阅读说明：本技术 一种工业固废石膏的纯化及制备硫酸钙晶须方法 (Method for purifying industrial solid waste gypsum and preparing calcium sulfate whisker ) 是由 张安将 杨路峰 余金海 于 2021-07-09 设计创作，主要内容包括：本发明公开了一种工业固废石膏的纯化及制备硫酸钙晶须方法,通过将多种工业固废石膏在盐酸中提纯得到高纯石膏,然后将提纯的石膏在一定的溶剂环境下,并在常压,＜100℃的温和反应条件下,混合得到初级滤饼、成品滤饼干燥后得到二水硫酸钙晶体,再和盐酸与醇的混合溶液混合,最终诱导结晶得到高纯度的硫酸钙晶须材料。其中提纯的盐酸与制备晶须所需的溶剂皆可循环使用,不产生二次污染,利于规模化生产,符合循环经济理念。本发明用工业固废石膏来替代日益减少的高品位石膏资源制备硫酸钙晶须,可减少对天然优质石膏开采,且本发明方法中各原料均十分易得,有利于降低生产成本,具有良好的经济效益和广阔的工业化应用前景。(The invention discloses a method for purifying industrial solid waste gypsum and preparing calcium sulfate whisker, which comprises the steps of purifying various industrial solid waste gypsums in hydrochloric acid to obtain high-purity gypsum, mixing the purified gypsum in a certain solvent environment under mild reaction conditions of normal pressure and less than 100 ℃ to obtain a primary filter cake, drying a finished filter cake to obtain calcium sulfate dihydrate crystal, mixing the calcium sulfate dihydrate crystal with a mixed solution of hydrochloric acid and alcohol, and finally inducing crystallization to obtain the high-purity calcium sulfate whisker material. The purified hydrochloric acid and the solvent required by preparing the crystal whisker can be recycled, secondary pollution is not generated, large-scale production is facilitated, and the concept of recycling economy is met. The invention uses industrial solid waste gypsum to replace increasingly reduced high-grade gypsum resources to prepare the calcium sulfate whisker, can reduce the exploitation of natural high-quality gypsum, has easily obtained raw materials, is favorable for reducing the production cost, and has good economic benefit and wide industrialized application prospect.)

1. A method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers is characterized by comprising the following steps: comprises the following steps

A1. Drying and crushing industrial solid waste gypsum to obtain powder for later use;

A2. mixing the powder obtained in the step A1 with hydrochloric acid, stirring, heating, and continuing to react for 0-2 hours after the temperature of the mixture is raised to 70-90 ℃;

A3. filtering the suspension obtained in the step A2 while the suspension is hot, aging the obtained filtrate for 0.5-6 h at room temperature, and collecting the obtained filter residues for calcination treatment to prepare a vitreous body for use as a building material;

A4. filtering the solid-liquid mixture obtained in the step A3 to obtain a primary filter cake, washing the primary filter cake to obtain a finished filter cake, drying the finished filter cake to obtain calcium sulfate dihydrate crystals, and returning the filtrate to the step A2 to continuously dissolve the solid waste gypsum powder;

A5. mixing the calcium sulfate dihydrate crystal obtained in the step A4 with a mixed solution of hydrochloric acid and alcohol, adding a crystal form regulating agent and a surface modifier, and stirring and reacting the mixture for 1-2 hours under the conditions of normal pressure, 80-100 ℃ and a stirring speed of 200-600 r/min to prepare slurry;

A6. and (3) filtering the slurry obtained in the step A5 while the slurry is hot, filtering, washing and drying the obtained filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtered filtrate to the step A5 to continuously react with the raw material calcium sulfate dihydrate to prepare the calcium sulfate whisker.

2. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step A1, the industrial solid waste gypsum is one of phosphogypsum, salt gypsum, desulfurized gypsum, fluorgypsum, titanium gypsum or citric acid gypsum.

3. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step A2, the mass fraction of the hydrochloric acid is 6-15%; the solid-to-liquid ratio (kg/L) of the solid waste gypsum powder to the hydrochloric acid is 1: (12-20); the stirring speed is 200-600 r/min.

4. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: and repeatedly washing the primary filter cake for three times by hot water, and performing forced air drying on the finished filter cake for 1-6 hours at the temperature of 40-80 ℃ to obtain calcium sulfate dihydrate crystals.

5. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step A5, the alcohol is one or a combination of two of ethylene glycol, glycerol, 1, 4-butanediol, 1, 5-pentanediol, diethylene glycol, triethylene glycol and tetraethylene glycol.

6. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step a5, the volume ratio of hydrochloric acid to alcohol in the mixed solution of hydrochloric acid and alcohol is 1: (1-4); the mass fraction of the hydrochloric acid is 3-15%; the solid-to-liquid ratio (kg/L) of the calcium sulfate dihydrate crystal to the mixed solution of hydrochloric acid and alcohol is 1: (3-10).

7. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step A5, the crystal form regulating agent is magnesium chloride hexahydrate, anhydrous magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium oxide or magnesium hydroxide, wherein the crystal form regulating agent accounts for 0.5-1 wt% of the input amount of the calcium sulfate dihydrate crystal.

8. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: in the step A5, the surface modifier is stearic acid, oleic acid, palmitic acid, sodium stearate, sodium oleate or sodium palmitate, wherein the surface modifier accounts for 0.5-2 wt% of the added amount of the calcium sulfate dihydrate crystal.

9. The method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers as recited in claim 1, wherein: and in the step A6, repeatedly washing the primary filter cake with hot water for three times, and then carrying out forced air drying on the finished filter cake for 1-6 h at the temperature of 40-80 ℃ to obtain the finished product of the calcium sulfate whisker.

Technical Field

The invention relates to a comprehensive utilization technology of industrial solid waste resources, in particular to a method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers, wherein the industrial solid waste gypsum is utilized.

Background

Calcium sulfate whisker as new generation composite material additive is one kind of environment friendly inorganic fiber material, and has the advantages of both superfine inorganic filler and reinforcing fiber. The preparation of the calcium sulfate whisker from the industrial solid waste gypsum is also an effective way for changing waste into valuable and improving the additional value of industrial waste. At present, natural gypsum is usually directly exploited for preparing the calcium sulfate whiskers, but in the long run, the non-renewable gypsum resource is less and less, and even exhausted; therefore, how to research the preparation of the calcium sulfate whisker with high added value by utilizing the industrial solid waste gypsum has important significance.

About billions of tons of industrial solid waste gypsum are discharged at present in China every year, so that a large amount of discharged gypsum not only occupies a large amount of land, but also causes great environmental pollution due to harmful impurities, thereby causing great burden to enterprises and great harm to the environment. The effective utilization of the industrial solid waste gypsum is improved, the capital consumed by stacking can be reduced, the occupied land and the pollution to the environment are reduced, and the exploitation amount of the natural gypsum can be reduced, so that the ecological environment is better protected.

The calcium sulfate whisker prepared by taking industrial solid waste gypsum as a raw material is used as an additive to be added into a high polymer material, can enhance various performances such as heat resistance, mechanical property and the like of a polymer, and has wide application in a plurality of civil industrial fields such as aerospace and the like. And may also be added to the plastic rubber to improve the bending strength, tensile strength, heat distortion temperature, elastic modulus, etc. of the composite material. Because of its excellent performance, it can also be added into building material, friction material and heat-insulating material instead of asbestos. And can also be used as a reinforcing filler in the industries of adhesives, resin matrix composite materials and the like.

The calcium sulfate whisker material has the advantages of excellent performance, low price, environmental protection and the like, and has wide application and market prospect. The calcium sulfate crystal whisker is prepared by utilizing industrial solid waste gypsum, so that the solid waste can obtain high-end functional materials.

The research of producing calcium sulfate crystal whisker by using industrial solid waste gypsum is available in China. Such as phosphogypsum which is a byproduct in phosphate fertilizer industry, citric acid gypsum discharged in citric acid production, desulfurized gypsum produced in flue gas desulfurization industry, fluorgypsum produced in the process of preparing hydrogen fluoride by decomposing fluorite with sulfuric acid, and salt gypsum produced in other chemical engineering production, etc. can be considered to be used for preparing calcium sulfate whisker.

The patent CN1477242A takes natural or chemical gypsum as a raw material, and calcium sulfate whiskers are prepared through processes of crushing, size mixing, hydrothermal reaction and the like, and the process has the defects that a polyvinyl alcohol solution is unevenly coated on the surfaces of the whiskers in the surface treatment process, the mass production cannot be realized, and the like.

