CN114700032A

CN114700032A - Cryptomelane whisker and preparation and application thereof

Info

Publication number: CN114700032A
Application number: CN202210263263.6A
Authority: CN
Inventors: 罗骏; 莽昌烨; 李光辉; 饶明军; 彭志伟; 蒋昊; 张鑫; 姜涛
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2022-07-05
Anticipated expiration: 2042-03-17
Also published as: CN114700032B

Abstract

The invention belongs to the field of pollutant treatment, and particularly discloses a preparation method of cryptomelane whiskers, which comprises the steps of carrying out a first-stage reaction on a divalent manganese source and a high-manganese acid source A, then supplementing a high-manganese acid source B to carry out a second-stage reaction, and then carrying out hydrothermal crystallization treatment to obtain cryptomelane whiskers; wherein the molar ratio of the high manganese acid source A to the bivalent manganese source is 0.5-2: 1; the temperature of the first stage reaction is 30-50 ℃; the molar ratio of the high manganese acid source B to the divalent manganese source is 2-8: 1; the temperature of the second stage reaction is 40-95 ℃. The invention also provides a whisker material prepared by the preparation method and application thereof in heavy metal adsorption. The method can obtain the material with high crystallinity, high phase purity, excellent heavy metal adsorption performance and excellent flue gas denitration performance.

Description

Cryptomelane whisker and preparation and application thereof

Technical Field

The invention belongs to the field of pollution treatment, and particularly relates to the fields of heavy metal pollution adsorption materials and catalytic reduction of factory waste gas.

Technical Field

Since the 21 st century, the world has faced serious problems with population, resources, environment, and the like. The continuous and rapid development of the modern society can not avoid the use of heavy metal in large quantity, so that a large quantity of heavy metal ions or related pollutants enter a water body, and great threat is caused to the surrounding environment and the health of human beings. The pollution of the water body is one of the major environmental problems facing human beings, and heavy metal ions in the water body can be enriched in aquatic organisms, so that the organs and tissues of the organisms are greatly damaged. In addition, if the heavy metal ions entering the water body can not be timely and effectively recovered, the method is not only a waste of resources, but also can greatly pollute a clean water source. Therefore, how to rapidly and effectively prevent heavy metal pollution and synchronously recycle heavy metal ions is one of the important problems in various countries and regions in the world.

Heavy metals have different definitions in different disciplines, with the physical index density being greater than 4.5g/cm³The metal of (a); chemical refers to metals having an atomic number greater than 20; toxicology broadly refers to metals having toxicity; in the environmental science, the major elements which are not biodegradable and have biological toxicity include metals such As cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), nickel (Ni), zinc (Zn), cobalt (Co), tin (Sn), and the like, and metalloids such As arsenic (As). The heavy metal ions in the water body have long-term persistence and accumulationThe characteristics of tiredness: on one hand, heavy metals are difficult to biodegrade, but change in valence and compound types can occur, and certain heavy metals can be converted into a form with higher toxicity even under the action of microorganisms after entering a water body; on the other hand, heavy metals can be enriched in organisms and enter human bodies through food chains, and when heavy metal ions in the human bodies are enriched to a certain amount, various diseases can occur in the human bodies.

At present, the heavy metal ion pollution in water bodies is divided into three important classes, namely a physical chemical method, a chemical method and a biological method. Each method has its advantages and disadvantages. Among them, the adsorption method has advantages of easy operation, simple equipment, high selectivity, etc., and is favored by many researchers.

Cryptomelane type manganese dioxide (OMS-2) has 2 x 2 pore channel structure composed of MnO₆The double-chain structure formed by the regular octahedron has unique physicochemical properties superior to those of similar materials. OMS-2 is a porous manganese oxide with a chemical composition of KMn₈O₁₆In which K is⁺The ions are located in one dimension of the pore canal and play a role in supporting the structure and balancing the charges. Mn exists in a framework of OMS-2 in a form of +2, +3 and +4, and a large amount of unsaturated coordinated Mn manganese ions exist in an exposed crystal face (110), so that conditions are created for adsorption of other heavy metal ions. Furthermore, K⁺The ions can exchange with external positively charged ions, so that the adsorption capacity to other heavy metal ions is greatly improved.

