CN113461059A

CN113461059A - Molybdenum sulfide layered double-metal hydroxide complex and preparation method and application thereof

Info

Publication number: CN113461059A
Application number: CN202110872670.2A
Authority: CN
Inventors: 马淑兰; 袁萌伟; 姚惠琴; 楚梦琳; 杨利肖
Original assignee: Beijing Normal University; Ningxia Medical University
Current assignee: Beijing Normal University; Ningxia Medical University
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2021-10-01

Abstract

The application provides a molybdenum sulfide layered double-metal hydroxide complex and a preparation method and application thereof,wherein, in the molybdenum sulfide layered double hydroxide complex, molybdenum sulfide anion cluster Mo₃S₁₃ ^2‑The interlayer of the magnesium-aluminum layered double hydroxide is inserted, and the magnesium-aluminum layered double hydroxide layer plate pair anion cluster Mo₃S₁₃ ^2‑Has good dispersibility, and Mo between layers₃S₁₃ ^2‑The Mo and S adsorption sites are fully exposed, and the adsorption to Ag is improved⁺The capture capacity and the adsorption capacity of the catalyst can reach 1073 mg/g. More importantly, MgAl-Mo₃S₁₃LDH can react Ag with⁺Reducing the silver into metal Ag, thereby obtaining the simple substance silver nanobelt.

Description

Molybdenum sulfide layered double-metal hydroxide complex and preparation method and application thereof

Technical Field

The application relates to the technical field of layered double hydroxide complexes, in particular to a molybdenum sulfide layered double hydroxide complex and a preparation method and application thereof.

Background

Silver is a precious metal and has important applications in modern electronics, medicine and chemical catalysis. The list of nanotechnology consumer products from the woodwilson institute (2016) lists 350 various manufacturer-identified products containing silver nanoparticles, fully accounting for the important requirements of Ag. However, the precious metal silver is usually extracted from low-grade silver ores and is accompanied by various other metal impurities such as zinc, lead and copper, so that the extraction of the silver has certain difficulty.

Although numerous materials, such as zeolites, activated carbons, polymers, biomaterials, and adsorption resins, have been developed to capture heavy metal ions, the requirement of silver extraction cannot be satisfied, and there is a need to find a material for extracting noble metal silver with high selectivity at low cost.

Disclosure of Invention

The purpose of the present application is to provide a molybdenum sulfide layered double hydroxide composite (MgAl-Mo)₃S₁₃LDH) to at least achieve efficient capture of silver ions.

In a first aspect, the present application provides a layered double hydroxide complex of molybdenum sulfide, wherein the molybdenum sulfide anion cluster Mo₃S₁₃ ^2-Intercalated between layers of the layered double hydroxide of magnesium aluminum.

In a second aspect, the present application provides a method for preparing a molybdenum sulfide layered double hydroxide complex of the first aspect of the present application, comprising:

will be (NH)₄)₂Mo₃S₁₃·H₂Dissolving O in N, N' -dimethylformamide or dimethyl sulfoxide to obtain MgAl-NO₃And (3) putting LDH into the reaction kettle, standing the reaction kettle for 20 to 30 hours in an air-isolated environment, filtering and washing the reaction kettle to obtain the molybdenum sulfide layered double hydroxide complex precipitate.

In a third aspect, the present application provides the use of the molybdenum sulfide layered double hydroxide complex of the first aspect of the present application for adsorbing Ag⁺The use of (1).

In a fourth aspect of the present application there is provided the use of the molybdenum sulphide layered double hydroxide complex of the first aspect of the present application for extracting metallic silver.

In a fifth aspect, the present application provides the use of the molybdenum sulfide layered double hydroxide composite of the first aspect of the present application for the preparation of elemental silver nanobelts.

In a sixth aspect, the present application provides a silver ion-adsorbing material comprising the molybdenum sulfide layered double hydroxide complex provided in the first aspect of the present application.

The molybdenum sulfide layered double hydroxide complex provided by the application has the advantages that the magnesium-aluminum layered double hydroxide laminate has good dispersing capacity, so that Mo positioned between layers₃S₁₃ ^2-The Mo and S adsorption sites are fully exposed, and the adsorption to Ag is improved⁺The capture capacity and the adsorption capacity of the catalyst can reach 1073 mg/g. More importantly, MgAl-Mo₃S₁₃LDH can be formed by precipitation and reduction of Ag⁺Generating a simple substance of metal Ag, and further obtaining the simple substance silver nanobelt.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only one embodiment of the present application, and other embodiments can be obtained by those skilled in the art according to the drawings.

FIG. 1 is (NH)₄)₂Mo₃S₁₃、MgAl-NO₃LDH and MgAl-Mo₃S₁₃-infrared absorption spectrum of LDH.

