano zero-valent iron material as well as a preparation method and application thereof, and relates to the technical field of environmental functional materials. The preparation method comprises the following steps: firstly, dipping pretreated biomass in phosphoric acid, pyrolyzing, and then ball-milling and crushing to micro-nano scale; then, FeCl3 is used as a precursor, NaBH4 and Na2S2O4 are used as a reducing-vulcanizing agent, and S-nZVI is loaded through a one-step method. The composite modified material has high efficiency in heavy metal pollution in a water body, can simultaneously remove various pollutants, has a wide application prospect, and provides a new efficient material choice for the field of environmental restoration.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental functional materials, and particularly to a pretreated biomass carbon supported sulfurized nano zero-valent iron material, a preparation method thereof, and an application thereof in the remediation of heavy metals in water bodies. Background Art

[0002] Nano zero-valent iron (nZVI) has been widely used in environmental pollution remediation due to its high reactivity and reduction ability. However, traditional nZVI has the following defects: it is easily oxidized and inactivated (rapidly forms an oxide layer when exposed to air or water); the particles are easily agglomerated, reducing the specific surface area and reaction efficiency; and there is insufficient selectivity for specific pollutants (such as chlorinated organic compounds). Therefore, it needs to be modified. Sulfidation can improve the electron transfer ability and electrons of nZVI, but the sulfided nZVI (S-nZVI) still has problems such as poor dispersion and easy migration and loss.

[0003] Therefore, it is necessary to prepare composite materials. By compounding sulfurized nZVI with porous carriers, the active sites can be fixed, the stability can be enhanced, and the targeted adsorption-reduction synergistic effect of pollutants can be achieved. In the prior art, there are still deficiencies in the selection of carriers and the compounding process, such as high cost, low loading rate, and poor dispersion.

[0004] Biochar refers to a carbon-rich, fluffy and porous substance formed by the pyrolysis of biomass under anoxic conditions. Common raw materials for the preparation of biochar include straw, coconut shells, sludge, etc. Due to the many advantages of biochar, such as a well-developed pore structure, a large specific surface area, rich surface functional groups, strong chemical stability and thermal stability, it is widely used as an adsorbent in pollutant removal, and its wide source and low cost make it a carrier material with excellent performance. Although biochar has many advantages in the field of environmental remediation, for single-phase biochar, generally, neither the adsorption capacity nor the kinetic rate can meet the requirements for efficient removal of pollutants in the environment.

[0005] Therefore, more and more attention has been paid to the preparation of composite materials with unique remediation functions using biochar as a carrier or an auxiliary catalyst. Summary of the Invention

[0006] Aiming at the above problems, the present invention provides a pretreated biomass carbon supported sulfurized nano zero-valent iron material, a preparation method thereof, and an application thereof, which have a high removal efficiency of heavy metals (Cr(Ⅵ), Cu, Pb, Zn, Ni, Co, Cd) and can be used to treat and repair heavy metal-polluted groundwater environments.

[0007] One of the purposes of the present invention is to provide a preparation method of a pretreated biomass carbon supported sulfurized nano zero-valent iron material.

[0008] The second object of the present invention is to provide a pre-treated biomass carbon supported sulfurized nano-zero valent iron material prepared by the preparation method.

[0009] The third object of the present invention is to provide an application of the pre-treated biomass carbon supported sulfurized nano-zero valent iron material in the remediation of heavy metals in water bodies.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] In the first aspect, the present invention provides a preparation method of a pre-treated biomass carbon supported sulfurized nano-zero valent iron material, including the following steps:

[0012] (a) Immerse the pre-treated biomass with an aqueous phosphoric acid solution, then pyrolyze and ball-mill to obtain the pre-treated biomass;

[0013] (b) Dissolve FeCl3·6H2O in an ethanol-aqueous solution for deoxygenation to obtain an FeCl3 solution; add the pre-treated biomass to the FeCl3 solution, mix well, and ultrasonically react; then dropwise add a mixed aqueous solution of NaBH4 and Na2S2O4, react to obtain a mixture, wash and dry to obtain the pre-treated biomass carbon supported sulfurized nano-zero valent iron material.