At present, the preparation of cryptomelane type manganese dioxide (OMS-2) requires the combination of a wet process and a pyrogenic process, the combination of various devices and the like, however, the crystallization degree, the phase purity and the morphology uniformity of a product prepared by the existing preparation method are not ideal, and the application performance such as the pollutant treatment capacity needs to be improved.

Disclosure of Invention

The first purpose of the invention is to provide a preparation method of cryptomelane type manganese dioxide, which is low in cost and simple in operation.

The second purpose of the invention is to provide the novel cryptomelane whisker prepared by the preparation method.

The third purpose of the invention is to provide the application of the cryptomelane prepared by the preparation method in pollutant treatment, such as treatment of heavy metal polluted water bodies, removal of harmful substances in flue gas and the like.

A preparation method of cryptomelane whiskers comprises the steps of carrying out a first-stage reaction on a divalent manganese source and a high manganese acid source A, then supplementing a high manganese acid source B to carry out a second-stage reaction, and then carrying out hydrothermal crystallization treatment to obtain cryptomelane whiskers;

wherein the molar ratio of the high manganese acid source A to the bivalent manganese source is 0.5-2: 1; the temperature of the first stage reaction is 30-50 ℃;

the molar ratio of the high manganese acid source B to the bivalent manganese source is 2-8: 1; the temperature of the second stage reaction is 40-95 ℃.

The invention innovatively discovers that a divalent manganese source and a high manganese acid source A are subjected to a first-stage reaction in advance, then a high manganese acid source B is supplemented to perform a second-stage reaction, and then the temperature is continuously increased to perform a hydrothermal crystallization third-stage reaction.

The research of the invention finds that the step-by-step three-section reaction idea of permanganate, the adding proportion in the reaction idea and the joint cooperative control of the reaction temperature of each section are the keys for regulating and controlling the crystallinity, phase and crystal whisker morphology of the product and improving the adsorption performance of heavy metal ions.

In the invention, the divalent manganese source can ionize Mn²⁺Water-soluble substance (c): preferably at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate, even manganese ore leachate. The divalent manganese source may be a commercial chemical feedstock or may be derived from a mineral smelting product (e.g. a leach solution).

Preferably, the solvent for the first stage reaction is water, or a water-organic solvent mixture, and the organic solvent is a water-miscible solvent, such as C1-C4 alcohol, acetone, THF, etc.

In the invention, a bivalent manganese source solution can be used as a base solution, a high manganese acid source A is added in advance to perform a first-stage reaction, a high manganese acid source B is supplemented to a first-stage reaction system to perform a second-stage reaction, the second-stage reaction system is placed in a closed pressure-resistant container to perform hydrothermal crystallization treatment, and the cryptomelane whiskers are obtained through solid-liquid separation after the hydrothermal crystallization treatment.

Preferably, in the initial solution system of the first stage reaction, Mn²⁺The molar concentration of (A) is 0.1-4M; preferably 0.5-4M; more preferably 0.5 to 2M.

The permanganate source A and the permanganate source B can ionize MnO₄ ^-The water-soluble salt of (2) is preferably at least one of potassium permanganate, sodium permanganate, and magnesium permanganate. Cations in the permanganate source A and the permanganate source B can be potassium, sodium and other cations, so that cryptomelane with corresponding interlayer cations can be prepared.

The research of the invention finds that the phase purity and the crystal whisker morphology of the target product can be further improved in a synergistic manner by controlling the material proportion and the temperature in the first stage of reaction, and the improvement of the product performance is facilitated.

In the present invention, the high manganese acid source A may be added in the form of a solid or an aqueous solution, and when it is added in the form of an aqueous solution, the concentration thereof may be 0.2 to 0.6M.

Preferably, the molar ratio of the high manganese acid source A (calculated as MnO 4-) to the divalent manganese source is 0.8-1.2: 1; more preferably 0.8 to 1: 1. It was found that, with the preferred parameters, the crystallinity, the phase and the heavy metal adsorption properties of the product obtained can be surprisingly further synergistically improved.

Preferably, in the step (1), the stirring speed in the first stage reaction process is 150-300 r/min.

Preferably, in the step (1), the reaction temperature in the first stage of the reaction process is 30-40 ℃, and more preferably 35-40 ℃.

In the step (1), the reaction time of the first stage reaction process can be adjusted according to the preparation requirement, and in consideration of the preparation efficiency, the reaction time of the first stage reaction process can be 0.5-2 h, and is further preferably 0.5-1 h.

