Method for enhancing whiteness of phosphogypsum

Abstract

The invention provides a method for enhancing the whiteness of ardealite, and belongs to the technical field of ardealite treatment. The method provided by the invention comprises the following steps: uniformly mixing ardealite, a sulfuric acid solution and an additive, and carrying out a stirring reaction after the ardealite is dissolved. According to the method, the ardealite is treated by using the sulfuric acid solutions with different concentrations and the additive, so that the whiteness of the ardealite can be increased, the morphology can be regulated and controlled, and meanwhile, the technical effect of crystal form control can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of phosphogypsum processing, and in particular to a method for enhancing the whiteness of phosphogypsum. Background Art

[0002] The comprehensive disposal and resource utilization of phosphogypsum has always been a global problem. Phosphogypsum is an industrial solid waste discharged during the wet production of phosphoric acid. Its main component is calcium sulfate dihydrate. 4 to 5 tons of phosphogypsum are discharged for every ton of phosphoric acid produced. At present, the utilization rate of phosphogypsum is only 30 to 40%. From the perspective of environmental protection and technical safety, the comprehensive utilization of phosphogypsum waste residue has received more and more attention.

[0003] After proper treatment, phosphogypsum can be used not only to prepare building gypsum products, such as gypsum boards (paper-faced gypsum boards, gypsum fiberboards), gypsum blocks, building gypsum powder, ceramic decorative materials, gypsum building standard bricks, and cement retarders, such as gypsum combined with cement, sand and gravel as reinforcement materials for soft roadbeds, but also to make gypsum-based conductive materials, gypsum-based magnetic materials, new thermal insulation materials, high-water-speed solidification materials - mining fillers, new phosphogypsum-based polyvinyl chloride profiles, etc. In addition, purified phosphogypsum can also be used as various industrial fillers, such as papermaking fillers, desiccants, polishing materials for casting molds and glass industries, and regulators for aerated concrete.

[0004] Because phosphogypsum contains organic impurities, as well as a small amount of SiO2 and metal ion impurities such as iron, magnesium, and aluminum, it is generally light yellow, light gray, or gray-black, with a low whiteness, which greatly limits its industrial application. With the application and promotion of phosphogypsum in various industries, especially for indoor painting and decorative products, the requirements for the whiteness of gypsum are getting higher and higher, and the research on gypsum whitening has gradually attracted the attention of the industry and scientific researchers. Summary of the invention

[0005] Based on the above content, the purpose of the present invention is to provide a method for enhancing the whiteness of phosphogypsum. The method provided by the present invention can not only achieve the purpose of whitening phosphogypsum, but also regulate the morphology of phosphogypsum and control the crystal form of phosphogypsum.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a method for enhancing the whiteness of phosphogypsum, comprising uniformly mixing phosphogypsum, a sulfuric acid solution and an additive, and stirring the mixture for reaction after the phosphogypsum is dissolved.

[0007] Preferably, the dosage ratio of the phosphogypsum and the sulfuric acid solution is 25g:100mL.

[0008] Preferably, the concentration of sulfuric acid in the sulfuric acid solution is 2-60 wt %.

[0009] Preferably, the additive is polysulfate and / or disodium ethylenediaminetetraacetic acid.

[0010] Further preferably, the amount of the polysulfate is 0.4-0.7wt% of the phosphogypsum; the amount of the disodium salt of ethylenediaminetetraacetic acid is 0.5-1wt% of the phosphogypsum.

[0011] Further preferably, the polysulfate is polyaluminum sulfate; the disodium salt of ethylenediaminetetraacetic acid is calcium disodium ethylenediaminetetraacetate or magnesium disodium ethylenediaminetetraacetate.

[0012] Preferably, the phosphogypsum is aged phosphogypsum or fresh phosphogypsum.

[0013] Preferably, the stirring reaction is carried out at a temperature of 80-100° C. and for a time of 3-6 hours.

