A montmorillonite loaded sulfidized zero-valent iron composite material, a preparation method and application thereof

Abstract

The application discloses a montmorillonite loaded sulfidized zero-valent iron composite material and a preparation method and application thereof, and the preparation method comprises the following steps: step 1, dissolving ferrous sulfate heptahydrate and montmorillonite in deionized water to generate a first mixed solution; step 2, stirring the first mixed solution under the protection of a protective gas; step 3, under the protection of a protective gas, dropping a sulfidizing agent and an aqueous solution of sodium borohydride into the first mixed solution, and fully reacting to obtain a second mixed solution; step 4, performing solid-liquid separation on the second mixed solution; and step 5, washing the separated solid with anhydrous ethanol and anaerobic deionized water in sequence, and then obtaining (S-nZVI@MMT) through vacuum freeze drying. When Na2S·9H2O, Na2S2O3 and Na2SO3 are used as the sulfidizing agent, and the S / Fe molar ratio is 0.01, 0.01 and 0.02 respectively, the S-nZVI@MMT can simultaneously reduce Cr(VI) and NO3 ‑ -N is Cr(III) and NH4 + -N; when the S / Fe molar ratio is 0.2, 0.2 and 0.1 respectively, the S-nZVI@MMT can selectively reduce Cr(VI) into Cr(III), effectively inhibits the reduction of NO3 ‑ -N.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water pollution remediation, in particular to a montmorillonite loaded sulfidized zero-valent iron composite material and a preparation method and application thereof. BACKGROUND

[0002] Hexavalent chromium (Cr(VI)) and nitrate (NO3 - -) are ubiquitous in various industrial wastewater and waste residues as byproducts of electroplating, tanning, mining, etc. The long-term stacking and unreasonable discharge of these byproducts inevitably cause soil, groundwater and surface water pollution, which has adverse effects on human health and the ecological environment, and may inhibit the treatment efficiency of biological denitrification in wastewater treatment plants due to the biological toxicity of Cr(VI). Therefore, how to effectively remove coexisting Cr(VI) and NO3 - - in different environments is of great concern.

[0003] Physical adsorption and chemical reduction precipitation are common methods for removing Cr(VI), and more and more recent studies have proposed that NO3 - - can be reduced to NH4 + - by chemical reduction, which is an ideal alternative to traditional NH3 synthesis. Therefore, simultaneous chemical reduction of NO3 - - and Cr(VI) to NH4 + - and Cr(III) can not only remove pollutants in wastewater, but also effectively recover nitrogen resources. However, in groundwater or biological denitrification facilities in wastewater treatment plants, the most ideal way to convert NO3 - - to non-toxic and harmless N2 is through microbial denitrification, while NH4 + - is considered as a process byproduct that affects effluent water quality. Therefore, effectively removing Cr(VI) in water bodies, reducing its biological toxicity, and not affecting the microbial conversion process of NO3 - - is an effective method to solve the problem of coexisting Cr(VI) and NO3 - - in groundwater and wastewater treatment plants. Therefore, it is crucial to find a suitable method to solve the problem of coexisting Cr(VI) and NO3 - - in different application scenarios. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a montmorillonite loaded sulfidized zero-valent iron composite material in view of the technical defects in the prior art.

[0005] Another purpose of the present application is to provide a montmorillonite loaded sulfidized zero-valent iron composite material obtained based on the preparation method, which can achieve the removal of Cr(VI) and NO3 -- selective reduction of N.

[0006] Another object of the present application is to provide the application of the said montmorillonite loaded sulfidized zero-valent iron composite material in sewage treatment.

