CN115074815A - Method for preparing calcium sulfate dihydrate whisker at normal temperature by taking brine salt preparation by-product as raw material - Google Patents
Method for preparing calcium sulfate dihydrate whisker at normal temperature by taking brine salt preparation by-product as raw material Download PDFInfo
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Abstract
The invention provides a method for preparing calcium sulfate dihydrate crystal whiskers at normal temperature by taking by-products of brine salt preparation as raw materials. The method regulates and controls the growth rate of crystal nuclei and crystal whiskers by controlling the concentration of the solution, so that the calcium sulfate dihydrate crystal whiskers with uniform high length-diameter ratio are prepared, a dispersing agent, a surfactant and a crystal form control agent are not required to be added, the preparation can be carried out at normal temperature, the method is quick and efficient, the raw material cost is low, the green and environment-friendly effects are realized, and the method can be used for industrial production. The industrial byproduct salt mud and the high-nitrate water are used as raw materials, so that the whisker product with high added value can be obtained, a new method is provided for salt manufacturing enterprises to treat a large amount of accumulated salt mud and the high-nitrate water with high energy consumption and low added value, and the comprehensive utilization of resources is realized.
Description
Technical Field
The invention relates to the technical field of inorganic non-metallic material preparation and industrial solid waste recycling comprehensive utilization, in particular to a method for preparing calcium sulfate dihydrate whiskers at normal temperature by taking a sodium sulfate type brine salt preparation byproduct as a raw material.
Background
The salt mud is waste residue generated when raw salt is refined, the prior treatment technology of the chlor-alkali salt mud waste residue is basically limited to filter pressing and recovering brine, and the rest substances are stacked on the bank of rivers and lakes or are subjected to landfill treatment and the like. Along with the improvement of national energy-saving and emission-reduction requirements, the harmless treatment and utilization of the salt mud need to be solved urgently. The high-nitrate water is a byproduct in the primary brine production process, the solutes of the high-nitrate water are mainly sodium chloride and sodium sulfate, and the high-nitrate water can be used as a raw material for preparing mirabilite. Therefore, a new application way of the high-nitrate water needs to be found. Through detection, the salt mud of the company contains rich calcium carbonate, and the calcium source in the salt mud can react with high-nitrate water to produce calcium sulfate whiskers, so that the solid waste is effectively treated, and the additional value of industrial byproducts is increased.
Calcium Sulfate Whisker (CSW) is also called gypsum Whisker, is a fibrous single crystal, has uniform cross section, complete appearance and complete internal structure, and has excellent mechanical and physical properties such as high strength, high modulus, high toughness, loss resistance, high temperature resistance and the like. Meanwhile, the surface of the material is easy to treat, the compatibility is good, the material is non-toxic, and the material can be used for manufacturing a reinforced composite material with high strength, wear resistance and light weight, and is a novel high-performance inorganic material with wide application range. Calcium sulfate whiskers can be divided into dihydrate, semi-hydrate and anhydrous calcium sulfate whiskers according to the content of crystal water in crystals, and whiskers with different crystal water contents can be applied to different industrial fields, wherein the dihydrate calcium sulfate whiskers are widely applied to the paper-making industry.
At present, the preparation method of calcium sulfate dihydrate crystal whisker mainly comprises two methods, one is a reaction crystallization method, and the other is a recrystallization method.