According to the invention, the permanganate source B is added into the first system, and the mixture is stirred at a certain temperature for the second stage reaction, and researches show that the strict control of the reaction temperature of the second stage reaction and the addition of the permanganate source B is beneficial to the cooperative control of the crystallinity, phase and crystal whisker morphology of the product, and the cooperative improvement of the adsorption performance of the prepared product on heavy metal ions is facilitated.

In the invention, the high manganese acid source B can be added in the form of solid or aqueous solution, and when the high manganese acid source B is added in the form of aqueous solution, the concentration of the high manganese acid source B can be 0.1-0.6M; preferably 0.3 to 0.4M.

Preferably, the molar ratio of the high manganese acid source B to the divalent manganese source is 4-6: 1. It was found that, with the preferred parameters, the crystallinity, the phase and the heavy metal adsorption properties of the product obtained can be surprisingly further synergistically improved.

Preferably, the stirring speed of the second stage reaction is 150 to 300 r/min.

Preferably, the temperature of the second stage reaction is 60 to 80 ℃, and more preferably 70 to 80 ℃. It was found that, with the preferred parameters, it is possible to further synergistically improve the heavy metal adsorption properties of the products obtained.

In the invention, the time of the second-stage reaction can be adjusted as required, and in consideration of the preparation efficiency, the time of the second-stage reaction can be 0.2-2 h; further, the time period may be 0.5 to 1 hour.

In the invention, the mixed solution is transferred into a high-temperature-resistant and high-pressure-resistant container, the container is sealed, the temperature is raised for carrying out the third-stage reaction, and the crystallinity, the phase and the morphology of the product are further improved by controlling the reaction temperature of the third stage, so that the material with excellent heavy metal ion adsorption performance is obtained.

Preferably, the reaction temperature in the second stage is 100 to 260 ℃, more preferably 120 to 260 ℃, and still more preferably 200 to 240 ℃. It was found that, with the preferred parameters, the crystallinity, the phase and the heavy metal adsorption properties of the product obtained can be surprisingly further synergistically improved.

In the present invention, the time for the hydrothermal crystallization can be adjusted as needed, for example, in consideration of the preparation effect, the crystallization time is, for example, greater than or equal to 8 hours, preferably 12 to 36 hours, and more preferably 20 to 24 hours.

In the invention, after hydrothermal crystallization, solid-liquid separation is carried out on the product, and the product is obtained after washing and drying.

The invention discloses a preparation method of a preferable cryptomelane whisker, which comprises the following steps:

step (1): dropwise adding a high manganese acid source A aqueous solution with a certain concentration into a bivalent manganese source aqueous solution under a heating condition, and stirring for a certain time to perform a first-stage reaction; wherein the molar ratio of the high manganese acid source A to the bivalent manganese source is 0.5-2: 1;

step (2): adding a high manganese acid source B aqueous solution with a certain concentration into the solution system of the first reaction under the heating condition, stirring for a period of time to perform a second stage reaction, then transferring the mixed solution into a sealed container, heating to perform a third stage reaction, and separating to obtain a whisker-shaped cryptomelane product after the reaction is finished;

the molar ratio of the high manganese acid source B to the bivalent manganese source is 2-8: 1;

the reaction temperature of the first stage is 30-50 ℃, the reaction temperature of the second stage is 40-95 ℃, and the reaction temperature of the third stage is 100-260 ℃.

The invention relates to a more preferable preparation method of cryptomelane whiskers, which comprises the following steps:

(1) to the Mn obtained above²⁺Aqueous potassium permanganate solution (MnO 4-relative to Mn added) was added dropwise to the aqueous solution²⁺The molar ratio of (1) to (0.8-1.2), stirring for 0.5-1 h at 30-50 ℃, and carrying out a first-stage reaction to obtain a first reaction solution;

(2) continuously dripping potassium permanganate solution (MnO 4-relative to Mn in the solution) into the mixed solution²⁺At a molar ratio of 4-6: 1), stirring and reacting for 0.5-1 h at a reaction temperature of 70-80 ℃, and performing a second stageCarrying out sectional reaction to obtain suspension;

(3) transferring the suspension into a high-temperature-resistant and high-pressure-resistant container, sealing the reactor, and carrying out crystallization reaction at 200-240 ℃ for 20-24 hours;

(4) washing the solution to be neutral by using absolute ethyl alcohol and deionized water, performing suction filtration by using a vacuum pump, drying at the temperature of 60-120 ℃, and grinding to obtain cryptomelane whisker powder.

