CN104562180A - Method for preparing calcium sulfate whisker from phosphogypsum - Google Patents

Abstract

The invention discloses a method for preparing calcium sulfate whiskers from phosphogypsum, which comprises the following steps: 1) crushing and grinding phosphogypsum raw materials to obtain phosphogypsum powder; 2) mixing the obtained phosphogypsum powder with dilute acid , placed in a reactor with a stirring device, controlled at a certain temperature to react, to obtain an acidic mixed solution containing calcium, sulfate ions and insoluble matter; 3) filtering the obtained mixed solution while it was hot, to obtain an acidic filtrate; 4) The obtained acidic filtrate is cooled to crystallize, filtered, washed and dried to obtain a calcium sulfate whisker product. The raw materials used in the present invention are not pretreated to remove impurities, and directly adopt one-step acid leaching to remove impurities to prepare calcium sulfate dihydrate whiskers with a large aspect ratio; the process flow is simple, the production cost is low, and the energy consumption is small. The water can be recycled; the obtained calcium sulfate whisker has the characteristics of high purity, large length and diameter, etc.; it is beneficial to popularization and application.

Description

A kind of method that prepares calcium sulfate whisker with phosphogypsum

technical field

The invention relates to a method for preparing calcium sulfate whiskers from phosphogypsum, and belongs to the technical fields of resource utilization of industrial solid waste, inorganic non-metallic materials and environmental protection.

Background technique

Phosphogypsum is a solid waste mainly composed of CaSO ₄ ·2H ₂ O discharged during the production of phosphoric acid, and contains phosphate, fluoride, other sulfates and organic matter. About 5 tons of phosphogypsum are produced for every ton of phosphoric acid produced, and the storage capacity of phosphogypsum in China is as high as more than 1 billion tons. The large stockpiling of phosphogypsum not only occupies land, but also causes different degrees of pollution to the environment. Therefore, the resource utilization of phosphogypsum has very important resource and environmental significance.

Calcium sulfate whiskers grow in the form of single crystals, with uniform cross-sectional area, complete shape, and perfect internal structure, and are needle-like and fibrous single crystals. Because of its excellent physical and chemical properties such as reinforcement, acid and alkali resistance, corrosion resistance, easy processing, non-toxic and harmless, it is widely used as a reinforcement in resin, plastic, rubber, paint, paper, asphalt, friction and sealing materials. Toughening agent or functional filler can also be directly used as filter material, thermal insulation material, etc. The average diameter of calcium sulfate whiskers is 1-8 μm, and the average length is 30-200 μm.

The Chinese invention patent whose publication number is CN101311355A discloses a preparation method of calcium sulfate whiskers. In the method, a strong alkali is used to adjust the pH value of the phosphogypsum slurry to be alkaline, and the stirring treatment is carried out at a temperature of 90-200° C. for 20-30 minutes, and the filter residue obtained by filtering is the first intermediate product; the first intermediate product is prepared into a certain concentration The slurry, in the presence of magnesium nitrate, is stirred at a temperature of 100-200°C for 20-30 minutes, and the filtrate obtained by filtering at a temperature of 80-150°C is the second intermediate product, and the second intermediate product is cooled and crystallized to obtain The product is calcium sulfate whiskers. The method has complex process, low production efficiency, and needs to add crystal form control agent. The publication number is CN102115142A Chinese invention patent, which discloses a preparation method of industrial calcium sulfate. The method uses phosphogypsum as a raw material, washes with water to remove soluble impurities, then uses hydrochloric acid to remove insoluble phosphate and other insoluble impurities, and finally filters and separates to obtain filter residues containing calcium sulfate and other sulfates, which are dried and pulverized to obtain industrial calcium sulfate. The calcium sulfate obtained by this method has low purity and is difficult to be widely used.

Contents of the invention

In order to solve the defects such as difficulty in removing impurities and complicated process routes for preparing calcium sulfate whiskers from phosphogypsum in the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing calcium sulfate whiskers with phosphogypsum with simple process and one-step removal of impurities. method.

