Silver-copper ferrite-iron based metal-organic framework composite material, preparation method and application thereof

Abstract

The application provides a preparation method of a silver-copper ferrite-iron-based metal organic framework composite material, and comprises the following steps: step S1, a copper ferrite material is prepared by improving a pH value and a hydrothermal temperature and by adding different additives through a modified solvothermal method; step S2, an iron-based metal organic framework material is prepared by improving a pH value and stirring conditions at room temperature through a sol-gel method; step S3, a heterostructure is formed by combining the copper ferrite material and the iron-based metal organic framework material through an ultrasonic method, so that a copper ferrite-iron-based metal organic framework composite material is obtained; and step S4, a silver quantum dot is photo-deposited on the surface of the copper ferrite-iron-based metal organic framework composite material through a photo-deposition method, so that a silver-copper ferrite-iron-based metal organic framework composite material is prepared. The silver-copper ferrite-iron-based metal organic framework composite material prepared by the application can be used for removing oxygen-containing acid salt pollutants in drinking water, such as nitrate, bromate and chlorite, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of drinking water treatment, and in particular relates to a silver-copper ferrite-iron-based metal organic framework composite material, a preparation method and an application thereof. Background Art

[0002] Oxygenate pollutants such as nitrate (NO3 - ), bromate (BrO3 - ) and chlorite (ClO2 - ) are common non-metallic oxides in water, with high solubility and mobility. They are widely present in natural and treated water bodies worldwide. Groundwater, an important source of drinking water, suffers from excessive nitrate levels in areas such as northern my country, potentially causing hazards such as hemoglobinemia. Furthermore, byproducts such as bromate, chlorate, and chlorite produced during water plant disinfection processes pose a serious threat to human health and have drawn considerable attention.

[0003] Oxygenated salt pollutants have the characteristics of small molecular weight and stable properties. Currently, the commonly used treatment methods for drinking water are physical methods and chemical methods, such as reverse osmosis membrane method, ion exchange method, adsorption method, chemical reduction method, and electrochemical reduction method. These methods have the disadvantages of high energy consumption, large dosage of reagents, harsh reaction conditions and low removal rate. In recent years, advanced reduction methods based on active groups have broad prospects as a new technology. Research has found that e aq - 、H · 、CO2 ·- 、SO3 2- Reducing free radicals can efficiently remove oxygenated salts under mild conditions. Compared with the addition of certain chemical agents such as metal ions in the same phase advanced reduction, which is easy to cause secondary pollution, the heterogeneous advanced reduction has the characteristics of low dosage of agents (such as nitrate reduction) or no addition of agents (such as bromate and chlorite reduction), removing oxygenated salt pollutants and selectively converting them into N2, Br - and Cl - By adding additives, it can be mineralized into CO2, which has great application prospects in drinking water treatment.

[0004] The current heterogeneous advanced reduction technology is mainly based on titanium oxide, and sulfides and perovskites are also studied, but there is a risk of secondary pollution of the catalyst. Silver nanoparticles have surface plasmon resonance effect, and the use of silver modification can effectively improve the photoelectron lifetime and the reduction efficiency, but the effect of silver modified TiO2 decreases significantly after recycling, and it is difficult to recover. Spinel materials have good photoelectric effect, among which copper ferrite (CuFe2O4) has the characteristics of wide preparation materials, simple preparation, stable properties, non-toxicity, etc. In particular, its magnetic property facilitates recycling and use, and it is a green and efficient catalyst, which has a good prospect in drinking water treatment and is rarely studied. Metal organic framework (MOF) is a new type of semiconductor material composed of metal clusters and organic ligands, which has rich porous structure, more active sites and high specific surface area. Among them, iron-based metal organic framework material has high photocatalytic performance. The heterogeneous catalyst composed of spinel material and iron-based metal organic framework material can effectively form a heterojunction structure, effectively improve the photo quantum yield and pollutant reduction efficiency. However, there is no report on the use of silver-copper ferrite-iron-based metal organic framework catalyst in the field of advanced reduction technology for several kinds of oxygen-containing acid salt pollutants in drinking water treatment. SUMMARY

[0005] The present application is to solve the above problems, and aims to provide a silver-copper ferrite-iron-based metal organic framework composite material and a preparation method and application thereof.

[0006] The present application provides a preparation method of a silver-copper ferrite-iron-based metal organic framework composite material, which has the following characteristics and comprises the following steps:

[0007] In step S1, iron nitrate and copper nitrate are weighed and placed in a solvent for stirring until they are dissolved uniformly to obtain a mixed solution. The pH of the mixed solution is adjusted, and the suspension is obtained after continuous stirring and dispersion. The suspension is subjected to hydrothermal reaction to obtain a first mixture. The copper ferrite material is obtained after separation, washing, drying and grinding of the first mixture.

[0008] In step S2, trimesic acid and sodium hydroxide solution are mixed and stirred, and the pH is adjusted. After slow stirring and ultrasonic treatment, solution A is obtained. Ferrous chloride is dissolved in deionized water and slowly stirred to obtain solution B. Solution A is added dropwise to solution B, and the pH is adjusted. After slow stirring, a second mixture is obtained. The iron-based organic framework material is obtained after separation, washing, drying and grinding of the second mixture.

