A method for preparing calcium sulfate dihydrate whiskers using carbide slag.

Abstract

This invention belongs to the field of inorganic material crystal preparation technology, specifically relating to a method for preparing calcium sulfate dihydrate whiskers using carbide slag. The method includes the following steps: dissolving an organic acid salt in water to prepare a solution; adding carbide slag powder and reacting, followed by solid-liquid separation to obtain a calcium ion filtrate; adding dilute sulfuric acid dropwise to the filtrate under constant temperature stirring to generate a whisker-containing slurry; aging the slurry at a constant temperature, followed by filtration, washing, and drying to obtain the calcium sulfate dihydrate whisker product. The organic acid salt is selected from betaine hydrochloride, glucosamine hydrochloride, or lysine hydrochloride, which acts as a "calcium ion carrier" and "morphology regulator" in the reaction, and can achieve in-situ regeneration and recycling. By optimizing key parameters such as reaction temperature, reaction time, and aging time, this invention can stably prepare calcium sulfate dihydrate whiskers with an aspect ratio of 75:1. This method uses industrial waste carbide slag as the main raw material, achieving high-value utilization of waste, and the process is green and recyclable.

Description

Technical Field

[0001] This invention belongs to the field of inorganic material crystal preparation technology, specifically relating to a calcium sulfate dihydrate whisker prepared using carbide slag and its preparation method. Background Technology

[0002] Calcium sulfate whiskers (calcium sulfate dihydrate, CaSO4·2H2O) are high-performance fibrous reinforcing materials widely used in polymer composites. Traditional preparation methods often use high-purity gypsum as raw material, which suffers from high raw material costs or complex processes (such as hydrothermal methods) and high energy consumption.

[0003] Meanwhile, calcium carbide slag, as an industrial waste rich in calcium hydroxide, is produced in huge quantities and faces severe environmental disposal pressures. Using it as a cheap calcium source to prepare high-value products is an ideal path to achieve resource recycling. To this end, some studies have attempted to use calcium carbide slag to prepare calcium sulfate whiskers, but they generally face a fundamental technical bottleneck: it is difficult to effectively control the crystal morphology. The products obtained are mostly particles or short rod-shaped crystals with very low aspect ratios, which seriously limits their reinforcing effectiveness.

[0004] Methods for preparing calcium sulfate dihydrate whiskers include atmospheric acidification, hydrothermal synthesis, ion exchange, and microemulsion methods, with atmospheric acidification and hydrothermal synthesis being the most commonly used. Atmospheric acidification is a unit operation technique that uses the chemical properties of acids (such as sulfuric acid, hydrochloric acid, or organic acids) to adjust the pH of the system under standard atmospheric pressure, thereby extracting, purifying, converting, or removing impurities from the target substance. This method is simple and produces products with high purity and good dispersibility. However, it has the following drawbacks: (1) Under no external control conditions, calcium sulfate crystals tend to grow isotropically and cannot spontaneously form whiskers with high aspect ratio; (2) Although adding organic regulators is a common approach, most methods treat regulators as disposable consumables and fail to design a recycling mechanism for them in the reaction system, which increases costs and environmental burden.

[0005] Therefore, there is an urgent need in this field to develop a novel preparation method specifically for calcium carbide slag raw materials. This method not only requires the screening of highly efficient morphology modifiers, but more importantly, it requires the construction of a green reaction system that enables the regeneration of the modifiers, ultimately achieving the goal of stable, efficient, and controllable preparation of high aspect ratio calcium sulfate dihydrate whiskers from calcium carbide slag. Summary of the Invention

[0006] To address the problems of low aspect ratio, difficulty in controlling morphology, and insufficient green and economical processes in the preparation of calcium sulfate whiskers using carbide slag in existing technologies, this invention provides a method for the efficient and controllable preparation of high aspect ratio dihydrate calcium sulfate whiskers using carbide slag as raw material by introducing specific organic acid salt crystallizing agents and optimizing key process parameters.