FIG. 2 shows MgAl-Mo₃S₁₃-LDH、MgAl-NO₃-LDH and (NH)₄)₂Mo₃S₁₃XRD pattern of (a).

FIG. 3 shows MgAl-Mo₃S₁₃SEM pictures of solid samples before and after adsorption of 400ppm silver ions by LDH.

FIG. 4 shows Mo₃S₁₃-LDH vs Ag⁺The Langmuir adsorption isotherm model of (a) wherein the plot is q_eAnd C_eThe relationship curve of (1); (b) the figure is Ce/q_eAnd C_eThe relationship of (1).

FIG. 5 shows Mo₃S₁₃-LDH vs Ag⁺Wherein graph (a) is a concentration-time curve; (b) the graph is a removal rate-time curve; (c) the figure is an adsorption quantity-time curve; (d) the figure is a fitted curve of pseudo-secondary kinetics.

FIG. 6 shows MgAl-Mo₃S₁₃-LDH vs Ag⁺、Cu²⁺The selective adsorption result of (a), wherein the graph (a) shows different Cu²⁺/Ag⁺Molar ratio of Cu²⁺、Ag⁺Histogram of removal rate; (b) the graph shows the separation factor SF (Ag/Cu), i.e., K_d(Ag)/K_d(Cu) ratio with Cu²⁺/Ag⁺Change curve of molar ratio.

FIG. 7 (A) is a drawing of MgAl-Mo₃S₁₃LDH adsorbing different concentrations of Ag⁺XRD spectrum of the solid sample; (B) the figure is 1000ppm Ag⁺Slow-scanning XRD (X-ray diffraction) spectrum of adsorbed solid sample, Ag and Ag₂And (4) a standard spectrogram of S.

FIG. 8 shows MgAl-Mo₃S₁₃Photographs of the objects and SEM photographs of elementary silver produced after adsorption of LDH.

FIG. 9 shows MgAl-Mo₃S₁₃XPS spectra of the solid matter after adsorption of 800ppm (panel a-panel a ") and 1300ppm (panel b-panel b") of silver by LDH (c) panel showing Ag in solution after adsorption⁺The decrease in concentration with time and the increase in Mo, S concentration with time; (d) the graph shows the change of the molar ratio of the amount of reduction of Ag to the amount of increase of S (Δ Ag/Δ S) in the solution with time during adsorption

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by referring to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in this application are within the scope of protection of this application.

In a first aspect, the present application provides a molybdenum sulfide layered double hydroxide composite (MgAl — Mo)₃S₁₃LDH), in which the molybdenum sulfide anion cluster Mo₃S₁₃ ^2-Intercalated between layers of the layered double hydroxide of magnesium aluminum.

In certain embodiments of the first aspect of the present application, the molybdenum sulfide layered double hydroxide complex has the following chemical composition formula: mg (magnesium)_0.64Al_0.34(OH)₂(Mo₃S₁₃)_x(NO₃)_y·mH₂O, wherein x is 0.05 to 0.10, y is 0.10 to 0.24, and m is 0.5 to 1.2.

In certain embodiments of the first aspect of the present application, the molybdenum sulfide layered double hydroxide complexes have a hexagonal morphology.

will be (NH)₄)₂Mo₃S₁₃·H₂Dissolving O in N, N' -Dimethylformamide (DMF) or dimethyl sulfoxide (DMSO), and adding magnesium aluminum nitrate type layered double hydroxide (MgAl-NO)₃LDH), standing and reacting for 20-30 hours in an air-isolated environment, filtering and washing to obtain the molybdenum sulfide layered double hydroxide complex precipitate. In this process, Mo₃S₁₃ ^2-By reaction with MgAl-NO₃-NO between LDH layers₃ ^-Ion exchange occurs to intercalate the layers of the layered double hydroxide of magnesium aluminum.

In this application, molybdenum sulfide stratiform bimetal hydroxide complex can go on under normal atmospheric temperature and pressure, for avoiding the carbon dioxide in the air to get into reaction system, generates magnalium carbonate stratiform double hydroxide, therefore the synthetic process of molybdenum sulfide stratiform bimetal hydroxide complex of this application need go on under the environment of isolated air.

In some embodiments of the second aspect of the present application, the washing comprises washing the solid with N, N' -dimethylformamide or dimethylsulfoxide until the filtrate is colorless, followed by washing with acetone.

In some embodiments of the second aspect of the present application, (NH)₄)₂Mo₃S₁₃·H₂The mass-volume ratio of O to N, N' -dimethylformamide or dimethyl sulfoxide is 0.3-0.5 mg/ml.

In some embodiments of the second aspect of the present application, the (NH)₄)₂Mo₃S₁₃·H₂O and MgAl-NO₃The mass ratio of-LDH is 1: 0.7-1: 1.

