A basic high iron lanthanum manganate material and its preparation method and application

Abstract

The invention discloses a basic lanthanum high iron manganate material and its preparation method and application. Lanthanum salt, iron salt and manganese salt are dispersed in water, and a complexing agent is added to carry out complexing reaction to obtain a lanthanum-iron-manganese composite sol; an alkaline oxidizing mixed solution is added to the lanthanum-iron-manganese composite sol for oxidation to obtain a high iron manganate gel; the gel product is placed in a high pressure reactor for homogenization and heating, and then centrifuged, dried and calcined to obtain the target product. La(OH)Fe synthesized by the method x Mn 1‑x The surface of O4 material is rich in hydroxyl active groups and metal active sites, and has a high fluoride ion adsorption capacity; in addition, a layer of iron / manganese active filter membrane can be formed on the surface of the material. By utilizing the strong oxidizing properties of ferric acid and the self-catalytic effect of the active filter membrane, it can achieve catalytic oxidation and removal of pollutants such as iron and manganese while removing fluorine. It is a new type of high-efficiency water treatment agent that integrates oxidation and adsorption.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and particularly relates to a basic lanthanum ferromanganate material and a preparation method and application thereof. Background Art

[0002] Drinking water safety is an important livelihood issue. The problem of excessive trace toxic pollutants in drinking water in some rural areas of my country is becoming increasingly serious, and the current situation of drinking water safety is not optimistic. According to the current "Drinking Water Hygiene Standard (GB5749-2022)" (the concentration limits of fluoride, iron and manganese in drinking water are: F - <1.0mg / L, Fe 2+ <0.3mg / L, Mn 2+ <0.1mg / L), groundwater in most parts of my country contains excessive amounts of fluoride, iron, and manganese, making water treatment difficult and costly. Long-term drinking of drinking water with excessive amounts of fluoride, iron, and manganese can cause serious damage to human bones, kidneys, liver, and brain, and can even endanger life. Due to the characteristics of fluoride, iron, and manganese pollution, such as geographical dispersion, variable forms, unclear removal mechanisms, difficulty in treatment, and high costs, the current treatment technology foundation is generally weak, and it is impossible to achieve deep removal of fluoride, iron, and manganese in drinking water. It is urgent to develop efficient and low-cost treatment technologies.

[0003] At present, the main methods used for removing fluoride, iron and manganese from drinking water at home and abroad are: precipitation method (including chemical precipitation method and coagulation precipitation method), membrane separation technology (reverse osmosis and electrodialysis), contact oxidation method, adsorption method, etc. Compared with other technologies, adsorption technology is more mature, cheaper and simpler to operate. Therefore, adsorption is currently widely used and used as a technology for efficiently removing fluoride ions from water. Commonly used defluorination adsorption materials include natural minerals, metal oxides, biomass materials, etc. Due to their structural similarities, iron and manganese are usually removed together. Commonly used iron and manganese adsorption materials include manganese sand, zeolite, volcanic rock, biomass materials, activated carbon, silicon carbon, etc. However, there are few studies on adsorbents for the synergistic removal of fluoride, iron and manganese pollutants, and existing technologies cannot achieve efficient synergistic removal of fluoride, iron, manganese and other pollutants in water.

[0004] At present, the most widely used method for simultaneous defluorination and iron and manganese removal in groundwater is to use the autocatalytic reaction of iron and manganese to coat the surface of the adsorbent with iron, so that the Fe 2+ , Mn 2+ After catalytic oxidation, it accumulates on the adsorbent surface in the form of metal oxides, changing the surface properties of the adsorbent and making it 2+ , Mn 2+ While catalytic oxidation is being performed, the adsorbent is enhanced to -Therefore, when designing adsorption materials, it is necessary to consider the complex surface structure, containing a variety of active groups, and being able to provide adsorption sites that combine with fluorine, iron, and manganese ions in water, so as to achieve efficient and synergistic removal of fluorine, iron, manganese and other pollution in water. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the prior art that the efficient and coordinated removal of fluorine, iron and manganese in water cannot be achieved, the purpose of the present invention is to provide a method for preparing a basic lanthanum ferric manganate material. The material is rich in hydroxyl active groups and lanthanum active sites, and a layer of iron / manganese active filter membrane can be formed on the surface. The strong oxidizing property of ferric acid, the adsorption property of the active sites, and the self-catalytic effect of the active filter membrane can be used to achieve catalytic oxidation removal of pollutants such as iron and manganese while removing fluorine. The material is a new type of high-efficiency water treatment agent that integrates oxidation, adsorption, deturbidity removal, decolorization, and deodorization.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing basic lanthanum ferromanganate comprises the following steps:

