A method for converting phosphogypsum into large-size calcium sulfate spherocrystals under normal pressure in aqueous phase with trace amounts of crystal stabilizer

Abstract

The application discloses a method for converting phosphogypsum into large-size calcium sulfate spherocrystals under normal-pressure water phase by using trace crystal stabilizer, and belongs to the field of chemical materials. The application aims to provide a method for effectively converting phosphogypsum into large-size calcium sulfate spherocrystals under normal-pressure water phase. The specific block copolymer of polyethylene glycol and 12-hydroxystearic acid can form effective barriers in the medium as a crystal form stabilizer, preventing the excessive growth of particles in a specific direction, so that large-size spherocrystals are obtained. The method can increase the purity, whiteness and added value of the product, improve the utilization rate of phosphogypsum, and the prepared anhydrous phosphogypsum spherocrystals have a larger size. The method provides a possibility for the sustainable development of the phosphate and compound fertilizer industry, and has the advantages of easy control of process conditions, mild reaction conditions, simple operation steps, favorable resource utilization of phosphogypsum and improved quality of the final product.

Description

Technical Field

[0001] This invention relates to the field of inorganic material preparation, and in particular to a method for preparing calcium sulfate spherulites with large grain diameters (greater than 100 micrometers) using a block copolymer of polyethylene glycol and 12-hydroxystearic acid as a crystal stabilizer. Background Technology

[0002] Calcium sulfate, as an important inorganic material, has wide applications in medicine, construction, coatings, and many other fields. However, traditional methods for preparing calcium sulfate often fail to yield spherulites with uniform, large-sized grains. Therefore, developing a method for the stable preparation of large-diameter calcium sulfate spherulites is of significant practical importance. Using a specific block copolymer of polyethylene glycol and 12-hydroxystearic acid as a crystal stabilizer in a medium can create effective steric barriers, preventing excessive particle growth in a specific direction and thus obtaining large-sized spherulites. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing calcium sulfate spherulites with a grain diameter greater than 100 micrometers by using a block copolymer of polyethylene glycol and 12-hydroxystearic acid as a crystal form stabilizer.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: By placing a purified aqueous solution of phosphogypsum in an atmospheric pressure aqueous system, a specific block copolymer of polyethylene glycol and 12-hydroxystearic acid acts as a crystal stabilizer, forming an effective potential barrier in the medium to prevent excessive particle growth in a specific direction, thus obtaining large-sized spherulites. This method can increase the purity, whiteness, and added value of the product; improve the utilization rate of phosphogypsum; produce larger anhydrous phosphogypsum spherulites; provide possibilities for the sustainable development of the phosphate compound fertilizer industry; and offers easy control of process conditions, mild reaction conditions, and simple operation steps; it is conducive to the resource utilization of phosphogypsum; this preparation technology greatly improves the quality of the final product. The beneficial effects of this invention are as follows: the method of this invention can stably prepare calcium sulfate spherulites with a grain diameter greater than 100 micrometers, which can meet the application needs of specific fields. The method of this invention is simple in steps and easy to operate and control. Attached Figure Description Figure 1 This is a SEM image of the product of Example 1 of the present invention; Figure 2 The XRD pattern of the product of Example 1 of the present invention; Detailed Implementation

[0005] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0006] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance tests in the embodiments of this application, unless otherwise specified, employ conventional testing methods in the art.

[0007] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and techniques not specifically mentioned herein refer to experimental methods and techniques commonly used by one of ordinary skill in the art. Unless otherwise specified, the methods and reagents used in the embodiments are conventional methods and reagents, respectively. It should be understood that the terminology used in this application is merely for describing particular implementation methods and is not intended to limit the content disclosed in this application.

