CN113368856A

CN113368856A - Preparation method and application of iron pillared montmorillonite composite catalyst

Info

Publication number: CN113368856A
Application number: CN202110618323.7A
Authority: CN
Inventors: 吴宏海; 卢鹏澄
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2021-06-03
Filing date: 2021-06-03
Publication date: 2021-09-10
Anticipated expiration: 2041-06-03
Also published as: CN113368856B

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of an iron pillared montmorillonite composite catalyst.

Description

Preparation method and application of iron pillared montmorillonite composite catalyst

Technical Field

Background

The progress of science and technology not only brings convenience to people, but also provides colorful articles, but people often generate a large amount of waste gas, waste liquid and solid waste, namely pollutants, in production and life while enjoying modern results. The unreasonable emission of pollutants causes harmful substances to enter soil, enter rivers, enter Wangyang and enter animal and plant bodies along with rainwater. In the ecological system where the rings are buckled, the pollution of harmful substances will probably cause ecological damage, and therefore, people must be concerned highly. Water is a source of life, and water pollution not only can induce diseases and harm human health, but also can influence social productivity, thereby reducing economic benefits, increasing the cost of a water purification process and reducing the quality of effluent water.

In soil/water body pollution, nitroaromatics are one of the non-degradable toxic and harmful chemicals, and the nitro (-NO) group₂) The biochemical stability of the compound is enhanced due to the strong electron withdrawing effect, and the compound is widely used as an intermediate of various synthetic compounds such as fuel, pesticide, medicine, dye, rubber, plastic additive, petrochemical industry and the like. Wherein, nitrophenols and derivatives thereof have obvious mutagenicity and carcinogenicity to organisms, and can also cause abnormal symptoms of nervous system, anemia, liver diseases and the like, because the nitrophenols and the derivatives thereof can enter water environment through various ways, such as the nitrophenols and the derivatives thereof can be discharged into water body and soil from industrial waste water of textile industry and dye house through dyes, and along with the rapid growth of' fashion clothing production, the dye waste water is rapidly increased, so that the nitrophenols and the derivatives thereof are widely detected in river water body, and the unmistable risk or harm is brought to the health and biological safety of local residents. Currently, these poisons have been listed as priority control pollutants. Therefore, in order to effectively alleviate or eliminate the harm of the nitroaromatic hydrocarbons to the environment, the method has important practical significance for finding a high-efficiency and low-cost treatment technology.

At present, the treatment method of the sewage containing the nitro compounds mainly comprises four methods: physical, chemical, biological, and combination techniques. The independent physical, chemical or biological treatment of nitrophenol wastewater has certain limitations, so that the most of the existing sewage treatment plants adopt a combined technology to achieve the optimal water outlet effect and meet the treatment cost budget. Although the four treatment methods can quickly remove the residual nitroaromatic pollutants in the environment, the methods are only suitable for in-situ remediation of the nitroaromatic pollutants which may exist, but cannot effectively treat the nitroaromatic pollutants deposited under anoxic conditions such as river sediment, soil and underground aquifers. Therefore, there is an urgent need to develop a sewage treatment method that can be applied under practical environmental conditions without introducing new pollutants.

Montmorillonite (Mt) is a clay mineral with a 2:1 layered structure, and is inexpensive and abundant in storage, because the montmorillonite has a basal plane and an edge

Acid and Lewis acid, which play an important promoting role in the conversion of high-selectivity organic matters in the acid catalytic reaction; at the same time, the fine-grained clay particles of montmorillonite enable an increase in the surface area per unit mass, i.e. a smaller particle size (0.002-0.001mm) enables a higher surface area. Therefore, the montmorillonite can be used as an excellent substrate material for preparing a catalyst material. However, the surface of the iron pillared montmorillonite (FPMt) material prepared by the existing method has a plurality of acid sites, and the acid sites and nitrophenol pollutants compete for electrons together, so that the catalytic reduction process is not facilitated.

The treatment modes of acid activation, heating, cation fixation and the like greatly influence the surface properties (including surface charge, acidity, structure and the like) of the clay mineral, thereby influencing the practical application potential of the clay mineral. It is particularly noted that the heat treatment not only modifies the lamellar structure and surface properties of the montmorillonite, but is also essential for the growth of the supported iron oxide crystals. However, too high a temperature may destroy the layered structure and surface functional groups of the montmorillonite, thereby being disadvantageous for the redox reaction.