The recrystallization method is to utilize the solubility difference of calcium sulfate at different temperatures and change the temperature to separate out the calcium sulfate in the solution. Patent CN111188087A discloses a method for preparing calcium sulfate whiskers by using phosphogypsum, which comprises the following steps: 1) crushing and grinding the phosphogypsum raw material to obtain phosphogypsum powder; 2) mixing the obtained phosphogypsum powder with dilute acid, placing the mixture in a reactor with a stirring device, and controlling a certain temperature to react to obtain an acidic mixed solution containing calcium, sulfate ions and insoluble substances; 3) filtering the obtained mixed solution while the mixed solution is hot to obtain an acidic filtrate; 4) and cooling, crystallizing, filtering, washing and drying the obtained acidic filtrate to obtain a calcium sulfate whisker product. The method needs heating and dissolving gypsum at 60-120 ℃ for 0.5-8 h, and consumes time and energy. CN 202110853640.7A process for continuously preparing calcium sulfate hemihydrate and calcium sulfate dihydrate whiskers by using salty mud is used for preparing the calcium sulfate hemihydrate whiskers through hydrothermal reaction, the calcium sulfate dihydrate whiskers are obtained through cooling crystallization, namely a recrystallization method, and the preparation method is complex, time-consuming and energy-consuming. CN 201310036635.2A method for preparing calcium sulfate whisker by recrystallization (1) temperature-raising dissolution process with program control: putting a raw material of which the main component is calcium sulfate into a sulfuric acid solution, stirring, heating at the same time, heating the mixture to 60-95 ℃ at a certain speed by adopting program control, and dissolving for 20 min-1 h; (2) and (3) controlling a temperature-reducing recrystallization process by a program: cooling the suspension obtained by dissolving to 10-30 ℃ at a certain speed by program control, and aging for 20 min-2 h; (3) separation and washing processes: carrying out solid-liquid separation on the suspension, and washing the separated solid-phase product; (4) and (3) drying: drying the washed solid phase product at a certain temperature to obtain calcium sulfate dihydrate crystal whiskers; the crystal whisker-shaped calcium sulfate dihydrate crystal whisker needs to grow through controlling the cooling rate of the crystallization reactor. The pretreatment of the existing recrystallization method for preparing the calcium sulfate whisker is long in time consumption, large in energy consumption and low in production efficiency.
Unlike recrystallization, the degree of saturation is not physically produced by reacting a solution containing calcium ions with a sulfateThe ionic solution is mixed and reacted under certain conditions to generate calcium sulfate precipitate, and crystals are separated out. Patent CN101586255B discloses a method for preparing calcium sulfate dihydrate whisker, which comprises adding dodecyl potassium phosphate and nonylphenol polyoxyethylene ether (TX10) into calcium chloride solution, adding dilute sulfuric acid while stirring, reacting and standing to obtain calcium sulfate dihydrate whisker. The method utilizes dilute sulfuric acid as a calcium ion precipitator, and because the addition amount of the dilute sulfuric acid is large and the acidity is strong, the conversion rate of calcium sulfate dihydrate crystal whiskers is low; dodecyl phosphate potassium salt and nonylphenol polyoxyethylene ether (TX10) are used as surfactants, have abundant foams, are easy to adsorb on the surface of the whisker during reaction, and prevent the further growth of the whisker. Patent CN110284197A discloses a clean and environment-friendly production method of gypsum whisker. Adding solution or solid of sodium sulfate into solution containing calcium chloride, or adding solution or solid of calcium chloride into solution of sodium sulfate containing chloride ions, and using Cl - Modelling of the ion in solution, forcing Ca 2+ With SO 4 2- The process of forming calcium sulfate by combination is oriented to grow, and the reaction is carried out for 3-30 h at 0-135 ℃ under normal pressure, thus producing the gypsum whisker. The method prepares the gypsum whisker by one-step reaction, but takes longer time, and the obtained whisker has larger diameter and smaller length-diameter ratio. The existing reaction crystallization method for preparing calcium sulfate dihydrate crystal whiskers has difficulty, so a dispersing agent, a crystal growth substance and the like are often required to be added, strong acid is used as a reaction raw material, and the cost is high. And even under the participation of other additives, the prepared dihydrate crystal whisker has smaller length-diameter ratio and poorer quality. In addition, the existing reaction crystallization methods all require hydrothermal reaction, heating and long reaction time.
Therefore, how to prepare the high-quality calcium sulfate dihydrate crystal whisker quickly and effectively at normal temperature by fully utilizing solid wastes and byproducts without adding a dispersing agent, a crystal growth substance and the like is a technical problem to be solved by the invention.
Disclosure of Invention
In order to solve the technical problems and overcome the defects in the prior art, the invention provides a method for preparing calcium sulfate dihydrate whiskers by taking a brine salt preparation byproduct as a raw material at normal temperature. The method adopts the solid waste salt mud in the chlor-alkali industry and the byproduct high-nitrate water as raw materials, firstly prepares the solution containing crystal nuclei by controlling the concentration and distribution of solutes in the solution, then promotes the generation of the crystal nuclei, and prepares the calcium sulfate dihydrate crystal whisker with high length-diameter ratio in a short time at normal temperature and within 20-40 min.