[0009] In step S3, the copper ferrite material and the iron-based organic framework material are weighed and dissolved in ethanol for ultrasonic treatment to obtain a third mixture. The copper ferrite-iron-based metal organic framework composite material is obtained after separation, washing, drying and grinding of the third mixture.

[0010] Step S4, weigh the copper ferrite-iron metal organic framework composite material into a quartz tube, add silver nitrate, formic acid and deionized water, stir uniformly, then irradiate with a mercury lamp to obtain a fourth mixture, and then separate, wash, dry and grind the fourth mixture to obtain a silver-copper ferrite-iron metal organic framework composite material.

[0011] In the preparation method of the silver-copper ferrite-iron metal organic framework composite material provided by the application, the following features can also be present: in step S1, the solvent is deionized water, ethylene glycol or ethanol, and when adjusting the pH of the mixed solution, sodium hydroxide is used to adjust the pH of the mixed solution to 9.0-11.0, and the suspension is obtained after 30 min of continuous stirring for dispersion; and a modifier is also added after adjusting the pH of the mixed solution, and the modifier is PVP, citric acid or urea.

[0012] In the preparation method of the silver-copper ferrite-iron metal organic framework composite material provided by the application, the following features can also be present: in step S1, the suspension is subjected to hydrothermal reaction in a polytetrafluoroethylene reaction kettle, the temperature during the hydrothermal reaction is 120-160 DEG C, and the time is 12-20 h; and when the first mixture is separated and washed, it is washed with ethanol and deionized water and centrifuged three times.

[0013] In the preparation method of the silver-copper ferrite-iron metal organic framework composite material provided by the application, the following features can also be present: in step S2, after the mixture of trimesic acid and sodium hydroxide solution is stirred, the pH is adjusted to 11.0, and the ultrasonic time is 2 h.

[0014] In the preparation method of the silver-copper ferrite-iron metal organic framework composite material provided by the application, the following features can also be present: in step S2, after solution A is added dropwise to solution B, the pH is adjusted to 10.0-12.0, and then slowly stirred for 12-24 h; and when the second mixture is separated and washed, it is washed with ethanol and deionized water and centrifuged three times.

[0015] In the preparation method of the silver-copper ferrite-iron metal organic framework composite material provided by the application, the following features can also be present: in step S3, the mass ratio of the copper ferrite material and the iron-based organic framework material is 1:1-5, the copper ferrite material and the iron-based organic framework material are dissolved in ethanol and ultrasonically treated for 2-6 h; and when the third mixture is separated and washed, it is washed with ethanol and deionized water and centrifuged three times.

[0016] In the preparation method of the silver-copper ferrite-iron-based metal organic framework composite provided by the application, the following features can also be present: in step S4, the mercury lamp has a power of 500 W, and the irradiation time is 3 h; when the fourth mixture is separated, washed, dried, and ground, the fourth mixture is centrifuged, washed repeatedly with water and ethanol three times, and then ground after being dried at 80 DEG C for 12 h; and the mass percentage of silver in the silver-copper ferrite-iron-based metal organic framework composite is 0.1 wt% to 2 wt%.

[0017] The application also provides a silver-copper ferrite-iron-based metal organic framework composite, which is prepared by the above preparation method of the silver-copper ferrite-iron-based metal organic framework composite.

[0018] The application also provides a use of the above silver-copper ferrite-iron-based metal organic framework composite in removing oxygen-containing acid salt pollutants in drinking water, which comprises: mixing the silver-copper ferrite-iron-based metal organic framework composite with nitrate salt pollutants, bromate salt pollutants, and chlorite salt pollutants, and combining with a hole trapping agent and a UV light source to catalyze the reduction of nitrate, bromate, and chlorite in water, and the specific process is as follows:

[0019] When the concentration of the nitrate salt pollutants is 0.5 to 2 mmol / L, the silver-copper ferrite-iron-based metal organic framework composite is added in an amount of 0.1 to 0.5 g / L, the hole trapping agent formic acid is added in an amount of 1 to 5 mmol / L, and a 500 W mercury lamp is used as the light source;

[0020] When the concentration of the bromate salt pollutants is 0.1 to 1 mmol / L, the silver-copper ferrite-iron-based metal organic framework composite is added in an amount of 0.1 to 0.5 g / L, and a 100 W mercury lamp is used as the light source;

[0021] When the concentration of the chlorite salt pollutants is 0.1 to 1 mmol / L, the silver-copper ferrite-iron-based metal organic framework composite is added in an amount of 0.1 to 0.5 g / L, and a 15 W mercury lamp is used as the light source.

[0022] Effects and advantages of the application

[0023] According to the preparation method of the silver-copper ferrite-iron-based metal organic framework composite, the copper ferrite material is synthesized by the improved solvothermal method, the uniformity of the complexing process is controlled by improving the pH value and the hydrothermal temperature, and different additives are appropriately added, so that the particle morphology of the synthesized material can be effectively controlled, the crystal with uniform particle size is formed, and the crystal structure is stabilized by controlling the hydrothermal time, so that the copper ferrite crystal has good crystallization and uniform particle size; and the iron-based organic framework material is prepared by using the sol-gel method at room temperature, by improving the pH value and the stirring condition.