[0014] Preferably, in step (a), the biomass is selected from one of straw, coconut shell, and sludge;

[0015] Preferably, in step (a), the mass concentration of the aqueous phosphoric acid solution is 10%-60%, preferably 50%;

[0016] Preferably, in step (a), the solid-liquid ratio of the biomass to the aqueous phosphoric acid solution is 1:2 g / ml - 1:10 g / ml, preferably 1:5 g / ml;

[0017] Preferably, in step (a), the impregnation time is 12 h - 48 h, preferably 24 h;

[0018] Preferably, in step (a), the pyrolysis temperature is 500 - 800 °C, preferably 600 °C, and the pyrolysis time is 1 h - 4 h, preferably 2 h;

[0019] Preferably, in step (a), the ball-milling uses ethanol as a dispersant, the ball-milling speed is 1000 r / min - 1300 r / min, preferably 1200 r / min, and the ball-milling time is 0.5 h - 2 h, preferably 1 h.

[0020] Preferably, in step (b), in the ethanol-aqueous solution, the volume concentration of ethanol is 10% - 40%, preferably 30%;

[0021] Preferably, in step (b), the mass ratio of Fe element to the pretreated biomass is 10:1 - 2:1;

[0022] Preferably, in step (b), the ultrasonic time is 5 min - 15 min, preferably 10 min; the reaction temperature is 15°C - 45°C, preferably 25°C; the reaction time is 10 min - 60 min, preferably 20 min, and the reaction is carried out in an N2 atmosphere.

[0023] Preferably, in step (b), the molar ratio of NaBH4 to FeCl3·6H2O is 3 - 6, and the molar ratio of Na2S2O4 to FeCl3·6H2O is 0.15 - 0.25;

[0024] Preferably, in step (b), the reaction time is 15 min - 75 min, preferably 30 min.

[0025] In the present invention, FeCl3 is used as the precursor, and NaBH4 and Na2S2O4 are used as the reduction - sulfurizing agents to load S - nZVI in one step. Through the combination of ultrasonic - high - speed stirring, the full mixing of the carrier and the active substance is realized, and the action efficiency is improved.

[0026] In the second aspect, the present invention provides a pretreated biomass carbon - supported sulfidated nano - zero - valent iron material prepared by the above - mentioned preparation method.

[0027] In the third aspect, the present invention provides an application of the above - mentioned pretreated biomass carbon - supported sulfidated nano - zero - valent iron material in the remediation of heavy metals in water bodies.

[0028] Preferably, the dosage of the pretreated biomass carbon - supported sulfidated nano - zero - valent iron material is 0.1 - 2.0 g / L, and the reaction pH is 4 - 8.

[0029] Beneficial effects:

[0030] (1) The present invention innovatively adopts a step - by - step functionalization strategy to optimize the structure of the biochar - based composite material. First, surface activation of the biochar is achieved through acid pretreatment, significantly improving the density of its surface oxygen - containing functional groups; then, micro - nano - scale pulverization of carbon particles is realized through high - energy wet ball milling; finally, a one - step reduction - sulfurization process promotes the transformation of the surface metal iron phase into sulfidated nano - zero - valent iron (S - nZVI). In the prepared composite modified material, S - nZVI is evenly dispersed on the porous carrier, making full use of the pore structure of the porous carrier, improving the loading efficiency, dispersion and stability of the biochar carrier for S - nZVI, and enhancing its contact area and reaction activity with pollutants.

[0031] (2) Compared with the improvement strategies for the dispersibility of S-nZVI by conventional chemical surface modification methods (such as surfactant coating or polymer stabilization), the biochar matrix composite system proposed in the present invention has dual advantages: on the one hand, the stable dispersion of nanoparticles is achieved through physical confinement effect and chemical bonding, and on the other hand, a composite carrier is constructed using renewable biomass raw materials, which not only improves the environmental adaptability of the material but also reduces the preparation cost, showing significant advantages in environmental friendliness and economy.

[0032] (3) This composite modified material is highly efficient in treating heavy metal pollution in water bodies, can simultaneously remove multiple pollutants, and has broad application prospects, providing a new choice of efficient materials for the field of environmental remediation.

[0033] The present invention has been described in detail above, but the above embodiments are essentially illustrative only and are not intended to limit the present invention. In addition, the present invention is not restricted by any theory described in the foregoing prior art or the summary of the invention or the following examples. Description of the Drawings

[0034] Figure 1 Schematic diagram of the synthesis process of the pretreated biomass carbon supported sulfide nano zero-valent iron material in Example 1;

[0035] Figure 2 SEM-EDS diagram of pmBC prepared in Example 1;

[0036] Figure 3 SEM-EDS diagrams of pmBC-S-nZVI and pBC-S-nZVI;

[0037] Figure 4 Removal efficiency of Cr(VI) by pmBC-S-nZVI, pBC-S-nZVI and mBC-S-nZVI materials;

[0038] Figure 5 Removal efficiency of Cu, Pb, Zn, Ni, Co by pmBC-S-nZVI, S-nZVI and mBC-S-nZVI materials. Detailed Description of the Embodiments

[0039] The following further illustrates the present invention with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation to the scope of protection required by the present invention.

