CN115055679B - Zero-valent iron reducing agent and preparation method and application thereof - Google Patents
Zero-valent iron reducing agent and preparation method and application thereof Download PDFInfo
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- CN115055679B CN115055679B CN202210638383.XA CN202210638383A CN115055679B CN 115055679 B CN115055679 B CN 115055679B CN 202210638383 A CN202210638383 A CN 202210638383A CN 115055679 B CN115055679 B CN 115055679B
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 246
- 239000003638 chemical reducing agent Substances 0.000 title claims abstract description 201
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 238000000034 method Methods 0.000 claims abstract description 68
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims abstract description 44
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 32
- 238000000197 pyrolysis Methods 0.000 claims abstract description 28
- 239000000178 monomer Substances 0.000 claims abstract description 20
- 239000011247 coating layer Substances 0.000 claims abstract description 17
- 238000001035 drying Methods 0.000 claims abstract description 16
- 239000011248 coating agent Substances 0.000 claims abstract description 15
- 238000000576 coating method Methods 0.000 claims abstract description 15
- 238000000151 deposition Methods 0.000 claims abstract description 15
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 claims abstract description 12
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 claims abstract description 12
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- 238000005229 chemical vapour deposition Methods 0.000 claims abstract description 7
- 230000001681 protective effect Effects 0.000 claims abstract description 7
- 238000002791 soaking Methods 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 45
- 238000006722 reduction reaction Methods 0.000 claims description 26
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims description 18
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 16
- GPNNOCMCNFXRAO-UHFFFAOYSA-N 2-aminoterephthalic acid Chemical compound NC1=CC(C(O)=O)=CC=C1C(O)=O GPNNOCMCNFXRAO-UHFFFAOYSA-N 0.000 claims description 14
- NQXWGWZJXJUMQB-UHFFFAOYSA-K iron trichloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].Cl[Fe+]Cl NQXWGWZJXJUMQB-UHFFFAOYSA-K 0.000 claims description 13
- 239000007789 gas Substances 0.000 claims description 12
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 239000003344 environmental pollutant Substances 0.000 claims description 10
- 231100000719 pollutant Toxicity 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 238000010000 carbonizing Methods 0.000 claims description 8
- 230000008021 deposition Effects 0.000 claims description 8
- 239000000356 contaminant Substances 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000007789 sealing Methods 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000003763 carbonization Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 3
- 229910052742 iron Inorganic materials 0.000 abstract description 11
- 239000002105 nanoparticle Substances 0.000 abstract description 5
- 230000010757 Reduction Activity Effects 0.000 abstract description 3
- 238000011065 in-situ storage Methods 0.000 abstract description 2
- 239000010842 industrial wastewater Substances 0.000 abstract description 2
- 238000004065 wastewater treatment Methods 0.000 abstract description 2
- 239000011651 chromium Substances 0.000 description 52
- 230000000694 effects Effects 0.000 description 30
- 230000009467 reduction Effects 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 18
- 238000011282 treatment Methods 0.000 description 18
- 230000000875 corresponding effect Effects 0.000 description 11
- 238000010306 acid treatment Methods 0.000 description 9
- 239000002245 particle Substances 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 230000008929 regeneration Effects 0.000 description 6
- 238000011069 regeneration method Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 5
- 230000000977 initiatory effect Effects 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 230000001603 reducing effect Effects 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000011276 addition treatment Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 238000007885 magnetic separation Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- 239000013291 MIL-100 Substances 0.000 description 2
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 2
- QMKYBPDZANOJGF-UHFFFAOYSA-N benzene-1,3,5-tricarboxylic acid Chemical compound OC(=O)C1=CC(C(O)=O)=CC(C(O)=O)=C1 QMKYBPDZANOJGF-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- SXDBWCPKPHAZSM-UHFFFAOYSA-M bromate Inorganic materials [O-]Br(=O)=O SXDBWCPKPHAZSM-UHFFFAOYSA-M 0.000 description 2
- SXDBWCPKPHAZSM-UHFFFAOYSA-N bromic acid Chemical group OBr(=O)=O SXDBWCPKPHAZSM-UHFFFAOYSA-N 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000013082 iron-based metal-organic framework Substances 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920000767 polyaniline Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 231100000419 toxicity Toxicity 0.000 description 2
- 230000001988 toxicity Effects 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 239000012692 Fe precursor Substances 0.000 description 1
- 229910002588 FeOOH Inorganic materials 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 238000001237 Raman spectrum Methods 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 238000000089 atomic force micrograph Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 230000000711 cancerogenic effect Effects 0.000 description 1
- 231100000315 carcinogenic Toxicity 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 238000009388 chemical precipitation Methods 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000012217 deletion Methods 0.000 description 1
- 230000037430 deletion Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- HVENHVMWDAPFTH-UHFFFAOYSA-N iron(3+) trinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HVENHVMWDAPFTH-UHFFFAOYSA-N 0.000 description 1
- 210000003734 kidney Anatomy 0.000 description 1
- 238000012933 kinetic analysis Methods 0.000 description 1
- 239000010985 leather Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 210000004185 liver Anatomy 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 231100000243 mutagenic effect Toxicity 0.000 description 1
- 230000003505 mutagenic effect Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000001699 photocatalysis Effects 0.000 description 1
- 239000002574 poison Substances 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 210000002784 stomach Anatomy 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/16—Metallic particles coated with a non-metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
-
- 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
- C02F1/70—Treatment of water, waste water, or sewage by reduction
- C02F1/705—Reduction by metals
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
-
- 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
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Inorganic Chemistry (AREA)
- Nanotechnology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Catalysts (AREA)
Abstract
The invention relates to the field of industrial wastewater treatment, and discloses a zero-valent iron reducing agent, and a preparation method and application thereof, wherein the preparation method comprises the following steps: a1, soaking a source reducing agent in a sodium persulfate solution, drying, and then depositing an aniline monomer on the dried source reducing agent by adopting a chemical vapor deposition method to obtain an intermediate; a2, performing high-temperature pyrolysis on the intermediate in a protective gas atmosphere to form a nitrogen-doped carbon coating layer (CN) on the surface of the zero-valent iron, thereby obtaining the zero-valent iron reducing agent with a coating structure; wherein the source reducing agent is nano zero-valent iron or load-type zero-valent iron. In the invention, the reduction activity of the obtained zero-valent iron reducing agent is high by adopting a method of forming CN coating activated zero-valent iron in situ by adopting a vapor deposition-pyrolysis strategy; the CN coating layer coated on the surface of the zero-valent iron nanoparticle can prevent the loss of iron species, and improves the utilization rate and stability of the zero-valent iron, thereby realizing the continuous utilization of the reducing agent.