[0024] Then the ultrasonic method is used to combine the copper ferrite material and the iron-based metal organic framework material to form a heterostructure, so that a new type of photocatalytic material is formed as a copper ferrite-iron-based metal organic framework composite material; the iron-based metal organic framework material acts as a skeleton to make the copper ferrite material more uniformly distributed, increase the reactive sites, promote the separation of electrons and holes, and improve the light quantum yield and catalytic performance;

[0025] Finally, the silver quantum dots are deposited on the surface of the copper ferrite-iron-based metal organic framework composite material by the photodeposition method to prepare a silver-copper ferrite-iron-based metal organic framework composite material, so that the silver-copper ferrite-iron-based metal organic framework composite material has the characteristics of stability and recyclability.

[0026] Further, the silver-copper ferrite-iron-based metal organic framework composite material prepared by the method has a metal organic framework material as a skeleton and forms a heterojunction, and can efficiently and selectively remove nitrate in water by using a high-level reduction technology, has a high removal rate for bromate and chlorite and other oxygen-containing acid salt pollutants, controls the reaction path to increase the harmless products and reduce secondary pollution.

[0027] Therefore, the preparation method of the present application has simple process, and the preparation raw materials are widely available, and the silver-copper ferrite-iron-based metal organic framework composite material prepared by the method has high catalytic efficiency, high nitrogen conversion rate, non-polluted products, low chemical reagent dosage, and other characteristics in the application of high-level reduction of oxygen-containing acid salt pollutants, and is easy to recycle magnetically, has high reusability, and has wide application prospect in water treatment of nitrate, bromate and chlorite and other oxygen-containing acid salt pollutants. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the SEM diagram of the copper ferrite material prepared in Example 1 of the present application;

[0029] Figure 2 is the SEM diagram of the iron-based metal organic framework material prepared in Example 1 of the present application;

[0030] Figure 3 is the SEM diagram of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present application;

[0031] Figure 4 is the ESD spectrum diagram of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present application;

[0032] Figure 5 is the XRD spectrum diagram of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present application;

[0033] Figure 6is a removal effect diagram of silver-copper ferrite-iron-based metal organic framework composite material on 1mM nitrate in test example 1 of the present application;

[0034] Figure 7 is a 5-cycle effect diagram of catalytic reduction of 1mM nitrate in test example 2 of the present application;

[0035] Figure 8 is a removal effect diagram of silver-copper ferrite-iron-based metal organic framework composite material with different Ag contents on 1mM nitrate in test example 3 of the present application;

[0036] Figure 9 is a removal effect diagram of silver-copper ferrite-iron-based metal organic framework composite material on different concentrations of bromate in test example 5 of the present application;

[0037] Figure 10 is a removal effect diagram of silver-copper ferrite-iron-based metal organic framework composite material on different concentrations of chlorite in test example 6 of the present application. DETAILED DESCRIPTION

[0038] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the following examples combine the silver-copper ferrite-iron-based metal organic framework composite material and the preparation method and application of the present application with the drawings to make specific description.

[0039] <EMBODIMENT 1>

[0040] A preparation method of a silver-copper ferrite-iron-based metal organic framework composite material, comprising the following steps:

[0041] Step S1, weigh iron nitrate and copper nitrate and place them in a solvent to stir until dissolved uniformly to obtain a mixed solution, adjust the pH of the mixed solution, and after continuous stirring and dispersion, obtain a suspension, and after hydrothermal reaction of the suspension, obtain a first mixture, and after separation, washing, drying and grinding of the first mixture, obtain a copper ferrite material, and the specific process is as follows:

[0042] Fe(NO3)3·9H2O and 2.5 mmol of Cu(NO3)3·3H2O were added to a flask containing 80 ml of deionized water, mixed and stirred until dissolved uniformly to obtain a mixed solution, 5 mol / L of NaOH was added dropwise in the mixed solution and stirred until the solution pH value reached 10.0, and continued to be stirred vigorously for 30 min to make it uniformly dispersed to obtain a suspension, the suspension was transferred into a polytetrafluoroethylene reaction kettle with a volume of 110 ml for hydrothermal reaction, and the temperature was raised to 140±2℃ at a rate of 5℃ / min, the hydrothermal reaction time was 16 h, the reaction kettle was naturally cooled to room temperature, and the supernatant in the kettle was poured out to obtain a first mixture, the first mixture was washed with ethanol and deionized water and centrifuged three times, the centrifugal speed was 10000 rpm, the centrifugal time was 10 min, and the centrifuged solid was dried in an 80℃ oven for 8-12 h, ground into a powder with a agate mortar to obtain a copper ferrite material, i.e. copper ferrite spinel (CuFe2O4).