Based on the oxidation characteristic of the chemical structure of the nitroaromatic hydrocarbon and in combination with the performance of promoting Fe (II) reduction by mineral surface catalysis discovered by the previous research, a treatment system for reducing and converting nitroaromatic pollutants by ferrous iron under the catalytic drive of the mineral surface is constructed. Meanwhile, considering that the montmorillonite can be used as a supporting material, the patent aims to develop and optimize the preparation method of the iron pillared montmorillonite composite material.

Some methods for preparing iron pillared montmorillonite (FPMt) are reported, but the surfaces of the prepared iron pillared montmorillonite have a plurality of acid sites, and the acid sites compete with nitrophenol pollutants for electrons, so that the catalytic reduction process is not facilitated.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method of the iron pillared montmorillonite composite catalyst, the surface acid sites of the prepared iron pillared montmorillonite composite catalyst are effectively reduced, the catalytic degradation of nitrophenol pollutant is facilitated, and the pollution problem of nitrophenol wastewater is solved.

In order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides a preparation method of an iron pillared montmorillonite composite catalyst, which comprises the following steps:

s1, according to [ Fe ]]Mixing montmorillonite suspension with sodium-based montmorillonite content of 2% and iron pillared agent solution at a ratio of 5-15 mmoL/g to obtain iron pillared montmorillonite suspension, wherein the iron pillared agent solution contains Na with concentration of 0.2mol/L₂CO₃And Fe (NO) at a concentration of 0.2mol/L₃)₃；

S2, aging the iron pillared montmorillonite suspension obtained in the step S1, centrifuging, washing, drying, grinding, and calcining at 200-400 ℃ for 1-3 hours to obtain the titanium pillared montmorillonite composite material.

Preferably, the calcining temperature of step S2 is 300 ℃ and the time is 2 h.

Preferably, in step S1, a montmorillonite suspension having a sodium-based montmorillonite content of 2% and an iron pillared agent solution are mixed at a ratio of [ Fe ]/Mt ═ 10mmoL/g to prepare an iron pillared montmorillonite suspension.

Preferably, the aging of step S2 is to stand at 60 ℃ for not less than 24 h. Further, the aging was carried out at 60 ℃ for 24 hours.

Preferably, the grinding in step S2 is to be 100-200 mesh. Further, the grinding is to 200 mesh.

Preferably, the centrifugation of step S2 is 4000r/min for 6 min.

Preferably, the purity of the sodium montmorillonite is more than 90%, and the particle size is 100-200 meshes.

The invention also provides the iron pillared montmorillonite composite catalyst prepared by the method.

The invention also provides application of the iron pillared montmorillonite composite catalyst in degrading nitroaromatic pollutants.

Preferably, the nitroaromatic contaminants include, but are not limited to, o-nitrophenol.

Compared with the prior art, the invention has the beneficial effects that:

the iron pillared montmorillonite composite catalyst prepared by scientifically blending the proportion of montmorillonite and the iron pillared agent and reasonably calcining (calcining at low temperature under aerobic condition) not only keeps relatively complete surface structure appearance of montmorillonite, but also generates hematite with relatively good crystallization, thereby improving the conductivity of the original material, and keeps a certain amount of surface hydroxyl with certain strength, so that a Fe (II) surface complex with high reduction activity can be formed by the action of the montmorillonite and the iron pillared agent in a water phase, and the nitro-arene pollutant can be more favorably degraded. Its advantages are:

(1) the hydroxyl iron cations are firmer between montmorillonite layers or on the surface through reasonable calcination, the transformation and growth of the surface iron oxide to hematite mineral phase are promoted, and the stability and the activity of the iron pillared montmorillonite composite catalyst are improved;

(2) the hematite phase is a core mineral phase component of a reduction catalytic reaction, the higher the exposure rate of the hematite phase is, the better the catalytic effect of surface drive is, and under the calcination temperature of 200-400 ℃ (especially the calcination temperature of 300 ℃), the layered structure of the iron pillared montmorillonite composite catalyst cannot be damaged, so that the montmorillonite section without hematite coverage cannot be exposed in a large area, and the catalytic effect is effectively improved;

(3) the montmorillonite surface has some solid acid sites which are not beneficial to the catalytic reduction conversion or removal process of pollutants, but after the calcination of the invention, the acid sites on the montmorillonite surface are irreversibly reduced, thereby being more beneficial to the catalytic degradation of nitrophenol pollutant pollutants.