Description
Technical Field
The invention relates to the field of industrial wastewater treatment, in particular to a zero-valent iron reducing agent and a preparation method and application thereof.
Background
Chromium is widely present in water environments and exists in nature mainly in the form of hexavalent chromium (Cr (VI)) and trivalent chromium (Cr (III)). Wherein, cr (VI) is often generated in the industrial production process, such as electroplating, smelting, leather tanning and the like, and has the characteristics of large discharge amount and high discharge concentration. Cr (VI) is a typical heavy metal, has toxicity 100 times greater than that of Cr (III), is easier to be absorbed by human body, and causes serious damage to human body. Cr (VI) has high accumulation property, can accumulate in human body if being absorbed by human body for a long time, and poison various organs of human body such as kidney, liver, stomach and the like; high concentrations of Cr (VI) also have carcinogenic and mutagenic properties.
Currently, the commonly used Cr (VI) treatment methods mainly include adsorption-reduction, chemical reduction, ion exchange, and photocatalytic reduction. The negative effects of high energy consumption, low efficiency, secondary pollution and the like are unavoidable in the application of the technologies. If the activated carbon is used for adsorbing Cr (VI), the adsorbent needs to be regenerated and replaced after reaching saturation, and the cost is high. The chemical precipitation method is to reduce Cr (VI) into Cr (III) by using a reducing agent, then add lime or sodium hydroxide to generate precipitate and remove the precipitate. The ion exchange method for treating Cr (VI) in water body mainly utilizes ion exchange resin to exchange with Cr (VI) ions, and has the defects that the resin used in the method is easy to be polluted and is invalid, and impurity ions such as sodium, iron and the like in regenerated waste liquid cannot be directly recycled, so that secondary pollution is caused when the regenerated waste liquid is discharged into the environment. The photo/electro-catalytic reduction method is based on the efficient reduction of Cr (VI) by the catalyst under the condition of energy input, but consumes a large amount of energy and has low economic benefit.
The nano zero-valent iron (Fe 0) has the advantages of low cost, environmental friendliness, low Fe II/Fe0 electrode potential (-0.44V vs. SHE) and the like, and is widely applied to Cr (VI) reduction, and the mechanism is that the strong oxidizing Cr (VI) is directly reduced by Fe 0 and the Fe is oxidized. However, the existing nano zero-valent iron reducing agent has low reduction efficiency, and the recycling of the reducing agent is difficult to realize.
Disclosure of Invention
The invention aims to solve the problems that the zero-valent iron reducing agent in the prior art is low in reducing efficiency and difficult to recycle, and provides a zero-valent iron reducing agent, a preparation method and application thereof.
The inventor finds that the existing nano zero-valent iron reducing agent has low reducing efficiency, and the recycling of the reducing agent is difficult to realize mainly for the following reasons: the inert ferric oxide films (such as FeO x and FeOOH) generated by the contact of Fe 0 with air prevent the reaction from proceeding and inhibit the activity; (2) The large-size block structure makes Fe in the bulk phase difficult to be utilized, resulting in reduced utilization of Fe; (3) The dissolution and loss of Fe species cause the waste of Fe resources and secondary pollution.
The inventor further researches and discovers that the zero-valent iron nanoparticle with the carbon-doped nitrogen (CN) coating, namely the zero-valent iron reducing agent, can be prepared by adopting a vapor deposition-pyrolysis technology to activate a source reducing agent (zero-valent iron), and has excellent reduction efficiency and stability, and high stability, so that the recovery, regeneration and reuse of the reducing agent can be realized.
In order to achieve the above object, the present invention provides in one aspect a method for preparing a zero-valent iron reducing agent, the method comprising the steps of:
A1, soaking a source reducing agent in a sodium persulfate solution, drying, and then adopting a chemical vapor deposition method to polymerize and deposit an aniline monomer on the dried source reducing agent to obtain an intermediate;
A2, performing high-temperature pyrolysis on the intermediate in a protective gas atmosphere to form a nitrogen-doped carbon coating layer on the surface of the zero-valent iron, thereby obtaining the zero-valent iron reducing agent with a coating structure;
wherein the source reducing agent is nano zero-valent iron or load-type zero-valent iron.
Preferably, in step A1, the deposition process includes: and respectively placing the dried source reducing agent and aniline monomer on two sides of a tube furnace, and sealing for deposition.
Preferably, the mass ratio of the source reducing agent to the aniline monomer is 1: 2-1: 10.
Preferably, the concentration of the sodium persulfate solution is 0.15-0.25 g/mL.
