CN114700032B

CN114700032B - Hidden potassium manganese ore whisker and preparation and application thereof

Info

Publication number: CN114700032B
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: 2023-06-16
Anticipated expiration: 2042-03-17
Also published as: CN114700032A

Abstract

The invention belongs to the field of pollutant treatment, and particularly discloses a preparation method of a cryptomelane whisker, which comprises the steps of carrying out a first-stage reaction on a divalent manganese source and a permanganate source A, then supplementing a permanganate source B to carry out a second-stage reaction, and then carrying out hydrothermal crystallization treatment to obtain the cryptomelane whisker; wherein the molar ratio of the permanganate source A to the divalent manganese source is 0.5-2:1; the temperature of the first-stage reaction is 30-50 ℃; the molar ratio of the permanganate 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 the 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 and excellent heavy metal adsorption performance and flue gas denitration performance.

Description

Hidden potassium manganese ore whisker and preparation and application thereof

Technical Field

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

Technical Field

Since the 21 st century, the world has faced serious problems of population, resources, environment, etc. The continuous and rapid development of the modern society can not separate the heavy metal from the heavy metal, so that a large amount of heavy metal ions or related pollutants enter the water body, and the environment around the water body and the health of human beings are greatly threatened. The pollution of the water body is one of the serious environmental problems commonly faced by human beings, and heavy metal ions in the water body can be enriched in aquatic organisms, so that great damage is caused to organs and tissues of the organisms. In addition, if heavy metal ions entering the water body cannot be timely and effectively recycled, the heavy metal ions are not only waste of resources, but also can greatly pollute a clean water source. Therefore, how to quickly and effectively prevent heavy metal pollution of water and synchronously recycle heavy metal ions is one of the important problems faced by various countries and regions in the world.

Heavy metals have different definitions in different disciplines, and physically refer to densities greater than 4.5g/cm ³ Metal of (2); chemically refers to metals having an atomic number greater than 20; toxicology generally refers to metals with toxicity; the environmental science mainly refers to heavy elements which cannot be biodegraded and have biotoxicity, including metals such As cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), nickel (Ni), zinc (Zn), cobalt (Co), tin (Sn) and the like, and metalloid arsenic (As). The heavy metal ions in the water body have the characteristics of long-term persistence and accumulation: on the one hand, heavy metals are difficult to biodegrade, but the valence and the compound types can be changed, and after certain heavy metals enter a water body, the heavy metals can be even converted into a form with higher toxicity under the action of microorganisms; on the other hand, heavy metals can be enriched in organisms, enter the human body through a food chain, and various diseases can occur in the human body when the heavy metal ions in the human body are enriched to a certain amount.

At present, heavy metal ion pollution in water is classified into three important categories, namely a physicochemical method, a chemical method and a biological method. Each method has its advantages and disadvantages. Among them, the adsorption method has the advantages of simple operation, simple equipment, high selectivity and the like, and is favored by many researchers.

Hidden potassium manganese ore type manganese dioxide (OMS-2) has 2×2 pore structure, composed of MnO ₆ The double-chain structure formed by the regular octahedron has unique physical and chemical properties superior to those of the similar materials. OMS-2 is a porous manganese oxide with chemical composition KMn ₈ O ₁₆ Wherein K is ⁺ The ions are positioned in the one-dimensional pore canal to play a role of supporting structure and balancingThe effect of the charge. Mn element exists in the form of +2, +3 and +4 in the skeleton of OMS-2, and the exposed crystal face (110) has a large amount of unsaturated coordination Mn ions, so that conditions are created for the adsorption of other heavy metal ions. In addition, K ⁺ The ions can be exchanged with external positively charged ions, so that the adsorption capacity of other heavy metal ions is greatly improved.

The existing preparation method for preparing the cryptomelane manganese dioxide (OMS-2) has the characteristics of combining a wet process with a pyrogenic process, combining various devices and the like, however, the crystallization degree, the phase purity and the morphology uniformity of the product prepared by the existing preparation method are not ideal, and the application performance such as the pollutant treatment capability is required to be improved.

Disclosure of Invention

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

The second object 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 novel cryptomelane prepared by the preparation method in the aspects of pollutant treatment such as heavy metal polluted water treatment, harmful substances removal in flue gas and the like.