This application is on (NH)₄)₂Mo₃S₁₃·H₂The source of O is not limited, and it can be obtained commercially or by an existing synthetic method, for example, by using (NH)₄)₆Mo₇O₂₄.4H₂O、(NH₄OH). HCl and (NH)₄)₂S_xAnd (4) reaction.

The application is to MgAl-NO₃The source of LDH is not restricted and can be obtained commercially or by existing synthetic methods, for example by homogeneous precipitation, by Mg (NO)₃)₂·6H₂O、Al(NO₃)₃·9H₂Obtaining MgAl-CO by uniform precipitation reaction of O₃-LDH; then MgAl-NO is synthesized by an ion exchange method₃-LDH。

A third aspect of the present application provides the use of the molybdenum sulfide layered double hydroxide complex of the first aspect of the present application for adsorbing Ag⁺The use of (1). MgAl-Mo of the present application₃S₁₃-LDH vs Ag⁺The maximum adsorption capacity can reach 1073mg/g, K_dA value of about 1.4X 10⁷mL/g, which indicates MgAl-Mo of the present application₃S₁₃-LDH vs Ag⁺Has excellent selective adsorption capacity.

In a fourth aspect of the present application there is provided the use of the molybdenum sulphide layered double hydroxide complex of the first aspect of the present application for extracting metallic silver. The inventors have unexpectedly found in their research that MgAl-Mo of the present application₃S₁₃The LDH can generate elementary silver in the system after adsorbing silver ions, so that the LDH can be used for extracting metallic silver.

In a fifth aspect, the present application provides the use of the molybdenum sulfide layered double hydroxide composite of the first aspect of the present application for the preparation of elemental silver nanobelts. The inventors have unexpectedly found in their research that MgAl-Mo of the present application₃S₁₃When the LDH adsorbs silver ions and generates elementary silver, the metallic silver grows in a state of a nanobelt, so that MgAl-Mo of the application₃S₁₃the-LDH can be used for preparing the elemental silver nanobelt.

The present application will be specifically described below with reference to examples, but the present application is not limited to these examples.

Example 1MgAl-Mo₃S₁₃Preparation of LDH

1.MgAl-NO₃Synthesis of-LDH

MgAl-CO synthesis by uniform precipitation method₃-LDH precursor: 3.21g Mg (NO)₃)₂·6H₂O、3.24g Al(NO₃)₃·9H₂O, 2.28g of Hexamethylenetetramine (HMT) and 50mL of deionized water are added into a reaction kettle, the reaction kettle is placed into a drying oven to react for 24 hours at the temperature of 140 ℃, the mixture is taken out to be cooled to the room temperature, the filtration is carried out and the washing is carried out for a plurality of times by using distilled water, the filtrate is light yellow, the solid is placed into the drying oven to be dried at the temperature of 40 ℃, and white powder MgAl-CO is obtained₃-LDH。

Synthesis of MgAl-NO by ion exchange method₃-LDH: 1.00g of MgAl-CO₃-LDH、100gNaNO₃0.36mL of concentrated nitric acid and 1000mL of boiled and exhausted deionized water are added into a conical flask, the conical flask is plugged by a plug and then sealed by a sealing film, and the mixture is stirred for 24 hours at room temperature. Immediately filtering, washing with deionized water and acetone for several times, and vacuum drying at 40 deg.C to obtain white powder MgAl-NO₃-LDH。

2.(NH₄)₂Mo₃S₁₃·H₂Synthesis of O

0.4g (NH) of the reaction solution was placed in a 20mL stainless steel reactor having a polytetrafluoroethylene liner₄)₆Mo₇O₂₄.4H₂O、0.3g(NH₄OH). HCl and 9ml (NH)₄)₂S_xReacting at 220 deg.C, filtering, washing with water and acetone for several times, and drying to obtain 0.55g dark red needle crystal (NH)₄)₂Mo₃S₁₃·H₂O。

3.MgAl-Mo₃S₁₃Synthesis of-LDH

Weighing 0.063g (NH)₄)₂Mo₃S₁₃·H₂Grinding O into powder in a mortar, and putting the powder into a beaker. Adding a total of 200mL of DMF solution into a beaker in batches, stirring, performing ultrasonic treatment to completely dissolve solids, and centrifuging to obtain a clear dark red solution. 0.05g of MgAl-NO₃The white powder of-LDH was charged with the above (NH) -containing compound₄)₂Mo₃S₁₃In the DMF solution, a plug is plugged, a sealing film is sealed, and the mixture is kept stand at room temperature for 24 hours. The solution remained dark red after the reaction, and was filtered, the filtrate was clear light red, and the solid was washed with DMF until the filtrate was substantially colorless (to remove insoluble or precipitated (NH)₄)₂Mo₃S₁₃) And then washed with a small amount of acetone to obtain a brownish red solid precipitate of 0.056 g.