Drawings

FIG. 1 is an XRD pattern of iron pillared montmorillonite (a shows an XRD contrast pattern of a calcined iron pillared montmorillonite composite material and an uncalcined iron pillared montmorillonite composite material; b shows an XRD pattern of iron pillared montmorillonite composite materials at different calcination temperatures; c is a partial enlarged view of the pattern b);

FIG. 2 is an SEM image of iron pillared montmorillonite (a represents FPMt200, b represents FPMt300, c represents FPMt400, d represents FPMt500, and e and f represent element distribution);

FIG. 3 is a graph showing the effect of catalytic reduction of iron pillared montmorillonite p-o-nitrophenol (2-NP) (a shows the experimental results of catalytic reduction conversion of iron pillared montmorillonite to 2-NP at different iron contents; b shows the experimental results of reduction conversion of iron pillared montmorillonite (example 1) to 2-NP at different temperatures);

FIG. 4 is an adsorption diagram of iron pillared montmorillonite p-o-nitrophenol;

FIG. 5 is a graph of pyridine FTIR of iron pillared montmorillonite.

Detailed Description

The following further describes the embodiments of the present invention. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The experimental procedures in the following examples were carried out by conventional methods unless otherwise specified, and the test materials used in the following examples were commercially available by conventional methods unless otherwise specified.

Example 1 preparation of iron pillared montmorillonite composite

(1) Preparation of a smectite suspension

Weighing 5g of sodium-based montmorillonite (with the purity of more than 90 percent and the particle size of 100-200 meshes), dispersing in 245mL of deionized water, and vigorously stirring at room temperature (about 25 ℃) for 1h to obtain a montmorillonite suspension with the sodium-based montmorillonite content of 2%;

(2) preparation of iron pillared agent

5.3g of Na are weighed₂CO₃Slowly adding 250mL of Fe (NO) with the concentration of 0.2mol/L₃)₃In aqueous solution (Na)₂CO₃The concentration of the iron pillared polymer is 0.2mol/L), and vigorously stirring for 2 hours to form a semitransparent reddish brown iron pillared agent solution, and standing and aging for 24 hours at room temperature;

(3) preparing iron pillared montmorillonite suspension:

mixing the montmorillonite suspension and the iron pillared agent solution according to the proportion of [ Fe ]/Mt ═ 10mmoL/g ([ Fe ] represents iron element), then vigorously stirring for 2h to make the mixture fully uniform to obtain iron pillared montmorillonite suspension, and standing and aging for 24h at 60 ℃;

(4) drying

After aging for 24h, the solution was centrifuged and washed with deionized water at 4000r/min for 6min (to remove nitrate and avoid introducing excessive impurities), and the wet cake obtained was dried in an oven at 80 ℃.

(5) Grinding and calcining

Grinding a sample and passing through a 200-mesh sieve, and dividing the powder into two parts, wherein one part is the titanium pillared montmorillonite composite material which is not calcined and is marked as initial FPMt; and putting the other part into a covered crucible, and putting the crucible into a muffle furnace at 100-500 ℃ for calcining for 2 hours to prepare the calcined titanium pillared montmorillonite composite material. Wherein, the titanium pillared montmorillonite composite materials with the calcination temperature of 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃ and 800 ℃ are respectively named as FPMt100, FPMt200, FPMt300, FPMt400, FPMt500 and FPMt 800.

Example 2 preparation of iron pillared montmorillonite composite

(1) Preparation of a smectite suspension

(2) preparation of iron pillared agent

2.65g of Na are weighed₂CO₃Slowly add 125mL of Fe (NO) with a concentration of 0.2mol/L₃)₃In the water solution, vigorously stirring for 2h to form a semitransparent reddish brown iron pillared agent solution, and standing and aging for 24h at room temperature;

(3) preparation of iron pillared montmorillonite suspension

Mixing the sodium-based montmorillonite suspension and the iron pillared agent solution according to the proportion of [ Fe ]/Mt ═ 5mmoL/g, then violently stirring for 2h to make the mixture fully and uniformly to obtain the iron pillared montmorillonite suspension, and standing and aging for 24h at 60 ℃;

(4) drying

After aging for 24h, centrifuging the suspension, washing the suspension for several times by using deionized water, wherein the centrifugal rotating speed is 4000r/min, the centrifugal time is 6min, and drying the obtained wet cake in a drying oven at 80 ℃;

(5) grinding

The sample is ground and passed through a 200-mesh sieve to obtain the titanium pillared montmorillonite composite material.