In order to achieve the above object, the present invention adopts following technical scheme: a kind of method for preparing calcium sulfate whisker with phosphogypsum, comprises steps as follows:

1) Take phosphogypsum raw material and crush and grind to obtain phosphogypsum powder with a particle size of 20-600 mesh;

2) Put the phosphogypsum powder and dilute acid in step 1) in a reactor with a solid-to-liquid ratio of 10Kg/m ³ to 200Kg/m ³ , stir evenly, heat and dissolve, and then filter to obtain acidic filtrate and filter residue respectively;

3) aging the acidic filtrate obtained in step 2) to obtain an acidic suspension containing calcium sulfate whiskers; then filtering the acidic suspension to obtain calcium sulfate whisker filter residue and acidic waste liquid; wherein The calcium sulfate whisker filter residue is washed with industrial water until the pH value of the washing filtrate is neutral, and then dried at -15°C to 90°C to obtain the calcium sulfate whisker.

The mass percent concentration of dilute acid used in the above step 2) is 1.0%-25.0%, the heating and dissolving temperature is 60°C-120°C, and the dissolving time is 0.5h-8h.

The above-mentioned dilute acid can be selected from at least one of dilute hydrochloric acid, dilute nitric acid or recovered dilute acid.

The preparation steps for recovering the dilute acid above are: A) stirring the acid waste liquid after filtering the acid suspension and the washing filtrate with a neutral pH value after washing to form a mixed solution at a volume ratio of 1:1 to 4:1; B ) adding hydrochloric acid or/and nitric acid to the mixed solution in a volume ratio of 10:1 to 40:1 to prepare the above-mentioned recovered dilute acid; same.

The aging treatment in the above step 3) includes cooling and crystallization treatment; wherein, the cooling is to reduce the temperature of the acidic filtrate in step 2) to 10°C to 40°C; the crystallization treatment is to gradually reduce the temperature of the acidic filtrate Calcium sulfate whiskers are precipitated during crystallization, and the crystallization time is 2h-24h.

The calcium sulfate whisker prepared by the above method has a phase of calcium sulfate dihydrate, a diameter of 5-30 μm, a length of 100-2000 μm, and an aspect ratio of 10-400.

Owing to having adopted above-mentioned technical scheme, the beneficial effect of the present invention is as follows: 1) prepare calcium sulfate whisker with phosphogypsum one-step acid leaching impurity removal, whole synthetic process adopts one-step acid leaching to finish, simplified the technological process of prior art, reduced 2) Phosphogypsum does not need to be pretreated to remove impurities, and can be directly acid-leached to obtain calcium sulfate whiskers and separate from impurities at the same time. The dissolution rate of phosphogypsum is large, which is conducive to large-scale resource utilization of phosphogypsum; 3) The end of the first reaction Finally, the acid waste liquid and the washing filtrate can be recovered, and the reclaimed dilute acid prepared can replace dilute hydrochloric acid or dilute nitric acid for reuse, saving costs and improving the utilization rate of chemical additives; 4) the purity and whiteness of the synthetic calcium sulfate whiskers High density, large aspect ratio of whiskers, it is a fibrous whisker material visible to the naked eye.

Description of drawings

Fig. 1 is the XRD pattern of the calcium sulfate whisker that example 1 prepares.

Fig. 2 is the appearance photograph of the calcium sulfate whisker that example 1 prepares.

Fig. 3 is the photograph of the optical microscope of the calcium sulfate whisker that example 1 prepares.

Fig. 4 is the XRD figure of the calcium sulfate whisker that example 2 prepares.

Fig. 5 is the appearance photograph of the calcium sulfate whisker that example 2 prepares.

Fig. 6 is the photograph of the optical microscope of the calcium sulfate whisker that example 2 prepares.

Fig. 7 is the XRD figure of the calcium sulfate whisker that example 3 prepares.

Fig. 8 is the appearance photograph of the calcium sulfate whisker that example 3 prepares.

Fig. 9 is the photograph of the optical microscope of the calcium sulfate whisker that example 3 prepares.

Fig. 10 is the XRD figure of the calcium sulfate whisker prepared in example 4.

Fig. 11 is the appearance photograph of the calcium sulfate whisker that example 4 prepares.

12 is an optical microscope photo of calcium sulfate whiskers prepared in Example 4.

Fig. 13 is the XRD figure of the calcium sulfate whisker that example 5 prepares.

Fig. 14 is the appearance photograph of the calcium sulfate whisker that example 5 prepares.

15 is an optical microscope photo of calcium sulfate whiskers prepared in Example 5.

Fig. 16 is the XRD figure of the calcium sulfate whisker that example 6 prepares.