₃ ₁₃Characterization of MgAl-MoS-LDH

1. Infrared absorption spectrum analysis

(NH₄)₂Mo₃S₁₃·H₂O、MgAl-NO₃LDH and MgAl-Mo₃S₁₃The results of infrared absorption spectroscopy analysis of-LDH are shown in FIG. 1, in which 547 and 505cm in (a)^-1The absorption peak at (NH) is₄)₂Mo₃S₁₃The Mo-S vibration of (1) is absorbed. (b) 3540 and 3456cm in length^-1The broad absorption peak of (1) belongs to the-OH (hydroxyl) oscillation peak of crystal water and the stretching oscillation peak of M-OH, wherein M represents Mg or Al, 1384cm^-1Peak of (A) is interlayer NO ₃ ^-676 and 438cm for vibration absorption^–1The absorption of which is attributed to the vibration of the M-O of the LDH sheets. (c) Middle 1384cm^-1The strength of the characteristic absorption peak is obviously weakened, which shows that Mo₃S₁₃ ^2-With NO₃ ^-Exchange and enter the interlayer to successfully obtain MgAl-Mo₃S₁₃-LDH. The MgAl-Mo prepared in example 1 is obtained by ICP and CHN element analysis₃S₁₃The chemical composition formula of-LDH is Mg_0.64Al_0.34(OH)₂(Mo₃S₁₃)_0.053(NO₃)_0.20·0.61H₂O, relative molecular mass 119.2.

X-ray powder diffraction analysis

MgAl-Mo₃S₁₃-LDH、MgAl-NO₃-LDH and (NH)₄)₂Mo₃S₁₃The results of X-ray powder diffraction (XRD) analysis of (A) are shown in FIG. 2. As can be seen from (a), MgAl-Mo₃S₁₃-LDThe H spectrogram has stable baseline, diffraction peaks at 0.91 and 0.45nm, and interlayer spacing of 0.91 nm. With precursors (NH)₄)₂Mo₃S₁₃(c) In contrast, MgAl-Mo₃S₁₃Disappearance of diffraction peaks at 0.87, 0.82, 0.54nm of-LDH (a), indicating absence of (NH) in the complex₄)₂Mo₃S₁₃The precursor and the product are pure. MgAl-Mo₃S₁₃LDH (a) with MgAl-NO₃Increase of the interlayer spacing from the original 0.89nm to 0.91nm in comparison with that of-LDH (b), indicating a larger volume of Mo₃S₁₃ ^2-And entering the interlayer. (a) The peak at medium 0.15nm corresponds to diffraction at the (110) plane on the LDH platelets, indicating that the LDH platelets are retained, as is topological ion exchange.

3. Analysis by scanning Electron microscope

MgAl-Mo₃S₁₃The Scanning Electron Microscope (SEM) picture of-LDH is shown in FIG. 3, in which (a) picture is the synthesized MgAl-Mo₃S₁₃LDH samples, which are seen to be clearly hexagonal in shape, with sample diameters of about 2-3 μm and exhibiting an ultra-thin nanosheet structure. (b) The figure shows MgAl-Mo after adsorbing 400ppm silver ion₃S₁₃SEM images of LDH samples, it can be seen that the size and morphology do not vary much, but there is little stacking, substantially maintaining hexagonal morphology.

₃ ₁₃Adsorption experiment of MgAl-MoS-LDH on silver ions

1.MgAl-Mo₃S₁₃Adsorption of Ag by LDH in Mixed solutions⁺

0.020g of MgAl-Mo is taken₃S₁₃LDH in 50mL centrifuge tubes, 20mL of Co-containing solution having a concentration of 10ppm each²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Ag⁺、Pb²⁺、Cd²⁺、Hg²⁺Nitrate solution of eight kinds of metal ions, sealing the centrifugal tube and oscillating for 24 h. Centrifuging at 15000r/min, standing, collecting 6mL supernatant, and detecting the content of each metal ion in the solution by inductively coupled plasma emission spectrometry (ICP), the results are shown in Table 1.

TABLE 1

TABLE 1MgAl-Mo₃S₁₃LDH for Ag in mixed solution⁺The adsorption capacity of (1). As can be seen from the table, MgAl-Mo is present in the mixed system₃S₁₃-LDH vs Ag⁺The removal rate of the catalyst can reach more than 99.99 percent, which indicates that MgAl-Mo₃S₁₃-LDH vs Ag⁺Has strong adsorption and removal capacity; in addition, in the mixed system, the partition coefficient K is generally adopted_dThe size of (A) represents the separation selectivity; MgAl-Mo of the present application₃S₁₃Adsorption of Ag by-LDH⁺Distribution coefficient K of_dCan reach 1.4 multiplied by 10⁷mL/g, which indicates MgAl-Mo₃S₁₃-LDH vs Ag⁺Has high selectivity. Further, the inventors found that MgAl-Mo of the present application₃S₁₃-LDH vs. Pb²⁺、Cu²⁺And Hg²⁺Also has certain adsorption force.