Example 3 preparation of iron pillared montmorillonite composite

(1) Preparation of a smectite suspension

(2) preparation of iron pillared agent

Weighing 7.95g of Na₂CO₃Slowly add 375mL of Fe (NO) with a concentration of 0.2mol/L₃)₃Stirring vigorously in the water solution for 2h to form a semitransparent reddish brown iron pillared agent solution, and standing and aging at room temperature for 24 h;

(3) preparation of iron pillared montmorillonite suspension

Mixing the montmorillonite suspension and the iron pillared agent solution according to the proportion of [ Fe ]/Mt ═ 15mmoL/g, then violently stirring for 2 hours to make the mixture fully and uniformly to obtain the iron pillared montmorillonite suspension, and standing and aging for 24 hours at the temperature of 60 ℃;

(4) drying

After aging for 24h, centrifuging the solution and washing the solution for several times by using deionized water, wherein the centrifugal rotating speed is 4000r/min, the centrifugal time is 6min, and the obtained wet cake is placed in an oven to be dried at the temperature of 80 ℃;

(5) grinding

Experimental example 1 XRD analysis

The titanium pillared montmorillonite composite material in example 1 was subjected to XRD analysis using an Ultima type IV X-ray powder diffractometer (japan chemicals) with copper ka radiation at 40kV and 40mA to analyze the mineral phase composition. The slide is used as a sample testing platform, the scanning angle (2 theta) ranges between 3 DEG and 70 DEG, and the scanning speed is 12 DEG/min.

The XRD diffraction peak at 2 θ -6.494 ° corresponds to the (001) characteristic crystal plane of montmorillonite (JCPDS cardno. 13-0259). As can be seen from FIGS. 1a and b, the 2 theta value after iron pillaring is reduced from 6.494 degrees to 5.557 degrees, and the corresponding distance between (001) surface layers is increased from 1.37nm to 1.59nm, which shows that the layered structure of the montmorillonite is damaged to a certain extent, and the hydroxyl iron is successfully embedded between the layers of the montmorillonite, thus the method of the invention can successfully prepare the titanium pillared montmorillonite. In terms of impurity phases, calcite disappeared, while quartz and part of the montmorillonite remained, and no discernible diffraction peak of the iron oxide crystalline phase was found in the initial FPMt.

As shown in fig. 1b, FPMt500 shows diffraction peaks at 2 θ 32.867, 35.270, 40.190, 49.116, 53.693, 61.818 and 63.763 ° (the specific positions are indicated by solid red lines), which are apparently not belonging to montmorillonite, and even some diffraction peaks are gradually revealed after the catalyst is calcined at 200 ℃ (solid lines in fig. 1 c). If the calcination temperature of the iron pillared montmorillonite is increased to 800 ℃, diffraction peaks at the positions are more obvious, and the iron pillared montmorillonite is determined to be hematite by comparing with a standard card. The hematite diffraction peak of FPMt800 coincides with FPMt400 at the 2 θ position described above, so it can be concluded that amorphous iron oxide in iron pillared montmorillonite can gradually transform to hematite mineral phase with increasing calcination temperature.

Experimental example 2 SEM analysis

The titanium pillared montmorillonite composite material in example 1 was subjected to surface topography analysis using a FEI Quanta 250FEG type Scanning Electron Microscope (SEM).

Fig. 2 shows SEM images of iron pillared montmorillonite (FPMt200, FPMt300, FPMt400, FPMt500) fired at 200, 300, 400 and 500 ℃, and it can be observed that the outer surface of iron pillared montmorillonite is gradually broken, dropped, or even disintegrated with increasing firing temperature, and the particles become smaller. Compared to FPMt200, FPMt300 had a rougher surface, but the overall montmorillonite structure was not damaged too much. In addition, ellipsoidal particles were found in the FPMt500 sample (FIG. 2d inset), so it is precisely the high temperature calcination that caused the structural failure of the material, less distribution of hydroxyl iron cations in the center of the layer, and the reduction of the interlayer molecular forces due to the increased interlayer spacing, suggesting that the center of the iron pillared montmorillonite layer is the primary site for fracture during calcination.