The invention also provides the porous cryptomelane prepared by the preparation method, and cryptomelane whiskers are staggered to form a porous material.

The invention also provides application of the cryptomelane whiskers obtained by the preparation method as a pollutant treatment material.

Preferred applications are for adsorption materials for heavy metal or metalloid contaminants;

preferably, an adsorbent material for heavy metal or metalloid contaminants in a body of water;

preferably, the heavy metal and metalloid pollutants are at least one of cadmium, chromium, mercury, lead, nickel, zinc, cobalt, tin, arsenic.

According to another application scheme of the invention, the prepared cryptomelane whiskers are used as an adsorption material for harmful flue gas. The harmful flue gas is nitrogen oxide, for example. The nitrogen oxides are, for example, NO₂And the like nitrogen oxide contaminants. The research of the invention finds that the cryptomelane whisker prepared from the cryptomelane has good heavy metal adsorption performance and also has excellent denitration performance.

Advantageous effects

1. The invention provides a permanganate three-stage reaction idea, and further discovers that based on the three-stage reaction idea, a synergistic reaction can be realized by further matching with the common control of conditions such as material proportion, reaction temperature, reaction time and the like, and the improvement of the properties such as cryptomelane phase purity, whisker morphology, heavy metal adsorption, denitration and the like is facilitated.

2. The cryptomelane whisker for efficiently adsorbing heavy metal ions in wastewater prepared by the invention has the advantages of simple preparation process, low cost, no need of adding any surfactant or modifier, and environmental friendliness. The cryptomelane prepared by the method has rich holes and good stability, and can have important application value in the fields of adsorption, wastewater, waste gas treatment and the like.

Drawings

FIG. 1 is an X-ray diffraction and SEM image of cryptomelane whiskers produced in example 1;

FIG. 2 is a scanning electron microscope photograph of the product made in A, B and group C of example 2;

FIG. 3X-ray diffraction pattern of panel C of example 3;

FIG. 4 is an SEM image of group C products of example 4;

FIG. 5 is an SEM image of group C products of example 5;

FIG. 6 is an SEM image of the products of group A and group C of example 6;

FIG. 7 is an SEM image of group A products of example 1;

FIG. 8 is an XRD pattern of the product obtained in comparative example 1;

FIG. 9 is a plot of degraded NOx versus temperature for the product of example 9 using example 1.

The specific implementation mode is as follows:

the method for recording the adsorption step of the heavy metal ions in the water and the data determination method comprises the following steps:

the adsorbed heavy metal ions are represented by lead ions and are prepared by diluting corresponding lead nitrate (AR), the pH value of the solution is regulated and controlled by adding dilute nitric acid, and the prepared cryptomelane sample is subjected to a heavy metal ion removal test in a single lead ion solution. The initial concentration of the lead ion solution is 100 +/-5 mg/L, a certain amount of 0.2g/L of adsorbent is taken and put into a 250mL conical flask, the adsorbent is added, the mixture is shaken at the rotating speed of 250rpm for 24h at room temperature and sampled at different times, the adsorbent and the lead ion solution in the mixed solution are separated by a 0.45 mu m filter membrane, and the removal rate (R) and the adsorption capacity (Q) are calculated.

R＝(C₀-C₁)/C₀*100％

Q＝(C₀-C₁)V/m

Wherein C is₀Is the initial concentration (mg/L), C, of the heavy metal ion solution₁Is the residual concentration (mg/L) of heavy metal ions after the adsorption test, V is the volume (L) of the solution, and m is the mass (g) of the adsorbent added.

The room temperature in the invention is, for example, 20 to 35 ℃.