Preferably, the conditions of the chemical vapor deposition include: the deposition temperature is 40-80 ℃, and the deposition time is 8-12 h.
Preferably, in step A2, the shielding gas is nitrogen or argon.
Preferably, the operating conditions of the pyrolysis include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h.
Preferably, the supported zero-valent iron is porous carbon supported zero-valent iron or nitrogen-doped porous carbon supported zero-valent iron, preferably nitrogen-doped porous carbon supported zero-valent iron.
Preferably, the method further comprises preparing the nitrogen-doped porous carbon-loaded zero-valent iron according to the following procedure:
B1, uniformly mixing ferric trichloride hexahydrate, 2-amino terephthalic acid and N, N-dimethylformamide, performing hydrothermal reaction, and then washing, centrifuging and drying to obtain a mixture;
And B2, carbonizing the mixture at a high temperature in a protective atmosphere to obtain the nitrogen-doped porous carbon-loaded zero-valent iron.
Preferably, in the step B1, the mass ratio of the ferric trichloride hexahydrate to the 2-amino terephthalic acid is 1:3~3:1.
Preferably, the temperature of the hydrothermal reaction is 100-200 ℃, and the reaction time is 18-24 hours.
Preferably, the operating conditions for carbonizing the high temperature include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h.
In a second aspect the present invention provides a zero-valent iron reducing agent produced by the method of producing a zero-valent iron reducing agent as described above.
In a third aspect the present invention provides the use of a zero-valent iron reducing agent, produced by a method as described above, for the treatment of oxidising pollutants in a body of water.
Preferably, the oxidative contaminant is bromate, dichromate or selenate.
In a fourth aspect the present invention provides a method of treating hexavalent chromium in a water body by treating the water body containing hexavalent chromium contaminants with a zero valent iron reducing agent, the zero valent iron reducing agent being prepared by a method as described above.
Preferably, the method comprises the steps of: adding a zero-valent iron reducing agent into a water body containing hexavalent chromium pollutants, adjusting the pH value of the water body to 1.5-3, and performing a reduction reaction to remove hexavalent chromium in the water body.
The invention has the advantages and beneficial effects that:
(1) In the invention, the reduction activity of the zero-valent iron is improved by adopting a method of forming the CN coating activated zero-valent iron in situ by adopting a vapor deposition-pyrolysis strategy, so that the reduction activity of the obtained zero-valent iron reducing agent is high, and the defect that the activity is sacrificed for replacing the stability in the traditional coating technology is overcome;
(2) The CN coating layer coated on the surface of the zero-valent iron nanoparticle can prevent the loss of iron species, and improves the utilization rate and stability of zero-valent iron, so that the continuous utilization of the reducing agent can be realized by utilizing carbothermic reaction and carbon addition regeneration;
(3) The zero-valent iron reducing agent synthesized by the invention is used for reducing Cr (VI) in water, and can efficiently remove the toxicity of the Cr (VI); in the use process, the method can be carried out at normal temperature and normal pressure without any other special equipment conditions, and has simple operation and wide application range;
(4) Each step in the preparation method of the zero-valent iron reducing agent is a basic chemical process, and the preparation method is easy to operate; the source reducing agent only contains iron element, so the material is easy to obtain, and the technical feasibility is realized;
(5) The invention relies on a chemical vapor deposition-pyrolysis strategy, and the method is applied to commercial nano zero-valent iron, load-type zero-valent iron and other source reducing agents, so that the reduction performance of the nano zero-valent iron can be effectively improved, and the nano zero-valent iron has universality.
Drawings
FIG. 1 is a transmission electron micrograph of the product obtained in each step of example 1;
FIG. 2 is an atomic force microscope image of the CN coating and the zero-valent iron reducing agent in example 1;
FIG. 3 is an XRD pattern of the source reducing agent, the zero-valent iron reducing agent, and the product of acid treatment of the zero-valent iron reducing agent in example 1;
FIG. 4 is a Raman spectrum of the source reducing agent, the zero-valent iron reducing agent, the product of acid treatment of the zero-valent iron reducing agent prepared in example 1, and the zero-valent iron reducing agent prepared in example 2 in example 1;
FIG. 5 is a UPS curve for the source reductant and zero valent iron reductant of example 1, and calculated work functions;
FIG. 6 is a Nyquist plot of the source reductant and the zero-valent iron reductant of example 1;
FIG. 7 is a graph showing the magnetic saturation and magnetic separation effects of the source reducing agent and the zero-valent iron reducing agent obtained in example 1, and the zero-valent iron reducing agent after use in application example 1;
FIG. 8 is a graph showing the effect of the treatment on Cr (VI) in application example 1, application comparative examples 1 to 3, and the results of the reduction performance test of each reducing agent;
FIG. 9 is a graph showing the results of the cycle performance and regeneration effect test of application example 1, and the reduction performance test of the reducing agent;
FIG. 10 is a graph showing the effect of application examples 1-4 on the treatment of Cr (VI) in a body of water;
FIG. 11 is a graph showing the effect of application example 1 and application examples 5 to 6 on the treatment of Cr (VI) in a water body;
FIG. 12 is a graph showing the effect of application example 7 and application comparative example 4 on the treatment of Cr (VI) in a water body;
FIG. 13 is a graph showing the effect of application example 8 and application comparative example 5 on the treatment of Cr (VI) in a water body;
FIG. 14 is a graph showing the effect of comparative example 6 on the treatment of Cr (VI) in a water body.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The invention provides a preparation method of a zero-valent iron reducing agent, which comprises the following steps:
A1, soaking a source reducing agent in a sodium persulfate solution, drying, and then adopting a chemical vapor deposition method to polymerize and deposit an aniline monomer on the dried source reducing agent to obtain an intermediate;
A2, performing high-temperature pyrolysis on the intermediate in a protective gas atmosphere to form a nitrogen-doped carbon coating layer on the surface of the zero-valent iron, thereby obtaining the zero-valent iron reducing agent with a coating structure;
wherein the source reducing agent is nano zero-valent iron or load-type zero-valent iron.
