CN114381150B - Composite coating material for separating and purifying heavy metals and preparation method thereof - Google Patents

Abstract

The invention discloses a composite coating material for obstructing and purifying heavy metal and a preparation method thereof, belonging to the technical field of heavy metal in-situ pollution control.

Description

A composite coating material for blocking and purifying heavy metals and its preparation method

technical field

The invention relates to the technical field of heavy metal in-situ pollution control, in particular to a composite coating material for blocking and purifying heavy metals and a preparation method thereof.

Background technique

Heavy metal pollution has the characteristics of complexity, persistence, concealment, and difficulty in treatment. Discharge into the environment will cause serious pollution to soil and groundwater, endangering human health and ecological security. Controlling heavy metal pollution sources from the source is an economical, reasonable and feasible effective treatment method. This method limits the migration of heavy metals by blocking the diffusion pathway of heavy metals, so as to achieve the purpose of risk control.

Phosphogypsum is a solid waste produced in the wet-process phosphoric acid process, and is a key factor restricting the development of the phosphorus chemical industry. Excessive stockpiling of phosphogypsum not only pollutes groundwater resources, but also wastes land resources and seriously damages the ecological environment.

Clay, bentonite, etc. are currently the most researched and applied barrier materials. These barrier materials have good anti-seepage performance and isolation effect, but their adsorption or fixation and purification capabilities for heavy metals are weak, and heavy metals cannot be effectively removed. Leakage will seriously endanger the environment. Therefore, it is of great significance to explore a composite material with both heavy metal barrier and heavy metal purification, and to effectively utilize phosphogypsum.

Contents of the invention

Aiming at the problem that the adsorption capacity of the reaction medium and the barrier and anti-seepage capacity cannot be combined in the heavy metal in-situ barrier technology, the present invention provides a composite coating material for barrier and purification of heavy metals and its preparation method, using industrial waste phosphogypsum as raw material 1. Hydroxyapatite is made through microwave-assisted chemical reaction, and clay and potassium silicate are added to improve the adhesion and anti-seepage performance of the composite coating material.

To achieve the above object, the present invention provides the following scheme:

The invention provides a composite coating material for blocking and purifying heavy metals. The raw materials include the following components in parts by mass: 20-70 parts of phosphogypsum, 1-3 parts of Ca(OH) ₂ , (NH ₄ ) ₂ HPO ₄ 2-4 parts, 1-2 parts of ammonia water, 10-20 parts of clay, 15-50 parts of water, 1-2 parts of potassium silicate and 1-2 parts of nano silicon dioxide.

The present invention also provides a preparation method of the composite coating material for blocking and purifying heavy metals, which includes the following steps: using phosphogypsum as a raw material, preparing hydroxyapatite through a microwave-assisted chemical reaction, adding clay and calcining at high temperature, and then adding potassium silicate and Nano silica, mix well.

Further, the preparation method specifically includes the following steps: (1) drying the clay and phosphogypsum at 50-80°C for 12-48 hours, and then pulverizing them respectively;

(2) Mix phosphogypsum with Ca(OH) ₂ , then grind with a ball mill, add (NH ₄ ) ₂ HPO ₄ and mix evenly, then grind and mix with a ball mill;

(3) Ammonia and water are added to the mixture in step (2) to make the mixture fully wet, and then transferred to the reaction kettle and left at room temperature;

(4) Transfer the reaction kettle to a microwave reaction device for reaction for 10-30 minutes, and dry at 40-50°C for 3-6 hours;

(5) Add clay, fully mix and calcined, and the calcined product is ground with a ball mill to make the particle size <50 μm;

(6) Potassium silicate and nano-silicon dioxide are added to the calcined product, and mixed thoroughly to obtain the composite coating material.

Further, the step (1) is crushed into particles with a particle diameter of <200 μm.

Further, in step (2), the phosphogypsum is mixed with Ca(OH) ₂ and then ground for 5-10 minutes; (NH ₄ ) ₂ HPO ₄ is added and then ground for 10-30 minutes.