The preparation method of the hidden potassium-manganese ore whisker comprises the steps of carrying out a first-stage reaction on a divalent manganese source and a permanganate source A, then supplementing a permanganate source B to carry out a second-stage reaction, and then carrying out hydrothermal crystallization treatment to obtain the hidden potassium-manganese ore whisker;

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

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

The invention innovatively discovers that the bivalent manganese source and the permanganate source A are subjected to a first-stage reaction in advance, then the permanganate source B is supplemented to carry out a second-stage reaction, then the hydrothermal crystallization third-stage reaction is carried out at a higher temperature, and based on the three-stage reaction thought, the control of each condition is further matched, so that the coordination can be realized unexpectedly, the porous material assembled by the whiskers with high crystallinity and high phase purity can be obtained, and more importantly, the material obtained by the method has unexpected advantages in the aspects of adsorbing heavy metal ions in waste water, reducing pollutants such as flue gas denitration and the like.

The research of the invention discovers that the stepwise three-stage reaction thought of permanganate, the addition proportion on the reaction thought and the joint cooperative control of the reaction temperature of each stage are key to regulating and controlling the crystallinity, the phase, the whisker morphology of the product and improving the adsorption performance of heavy metal ions.

In the invention, the divalent manganese source can ionize Mn ²⁺ Is a water-soluble substance of (a): preferably at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate, and even manganese ore leaching liquid. The divalent manganese source can be a commercial chemical raw material or can be from a mineral smelting product (such as leaching solution).

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, such as C1-C4 alcohol, acetone, THF, etc.

According to the invention, a divalent manganese source solution is taken as a base solution, a permanganate source A is added in advance to perform a first-stage reaction, then a permanganate source B is added into a first-stage reaction system to perform a second-stage reaction, and then the second-stage reaction system is placed in a closed pressure-resistant container to perform hydrothermal crystallization treatment, and after the treatment, solid-liquid separation is performed to obtain the cryptomelane whisker.

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

The permanganate source A and the permanganate source B can ionize MnO ₄ ^- 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 cations such as potassium, sodium and the like, so that cryptomelane with corresponding interlayer cations can be prepared.

According to the invention, the research discovers that the material proportion and the temperature in the first stage of reaction can be controlled to further synergistically improve the phase purity and whisker morphology of a target product, and the performance of the product is improved.

In the present invention, the permanganate source a may be added in the form of a solid or an aqueous solution, and when added in the form of an aqueous solution, the concentration thereof may be 0.2 to 0.6M.

Preferably, the molar ratio of the permanganate source A (calculated as MnO 4) to the divalent manganese source is between 0.8 and 1.2:1, a step of; more preferably 0.8 to 1:1. It was found that, under preferred parameters, the crystallinity, phase and heavy metal adsorption properties of the produced product could surprisingly be further synergistically improved.

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

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

In the step (1), the reaction time in the first stage reaction process may be adjusted according to the preparation requirement, and the time in the first stage reaction may be 0.5 to 2 hours, more preferably 0.5 to 1 hour in view of the preparation efficiency.

According to the invention, the permanganate source B is added into the first system and stirred at a certain temperature to perform the second-stage reaction, and researches show that the strict control of the reaction temperature of the second-stage reaction and the addition amount of the permanganate source B is beneficial to cooperatively controlling the crystallinity, the phase and the whisker morphology of the product and is beneficial to cooperatively improving the adsorption performance of the prepared product on heavy metal ions.

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

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

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

The temperature of the second stage reaction is preferably 60 to 80 ℃, more preferably 70 to 80 ℃. It was found that, under preferred parameters, the heavy metal adsorption properties of the produced product could surprisingly be further synergistically improved.

In the invention, the time of the second-stage reaction can be adjusted according to the needs, and the time of the second-stage reaction can be 0.2-2 h in consideration of the preparation efficiency; further, the time 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 closed, the temperature is raised to perform a 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.

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

In the present invention, the time for hydrothermal crystallization can be adjusted as required, and in view of the production effect, the time for crystallization is, for example, 8 hours or more, 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 washing and drying are carried out to obtain the product.