[0008] Step 1: lanthanum salt, iron salt and manganese salt in different molar ratios are dispersed in pure water, and a complexing agent is added to carry out complexing reaction to obtain a lanthanum-iron-manganese composite sol;

[0009] Step 2: Mixing the ammonia solution and the sodium hypochlorite solution in proportion to obtain an alkaline oxidizing mixed solution;

[0010] Step 3, adding the mixed solution dropwise into the lanthanum-iron-manganese composite sol obtained in step 1, and oxidizing it to obtain high iron manganate gel;

[0011] Step 4: Place the gel product in a high-pressure reactor for homogenization and heating, and then obtain basic lanthanum ferromanganate with fully exposed active sites through centrifugation, drying and calcination.

[0012] As a preferred technical solution, in step 1, the lanthanum salt, iron salt, and manganese salt are at least one of the nitrates, sulfates, and chlorides of the respective metals. The lanthanum salt is a salt composed of lanthanide elements. When lanthanum is selected as the element in the lanthanum salt, the compound formula of the obtained product, basic lanthanum ferromanganate, is La(OH)Fe x Mn 1-x O4, wherein x is in the range of 0.25-0.75. The molar ratio of the lanthanum salt, the iron salt and the manganese salt is 1:x:(1-x), and further preferably, the molar ratio of the lanthanum salt, the iron salt and the manganese salt is 2:1:1, 2:1.5:0.5 or 2:0.5:1.5.

[0013] As a preferred technical solution, in step 1, the complexing agent is at least one of citric acid, glycine, hydroxy acid, tartaric acid, and acetylacetone.

[0014] As a preferred technical solution, in step 2, the mass fraction of the sodium hypochlorite solution is 5%-8%, and the ratio of ammonia water to the sodium hypochlorite solution is at least one of 1:1, 1:2, and 1:3.

[0015] As a preferred technical solution, in step 4, the heating temperature is 120-180°C and the time is 3-5h.

[0016] As a preferred technical solution, in step 4, the drying temperature is 60-80°C, the calcination temperature is 400-600°C, and the time is 1-2h.

[0017] Another object of the present invention is to provide La(OH)Fe x Mn 1-x O4 material, the La(OH)Fe x Mn 1-x The surface of O4 material is rich in hydroxyl active groups and metal active sites. A layer of iron / manganese active filter membrane can be formed on the surface. Both manganese and iron are in hexavalent state. By utilizing the strong oxidizing property of ferric acid, the adsorption property of active sites and the self-catalytic effect of the active filter membrane, it can achieve catalytic oxidation removal of pollutants such as iron and manganese while removing fluorine. It is a new type of high-efficiency water treatment agent that integrates oxidation and adsorption.

[0018] The third object of the present invention is to provide the La(OH)Fe x Mn 1-x The application of O4 material in the synergistic removal of fluoride, iron and manganese ions in water. This material can adsorb and remove fluoride ions with an initial concentration of about 3 mg / L in water to below 1 mg / L within 10 minutes, adsorb and remove iron ions with an initial concentration of about 3 mg / L to below 0.3 mg / L, and adsorb and remove manganese ions with an initial concentration of about 3 mg / L to below 0.1 mg / L, thus meeting the sanitary standards for drinking water.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) La(OH)Fe synthesized by the method of the present invention x Mn 1-xO4 material, its surface is rich in hydroxyl active groups and metal active sites, it has a very high adsorption affinity for fluoride ions, and can form a layer of iron / manganese active filter membrane on the surface. In practical applications, the iron active filter membrane first adsorbs ferrous ions in the water. The adsorbed ferrous ions are rapidly oxidized to trivalent iron under the catalytic action of the active filter membrane, and the catalyst is regenerated. The reaction product is the catalyst and participates in new catalytic reactions. The process of the iron active filter membrane contacting ferrous ions is a self-catalytic reaction process. The manganese active filter membrane can convert Mn in water into 2+ It is catalytically oxidized to MnO2 and adsorbed on the surface of the filter material, so that the filter membrane is renewed. This process is also a self-catalytic reaction. By utilizing the strong oxidizing property of ferric acid, the adsorption property of active sites, and the self-catalytic effect of the active filter membrane, it can achieve catalytic oxidation removal of pollutants such as iron and manganese while removing fluorine. It is a new type of high-efficiency water treatment agent that integrates oxidation and adsorption.