[0008] To better illustrate the content of this application, specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0009] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0010] The present invention will be further described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the following description. Example

[0011] A method for converting phosphogypsum into large-sized calcium sulfate spherulites using a trace amount of crystal stabilizer in an aqueous phase under normal pressure, specifically includes the following steps: 1) Purification and purification of phosphogypsum: Phosphogypsum was mixed with a calcium hydroxide solution at pH 11 to prepare a 10% slurry. The slurry was pumped into an FX75 (75mm diameter) hydrocyclone while being stirred in a mixing tank. The inlet pressure was set to 0.15-0.25 MPa. After purification and separation by the hydrocyclone, the overflow and underflow products were subjected to sieve particle size analysis and chemical composition analysis. The sieve mesh sizes were 65 / 100 / 200 / 325 / 400 / 500 mesh. The 500-mesh product was selected and fed into a secondary hydrocyclone. The underflow product of the secondary hydrocyclone was used as purified phosphogypsum A.

[0012] 2) Purification of phosphogypsum dissolution Weigh 0.1 L (100 g) of deionized water using a graduated cylinder. Weigh 0.2 g of purified phosphogypsum A and dissolve it in 0.1 L of deionized water. Add sulfuric acid, stir, and adjust the pH to 5-6 to remove impurities (calcium hydroxide, calcium oxide). Partially dissolve the purified phosphogypsum, filter, remove undissolved residue, and take the purified phosphogypsum aqueous solution. Add ammonia water dropwise to adjust the pH to 7 and remove unreacted sulfuric acid. This yields purified phosphogypsum aqueous solution B.

[0013] 3) Regulation of calcium sulfate spherulite growth Take 0.0002 mol of a block copolymer of polyethylene glycol and 12-hydroxystearic acid as crystal growth stabilizers, add it to purified phosphogypsum aqueous solution B, heat in an oil bath at 98°C, stir, and wait for recrystallization. After filtration, obtain calcium sulfate spherulites with a crystal diameter greater than 100 micrometers.

[0014] 4) Drying of high aspect ratio anhydrous calcium sulfate whiskers The calcium sulfate spheroids were dried in a vacuum drying oven at 80°C for 8 hours to obtain the final product.

Claims

1. A method for converting phosphogypsum into large-sized calcium sulfate spherulites using a trace amount of crystal stabilizer in an aqueous phase under normal pressure, characterized in that... The steps include the following: a) Purification of phosphogypsum: Phosphogypsum was mixed with calcium hydroxide solution at pH 11 to prepare a slurry with a concentration of 10%. The slurry was purified and separated by hydrocyclone under an inlet pressure of 0.15-0.25 MPa. The product with a sieve mesh size of 500 mesh was selected as purified phosphogypsum A. b) Dissolving purified phosphogypsum: Dissolve purified phosphogypsum A in deionized water, adjust the pH to 5-6 to remove impurities, filter to obtain purified phosphogypsum aqueous solution, then adjust the pH to 7 to remove unreacted sulfuric acid, to obtain purified phosphogypsum aqueous solution B. c) Regulation of calcium sulfate spherulite growth: Add a block copolymer of polyethylene glycol and 12-hydroxystearic acid (relative to purified phosphogypsum aqueous solution B) at a concentration of 0.002-0.003 mol / L to purified phosphogypsum aqueous solution B, heat and stir at 95°C, and recrystallize to obtain calcium sulfate spherulites; d) Drying of calcium sulfate spherulites: Calcium sulfate spherulites were dried in a vacuum drying oven at 80°C for 8 hours to obtain the final product.

2. The method according to claim 1, characterized in that, The hydrocyclone is an FX75 hydrocyclone with a diameter of 75mm.

3. The method according to claim 1, characterized in that, The sieve mesh sizes are 65 / 100 / 200 / 325 / 400 / 500 mesh.

4. The method according to claim 1, characterized in that, The purified phosphogypsum A is derived from the underflow product of the secondary hydrocyclone.

5. The method according to claim 1, characterized in that, The drying temperature in the vacuum drying oven is 80℃, and the drying time is 8 hours.

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