CN111153409B - Method for purifying quartz sand by utilizing microwave heating and ultrasonic-assisted acid leaching for iron removal - Google Patents

Abstract

The invention relates to a method of using microwave heating to heat the impurity-containing phase in quartz at a temperature of 400-1000°C to promote the phase transformation and cracking of the iron (Fe)-containing impurity phase itself and the adjacent quartz matrix, and then use ultrasonic Auxiliary acid leaching method to remove iron. The method provided by the invention can achieve ultra-efficient removal of iron impurities in quartz sand, the iron content can be reduced to less than 0.383ppm at one time, the removal rate can reach more than 99.87%, and the iron removal efficiency is far higher than other iron removal methods.

Description

A method for purifying quartz sand by using microwave heating and ultrasonic assisted acid leaching to remove iron

technical field

The invention relates to the field of mineral purification, in particular to the technical field of quartz sand production, and relates to a method for purifying quartz sand by using microwave heating and ultrasonic-assisted acid leaching to remove iron.

Background technique

The main component of quartz sand is SiO ₂ , which is an important industrial raw material and is widely used in glass, ceramics, refractory materials and so on. With the development of science and technology, the demand for quartz glass is increasing in high-tech fields such as semiconductors, optical fiber communications, aerospace, solar energy, and electronics, and the demand for high-purity quartz raw materials is also increasing. Natural quartz stone contains some impurity elements, among which the presence of Fe directly affects the use value of quartz sand and reduces the quality of the product. For example, quartz sand is used to manufacture polycrystalline silicon ingot crucibles for solar cells. Since the quartz sand contains a certain amount of Fe, after the polycrystalline silicon ingot solidifies and grows, during the slow cooling process, Fe in the quartz crucible diffuses from When quartz sand enters the silicon ingot, a red zone that cannot be used to manufacture solar cells will be formed in the edge area where the polysilicon ingot contacts the quartz crucible, which will reduce the quality of the ingot. Therefore, the Fe content in quartz sand is required in many applications. as low as possible. Therefore, it is necessary to improve the efficiency of removing Fe as much as possible and reduce the content of Fe in quartz sand.

The methods for removing Fe from quartz sand are divided into physical methods, chemical methods and comprehensive methods.

Physical methods include magnetic separation, color separation, etc., but they can only remove magnetic or colored Fe-containing substances, and cannot reduce the Fe content in quartz sand to a very low level.

The chemical method is mainly acid leaching method, which is divided into single acid method and mixed acid method. It is found that the mixture of several acids can produce synergistic effect in the reaction process, and its effect is much better than the leaching effect of single acid. Veglio F. etc. mixed oxalic acid and sulfuric acid to leaching iron in quartz sand, the leaching rate (removal rate) was 35-45%, while using sulfuric acid alone, the leaching rate (removal rate) was only 3-9% under the same conditions %("Leahing test in iron removal from quartzusing oxalic and sulfuric acids", Veglio F, Passariello B., Barbaro M., Plescia P., Marabini A. M. Drum. Int. J. Miner. Process. 1998, 54, 183-200 ). Liu Chuang et al. treated quartz sand by combining alkali dissolution and sulfuric acid leaching to achieve the purpose of iron removal (see "Preparation of High-purity Quartz Sand by Alkali Dissolution of Quartz Gravel", Liu Chuang et al., Resource Investigation and Environment, 2006, 27 (7), 286-289). Since the Fe impurities in the quartz sand are only partially located on the surface of the quartz sand, and some of the Fe impurities are located inside the quartz sand particles and cannot contact with the acid solution, so the acid leaching method alone cannot reduce the Fe content in the quartz sand. down to a very low level.