[0007] The technical scheme adopted to achieve the object of the present application is as follows:

[0008] A preparation method of a montmorillonite loaded sulfidized zero-valent iron composite material, comprising the following steps:

[0009] Step 1, dissolving ferrous sulfate heptahydrate and montmorillonite in deionized water to generate a first mixed solution;

[0010] Step 2, under the protection of a protective gas, stirring the first mixed solution for sufficient adsorption;

[0011] Step 3, under the protection of a protective gas, adding a sulfidizing agent and an aqueous solution of sodium borohydride dropwise to the first mixed solution, and fully reacting to obtain a second mixed solution;

[0012] Step 4, performing solid-liquid separation on the second mixed solution;

[0013] Step 5, washing the separated solid with anhydrous ethanol and anaerobic deionized water in sequence, and then vacuum freeze-drying to obtain a montmorillonite loaded sulfidized zero-valent iron composite material (S-nZVI@MMT).

[0014] In the above technical scheme, the mass ratio of montmorillonite to Fe in ferrous sulfate heptahydrate in step 1 is 0.4-0.8, and the mass ratio of sodium borohydride to the mass of ferrous sulfate heptahydrate in step 1 in step 3 is 0.54-0.68.

[0015] In the above technical scheme, the sulfidizing agent in step 2 is sodium sulfide nonahydrate (Na2S·9H2O), sodium thiosulfate (Na2S2O3), or anhydrous sodium sulfite (Na2SO3).

[0016] In the above technical scheme, the molar ratio of S to Fe (S / Fe) in the sulfidizing agent in step 3 to the molar amount of Fe in ferrous sulfate heptahydrate in step 1 is 0.01-0.2, preferably, the S / Fe is 0.1-0.2, or the S / Fe is 0.01-0.05, and further, the S / Fe is 0.01-0.02.

[0017] In the above technical scheme, the dropwise addition speed in step 3 is 6-7 mL / min, and the reaction time is 20-40 minutes.

[0018] Another aspect of the present application also includes the montmorillonite loaded sulfidized zero-valent iron composite material obtained by the preparation method.

[0019] Another aspect of the present application also includes the application of the montmorillonite supported sulfidized zero-valent iron composite material in treating Cr(VI) in wastewater, wherein the ratio of the molar amount of S in the sulfidizing agent to the molar amount of Fe in the ferrous sulfate heptahydrate in step 1, i.e., S / Fe, is 0.01-0.05, preferably, the sulfidizing agent is Na2S, and S / Fe is 0.01.

[0020] In the above technical solution, the pH of the wastewater is 3-9, the concentration of NO3 - -N in the wastewater is 0-50 mg / L.

[0021] Another aspect of the present application also includes the application of the montmorillonite supported sulfidized zero-valent iron composite material in simultaneously treating Cr(VI) and NO3 - -N in wastewater, wherein the ratio of the molar amount of S in the sulfidizing agent to the molar amount of Fe in the ferrous sulfate heptahydrate in step 1, i.e., S / Fe, is 0.01-0.02, preferably, the sulfide is not Na2S2O3, when the sulfidizing agent is Na2S, S / Fe is preferably 0.01, and when the sulfidizing agent is Na2SO3, S / Fe is preferably 0.02.

[0022] In the above technical solution, the pH of the wastewater is 3-9, the concentration of NO3 - -N in the wastewater is 0-50 mg / L.

[0023] Another aspect of the present application also includes the application of the montmorillonite supported sulfidized zero-valent iron composite material in selectively removing Cr(VI) in wastewater and inhibiting the reduction of NO3 - -N, wherein the ratio of the molar amount of S in the sulfidizing agent to the molar amount of Fe in the ferrous sulfate heptahydrate in step 1, i.e., S / Fe, is greater than or equal to 0.1 and less than or equal to 0.2, when the sulfidizing agent is Na2S, S / Fe is 0.2, when the sulfidizing agent is Na2SO3, S / Fe is 0.1, and when the sulfidizing agent is Na2S2O3, S / Fe is 0.2.