2.MgAl-Mo₃S₁₃-LDH vs Ag⁺Equilibrium adsorption experiment of

Respectively weighing 9 parts of 0.02g MgAl-Mo₃S₁₃LDH in 50mL centrifuge tubes, 20mL of different concentrations of Ag were added to each tube⁺Nitrate solution (concentration see C in Table 2)₀) The centrifuge tube was sealed and shaken for 24 h. The centrifugation was carried out at 15000r/min, the supernatant was allowed to stand, and 6mL of each supernatant was subjected to ICP measurement, and the results are shown in Table 2.

TABLE 2

As can be seen from Table 2, when Ag is used⁺Ag at an initial concentration of less than 1000ppm⁺The removal rate can reach more than 95 percent, K_dValue of 10⁴～6.9×10⁷mL/g, which indicates MgAl-Mo₃S₁₃LDH is effective in removing Ag from solution⁺(ii) a When Ag is present⁺The concentration continued to increase to 1660ppm, the adsorption was near equilibrium, Ag⁺Maximum adsorption q_m1073mg/g, i.e. 1.07g/g of adsorbent, corresponding to 1g of adsorbent capable of adsorbing 1.07g of Ag⁺The adsorption effect is higher than the adsorption amount reported in most literatures.

Adsorption isotherm data can be fitted using a Langmuir adsorption isotherm model (see equation 1). The model assumes that a monolayer of adsorbed species is coated on the adsorbent surface, and assuming that each adsorption site is occupied, the same site can no longer be adsorbed.

In the formula 1, q (mg/g) is Ag⁺Equilibrium adsorption amount of (c)_e(mg/L) is the concentration at adsorption equilibrium, q_m(mg/g) is the theoretical maximum adsorption; k_LIs the adsorption equilibrium constant. In Ag⁺When the concentration is 10-1600ppm, the adsorption amounts q and c_eThe relationship fits well to the Langmuir model and the results of the fit are shown in fig. 4. Fitting the resulting theoretical maximum adsorption q_mIs 1063mg/g, and is close to the maximum adsorption amount of 1073mg/g measured by the experiment. Correlation coefficient R of fitting process²0.997, indicating that the experimental data and Langmuir adsorption model are in good agreement.

3.MgAl-Mo₃S₁₃-LDH vs Ag⁺Study of adsorption kinetics

Respectively weighing 5 parts of 0.02g MgAl-Mo₃S₁₃LDH in 50mL centrifuge tubes, 20mL Ag was added to each tube⁺Nitrate solution with the concentration of 10ppm, a sealing film seals the centrifuge tube, the centrifuge tube is respectively vibrated for 1 min, 10min, 60min, 180 min and 360min, the centrifuge tube is centrifuged, the rotating speed is 15000r/min, the centrifuge tube is kept still, 6mL of supernatant is respectively taken for ICP test, and the results are shown in Table 3.

TABLE 3

The results of the adsorption kinetics experiments are shown in table 3. Visible Ag⁺The adsorption rate of (a) is very fast. Within 10min, Ag⁺The removal rate is close to 90%. Within 60min (1h), Ag⁺The concentration is reduced to 0.001ppm (1 ppb), and the removal rate is improved>99.99%, adsorption is essentially complete, K_dUp to 10⁷mL/g. To analyze Ag in MgAl-Mo₃S₁₃Adsorption rate on LDH and rate control procedure, experimental data were fitted using quasi-second order kinetics (formula 2). In the formula 2, q_e(mg/g) represents the adsorption amount at equilibrium, q_tThe amount of adsorption at the contact time t, k₂(g·mg^-1·min^-1) Rate constants in the quasi-secondary kinetic model. FIG. 5 shows Ag⁺The kinetic experimental data and the fitted curve, the kinetic parameters are shown in table 4. Fitting to obtain correlation coefficient (R)²) Is-1 (0.9999), which indicates that the adsorption process conforms to a quasi-second order kinetic model and belongs to chemical adsorption.