[0007] To achieve the above objectives, the present invention provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Dissolve the organic acid salt in water to prepare a solution; S2. Heat the organic acid salt solution to 70°C, slowly add the carbide slag powder to the organic acid salt solution obtained in S1, stir and react, and after the reaction is completed, perform solid-liquid separation to obtain a filtrate rich in calcium ions. S3. Under constant temperature and stirring conditions, dilute sulfuric acid is added dropwise to the filtrate obtained in S2 to react and obtain a slurry containing calcium sulfate dihydrate whiskers. S4. The slurry obtained in S3 is kept at a certain temperature for aging, and then filtered, washed and dried to obtain calcium sulfate dihydrate whisker product.

[0008] Furthermore, the organic acid salt is a hydrochloride that regulates crystal growth, specifically selected from one of betaine hydrochloride, glucosamine hydrochloride, or lysine hydrochloride.

[0009] Preferably, the organic acid salt is betaine hydrochloride, and when betaine hydrochloride is used, the whiskers have the highest aspect ratio.

[0010] Furthermore, the concentration of organic acid salts in S1 is 153.6 g / L.

[0011] Furthermore, the reaction temperature in S3 is between 70°C and 90°C. Within this range, the whisker aspect ratio increases significantly with increasing temperature.

[0012] Preferably, the reaction temperature in S3 is 90°C.

[0013] Furthermore, the reaction time in S3 is 60-180 min. Within this range, extending the reaction time is beneficial for obtaining whiskers with a higher aspect ratio. Preferably, it is 180 min.

[0014] Furthermore, the concentration of dilute sulfuric acid in S3 is 1.6 mol / L.

[0015] Furthermore, the aging time in S4 is 60-180 minutes. Within this range, extending the aging time can further improve the whisker aspect ratio. The optimal value is 180 minutes.

[0016] The present invention also provides calcium sulfate dihydrate whiskers prepared by the above preparation method.

[0017] Furthermore, the aspect ratio of calcium sulfate dihydrate whiskers is 75:1.

[0018] The core of this invention lies in the addition of organic acid salts. These organic acid salts act simultaneously as a "calcium ion carrier" and a "crystal morphology regulator" in the system, achieving in-situ regeneration and recycling. The mechanism is as follows: the organic acid salts neutralize with calcium hydroxide in the carbide slag, generating betaine and calcium chloride solution. Calcium ions enter the solution, while insoluble impurities are filtered out. Calcium ions in the filtrate combine with added sulfate ions to form calcium sulfate dihydrate whiskers, simultaneously releasing hydrochloric acid. The newly generated hydrochloric acid immediately combines with free betaine in the solution to reform betaine hydrochloride. Therefore, theoretically, the organic acid salts are not consumed in the entire process, forming a closed loop of "extraction-precipitation-regeneration." After filtering out the whisker product, the betaine hydrochloride in the mother liquor can be recovered and used to treat the next batch of carbide slag, achieving the recycling of the medium.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: By selecting optimal crystallizing agents and precisely controlling process parameters, this invention can stably prepare high-quality calcium sulfate dihydrate whiskers with aspect ratios as high as 25:1 to 75:1, which is significantly better than the granular products with an aspect ratio of about 5:1 that can only be obtained without adding crystallizing agents, greatly enhancing its application value as a reinforcing material.

[0020] Using industrial waste carbide slag as the main raw material, the high-value utilization of solid waste has been realized, production costs have been reduced, and significant environmental and economic benefits have been achieved.

[0021] The additive organic acid salts of the present invention can be regenerated in situ and recycled in the reaction system, which greatly reduces chemical consumption and waste emissions, and the process flow complies with the principles of green chemistry. Attached Figure Description

[0022] Figure 1 A microscope image of the product prepared in Example 7 of this invention; Figure 2 The X-ray powder diffraction patterns are of the products prepared in Examples 1, 2, 3, 4, and 5 of this invention. Detailed Implementation

[0023] Example 1

[0024] This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 70℃, the reaction time is 60 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 60 minutes, filter and dry it to obtain the product.

[0025] Example 2 This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 80℃, the reaction time is 60 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 60 minutes, filter and dry it to obtain the product.

[0026] Example 3 This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 60 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 60 minutes, filter and dry it to obtain the product.