The iron pillared montmorillonite element mapping images showed uniform distribution of iron elements (fig. 2e-f), indicating that iron oxide was uniformly distributed on the outer surface of the montmorillonite mineral component or in the interlaminar space. These newly formed hematite minerals contribute greatly to the surface catalytic properties of iron pillared smectites.

Experimental example 3 catalytic reduction Effect of FPMt on o-nitrophenol

The catalytic reduction reaction is all in N₂The reaction is carried out under the atmosphere condition and has no light, and the reaction device is composed of a glass conical flask, a rubber plug, a magnetic stirrer, tinfoil and the like. Before the reaction starts (i.e. before adding ferrous sulfate and 2-NP), high-purity N is used in advance₂Dissolved oxygen in the reaction solution was removed, and aeration was set for about 30 min. The reaction solution contained 0.2mol/L NaCl, 28mmol/L buffer (MES), 22. mu. mol/L2-NP, 3.0mmol/L LFeSO₄And 4.0g/L of a catalyst (titanium pillared montmorillonite composite in examples 1 to 3). Before the 2-NP is added into the reaction system, the Fe (II) pre-adsorption needs to be carried out for 2h to ensure that the Fe (II) reaches the adsorption equilibrium. Once the 2-NP is added to the reaction system, catalytic reduction is carried outIt is started. The reaction temperature for each experiment was controlled at room temperature (about 25 ℃ C.), 1.5mL aliquots of the suspension were taken as test samples at intervals, and the reaction was stopped with 2.0mol/LHCl (20. mu.L).

All liquid samples were filtered using a 0.22 μm PTFE membrane before measuring the 2-NP concentration, and then measured by reverse phase High Performance Liquid Chromatography (HPLC) using a Shimadzu LC-10AT, Shimadzu, Japan, as a column on a Syncrons-C18 reverse phase column (250 mm. times.4.6 mm, 5 μm), and a mobile phase consisting of 80% methanol and 20% ultrapure water (wherein the ultrapure water was acidified with hydrochloric acid and the pH was adjusted to 2.8). The flow rate of the mobile phase is 1mL/min, the column temperature is 25 ℃, the sample injection amount is 20 mu L, and the detection wavelength is 265 nm.

The results of the catalytic reduction conversion experiment on 2-NP with iron pillared montmorillonite systems of different iron contents (example 1 is compared with example 2 and example 3 together with initial FPMt) as shown in FIG. 3a show that the higher the iron content of iron pillared montmorillonite, the faster the reduction conversion rate of 2-NP is, but when the iron content is increased from 10mmol/g to 15mmol/g, the increase of the reduction conversion rate of pollutants is greatly reduced, which indicates that the iron content of the catalyst material is no longer the dominant factor of the catalytic reduction reaction process.

The results of the experimental reduction conversion of 2-NP from iron pillared montmorillonite (example 1) calcined at different temperatures as shown in FIG. 3 b. The results show that the calcination temperature of the iron pillared montmorillonite and the removal rate of the 2-NP do not completely show a single linear relationship, and the initial FPMt, FPMt100 and FPMt200 have little difference on the removal rate of the 2-NP through catalytic reduction. The removal rates of 2-NP reductive conversion of three higher temperature calcined samples, FPMt300, FPMt400, FPMt500, etc., showed a decreasing trend. The FPMt300 sample has the best reduction catalytic performance.

The adsorption capacity of the different iron pillared montmorillonite (example 1) on o-nitrophenol, as shown in fig. 4, was lower for the initial FPMt and FPMt300 than for the other catalysts, but overall, it was substantially maintained at about 20%, and therefore, in addition to the surface adsorption removal, the mechanism of the surface catalytic reduction conversion was the main route for the removal of 2-NP from iron pillared montmorillonite. Of course, adsorption may also accelerate the interfacial reductive transformation of 2-NP.