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

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

step (2): adding a permanganate 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, transferring the mixed solution into a sealed container, heating to perform a third-stage reaction, and separating after the reaction is finished to obtain a whisker-shaped cryptomelane product;

the molar ratio of the permanganate source B to the divalent 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 whisker, which comprises the following steps:

(1) Mn obtained as described above ²⁺ The aqueous solution was dropped with an aqueous potassium permanganate solution (MnO 4-relative to the added Mn ²⁺ The molar ratio of (2) is 0.8-1.2:1), stirring for 0.5-1 h at 30-50 ℃ to perform a first-stage reaction to obtain a first reaction solution;

(2) Continuously dropping potassium permanganate solution (MnO 4-relative to Mn in the solution) into the mixed solution ²⁺ The molar ratio of (2) is 4-6:1), stirring and reacting for 0.5-1 h at the reaction temperature of 70-80 ℃ to obtain suspension after the second-stage reaction;

(3) Transferring the suspension into a high temperature and high pressure resistant container, sealing the reactor, and crystallizing at 200-240 ℃ for 20-24 h;

(4) Washing with absolute ethyl alcohol and deionized water to neutrality, filtering with a vacuum pump, drying at 60-120 deg.c and grinding to obtain cryptomelane whisker powder.

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

The invention also provides an application of the cryptomelane whisker obtained by the preparation method, which is used as a treatment material of pollutants.

Preferred applications, adsorbent materials for heavy metals or metalloid contaminants;

preferably, the adsorbent material is for heavy metals or metalloid contaminants in a body of water;

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

According to another application scheme of the invention, the prepared cryptomelane whisker is used as an adsorbing material for harmful smoke. The harmful fumes are for example nitrogen oxides. The nitrogen oxides are, for example, NO ₂ Nitrogen oxide contaminants. The research of the invention discovers that the prepared cryptomelane whisker not only has good heavy metal adsorption performance, but 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, the synergistic reaction can be realized by further matching with the common control of the conditions such as material proportion, reaction temperature, reaction time and the like, and the performances such as the phase purity, whisker morphology, heavy metal adsorption, denitration and the like of the cryptomelane can be improved.

2. The preparation method of the cryptomelane whisker for efficiently adsorbing heavy metal ions in wastewater 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 treatment, waste gas treatment and the like.

Drawings

FIG. 1 is an X-ray diffraction and SEM image of the cryptomelane whisker prepared in example 1;

FIG. 2 is a scanning electron microscope picture of the product from groups A, B and C of example 2;

FIG. 3X-ray diffraction pattern of group 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 groups A and 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 of comparative example 1;

FIG. 9 is a graph showing the degradation of nitrogen oxides as a function of temperature for the product prepared in example 1 in example 9.

The specific embodiment is as follows:

recording the heavy metal ion adsorption step in water and the data measurement method:

the absorbed 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 was 100.+ -.5 mg/L, a certain amount of 0.2g/L of the adsorbent was taken and put into a 250mL Erlenmeyer flask, and the adsorbent was added thereto, and the mixture was shaken at a rotation speed of 250rpm for 24 hours at room temperature and sampled at various times, and the adsorbent and the lead ion solution in the mixed solution were separated with a 0.45 μm filter membrane, and the removal rate (R) and adsorption capacity (Q) were calculated.

R＝(C ₀ -C ₁ )/C ₀ *100％

Q＝(C ₀ -C ₁ )V/m

Wherein C is ₀ Is the initial concentration (mg/L) of the heavy metal ion solution, C ₁ 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 according to the invention is, for example, 20 to 35 ℃.

Example 1

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

(2) Dropwise adding 0.4M potassium permanganate solution (the dropwise adding rate is 0.01mol/min, and the dropwise adding molar quantity is 0.2mol, 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 rotating speed is 180 r/min), carrying out first-stage reaction, and the reaction time is 30min, so as to obtain a first-stage reaction solution;

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

(4) Transferring the second-stage reaction liquid into a high-temperature-resistant and high-pressure-resistant reactor, sealing the reactor, heating to 200 ℃ and performing a third-stage reaction, wherein the reaction time is 20 hours;

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

The porous cryptomelane material with high-efficiency adsorption of heavy metal ions in wastewater prepared by the embodiment has an X-ray diffraction spectrum shown in figure 1A and a scanning electron microscope picture shown in figure 1B.