[0024] In the above technical solution, the pH of the wastewater is 3-9, the concentration of NO3 - -N in the wastewater is 0-50 mg / L.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. When Na2S·9H2O, Na2S2O3 and Na2SO3 are used as the sulfidizing agent, and the molar ratio of S / Fe is 0.01, 0.01 and 0.02 respectively, S-nZVI@MMT can simultaneously reduce Cr(VI) and NO3- -N is Cr(III) and NH4 + -N, when Na2S·9H2O and Na2SO3 are selected as sulfidation agents, the performance is better than that of Na2S2O3; when the molar ratio of S / Fe is 0.2, 0.2 and 0.1 respectively, S-nZVI@MMT can selectively reduce Cr(VI) to Cr(III), effectively inhibit NO3 - -N reduction, selective removal of Cr(VI) can not only reduce the toxicity inhibition of Cr(VI) on denitrification, but also promote NO3 - -N biological transformation process, and by inhibiting NO3 - -N reduction avoids interference with NO3 - -N biological transformation process, thereby promoting Cr(VI) and NO3 - -N effective removal;

[0027] 2. When Na2S·9H2O and Na2SO3 are used as sulfidation agents, S-nZVI@MMT can simultaneously reduce Cr(VI) and NO3 - -N, the simultaneous reduction efficiency of Cr(VI) and NO3 - -N reduction to NH4 + -N conversion rate is relatively high, which is 94% and 95% respectively;

[0028] 3. S-nZVI@MMT selectively reduces Cr(VI) and is not affected by solution pH (3-9) and NO3 - -N concentration (0, 5, 10, 30 and 50 mg / L);

[0029] 4. The present application discloses that Fe(II) and S 0 In the process of Cr(VI) and NO3 - -N reduction;

[0030] 5. When the molar ratio of S / Fe is 0.02, Fe(II) mainly participates in the generation of S-nZVI@MMT surface Fe3O4 in the reaction process; when the molar ratio of S / Fe is 0.1, Fe(II) and S 0 mainly participate in the transformation of S-nZVI@MMT surface amorphous Fe3O4, FeS and FeS2 in the reaction process;

[0031] 6. S-nZVI@MMT can simultaneously reduce Cr(VI) and NO3 -When N coexists, the conversion ratio of Cr(III) is 83.65%, mainly in the form of amorphous chromium(III) hydroxide and chromite; when S-nZVI@MMT selectively reduces Cr(VI), the conversion ratio of Cr(III) is 94.2%, mainly in the form of amorphous chromium(III) hydroxide and chromium oxide(III). BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The preparation method flowchart of S-nZVI@MMT is shown in the figure.

[0033] Figure 2 The scanning electron microscope image (SEM) of S-nZVI@MMT is shown in the figure.

[0034] Figure 3 The X-ray diffractometer spectrum (XRD) of S-nZVI@MMT is shown in the figure.

[0035] Figure 4 The removal of Cr(VI) and NO3 - The flowchart of the removal of N coexisting pollution is shown in the figure.

[0036] Figure 5 The removal of Cr(VI) and NO3 - The removal of N coexisting pollution is shown in the figure.

[0037] Figure 6 The simultaneous reduction of NO3 - The ratio of N species is shown in the figure.

[0038] Figure 7 The initial NO3 - The removal of Cr(VI) by S-nZVI@MMT is shown in the figure.

[0039] Figure 8 The removal of Cr(VI) by S-nZVI@MMT is shown in the figure.

[0040] Figure 9 The X-ray diffractometer spectrum (XRD) of S-nZVI@MMT is shown in the figure.

[0041] Figure 10 The X-ray photoelectron spectrogram (XPS) of the surface Fe 2p3 / 2 and S2p3 / 2 of S-nZVI@MMT is shown in the figure.

[0042] Figure 11 The X-ray photoelectron spectrogram (XPS) of the surface Cr 2p3 / 2 of S-nZVI@MMT is shown in the figure. DETAILED DESCRIPTION

[0043] The application will be described in further detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are intended to be illustrative only and are not intended to limit the present application.