When the source reducing agent is supported zero-valent iron, the method further includes, before step A1: the source reducing agent is milled to form a uniform powder for uniform deposition.
In the invention, the nitrogen-doped carbon coating layer (CN coating layer) is obtained by chemical vapor deposition-pyrolysis of precursor aniline monomers, and the zero-valent iron precursor is obtained by carbonization of an Fe-based metal organic framework. In addition, the iron content in the zero-valent iron reducing agent is 20-80%.
In a specific embodiment, in step A1, the depositing includes: and respectively placing the dried source reducing agent and aniline monomer on two sides of a tube furnace, sealing, and depositing to obtain an intermediate.
In a specific embodiment, the mass ratio of the source reducing agent to the aniline monomer is 1: 2-1: 10, in particular, may be 1: 2. 1:4. 1: 5. 1:7 or 1:10, preferably 1:4.
In a specific embodiment, the sodium persulfate solution can have a concentration of 0.15 g/mL, 0.18 g/mL, 0.20 g/mL, or 0.25 g/mL.
In a preferred embodiment, the chemical vapor deposition temperature may be 40 ℃, 45 ℃, 50 ℃, 54 ℃ or 60 ℃ for a time of 8 h, 10 h, 11 h or 12 h.
In a preferred embodiment, in step A2, the shielding gas is nitrogen or argon.
In a preferred embodiment, in step A2, the operating conditions of the pyrolysis include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h. In the pyrolysis process, the inert oxide film on the surface of the zero-valent iron particles can be removed, so that the activity of the zero-valent iron is improved.
Wherein the loaded zero-valent iron is porous carbon loaded zero-valent iron (Fe 0/C) or nitrogen-doped porous carbon loaded zero-valent iron (Fe 0/CN), and is preferably nitrogen-doped porous carbon loaded zero-valent iron.
The method for preparing the nitrogen-doped porous carbon-loaded zero-valent iron is not limited, and can be obtained by purchasing or conventional preparation methods in the field. Preferably, the nitrogen-doped porous carbon-loaded zero-valent iron is prepared according to the following procedure:
Step B1, uniformly mixing ferric trichloride hexahydrate, 2-amino terephthalic acid and N, N-dimethylformamide, performing hydrothermal reaction, washing, centrifuging and drying to obtain a mixture,
And step B2, carbonizing the mixture at a high temperature in a protective atmosphere to obtain the nitrogen-doped porous carbon-loaded zero-valent iron.
In a specific embodiment, in step B1, the mass ratio of the ferric trichloride hexahydrate to the 2-aminoterephthalic acid is 1:3~3:1, that is, may be 1: 3. 1.5: 3. 3: 3. 3:2 or 3:1, preferably 3:1.
In a specific embodiment, in step B1, 2-aminoterephthalic acid and N, N-Dimethylformamide (DMF) are first mixed to obtain a 2-aminoterephthalic acid solution, and then ferric trichloride hexahydrate is added to carry out hydrothermal reaction. Preferably, the temperature of the hydrothermal reaction is 100-200 ℃, and the reaction time is 18-24 hours.
In a preferred embodiment, the operating conditions for carbonizing the high temperature include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h.
According to the invention, aniline is used as a precursor, a source reducing agent is soaked in sodium persulfate solution and dried, the source reducing agent and aniline monomers are placed in a tube furnace together, volatilized aniline molecules are captured through vapor deposition, and then oxidative polymerization is carried out, namely, the surface of the source reducing agent is coated with a layer of Polyaniline (PANI), and a uniform CN coating layer is formed after pyrolysis at a high temperature and coated on the surface of the zero-valent iron nanoparticle, namely, the zero-valent iron reducing agent.
The invention also provides a zero-valent iron reducing agent, which is prepared by the preparation method of the zero-valent iron reducing agent.
The invention also provides application of the zero-valent iron reducing agent in treating oxidized pollutants in water, wherein the zero-valent iron reducing agent is prepared by the method.
In a specific embodiment, the oxidized contaminant is bromate, chromate, or selenate.
In addition, the invention also provides a method for treating hexavalent chromium in water, which comprises the following steps: a body of water containing hexavalent chromium contaminants is treated with a zero-valent iron reducing agent, the zero-valent iron reducing agent being produced by a method as described above.
In a preferred embodiment, the method comprises the steps of: adding a zero-valent iron reducing agent into a water body containing hexavalent chromium pollutants, adjusting the pH value of the water body to 1.5-3, and carrying out reduction reaction. More preferably, the pH of the body of water is adjusted to 2.
The use amount of the zero-valent iron reducing agent is not limited, and can be determined according to the concentration of specific pollutants, and in the invention, when the initial concentration of hexavalent chromium pollutants is 5-15 mg/L and the use amount of the zero-valent iron reducing agent is 30-50 mg/L, the removal rate of hexavalent chromium pollutants in a water body can be over 80% within 50-120 min.
The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.
Example 1
This example is intended to illustrate the method of preparing the zero-valent iron reducing agent of the present invention.