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

Example 2

The difference compared with example 1 is only that the potassium permanganate in the step (2) is regulated relative to Mn ²⁺ The molar ratio of the addition is as follows: (A): potassium permanganate relative to Mn ²⁺ The molar ratio of the addition is 0.8; (B): potassium permanganate relative to Mn ²⁺ The molar ratio of the addition is 0.2; (C): potassium permanganate relative to Mn ²⁺ Adding a molar ratio of 3; (D): potassium permanganate relative to Mn ²⁺ The molar ratio of the addition is 0.5; (E): potassium permanganate relative to Mn ²⁺ The molar ratio is 2. Other operations and parameters were the same as in example 1.

The product obtained in the case of group A is shown in FIG. 2A, the whisker morphology product is obtained, and the whisker morphology products are not obtained in groups B and C because the proportion is not controlled within the scope of the invention (SEM images are shown in FIG. 2B and FIG. 2C respectively)

The adsorption experiments were carried out on each group of products, with the following results:

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

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

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

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

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

Example 3

The only difference compared to example 1 is that the temperatures of the first reaction stage of step (2) are respectively:

A：30℃；B：50℃；C：25℃；

groups a and B gave the same phase and morphology as the analogue of example 1, however, group C gave no pure phase target product, XRD of which is shown in figure 3. The obtained sample is a birnessite and cryptomelane co-organism.

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

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

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

Example 4

The difference compared with example 1 is only that the potassium permanganate in the control step (3) was compared with Mn added initially in the first step ²⁺ The molar ratios of (3) are respectively as follows: (A): potassium permanganate relative to Mn ²⁺ Adding a molar ratio of 1; (B): potassium permanganate relative to Mn ²⁺ The molar ratio of the addition is 9.5; (C): potassium permanganate relative to Mn ²⁺ Adding a molar ratio of 6; (D): potassium permanganate relative to Mn ²⁺ Adding a molar ratio of 2; (E): potassium permanganate relative to Mn ²⁺ Adding a molar ratio of 8;

groups C-E yield similar morphology cryptomelane mineral phase products, 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 of 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 of 100mg/L lead ion solution reaches 220mg/g within 10 minutes, and the removal rate reaches 44%.

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

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

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

Example 5

The difference from example 1 is only that the reaction temperature in the step (3) is controlled as follows: (A): 40 ℃; (B): 60 ℃; (C): 25 ℃; (D): 70 ℃; (E) 95 ℃;

A. b, D and E groups obtained pure cryptomelane phase products of similar morphology to example 1, however, group C did not obtain the target phase product, whose XRD is shown in FIG. 5, was a birnessite and cryptomelane co-organism.

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

Group B: when the dosage of the adsorbent is 0.2g/L, the adsorption capacity of 100mg/L lead ion solution reaches 355mg/g within 10 minutes, 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 of lead ion solution reaches 280mg/g within 10 minutes, and the removal rate reaches 56%.

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

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

Example 6

The difference from example 1 is only that the temperature of hydrothermal crystallization in step (4) is controlled as follows:

(A)：120℃；(B)：260℃；(C)：80℃；(D)：240℃；

group A and B, D obtain similar morphology and phase products as example 1, and the scanning electron microscope pictures of the materials prepared in group A are shown in figure 6A to obtain the target products. However, group C did not give the target product, SEM see fig. 6B:

(A) Group: when the adsorbent is used in an amount of 0.2g/L, the adsorption capacity of 100mg/L lead ion solution reaches 305mg/g within 10 minutes, and the removal rate reaches 61%.

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

(C) Group: when the adsorbent is used in an amount of 0.2g/L, the adsorption capacity of 100mg/L lead ion solution reaches 140mg/g within 10 minutes, and the removal rate reaches 28%.

(D) Group: when the adsorbent is used in an amount of 0.2g/L, the lead ion removal rate of 100mg/L reaches 89% within 10 minutes.

Example 7

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

A. group B gave a similar product to example 1, as group a gave the product shown in figure 7.

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

(B) Group: when the adsorbent is used in an amount of 0.2g/L, the lead ion removal rate of 100mg/L reaches 89% within 10 minutes.

Example 8

The difference compared with example 1 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 0.5h. A similar product to example 1 was obtained, and further performance measurements were made using the procedure of example 1, resulting in: when the adsorbent is used in an amount of 0.2g/L, the adsorption capacity of 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 same ratio of the raw materials was directly mixed without using three-stage reaction, and the hydrothermal crystallization treatment described in the third stage was directly performed, and the crystallization temperature and time were the same as those in example 1.