The invention relates to a method for preparing calcium sulfate dihydrate crystal whiskers at normal temperature by taking brine salt preparation byproducts as raw materials, which comprises the following steps:
(1) pretreatment of salt mud
Taking salt slurry generated in the sodium sulfate type brine purification process by a two-alkali method, wherein the salt slurry comprises the following components in parts by weight: CaCO 3 :70～75％，H 2 O:20～25％，CaSO 4 :2～4％，Mg(OH) 2 1-2%, NaCl 2-3%, and the balance SS. Adding hydrochloric acid into the salt slurry for dissolving, filtering when the pH value of the solution is 0.5-1.5, and collecting filtrate, namely the salt slurry acidolysis solution, wherein CaCl in the salt slurry acidolysis solution 2 The concentration is 220-330 g/L.
Further, the selected brine is sodium sulfate type brine, and the main components of the brine are as follows: 295-300 g/L of NaCl and SO 4 2- :13.8～14.8g/L，Ca 2+ :0.53～0.60g/L，Mg 2+ About 0.02g/L, the remainder being water.
(2) Preparation of crystal nucleus
The high-nitrate water is a byproduct in the brine production process, and comprises the following main components: na (Na) 2 SO 4 :74～89g/L，NaCl:220～250g/L，Ca 2+ +Mg 2+ Less than or equal to 1.0mg/L, the rest is water, and the pH value is 7-9.
And (3) mixing the hydrochloric acid hydrolysate obtained in the step (2) with high-nitrate water according to a volume ratio of 30-40: 1, and carrying out ultrasonic treatment for 20-30 min at a normal temperature of 40kHz and 60-80W to obtain a solution containing crystal nuclei.
The concentration of the mixed solution of the salt slurry acidolysis solution and the high-nitrate water in a specific ratio meets the requirement of the crystal nucleus growth environment, and a large amount of uniformly dispersed small calcium sulfate crystal nucleus particles are generated under the coordination of ultrasonic conditions, so that a key condition is provided for the preparation of subsequent whiskers.
(3) Whisker growth
In the crystal nucleusAdding 5-15 times of water in volume into the solution, and uniformly diluting the solution at normal temperature by ultrasonic waves (ultrasonic conditions 40kHz and 60w) for 0.5-1 min (the requirement of whisker growth can be met after dilution); according to the molar ratio SO 4 2- :Ca 2+ The molar ratio of SO is more preferably 1:1.5 to 2.5 4 2- :Ca 2+ Slowly adding high-nitrate water into the diluted crystal nucleus solution according to the proportion of 1:2, reacting for 20-40 min, performing suction filtration, and dehydrating and drying a filter cake (60-80 ℃ for 2-4 h) to obtain calcium sulfate dihydrate whiskers. Recovering the filtrate and returning the filtrate to the ore.
The method comprises the steps of adding high-nitrate water in two steps, firstly controlling the concentration of calcium sulfate in the solution, ensuring that high-concentration salt mud acidolysis solution and the high-nitrate water are mixed at the early stage, and generating a large amount of calcium sulfate crystal nuclei under the ultrasonic action; and adding water for dilution at the later stage, slowly adding the residual high-nitrate water, controlling the concentration of the solution, creating the condition for growing the crystal into the crystal whisker, and controlling the growth process by the concentration without adding other reagents to generate a template effect, so that the self-assembly behavior is formed, the powder is changed into the needle-shaped crystal whisker to grow, and the calcium sulfate dihydrate crystal whisker with uniform high length-diameter ratio is prepared.
The invention has the beneficial effects that:
the method can be used for simply carrying out acid treatment on the solid waste salt mud as a raw material of the reaction, the high-nitrate water is a primary brine byproduct, and the high-nitrate water and the primary brine byproduct are converted into industrial products by combining the reaction without additional treatment, so that the method has high economic value and environmental protection significance. In the reaction process, the shape and the uniformity of the crystal whisker can be controlled only by controlling the concentration of the solution, additives such as a crystal transfer agent, a crystal form promoter and the like are not required to be added, the content of impurities in the solution is reduced, and the subsequent washing treatment of the crystal whisker is convenient.
The method is carried out at normal temperature and normal pressure, can not be used in any heating process, is high-efficient and simple, has mild conditions, does not need heating, has low energy consumption and is suitable for industrial application compared with other methods which need long-time high-temperature hydrothermal reaction, aging and the like. The finally prepared calcium sulfate dihydrate crystal whisker has regular shape and uniform size and consumes short time. In addition, the high-concentration sodium chloride in the high-nitrate water can promote the precipitation of crystals and the axial growth of the whiskers, so that the quality of the whiskers is improved, and the preparation time of the whiskers is shortened.