Further, step (3) standing at room temperature for 8-16h.

Further, the calcination temperature in step (5) is 400-600°C, and the time is 1-3h.

Further, the microwave power is 1200W, and the frequency is 2450MHz.

The invention also provides a composite paint prepared from the composite coating material for blocking and purifying heavy metals.

The invention also provides the application of the composite paint in blocking and purifying heavy metals.

The main component of phosphogypsum is calcium sulfate, and it also contains incompletely decomposed phosphate rock, residual phosphoric acid and other components, which can be used as potential precursors for the synthesis of hydroxyapatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ) substance. Hydroxyapatite, like nano-silica, has high-efficiency heavy metal adsorption capacity, which can not only fill the internal pores of barrier engineering walls and coatings, improve anti-seepage performance, but also fix and purify heavy metals. In addition, the silicification reaction of silicate can improve the permanent adhesion between the coating material and the barrier engineering, improve the anti-seepage performance and prolong the service life.

The invention discloses the following technical effects:

The present invention makes full use of industrial solid waste (phosphogypsum) and low-cost, easily-obtained clay, and the cost of raw materials is low; the composition of Ca ²⁺ and PO ₄ ^3- rich in phosphogypsum is used in chemical reaction and microwave-assisted synthesis Under the action, hydroxyapatite with high adsorption capacity of heavy metals is generated; using the aluminosilicate rich in clay, the characteristics of strong plasticity and silicification reaction of potassium silicate can fill the internal pores of the material, improve the impermeability and permanent Adhesion and service life; In addition, the added nano-silica can improve the adhesion and heavy metal adsorption performance of the composite coating material. The composite coating material prepared by the invention has strong adhesion and anti-seepage performance, and has strong adsorption and fixation effects on heavy metal ions, that is, it has both heavy metal barrier and purification effects.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the SEM figure of the composite coating material prepared by embodiment 1;

FIG. 2 is an SEM image of the composite coating material prepared in Comparative Example 3.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention.

It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention. In addition, regarding the numerical ranges in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Any stated value or intervening value in a stated range, and each smaller range between any other stated value or intervening value in a stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control.

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The description and examples of the invention are illustrative only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

Example 1

The composite coating material includes the following raw materials by weight: 45 parts of phosphogypsum, 2 parts of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 30 parts of ultrapure water, 20 parts of clay, potassium silicate 2 parts, 2 parts of nano silicon dioxide.

Preparation method: Clay and phosphogypsum dried at 80°C for 12 hours were pulverized into particles with a particle size of <200 μm; the phosphogypsum was mixed with Ca(OH) ₂ and ground for 10 minutes with a ball mill, and then added (NH ₄ ) ₂ HPO ₄ Mix evenly, then grind and mix with a ball mill for 20 minutes; add ammonia water to the obtained mixture, then add ultrapure water to make the mixture fully wet, then transfer it to the reaction kettle, let it stand at room temperature for 16 hours, and then transfer the reaction kettle to the microwave reactor React in medium for 30 minutes, microwave power is 1200W, frequency is 2450MHz; the obtained reactant is dried at 50°C for 3h, then added to clay, fully mixed and then calcined at 600°C for 2h, and the calcined product is ground with a ball mill to make the particle size <50μm; Add 2 parts of potassium silicate and 2 parts of nano-silicon dioxide to the mixture, and mix well to obtain a composite coating material.

Before use, take 50 parts of the composite coating material, add 40 parts of water, and stir evenly to obtain a composite coating, which is subjected to a performance test. The method of measuring the permeability coefficient refers to the national standard GB/T 19979.2-2006 "Impermeability of Geosynthetics Part 2: Determination of Permeability Coefficient"; the bond strength is measured by a digital display bond strength detector (JG/T 507-2016) . The results are shown in Table 1.