(1) Uniformly mixing 2-amino terephthalic acid and DMF, then adding ferric trichloride hexahydrate, uniformly stirring, performing hydrothermal reaction at 110 ℃ for 24 h, and then washing, centrifuging and drying to obtain a mixture, wherein the mass ratio of the ferric trichloride hexahydrate to the 2-amino terephthalic acid is 3:1, a step of;
(2) Carbonizing the mixture at a flow rate of N 2 of 150 mL/min and a temperature of 900 ℃ for 5 h to obtain a source reducing agent, namely Fe 0/CN;
(3) Grinding the source reducing agent, soaking and drying the ground source reducing agent by using a sodium persulfate solution with the concentration of 0.15 g/mL, putting the ground source reducing agent and an aniline monomer into a tube furnace together, sealing the two sides of the tube furnace, and depositing 12 h at 50 ℃ to obtain an intermediate, wherein the mass ratio of the source reducing agent to the aniline monomer is 1:4, a step of;
(4) And pyrolyzing the intermediate for 5 hours under the conditions that the flow rate of N 2 is 150 mL/min and the temperature is 800 ℃, so as to obtain the CN coated iron zero-valent iron reducing agent, namely the zero-valent iron reducing agent, which is marked as Fe 0 @CN.
Example 2
This example is intended to illustrate the method of preparing the zero-valent iron reducing agent of the present invention.
The procedure of example 1 was followed, except that the source reducing agent in step (3) was porous carbon-loaded zero-valent iron (Fe 0/C), designated Fe 0/C@CN, prepared by dissolving ferric nitrate hexahydrate and trimesic acid in deionized water, stirring 30 min, transferring to a hydrothermal reaction vessel, and hydrothermally reacting 12 h at 180 ℃. Cooling to room temperature, filtering the mixture, washing with deionized water and methanol, and drying to obtain a mixture MIL-100 (Fe); MIL-100 (Fe) was carbonized under nitrogen to give Fe 0/C.
Example 3
This example is intended to illustrate the method of preparing the zero-valent iron reducing agent of the present invention.
In contrast to the implementation of the method described in example 1, the source reducing agent in step (3) is commercially available zero valent iron nZVI, as will be appreciated, the adaptive deletion of steps (1) and (2).
Example 4
(1) Uniformly mixing 2-amino terephthalic acid and DMF, then adding ferric trichloride hexahydrate, uniformly stirring, performing hydrothermal reaction at 100 ℃ for 20 h, and then washing, centrifuging and drying to obtain a mixture, wherein the mass ratio of the ferric trichloride hexahydrate to the 2-amino terephthalic acid is 3:3:
(2) Carbonizing 8 h under the conditions that the flow rate of N 2 is 100 mL/min and the temperature is 700 ℃ to obtain a source reducing agent which is marked as Fe 0/CN;
(3) Grinding the source reducing agent, soaking and drying the ground source reducing agent by using a sodium persulfate solution with the concentration of 0.2 g/mL, putting the ground source reducing agent and an aniline monomer into a tube furnace, sealing two sides of the tube furnace, and depositing 10 h at the temperature of 40 ℃ to obtain an intermediate, wherein the mass ratio of the source reducing agent to the aniline monomer is 1:10;
(4) And pyrolyzing the intermediate at the flow rate of N 2 of 200 mL/min and the temperature of 1000 ℃ of 6h to obtain the CN coated iron zero-valent iron reducing agent, namely the zero-valent iron reducing agent.
Example 5
(1) Uniformly mixing 2-amino terephthalic acid and DMF, then adding ferric trichloride hexahydrate, uniformly stirring, performing hydrothermal reaction at 200 ℃ for 18 h, and then washing, centrifuging and drying to obtain a mixture, wherein the mass ratio of the ferric trichloride hexahydrate to the 2-amino terephthalic acid is 1:3, a step of;
(2) Carbonizing the mixture under the conditions of N 2 flow rate of 200 mL/min and temperature of 1000 ℃ for 6h to obtain a source reducing agent, namely Fe 0/CN;
(3) Grinding the source reducing agent, soaking and drying the ground source reducing agent by using a sodium persulfate solution with the concentration of 0.25 g/mL, putting the ground source reducing agent and an aniline monomer into a tube furnace together, sealing the two sides of the tube furnace, and depositing 8 h at the temperature of 80 ℃ to obtain an intermediate, wherein the mass ratio of the source reducing agent to the aniline monomer is 1:2;
(4) And pyrolyzing the intermediate at the flow rate of N 2 of 100 mL/min and the temperature of 700 ℃ of 8 h to obtain the CN coated iron zero-valent iron reducing agent, namely the zero-valent iron reducing agent.
Comparative example 1
The procedure described in example 1 was followed, except that the aniline monomer was an oxidative polymerization cladding-pyrolysis synthesis of zero-valent iron reducing agent in the liquid phase. Specifically, the method comprises the following steps:
(1) Source reductant Fe 0/CN was prepared by the method described in example 1;
(2) Sodium persulfate was dissolved in 1M hydrochloric acid solution, fe 0/CN was dispersed in the above solution, and after stirring for 0.5: 0.5 h, the purified aniline monomer was dropwise added to the above mixture. Continuously stirring for 5h, and finally enabling the material to be dark green;
(3) The materials are magnetically separated from the solution, filtered and washed for a plurality of times, and are placed in a tubular furnace for pyrolysis 5 h under the conditions of N 2 atmosphere (the flow rate is 150 mL/min) and the temperature is 800 ℃. The final product is Fe 0 @CN reducing agent synthesized by a liquid phase deposition-pyrolysis method.
Application example 1
The application example is used for explaining the method for treating hexavalent chromium in water (namely, application of the zero-valent iron reducing agent).