A comprehensive purification method using multiple means can obtain a better purification effect than individual physical method purification or chemical method purification. The main process includes calcination, water quenching, crushing, magnetic separation, flotation, acid leaching, drying and other steps. Patent application CN110510620A, the quartz ore is calcined at 1050-1100°C for 2-4hrs; then quenched in water, and then pickled with a mixed acid of oxalic acid and thiocyanic acid: the content of Fe ₂ O ₃ in the purified quartz sand is 0.015% (150ppm). In many similar patent applications and industrial production practices, the calcination temperature of quartz ore is generally 900-1100°C, and the acid leaching is just soaking in a container at room temperature or heating for a long time. If the content of Fe in the raw ore Higher, through this process, the content of Fe cannot be quickly reduced to a very low level. Usually, a higher calcination treatment temperature is adopted, because the quartz material matrix will undergo phase transformation at high temperature, and microcracks will be generated after quenching treatment. The higher the treatment temperature, the more microcracks will be produced after quenching, which is beneficial to inclusions From this point of view, increasing the calcination temperature of quartz materials is beneficial to the removal of impurities. However, due to the relatively open crystal structure of quartz sand, especially because quartz has a phase transition of α-quartz-β-quartz and a phase transition of quartz-tridymite at 573°C and 870°C respectively, after it transforms into a high-temperature phase, the quartz The volume of the matrix expands, the crystal structure becomes looser, and interstitial impurity atoms such as Fe can diffuse at a faster rate in the loose crystal lattice of the quartz matrix. In quartz materials, Fe is often enriched in solid phase inclusions or fluid inclusions such as feldspar, magnetite, and liquid inclusions in the form of impurity phases. Under high temperature treatment, Fe can move from impurities to quartz. Diffusion occurs in the crystal lattice of the matrix and enters the quartz lattice. Once Fe enters the quartz matrix lattice, since the acid solution cannot enter the quartz lattice, it can no longer be removed by acid leaching. Therefore, high temperature is used for quartz materials. Calcination treatment will cause Fe to diffuse from the impurity phase to the quartz matrix and enter the quartz lattice, becoming lattice Fe and cannot be removed, and the removal rate of quartz sand impurity Fe is reduced, which limits the application of high-temperature calcination and the increase of calcination temperature. Moreover, relying on high-temperature calcination + water quenching to produce microcracks in the quartz substrate also has the problems of high energy consumption and cumbersome operations.

With the development of science and technology, the requirements for the purity of quartz sand are getting higher and higher, and how to quickly and efficiently remove Fe impurities in quartz sand is becoming more and more important, but the existing technology is difficult to meet the requirements of high-efficiency and rapid removal of Fe.

Contents of the invention

In order to solve the above problems, microwave heating and ultrasonic assisted acid leaching are used to achieve efficient iron removal.

The present invention is achieved through the following technical solutions:

A method for purifying quartz sand by microwave heating and ultrasonic-assisted acid leaching to remove iron, said method comprising the following steps:

(1) After heating the quartz ore to a predetermined temperature using microwaves and keeping it warm for a certain period of time, turn off the microwave power and cool it down to room temperature;

(2) mechanically crushing the quartz ore after the heat treatment in step (1) to form quartz sand;

(3) Mix the quartz sand sample obtained in step (2) with an acidic solution to form a pulp, put the pulp into an ultrasonic cleaning device and perform ultrasonic-assisted acid leaching at room temperature or under heating conditions, after the acid leaching is completed, turn off the ultrasonic, The pulp is naturally cooled to room temperature;

(4) After the quartz sand in step (3) is filtered and separated from the pulp, it is rinsed with deionized water until the pH is close to neutral, and then put into a clean container for drying to obtain a low-iron quartz sand product.

Wherein, the quartz ore in the step (1) is a natural ore with a particle size greater than 1 mm containing a large amount of SiO ₂ , the microwave heating temperature is 400-1000° C., and the holding time is 30-600 min. Preferably, the microwave heating temperature in step (1) is 400-870°C. Further preferably, the microwave heating temperature in step (1) is 400-573°C.

Preferably, the acidic solution in step (3) is one or a mixture of two or more of HNO ₃ , H ₂ SO ₄ , HCl, HF, H ₃ PO ₄ , CH ₃ COOH, C ₂ H ₂ O ₄ and The acid liquid formed by water, the concentration of the acid liquid can be adjusted according to the actual situation: the solid/liquid ratio of the pulp can be adjusted according to the situation.