TABLE 4 MgAl-Mo₃S₁₃Adsorption of Ag by-LDH⁺Second order dynamics fitting parameters of

4.MgAl-Mo₃S₁₃-LDH vs Cu²⁺、Ag⁺Study on the separation ability of

According to MgAl-Mo₃S₁₃Adsorption of Ag by LDH in Mixed solutions⁺As a result, MgAl-Mo₃S₁₃-LDH vs Ag⁺And Cu²⁺Has high adsorption capacity. Considering Ag in many natural ores⁺The method is in a copper-rich environment, and has important significance for the rapid and low-cost separation of copper and silver. Thus, this application has investigated MgAl-Mo₃S₁₃Whether or not LDH can be derived fromHigh concentration of Cu²⁺Extracting trace silver from the solution. The fixed silver ion concentration is about 1ppm, Cu²⁺The concentration increased from 0.5ppm to 520ppm, investigating MgAl-Mo₃S₁₃-LDH vs Ag⁺Selective adsorption performance of.

Respectively taking 6 parts of 0.02g MgAl-Mo₃S₁₃LDH in 50mL centrifuge tubes, 20mL of each tube containing Cu at different concentrations²⁺And 1ppm Ag⁺Sealing the centrifugal tube, and oscillating for 24 h. After centrifugation at 15000r/min and standing, 6mL of each supernatant was taken out and subjected to ICP testing, and the results are shown in Table 5.

TABLE 5 MgAl-Mo₃S₁₃-LDH vs Cu²⁺、Ag⁺Selective adsorption of

To show Cu in the table²⁺And Ag⁺Molar ratio and removal rate of (A) and K_dThe values are plotted as shown in FIG. 6, where the abscissa of the (a) plot is Cu²⁺And Ag⁺In a molar ratio of (A) and the ordinate is Ag⁺、Cu²⁺Removal rate, (b) the abscissa of the graph is Cu²⁺And Ag⁺In a molar ratio of (C), the ordinate is Cu²⁺And Ag⁺Distribution coefficient K of_dThe separation factor SF (Ag/Cu). As can be seen from the (a) diagram, when Cu²⁺/Ag⁺When the molar ratio is gradually increased, MgAl-Mo₃S₁₃The adsorption rate of LDH to copper ions gradually decreases (99.8% → 11.4%), while Ag⁺The adsorption rate is always kept at a high level (>99.9%), indicating MgAl-Mo₃S₁₃LDH has a high capacity to separate these two ions. As can be seen from the (b) diagram, when Cu is present²⁺And Ag⁺When the molar ratio of (A) to (B) is gradually increased, the separation factor SF_(Ag/Cu)Also gradually increases, and SF is added when the Cu/Ag mass ratio is 520 and the molar ratio is 874_(Ag/Cu)Up to 7969 (8000) which indicates MgAl-Mo₃S₁₃-LDH vs. Cu at high concentration²⁺Low concentration of Ag⁺Mixed systems, especially effective in separationAre prominent. MgAl-Mo to illustrate the present application₃S₁₃LDH can be made Cu-rich²⁺And extracting Ag from a low-grade Ag system.

5. Generation and analysis of elemental silver nanobelts

The inventor aims at MgAl-Mo₃S₁₃-LDH vs Ag⁺In the equilibrium adsorption experiment of (1), it was surprisingly found that in Ag⁺Elemental silver was observed to be produced in solutions with concentrations greater than 800 ppm; further, with Ag⁺The greater the concentration, the greater the amount of elemental silver produced.

MgAl-Mo₃S₁₃-LDH vs Ag⁺In the equilibrium adsorption experiment, the solid sample after the adsorption experiment is completed is dried and subjected to XRD analysis, and the result is shown in FIG. 7; wherein, the diagram (A) is MgAl-Mo₃S₁₃LDH adsorbing different concentrations of Ag⁺XRD spectrum of the solid sample; (B) the figure is 1000ppm Ag⁺Slow-scanning XRD (X-ray diffraction) spectrum of adsorbed solid sample, Ag and Ag₂And (4) a standard spectrogram of S. As can be seen from (b) and (c) of the graph (A), MgAl-Mo₃S₁₃LDH adsorbing Ag at low concentrations, e.g. 10ppm, 100ppm⁺After that, the interlayer distance of the adsorbed solid became 0.89nm, and the inventors thought that this is probably because Mo is not limited to any theory₃S₁₃ ^2-With Ag⁺Complexation of Mo₃S₁₃ ^2-The arrangement between the layers is more regular, which leads to the reduction of the interlayer spacing, and simultaneously, along with Ag⁺Into the interlayer to balance the positive charge, NO₃ ^-Into the interlayer to make the interlayer spacing close to NO₃ ^-Interlayer spacing of intercalated LDH. MgAl-Mo₃S₁₃LDH adsorbing Ag at 400ppm (d) and 1000ppm (e)⁺Thereafter, compared with (a), the series of diffraction peaks corresponding to the layered double hydroxide disappeared, and Ag appeared₂And the diffraction peak of S is strong. High concentration of Ag such as 1000ppm⁺The appearance of bright metal can be observed by naked eyes on the adsorbed sample, and the generation of simple substance silver is presumed to be possible. It can be seen from the results of slow-scan XRD test (B diagram) that except for Ag₂In addition to the diffraction peak of S, the diffraction peak of the simple substance Ag was observed, and thus the generation of the simple substance Ag was confirmed.