Fig. 17 is the appearance photograph of the calcium sulfate whisker that example 6 prepares.

18 is an optical microscope photo of calcium sulfate whiskers prepared in Example 6.

Fig. 19 is the XRD pattern of the calcium sulfate whisker prepared in Example 7.

Fig. 20 is the appearance photograph of the calcium sulfate whisker that example 7 prepares.

21 is an optical microscope photo of calcium sulfate whiskers prepared in Example 7.

Detailed ways

The present invention prepares the method for calcium sulfate whisker with phosphogypsum, comprises steps as follows:

1) Take the phosphogypsum raw material, crush it and grind it into a phosphogypsum powder with a particle size of 20-600 mesh;

2) Put the phosphogypsum powder and dilute acid in step 1) in a reactor with a solid-to-liquid ratio of 10Kg/m ³ to 200Kg/m ³ , stir evenly, heat and dissolve, and then filter to obtain acidic filtrate and filter residue respectively;

3) Aging the acidic filtrate in step 2) to obtain an acidic suspension containing calcium sulfate whiskers, and then filtering the acidic suspension to obtain calcium sulfate whisker filter residue and acidic waste liquid; wherein the sulfuric acid The calcium whisker filter residue is washed with industrial water until the pH value of the washing filtrate is neutral, and then dried at -15°C to 90°C to obtain the calcium sulfate whisker.

The dilute acid used in the above step 2) has a mass percentage concentration of 1.0%-25.0%, a heating and dissolving temperature of 60°C-100°C, and a dissolution time of 0.5h-10h.

The dilute acid used can be at least one of dilute hydrochloric acid, dilute nitric acid or recovered dilute acid.

The aging treatment in the above step 3) includes cooling and crystallization treatment; wherein, the cooling is to reduce the temperature of the acidic filtrate to 10°C to 40°C; the crystallization treatment is to gradually crystallize and separate out as the temperature of the acidic filtrate decreases Calcium sulfate whiskers, the crystallization time is 2h~24h;

Wherein, the acidic waste liquid and the washing filtrate can also be recovered, and then prepared to recover dilute acid, which is returned to step 2) for use. The preparation steps for recovering the dilute acid are: A) stirring the acidic waste liquid after filtering the acidic suspension and the washing filtrate with a neutral pH value after washing to form a mixed solution at a volume ratio of 1:1 to 4:1; B) ) add hydrochloric acid or/and nitric acid to the mixed solution in a volume ratio of 10:1 to 40:1, and mix to make the above-mentioned reclaimed dilute acid; The mass percent concentration is the same.

The phase of the calcium sulfate whisker prepared by the invention is calcium sulfate dihydrate, the diameter is 5-30 μm, the length is 100-2000 μm, and the aspect ratio is 10-400.

The technical scheme of the present invention will be further described in detail below through specific examples and in conjunction with the accompanying drawings.

Example 1:

The method for preparing calcium sulfate whiskers with phosphogypsum comprises steps as follows:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 100 mesh.

2) Mix the phosphogypsum powder obtained in step 1) with dilute hydrochloric acid with a mass percent concentration of 25.0% according to a solid-to-liquid ratio of 200Kg/m ³ , and place in a reactor with a stirring device to stir evenly; then, energize the Heat the material in the reactor to 100°C and stir for 2 hours to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; filter and separate the obtained acidic mixed solution while it is hot to obtain acidic filtrate and filter residue respectively. Discard the filter residue or use it for other purposes.

3) Aging the above-mentioned acidic filtrate, cooling it naturally to 20° C., and crystallizing it for 24 hours to obtain an acidic suspension containing calcium sulfate whiskers; then filtering the acidic suspension with a filter press to obtain Calcium sulfate whisker filter residue and acidic waste liquid; then the calcium sulfate whisker filter residue will be washed with industrial water repeatedly until the pH value of the washing filtrate reaches neutrality; the filter residue is dried in a ventilated place at normal temperature to obtain the Calcium sulfate whiskers.

The acid waste liquid and washing filtrate in this example can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate into a mixed solution at a volume ratio of 1:1 to 4:1, and then mix it with hydrochloric acid at a volume ratio of 10:1 to prepare a recovered dilute solution with a mass percentage concentration of 25.0%. acid, return to step 2) for use.