[0040] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the embodiments are all conventional raw materials, reagents, methods in the art.

[0041] Example 1

[0042] The preparation process of the pre-treated biochar-supported sulfurized nano-zero-valent iron material is exemplified as Figure 1 shown, and specifically includes:

[0043] 1. Biochar preparation:

[0044] (1) Take 30 g of straw powder, wash it with deionized water and dry it. Subsequently, put the mixture containing straw powder and an aqueous solution of phosphoric acid (H3PO4) with a mass concentration of 50% (the solid-liquid ratio is 1 g:5 ml) in a beaker, impregnate it by magnetic stirring for 24 hours, and carbonize the sample after washing and drying with deionized water at 600 °C for 2 hours under nitrogen conditions to obtain biochar;

[0045] (2) Use ethanol as a dispersant to ball-mill the prepared biochar with a high-energy ball mill, ball-mill it at a speed of 1200 r / min for 1 h, dry it for standby, and obtain phosphoric acid-treated ball-milled biochar (denoted as pmBC).

[0046] The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) pattern of pmBC is as Figure 2 shown. As can be seen from Figure 2 , pmBC has a relatively small particle size (mostly below 10 μm), and at the same time shows a rough, layered structure, and some pore structures can be observed. The surface elements are mainly composed of C, O, Si, Al, and P.

[0047] 2. S-nZVI loading:

[0048] Weigh 6.76 g of FeCl3·6H2O and dissolve it in 100 ml of deionized water containing 30% ethanol. Purge with N2 to remove oxygen. Mix 0.28 g of pmBC with the FeCl3 solution, sonicate for 10 min, and stir at 300 r / min at 25 °C for 20 min. The entire synthesis process is carried out in an N2 atmosphere. In addition, add 100 mL of a mixed aqueous solution of NaBH4 (4.5 g) and Na2S2O4 (0.852 g) dropwise to the three-necked flask and react for 30 min. Wash the obtained mixture three times with deoxygenated water and absolute ethanol respectively, and after suction filtration, dry the mixture under vacuum at 60 °C for 16 h to obtain pmBC-S-nZVI.

[0049] The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) pattern of pmBC-S-nZVI is as Figure 3 shown in (a) and (b) in

[0050] Comparative Example 1

[0051] The difference from Example 1 is that the straw powder is not treated with phosphoric acid, and the ball-milled biochar without phosphoric acid treatment is obtained in step 1 (denoted as mBC, and the final material is denoted as mBC-S-nZVI).

[0052] Comparative Example 2

[0053] It is different from Example 1 in that the straw powder is not subjected to ball milling treatment, and the biomass carbon treated with phosphoric acid without ball milling is obtained in Step 1 (denoted as pBC, and the final material is denoted as pBC-S-nZVI).

[0054] The scanning electron microscopy-energy dispersive spectrometry (SEM-EDX) images of pBC-S-nZVI are as Figure 3 shown in (c) and (d) of

[0055] From Figure 3 it can be seen that the surface of the ball-milled pmBC-S-nZVI particles is relatively rough, with spherical nanoparticles highly dispersed, while the dispersion of S-nZVI on the surface of the non-ball-milled pBC is slightly worse.

[0056] Select 15 - 20 points on the surfaces of the pmBC-S-nZVI and pBC-S-nZVI materials, scan the surface elements by X-ray energy spectrometry, and the relative atomic contents of each element are shown in Table 1. It can be seen that ball milling promotes the dispersion of surface S-nZVI and makes the distribution of each element on the surface more uniform.

[0057] Table 1 Atomic contents (%) on the surfaces of pmBC-S-nZVI and pBC-S-nZVI

[0058] Element O Al Si P S Fe pBC-S-nZVI 72.30 / 2.33 0.47 2.00 23.34 pmBC-S-nZVI 42.86 2.63 10.39 1.46 3.96 41.38

[0059] Comparative Example 3

[0060] Preparation of S-nZVI:

[0061] Weigh 6.76 g of FeCl3·6H2O and dissolve it in 100 ml of deionized water containing 30% ethanol. Deoxygenate by introducing N2, and add dropwise 100 mL of a mixed aqueous solution of NaBH4 (4.5 g) and Na2S2O4 (0.852 g) to the three-necked flask, and react for 30 min. The obtained mixture is washed with deoxygenated water and absolute ethanol respectively, and then the mixture is dried in vacuo at 60 °C for 16 h.