[0027] Examples 1-3 demonstrate the key effect of reaction temperature on the aspect ratio of calcium sulfate dihydrate whiskers prepared from carbide slag, as shown in the XRD patterns. Figure 2As shown in Table 1, the aspect ratio results are as follows. Under the premise that all other conditions (betaine hydrochloride dosage, carbide slag dosage, sulfuric acid dosage, reaction time, stirring and heat preservation parameters) are exactly the same, by gradually increasing the reaction temperature from 70℃ (Example 1) to 80℃ (Example 2) and 90℃ (Example 3), the aspect ratio of the product whiskers showed a significant and regular increase, reaching 25:1, 30:1, and 40:1, respectively. This indicates that within the temperature range studied in the experiment, increasing the reaction temperature can effectively promote the preferential growth of crystals along the one-dimensional direction, thereby obtaining calcium sulfate dihydrate whiskers with a more slender morphology and a higher aspect ratio, which is a key control parameter for optimizing the product morphology.

[0028] If the reaction temperature continues to rise, the aspect ratio of the whiskers will increase with increasing temperature below 100℃, but above 100℃, a change in crystal form will begin to occur. Increasing the temperature beyond 90℃ will promote whisker growth to some extent, but the increase in aspect ratio is limited. When the reaction system temperature exceeds 100℃, calcium sulfate dihydrate will begin to dehydrate, transforming into calcium sulfate hemihydrate. It is generally believed that the product is calcium sulfate dihydrate whiskers in the temperature range below 100℃; while in the range of 130-160℃, calcium sulfate hemihydrate whiskers will form in large quantities. In the betaine hydrochloride system, to prepare calcium sulfate dihydrate whiskers with a high aspect ratio, the reaction temperature should not exceed approximately 100℃.

[0029] Table 1. Aspect Ratio Test Results of Calcium Sulfate Whiskers in Examples 1-3 Example 1 25：1 Example 2 30：1 Example 3 40：1 Example 4

[0030] This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 120 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 60 minutes, filter and dry it to obtain the product.

[0031] Example 5 This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 60 minutes, filter and dry it to obtain the product.

[0032] The main difference between Examples 3-5 is that the reaction times of dilute sulfuric acid and filtrate in step (3) are 60, 120, and 180 minutes, respectively, and the aspect ratios of the resulting products are increased to 40:1, 50:1, and 60:1, respectively. The XRD values ​​obtained in Examples 3-5 are as follows: Figure 2 As shown in Table 1, the aspect ratio results are shown in Table 2. This indicates that, under the same reaction temperature, stirring speed, and raw material ratio, appropriately extending the sulfuric acid titration reaction time helps to obtain calcium sulfate dihydrate whiskers with a higher aspect ratio.

[0033] If the reaction time is extended further, whisker growth will slow down, and the aspect ratio will reach a peak before changing, potentially leading to a decrease in aspect ratio or even a change in crystal form. The reaction time in this experiment represents the theoretically rapid axial growth period of the whiskers. However, as the whiskers grow, the concentrations of calcium and sulfate ions in the solution gradually decrease, weakening the driving force for crystal growth and slowing the rate of increase in aspect ratio. Excessively extending the reaction time may result in a decrease in aspect ratio. Due to the high surface energy of the whiskers, dissolution and recrystallization will occur to reduce the total surface energy, causing the aspect ratio to decrease instead of increase, and even leading to defects such as surface roughness, bifurcation, and agglomeration in the crystals.

[0034] Table 2. Aspect Ratio Test Results of Calcium Sulfate Whiskers in Examples 3-5 Example 3 40：1 Example 4 50：1 Example 5 60：1 Example 6

[0035] This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, slowly add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 120 minutes, filter and dry it to obtain the product.

[0036] Example 7 This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 15.36g of betaine hydrochloride and dissolve it in 100mL of water to obtain a betaine hydrochloride solution; S2. Heat the betaine hydrochloride solution to 70°C, add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 180 minutes, filter and dry it to obtain the product.

[0037] Examples 5-7 focused on investigating the effect of holding time on whisker morphology. A microscopic image of the product obtained in Example 7 is shown below. Figure 1 As shown in Table 3, under the premise that other conditions are kept completely consistent, by extending the holding time of the slurry at 90℃, the aspect ratio of the product significantly increased from 60:1 to 75:1. This indicates that after the sulfuric acid dropwise reaction is completed, extending the holding time is beneficial for the crystals to continue to dissolve and recrystallize in the solution, promoting the axial growth of the crystals, thereby obtaining calcium sulfate dihydrate whiskers with a longer aspect ratio.