The XRD figure of the calcium sulfate whisker that obtains in this example, appearance photograph, the photograph of optical microscope are as shown in Figure 1, Figure 2, Figure 3. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; the appearance of calcium sulfate whiskers is a white whisker-like substance with a large aspect ratio and a diameter of 5 ～10μm, length 1000～2000μm, aspect ratio 100～400.

Example 2:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 20 mesh.

2) Mix the phosphogypsum powder obtained in step 1) with dilute hydrochloric acid with a mass percent concentration of 1.0% according to a solid-to-liquid ratio of 10Kg/m ³ , and place in a reactor with a stirring device to stir evenly; then the reactor The material in the mixture was heated to 60°C with steam, and stirred for 8 hours to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; the obtained acidic mixed solution was filtered and separated while it was hot to obtain acidic filtrate and filter residue respectively.

3) Aging the above-mentioned acidic filtrate, cooling the temperature to 20°C by air cooling, and crystallizing for 24 hours to obtain an acidic suspension containing calcium sulfate whiskers; and then using a filter press for the acidic suspension Filter to obtain the calcium sulfate whisker filter residue and acidic waste liquid; the obtained calcium sulfate whisker filter residue is washed with industrial water several times until the pH value of the washing filtrate reaches neutral; the filter residue is freeze-dried at -15°C, Calcium sulfate whiskers are obtained.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate into a mixed solution at a volume ratio of 1:1 to 4:1, and then mix it with hydrochloric acid at a volume ratio of 40:1 to prepare a recovered dilute solution with a mass percentage concentration of 1.0%. acid, return to step 2) for use.

The XRD figure of the calcium sulfate whisker that obtains in this example, appearance photograph, the photograph of optical microscope are as shown in Figure 4, Figure 5, Figure 6. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; the appearance of the calcium sulfate whiskers is a white whisker-like substance with a large aspect ratio, 5～ 15 μm, the length is 1000-2000 μm, and the aspect ratio is 100-400.

Example 3:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 600 mesh.

2) Mix the phosphogypsum powder obtained in step 1) with dilute hydrochloric acid with a mass percentage concentration of 7.2% according to a solid-to-liquid ratio of 70Kg/m ³ , and place in a reactor with a stirring device to stir evenly; then the reactor The material in the mixture was heated to 95°C by steam and stirred for 0.5h to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; the obtained acidic mixed solution was filtered and separated while it was hot to obtain acidic filtrate and filter residue respectively.

3) Aging the above-mentioned acidic filtrate, using water cooling to lower the temperature to 10° C., and crystallizing for 10 hours to obtain an acidic suspension containing calcium sulfate whiskers; then use a filter press to process the acidic suspension Filtration to obtain calcium sulfate whisker filter residue and acidic waste liquid; the obtained calcium sulfate whisker filter residue was washed with industrial water several times until the pH value of the washing filtrate reached neutrality; the filter residue was freeze-dried at -10°C to obtain The calcium sulfate whiskers.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate into a mixed solution at a volume ratio of 1:1 to 4:1, and then prepare a recovered dilute solution with a mass percentage concentration of 7.2% with hydrochloric acid at a volume ratio of 30:1. acid, return to step 2) for use.

The XRD pattern, appearance photo, and optical microscope photo of the calcium sulfate whiskers obtained in this example are shown in Figure 7, Figure 8, and Figure 9. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; the appearance of calcium sulfate whiskers is a white whisker-like substance with a small aspect ratio and a diameter of 15-30 μm, length 200-800 μm, aspect ratio 20-60.

Example 4:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 300 mesh.

2) Mix the phosphogypsum powder obtained in step 1) with dilute hydrochloric acid with a mass percent concentration of 25.0% according to a solid-to-liquid ratio of 100Kg/m ³ , and place in a reactor with a stirring device to stir evenly; then the reactor The materials in the mixture were heated to 80°C in a coal furnace and stirred for 4 hours to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; the obtained acidic mixed solution was filtered and separated while it was hot to obtain acidic filtrate and filter residue respectively.

3) Aging the above-mentioned acidic filtrate, using water cooling to lower the temperature to 40° C., and crystallizing for 2 hours to obtain an acidic suspension containing calcium sulfate whiskers; then use a filter press to process the acidic suspension. Filtrate to obtain calcium sulfate whisker filter residue and acidic waste liquid; rinse the obtained calcium sulfate whisker filter residue with industrial water several times until the pH value of the washing filtrate reaches neutral; dry the filter residue at 80°C to obtain the Calcium sulfate whiskers.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate into a mixed solution at a volume ratio of 1:1 to 4:1, and then mix it with hydrochloric acid at a volume ratio of 20:1 to make a concentration of 15.0% by mass percentage to recover dilute acid , return to use in step 2).

