A method for preparing layered calcium sulfate using phosphogypsum

Abstract

The present invention discloses a method for preparing layered calcium sulfate using phosphogypsum, and the method comprises the following steps: mixing phosphogypsum with calcium hydroxide to prepare a slurry, subjecting the slurry to purification and separation through a hydrocyclone and then screening, selecting the product with a mesh size of 200 - 500, and then treating the product through a secondary hydrocyclone to obtain purified phosphogypsum; dissolving the purified phosphogypsum in water, adding citric acid to adjust the pH value to 5 - 6 and adding a impurity removal reagent, filtering, and then dropping ammonia water into the filtrate to adjust the pH value to 7 to obtain an aqueous solution of purified phosphogypsum; adding a crystal form growth regulator into the aqueous solution of purified phosphogypsum, heating and stirring in an oil bath, performing recrystallization and drying to obtain the layered calcium sulfate. The present invention prepares layered calcium sulfate in an aqueous system environment, without organic waste liquid, is environmentally friendly, and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention relates to a method for preparing layered calcium sulfate using phosphogypsum, and more particularly to a method for preparing layered calcium sulfate using phosphogypsum under aqueous conditions. Background Art

[0002] Calcium sulfate is a functional inorganic powder material, which has excellent properties such as light weight, good gelling, sound insulation, heat insulation, and flame retardancy of ordinary powder materials, and has the characteristics of materials such as good toughness, high strength, easy surface treatment, and strong affinity. It has advantages such as high temperature resistance and chemical corrosion resistance, and is widely used in many fields such as medicine, papermaking, environmental protection, and coatings.

[0003] With the significant environmental pollution problems caused by the stacking of industrial by-product phosphogypsum, the comprehensive utilization of phosphogypsum produced by the wet process of phosphate ore to produce phosphoric acid is a major problem. Preparing calcium sulfate from industrial by-product gypsum to increase the added value of industrial waste is an effective way to turn waste into treasure, in order to solve the problems of the stacking of industrial gypsum slag and the shortage of natural gypsum resources.

[0004] Patent Publication No. CN 112978782 A discloses a method for preparing nano-layered calcium sulfate. By mixing glycerol and ethylene glycol evenly at 60 - 80 °C, then adding a calcium ion complexing agent, continuing to stir until the particles dissolve, adding a dihydrate calcium sulfate sample for reaction, and performing solid-liquid separation while it is hot after the reaction ends, the obtained solid is dried to obtain nano-layered calcium sulfate. Although nano-layered calcium sulfate can be prepared by using dihydrate calcium sulfate or phosphogypsum containing dihydrate calcium sulfate and flue gas desulfurization gypsum and adding a calcium ion complexing agent, the process is simple and highly operable, and has the advantages of waste utilization and improving the comprehensive utilization value of gypsum by-products. However, it is carried out in an organic solvent environment, resulting in a large amount of chemical waste liquid and polluting the environment.

[0005] Therefore, how to provide a method for preparing layered calcium sulfate that is environmentally friendly without organic waste liquid in an aqueous environment is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] In view of this, to solve this problem, the present invention discloses a method for preparing layered calcium sulfate that is environmentally friendly without organic waste liquid in an aqueous environment.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for preparing layered calcium sulfate using phosphogypsum, the method specifically includes the following steps:

[0009] (1) Impurity removal and purification of phosphogypsum: Mix phosphogypsum with calcium hydroxide to form a slurry, screen it after purification and separation by a hydrocyclone, select the product with a mesh size of 200 - 500, and then treat the product with a secondary hydrocyclone to obtain purified phosphogypsum;

[0010] (2) Dissolution of phosphogypsum: Dissolve the purified phosphogypsum in water, add citric acid to adjust the pH value to 5 - 6 and add an impurity removal reagent, filter, and then drop ammonia water into the filtrate to adjust the pH value to 7 to obtain an aqueous solution of purified phosphogypsum;

[0011] (3) Regulation of calcium sulfate crystal growth: Add a crystal growth regulator to the aqueous solution of purified phosphogypsum, heat and stir in an oil bath, recrystallize and dry to obtain the layered calcium sulfate.