[0043] In step S2, the trimesic acid and the sodium hydroxide solution were mixed and stirred, the pH was adjusted, and then ultrasonic was applied after slow stirring to obtain solution A. The ferrous chloride was dissolved in deionized water and stirred slowly to obtain solution B. Solution A was added dropwise to solution B, and the pH was adjusted, and then slow stirring was applied to obtain a second mixture. After separation, washing, drying and grinding of the second mixture, an iron-based organic framework material was obtained, and the specific process was as follows:

[0044] In step S2, the trimesic acid and the sodium hydroxide solution were mixed and stirred, the pH was adjusted, and then ultrasonic was applied after slow stirring to obtain solution A. The ferrous chloride was dissolved in deionized water and stirred slowly to obtain solution B. Solution A was added dropwise to solution B, and the pH was adjusted, and then slow stirring was applied to obtain a second mixture. After separation, washing, drying and grinding of the second mixture, an iron-based organic framework material was obtained, and the specific process was as follows:

[0045] In step S3, the copper ferrite material and the iron-based organic framework material were weighed, dissolved in ethanol and ultrasonic was applied to obtain a third mixture. After separation, washing, drying and grinding of the third mixture, a copper ferrite-iron-based organic framework composite material was obtained, and the specific process was as follows:

[0046] Take 0.2 g of copper ferrite material and a certain amount of iron-based metal organic framework material into 50 ml of ethanol solvent, so that the mass ratio of copper ferrite material to iron-based metal organic framework material is 1:2, ultrasonic the mixture for 6 h to obtain a third mixture, wash and centrifuge the third mixture with ethanol and deionized water respectively for three times, the centrifugal speed is 10000 rpm, the centrifugal time is 10 min, dry the obtained solid in an oven at 80℃ for 8-12 h, grind the powder into a powder with a marble mortar to obtain a copper ferrite-iron-based metal organic framework material (CuFe2O4 / MIL-100(Fe)).

[0047] Step S4, take the copper ferrite-iron-based metal organic framework composite material into a quartz tube, add silver nitrate, formic acid and deionized water, stir uniformly, then irradiate with a mercury lamp to obtain a fourth mixture, separate, wash, dry and grind the fourth mixture to obtain a silver-copper ferrite-iron-based metal organic framework composite material, the specific process is as follows:

[0048] Take 0.2 g of copper ferrite-iron-based metal organic framework composite material and a certain amount of silver nitrate into a quartz reaction tube (the silver nitrate is taken according to the condition that the mass percentage of silver in the prepared silver-copper ferrite-iron-based metal organic framework material is 1wt%), add 50 ml of deionized water and 0.5 ml of formic acid as a reducing agent, stir uniformly, put the quartz reaction tube into a light reactor, use a 500w mercury lamp as the light source, the reaction time is 3h, the stirring speed of the magnetic stirrer is 100-120 rpm; after the reaction tube is naturally cooled to room temperature, a fourth mixture is obtained, centrifuge the fourth mixture, wash with ethanol and deionized water respectively for three times to obtain a powder, dry the powder at 80℃ for 8-12 h to obtain a silver-copper ferrite-iron-based metal organic framework composite material (Ag / CuFe2O4 / MIL-100(Fe)).

[0049] The mass percentage of Ag in the silver-copper ferrite-iron-based metal organic framework composite material prepared in this example is 1wt%, and the mass ratio of copper ferrite material to iron-based metal organic framework material is 1:2.

[0050] The surface physical and chemical properties of the silver-copper ferrite-iron-based metal organic framework composite material (Ag / CuFe2O4 / MIL-100(Fe)) are as follows:

[0051] The average pore size of the copper ferrite material (CuFe2O4) is 2.35 nm, the specific surface area is 154.72 m 2 / g, and the average particle size is 150-225 nm;

[0052] The specific surface area of the iron-based metal organic framework material (MIL-100(Fe)) is 920.30 m 2 / g, and the average particle size is 550-1050 nm;

[0053] The specific surface area of ​​silver-copper ferrite-iron-based metal organic framework composite material (1wt% Ag / CuFe2O4 / MIL-100(Fe)) is 721.32m 2 / g.

[0054] Figure 1 is a SEM image of the copper ferrite material prepared in Example 1 of the present invention.

[0055] like Figure 1 As shown, the copper ferrite material prepared in this embodiment is well crystallized and has uniform particles.

[0056] Figure 2 is a SEM image of the iron-based metal organic framework material prepared in Example 1 of the present invention.

[0057] like Figure 2 As shown, the iron-based metal organic framework material prepared in this embodiment is well crystallized and the particles are relatively uniform.

[0058] Figure 3 This is a SEM image of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present invention.

[0059] like Figure 3 As shown, it can be seen that the two materials are effectively bonded together, and the formed heterojunction structure can effectively separate electrons and holes. At the same time, the iron-based metal organic framework material serves as a skeleton to make the copper ferrite distribution more uniform, increase the reaction active sites, and improve the photon yield and reduction efficiency.

[0060] Figure 4 This is the ESD spectrum of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present invention.

[0061] like Figure 4 As shown, in the copper ferrite-iron-based metal organic framework composite material (CuFe2O4 / MIL-100(Fe) (mass ratio 1:2) prepared in this embodiment, copper ferrite and the iron-based metal organic framework material are effectively composited together, and different sites have different Fe and Cu contents.