The beneficial effects of the present invention are:

Microwaves have the characteristic of selective heating. The ability of the quartz sand matrix to absorb microwave energy is very weak and cannot be effectively heated by microwaves. However, the Fe-containing impurity phase inside the quartz sand can absorb microwave energy well and can be heated rapidly. Due to the heat conduction effect, the quartz matrix adjacent to the iron-containing impurities will also reach a relatively high temperature, while the matrix far away from the impurities will still maintain a relatively low temperature. When the temperature of the quartz matrix exceeds the phase transition temperature, it will A phase transition occurs, and the volume of the quartz matrix expands. When the subsequent quenching and rapid cooling occurs, the quartz matrix shrinks. In this cold and hot cycle, microcracks will be generated in the matrix around the impurity phase. Therefore, the use of microwave heating and cooling of quartz can promote the generation of microcracks near the impurity phase, and at the same time, it can better inhibit the diffusion of Fe from the impurity phase to the quartz matrix at high temperature, and then the microwave-heated quartz ore is made by mechanical crushing. The quartz sand is then acid leached by ultrasonic waves to promote the acid solution to enter the interior of the quartz sand along the micro-cracks with the assistance of ultrasonic waves, and react with Fe-containing impurities to dissolve and remove Fe. Realize the ultra-efficient removal of iron impurities in quartz sand. The iron content can be reduced to less than 0.383ppm after one removal, and the removal rate can reach more than 99.87%. The iron removal efficiency is far higher than other iron removal methods.

Description of drawings

Fig. 1 is the process flow diagram of the high-efficiency iron removal method for quartz sand of the present invention.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1-4, using microwave heating, heating the ore to 400, 600, 800, 1000°C, and keeping it warm for 1hr. After the sample is cooled, take the ore out of the microwave heating device, and use the mechanical crushing method to crush the quartz ore to 80- 120 mesh, and then, with 2 mol/L HNO ₃ , ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 284.876ppm of the quartz raw ore to: 0.383ppm, 2.063ppm, 6.823ppm, 8.410ppm, and the removal rates reach 99.87%, 99.28ppm, respectively. %, 97.61%, 97.05%. After the above steps, the content of Fe was greatly reduced, but with the increase of microwave heating temperature, the content of residual Fe gradually increased, and the removal rate of Fe decreased gradually.

Example 5-8, microwave heating is used to heat the ore to 400°C and keep it warm for 30, 45, 60, and 600 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80- 120 mesh, and then, with 2mol/L HNO ₃ , ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the quartz raw ore to: 0.534ppm, 0.895ppm, 0.958ppm, 1.845ppm, and the removal rates are: 99.836%, 99.725ppm %, 99.705%, 99.432%. After the above steps, the content of Fe was greatly reduced, but with the increase of microwave heating time, the content of residual Fe gradually increased, and the removal rate of Fe gradually decreased.

Examples 9-13, microwave heating is used to heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then, respectively Use 2, 1, 2, 1, 1 mol/L CH ₃ COOH, C ₂ H ₂ O ₄ , HCl, H ₃ PO ₄ , H ₂ SO ₄ for ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to: 10.016ppm, 1.838ppm, 6.370ppm, 8.880ppm, 5.921ppm. The removal rates are respectively: 96.9% , 99.43%, 98.04%, 97.27%, 98.18%. Based on Example 5, it can be seen that after the above steps, the content of Fe is greatly reduced, and different types of acids have a significant removal effect on Fe in quartz sand.

In Comparative Example 1, the quartz sand treatment process is similar to that of Examples 1-4, except that the microwave heating temperature is further reduced to 200°C. After the treatment, the residual Fe content in the quartz sand drops from 284.876ppm of the raw quartz ore to 24.630ppm , the removal rate was 91.36%, and the content of residual Fe was significantly higher than that of Examples 1-4.

In Comparative Example 2, the quartz ore was directly crushed without microwave heating, and then treated with acid leaching. The content of residual Fe in the obtained quartz sand dropped from 325ppm of the original quartz ore to 51.234ppm, and the removal rate was 84.236%. The content of Fe was significantly higher than in the case of Examples.