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

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

Example 9

The difference compared to example 1 is only that the synthesized product is used for NH of nitrogen oxides ₃ -SCR reduction.

NH ₃ -SCR test method:

reactor diameter: 8mm, length: 460mm. The reaction tube was filled with about 200mg of catalyst (200 mesh) in the middle and glass beads in the rest. The temperature of the reactor is detected by a K-type thermocouple, the reaction temperature is controlled to be 100-300 ℃, and SCR activity tests are set to be carried out every 50 ℃. The reaction raw material gas is composed of 500ppm NO,500ppm NH ₃ 5% O ₂ ，N ₂ Is the balance of qi. The gas composition was tested using a KANE9506 type gas analyzer. The gas mass flow device is adopted to adjust the flow of each path of gas, and the gas volume airspeed is controlled to be 30000h ^-1 . Calculating NO using the following formula _x Is a conversion rate of (2): NO (NO) _x Conversion (%) = (NO) _xletin －NO _xoutlet )÷NO _xinlet ×100％

The curve of the conversion rate of nitrogen oxide with temperature in the present case is shown in fig. 9, and the result is that the conversion rate of nitrogen oxide is 33.8% at 100 ℃; at 150 ℃, the conversion rate of nitrogen oxidation is 65.4%; at 200 ℃, the conversion rate of nitrogen oxidation is 93.7%; at 250 ℃, the conversion rate of nitrogen oxidation is 93.4%; at 300℃the conversion of nitrogen oxide was 82.4%. It can be seen that the material according to the present invention has an excellent denitration effect, and particularly a more excellent denitration effect can be obtained at a temperature of 175 ℃ or higher, particularly 200 to 400 ℃, preferably 200 to 300 ℃, and more preferably 200 to 250 ℃.

Claims

1. The application of the cryptomelane whisker in adsorbing heavy metal or metalloid pollutants in a water body is characterized in that the cryptomelane whisker is prepared by the following steps: performing a first-stage reaction on a divalent manganese source and a permanganate source A, then supplementing a permanganate source B to perform a second-stage reaction, and then performing hydrothermal crystallization treatment to obtain cryptomelane whiskers;

the molar ratio of the permanganate source B to the divalent manganese source is 2-8:1; the temperature of the second-stage reaction is 40-95 ℃;

the temperature of the hydrothermal crystallization treatment is 100-260 ℃.

2. The use according to claim 1, wherein the divalent manganese source is capable of ionizing Mn ²⁺ Is a water-soluble compound of (a).

3. The use according to claim 2, wherein the divalent manganese source is at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese acetate.

4. The use according to claim 1, wherein the solvent of the first stage reaction is water or a water-organic solvent mixture, and the organic solvent is a water-miscible solvent.

5. The use according to claim 1, wherein in the starting solution system of the first stage reaction Mn ²⁺ The molar concentration of (2) is 0.1-4M.

6. The use according to claim 1, wherein the source of permanganate A and B are capable of ionizing MnO ₄ ^- Is a water-soluble salt of (a).

7. The use according to claim 6, wherein the source of permanganate a, source of permanganate B is at least one of potassium permanganate, sodium permanganate, magnesium permanganate.

8. The use according to claim 1, wherein in the first reaction stage the molar ratio of permanganate source a to divalent manganese source is 0.8 to 1.2:1.

9. The use according to claim 1, wherein the first reaction time is 0.5 to 2 hours.

10. The use according to claim 1, wherein the molar ratio of permanganate source B to divalent manganese source is 4-6:1.

11. The use according to claim 1, wherein the second reaction time is 0.2 to 2 hours.

12. The use according to claim 1, wherein the temperature of the hydrothermal crystallization treatment is 200-240 ℃.

13. The use according to claim 1, wherein the treatment time for the hydrothermal crystallization is greater than or equal to 8h.

14. The use according to claim 13, wherein the hydrothermal crystallization is carried out for a treatment time of 12 to 36 hours.

15. The use according to claim 13, wherein the hydrothermal crystallization is carried out for a treatment time of 20 to 24 hours.

16. The use of claim 1, wherein the heavy metal and metalloid contaminants are at least one of cadmium, chromium, mercury, lead, nickel, zinc, cobalt, tin, and arsenic.