[0012] Optionally, the concentration of the slurry is 6% - 12%, and the inlet pressure of the hydrocyclone is 0.15 - 0.25 MPa.

[0013] Optionally, in step (2), the mass ratio of the purified phosphogypsum to water is 1:400, and the impurity removal reagent is calcium hydroxide or calcium oxide.

[0014] Optionally, the crystal growth regulator is N-(2-aminoethyl)-aminopropionate or N-(2-aminoethyl)-aminopropionate salt; the N-(2-aminoethyl)-aminopropionate salt includes one or a combination of N-(2-aminoethyl)-aminopropionate iron, N-(2-aminoethyl)-aminopropionate magnesium, and N-(2-aminoethyl)-aminopropionate zinc.

[0015] Furthermore, the addition amount of the crystal growth regulator is 0.004 - 0.02 g, and the addition amount of the crystal growth regulator is 1% - 5% of the mass of the purified phosphogypsum.

[0016] Optionally, the oil bath heating temperature is 95 °C, the drying temperature is 80 °C, and the drying time is 8 h.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The layered calcium sulfate prepared by the present invention is prepared in an aqueous system environment, without organic waste liquid, and is environmentally friendly; moreover, the prepared layered calcium sulfate not only has potential functionalization value that ordinary calcium sulfate does not have, has a significantly better effect on enhancing the rigidity of polymers than spherical and single-sheet powders, can be functionalized by organic exfoliation intercalation, but also can be refined and used as a crystal seed for improving the crystallization quality of desulfurization slurry composite gypsum crystallization promoters. Description of the Drawings

[0019] 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 for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided drawings.

[0020] Figure 1 It is the SEM image of the layered calcium sulfate prepared in Example 2 of the present invention.

[0021] Figure 2 It is the XRD pattern of the layered calcium sulfate prepared in Example 2 of the present invention.

[0022] Figure 3 It is the SEM image of the layered calcium sulfate prepared in Example 1 of the present invention.

[0023] Figure 4 It is the SEM image of the layered calcium sulfate prepared in Example 3 of the present invention.

[0024] Figure 5 It is the SEM image of the layered calcium sulfate prepared in Example 4 of the present invention. Detailed implementation manners

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] The special term "embodiment" here, any embodiment described as "exemplary" does not have to be interpreted as superior to or better than other embodiments. For the performance index tests in the embodiments of this application, unless otherwise specified, the conventional test methods in the art are adopted. It should be understood that the terms described in this application are only used to describe specific embodiments and are not used to limit the content disclosed in this application.

[0027] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as those generally understood by those of ordinary skill in the technical field to which this application belongs; the test methods and technical means not otherwise specifically noted in this application refer to the experimental methods and technical means commonly adopted by those of ordinary skill in the art.

[0028] To better illustrate the content of this application, numerous specific details are provided in the following specific embodiments. Those skilled in the art should understand that this application can still be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. that are well-known to those skilled in the art are not described in detail in order to highlight the gist of this application.

[0029] On the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the obtained technical solutions belong to the content disclosed in the embodiments of this application.

[0030] The present invention discloses a method for preparing layered calcium sulfate using phosphogypsum.

[0031] To better understand the present invention, the following embodiments are used to further specifically elaborate on the present invention, but it should not be construed as a limitation to the present invention. For those skilled in the art, some non-essential improvements and adjustments made based on the above-mentioned invention content are also considered to fall within the protection scope of the present invention.

[0032] Example 1

[0033] A method for preparing layered calcium sulfate using phosphogypsum specifically includes the following steps:

[0034] 1) Impurity removal and purification of phosphogypsum:

[0035] Mix phosphogypsum with calcium hydroxide solution with a pH of 11 to prepare slurries with concentrations of 6%, 8%, 10%, and 12% respectively. While stirring in a stirring tank, pump the slurry into a FX75 (75 mm in diameter) hydrocyclone, set the inlet pressure to 0.15 - 0.25 MPa. After the slurry is purified and separated by the hydrocyclone, perform particle size analysis and chemical composition analysis on the products at the overflow and underflow ports. The screening mesh numbers are 65 / 100 / 200 / 325 / 400 / 500 meshes respectively. Select the products with 200 - 500 meshes and enter them into the secondary hydrocyclone. Take the product at the underflow port of the secondary hydrocyclone as purified phosphogypsum A.