[0062] Figure 5 This is the XRD spectrum of the copper ferrite-iron-based metal organic framework composite material prepared in Example 1 of the present invention.

[0063] like Figure 5 As shown, with reference to the standard diffraction peak pattern (JCPDS 77-0010), the copper ferrite material prepared in this embodiment has a spinel cubic crystal structure.

[0064] <Example 2>

[0065] In this embodiment, based on the same preparation conditions of step S1 in embodiment 1, only the solvent is adjusted to ethylene glycol and ethanol solvent, and a modifier is also added after adjusting the pH to prepare the cupric ferrite material, and the specific process is as follows:

[0066] The ferric nitrate and cupric nitrate are weighed and stirred in 80 ml of ethylene glycol and ethanol solvent to dissolve uniformly, the pH of the above mixed solution is adjusted to 10.0 using sodium hydroxide, 0.2 g of PVP or citric acid is added, or urea with the same molar concentration of total iron and copper ions is added as a modifier, and the mixed solution is stirred vigorously for 30 min to disperse uniformly to obtain a suspension. A 110 ml volume of reaction kettle is used for solvothermal reaction to obtain a first mixture. After separation, washing, drying and grinding of the first mixture, the cupric ferrite material is obtained.

[0067] In this embodiment, the cupric ferrite material is also prepared by adding a modifier. The cupric ferrite material prepared has a regular morphology, and has good catalytic reduction of oxygen-containing acid salt performance. When urea is used as a modifier, the cupric ferrite material obtained is rod-shaped.

[0068] <Embodiment 3>

[0069] In this embodiment, based on the same preparation conditions of step S1 in embodiment 1, only when adjusting the pH using sodium hydroxide, the pH is adjusted to 9.0 or 11.0, and the subsequent preparation of the cupric ferrite material is carried out.

[0070] In this embodiment, cupric ferrite materials with certain morphology and catalytic performance can be prepared under different pH conditions.

[0071] <Embodiment 4>

[0072] In this embodiment, based on the same preparation conditions of step S1 in embodiment 1, only the hydrothermal reaction in the reaction kettle is carried out under the following reaction conditions: temperature 120℃, time 12h and temperature 160℃, time 20h, and the subsequent preparation of the cupric ferrite material is carried out.

[0073] In this embodiment, under the solvothermal reaction conditions of 120℃ and 12h, the cupric ferrite material prepared has a regular morphology and good catalytic performance;

[0074] Under higher temperature and longer reaction time, such as 160℃ and 20h, the cupric ferrite material prepared has a more regular crystal form and improved catalytic performance.

[0075] <Embodiment 5>

[0076] In this embodiment, based on the same preparation conditions as step S2 in Example 1, only in the process of adding solution A to solution B and adjusting the pH, and then slowly stirring to obtain the second mixture, the pH value can be adjusted to 10.0, the slow stirring time can be adjusted to 12h or 18h, and subsequent preparation is carried out to obtain the iron-based organic framework material.

[0077] In this embodiment, iron-based organic framework materials can be obtained under different pH conditions, and as the stirring time increases, the catalytic performance of the material improves. After washing and separation, iron-based organic framework materials with regular morphology and good catalytic performance can be obtained.

[0078] <Example 6>

[0079] In this embodiment, based on the same preparation conditions as step S3 in embodiment 1, only the ultrasonic time was adjusted to 2 h or 4 h during the ultrasonication, and subsequent preparation was performed to obtain a copper ferrite-iron-based metal organic framework composite material.

[0080] In this embodiment, when preparing the copper ferrite-iron-based metal organic framework composite material, the ultrasonic method is used to form a CuFe2O4 / MIL-100(Fe) heterojunction, which can effectively improve the catalytic performance of the composite material. In addition, 2h of ultrasound can also form an effective heterojunction, thereby improving the catalytic performance of the composite material.

[0081] <Test Example 1>

[0082] In this test example, the silver-copper ferrite-iron-based metal organic framework composite material prepared in Example 1 was used to photocatalyze the reduction of nitrate to nitrogen gas, as follows:

[0083] A quartz reaction trap was filled with 0.04g of a silver-copper ferrite-iron metal-organic framework composite (CuFe2O4 and MIL-100(Fe) in a 1:2 mass ratio, with 1wt% Ag) and 200ml of a 1mM nitrate solution. The mixture was stirred in the dark for 30 minutes until adsorption equilibrium was reached. Formic acid, a hole trap, was then added to a concentration of 3mM. After the circulation system stabilized, a 500W mercury lamp was preheated for 5 minutes. The photoreaction was then placed in the quartz reaction trap and allowed to proceed at room temperature with the circulating cooling water maintained at 20±1°C. At regular intervals, 3ml of the mixture was sampled for measurement. The mixture was then centrifuged at 10,000rpm for 10 minutes to separate the solid and liquid, and the supernatant was measured. The concentrations of nitrate, nitrite, and formate were measured using ion chromatography (Thermo Fisher, Dionex™ Aquion™), ammonium using UV spectrophotometry (Hash, DR6000), and total nitrogen was quantitatively analyzed using a total organic carbon analyzer (Shimadzu, TOC-L). Nitrogen was indirectly calculated from the total nitrogen and the total detected single element balance of the solution to obtain the nitrate removal rate and nitrogen conversion rate.