[0038] If the holding time is extended further, the aspect ratio of the whiskers will continue to increase, but the subsequent increase becomes very slow. If the holding time is too long, no growth will occur. In the examples of this experiment, it was found that when the holding time increased from 1 hour to 2 hours, the aspect ratio increased by 10, while when the holding time increased from 2 hours to 3 hours, the aspect ratio only increased by 5. This pattern indicates that as the holding time increases, the aspect ratio increases slowly, but if the time is too long, the growth shifts to the radial direction, leading to an increase in crystal diameter and a decrease in the whisker aspect ratio. If the radial growth rate of the crystal exceeds the axial growth rate, the aspect ratio will stop increasing and begin to decline after reaching a peak.

[0039] Table 3. Aspect Ratio Test Results of Calcium Sulfate Whiskers in Examples 5-7 Example 5 60：1 Example 6 70：1 Example 7 75：1 Example 8

[0040] This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 21.56g of glucosamine hydrochloride and dissolve it in 100mL of water to obtain glucosamine hydrochloride solution; S2. Heat the glucosamine hydrochloride solution to 70°C, add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 180 minutes, filter and dry it to obtain the product.

[0041] Example 9 This embodiment provides a method for preparing calcium sulfate dihydrate whiskers from carbide slag, comprising the following steps: S1. Weigh 18.27g of lysine hydrochloride and dissolve it in 100mL of water to obtain a lysine hydrochloride solution; S2. Heat the lysine hydrochloride solution to 70°C, add 3.7g of carbide slag powder and stir to react. After the reaction, perform solid-liquid separation by vacuum filtration to obtain the filtrate. S3. Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. S4. After heating and holding the slurry for 180 minutes, filter and dry it to obtain the product.

[0042] Examples 7-9 primarily investigated the effects of different types of organic acid salt additives on the preparation of calcium sulfate dihydrate whiskers from calcium carbide slag. The results are shown in Table 4. Under the same calcium carbide slag dosage, sulfuric acid addition conditions, and holding time, the type of organic acid salt additive was the decisive factor affecting the final aspect ratio of the calcium sulfate dihydrate whiskers. Specifically, the highest aspect ratio (75:1) was obtained when using betaine hydrochloride, while the aspect ratios of the products obtained from glucosamine hydrochloride and lysine hydrochloride decreased sequentially (65:1 and 60:1, respectively).

[0043] In this system, the role of hydrochloride is to provide an acidic environment and ensure that the additive exists in a protonated form. The final crystal regulation effect is determined by the structure of the organic part of the additive. This fully demonstrates the decisive role of functional group type, spatial arrangement, and molecular rigidity in crystal morphology regulation. While the sugar ring of glucosamine and its monoamine act as template agents, the flexible diamine chain of lysine is closer to that of ordinary amino acid template agents. Although both can contribute to crystallization, their effects are not as good as those of betaine hydrochloride. The reason why betaine hydrochloride achieves the highest aspect ratio of calcium sulfate dihydrate whiskers is attributed to the unique amphoteric characteristic of the quaternary ammonium-carboxylic acid inner salt structure of betaine. The stable and ordered synergistic adsorption layer formed by its zwitterionic structure on the radial crystal surface maximally suppresses lateral growth and promotes axial one-dimensional directional growth.

[0044] Table 4. Aspect Ratio Test Results of Calcium Sulfate Whiskers in Examples 7-9 Example 7 75：1 Example 8 65：1 Example 9 60：1 Comparative Example 1 A method for preparing calcium sulfate dihydrate whiskers from carbide slag includes the following steps: (1) Add 3.7g of carbide slag powder to water and stir to react. After the reaction, the mixture is subjected to solid-liquid separation by vacuum filtration to obtain the filtrate. (2) Take 36.5 mL (1.6 mol / L) of dilute sulfuric acid and titrate it into the filtrate. During titration, ensure that the reaction environment temperature is 90℃, the reaction time is 180 min, and the stirring speed is 100 r / min to obtain a slurry. (3) After heating and keeping the slurry at a constant temperature for 180 minutes, filter and dry it to obtain the product.