[0062] Test Example

[0063] Add the materials of the examples and comparative examples to the water containing Cr(VI) with a material dosage of 0.5 g / L, and ultrasonicate for 1 min until fully mixed; oscillate (160 r / min) at room temperature under N2 conditions for 120 min, and take 2 mL of samples at specific time intervals (1 min, 3 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 120 min) respectively. The solutions after filtration through a 0.22 μm filter membrane are used for Cr(VI) analysis. Each experiment is repeated 3 times in parallel.

[0064] The removal efficiencies of three S-nZVI-based materials, pmBC-S-nZVI, pBC-S-nZVI, and mBC-S-nZVI, for 20 mg / L Cr(VI) and 50 mg / L Cr(VI) are as follows Figure 4 shown. It can be seen from Figure 4 that the removal efficiencies of pmBC-S-nZVI for 20 mg / L and 50 mg / L Cr(VI) are significantly higher than those of pBC-S-nZVI and mBC-S-nZVI.

[0065] Using the same method to evaluate the removal efficiencies of pmBC-S-nZVI, S-nZVI, and mBC-S-nZVI for different metals, the results are as follows Figure 5 shown. It can be seen from Figure 5 that the removal efficiencies of pmBC-S-nZVI for 50 mg / L Cu, Pb, Zn, Ni, and Co are significantly higher than those of S-nZVI and mBC-S-nZVI.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: within the scope of the spirit and essence defined by the claims of the present invention, the technical solutions described in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements are still within the scope defined by the claims of the present invention.

Claims

1. A preparation method of a pre-treated biomass carbon-supported sulfurized nano-zero valent iron material, characterized in that It includes the following steps: (a) Immerse the pretreated biomass with an aqueous phosphoric acid solution, then pyrolyze and ball-mill to obtain the pretreated biomass; (b) Dissolve FeCl3·6H2O in ethanol-aqueous solution to remove oxygen to obtain an FeCl3 solution; add the pretreated biomass into the FeCl3 solution, mix well, sonicate and react; then dropwise add an aqueous solution of a mixture of NaBH4 and Na2S2O4, react to obtain a mixture, and after washing and drying, obtain a material of pretreated biomass carbon supported with sulfided nano-zero valent iron.

2. The preparation method according to claim 1, characterized in that, In step (a), the biomass is selected from one of straw, coconut shell and sludge.

3. The preparation method according to claim 1, wherein In step (a), the mass concentration of the aqueous phosphoric acid solution is 10% - 60%; In step (a), the solid-liquid ratio of the biomass to the aqueous phosphoric acid solution is 1:2 g / ml - 1:10 g / ml, preferably 1:5 g / ml.

4. The preparation method according to claim 1, characterized in that, In step (a), the impregnation time is 12 h - 48 h.

5. The preparation method according to claim 1, characterized in that, In step (a), the pyrolysis temperature is 500 - 800 °C and the pyrolysis time is 1 h - 4 h; In step (a), ethanol is used as the dispersant for ball-milling, the ball-milling speed is 1000 r / min - 1300 r / min, and the ball-milling time is 0.5 h - 2 h.

6. The preparation method according to claim 1, characterized in that, In step (b), in the ethanol-aqueous solution, the volume concentration of ethanol is 10% - 40%; In step (b), the mass ratio of Fe element to the pretreated biomass is 10:1 - 2:

1.

7. The preparation method according to claim 1, wherein In step (b), the sonication time is 5 min - 15 min, the reaction temperature is 15 °C - 45 °C, the reaction time is 10 min - 60 min, and the reaction is carried out in an N2 atmosphere.

8. The preparation method according to claim 1, characterized in that, In step (b), the molar ratio of NaBH4 to FeCl3·6H2O is 3 - 6, and the molar ratio of Na2S2O4 to FeCl3·6H2O is 0.15 - 0.25; In step (b), the reaction time is 15 min - 75 min.

9. A pre-treated biochar-supported sulfurized nano-zero valent iron material, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the material of pretreated biomass carbon supported with sulfided nano-zero valent iron according to claim 9 in the remediation of heavy metals in water bodies; Preferably, the dosage of the material of pretreated biomass carbon supported with sulfided nano-zero valent iron is 0.1 - 2.0 g / L, and the reaction pH is 4 - 8.

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