[0084] Figure 6 This is a graph showing the removal effect of 1 mM nitrate by the silver-copper ferrite-iron-based metal organic framework composite material in Test Example 1 of the present invention. The graph shows the change curves of total nitrogen, nitrate nitrogen, nitrite nitrogen and ammonia nitrogen concentration over time.

[0085] like Figure 6 As shown in the figure, in the process of removing nitrate, the silver-copper ferrite-iron-based metal organic framework composite material acts as a catalyst, and formic acid is adsorbed on the surface of the copper ferrite-iron-based metal organic framework material and recombines with the holes to produce carbon dioxide free radicals (·CO2 - ); Nitrate is adsorbed on the surface of copper ferrite-iron-based metal organic framework material and decomposed into intermediate product nitrite (NO2 - ) and nitrogen dioxide radicals (·NO2), etc. The main reaction pathway is that the intermediate product is ·CO2 - It is reduced to nitrogen, and a small amount of nitrite and ammonium ions are produced during the reaction. It has a high removal rate and a nitrogen conversion rate of more than 90%. In addition, the added hole capture agent formic acid is consumed as the reduction process ends, and no secondary pollution is generated.

[0086] <Test Example 2>

[0087] In this test example, the silver-copper ferrite-iron-based metal organic framework composite material (1wt% Ag / CuFe2O4 / MIL-100(Fe)) prepared in Example 1 was magnetically separated and recovered, with a recovery rate of between 91% and 97% each time. The recovered material was used for the catalytic reduction of 1mM nitrate pollutants. The specific test method was the same as that in Test Example 1.

[0088] Figure 7 This is a graph showing the effects of five cycles of catalytic reduction of 1 mM nitrate in Test Example 2 of the present invention.

[0089] like Figure 7 As shown, after 3 hours of catalytic reduction, the nitrate removal rates in the five tests were 97.6%, 90.1%, 83.6%, 75.9%, and 61.3%, respectively, and the nitrogen conversion rates were 99.7%, 95.4%, 96.8%, 92.5%, and 90.5%, all exceeding 90%. The above experiments demonstrate that the silver-copper ferrite-iron-based metal-organic framework composite material of the present invention is a magnetic material with excellent recovery performance, stable nitrate removal performance, and high nitrogen selectivity.

[0090] <Test Example 3>

[0091] In this test example, based on the same preparation conditions as in Example 1, only part of the weighed silver nitrate in step S5 was replaced, and by weighing different amounts of silver nitrate, the mass percentage of silver in the prepared silver-copper ferrite-iron metal organic framework material was 0.1wt%, 0.5wt% and 2wt% respectively.

[0092] Based on the same test method as in Test Example 1, silver-copper ferrite-iron metal organic framework composite materials with silver mass percentages of 0.1wt%, 0.5wt%, 1wt%, 2wt% were used to reduce 1mM nitrate to nitrogen respectively. Figure 8 The removal effect of 1mM nitrate by silver-copper ferrite-iron metal organic framework composite materials with different Ag contents in Test Example 3 of the present application.

[0093] As shown in Figure 8 With the increase of the mass percentage of silver, the removal rate of nitrate and the conversion rate of nitrogen of the silver-copper ferrite-iron metal organic framework material also increased greatly, and when the mass percentage of silver was 1wt% and 2wt%, higher removal rate of nitrate and conversion rate of nitrogen were obtained.

[0094] <TEST EXAMPLE 4>

[0095] In this test example, based on the same preparation conditions as in Example 1, only the mass ratio of the weighed copper ferrite material and iron metal organic framework material in step S3 was replaced, and by weighing different mass ratios of copper ferrite material and iron metal organic framework material, the mass ratio of copper ferrite material and iron metal organic framework material in the prepared silver-copper ferrite-iron metal organic framework material was 1:1, 1:3, 1:4 and 1:5.

[0096] Based on the same test method as in Test Example 1, silver-copper ferrite-iron metal organic framework composite materials with mass ratios of copper ferrite material and iron metal organic framework material of 1:1, 1:2, 1:3, 1:4 and 1:5 were used to reduce 1mM nitrate to nitrogen, and the test results were as follows:

[0097] After 3h of reduction reaction, the removal rates of 1mM nitrate by silver(1wt%)-copper ferrite-iron metal organic framework composite materials with mass ratios of 1:1, 1:2, 1:3, 1:4 and 1:5 were 88.2%, 95.4%, 84.9%, 80.1% and 77.5% respectively, and the nitrogen conversion rates all reached more than 90%.