In comparative example 3, ordinary resistance heating was used to heat to 800° C., and the temperature was kept for 2 hrs. The quartz ore was crushed to 80-120 mesh by mechanical crushing method, and 2 mol/L HNO ₃ was used for acid leaching at 90°C for 2hrs. The content of Fe in the obtained sample dropped from 325ppm of the raw quartz ore to 81.126ppm, and the removal rate was 75.038 %, the content of residual Fe is significantly higher than that of the examples.

In comparative example 4, the microwave was used to heat to 400°C, the holding time was shortened to 15min, and the sample was cooled. The quartz ore was crushed to 80-120 mesh by mechanical crushing method, and 2 mol/L HNO ₃ was used for acid leaching at 90°C for 2 hours. The content of Fe in the obtained sample decreased from 325ppm of the raw quartz ore to 15.859ppm, and the removal rate was 95.120 %, the content of residual Fe is significantly higher than that of Examples 5-8.

Embodiment and comparative example are as follows:

Example 1

As shown in Figure 1, put the quartz ore into the microwave heating device first, turn on the microwave, heat the quartz ore to 400°C, keep it warm for 1 hour, turn off the microwave, and let the ore cool naturally. After cooling, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then ultrasonic acid leaching is performed at 90°C for 2hrs with 2 mol/L HNO ₃ . The content of Fe in the obtained samples decreased from 284.876ppm of quartz ore to 0.383ppm, and the removal rate reached 99.87%.

Example 2

Put the quartz ore into the microwave heating device, turn on the microwave, heat the quartz ore to 600°C, keep it warm for 1 hour, turn off the microwave, and let the ore cool naturally. After cooling, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then ultrasonic acid leaching is performed at 90°C for 2hrs with 2 mol/L HNO ₃ . The content of Fe in the obtained sample decreased from 284.876ppm of quartz ore to 2.063ppm, and the removal rate reached 99.28%.

Example 3

Put the quartz ore into the microwave heating device, turn on the microwave, heat the quartz ore to 800°C, keep it warm for 1 hour, turn off the microwave, and let the ore cool naturally. After cooling, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 2mol/L HNO ₃ , ultrasonic acid leaching at 90°C for 2hrs. The content of Fe in the obtained samples decreased from 284.876ppm of quartz ore to 6.823ppm, and the removal rate reached 97.61%.

Example 4

Put the quartz ore into the microwave heating device, turn on the microwave, heat the quartz ore to 1000°C, keep it warm for 1 hour, turn off the microwave, and let the ore cool naturally. After cooling, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 2mol/L HNO ₃ , ultrasonic acid leaching at 90°C for 2hrs. The content of Fe in the obtained samples decreased from 284.876ppm in quartz ore to 8.410ppm, and the removal rate reached 97.05%.

Example 5

Microwave heating is used to heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then, 2 mol/L HNO ₃ , Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 0.534ppm, and the removal rate is 99.836%.

Example 6

Microwave heating is used to heat the ore to 400°C and keep it warm for 45 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then, 2 mol/L HNO ₃ , Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 0.895ppm, and the removal rate is 99.725%.

Example 7

Microwave heating was used to heat the ore to 400°C and keep it warm for 60 minutes. After the sample was cooled, the ore was taken out from the microwave heating device, and the quartz ore was crushed to 80-120 mesh by mechanical crushing method, and then, 2 mol/L HNO ₃ , Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 0.958ppm, and the removal rate is 99.705%.

Example 8

Microwave heating is used to heat the ore to 400°C and keep it warm for 600 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then, 2 mol/L HNO ₃ , Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 1.845ppm, and the removal rate is 99.432%.

Example 9

Using microwave heating, heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 2 mol/L CH ₃ COOH ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 10.016ppm, and the removal rate of Fe is 96.9%.

Example 10

Using microwave heating, heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 1 mol/L C ₂ H ₂ O ₄ Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 1.838ppm, and the removal rate of Fe is 99.43%.

Example 11

Microwave heating is used to heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method. Then, use 2mol/L HCl in Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 6.370ppm, and the removal rate of Fe is 98.04%.

Example 12

Microwave heating is used to heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then, 1mol/L H ₃ PO ₄ ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 8.880ppm, and the removal rate of Fe is 97.27%.