The XRD pattern, appearance photo, and optical microscope photo of the calcium sulfate whiskers obtained in this example are shown in Figure 10, Figure 11, and Figure 12. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; The diameter of the whiskers is 10-25 μm, the length is 100-600 μm, and the aspect ratio is 10-60.

Example 5:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 200 mesh.

2) The phosphogypsum powder obtained in step 1) is mixed with dilute nitric acid with a mass percentage concentration of 1.0% according to a solid-to-liquid ratio of 50Kg/m ³ , and placed in a reactor with a stirring device to stir evenly; then the reactor The material in the mixture was heated to 75°C with an oil burner and stirred for 6 hours to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; the obtained acidic mixed solution was filtered and separated while it was hot to obtain acidic filtrate and filter residue respectively.

3) Aging the above-mentioned acidic filtrate, cooling the temperature to 15°C by air cooling, and crystallizing for 8 hours to obtain an acidic suspension containing calcium sulfate whiskers; and then using a filter press for the acidic suspension Filtrate to obtain calcium sulfate whisker filter residue and acid waste liquid; wash the obtained calcium sulfate whisker filter residue with industrial water for several times until the pH value of the washing filtrate reaches neutral; dry the filter residue at 100°C to obtain the obtained calcium sulfate whiskers.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acid waste liquid and washing filtrate into a mixed solution with a volume ratio of 1:1 to 4:1, and then prepare a mixed solution with nitric acid at a volume ratio of 40:1 to recover dilute acid with a concentration of 1.0% by mass percentage. , return to use in step 2).

The XRD patterns, appearance photos and optical microscope photos of the calcium sulfate whiskers obtained in this example are shown in Figure 13, Figure 14, and Figure 15. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, and the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; 10-25 μm, length 500-1000 μm, aspect ratio 50-100.

Example 6:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 200 mesh.

2) The phosphogypsum powder obtained in step 1) is mixed with dilute nitric acid with a mass percentage concentration of 10.5% according to a solid-to-liquid ratio of 100Kg/m ³ , and placed in a reactor with a stirring device to stir evenly; then the reactor The material in the mixture was heated to 120°C by electric heating, and stirred for 0.5h to obtain an acidic mixed solution containing calcium, sulfate ions and acid insoluble matter; the obtained acidic mixed solution was filtered and separated while it was hot, and the acidic filtrate and filter residue were obtained respectively.

3) Aging the above-mentioned acidic filtrate, using water cooling to lower the temperature to 25° C., and crystallizing for 15 hours to obtain an acidic suspension containing calcium sulfate whiskers; then use a filter press to process the acidic suspension Filtrate to obtain the calcium sulfate whisker filter residue and acidic waste liquid; rinse the obtained calcium sulfate whisker filter residue with industrial water several times until the pH value of the washing filtrate reaches neutral; dry the filter residue at 60°C to obtain the Calcium sulfate whiskers.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate into a mixed solution at a volume ratio of 1:1 to 4:1, and then mix it with nitric acid at a volume ratio of 25:1 to make a mass percentage concentration of 10.5% to recover dilute acid , return to use in step 2).

The XRD patterns, appearance photos, and optical microscope photos of the calcium sulfate whiskers obtained in this example are shown in Figure 16, Figure 17, and Figure 18. The main crystal phase of the prepared calcium sulfate whiskers is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; the appearance of the calcium sulfate whiskers is a white whisker-like substance with a large long diameter and a diameter of 6 ～17μm, length 1050～2200μm, aspect ratio 108～400.

Example 7:

The steps of the method in this example are basically the same as those in Example 1, and will not be repeated here.

The difference is that in the following steps:

1) The phosphogypsum raw material is ground by a ball mill to obtain a phosphogypsum powder with a particle size of 80 mesh.