[0014] Preferably, after the stirring reaction is completed, the method further comprises the steps of filtering and washing, and drying the sample obtained by filtering and washing.

[0015] Beneficial effects:

[0016] The present invention uses sulfuric acid solutions and additives of different concentrations to treat phosphogypsum, thereby increasing the whiteness of the phosphogypsum and achieving morphology regulation, and at the same time achieving the technical effect of crystal form control.

[0017] The method provided by the invention is simple, has mild reaction conditions, low cost and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The SEM images of the phosphogypsum treated in Examples 1-5 and the original gypsum, wherein A is Example 1, B is Example 2, C is Example 3, D is Example 4, E is Example 5, and F is the original gypsum;

[0020] Figure 2 The SEM images of the treated phosphogypsum and original gypsum (PG) in Example 6;

[0021] Figure 3 The XRD diagram of the treated phosphogypsum in Examples 1-6. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation 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 associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] The invention provides a method for enhancing the whiteness of phosphogypsum. The method comprises the steps of uniformly mixing phosphogypsum, a sulfuric acid solution and an additive, and stirring and reacting the phosphogypsum after the phosphogypsum is dissolved.

[0028] In some embodiments, the usage ratio of the phosphogypsum and the sulfuric acid solution is 25 g:100 mL.

[0029] In some embodiments, the concentration of sulfuric acid in the sulfuric acid solution is 2-60 wt %.

[0030] The present invention utilizes the difference in solubility of phosphogypsum in acids of different concentrations, and through a dissolution and recrystallization process, achieves the technical effects of whitening, morphology and crystal form control. As the acid concentration increases, the solubility of phosphogypsum increases, causing the phosphogypsum to recrystallize, resulting in changes in morphology and particle size, and a decrease in particle size. When the acid concentration is too high, the strong oxidizing property is enhanced, and part of the organic matter is carbonized, resulting in a decrease in whiteness. Therefore, in order to adjust the morphology and crystal form of phosphogypsum while obtaining a greater whiteness, the present invention preferably uses the above parameter range.

[0031] In some embodiments, the additive is polysulfate and / or disodium ethylenediaminetetraacetic acid.

[0032] In some embodiments, the amount of the polysulfate is 0.4-0.7 wt % of the phosphogypsum; the amount of the disodium salt of ethylenediaminetetraacetic acid is 0.5-1 wt % of the phosphogypsum.

[0033] In the present invention, the amount of additives used will affect the whiteness. If the amount of additives used is too little, the whiteness of phosphogypsum will not change significantly. As the amount of additives used increases, the whiteness of phosphogypsum will increase significantly. When the amount of additives used is too much, the whiteness of phosphogypsum will not change significantly, and the process cost will also be increased. In order to obtain better whiteness and control costs at the same time, the amount of additives used in the present invention is preferably within the above parameter range.

[0034] In some embodiments, the polysulfate is polyaluminum sulfate; the disodium salt of EDTA is calcium disodium EDTA or magnesium disodium EDTA.

[0035] In some embodiments, the phosphogypsum is aged phosphogypsum or fresh phosphogypsum.

[0036] In some embodiments, the stirring reaction is carried out at a temperature of 80-100° C. and for a time of 3-6 hours.

[0037] In some embodiments, after the stirring reaction is completed, the method further includes the steps of filtering and washing, and drying the sample obtained by filtering and washing.

[0038] In some embodiments, the method for enhancing the whiteness of phosphogypsum comprises the following specific steps:

[0039] Add 25g of phosphogypsum (PG) to 100ml of a dilute sulfuric acid solution with a concentration of 2-60wt%, stir evenly, then add 0.4-0.7% of polysulfate and / or 0.5-1% of disodium ethylenediaminetetraacetic acid in a mass ratio of phosphogypsum. After the above-mentioned drugs are dissolved, stir and react at 80-100°C for 3-6h, filter and wash until neutral, and then dry.

[0040] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0041] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0042] The phosphogypsum used in the embodiments comes from a chemical plant in Guizhou, and the phosphogypsum is aged phosphogypsum or fresh phosphogypsum.