Drawings
The invention is further illustrated below with reference to the figures, examples and comparative examples.
Figure 1 is a microscope image of calcium sulfate dihydrate whisker sample 1 prepared in example 1.
Figure 2 is a microscope image of calcium sulfate dihydrate whisker sample 2 prepared in example 2.
Figure 3 is a microscope image of comparative sample 1 of calcium sulfate dihydrate whisker made in comparative example 1.
Figure 4 is a microscope image of comparative sample 2 of calcium sulfate dihydrate whisker made in comparative example 2.
Figure 5 is a microscope image of comparative calcium sulfate dihydrate whisker sample 3 made in comparative example 3.
Figure 6 is a microscope image of comparative calcium sulfate dihydrate whisker sample 4 prepared in comparative example 5.
Figure 7 is a microscope image of comparative calcium sulfate dihydrate whisker sample 5 prepared in comparative example 6.
Fig. 8 is XRD patterns of sample 1 and sample 2.
Detailed Description
The present invention will be described in further detail with reference to examples. However, the scope of the present invention is not limited to the following examples. It will be understood by those skilled in the art that various changes and modifications may be made to the invention without departing from the spirit and scope of the invention.
Example 1
The brine used in the present example was tested to be: NaCl 297.7g/L, SO 4 2- :14.18g/L，Ca 2+ :0.54g/L，Mg 2+ 0.02g/L, and the balance of water. The salty mud comprises the following components in parts by weight: CaCO 3 :72.6％，H 2 O:20.6％，CaSO 4 :2.8％，Mg(OH) 2 1.8 percent, NaCl 2.1 percent and the balance of SS. The high-nitrate water mainly comprises the following components: na (Na) 2 SO 4 :79g/L，NaCl:230g/L，Ca 2+ +Mg 2+ Less than or equal to 1.0mg/L, the rest is water, and the pH value is 7.2.
(1) 200g of the salty mud is weighed, 21 wt% hydrochloric acid is added dropwise and stirred, the pH value of the solution is tested, and when the pH value is 1, the dropwise addition is stopped.
(2) Filtering the reaction system obtained in the step (1), and measuring CaCl in the reaction system 2 The concentration was 275 g/L.
(3) Mixing the hydrochloric acid hydrolysate obtained in the step (2) with high-nitrate water according to the volume ratio of 30:1, and carrying out ultrasonic treatment at normal temperature for 20min under the conditions of 40kHz and 60 w.
(4) And (4) adding water into the solution obtained in the step (3) to dilute the solution by 10 times, and carrying out normal-temperature ultrasonic treatment for 0.5min under the conditions of 40kHz and 60 w.
(5) In molar ratio of SO 4 2- :Ca 2+ And (4) slowly adding high-nitrate water into the solution diluted in the step (4) at the ratio of 1:2, and reacting for 30 min.
(6) After the reaction, the mixture is filtered, washed with water and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whisker, which is sample 1.
Example 2
(1) 200g of the salty mud prepared in the embodiment 1 is weighed, 35 wt% hydrochloric acid is added dropwise and stirred, the pH value of the solution is tested, and when the pH value is 0.5, the dropwise addition is stopped.
(2) Filtering the reaction system obtained in the step (1), and measuring CaCl in the reaction system 2 The concentration was 255 g/L.
(3) Mixing the acidolysis solution of the salt mud obtained in the step (2) with high-nitrate water according to the volume ratio of 30:1, and carrying out ultrasonic treatment at the normal temperature for 20min under the conditions of 40kHz and 60 w.
(4) And (4) adding water into the solution obtained in the step (3) to dilute the solution by 5 times, and carrying out ultrasonic treatment at normal temperature for 0.5min under the conditions of 40kHz and 60 w.
(5) In molar ratio of SO 4 2- :Ca 2+ And (4) slowly adding high-nitrate water into the solution diluted in the step (4) at the ratio of 1:1.5, and reacting for 20 min.
(6) After the reaction, the mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whisker, sample 2.
Comparative example 1
(1) Mixing the hydrochloric acid decomposition liquid obtained in the example 1 and high nitrate water according to the molar ratio SO 4 2- :Ca 2+ Mixed together in a ratio of 1:2 and reacted for 30 min.