Example 1

(1) Preparing 0.2M manganese sulfate solution for later use;

(2) dropwise adding 0.4M potassium permanganate solution (the dropwise adding speed is 0.01mol/min, and the dropwise adding molar weight is 0.2 mol; namely, the molar ratio of potassium permanganate to manganese sulfate is 1:1) into the prepared manganese sulfate aqueous solution (1L), stirring at 40 ℃ (the stirring speed is 180r/min), and carrying out first-stage reaction for 30min to obtain first-stage reaction liquid;

(3) continuously adding 0.3M potassium permanganate solution (the added molar weight is 0.8mol, namely the molar ratio of potassium permanganate to manganese sulfate is 4: 1; the dropping speed is the same as that in the step (2)) into the first-stage reaction solution, stirring for 60min at 80 ℃, and carrying out second-stage reaction to obtain suspension which is second-stage reaction solution;

(4) transferring the second-stage reaction liquid into a high-temperature-resistant and high-pressure-resistant reactor, sealing the reactor, heating to 200 ℃, and carrying out a third-stage reaction for 20 hours;

(5) washing with absolute ethyl alcohol and deionized water to neutrality, vacuum-filtering with a vacuum pump, drying at 80 deg.C, and grinding to obtain cryptomelane powder.

The X-ray diffraction spectrum of the porous cryptomelane material with the function of efficiently adsorbing heavy metal ions in wastewater prepared by the embodiment is shown in the attached figure 1A, and the scanning electron microscope picture is shown in the attached figure 1B.

The cryptomelane whisker material obtained in the embodiment has good adsorption performance, and when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the adsorbent to 100mg/L lead ion solution reaches 460mg/g within 10 minutes, and the removal rate reaches 92%.

Example 2

Compared with example 1, the difference is only that of the regulation step (2)Potassium permanganate to Mn²⁺Adding the following components in a molar ratio: (A) the method comprises the following steps Potassium permanganate to Mn²⁺The adding molar ratio is 0.8; (B) the method comprises the following steps Potassium permanganate relative to Mn²⁺The adding molar ratio is 0.2; (C) the method comprises the following steps Potassium permanganate relative to Mn²⁺Adding the mixture according to a molar ratio of 3; (D) the method comprises the following steps Potassium permanganate relative to Mn²⁺The adding molar ratio is 0.5; (E) the method comprises the following steps Potassium permanganate relative to Mn²⁺The adding molar ratio is 2. The other operations and parameters were the same as in example 1.

The product obtained in case of group A is shown in FIG. 2A, and whisker morphology product is obtained, while group B and C do not obtain whisker product because the ratio is not controlled within the range required by the present invention (SEM images are shown in FIG. 2B and FIG. 2C, respectively)

Adsorption experiments were performed on each set of products, with the results:

(A) group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of 100mg/L lead ion solution in 10 minutes reaches 420mg/g, and the removal rate reaches 84%.

(B) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the 100mg/L lead ion solution reaches 164mg/g in 10 minutes, and the removal rate reaches 33%.

(C) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 105mg/g, and the removal rate reaches 21%.

(D) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 295mg/g, and the removal rate reaches 59%.

(E) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 300mg/g, and the removal rate reaches 60%.

Example 3

Compared with the example 1, the difference is only that the temperatures of the first stage reaction stage of the step (2) are respectively as follows:

A：30℃；B：50℃；C：25℃；

the A and B groups gave products with similar phases and morphologies as in example 1, whereas the C group did not give the pure phase of the target product, as the XRD is shown in FIG. 3. The obtained sample is birnessite and cryptomelane commensal.

The adsorption performance was measured by the method of example 1, and the results were:

group A: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 410mg/g, and the removal rate reaches 82%.

Group B: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 390mg/g, and the removal rate reaches 78%.

Group C: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 240mg/g, and the removal rate reaches 48 percent.

Example 4

The only difference compared with example 1 is that the potassium permanganate in step (3) is regulated to the initially added Mn in the first step²⁺The molar ratio of (A) to (B) is respectively as follows: (A) the method comprises the following steps Potassium permanganate relative to Mn²⁺Adding the mixture according to the molar ratio of 1; (B) the method comprises the following steps Potassium permanganate to Mn²⁺The adding molar ratio is 9.5; (C) the method comprises the following steps Potassium permanganate relative to Mn²⁺Adding the mixture according to a molar ratio of 6; (D) the method comprises the following steps Potassium permanganate relative to Mn²⁺Adding the mixture according to the molar ratio of 2; (E) the method comprises the following steps Potassium permanganate relative to Mn²⁺Adding the mixture according to the molar ratio of 8;

groups C-E yielded cryptomelane phase products of similar morphology, e.g., SEM images of group C are shown in fig. 4.

group A: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 40mg/g, and the removal rate reaches 8%.