Heavy metal barrier purification experiment: apply brushing method on the inner layer of square glass box without cover (length*width*height: 20cm*20cm*20cm), smooth evenly, thickness 1mm, and apply the composite coating after fully drying The layer was subjected to the heavy metal barrier purification experiment. The concentration of the heavy metal pollution solution used in the test is Pb 1000mg/L, Cd 500mg/L, and Mn 500mg/L. The concentration of heavy metals remaining in the contaminated solution after treatment was measured, and the removal rate of heavy metals by the composite coating was analyzed. The results are shown in Table 1.

Example 2

The composite coating material includes the following raw materials by weight: 25 parts of phosphogypsum, 1 part of Ca(OH) ₂ , 2 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 20 parts of ultrapure water, 15 parts of clay, potassium silicate 1 part, 1 part of nano silicon dioxide.

The preparation method is the same as in Example 1, and the performance test and heavy metal barrier purification experiment are also the same as in Example 1.

Example 3

The composite coating material includes the following raw materials in parts by weight: 70 parts of phosphogypsum, 1 part of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 2 parts of ammonia water, 45 parts of ultrapure water, 20 parts of clay, potassium silicate 2 parts, 2 parts of nano silicon dioxide.

The preparation method is the same as in Example 1, and the performance test and heavy metal barrier purification experiment are also the same as in Example 1. The results are shown in Table 1.

Example 4

The composite coating material includes the following raw materials by weight: 45 parts of phosphogypsum, 1 part of Ca(OH) ₂ , 3 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 30 parts of ultrapure water, 10 parts of clay, potassium silicate 1 part, 1 part of nano silicon dioxide.

The preparation method is the same as in Example 1, and the performance test and heavy metal barrier purification experiment are also the same as in Example 1. The results are shown in Table 1.

Example 5

The raw materials in parts by weight of the composite coating material are the same as in Example 1.

Preparation method: Clay and phosphogypsum dried at 80°C for 12 hours were pulverized into particles with a particle size of <200 μm; the phosphogypsum was mixed with Ca(OH) ₂ and ground for 10 minutes with a ball mill, and then added (NH ₄ ) ₂ HPO ₄ Mix evenly, then grind and mix with a ball mill for 20 minutes; add ammonia water to the obtained mixture, then add ultrapure water to make the mixture fully wet, then transfer to the reaction kettle, let it stand at room temperature for 10 hours, and then transfer the reaction kettle to the microwave reactor React in medium for 20 minutes, microwave power is 1200W, frequency is 2450MHz; the obtained reactant is dried at 50°C for 3h, then added to clay, fully mixed and then calcined at 400°C for 2h, and the calcined product is ground with a ball mill to make the particle size <50μm; in the above calcined product Potassium silicate and nano-silicon dioxide are added to the mixture, and the composite coating material is obtained by mixing well.

The performance test of the composite coating and the heavy metal barrier and purification experiment of this embodiment are the same as those of Example 1, and the results are shown in Table 1.

Example 6

The raw materials, preparation method and performance test of the composite coating material are the same as those in Example 1.

Heavy metal barrier purification experiment: Apply the above composite coating material on the inner layer of the square glass box without a cover (length*width*height: 20cm*20cm*20cm) by brushing method, evenly smooth, thickness 2mm, fully dry Afterwards, the heavy metal barrier purification experiment was carried out on the composite coating. The concentration of heavy metal pollution solution used in the test is Pb 800mg/L, Cd 500mg/L, Mn 500mg/L. The concentration of heavy metals remaining in the pollution solution after treatment was measured, and the removal rate of heavy metals by the composite coating was analyzed. The results are shown in Table 1.

Table 1 Example 1-6 Composite coating material performance and heavy metal barrier purification test results

The above results show that the composite coating material of the present invention has strong anti-seepage performance, and the permeability coefficients are all lower than 0.54×10 ^-8 m/s; the adhesion is strong, and the bond strength is greater than 0.93MPa; The removal rate is higher than 89.52%.

Comparative example 1

The composite coating material includes the following raw materials in parts by weight: 45 parts of phosphogypsum, 2 parts of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 30 parts of ultrapure water, and 20 parts of clay.