(2) After the reaction, the reaction mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate as comparative sample 1.
Comparative example 2
(1) Mixing the hydrochloric acid hydrolysate obtained in the embodiment 1 with high-nitrate water according to the volume ratio of 30:1, and standing for 20 min.
(2) And (2) adding water to dilute the solution obtained in the step (1) by 10 times.
(3) In molar ratio of SO 4 2- :Ca 2+ And (3) slowly adding high-nitrate water into the solution diluted in the step (3) at the ratio of 1:2, and reacting for 20 min.
(4) After the reaction, the mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whiskers, which was comparative sample 2.
Comparative example 3
(1) The hydrochloric acid hydrolysate obtained in the example 1 and high-nitrate water are mixed according to the volume ratio of 30:1, and are stirred mechanically (200rpm) for 20 min.
(2) The solution of step (1) was diluted 10 times with water and stirred (200rpm) for 0.5 min.
(3) In terms of molar ratio SO 4 2- :Ca 2+ And (3) slowly adding high-nitrate water into the solution diluted in the step (3) at the ratio of 1:2, and reacting for 20 min.
(4) After the reaction, the reaction mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whisker as comparative sample 3.
Comparative example 4
(1) Mixing the hydrochloric acid hydrolysate obtained in the embodiment 1 with high-nitrate water according to a volume ratio of 30:1, and carrying out ultrasonic treatment at normal temperature for 20min under the conditions of 40kHz and 60 w.
(2) Diluting the solution obtained in the step (1) by 10 times with water, and performing ultrasonic treatment at normal temperature for 0.5min under the conditions of 40kHz and 60 w.
(3) In molar ratio of SO 4 2- :Ca 2+ And (4) slowly adding high-nitrate water into the solution diluted in the step (3) at the ratio of 1:4, and reacting for 20 min.
(4) No solid is formed after the reaction is finished.
Comparative example 5
(1) Mixing the hydrochloric acid hydrolysate obtained in the embodiment 1 with high-nitrate water according to a volume ratio of 30:1, and carrying out ultrasonic treatment at normal temperature for 20min under the conditions of 40kHz and 60 w.
(2) Diluting the solution obtained in the step (1) by 10 times with water, and performing ultrasonic treatment at normal temperature for 0.5min under the conditions of 40kHz and 60 w.
(3) In molar ratio of SO 4 2- :Ca 2+ And (3) slowly adding high-nitrate water into the solution diluted in the step (3) at the ratio of 1:1, and reacting for 20 min.
(4) After the reaction, the mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whiskers, which was comparative sample 4.
Comparative example 6
(1) Using analytically pure calcium chloride and sodium sulfate to prepare CaCl with the concentration of 275g/L 2 Solution and Na with concentration of 79g/L 2 SO 4 And (3) solution.
(2) CaCl obtained in the step (1) 2 Solution with Na 2 SO 4 The solution is mixed according to the volume ratio of 30:1, and is subjected to ultrasonic treatment for 20min at the normal temperature under the conditions of 40kHz and 60 w.
(3) And (3) adding water into the solution obtained in the step (2) to dilute the solution by 10 times, and carrying out normal-temperature ultrasonic treatment for 0.5min under the conditions of 40kHz and 60 w.
(4) In terms of molar ratio SO 4 2- :Ca 2+ Slowly adding Na into the solution diluted in the step (3) at a ratio of 1:2 2 SO 4 And (5) reacting for 30 min.
(5) After the reaction, the mixture was filtered, washed with water, and dried at 60 ℃ for 3 hours to obtain calcium sulfate dihydrate whiskers, which was comparative sample 5.
Detection experiment 1
Detecting the length-diameter ratio of the crystal whisker: the prepared whisker sample is placed in a dispersion medium (ethanol) by adopting a Nikon upright microscope, is subjected to ultrasonic dispersion at room temperature and then is dripped on a glass slide, and is placed in a 60 ℃ oven for drying and shaping; the whisker morphology was then observed, while the average length and average diameter of the whiskers were measured (50 sets of length data and 50 sets of diameter data for each sample, respectively), and the average aspect ratio of the whiskers was calculated. The results are shown in table 1, and fig. 1-7 are the micro-morphologies (400 ×) of calcium sulfate dihydrate whiskers of the examples and comparative examples.