[0044] Example 1

[0045] A preparation method of a montmorillonite loaded sulfidized zero-valent iron composite material, comprising the following steps:

[0046] Step 1: 2.085 g of ferrous sulfate heptahydrate and 0.168 g of montmorillonite are added to a serum bottle containing 100 mL of deionized water to dissolve, to generate a first mixed solution, wherein the mass ratio of MMT to Fe is 0.4;

[0047] Step 2: After nitrogen is introduced for 10 min, the serum bottle is sealed, and magnetic stirring is performed for 5 hours;

[0048] Step 3: 100 mL of a mixed solution containing different sulfidizing agents and sodium borohydride is added dropwise to the first mixed solution at a rate of 6-7 mL / min for chemical reaction for 30 min to generate a second mixed solution, and nitrogen is introduced during the reaction process, wherein the sulfidizing agent includes Na2S·9H2O, Na2S2O3 and Na2SO3, the molar ratio of S to Fe is 0-0.2, and the amount of NaBH4 is 0.375 mol / L;

[0049] Step 4: The second mixed solution is subjected to solid-liquid separation by vacuum filtration to obtain a solid;

[0050] Step 5: The solid obtained in step 4 is washed with anhydrous ethanol and anaerobic deionized water, and then vacuum freeze-dried to obtain the target S-nZVI@MMT.

[0051] The montmorillonite loaded sulfidized nano zero-valent iron (S-nZVI@MMT) takes montmorillonite (MMT) as a support, and by regulating the types of sulfidizing agents and the molar ratio of S to Fe, S-nZVI@MMT with different reaction characteristics and chemical properties is prepared; the preparation method has mild reaction conditions and simple preparation process, and has good selective removal effect on Cr(VI) and NO3 - -N coexisting pollutants in different application scenarios, and has good application prospects in the fields of resource recycling and water body remediation.

[0052] Example 2

[0053] In this embodiment, based on example 1, Na2SO3 is selected as the sulfidizing agent in step 3, and the molar ratio of S in Na2SO3 to the molar amount of Fe in the ferrous sulfate heptahydrate in step 1 is set to 0, 0.01, 0.02, 0.05, 0.1 and 0.2 in step 3, respectively, and is denoted as S-nZVI@MMT-0, S-nZVI@MMT-0.01, S-nZVI@MMT-0.02, S-nZVI@MMT-0.05, S-nZVI@MMT-0.1 and S-nZVI@MMT-0.2.

[0054] Different Scanning electron microscope (SEM) images of S-nZVI@MMT synthesized at the specified molar ratio are shown below. Figure 2 As shown, a large number of glossy nano-zero-valent iron (nZVI) particles with an average size of 100 nm are uniformly dispersed on the surface and between the layers of montmorillonite (MMT). Figure 2 (A) effectively avoids Fe 0 Reunion.

[0055] along with With increasing molar ratio, the sheet-like thin film structure (a mixture of iron sulfides, including FeS, FeS2, polysulfides, and elemental S) coating the S-nZVI@MMT surface gradually increases in size and thickness until it completely covers the S-nZVI@MMT surface. EDS spectra show that the mass percentage (wt%) of S and Fe in S-nZVI@MMT increases with increasing molar ratio. The molar ratios increased from 0% and 26.1% to 3.1% and 82.9%, respectively, and the S / Fe mass ratio in S-nZVI@MMT also increased from 0.006 to 0.04. This indicates that the iron sulfides on the surface of S-nZVI@MMT may undergo species transformation with increasing S / Fe molar ratio.

[0056] Example 3

[0057] Based on Example 1, in step 3, Na2SO3, Na2S, and Na2S2O3 were selected as sulfiding agents to synthesize S-nZVI@MMT under different S / Fe molar ratios (the ratio of the molar amount of S in the sulfiding agent in step 3 to the molar amount of Fe in ferrous sulfate heptahydrate in step 1). The X-ray diffraction (XRD) patterns are shown below. Figure 3 As shown, regardless of the vulcanizing agent chosen, when the S / Fe molar ratio is low (<0.1), the main component of S-nZVI@MMT is Fe. 0 And Fe3O4; when the S / Fe molar ratio is greater than 0.1, the diffraction peak of Fe3O4 in S-nZVI@MMT disappears, Fe 0 The crystallinity of the peaks is significantly enhanced. Compared to when the S / Fe molar ratio is 0, sulfidation weakens the peaks of other iron oxides and slows down the Fe... 0 Oxidation. Changes in the type of sulfiding agent and the S / Fe molar ratio also caused a significant shift in the Fe(110) peak. Figure 3 The presence of C indicates the formation of iron sulfides in S-nZVI@MMT. However, no obvious iron sulfide peaks were observed on the surface of S-nZVI@MMT, suggesting that the formed iron sulfides may be in an amorphous state.