Experimental example 4 pyridine FTIR Pattern

The fourier transform infrared spectroscopy (FTIR) of the chemisorbed pyridine of the catalyst (the titanium pillared montmorillonite composite of example 1) was determined using a Nicolet 6700 fourier transform infrared spectrometer. The specific method comprises the following steps: 0.1g of catalyst is weighed and placed in a vacuum drying oven at 80 ℃ for 5 hours, then 0.5mL of pyridine is dropped into 0.1g of catalyst and is adsorbed for 2 hours, and finally the catalyst is transferred to an oven at 50 ℃ and is dried for 24 hours to remove part of residual substances after physical adsorption.

The acid sites are mainly derived from the interlamination of polarized water molecules (such as Na) in the montmorillonite⁺、K⁺、Ca²⁺Hydrate of (b), H adsorbed on Al-O octahedron (main site of structural negative charge)₃O⁺And SiOH, whereas the Lewis acid sites originate mainly from octahedral lamellar edge-unsaturated Al³⁺(Mg²⁺And Fe^2+/3+). According to the pyridine adsorption mode, at 1640 and 1540cm^-1The infrared absorption band of (A) corresponds to the acid site of Bpy, and is located at 1450-^-1Has an infrared absorption band belonging to the acid position of Lpy and being close to 1440 and 1590cm^-1Corresponds to the acid position of Hpy and 1490cm^-1The strong absorption band may contain all types of acid sites, i.e., Bpy + Lpy + Hpy.

As shown in fig. 5, the total acid site content of iron pillared montmorillonite gradually decreased as the calcination temperature increased. Of these, Bpy and Hpy both relate to adsorption of water and surface hydroxyl groups, both of which decrease as the calcination temperature increases. The influencing factor of the number of Lewis acid sites is mainly naked unsaturated Al³⁺The amount, the surface area covered by iron oxide or hematite, and the amount of interlayer cations and their migration. As shown in FIG. 5, only the FPMt500 is at 1620cm^-1No Lpy peak was observed, and the Lpy peaks for the remaining catalysts all decreased with increasing calcination temperature. Presumably, the reason is that the crystal growth and covering effect of iron oxide are generated, and at the same time, high temperature is existed to promote interlayer cation penetration into montmorillonite octahedron or migration fixation is catalyzedThe surface of the agent thus forms an oxide. On the other hand, the structure collapse limits the output of interlayer cations, various types of solid acid surface acid sites are distributed on the surface of the clay mineral, and the acid site strengths are different due to different structural forms. In fact, highly reductive catalytically active surface sites need to have a certain capacity to bind Fe (ii) such that the density of the Fe (ii) outer layer electron cloud is greatly increased, e.g. weaker or medium strength acid sites (≡ AlOH, ≡ TiOH and ≡ FeOH etc.) all tend to form Fe (ii) surface complexes, but too strong acid sites (≡ SiOH etc.) do not form Fe (ii) surface complexes easily instead.

The comprehensive embodiment shows that the FPMt300 sample not only keeps relatively complete surface structure appearance of montmorillonite, but also generates hematite with relatively good crystallization, thereby improving the conductivity of the original material, but also keeps a certain amount of surface hydroxyl with certain strength, and further can react with ferrous iron in a water phase to form a Fe (II) surface complex with high reduction activity. It can be seen that optimization of the surface properties of these mineral materials is very beneficial to the catalytic reduction process of 2-NP.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.

Claims

1. The preparation method of the iron pillared montmorillonite composite catalyst is characterized by comprising the following steps of:

2. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein the calcination temperature in step S2 is 300 ℃ and the calcination time is 2 hours.

3. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein in step S1, a montmorillonite suspension having a sodium based montmorillonite content of 2% and an iron pillared agent solution are mixed at a ratio of [ Fe ]/Mt ═ 10mmoL/g to prepare an iron pillared montmorillonite suspension.

4. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein the aging in step S2 is performed by standing at 60 ℃ for not less than 24 hours.

5. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein the grinding in step S2 is to 100 to 200 mesh.

6. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein the centrifugation in step S2 is 4000r/min for 6 min.

7. The method for preparing an iron pillared montmorillonite composite catalyst according to claim 1, wherein the purity of the sodium montmorillonite is 90% or more, and the particle size is 100 to 200 meshes.

8. The iron pillared montmorillonite composite catalyst prepared by the method of any one of claims 1 to 7.

9. The use of the iron pillared montmorillonite composite catalyst of claim 8 for degrading nitroaromatic pollutants.

10. The use of claim 9, wherein the nitroaromatic contaminant comprises, but is not limited to, o-nitrophenol.