[0036] 2) Dissolution of purified phosphogypsum

[0037] Weigh 160 ml (160 g) of deionized water with a measuring cylinder, weigh 0.4 g of purified phosphogypsum A, dissolve it with 160 ml of deionized water, add citric acid, stir, and adjust the pH value to 5 - 6 to remove impurity reagents (calcium hydroxide, calcium oxide). Partially dissolve the purified phosphogypsum, filter, remove the undissolved filter residue, and take the aqueous solution of purified phosphogypsum. Drop in ammonia water and adjust the pH value to 7 to remove the unreacted citric acid. Obtain aqueous solution B of purified phosphogypsum.

[0038] 3) Regulation of calcium sulfate crystal form growth

[0039] Weigh 0.004 g of the crystal growth regulator, namely sodium N-(2-aminoethyl)aminopropionate or sodium salt of N-(2-aminoethyl)aminopropionate (iron salt of sodium N-(2-aminoethyl)aminopropionate, magnesium salt of sodium N-(2-aminoethyl)aminopropionate, zinc salt of sodium N-(2-aminoethyl)aminopropionate) with an analytical balance, and add it to the purified phosphogypsum aqueous solution B. Heat it in an oil bath at 95 °C with stirring until recrystallization to obtain layered calcium sulfate. Then filter to obtain layered calcium sulfate C.

[0040] 4) Drying of layered calcium sulfate

[0041] Vacuum dry the layered calcium sulfate C in a vacuum drying oven at 80 °C for 8 hours to obtain the final product.

[0042] Example 2

[0043] Compared with Example 1, the only difference is that: weigh 0.008 g of the crystal growth regulator with an analytical balance.

[0044] Example 3

[0045] Compared with Example 1, the only difference is that: weigh 0.016 g of the crystal growth regulator with an analytical balance.

[0046] Example 4

[0047] Compared with Example 1, the only difference is that: weigh 0.02 g of the crystal growth regulator with an analytical balance.

[0048] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing layered calcium sulfate using phosphogypsum, characterized in that, The method specifically includes the following steps: (1) Impurity removal and purification of phosphogypsum: Mix phosphogypsum with calcium hydroxide to form a slurry, purify and separate it through a hydrocyclone and then screen it, select the product with a mesh size of 200 - 500, and then process the product through a secondary hydrocyclone to obtain purified phosphogypsum; The concentration of the slurry is 6% - 12%, and the inlet pressure of the hydrocyclone is 0.15 - 0.25 MPa; (2) Dissolution of phosphogypsum: Dissolve the purified phosphogypsum in water, add citric acid to adjust the pH value to 5 - 6 and add an impurity removal reagent, filter, and then drop ammonia water into the filtrate to adjust the pH value to 7 to obtain an aqueous solution of purified phosphogypsum; The mass ratio of the purified phosphogypsum to water is 1:400, and the impurity removal reagent is calcium hydroxide or calcium oxide; (3) Regulation of calcium sulfate crystal growth: Add a crystal growth regulator to the aqueous solution of purified phosphogypsum, heat and stir it in an oil bath, recrystallize and dry it to obtain the layered calcium sulfate; The crystal growth regulator is sodium N-(2-aminoethyl)aminopropionate; the sodium N-(2-aminoethyl)aminopropionate includes one or a combination of more than one of sodium N-(2-aminoethyl)aminopropionate iron, sodium N-(2-aminoethyl)aminopropionate magnesium, and sodium N-(2-aminoethyl)aminopropionate zinc; The addition amount of the crystal growth regulator is 1% - 5% of the mass of the purified phosphogypsum; The oil bath heating temperature is 95 °C, the drying temperature is 80 °C, and the drying time is 8 h.

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