The zero-valent iron reducing agent prepared in the example 1 is added into a water body containing hexavalent chromium pollutants, wherein the initial concentration of Cr (VI) in the water body is 10.4 mg/L, the concentration of the reducing agent is 40 mg/L, the pH value of the water body is adjusted to 2, and the water body is subjected to reduction reaction at normal temperature and normal pressure to 2h.
Application examples 2 to 4
The process was conducted in accordance with application example 1, except that in application example 2, the initial concentration of Cr (VI) in the water was 6.2 mg/L; in application example 3, the initial concentration of Cr (VI) in the water body is 8.2 mg/L; the initial concentration of Cr (VI) in the water in application example 4 is 12.4 mg/L.
Application examples 5 to 6
The process was conducted in accordance with application example 1, except that in application example 5, the concentration of the reducing agent in the water body was 32 mg/L; in application example 6, the concentration of the reducing agent was 51 mg/L.
Application example 7
The procedure of application example 1 was followed, except that the reducing agent used was the zero-valent iron reducing agent prepared in example 2 (i.e., the source reducing agent was Fe 0/C).
Application example 8
The procedure of application example 1 was followed except that the reducing agent used was the zero-valent reducing agent prepared in example 3 (i.e., the source reducing agent was commercial zero-valent iron).
Comparative examples 1 to 3 were applied
The procedure of application example 1 was followed, except that the reducing agent used in comparative example 1 was pure CN material; the reducing agent used in comparative example 2 was Fe 0/CN obtained in step (2) of example 1; the reducing agent used in comparative example 3 was obtained after the acid treatment of the zero-valent iron reducing agent obtained in example 1 (i.e., after stirring the zero-valent iron reducing agent in a hydrochloric acid solution of 2M for 3 h, washing the resulting solid to neutrality, and drying the resulting solid), and was designated as Fe 0 @ CN-acid treatment.
Comparative example 4 was used
The procedure was followed as in application example 1, except that the reducing agent used was the source reducing agent (Fe 0/C) in example 2.
Comparative example 5 was used
The procedure of application example 1 was followed except that the reducing agent used was the source reducing agent commercial zero valent iron (nZVI) of example 3.
Comparative example 6 was used
The procedure of application example 1 was followed, except that the reducing agent used in comparative example 6 was the zero-valent reducing agent prepared in comparative example 1 (i.e., prepared using an aqueous polymerization-pyrolysis strategy).
Test example 1
The mixture prepared in step (1), the source reducing agent prepared in step (2), the intermediate prepared in step (3) and the zero-valent iron reducing agent prepared in step (4) of example 1 were characterized by using a transmission electron microscope, and the results are shown in fig. 1.
Wherein fig. 1 (a) is an electron microscope image of the mixture. As can be seen from FIG. 1 (a), the resulting product was an iron-based MOFs of regular octahedral structure.
FIG. 1 (b) is an electron microscopic view of the source reducing agent, and it can be seen from FIG. 1 (b) that Fe particles are supported on the surface of porous carbon.
Fig. 1 (c) is an electron microscope image of an intermediate, and as can be seen from fig. 1 (c), the contour of the Fe particles after deposition is blurred, indicating that the Fe particles are effectively coated.
Fig. 1 (d) is an electron microscope image of the zero-valent iron reducing agent, and as can be seen from fig. 1 (d), the state of the coating layer and the particle is not significantly changed after pyrolysis, which indicates that the coating structure is not damaged by pyrolysis.
Further, the zero-valent iron reducing agent was tested to show an iron content of 28.9 wt%.
Test example 2
The CN coating layer prepared in example 1, and the zero-valent iron reducing agent were characterized using an atomic force microscope, and the results are shown in fig. 2.
Wherein, fig. 2 (a) is a graph of characterization results of the CN coating layer, and as can be seen from fig. 2 (a), the thickness of the CN coating layer is about 5 nm a. Fig. 2 (b) is a graph showing the characterization result of the zero-valent iron reducing agent, and as can be seen from fig. 2, the zero-valent iron reducing agent (i.e., the coated Fe 0 nano-particles and the CN coating) is about 28.6 nm, so that the particle size of the Fe particles is about 24 nm.
The results of X-ray diffraction of the source reducing agent (Fe 0/CN), the zero-valent iron reducing agent (Fe 0 @CN) and the product obtained by acid treatment of the zero-valent iron reducing agent (Fe 0 @CN-acid treatment) obtained in example 1 are shown in FIG. 3. The acid treatment step was carried out by stirring the Fe 0 @ CN reducing agent in a hydrochloric acid solution of 2M for 3 h, washing the solution until the washing solution became neutral, and drying the obtained solid.
The patterns corresponding to Fe 0 @CN and Fe 0/CN in FIG. 3 each show characteristic peaks of Fe of similar intensity, because the thickness of the carbon coating layer is insufficient to affect the strength of Fe, and after the acid treatment, fe particles are removed, so that the characteristic peaks disappear.
Test example 3
The source reducing agent (Fe 0/CN) obtained in example 1, the zero-valent iron reducing agent (Fe 0 @ CN), the product obtained by acid-treating the zero-valent iron reducing agent obtained in example 1 (Fe 0 @ CN-acid treatment), and the zero-valent iron reducing agent obtained in example 2 were subjected to Raman spectroscopy, and the results are shown in FIG. 4.
As can be seen from the comparison of fig. 4, the graphitization degree of the zero-valent iron reducing agent obtained after coating CN is higher than that of the source reducing agent before coating, which is advantageous for the improvement of the activity. However, the supported Fe 0/C in example 2 was less graphitized after being coated because the pure carbon support was not graphitized easily.