[0021] (2) La(OH)Fe synthesized by the present invention x Mn 1-x O4 material has greatly increased surface active groups, and can synergistically adsorb and remove fluorine, iron, and manganese ions with an initial concentration of about 3 mg / L in water within 10 minutes, reaching below the drinking water standard, overcoming the defect that conventional materials cannot remove fluorine, iron, and manganese ions at the same time;

[0022] (3) The synthesis method and process used in the present invention are simple and easy to operate, and are suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The La(OH)Fe prepared in Example 1 x Mn 1-x SEM morphology of O4 material;

[0024] Figure 2 The La(OH)Fe prepared in Example 1 x Mn 1-x O4 material has a synergistic removal effect on fluorine, iron and manganese ions. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0027] Example 1

[0028] A method for preparing basic lanthanum ferromanganate comprises the following steps:

[0029] Step 1: disperse lanthanum nitrate, iron nitrate and manganese nitrate in 500 mL of pure water at a molar ratio of 2:1:1 (64.98 g of lanthanum nitrate, 24.19 g of iron nitrate and 17.89 g of manganese nitrate), and add 19.21 g of citric acid for complexation reaction to obtain a lanthanum-iron-manganese composite sol;

[0030] Step 2: Mix 50 mL of aqueous ammonia and 100 mL of a 5% sodium hypochlorite solution to obtain an alkaline oxidizing mixed solution;

[0031] Step 3, adding the mixed solution dropwise into the sol obtained in step 1, and oxidizing it to obtain high iron manganate gel;

[0032] Step 4: Place the gel product in a high pressure reactor and heat at 160°C for 3 h, then centrifuge, dry, and calcine at 500°C for 1 h to obtain La(OH)Fe 0.5 Mn 0.5 O4 material.

[0033] Example 1 Synthesized La(OH)Fe 0.5 Mn 0.5 The morphology of O4 material was characterized by scanning electron microscopy. Figure 1 As shown, it can be seen that the prepared material is uniformly granular with an average particle size of about 200nm. Figure 2 When the dosage is 150 mg / L, it can synergistically adsorb and remove fluoride, iron and manganese ions with an initial concentration of about 3 mg / L in water, reaching below the drinking water standard, overcoming the defect that conventional materials cannot remove fluoride, iron and manganese ions at the same time.

[0034] Example 2

[0035] A method for preparing basic lanthanum ferromanganate comprises the following steps:

[0036] Step 1: disperse lanthanum sulfate, iron sulfate and manganese sulfate in 500 mL of pure water at a molar ratio of 2:1:1 (113.20 g of lanthanum sulfate, 39.99 g of iron sulfate and 15.10 g of manganese sulfate), and add 7.51 g of glycine for complexation reaction to obtain a lanthanum-iron-manganese composite sol;

[0037] Step 2: Mix 100 mL of aqueous ammonia and 100 mL of 5% sodium hypochlorite solution to obtain an alkaline oxidizing mixed solution;

[0038] Step 3, adding the mixed solution dropwise into the sol obtained in step 1, and oxidizing it to obtain high iron manganate gel;

[0039] Step 4: Place the gel product in a high pressure reactor and heat at 160°C for 3 h, then centrifuge, dry, and calcine at 500°C for 1 h to obtain La(OH)Fe 0.5 Mn 0.5 O4 material.

[0040] The La(OH)Fe synthesized in Example 2 0.5 Mn 0.5 O4 material, the adsorption experiment results show that when the dosage is 150mg / L, it can synergistically adsorb and remove fluorine, iron and manganese ions with an initial concentration of about 3mg / L in water, reaching below the drinking water standard, overcoming the defect that conventional materials cannot remove fluorine, iron and manganese ions at the same time.