Example 13

Using microwave heating, heat the ore to 400°C and keep it warm for 30 minutes. After the sample is cooled, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 1mol/L H ₂ SO ₄ Ultrasonic pickling at 90°C for 2hrs. After the acid leaching is completed, the quartz sand is washed and dried, and the Fe content of the obtained quartz sand drops from 325ppm of the raw quartz ore to 5.921ppm, and the removal rate of Fe is 98.18%.

Comparative example 1

Put the quartz ore into the microwave heating device, turn on the microwave, heat the quartz ore to 200°C, keep it warm for 1 hour, turn off the microwave, and let the ore cool naturally. After cooling, the ore is taken out from the microwave heating device, and the quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then ultrasonic acid leaching is performed at 90°C for 2hrs with 2 mol/L HNO ₃ . The content of Fe in the obtained samples decreased from 284.876ppm of quartz ore to 24.630ppm, and the removal rate was 91.36%.

Comparative example 2

The quartz ore is crushed to 80-120 mesh by mechanical crushing method, and then acid leached with 2 mol/L HNO ₃ at 90°C for 2hrs. The content of Fe in the obtained sample decreased from 325ppm of quartz ore to 51.234ppm, and the removal rate was 84.236%.

Comparative example 3

The quartz ore is heated to 800°C by resistance and kept for 2hrs. The quartz ore was crushed to 80-120 mesh by mechanical crushing method, and 2 mol/L HNO ₃ was used for acid leaching at 90°C for 2hrs. The content of Fe in the obtained sample dropped from 325ppm of the raw quartz ore to 81.126ppm, and the removal rate was 75.038 %

Comparative example 4

Put the quartz ore into the microwave heating device, turn on the microwave, heat the quartz ore to 400°C, keep it warm for 15 minutes, turn off the microwave, and let the ore cool naturally. After cooling, take the ore out of the microwave heating device, use mechanical crushing method to crush the quartz ore to 80-120 mesh, and then use 2mol/L HNO ₃ , ultrasonic acid leaching at 90°C for 2hrs. The content of Fe in the obtained sample decreased from 325ppm of quartz ore to 15.859ppm, and the removal rate was 95.120%.

To sum up, using microwaves to heat quartz ore at 400-1000°C, and then preparing the ore into quartz sand, and then using ultrasonic-assisted acid leaching, can obtain a super high removal rate of Fe, and the content of residual Fe can be reduced. to very low levels.

The above-mentioned embodiments are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (4)

1. A method for removing iron and purifying quartz sand by microwave heating and ultrasonic-assisted acid leaching is characterized by comprising the following steps:

(1) Heating quartz ore to a preset temperature by using microwaves, preserving heat for a certain time, and then closing the microwave power to cool the quartz ore to room temperature;

(2) Mechanically crushing the quartz ore subjected to the heating treatment in the step (1) to form quartz sand;

(3) Mixing the quartz sand sample obtained in the step (2) with an acidic solution to form ore pulp, putting the ore pulp into ultrasonic cleaning equipment, carrying out ultrasonic auxiliary acid leaching treatment at room temperature or under a heating condition, turning off the ultrasonic after the acid leaching treatment is finished, and naturally cooling the ore pulp to the room temperature;

(4) Filtering and separating the quartz sand in the step (3) from the ore pulp, washing the quartz sand with deionized water until the pH value is close to neutrality, and then putting the quartz sand into a clean container for drying to obtain a low-iron quartz sand product;

the microwave heating temperature in the step (1) is 400-600 ℃.

2. The method of claim 1, wherein: the quartz ore in the step (1) is a quartz ore with a particle size of more than 1mm and contains a large amount of SiO ₂ The heat preservation time of the natural ore of the components is 30-600min.

3. The method of claim 1, wherein: the microwave heating temperature in the step (1) is 400-573 ℃.

4. The method of claim 1, wherein: the acidic solution in the step (3) is HNO ₃ 、H ₂ SO ₄ 、HCl、HF、H ₃ PO ₄ 、CH ₃ COOH、C ₂ H ₂ O ₄ One or a mixture of two or more of them and water.

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