Preparation method: Clay and phosphogypsum dried at 80°C for 12 hours were crushed into particles with a particle size of <200 μm; the phosphogypsum was mixed with Ca(OH) ₂ , then ground for 10 minutes with a ball mill, and then mixed with (NH4) ₂ HPO ₄ Uniformly, then use a ball mill to grind and mix for 20 minutes; add ammonia water to the obtained mixture, then add ultrapure water to make the mixture fully wet, then transfer it to the reaction kettle, let it stand at room temperature for 16 hours, and then transfer the reaction kettle to the microwave reactor React for 30 minutes, the microwave power is 1200W, and the frequency is 2450MHz; the obtained reactant is dried at 50°C for 3h, then added to clay, fully mixed and then calcined at 600°C for 2h, and the calcined product is ground with a ball mill to make the particle size <50μm; mix well, The composite coating material is obtained.

The performance test and heavy metal barrier purification experiment are the same as in Example 1, and the results are shown in Table 2.

Comparative example 2

The composite coating material includes the following raw materials by weight: 45 parts of phosphogypsum, 2 parts of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 30 parts of ultrapure water, 2 parts of potassium silicate, nano Silica 2 parts.

Preparation method: Grind the phosphogypsum dried at 80°C for 12 hours into particles with a particle size of <200 μm; mix the phosphogypsum with Ca(OH) ₂ , and grind it with a ball mill for 10 minutes, then add (NH ₄ ) ₂ HPO ₄ and mix evenly. Then use a ball mill to grind and mix for 20 minutes; add ammonia water to the obtained mixture, then add ultrapure water to make the mixture fully wet, then transfer it to the reaction kettle, let it stand at room temperature for 16 hours, and then transfer the reaction kettle to a microwave reactor for 30 minutes. , the microwave power is 1200W, and the frequency is 2450MHz; the obtained reactants are dried at 50°C for 3 hours and then fully mixed, calcined at 600°C for 2 hours, and the calcined product is ground with a ball mill to make the particle size <50 μm; add potassium silicate to the above calcined product 2 parts, 2 parts of nano-silicon dioxide, fully mixed evenly to obtain a composite coating material.

The performance test and heavy metal barrier purification experiment are the same as in Example 1, and the results are shown in Table 2.

Comparative example 3

The composite coating material includes the following raw materials by weight: 45 parts of phosphogypsum, 2 parts of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 15 parts of ultrapure water, 20 parts of clay, potassium silicate 2 parts, 2 parts of nano silicon dioxide.

Preparation method: mix Ca(OH) ₂ and (NH ₄ ) ₂ HPO ₄ evenly, grind with a ball mill for 10 minutes, add ammonia water and ultrapure water to make the mixture fully wet, then transfer to a reaction kettle, and stand at room temperature for 16 hours Finally, transfer the reaction kettle to a microwave reactor for 30 minutes of reaction, the microwave power is 1200W, and the frequency is 2450MHz; the obtained reactant is dried at 50°C for 3 hours, then added with phosphogypsum, clay, potassium silicate, and nano-silicon dioxide, and then ground with a ball mill Mix for 20 minutes, and then calcinate the resulting mixture at 600°C for 2 hours to obtain a composite coating material.

The performance test and heavy metal barrier purification experiment are the same as in Example 1, and the results are shown in Table 2.

Comparative example 4

The composite coating material includes the following raw materials by weight: 45 parts of phosphogypsum, 2 parts of Ca(OH) ₂ , 4 parts of (NH ₄ ) ₂ HPO ₄ , 1 part of ammonia water, 30 parts of ultrapure water, 20 parts of clay, potassium silicate 2 parts, 2 parts of nano silicon dioxide.