The source reducing agent (Fe 0/CN) and the zero-valent iron reducing agent (Fe 0 @CN) prepared in example 1 were tested using an ultraviolet electron spectrometer (UPS) and the corresponding work functions were calculated, and the results are shown in FIG. 5.
As can be seen from FIG. 5, the work function of Fe 0 @ CN is lower than that of Fe 0/CN, which characterizes a reduced energy barrier, facilitating the reaction. A similar conclusion was also confirmed by the Nyquist curve, with an impedance of Fe 0 @ CN of 10.03 Ω, lower than Fe 0 @ CN (15.41 Ω) (as shown in FIG. 6).
FIG. 7 is a graph showing the effects of magnetic saturation (a) and magnetic separation (b) of the source reducing agent (Fe 0/CN) and the zero-valent iron reducing agent (Fe 0 @CN) obtained in example 1, and the zero-valent iron reducing agent (Fe 0 @CN-after use) after use in application example 1.
The magnetic saturation levels after use of Fe 0@CN,Fe0/CN and Fe 0 @ CN-shown in FIG. 7 (a) were 12 emu/g,47 emu/g and 49 emu/g, respectively, indicating that the reducing agent after activation and use was more magnetically saturated, facilitating magnetic separation, and sufficient to allow the material to be effectively separated within 3 min (as shown in FIG. 7 (b)).
Test example 4
The treatment effect of Cr (VI) in water body in application example 1 and application comparative examples 1-3 was tested, and the corresponding activity and removal amount of each reducing agent were tested, and the test results are shown in FIG. 8. In fig. 8 to 14, C t/C0 is the ratio of the contaminant concentration at time t to the initial contaminant concentration, INITIAL ACTIVITY is the initial activity, and removal capacity is the removal capacity.
As can be seen from fig. 8, the pure CN material is not effective in removing Cr (VI), which reduction takes place on the reducing agent containing iron. The reaction of the system is the reduction of Cr (VI) with the participation of Fe. The set Cr (VI) can be completely reduced at 70: 70 min by Fe 0 @CN, and the Cr (VI) removal amount of Fe 0/CN is less than 10%, so that the super-high reduction performance is shown. Specific activity and removal comparison data as shown in fig. 8 (b), the activity (2037 mg/g reductant h.l) after coating and the removal of Cr (VI) (0.26 gCr/g reductant) were 75.4 times and 10 times that of Fe 0/CN, respectively, demonstrating that the reduction performance can be greatly improved by activating the source reductant Fe 0/CN using a chemical vapor deposition-pyrolysis strategy.
After repeating the step of application example 14 times, the separated Fe 0 @ CN was subjected to carbon thermal regeneration and carbon addition treatment, wherein the carbon addition treatment was performed as vapor deposition-pyrolysis step ((3) and (4) in example 1). The procedure of example 1 was repeated 1 more times, and the effect of treatment on Cr (VI) and the corresponding activity and removal amount of the reducing agent were tested.
As can be seen from fig. 9, under the same reaction conditions, fe 0 @ CN can maintain high stability through carbon thermal regeneration (same conditions as the synthesis of CN coating) and carbon addition. As shown in fig. 9 (a), the reduction performance of the former three-cycle regeneration reducing agent remains substantially unchanged, while the fourth activity is reduced, mainly because the carbon layer in the material is insufficient to reduce the zero-valent iron, so the performance after the carbon addition treatment is restored to the original level again, as shown in fig. 9 (b) for the specific comparison.
Test example 5
The results of the treatment of Cr (VI) in a body of water using examples 1-4 are shown in FIG. 10, which shows the reduction curves, corresponding primary activities and removal amounts of Cr (VI) at Fe 0 @CN reducing agent at different initial concentrations (6.2 mg/L, 8.2 mg/L, 10.4 mg/L and 12.4 mg/L).
As can be seen from FIG. 10, when the amount of the reducing agent added is 40 mg/L, the reducing agent can completely remove Cr (VI) in 50 min at a concentration of less than 10.4 mg/L (inclusive), and above this concentration, the Cr (VI) cannot be completely removed even if the concentration is prolonged to 120 min (as shown in FIG. 10 (a)), mainly because Fe in the reducing agent is enough to reduce all Cr (VI) below 10.4 mg/L, and the content of Fe above this concentration becomes a limiting factor. Regarding kinetic analysis, the present reaction is adsorption-controlled (as in FIG. 10 (b)), so that as the initial Cr (VI) concentration increases, the activity increases and the amount removed increases until the reducing agent is reacted completely (as in FIG. 10 (c)).
The treatment effect of application example 1 and application examples 5-6 on Cr (VI) in a water body was tested, and the results are shown in FIG. 11, namely, reduction curves of different addition amounts of reducing agents (32 mg/L, 40 mg/L and 51 mg/L) on Cr (VI), corresponding primary activities and removal amounts.
As can be seen from FIG. 11, the result is similar to FIG. 10 in that Cr (VI) is completely reduced in 70 min under the condition of excessive reducing agent, and the reduction amount of Cr (VI) is correspondingly reduced when the amount of reducing agent is insufficient. The amount removed and the initial activity are also consistent with the results of FIG. 10 as shown in FIG. 11 (b).
Test example 6
The effect of application example 7 (Fe 0/C@CN) and application comparative example 4 (Fe 0/C) on the treatment of Cr (VI) in a water body was tested, and the results are shown in FIG. 12, namely, the reduction curve of Fe 0/C reducing agent and corresponding vapor deposition-pyrolysis treatment Fe 0/C@CN reducing agent on Cr (VI), corresponding initial activity and removal amount.