Patent CN1584130A uses excessive high-concentration phosphoric acid to perform acid leaching chemical reaction with phosphorite, separates liquid phase and filters to obtain phosphoric acid leaching solution containing phosphoric acid and calcium ions, and then adds high-concentration sulfuric acid solution to react and precipitate calcium sulfate dihydrate whisker. For the technology, the formation process of the calcium sulfate whisker can be completed only by simultaneously preparing high-concentration phosphoric acid and sulfuric acid, and the method is only suitable for the industrial production process of phosphoric acid or a phosphorus-rich ore area.

In patent CN101311355A, phosphogypsum is used as a raw material, and a calcium sulfate whisker product with controllable diameter and length is prepared through synthesis reaction, filtration, heating dissolution, hot filtration and cooling crystallization, but in the method, a pH regulator is required to be added to maintain the pH value of the solution to be 7.5-12, magnesium nitrate powder is also required to be added as a crystal growth substance, the required pretreatment steps are more, the temperature is more than 100 ℃, and the regulation difficulty and the cost are increased.

Patent CN101671848A proposes a preparation method of anhydrous calcium sulfate whisker with high length-diameter ratio, which undergoes the processes of size mixing, hydrothermal reaction, calcination treatment and the like, and relates to three levels of temperature, low temperature, medium temperature and high temperature, the whole process has high energy consumption, needs a large amount of surfactant, has complex preparation process, and is not beneficial to large-scale popularization and application.

The patent CN110541188A adopts calcium sulfate dihydrate as a raw material, and the calcium sulfate hemihydrate crystal whisker with high length-diameter ratio is prepared through processes of grinding, acid leaching impurity removal, oxidation impurity removal, hydrothermal reaction and the like.

In a word, the traditional calcium sulfate whisker production process has the problems of high raw material price, difficult wastewater treatment, high energy consumption (high temperature and high pressure) and the like, so that the prepared calcium sulfate whisker is expensive, and a great obstacle factor is caused for large-scale application of the calcium sulfate whisker.

Disclosure of Invention

The invention provides a method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers, which aims to solve the problems that the cost of raw materials is high, waste water is difficult to treat and energy consumption is high in the existing calcium sulfate whisker production process, so that the prepared calcium sulfate whiskers are expensive, and the current situations of great obstacles and the like are caused for large-scale application of the calcium sulfate whiskers.

The invention adopts the following specific technical scheme for solving the technical problems: a method for purifying industrial solid waste gypsum and preparing calcium sulfate whiskers is characterized by comprising the following steps: comprises the following steps

A1. Drying and crushing industrial solid waste gypsum to obtain powder for later use;

A2. mixing the powder obtained in the step A1 with hydrochloric acid, stirring, heating, and continuing to react for 0-2 hours after the temperature of the mixture is raised to 70-90 ℃;

A3. filtering the suspension obtained in the step A2 while the suspension is hot, aging the obtained filtrate for 0.5-6 h at room temperature, and collecting the obtained filter residues for calcination treatment to prepare a vitreous body for use as a building material;

A4. filtering the solid-liquid mixture obtained in the step A3 to obtain a primary filter cake, washing the primary filter cake to obtain a finished filter cake, drying the finished filter cake to obtain calcium sulfate dihydrate crystals, and returning the filtrate to the step A2 to continuously dissolve the solid waste gypsum powder;

A5. mixing the calcium sulfate dihydrate crystal obtained in the step A4 with a mixed solution of hydrochloric acid and alcohol, adding a crystal form regulating agent and a surface modifier, and stirring and reacting the mixture for 1-2 hours under the conditions of normal pressure, 80-100 ℃ and a stirring speed of 200-600 r/min to prepare slurry;

A6. and (3) filtering the slurry obtained in the step A5 while the slurry is hot, filtering, washing and drying the obtained filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtered filtrate to the step A5 to continuously react with the raw material calcium sulfate dihydrate to prepare the calcium sulfate whisker.

In the step A1, the industrial solid waste gypsum is one of phosphogypsum, salt gypsum, desulfurized gypsum, fluorgypsum, titanium gypsum or citric acid gypsum.