[0043] Example 1

[0044] Add 25g of old phosphogypsum to 100ml of 5wt% dilute sulfuric acid solution, stir evenly, then add 0.7% of polyaluminum sulfate and 0.5% of calcium disodium ethylenediaminetetraacetate by mass of the old phosphogypsum, after the above-mentioned drugs are dissolved, stir and react at 80°C for 4h, filter and wash until neutral, and then dry.

[0045] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0046] Example 2

[0047] Add 25g of fresh phosphogypsum to 100ml of 10wt% dilute sulfuric acid solution, stir evenly, then add 0.4% of polyaluminum sulfate and 0.7% of calcium disodium ethylenediaminetetraacetate by mass of the fresh phosphogypsum, after the above chemicals are dissolved, stir and react at 80°C for 5h, filter and wash until neutral, and then dry.

[0048] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0049] Example 3

[0050] Add 25g of fresh phosphogypsum to 100ml of 20wt% dilute sulfuric acid solution, stir evenly, then add 0.7% of polyaluminum sulfate and 1% of calcium disodium ethylenediaminetetraacetate by mass of the fresh phosphogypsum. After the above-mentioned chemicals are dissolved, stir and react at 90°C for 6h, filter and wash until neutral, and then dry.

[0051] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0052] Example 4

[0053] Add 25g of old phosphogypsum to 100ml of 40wt% dilute sulfuric acid solution, stir evenly, then add 0.7% of polyaluminum sulfate and 1% of disodium magnesium ethylenediaminetetraacetate by mass of the old phosphogypsum, after the above chemicals are dissolved, stir and react at 90°C for 4h, filter and wash until neutral, and then dry.

[0054] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0055] Example 5

[0056] Add 25g of old phosphogypsum to 100ml of 60wt% dilute sulfuric acid solution, stir evenly, then add 0.5% of polyaluminum sulfate and 0.8% of disodium magnesium ethylenediaminetetraacetate by mass of the old phosphogypsum, after the above chemicals are dissolved, stir and react at 100°C for 3h, filter and wash until neutral, and then dry.

[0057] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0058] Example 6

[0059] Add 25g of old phosphogypsum to 100ml of deionized water, stir evenly, then add 0.7% of polyaluminum sulfate and 1% of calcium disodium ethylenediaminetetraacetate by mass of the old phosphogypsum, after the above drugs are dissolved, stir and react at 80°C for 4h, filter and wash until neutral, and then dry.

[0060] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0061] Example 7

[0062] Add 25g of fresh phosphogypsum into 100ml of 40wt% dilute sulfuric acid solution, stir evenly, add 0.7% of polyaluminum sulfate by mass of fresh phosphogypsum, after the above reagents are dissolved, stir and react at 80℃ for 4h, filter and wash until neutral, and then dry.

[0063] The whiteness of the dried sample was measured using a whiteness meter, and a scanning microscope and a particle size analyzer were used to observe the changes in the morphology and structure and the changes in the particle size, respectively.

[0064] Example 8

[0065] Add 25g of fresh PG phosphogypsum to 100ml of 40wt% dilute sulfuric acid solution, stir evenly, add 1% of calcium disodium ethylenediaminetetraacetate by mass, and after the above reagents are dissolved, stir and react at 100℃ for 4h, filter and wash until neutral, and then dry.

[0066] The whiteness of the dried sample was measured using a whiteness meter, and the particle size analyzer was used to analyze the change in particle size.

[0067] Comparative Example 1

[0068] Add 25g of fresh phosphogypsum into 100ml of 40wt% dilute sulfuric acid solution, stir evenly without adding additives. After the above reagents are dissolved, stir and react at 80℃ for 4h, filter and wash until neutral, and then dry.

[0069] The whiteness of the dried sample was measured using a whiteness meter, and the particle size analyzer was used to analyze the change in particle size.