[0058] Example 4

[0059] As Figure 4 shown, the S-nZVI@MMT was used to treat wastewater containing Cr(VI) and NO3 - -N, including the following steps:

[0060] Step 1: The target montmorillonite loaded sulfurized nano zero-valent iron (S-nZVI@MMT) was prepared according to the preparation method of the embodiment.

[0061] Step 2: 100 mL of mixed solution containing Cr(VI) and NO3 - -N was added to the anaerobic serum bottle according to the preset reaction conditions, and the preset reaction conditions were different initial pH (3, 5, 7, 9) and different initial NO3 - -N concentration (0, 5, 10, 30, 50 mg / L), and the Cr(VI) concentration in the mixed solution was 30 mg / L; wherein a Cr(VI) solution mother liquor with an initial concentration of 1 g / L was prepared by using potassium dichromate, and the mother liquor was diluted to 30 mg / L before the experiment for use.

[0062] Step 3: After deoxygenating the mixed solution in the anaerobic serum bottle with nitrogen for 5 min, 1 g / L of S-nZVI@MMT prepared with different sulfurizing agents and S / Fe molar ratios was added, and then the bottle was sealed to maintain an anaerobic reaction state. The anaerobic serum bottle was placed in a constant temperature shaker for full reaction, with a rotation speed of 150 rpm and a temperature of 25°C. At intervals, an appropriate amount of solution was taken out with a syringe and filtered through a 0.45 μm filter membrane. The Cr(VI) concentration was determined by the diphenyl carbazide spectrophotometric method, the total chromium concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS), the NH4 + -N concentration was determined by the Nash reagent spectrophotometric method, and the NO3 - -N and NO2 - -N concentrations were determined by ion chromatography (IC). Without special requirements, the initial pH of the solution was adjusted to 7 with 0.1 M HC1 or NaOH. In the effect test of Cr(VI) and NO3 - -N coexisting pollution removal in water, S-nZVI@MMT prepared with different sulfurizing agents and S / Fe molar ratios was used to study the influence on the selective removal performance of Cr(VI) and NO3 - -N.

[0063] The removal of Cr(VI) and NO3 - -N in aqueous solution by S-nZVI@MMT synthesized with different sulfurizing agents and S / Fe molar ratios was plotted as a function of time, as shown in Figure 5 When S / Fe was 0.01 and 0.05, The highest removal rate of Cr(VI) was achieved, reaching 99.8% after 6.5 hours of reaction, which is higher than that of unsulfurized materials (S / Fe = 0, 88.6%). Figure 5 (A). When S / Fe is 0.01, Also showing an affinity for NO3 - -N has the highest reduction efficiency (87%), which is higher than that of uncured materials (66.1%). Figure 5 (B). With increasing S / Fe molar ratio, Cr(VI) and NO3... - The removal efficiency of -N gradually decreases. When the S / Fe ratio is 0.2, although the removal efficiency of Cr(VI) decreases, Completely inhibited NO3 - The reduction of -N achieves selective removal of Cr(VI).

[0064] When S / Fe is 0.02, For Cr(VI) and NO3 - -N removal efficiency was the highest, at 98.8% and 74.4%, respectively. Figure 5 (C and D). When S / Fe is 0.1, it not only effectively inhibits NO3 - The reduction of -N also exhibited a high selective removal efficiency (93.5%) for Cr(VI). Compared to sulfiding agents Na2S·9H2O and Na2SO3, Na2S2O3, when used as a sulfiding agent, simultaneously removed NO3- at low S / Fe ratios (S / Fe = 0.01). - -N is less efficient ( Figure 5 (E and F), however, when S / Fe is 0.2, The selective removal efficiency for Cr(VI) is high (99.3%). Therefore, by adjusting the type of vulcanizing agent and the S / Fe molar ratio, S-nZVI@MMT can achieve high selective removal efficiency for Cr(VI) and NO3. - -N has high simultaneous removal efficiency and selective removal of Cr(VI).