Preparation method: Clay and phosphogypsum dried at 80°C for 12 hours were pulverized into particles with a particle size of <200 μm; the phosphogypsum was mixed with Ca(OH) ₂ and ground for 10 minutes with a ball mill, and then added (NH ₄ ) ₂ HPO ₄ Mix evenly, then grind and mix with a ball mill for 20 minutes; add ammonia water to the obtained mixture, then add ultrapure water to make the mixture fully wet, then transfer it to the reaction kettle, let it stand at room temperature for 16 hours, and then transfer the reaction kettle to the microwave reactor React in medium for 30 minutes, microwave power is 1200W, frequency is 2450MHz; the obtained reactant is dried at 50°C for 3h, then added to clay, fully mixed and then calcined at 1000°C for 2h, and the calcined product is ground with a ball mill to make the particle size <50μm; Add 2 parts of potassium silicate and 2 parts of nano-silicon dioxide to the mixture, and mix well to obtain a composite coating material.

The performance test and heavy metal barrier purification experiment are the same as in Example 1, and the results are shown in Table 2.

Table 2 Comparative Examples 1-4 Composite coating material properties and heavy metal barrier purification test results

As can be seen from the above results, the composite coating material permeability coefficient and bond strength performance without adding potassium silicate (comparative example 1) and clay (comparative example 2) are obviously lower than examples; not at the calcination temperature of the present invention (comparative example 4 ) permeability coefficient, bond strength and heavy metal removal rate are all reduced to a certain extent; the permeability coefficient, bond strength and heavy metal removal rate of the composite coating material are significantly reduced by changing the preparation method and material addition sequence (comparative example 3) . The SEM figure of the composite coating material prepared in embodiment 1 is shown in Fig. 1, the SEM figure of the composite coating material prepared in comparative example 3 is shown in Fig. 2, as can be seen from the SEM figure, the composite coating prepared by the method of the present invention The material (Fig. 1) is loose and porous, with irregular shape and rough surface, and has hydroxyapatite crystals on the surface, which help to improve the adsorption performance. However, the composite coating material obtained in Comparative Example 3 (Fig. 2) is mostly agglomerated into larger spherical bodies, which is not conducive to adsorption.

The above-mentioned embodiments are only to describe the preferred mode of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (5)

1. The preparation method of the composite coating material for blocking and purifying heavy metals is characterized by comprising the following steps: preparing hydroxyapatite from phosphogypsum serving as a raw material through microwave-assisted chemical reaction, adding clay, calcining at the high temperature of 400-600 ℃, adding potassium silicate and nano-silica, and uniformly mixing;

the method specifically comprises the following steps:

(1) Respectively drying clay and phosphogypsum for 12-48h at 50-80 ℃, and then respectively crushing;

(2) Mixing phosphogypsum and Ca (OH) ₂ Mixing, grinding, adding (NH) ₄ ) ₂ HPO ₄ Mixing, and grinding;

(3) Adding ammonia water and water into the mixture obtained in the step (2), and standing at room temperature;

(4) Putting the substance obtained in the step (3) into a microwave reaction device for reaction for 10-30min, and drying at 40-50 ℃ for 3-6h;

(5) Adding clay, fully and uniformly mixing, calcining, and grinding calcined substances until the particle size is less than 50 mu m;

(6) Adding potassium silicate and nano silicon dioxide into the calcined substance, and fully and uniformly mixing to obtain the composite coating material;

the composite coating material for blocking and purifying heavy metals comprises the following raw materials in parts by mass: 20-70 parts of phosphogypsum, ca (OH) ₂ 1-3 parts of (NH) ₄ ) ₂ HPO ₄ 2-4 parts of ammonia water, 1-2 parts of clay, 15-50 parts of water, 1-2 parts of potassium silicate and 1-2 parts of nano silicon dioxide.

2. The method according to claim 1, wherein the step (1) is carried out by pulverizing the respective particles to a particle size of less than 200 μm.

3. The method of claim 1, wherein step (2) is mixing phosphogypsum with Ca (OH) ₂ Mixing, and grinding for 5-10min; adding (NH) ₄ ) ₂ HPO ₄ And grinding for 10-30min.

4. The method according to claim 1, wherein the step (3) is allowed to stand at room temperature for 8 to 16 hours.

5. The preparation method of claim 1, wherein the calcination time in step (5) is 1-3h.

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