[0070] The changes in whiteness and particle size of phosphogypsum under different implementation conditions of Examples 1-8 and Comparative Example 1 are shown in Table 1.

[0071] Table 1 Changes in whiteness and particle size under different implementation conditions

[0072]

[0073] As can be seen from Table 1, with the increase of acid concentration (original gypsum sample and Examples 1-5), the whiteness of phosphogypsum gradually increases, and the particle size also shows a decreasing trend, indicating that the increase in acid concentration causes the original gypsum to dissolve and recrystallize, resulting in a smaller particle size. When the acid concentration increases to 60%, the whiteness begins to decrease. This is because the increase in sulfuric acid concentration increases the strong oxidizing property, and part of the organic matter is carbonized, resulting in a decrease in whiteness.

[0074] When the phosphogypsum is treated with additives only without acid treatment (Example 6), the whiteness of the phosphogypsum can be increased, but the crystal form cannot be adjusted and the particle size cannot be reduced.

[0075] When the acid concentration is kept constant and only one of the additives is used for treatment (Examples 7 and 8), the particle size of the phosphogypsum decreases and the whiteness increases significantly.

[0076] When no additives are added and only acid treatment is performed (Comparative Example 1), although the particle size of phosphogypsum is reduced, the increase in whiteness is not obvious.

[0077] The phosphogypsum treated in Examples 1-6 was subjected to SEM analysis. Figure 1It can be seen that with the increase of acid concentration, the morphology of phosphogypsum changes greatly, from the original trapezoidal block to granular, and the particle size becomes smaller. This is because the increase in acid concentration increases the solubility of phosphogypsum, causing the phosphogypsum to recrystallize, resulting in changes in morphology and particle size. Figure 2 It can be seen that only the addition of additives did not change the morphology of phosphogypsum, but increased the whiteness of the original gypsum.

[0078] The XRD patterns of the treated phosphogypsum in Examples 1-6 are as follows: Figure 3 As shown, it can be seen that with the increase of acid concentration, the original phosphogypsum gradually changes from dihydrate gypsum to anhydrous gypsum, and only adding additives does not affect the crystal form of the original phosphogypsum.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for enhancing the whiteness of phosphogypsum, characterized in that: Evenly mix the phosphogypsum, sulfuric acid solution and additives, and stir to react after the phosphogypsum is dissolved.

2. The method for enhancing the whiteness of phosphogypsum according to claim 1, characterized in that: The dosage ratio of the phosphogypsum and the sulfuric acid solution is 25g:100mL.

3. The method for enhancing the whiteness of phosphogypsum according to claim 1 or 2, characterized in that: The concentration of sulfuric acid in the sulfuric acid solution is 2-60 wt %.

4. The method for enhancing the whiteness of phosphogypsum according to claim 1, characterized in that: The additive is polysulfate and / or disodium ethylenediaminetetraacetic acid.

5. The method for enhancing the whiteness of phosphogypsum according to claim 4, characterized in that: The amount of the polysulfate is 0.4-0.7wt% of the phosphogypsum; the amount of the disodium salt of ethylenediaminetetraacetic acid is 0.5-1wt% of the phosphogypsum.

6. The method for enhancing the whiteness of phosphogypsum according to claim 4 or 5, characterized in that: The polysulfate is polyaluminum sulfate; the disodium salt of ethylenediaminetetraacetic acid is calcium disodium ethylenediaminetetraacetate or magnesium disodium ethylenediaminetetraacetate.

7. The method for enhancing the whiteness of phosphogypsum according to claim 1, characterized in that: The phosphogypsum is aged phosphogypsum or fresh phosphogypsum.

8. The method for enhancing the whiteness of phosphogypsum according to claim 1, characterized in that: The stirring reaction is carried out at a temperature of 80-100° C. and for a time of 3-6 hours.

9. The method for enhancing the whiteness of phosphogypsum according to claim 1, characterized in that: After the stirring reaction is completed, the steps of suction filtration and washing and drying the sample obtained by suction filtration and washing are also included.

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