[0098] <TEST EXAMPLE 5>

[0099] In this test example, the silver-copper ferrite-iron metal organic framework composite material prepared in Example 1 was applied to photocatalyst reduction of bromate, and the specific method was as follows:

[0100] 0.04g of silver-copper ferrite-iron metal organic framework composite material (mass ratio of CuFe2O4 and MIL-100(Fe) is 1:2, and the mass percentage of Ag is 1wt%) was added into a quartz reaction cell with 200ml of 0.1mM, 0.5mM, and 1mM bromate solution respectively, and stirred in the dark for 30min to reach adsorption equilibrium. After the circulation system was stabilized, the light reactor was opened, and the 100w mercury lamp was preheated for 5min before being placed in the quartz reaction cell for photoreaction. The circulating cooling water temperature was 20±1℃. Every certain time, 3ml of the mixture was taken for measurement, and the mixture was centrifuged at a speed of 10000rpm for 10min for solid-liquid separation, and the supernatant was taken for measurement. The concentrations of bromate, bromide and the like were quantitatively analyzed by ion chromatography (Thermo, DionexTMAquionTM), and the bromate removal rate was obtained.

[0101] Figure 9 Figure 1 is a silver-copper ferrite-iron metal organic framework composite material for different concentrations of bromate removal effect diagram in the test example 5 of the present application. The vertical coordinate C t / Co in the figure represents the change of bromate concentration with time.

[0102] As Figure 9 shown, in the removal of bromate, the silver-copper ferrite-iron metal organic framework composite material acts as a catalyst, and the bromate is adsorbed on the surface of the copper ferrite-iron metal organic framework material. The main reduction product of bromate is bromide, and the conversion rate of bromide obtained by detection is all above 97.9%.

[0103] <test example 6>

[0104] In this test example, the silver-copper ferrite-iron metal organic framework composite material prepared in example 1 was applied to the reduction of chlorite as a photocatalyst, and the specific method was as follows:

[0105] 0.04g of silver-copper ferrite-iron-based metal organic framework composite material (mass ratio of CuFe2O4 and MIL-100 (Fe) is 1:2, and the mass percentage of Ag is 1wt%) is respectively put into a quartz reaction tank with 200ml of 0.1mM, 0.2mM, 0.5mM, 1mM chlorite solution, and stirred in the dark for 30min to reach adsorption equilibrium. After the circulation system is stable, the light reactor is opened, and the quartz reaction tank is put into the light reactor after the 15w mercury lamp is preheated for 5min to carry out photoreaction, and the circulating cooling water temperature is 20±1℃. Every certain time, 3ml of the mixture is taken for measurement, the mixture is centrifuged at a speed of 10000rpm for 10min to carry out solid-liquid separation, and the supernatant is taken for measurement. The concentrations of chlorite, chloride and chlorate are quantitatively analyzed by ion chromatography (Thermo, Dionex TMAquionTM), and then the removal rate of chlorite is obtained.

[0106] Figure 10 Figure 1 is a silver-copper ferrite-iron-based metal organic framework composite material for different concentrations of chlorite removal effect diagram in the test example 6 of the present application. The vertical coordinate C t / C0 represents the change of chlorite concentration with time.

[0107] As Figure 10 shown, in the removal of chlorite, the silver-copper ferrite-iron-based metal organic framework composite material is used as a catalyst, chlorite is adsorbed on the surface of the copper ferrite-iron-based metal organic framework material, the main reduction product of chlorite is chloride ion, and a small amount of chlorate ion, and the chloride ion conversion rate is detected to be above 96.2%,

[0108] Effects of the embodiments

[0109] According to the embodiments 1-4, the copper ferrite material is synthesized by the improved solvothermal method, the uniformity of the complexing process is controlled by improving the pH value and the hydrothermal temperature, different additives are appropriately added, the particle morphology of the synthesized material can be effectively controlled, the crystal with uniform particle size is formed, the crystal structure is stabilized by keeping the hydrothermal time for 14h, the copper ferrite crystal obtained has good crystallization, and the particle size is 150-225nm.

[0110] According to the embodiments 1 and 5, the iron-based organic framework material is conveniently prepared by using the sol-gel method at room temperature, the particle size of the iron-based organic framework material prepared by improving the pH value and stirring conditions, i.e. pH value is 11.0 and stirring at room temperature for 24h, is 550-1050nm, the copper ferrite crystal is more uniformly distributed by using the iron-based metal framework compound as a skeleton, and the reduction active site is increased.

[0111] According to the embodiments 1, 6, the application adopts the ultrasonic method to combine the copper ferrite material (Ecb=-1.30eV, Evb=0.30eV) and the iron-based organic framework material (Ecb=-0.61eV, Evb=1.81eV) to form a heterostructure to constitute a new type of photocatalytic material, which promotes the separation of electrons and holes, improves the light quantum yield and catalytic performance.

[0112] According to the test examples 1, 4, 5 and 6, the silver-copper ferrite-iron-based metal organic framework composite material prepared by the application has a metal organic framework material as a skeleton and forms a heterojunction, and can efficiently and highly selectively remove nitrate in water by combining with the advanced reduction technology, and has a high removal rate for bromate and chlorite and other oxygen-containing acid salt pollutants, and controls the reaction path to increase the harmless products and reduce secondary pollution. Further, when the mass ratio of the copper ferrite material and the iron-based metal organic framework material is 1:2, a relatively optimal nitrate removal rate and nitrogen conversion rate can be obtained.