[0065] S-nZVI@MMT Synchronous Restoration NO3 - -N represents the proportion of different N species. As shown in the figure, in the optimal NO3... - Under S / Fe conditions of -N reduction (0.01 and 0.02), and Restore NO3 - -N is NH4 + The conversion rates of -N were high, at 94% and 95%, respectively. Therefore, S-nZVI@MMT simultaneously reduced Cr(VI) and NO3. - Effective nitrogen resource recovery can also be achieved when -N is present.

[0066] Initial NO3 - The effect of -N concentration on the removal of Cr(VI) by S-nZVI@MMT over time is shown in the curve. Figure 7 As shown, with the initial NO3 in the solution - With increasing N-N concentration, the removal efficiency of Cr(VI) by unsulfurized materials (S / Fe = 0) significantly decreases. Figure 7 (G). Regardless of the type of vulcanizing agent, under low S / Fe and high S / Fe conditions, NO3... - The increase in -N concentration did not significantly affect the removal efficiency of Cr(VI) by S-nZVI@MMT.

[0067] The effect of initial solution pH on the selective removal of Cr(VI) by S-nZVI@MMT over time is shown in the curve. Figure 8 As shown, under high S / Fe conditions, S-nZVI@MMT prepared with different sulfiding agents exhibited high selective removal efficiency for Cr(VI) at pH 3. This efficiency decreased slightly as pH increased to 7, but did not decrease further when pH continued to rise from 7 to 9. Furthermore, S-nZVI@MMT showed almost no interaction with NO3- in the pH range of 3–9. - -N reaction. Therefore, S-nZVI@MMT can achieve selective removal of Cr(VI) within a relatively wide pH range (3-9).

[0068] The X-ray diffraction (XRD) spectrum of S-nZVI@MMT after the reaction is shown below. Figure 9 As shown, similar to the uncured material (S / Fe = 0), it was synthesized at a low S / Fe (0.02) ratio. Fe after the reaction 0 The disappearance of diffraction peaks and the enhancement of Fe3O4 crystallization peaks indicate that Fe 0 Simultaneous removal of NO3 - -N and Cr(VI) play a crucial role. Synthesis under high S / Fe (0.1) conditions... Fe after the reaction 0 The diffraction peaks remained clear, and no crystalline peaks for iron oxide and iron sulfide were observed. Therefore, except for Fe... 0 In addition, other important iron species are involved in the selective removal of Cr(VI).

[0069] X-ray photoelectron spectroscopy (XPS) spectra of Fe 2p3 / 2 and S 2p3 / 2 on the S-nZVI@MMT surface before and after the reaction are shown below. Figure 10 As shown, before the reaction (S / Fe = 0.02) Surface except for Fe 0 In addition to Fe3O4, there are also small amounts of FeS and FeS2 peaks. Figure 10(A and E in the middle), Fe after the reaction 0 The FeS and FeS2 peaks disappeared, while the Fe(II) and Fe3O4 peaks increased. Figure 10 The results (D) are consistent with the XRD results. Fe(II) mainly participates in the formation of highly conductive Fe3O4 during the reaction, thereby promoting the reaction. Fe 0 Corrosion and electron transfer to achieve NO3 - -N and Cr(VI) have high simultaneous removal efficiency. (S / Fe = 0.1) A high proportion of Fe(II) (46.76%) was observed on the surface. Figure 10 In reaction B), Fe(II) is mainly converted into amorphous phases Fe3O4 and FeS. x ( Figure 10 In C), the main morphology of surface S is S. 0 (43.01%) Figure 10 (F in the middle). After the reaction, FeS2, FeS and SO4... 2- The proportion increased significantly, S 0 Decrease (7.75%) Figure 10 (G). During the reaction process, S 0 with Fe 0 The reaction continuously generates amorphous phases FeS and FeS2, which then react with Cr(VI) to form SO4. 2- Meanwhile, S 0 and the generated FeS x Effectively inhibit NO3 - The adsorption and reduction of -N achieve selective removal of Cr(VI).