In the step A2, the mass fraction of the hydrochloric acid is 6-15%; the solid-to-liquid ratio (kg/L) of the solid waste gypsum powder to the hydrochloric acid is 1: (12-20); the stirring speed is 200-600 r/min. And in the step A4, repeatedly washing the primary filter cake with hot water for three times, and then drying the finished filter cake by blowing air at 40-80 ℃ for 1-6 hours to obtain calcium sulfate dihydrate crystals.

In the step A5, the alcohol is one or a combination of two of ethylene glycol, glycerol, 1, 4-butanediol, 1, 5-pentanediol, diethylene glycol, triethylene glycol and tetraethylene glycol; the volume ratio of the hydrochloric acid solution to the alcohol in the mixed solution of the hydrochloric acid and the alcohol is 1: (1-4); the mass fraction of the hydrochloric acid is 3-15%; the solid-to-liquid ratio (kg/L) of the calcium sulfate dihydrate crystal to the mixed solution of hydrochloric acid and alcohol is 1: (3-10).

In the step A5, the crystal form regulating agent is magnesium chloride hexahydrate, anhydrous magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium oxide or magnesium hydroxide, wherein the crystal form regulating agent accounts for 0.5-1 wt% of the input amount of the calcium sulfate dihydrate crystal; the surface modifier is stearic acid, oleic acid, palmitic acid, sodium stearate, sodium oleate or sodium palmitate, wherein the surface modifier accounts for 0.5-2 wt% of the input amount of the calcium sulfate dihydrate crystal.

And in the step A6, repeatedly washing the primary filter cake with hot water for three times, and then carrying out forced air drying on the finished filter cake for 1-6 h at the temperature of 40-80 ℃ to obtain the finished product of the calcium sulfate whisker.

The invention has the beneficial effects that: the liquid phase is reused in the production process, secondary pollution is avoided, energy is saved, emission is reduced, the product purity is higher, the performance is excellent, reaction reagents are basically not consumed, the calcium sulfate whisker with regular appearance can be prepared under the conditions of normal pressure and temperature (lower than 100 ℃), the requirements on the grade and reaction conditions of industrial solid waste gypsum are low, resource utilization can be achieved to a greater extent, and industrial scale production is facilitated. The crystal form regulating agent and the surface modifier, namely the modifier and the crystal modifier can achieve zero loss; the popularization of the invention is beneficial to the development of low-carbon circular economy and conforms to the strategy of sustainable development.

Description of the drawings:

the accompanying drawings are included to provide a further understanding of the claimed subject matter and are incorporated in and constitute a part of this specification, illustrate embodiments of the subject matter and together with the description serve to explain the principles of the subject matter and not to limit the subject matter.

Fig. 1 is a scanning electron micrograph of the calcium sulfate whiskers prepared in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer and to make the skilled in the art better understand the present invention, the present invention is further illustrated by the following examples, which are only used for illustrative purposes and do not limit the scope of the present invention. The test methods in the following examples, which are not specified under specific conditions, are generally carried out under conventional conditions.

Example 1:

drying and crushing the phosphogypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to the solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 6 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is raised to 70 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into a vitreous body for serving as a building material. And filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, wherein the filtrate can be returned to dissolve the phosphogypsum again. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 3 percent, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.6 mu m, the average length is 90 mu m, and the length-diameter ratio is 56.

Example 2:

drying and crushing the phosphogypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to the solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. And filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, wherein the filtrate can be returned to dissolve the phosphogypsum again. Then put this in

Mixing the calcium sulfate dihydrate crystal with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. It is composed of

The mass fraction of the hydrochloric acid is 4%, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.5 mu m, the average length is 71 mu m, and the length-diameter ratio is 47.

Example 3:

drying and crushing the phosphogypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to the solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. And filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, wherein the filtrate can be returned to dissolve the phosphogypsum again. Then mixing the calcium sulfate dihydrate crystal with a mixed solution of hydrochloric acid, glycerol and diethylene glycol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4%, the volume ratio of the mixed solution of the hydrochloric acid and the alcohol is 1:4, and the volume ratio of the glycerol to the diglycol in the mixed solution of the alcohol is 1: 1. After 0.5wt% of magnesium sulfate and 1wt% of stearic acid are added into the mixed solution, the mixed solution is stirred at the rotating speed of 300 r/min and gradually heated, and after the temperature is raised to 85 ℃, the mixed solution is continuously stirred and reacts for 1 hour. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.4 mu m, the average length is 83 mu m, and the length-diameter ratio is 59.