2) Mix the phosphogypsum powder obtained in step 1) with a mixed dilute acid with a mass percent concentration of 7.2% (dilute hydrochloric acid and dilute nitric acid are configured at a volume ratio of 1:1) according to a solid-to-liquid ratio of 70Kg/m ³ , and Place in a reactor with a stirring device and stir evenly; then heat the material in the reactor to 110°C with flue gas, and stir for 7 hours to obtain an acidic mixture containing calcium, sulfate ions and acid insolubles; the obtained acidic The mixture was separated by filtration while hot to obtain acidic filtrate and filter residue respectively.

3) Aging the above-mentioned acidic filtrate, using water cooling to lower the temperature to 30° C., and crystallizing for 8 hours to obtain an acidic suspension containing calcium sulfate whiskers; then use a filter press to process the acidic suspension Filtrate to obtain the calcium sulfate whisker filter residue and acidic waste liquid; rinse the obtained calcium sulfate whisker filter residue with industrial water several times until the pH value of the washing filtrate reaches neutral; dry the filter residue at 70°C to obtain the Calcium sulfate whiskers.

The above-mentioned acid waste liquid and washing filtrate can also be recycled. The specific method is: stir the above-mentioned acidic waste liquid and washing filtrate at a volume ratio of 1:1 to 4:1 to form a mixed solution, and then mix it with hydrochloric acid and nitric acid with a volume ratio of 1:1 to form a mixed solution at a volume ratio of 30:1. Prepare the dilute acid with a mass percentage concentration of 7.2%, and return to step 2) for use.

The XRD patterns, appearance photos, and optical microscope photos of the calcium sulfate whiskers obtained in this example are shown in Figure 19, Figure 20, and Figure 21. The main crystal phase of the prepared calcium sulfate whisker is dihydrate gypsum, the characteristic diffraction peak intensity is high, the peak shape is sharp, and the crystallinity is good; the appearance of the calcium sulfate whisker is white whisker-like substance, and the aspect ratio is second to that of the example 6. The diameter is 4-15 μm, the length is 1008-2060 μm, and the aspect ratio is 104-398.

Claims (6)

1., by a method for preparing calcium sulphate whiskers from ardealite, comprise step as follows:

1) phosphogypsum raw material crushing is got and grinding becomes granularity to be 20 ~ 600 object phosphogypsum powders;

2) by step 1) phosphogypsum powder and diluted acid be 10Kg/m by solid-to-liquid ratio ³~ 200Kg/m ³be placed in reactor to stir, reheat after dissolving and filter, obtain acid filtrate and filter residue respectively;

3) by step 2) acid filtrate carry out ripening, obtain the acid suspension liquid containing calcium sulfate crystal whiskers; This acid suspension liquid is filtered, obtains calcium sulfate crystal whiskers filter residue and acid waste liquid; Calcium sulfate crystal whiskers filter residue process water wherein rinses, and rinses pH value to wash filtrate for neutral, drier under-15 DEG C ~ 100 DEG C environment, obtains described calcium sulfate crystal whiskers.

2. method according to claim 1, is characterized in that: above-mentioned steps 2) diluted acid used, its mass percent concentration is 1.0% ~ 25.0%; The temperature of described heating for dissolving is 60 DEG C ~ 120 DEG C, and dissolution time is 0.5h ~ 8h.

3. method according to claim 2, is characterized in that: described diluted acid is dilute hydrochloric acid, dust technology or to reclaim in diluted acid at least a kind.

4. method according to claim 3, is characterized in that: the preparation steps of described recovery diluted acid is: A) described acid waste liquid and described wash filtrate are stirred into mixed solution with the volume ratio of 1:1 ~ 4:1; B) mixed solution is added hydrochloric acid or/and nitric acid is mixed with described recovery diluted acid for 10:1 ~ 40:1 by volume; The mass percent concentration of described recovery diluted acid is identical with the mass percent concentration of described dilute hydrochloric acid or described dust technology.

5. the method according to any one of claim 1-4, is characterized in that: step 3) described in ripening comprise cooling and Crystallizing treatment; Wherein, cooling is that the temperature of described acid filtrate is down to 10 DEG C ~ 40 DEG C; Crystallizing treatment separates out described calcium sulfate crystal whiskers with the reduction Step crystallization of described acid filtrate temperature, and its crystallization time is 2h ~ 24h.

6. method according to claim 5, is characterized in that: the thing of described calcium sulfate crystal whiskers is terra alba mutually, its diameter at 5 ~ 30 μm, length at 100 ~ 2000 μm, length-to-diameter ratio 10 ~ 400.