[0070] The X-ray photoelectron spectrum (XPS) of Cr 2p3 / 2 on the S-nZVI@MMT surface after the reaction is shown below. Figure 11 As shown, after the reaction (S / Fe = 0.02) The surface Cr(III) content is approximately 83.65%, mainly consisting of Cr(III) hydroxide (43.49%) and FeCr2O4 (34.89%). Figure 11 (A and B); Cr(VI) still accounts for 16.35%, which is attributed to the adsorption of Cr(VI) by Fe3O4 generated during the reaction. According to XRD results ( Figure 9 After the reaction (S / Fe = 0.1) No obvious chromium compound crystallization peaks were detected, indicating that the Cr precipitate exists in an amorphous phase after the reaction. Figure 11 From C and D, we can know that The proportion of surface Cr(III) rose to 94.26% in S-nZVI@MMT (S / Fe = 0.1), mainly in the form of amorphous Cr(III) hydroxide (61.94%) and Cr(III) oxide (20.53%). It can be seen that the different Fe and S species formed on the surface of S-nZVI@MMT determine the different reaction paths of Cr(VI).

[0071] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and refinements can also be made, which should be considered as the protection scope of the present application.

Claims

1. A montmorillonite-supported zero-valent iron sulfide composite material for treating Cr(VI) and NO3 in wastewater. − The application of -N is characterized by, The preparation method of the montmorillonite-supported zero-valent iron sulfide composite material includes the following steps: Step 1: Add ferrous sulfate heptahydrate and montmorillonite to deionized water to dissolve them and generate the first mixed solution; Step 2: Under the protection of a protective gas, the first mixed solution is stirred to achieve full adsorption; Step 3: Under the protection of a protective gas, an aqueous solution of the sulfiding agent and sodium borohydride is added dropwise to the first mixed solution and allowed to react fully to obtain a second mixed solution; the sulfiding agent is Na2S2O3, sodium sulfide nonahydrate, or anhydrous sodium sulfite. Step 4: Perform solid-liquid separation on the second mixed solution; Step 5: The separated solids were washed successively with anhydrous ethanol and oxygen-free deionized water, and then the montmorillonite-supported sulfidated zero-valent iron composite material was obtained by vacuum freeze drying. When the sulfiding agent is Na2S and the molar ratio of S / Fe is 0.01, or when the sulfiding agent is Na2SO3 and the molar ratio of S / Fe is 0.02, the montmorillonite-supported sulfidated zero-valent iron composite material simultaneously treats Cr(VI) and NO3 in wastewater. - -N; When the sulfiding agent is Na2S and the molar ratio of S / Fe is 0.2, or when the sulfiding agent is Na2SO3 and the molar ratio of S / Fe is 0.1, or when the sulfiding agent is Na2S2O3 and the molar ratio of S / Fe is 0.2, the montmorillonite-supported sulfidated zero-valent iron composite material selectively removes Cr(VI) from wastewater and inhibits the effect of NO3- on NO3-. - -N restoration.

2. The application as described in claim 1, characterized in that, In step 1, the mass ratio of Fe in montmorillonite and ferrous sulfate heptahydrate is 0.4~0.8, and in step 3, the mass ratio of sodium borohydride to ferrous sulfate heptahydrate in step 1 is 0.54~0.

68.

3. The application as described in claim 1, characterized in that, The dropping rate in step 3 is 6-7 mL / min, and the reaction time is 20-40 minutes.

4. The application as described in claim 1, characterized in that, The pH of the wastewater is 3-9, and the NO3 in the wastewater... − The concentration of -N is 5~50 mg / L.

Images