More unexpectedly, the inventors formed Ag⁺The concentration is increased to 1300ppm, the adsorption process is kept still, silver crystals grow naturally, and a large amount of bright white silver wires can be observed to be generated, as shown in a picture A of figure 8. After the adsorption, the sample was carefully taken out and observed by SEM, and as a result, as shown in B-I diagram of FIG. 8, elemental silver was seen to be filamentous (E, F diagram), the thickness was in nanometer level (I diagram), the width was about 10-20 μm (H diagram), and the length was in centimeter level (F diagram). MgAl-Mo to illustrate the present application₃S₁₃LDH produces elemental silver nanoribbons during the adsorption of silver ions. Compared with the massive or powdery simple substance silver, the silver nanobelt has higher specific surface area, and can obtain higher catalytic activity when being used as a catalyst.

In order to confirm that the generated substance is elemental silver, X-ray photoelectron spectroscopy (XPS) was performed on the adsorbed solid, and the result of the change in valence state of the relevant element, particularly Mo, during the adsorption process is shown in fig. 9. Known Compound (NH)₄)₂Mo₃S₁₃Mo in (b) is +4 valent, (a) shows that for 800ppm Ag⁺Solid sample after adsorption, except Mo⁴⁺Peak of (2) and peak of 229.6eV, peaks at binding energies of 235.6 and 232.7eV, respectively, corresponding to Mo ⁶⁺3d of_3/2And 3d_5/2Showing Mo⁶⁺Formation of an oxidation state. (b) The graph shows the contrast to 1300ppm Ag⁺Sample after adsorption, Mo at 229.5eV ⁴⁺3d_5/2The intensity of the peaks is further reduced, Mo at 232.6 and 235.6eV ⁶⁺3d_5/2And 3d_3/2The peak of (A) becomes strong, indicating that Mo is present⁶⁺The content of (c) increases. Furthermore, (a ') and (b') show that along with Ag⁺The increase in concentration, 162.5/162.7eV (Peak 5) corresponds to S₂ ^2-Decrease in peak intensity of (A), indicating S₂ ^2-Is decreased, indicating S₂ ^2-Redox reactions may occur, converting to other forms. Meanwhile, the binding energies of the peaks at 368.3eV assigned to elemental Ag 3d are shown in graphs (a ") and (b"), indicating the presence of elemental silver.

According to the XPS results, molybdenum in the adsorbed solid is mainly in +6 valence, and the inventors speculate that molybdenum therein may beCan be MoS₄ ^2-、MoO₄ ^2-Or MoO₃In the form of (A) and (B) are water-soluble, the latter being MoO₃Are poorly soluble. The sulfur is oxidized and possibly changed into the element S which is difficult to dissolve in water⁰Or water-soluble SO₄ ^2-. The present application proposes the following three possible reactions:

(1)Mo₃S₁₃ ^2-+50Ag⁺+32H₂O→8Ag₂S+5SO₄ ^2-+3MoO₄ ^2-+34Ag⁰+64H⁺

(2)Mo₃S₁₃ ^2-+20Ag⁺+9H₂O→7Ag₂S+6S⁰+3MoO₃+6Ag⁰+18H⁺

(3)Mo₃S₁₃ ^2-+50Ag⁺+29H₂O→8Ag₂S+5SO₄ ^2-+3MoO₃+34Ag⁰+58H⁺

in these three reactions, (1) MoO obtained₄ ^2-And SO₄ ^2-Are both water-soluble, (2) insoluble element S is obtained⁰And MoO₃(3) obtaining soluble SO₄ ^2-And insoluble MoO₃. In order to determine which reaction is more representative of the reaction actually generated by the adsorption system, adsorption experiments with different adsorption time are designed, and the ICP method is used for measuring Ag in the solution⁺The amount remaining, and the amount S, Mo in solution increasing with time. As can be seen from the data in Table 6 and the graphs (c) and (d) of FIG. 9, Ag in the stock solution increased with the contact time⁺Is continuously reduced and the concentration of sulfur released into the solution is continuously increased. Although the presence of molybdenum in the solution was also detected and its concentration slightly increased with time, the content of molybdenum was very low with respect to sulfur, with an S/Mo ratio of 12 to 62, much greater than the S/Mo ratio corresponding to reactions (1) to (3) (1.7 to 2, i.e. 5:3 to 6: 3). Therefore, the inventors believe that the molybdenum released into the solution is negligible, i.e. no soluble Mo compounds are formed, and therefore reaction (1) may be excluded. For reaction (2), S, which is insoluble in water, cannot account for the higher levels detected in solutionThe S element of (1), and thus reaction (2) is also excluded.