[0113] According to the test examples 2 and 3, the silver-copper ferrite-iron-based metal organic framework composite material prepared by the application has the characteristics of stability and repeated use, is convenient for magnetic recovery, has a high reusability, and the silver loading can further improve the nitrate removal rate and nitrogen conversion rate.

[0114] Therefore, the preparation method of the application has a simple process, and the raw materials are widely available, and the silver-copper ferrite-iron-based metal organic framework composite material prepared by the application has the characteristics of high catalytic efficiency, high nitrogen conversion rate, non-polluted product, low chemical reagent dosage, and is convenient for magnetic recovery, has a high reusability, and has a wide application prospect in the treatment of water plants containing nitrate, bromate and chlorite and other oxygen-containing acid salt pollutants.

[0115] The above embodiments are preferred cases of the application and do not limit the protection scope of the application.

Claims

1. A method for preparing a silver-copper ferrite-iron-based metal organic framework composite material, characterized in that: The following steps are involved: Step S1, weighing ferric nitrate and copper nitrate, placing them in a solvent and stirring until they are uniformly dissolved to obtain a mixed solution, adjusting the pH of the mixed solution, continuously stirring and dispersing to obtain a suspension, subjecting the suspension to a hydrothermal reaction to obtain a first mixture, separating, washing, drying, and grinding the first mixture to obtain a copper ferrite material; Step S2, mixing trimesic acid and sodium hydroxide solution, adjusting the pH, and then slowly stirring and ultrasonicating to obtain solution A, dissolving ferrous chloride in deionized water, slowly stirring to obtain solution B, dropwise adding solution A to solution B, adjusting the pH, and slowly stirring to obtain a second mixture, separating, washing, drying, and grinding the second mixture to obtain an iron-based organic framework material; Step S3, weighing the copper ferrite material and the iron-based organic framework material, dissolving them in ethanol and ultrasonically obtaining a third mixture, separating, washing, drying, and grinding the third mixture to obtain a copper ferrite-iron-based metal organic framework composite material, wherein the mass ratio of the copper ferrite material to the iron-based organic framework material is 1:1-5, dissolving the copper ferrite material and the iron-based organic framework material in ethanol and ultrasonically obtaining 2h-6h, and separating and washing the third mixture by washing with ethanol and deionized water, respectively, and centrifuging three times; Step S4, weighing the copper ferrite-iron-based metal-organic framework composite material into a quartz tube, adding silver nitrate, formic acid and deionized water, stirring evenly, and then irradiating with a mercury lamp to obtain a fourth mixture, and separating, washing, drying and grinding the fourth mixture to obtain a silver-copper ferrite-iron-based metal-organic framework composite material.

2. The method for preparing the silver-copper ferrite-iron-based metal organic framework composite material according to claim 1, characterized in that: in, In step S1, the solvent is deionized water, ethylene glycol or ethanol, When adjusting the pH of the mixed solution, sodium hydroxide was used to adjust the pH of the mixed solution to 9.0-11.0, and the mixture was stirred for 30 minutes to obtain a suspension. After adjusting the pH of the mixed solution, a modifier is added, and the modifier is PVP, citric acid or urea.

3. The method for preparing the silver-copper ferrite-iron-based metal organic framework composite material according to claim 1, characterized in that: in, In step S1, the suspension is subjected to the hydrothermal reaction in a polytetrafluoroethylene reactor at a temperature of 120° C. to 160° C. for 12 h to 20 h. When separating and washing the first mixture, the mixture was washed with ethanol and deionized water respectively and centrifuged three times.

4. The method for preparing the silver-copper ferrite-iron-based metal organic framework composite material according to claim 1, characterized in that: in, In step S2, the trimesic acid and the sodium hydroxide solution are mixed and stirred, and the pH is adjusted to 11.0, and the ultrasonic time is 2 hours.

5. The method for preparing the silver-copper ferrite-iron-based metal organic framework composite material according to claim 1, characterized in that: in, In step S2, after adding solution A dropwise to solution B, the pH is adjusted to 10.0-12.0, and then slowly stirred for 12-24 hours. When the second mixture is separated and washed, it is washed with ethanol and deionized water respectively and centrifuged three times.

6. The method for preparing the silver-copper ferrite-iron-based metal organic framework composite material according to claim 1, characterized in that: in, In step S4, the power of the mercury lamp is 500W and the irradiation time is 3h. When separating, washing, drying and grinding the fourth mixture, the fourth mixture is centrifuged, washed three times with water and ethanol, dried at 80° C. for 12 hours and then ground. The mass percentage of silver in the silver-copper ferrite-iron-based metal organic framework composite material is 0.1 wt % to 2 wt %.

7. A silver-copper ferrite-iron-based metal organic framework composite material, characterized in that: The silver-copper ferrite-iron-based metal organic framework composite material is prepared by the preparation method of any one of claims 1 to 6.

8. Use of the silver-copper ferrite-iron-based metal organic framework composite material as claimed in claim 7 in removing oxygen-containing salt pollutants in drinking water.

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