TABLE 1
The average length, average diameter and length-diameter ratio data in the table 1 and the micro-morphology of the crystal whisker in the figures 1-7 are combined, so that the crystal whisker prepared by the two steps of crystal nucleus preparation and crystal whisker growth by using the salt slurry acidolysis solution and the high-nitrate water as raw materials in the samples 1 and 2 is long, thin and uniform and has a higher length-diameter ratio. The crystals prepared by direct mixing, short and fine, of comparative sample 1, on the other hand, illustrate the necessity and effectiveness of the two-step preparation method proposed by the present invention. The ultrasonic mixing mode of the comparative sample 2 and the ultrasonic mixing mode of the comparative sample 3 are respectively changed into standing and stirring, but the two modes both enable the ion diffusion speed to be slower and the ion concentration distribution to be uneven, so that more flaky crystals are generated. Comparative experiments 4 and 5 change the crystal whisker growth stage by adding SO4 2- With Ca 2+ The molar ratio, contrast experiment 4, because the high saltpeter water that adds is too little, leads to the calcium sulfate that generates too little, can't reach saturated concentration and precipitate out, contrast experiment 5, the high saltpeter water that adds is excessive, leads to the crystal (contrast sample 4) diameter that generates to become thick, and draw ratio reduces. In the comparative sample 5, the whiskers prepared from analytically pure calcium chloride and sodium sulfate as raw materials are thicker and contain more flaky crystals, which shows that the salt slurry and sodium chloride in high-nitrate water used in the invention have an effect of improving the whisker morphology.
Detection experiment 2
Whisker X-ray diffraction (XRD) detection:
adopting a step-by-step scanning method, X-ray (Cu), the scanning range is 5.000-35.000, the scanning mode is continuous scanning, the scanning speed is 2.0000deg/min, and the sample inclination is 0.0500 deg; the adjustment time was 1.50 sec.
Fig. 8 is an X-ray diffraction pattern of the sample, and it can be seen from XRD pattern analysis that sample 1 and sample 2 have distinct characteristic peaks of calcium sulfate dihydrate at 11.5 °, 20.7 °, 23.4 °, and 29.1 ° compared with XRD pattern of standard calcium sulfate dihydrate, which indicates that the product prepared by our process is calcium sulfate dihydrate whisker.
The invention uses the salt mud acidolysis solution and high-nitrate water as raw materials, and prepares the calcium sulfate dihydrate crystal whisker with uniform appearance and high length-diameter ratio by controlling the concentration of the solution and regulating and controlling the growth rate of crystal nucleus and crystal whisker. Additives such as a crystal transfer agent, a crystal form promoter and the like are not required to be added in the reaction process, so that the content of impurities in the solution is reduced, and the subsequent washing treatment of the crystal whisker is facilitated. The method is carried out at normal temperature and normal pressure, is simple, has mild conditions, does not need heating, has low energy consumption and is suitable for industrial application. In addition, the high-concentration sodium chloride in the high-nitrate water can promote the precipitation of crystals and the axial growth of the whiskers, improve the quality of the whiskers and reduce the preparation time of the whiskers.
The applicant has ascertained that while the above-described preferred embodiments of the present invention are taught, various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the present invention. Any modifications to the invention, equivalents of its operation, additions of auxiliary operations, selection of particular means, etc., are intended to fall within the scope and spirit of the invention.
Claims (6)
1. A method for preparing calcium sulfate dihydrate crystal whiskers at normal temperature by taking brine salt preparation byproducts as raw materials is characterized by comprising the following steps:
(1) pretreatment of salt mud
Dissolving salt mud generated in the purification process of sodium sulfate type brine in hydrochloric acid, filtering, and collecting filtrate to obtain salt mud acidolysis solution 2 The concentration is 220-330 g/L;
(2) preparation of crystal nucleus
Mixing the acidolysis solution of the salt slurry with high-nitrate water according to the volume ratio of 30-40: 1, and carrying out ultrasonic treatment at normal temperature for 20-30 min to obtain a solution containing crystal nuclei;
wherein the high-nitrate water is a byproduct in the brine production process and comprises the following components: na (Na) 2 SO 4 :74～89g/L，NaCl:220～250g/L，Ca 2+ +Mg 2+ Less than or equal to 1.0mg/L, the rest is water, and the pH value is 7-9;
(3) whisker growth
Adding 5-15 times of volume of water into the solution containing the crystal nucleus, and performing ultrasonic treatment at normal temperature for 0.5-1 min to dilute the solution uniformly; according to the molar ratio SO 4 2- :Ca 2+ Slowly adding high-nitrate water into the diluted crystal nucleus solution according to the proportion of 1: 1.5-2.5, performing suction filtration after room temperature reaction, dehydrating and drying a filter cake to obtain calcium sulfate dihydrate crystal whiskers, and recovering filtrate.