Group B: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 220mg/g, and the removal rate reaches 44%.

Group C: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 490mg/g, and the removal rate reaches 98%.

Group D: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 340mg/g, and the removal rate reaches 68 percent.

Group E: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 365mg/g, and the removal rate reaches 73%.

Example 5

Compared with the example 1, the difference is only that the reaction temperature of the step (3) is regulated and controlled as follows: (A) the method comprises the following steps 40 ℃; (B) the method comprises the following steps 60 ℃; (C) the method comprises the following steps 25 ℃; (D) the method comprises the following steps 70 ℃; (E)95 ℃;

A. b, D and E gave pure cryptomelane phase products of similar morphology to example 1, however, group C did not give the target phase product, as shown in FIG. 5 by XRD, which is a birnessite and cryptomelane intergrowth.

group A: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 310mg/g, and the removal rate reaches 62%.

Group B: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity to 100mg/L lead ion solution in 10 minutes reaches 355mg/g, and the removal rate reaches 71%.

Group C: when the adsorbent is used in an amount of 0.2g/L, the adsorption amount of 100mg/L lead ion solution reaches 280mg/g in 10 minutes, and the removal rate reaches 56%.

Group D: when the adsorbent is used in an amount of 0.2g/L, the removal rate of 100mg/L of lead ions in 10 minutes reaches 87%.

Group E: when the adsorbent is used in an amount of 0.2g/L, the removal rate of 100mg/L of lead ions reaches 76% in 10 minutes.

Example 6

Compared with the example 1, the difference is only that the temperature of the hydrothermal crystallization in the step (4) is regulated and controlled as follows:

(A)：120℃；(B)：260℃；(C)：80℃；(D)：240℃；

the A group and B, D group obtained the product with similar appearance and phase as example 1, and the scanning electron microscope picture of the material prepared by the A group shown in figure 6A gave the target product. However, group C did not yield the target product, SEM see fig. 6B:

(A) group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the adsorbent to 100mg/L lead ion solution in 10 minutes reaches 305mg/g, and the removal rate reaches 61%.

(B) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the adsorbent to 100mg/L lead ion solution in 10 minutes reaches 285mg/g, and the removal rate reaches 57%.

(C) Group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the adsorbent to 100mg/L lead ion solution in 10 minutes reaches 140mg/g, and the removal rate reaches 28 percent.

(D) Group (2): when the dosage of the adsorbent is 0.2g/L, the removal rate of 100mg/L lead ions in 10 minutes reaches 89%.

Example 7

Compared with the example 1, the difference is only that the crystallization time in the step (4) is regulated and controlled as follows: a, crystallizing time is 12 hours; b, crystallization time is 36 h;

A. group B gave a similar product to example 1, as for group A see FIG. 7.

(A) group (2): when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the 100mg/L lead ion solution reaches 340mg/g in 10 minutes, and the removal rate reaches 68 percent.

(B) Group (2): when the dosage of the adsorbent is 0.2g/L, the removal rate of 100mg/L lead ions in 10 minutes reaches 89%.

Example 8

Compared with example 1, the difference is only that the time of the first reaction and the second reaction is regulated, wherein the treatment time of the step (2) is 1h, and the treatment time of the step (3) is 0.5 h. A similar product to that of example 1 was obtained, and further performance measurement was performed by the method of example 1, with the results that: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of the adsorbent to 100mg/L lead ion solution reaches 430mg/g within 10 minutes, and the removal rate reaches 86%.

Comparative example 1

The difference from example 1 is that the hydrothermal crystallization treatment described in the third stage is directly performed by mixing the raw materials in the same ratio without using the three-stage reaction, and the temperature and time of crystallization are the same as those of example 1.

The X-ray diffraction spectrum of this case is shown in fig. 8, and it can be seen that the sample obtained without three-stage reaction is birnessite instead of cryptomelane, which indicates that the three-stage reaction is very necessary for cryptomelane generation.

The performance measurement was performed by the method of example 1, and the result was that when the amount of the adsorbent was 0.2g/L, the amount of the adsorbent adsorbed to 100mg/L of the lead ion solution reached 265mg/g in 10 minutes, and the removal rate reached 53%.