As can be seen from FIG. 12 (a), fe 0/C reduced Cr (VI) less than 10% in 120 min, while Fe 0/C@CN can reach more than 80%. As can be seen from FIG. 12 (b), the corresponding activities and removal amounts of Fe 0/C@CN were 17-fold and 8.5-fold higher than those of Fe 0/C. It is demonstrated that the reduction performance can be greatly improved by activating the source reducing agent Fe 0/C by adopting a chemical vapor deposition-pyrolysis strategy.
The treatment effect of application example 8 and application comparative example 5 on Cr (VI) in a water body was tested, and the results are shown in fig. 13, i.e., the reduction curve of commercial zero-valent iron (nZVI) and the corresponding zero-valent iron reducing agent (nzvi@cn) for vapor deposition-pyrolysis treatment on Cr (VI), the corresponding primary activity and the removal amount.
As can be seen from fig. 13, the activity and the removal amount of the commercial zero-valent iron are greatly improved after the commercial zero-valent iron is activated by the chemical vapor deposition-pyrolysis strategy.
The treatment effect of comparative example 6 on Cr (VI) in a water body was tested, and the results are shown in FIG. 14.
As can be seen from fig. 14, the zero-valent iron reducing agent prepared by the aqueous polymerization-pyrolysis strategy has low reducing activity and low removal amount.
The hexavalent chromium in the water body is treated in the same manner as in example 1 in examples 4 and 5, and the treatment effect is tested, and the results show that the reduction performance of examples 4 and 5 is equivalent to that of example 1, and no description is given here.
In conclusion, after the vapor deposition-pyrolysis strategy provided by the invention is adopted to activate the source reducing agent, the activity of the source reducing agent and the removal amount of pollutants can be greatly improved.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (16)
1. A method of preparing a zero-valent iron reducing agent, the method comprising the steps of:
A1, soaking a source reducing agent in a sodium persulfate solution, drying, and then adopting a chemical vapor deposition method to polymerize and deposit an aniline monomer on the dried source reducing agent to obtain an intermediate;
A2, performing high-temperature pyrolysis on the intermediate in a protective gas atmosphere to form a nitrogen-doped carbon coating layer on the surface of the zero-valent iron, thereby obtaining the zero-valent iron reducing agent with a coating structure;
wherein the source reducing agent is nano zero-valent iron or load-type zero-valent iron.
2. The method of preparing a zero-valent iron reducing agent according to claim 1, wherein in step A1, the depositing process comprises: and respectively placing the dried source reducing agent and aniline monomer on two sides of a tube furnace, and sealing for deposition.
3. The method for producing a zero-valent iron reducing agent according to claim 1 or 2, characterized in that the mass ratio of the source reducing agent to the aniline monomer is 1: 2-1: 10.
4. The method for preparing a zero-valent iron reducing agent according to claim 1, wherein the concentration of the sodium persulfate solution is 0.15-0.25 g/mL.
5. The method for preparing a zero-valent iron reducing agent according to claim 1, wherein the conditions of the chemical vapor deposition include: the deposition temperature is 40-80 ℃, and the deposition time is 8-12 h.
6. The method for producing a zero-valent iron reducing agent according to claim 1, wherein in step A2, the shielding gas is nitrogen or argon.
7. The method of preparing a zero-valent iron reducing agent of claim 1, wherein the operating conditions of the high temperature pyrolysis include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h.
8. The method for preparing a zero-valent iron reducing agent according to claim 1, wherein the supported zero-valent iron is porous carbon supported zero-valent iron.
9. The method for preparing a zero-valent iron reducing agent according to claim 1, wherein the supported zero-valent iron is nitrogen-doped porous carbon supported zero-valent iron.
10. The method of preparing a zero-valent iron reducing agent of claim 9, further comprising preparing the nitrogen-doped porous carbon-loaded zero-valent iron according to the following procedure:
B1, uniformly mixing ferric trichloride hexahydrate, 2-amino terephthalic acid and N, N-dimethylformamide, performing hydrothermal reaction, and then washing, centrifuging and drying to obtain a mixture;
And B2, carbonizing the mixture at a high temperature in a protective atmosphere to obtain the nitrogen-doped porous carbon-loaded zero-valent iron.
11. The method for preparing a zero-valent iron reducing agent according to claim 10, wherein in the step B1, the mass ratio of the ferric trichloride hexahydrate to the 2-amino terephthalic acid is 1:3~3:1.
12. The method for preparing a zero-valent iron reducing agent according to claim 10, wherein in the step B1, the hydrothermal reaction is performed at a temperature of 100-200 ℃ for 18-24 hours.
13. The method for preparing a zero-valent iron reducing agent according to claim 10, wherein in step B2, the operating conditions of the high-temperature carbonization include: the flow rate of the shielding gas is 100-200 mL/min, the temperature is 700-1000 ℃ and the time is 5-8 h.
14. A zero-valent iron reducing agent, characterized by being produced by the method for producing a zero-valent iron reducing agent according to any one of claims 1 to 13.
15. A method of treating hexavalent chromium in a water body, characterized in that the water body containing hexavalent chromium contaminants is treated with a zero-valent iron reducing agent, said zero-valent iron reducing agent being produced by the method of any one of claims 1 to 13.
16. The method of treating hexavalent chromium in a water body according to claim 15, characterized in that said method comprises the steps of: adding a zero-valent iron reducing agent into a water body containing hexavalent chromium pollutants, adjusting the pH value of the water body to 1.5-3, and performing a reduction reaction to remove hexavalent chromium in the water body.
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