2. The method for preparing calcium sulfate dihydrate whiskers at normal temperature by using brine salt-making byproducts as raw materials according to claim 1, which is characterized by comprising the following steps: the sodium sulfate type brine obtained in the step (1) comprises the following components: 295-300 g/L of NaCl and SO 4 2- :13.8～14.8g/L，Ca 2+ :0.53～0.60g/L，Mg 2+ :0.02g/L, and the balance of water; the salt mud comprises the following components in parts by weight: CaCO 3 :70～75％，H 2 O:20～25％，CaSO 4 :2～4％，Mg(OH) 2 1-2%, NaCl 2-3%, and the balance SS.
3. The method for preparing calcium sulfate dihydrate whisker from brine salt-making by-products at normal temperature according to claim 1, which is characterized in that: the pH value of the salt slurry acidolysis solution in the step (1) is 0.5-1.5.
4. The method for preparing calcium sulfate dihydrate whisker from brine salt-making by-products at normal temperature according to claim 1, which is characterized in that: the ultrasonic condition is 40kHz and 60-80W.
5. The method for preparing calcium sulfate dihydrate whisker from brine salt-making by-products at normal temperature according to claim 1, which is characterized in that: and (3) drying the calcium sulfate dihydrate whisker at the temperature of 60-80 ℃ for 2-4 h.
6. The method for preparing calcium sulfate dihydrate whisker from brine salt-making by-products at normal temperature according to claim 1, which is characterized in that: and (4) in the step (3), the reaction time at room temperature is 20-40 min.
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|---|---|---|---|---|
| CN101717999A (en) * | 2009-11-26 | 2010-06-02 | 西南科技大学 | Method for preparing calcium sulfate whisker by crystal seed alcohol heating method |
| CN104894650A (en) * | 2015-05-31 | 2015-09-09 | 四川理工学院 | Method for preparing calcium sulfate dihydrate whisker from mirabilite and calcium water |
| CN111101191A (en) * | 2020-02-27 | 2020-05-05 | 武汉工程大学 | Method for preparing gypsum whisker by seed crystal method |
| WO2021000586A1 (en) * | 2019-07-04 | 2021-01-07 | 江苏一夫科技股份有限公司 | Method for preparing calcium sulfate dihydrate whiskers and calcium sulfate hemihydrate whiskers and product prepared therefrom |
| CN112850772A (en) * | 2021-01-29 | 2021-05-28 | 中蓝长化工程科技有限公司 | Method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore |
| CN113668060A (en) * | 2021-07-28 | 2021-11-19 | 中盐金坛盐化有限责任公司 | Process for continuously preparing semi-hydrated and dihydrate calcium sulfate whiskers by using salt slurry |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101717999A (en) * | 2009-11-26 | 2010-06-02 | 西南科技大学 | Method for preparing calcium sulfate whisker by crystal seed alcohol heating method |
| CN104894650A (en) * | 2015-05-31 | 2015-09-09 | 四川理工学院 | Method for preparing calcium sulfate dihydrate whisker from mirabilite and calcium water |
| WO2021000586A1 (en) * | 2019-07-04 | 2021-01-07 | 江苏一夫科技股份有限公司 | Method for preparing calcium sulfate dihydrate whiskers and calcium sulfate hemihydrate whiskers and product prepared therefrom |
| CN111101191A (en) * | 2020-02-27 | 2020-05-05 | 武汉工程大学 | Method for preparing gypsum whisker by seed crystal method |
| CN112850772A (en) * | 2021-01-29 | 2021-05-28 | 中蓝长化工程科技有限公司 | Method for preparing calcium sulfate by using calcium-containing waste liquor of fluorite ore |
| CN113668060A (en) * | 2021-07-28 | 2021-11-19 | 中盐金坛盐化有限责任公司 | Process for continuously preparing semi-hydrated and dihydrate calcium sulfate whiskers by using salt slurry |
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