[0041] Example 3

[0042] A method for preparing basic lanthanum ferromanganate comprises the following steps:

[0043] Step 1: disperse lanthanum chloride, ferric chloride and manganese chloride in 500 mL of pure water at a molar ratio of 2:1:1 (49.06 g of lanthanum chloride, 16.22 g of ferric chloride and 12.58 g of manganese chloride), and add 10.01 g of acetylacetone for complexation reaction to obtain a lanthanum-iron-manganese composite sol;

[0044] Step 2: Mix 100 mL of aqueous ammonia and 100 mL of 6% sodium hypochlorite solution to obtain an alkaline oxidizing mixed solution;

[0045] Step 3, adding the mixed solution dropwise into the sol obtained in step 1, and oxidizing it to obtain high iron manganate gel;

[0046] Step 4: Place the gel product in a high pressure reactor and heat at 120°C for 5 h, then centrifuge, dry, and calcine at 500°C for 1 h to obtain La(OH)Fe 0.5 Mn 0.5 O4 material.

[0047] The La(OH)Fe synthesized in Example 3 0.5 Mn 0.5 O4 material, the adsorption experiment results show that when the dosage is 150mg / L, it can synergistically adsorb and remove fluorine, iron and manganese ions with an initial concentration of about 3mg / L in water, reaching below the drinking water standard, overcoming the defect that conventional materials cannot remove fluorine, iron and manganese ions at the same time.

[0048] Example 4

[0049] A method for preparing basic lanthanum ferromanganate comprises the following steps:

[0050] Step 1: disperse lanthanum chloride, ferric chloride and manganese chloride in 500 mL of pure water at a molar ratio of 2:1.5:0.5 (49.06 g of lanthanum chloride, 24.33 g of ferric chloride and 6.29 g of manganese chloride), and add 15.01 g of tartaric acid for complexation reaction to obtain a lanthanum-iron-manganese composite sol;

[0051] Step 2: Mix 50 mL of aqueous ammonia and 100 mL of 8% sodium hypochlorite solution to obtain an alkaline oxidizing mixed solution;

[0052] Step 3, adding the mixed solution dropwise into the sol obtained in step 1, and oxidizing it to obtain high iron manganate gel;

[0053] Step 4: Place the gel product in a high pressure reactor and heat at 150°C for 5 h, then centrifuge, dry, and calcine at 200°C for 3 h to obtain La(OH)Fe 0.75 Mn 0.25 O4 material.

[0054] The La(OH)Fe synthesized in Example 4 0.75 Mn 0.25 O4 material, the adsorption experiment results show that when the dosage is 150mg / L, it can synergistically adsorb and remove fluorine, iron and manganese ions with an initial concentration of about 3mg / L in water, reaching below the drinking water standard, overcoming the defect that conventional materials cannot remove fluorine, iron and manganese ions at the same time.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing basic lanthanum ferromanganate, characterized in that: The following steps are involved: Step 1: dispersing lanthanum salt, iron salt and manganese salt in water, adding a complexing agent for complexing reaction to obtain a lanthanum-iron-manganese composite sol; the molar ratio of the lanthanum salt, iron salt and manganese salt is 1:x:(1-x), wherein the value of x ranges from 0.25 to 0.75; Step 2: Mixing an ammonia solution and a sodium hypochlorite solution to obtain an alkaline oxidizing mixed solution; Step 3, adding the alkaline oxidation mixture dropwise into the lanthanum-iron-manganese composite sol obtained in step 1 to oxidize to obtain high iron manganate gel; Step 4: placing the high iron manganate gel in a high pressure reactor for homogenization and heating, and then centrifuging, drying and calcining to obtain basic high iron manganate lanthanum; the heating temperature is 120-180°C; the calcination temperature is 400-600°C.

2. The preparation method according to claim 1, characterized in that: In step 1, the lanthanum salt, iron salt and manganese salt are at least one of the nitrate, sulfate and chloride of the respective metals.

3. The preparation method according to claim 1, characterized in that: In step 1, the complexing agent is at least one of citric acid, glycine, hydroxy acid, tartaric acid, and acetylacetone.

4. The preparation method according to claim 1, characterized in that: In step 2, the mass fraction of the sodium hypochlorite solution is 5%-8%.

5. The preparation method according to claim 1, characterized in that: In step 4, the heating time is 3-5h.

6. The preparation method according to claim 1, characterized in that: In step 4, the drying temperature is 60-80° C. and the calcination time is 1-2 h.

7. Basic lanthanum ferromanganate obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the basic lanthanum ferromanganate as claimed in claim 7 in removing fluorine, iron and manganese ions from water.

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