Example 9

The difference compared to example 1 is only that the product of the synthesis is used for the NH of the nitrogen oxides₃-SCR reduction.

NH₃-SCR test method:

diameter of the reactor: 8mm, length: 460 mm. The middle of the reaction tube was filled with about 200mg of a catalyst (200 mesh), and the remaining portion was filled with glass beads. The reactor temperature was monitored by a K-type thermocouple, the reaction temperature was controlled at 100 ℃ and 300 ℃ and SCR activity tests were performed every 50 ℃. The reaction feed gas was composed of 500ppm NO, 500ppm NH₃5% of O₂，N₂Is the balance gas. The gas composition was tested using a KANE9506 model gas analyzer. The flow of each path of gas is regulated by adopting a gas mass flow meter, and the gas volume space velocity is controlled to be 30000h^-1. Calculating NO by the following formula_xConversion ratio of (2): NO_xConversion (%) ═ NO_xletin－NO_xoutlet)÷NO_xinlet×100％

The curve of the change of the nitrogen oxide conversion rate along with the temperature in the case is shown in figure 9, and the result shows that the nitrogen oxide conversion rate is 33.8% when the temperature is 100 ℃; the nitrogen oxidation conversion rate is 65.4% when the temperature is 150 ℃; the nitrogen oxidation conversion rate is 93.7% when the temperature is 200 ℃; the nitrogen oxidation conversion rate is 93.4% when the temperature is 250 ℃; the nitrogen oxidation conversion was 82.4% at a temperature of 300 ℃. Therefore, the material has excellent denitration effect, and particularly can obtain better denitration effect at the temperature of more than or equal to 175 ℃, particularly at the temperature of 200-400 ℃, preferably at the temperature of 200-300 ℃, and further preferably at the temperature of 200-250 ℃.

Claims

1. A preparation method of cryptomelane whiskers is characterized in that a bivalent manganese source and a high manganese acid source A are subjected to a first stage reaction, then a high manganese acid source B is supplemented to perform a second stage reaction, and then hydrothermal crystallization treatment is performed to prepare cryptomelane whiskers;

2. The method of preparing cryptomelane whiskers of claim 1, wherein the divalent manganese source is capable of ionizing Mn² ⁺The water-soluble compound of (1); preferably at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate, or manganese ore leachate;

preferably, the solvent of the first stage reaction is water or a mixed solvent of water and an organic solvent, and the organic solvent is a solvent miscible with water;

preferably, in the initial solution system of the first stage reaction, Mn²⁺The molar concentration of (A) is 0.1-4M.

3. The method for preparing cryptomelane whiskers as claimed in claim 1, wherein the permanganate source A and the permanganate source B are capable of ionizing to form MnO₄ ^-The water-soluble salt of (2) is preferably at least one of potassium permanganate, sodium permanganate and magnesium permanganate.

4. The method for preparing cryptomelane whiskers as claimed in claim 1, wherein in the first stage of reaction, the molar ratio of the permanganate source A to the divalent manganese source is 0.8-1.2: 1;

preferably, the time of the first stage reaction is 0.5-2 h, preferably 0.5-1 h.

5. The preparation method of cryptomelane whiskers as claimed in claim 1, wherein the molar ratio of the high manganese acid source B to the divalent manganese source is 4-6: 1;

preferably, the time of the second stage reaction is 0.2-2 h.

6. The method for preparing cryptomelane whiskers as claimed in claim 1, wherein the temperature of the hydrothermal crystallization treatment is greater than or equal to 100 ℃, preferably 100-260 ℃.

7. The preparation method of cryptomelane whiskers as claimed in claim 1, wherein the treatment time of hydrothermal crystallization is greater than or equal to 8h, preferably 12-36 h, and further preferably 20-24 h.

8. Cryptomelane whiskers prepared by the preparation method of any one of claims 1-7.

9. The application of the cryptomelane whiskers prepared by the preparation method of any one of claims 1-7 is characterized in that the cryptomelane whiskers are used as a pollutant treatment material.

10. Use according to claim 9, for treatment materials of heavy metals, metalloid pollutants, harmful fumes;

preferably, the heavy metal and metalloid pollutants are at least one of cadmium, chromium, mercury, lead, nickel, zinc, cobalt, tin and arsenic;

preferably, the harmful flue gas is nitrogen oxide, and more preferably NO and NO₂At least one of (1).