[0045] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not use any organic acid salts and only obtained particulate products with an aspect ratio of 5:1 under the same reaction conditions. This significant difference proves that organic acid salts play an indispensable core role in regulating the crystal growth direction.

[0046] The key difference between Comparative Example 1 and Example 1 lies in the presence or absence of organic acid salts. This comparison clearly reveals the indispensable regulatory role of organic acid salts in the formation of calcium sulfate dihydrate whiskers. Calcium sulfate dihydrate whiskers thermodynamically tend to grow faster along the axial direction and slower along the radial direction, exhibiting inherent anisotropy. However, in the solution without additives, this anisotropy is not significant. The difference in surface free energy among the various crystal facets is insufficient to induce extreme axial growth. Without additives, each crystal facet can grow freely after nucleation, and the newly formed crystals are prone to agglomeration, further leading to irregular morphology and dispersed size.

[0047] In summary, this invention reveals a process for preparing high aspect ratio calcium sulfate dihydrate whiskers using carbide slag through systematic experiments. The core innovation lies in using organic acid salts (betaine hydrochloride, glucosamine hydrochloride, and lysine hydrochloride) as crystallizing agents, reacting them with dilute sulfuric acid under specific conditions to synthesize whiskers. Experimental data show that the type of hydrochloride, reaction temperature, reaction time, and aging time are key factors affecting whisker quality, with the betaine hydrochloride system exhibiting the best performance. Regarding process parameters, a higher reaction temperature (90℃), a longer reaction time (180 min), and a sufficient aging time (180 min) all benefit the axial growth of the whiskers. Under these optimal conditions, Example 7, using betaine hydrochloride, reacted at 90℃ for 180 min and held for 180 min, achieving an aspect ratio as high as 75:1, the best among all examples.

[0048] This invention utilizes the principles of calcium ion cycling and acid-base neutralization to construct a relatively closed-loop green chemical process. First, calcium carbide slag (mainly calcium hydroxide) undergoes a neutralization reaction with betaine hydrochloride, generating a solution of betaine and calcium chloride, simultaneously achieving the conversion of calcium carbide slag and the separation of impurities. After filtration to remove insoluble residues, the calcium-rich filtrate reacts with sulfuric acid, where calcium ions combine with sulfate ions to form calcium sulfate dihydrate whiskers, while hydrochloric acid is regenerated. The newly generated hydrochloric acid immediately combines with free betaine in the solution, converting it back into betaine hydrochloride. Therefore, betaine hydrochloride achieves the transfer and release of calcium ions through acid-base reactions in the reaction system without being consumed itself. Finally, after filtration to obtain the whisker product, the betaine hydrochloride in the filtrate is regenerated and can be recycled to treat the next batch of calcium carbide slag. The entire process consumes only calcium carbide slag and sulfuric acid, converting industrial waste into high-value-added whiskers, with betaine hydrochloride used as a green medium for recycling, achieving resource recycling.

Claims

1. A method for preparing calcium sulfate dihydrate whiskers from carbide slag, characterized in that: Includes the following steps: S1. Dissolve the organic acid salt in water to prepare a solution; S2. Heat the organic acid salt solution, slowly add the carbide slag powder to the organic acid salt solution obtained in S1, stir and react, and after the reaction is completed, perform solid-liquid separation to obtain a filtrate rich in calcium ions; the organic acid salt is betaine hydrochloride; S3. Under constant temperature and stirring conditions, dilute sulfuric acid is added dropwise to the filtrate obtained in S2 to react and obtain a slurry containing calcium sulfate dihydrate whiskers. S4. The slurry obtained in S3 is kept at a warm temperature and aged, and then filtered, washed and dried to obtain calcium sulfate dihydrate whisker product. The aspect ratio of the calcium sulfate dihydrate whiskers is 75:

1.

2. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The concentration of organic acid salts in S1 is 153.6 g / L.

3. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The heating temperature in S2 is 70℃.

4. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The concentration of dilute sulfuric acid in S3 is 1.6 mol / L.

5. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The reaction temperature in S3 is 70-90℃.

6. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The reaction time in S3 is 60-180 min.

7. The method for preparing calcium sulfate dihydrate whiskers from carbide slag as described in claim 1, characterized in that: The heat preservation and aging time in S4 is 60-180 minutes.

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