According to reaction formula (3), when the adsorption reached equilibrium, the molar weight ratio of the amount of reduction of silver (Δ Ag) to the amount of increase of sulfur (Δ S) (i.e., Δ Ag/Δ S) was 10, which is in good agreement with the experimentally determined Δ Ag/Δ S ratio of 10.06 (at a contact time of 18 h). Insoluble MoO is formed in this reaction₃It also explains why only trace amounts of Mo are detected in the solution. In addition, in graphs c and d of FIG. 7, it can be seen that Δ Ag/Δ S rises first and falls second. A relatively high ratio of Δ Ag/Δ S means less sulfur is released into the solution during the initial period, indicating that the reduction in Ag does not result in a corresponding increase in S in the solution at this stage, presumably by Ag⁺And S^2-Precipitation is the main reaction to generate insoluble Ag₂And S. In the later stage of adsorption, redox reaction predominates, Ag⁺Reduction to form metallic Ag⁰And S is_x ^2-Oxidized to soluble SO₄ ^2-Released into solution. Thus, the sulfur detected in the solution at this time increased significantly and Δ Ag/Δ S decreased. From this, it is presumed that the initial stage of the silver adsorption process is mainly precipitation reaction to form Ag₂S, the adsorption later stage is mainly oxidation-reduction reaction and Ag⁺Is reduced to generate simple substance Ag.

Table 6 shows the relationship between the decrease and increase in Ag concentration and S, Mo and the ratio of decrease and increase in Ag, Δ Ag/Δ S, to the adsorption time.^a

The combination of the above experimental results shows that MgAl-Mo of the present application₃S₁₃The LDH has excellent selective adsorption capacity for silver ions, can adsorb the silver ions in an environment rich in copper ions with high selectivity, and can extract trace silver from the copper-rich environment. More surprisingly, the MgAl-Mo of the present application₃S₁₃LDH, which, after adsorption of silver ions, reduces the silver ions to elemental silver and is therefore useful for the extraction of metallic silver, and furthermore, the elemental silver is produced in the form of nanoribbons (with a thickness on the nanometer scale), and therefore MgA of the present applicationl-Mo₃S₁₃the-LDH can be used for preparing the elemental silver nanobelt.

The above description is only for the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A molybdenum sulfide layered double metal hydroxide complex, wherein, molybdenum sulfide anion cluster Mo₃S₁₃ ^2-Intercalated between layers of the layered double hydroxide of magnesium aluminum.

2. The molybdenum sulfide layered double hydroxide complex according to claim 1, having the following chemical composition formula: mg (magnesium)_0.64Al_0.34(OH)₂(Mo₃S₁₃)_x(NO₃)_y·mH₂O, wherein x is 0.05 to 0.10, y is 0.10 to 0.24, and m is 0.5 to 1.2.

3. A method of preparing a molybdenum sulfide layered double hydroxide complex as claimed in claim 1 or 2, comprising:

will be (NH)₄)₂Mo₃S₁₃·H₂Dissolving O in N, N' -dimethyl formamide or dimethyl sulfoxide to obtain MgAl-NO₃And (3) putting LDH into the reaction kettle, standing the reaction kettle for 20 to 30 hours in an air-isolated environment, filtering and washing the reaction kettle to obtain the molybdenum sulfide layered double hydroxide complex precipitate.

4. The method of claim 3, wherein the washing comprises washing the solid with N, N' -dimethylformamide or dimethylsulfoxide until the filtrate is colorless, followed by washing with acetone.

5. The method of claim 3 or 4, wherein (NH)₄)₂Mo₃S₁₃·H₂Of O with N, N' -dimethylformamide or dimethyl sulfoxideThe mass-volume ratio is 0.3-0.5 mg/ml.

6. The method according to claim 3 or 4, wherein the (NH)₄)₂Mo₃S₁₃·H₂O and MgAl-NO₃The mass ratio of-LDH is 1: 0.7-1: 1.

7. Use of the molybdenum sulfide layered double hydroxide complex according to claim 1 or 2 for adsorbing Ag⁺The use of (1).

8. Use of the molybdenum sulphide layered double hydroxide complex as defined in claim 1 or 2 for extracting metallic silver.

9. Use of the molybdenum sulfide layered double hydroxide complex as claimed in claim 1 or 2 for the preparation of elemental silver nanobelts.

10. A silver ion adsorbing material comprising the molybdenum sulfide layered double hydroxide complex of claim 1 or 2.