Example 4:

drying and crushing the salt gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 6 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is raised to 70 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into a vitreous body for serving as a building material. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to redissolve the salt gypsum. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4 percent, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.5 mu m, the average length is 65 mu m, and the length-diameter ratio is 43.

Example 5:

drying and crushing the salt gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to redissolve the salt gypsum. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4 percent, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.5 mu m, the average length is 82 mu m, and the length-diameter ratio is 55.

Example 6:

drying and crushing the salt gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to redissolve the salt gypsum. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid, glycerol and triethylene glycol according to the solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4%, the volume ratio of the mixed solution of the hydrochloric acid and the alcohol is 1:4, and the volume ratio of the glycerol to the triethylene glycol in the mixed solution of the alcohol is 1: 1. After 0.5wt% of magnesium sulfate and 1wt% of stearic acid are added into the mixed solution, the mixed solution is stirred at the rotating speed of 300 r/min and gradually heated, and after the temperature is raised to 85 ℃, the mixed solution is continuously stirred and reacts for 1 hour. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.70 mu m, the average length is 75 mu m, and the length-diameter ratio is 44.

Example 7:

drying and crushing the desulfurized gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 6 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is raised to 70 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into a vitreous body for serving as a building material. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to dissolve the desulfurized gypsum again. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4 percent, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.5 mu m, the average length is 60 mu m, and the length-diameter ratio is 40.

Example 8:

drying and crushing the desulfurized gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to dissolve the desulfurized gypsum again. Then, the calcium sulfate dihydrate crystal is mixed with a mixed solution of hydrochloric acid and glycerol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 4 percent, and the volume ratio of the hydrochloric acid to the glycerol is 1: 4. After adding 0.5wt% of magnesium sulfate and 0.5wt% of stearic acid into the mixed solution, stirring the mixed solution at the rotating speed of 300 r/min and gradually heating, and continuing stirring and reacting for 1h after the temperature is raised to 85 ℃. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The prepared calcium sulfate crystal whisker is flat

Average diameter of 1.7 μm, average length of 78 μm, and aspect ratio of 46.

Example 9:

drying and crushing the desulfurized gypsum to obtain a dry material, and then mixing the dry material with hydrochloric acid according to a solid-to-liquid ratio (kg/L) of 1: 12. Wherein the mass fraction of the hydrochloric acid is 9 percent. And then stirring the mixture at the rotating speed of 300 r/min and gradually heating, continuing stirring and reacting for 10min after the temperature is increased to 90 ℃, filtering while hot, standing the filtrate at room temperature for 2h, and collecting filter residues to sinter the filter residues into glass bodies for serving as building materials. Filtering, washing and drying the solid-liquid mixture after standing to obtain calcium sulfate dihydrate crystals, and returning the filtrate to dissolve the desulfurized gypsum again. Then mixing the calcium sulfate dihydrate crystal with a mixed solution of hydrochloric acid, glycerol and diethylene glycol according to a solid-to-liquid ratio (kg/L) of 1: 3. Wherein the mass fraction of the hydrochloric acid is 5%, the volume ratio of the mixed solution of the hydrochloric acid and the alcohol is 1:4, and the volume ratio of the glycerol to the diglycol in the mixed solution of the alcohol is 1: 1. After 0.5wt% of magnesium sulfate and 1wt% of stearic acid are added into the mixed solution, the mixed solution is stirred at the rotating speed of 300 r/min and gradually heated, and after the temperature is raised to 85 ℃, the mixed solution is continuously stirred and reacts for 1 hour. And then filtering while hot, filtering, washing and drying the filter cake to obtain a finished product of calcium sulfate whisker, and returning the filtrate for reuse. The average diameter of the prepared calcium sulfate whisker is 1.7 mu m, the average length is 88 mu m, and the length-diameter ratio is 52.

The foregoing summary and structure are provided to explain the principles, general features, and advantages of the product and to enable others skilled in the art to understand the invention. The foregoing examples and description have been presented to illustrate the principles of the invention and are intended to provide various changes and modifications within the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.