CN115970630A - Method for preparing nano hematite by using pyrite in coal-series solid waste - Google Patents
Method for preparing nano hematite by using pyrite in coal-series solid waste Download PDFInfo
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Abstract
The invention belongs to the field of coal solid waste resource utilization, and particularly relates to a method for preparing nano hematite by using pyrite in coal-based solid waste. The method comprises the following steps: 1) Grinding the coal-based solid waste powder to obtain coal-based solid waste powder; 2) And calcining the coal-based solid waste powder to obtain the nano hematite. The method provided by the invention is based on the advantage that most of pyrite is easy to oxidize, and the pyrite in the coal-series solid waste is heated and is introduced with air atmosphere, so that the nano hematite material with small particle size and large specific surface area is obtained. The method has the advantages of simple operation, low cost, environmental protection, safety, high efficiency and easy industrialization, and can convert the impurity pyrite in the coal-series solid waste into the nano hematite with good adsorption property, thereby being beneficial to the reclamation of the coal-series solid waste.
Description
Technical Field
The invention belongs to the field of coal solid waste resource utilization, and particularly relates to a method for preparing nano hematite by utilizing pyrite in coal-based solid waste.
Background
Nano hematite is a nano porous particulate material having a hematite crystal structure. Nanotechnology is considered one of the most important scientific techniques of the 21 st century, referring to the multidisciplinary intersection of science and techniques that study the properties and interactions of substances on the nanometer scale (1-100 nm) and exploit these properties. The hematite has the characteristics of wide existence, environmental friendliness and rich surface active sites, and is one of important media for biological-soil-mineral-water interaction. The hematite is stable in structure, non-toxic and easy to obtain, is a functional material with a great application prospect, is widely applied to various fields such As magnetic materials, lithium battery anode materials, gas sensors and the like, and particularly has high adsorption capacity on wastewater containing heavy metal ions such As As, cr, pb, cu, zn, cd, cs, se, sb, hg and the like in the aspect of sewage treatment. Heavy metal ions are adsorbed to the surface by the hematite, so that the concentration of the heavy metal ions in water is greatly reduced, and the environmental pollution is reduced. The nano hematite has huge specific surface area, more adsorption sites and stronger adsorption capacity, and is widely applied to the control and restoration of environmental pollution.
The preparation method of the nano hematite generally comprises a hydrothermal synthesis method, a precipitation method, a pyrolysis method, a sol-gel method and the like, but each synthesis method has some disadvantages. The biggest defect of the hydrothermal reaction is that the hydrothermal reaction is difficult to repeat and amplify into batch experiments and non-visibility, and whether various reaction parameters are adjusted or not can be determined only by checking reaction products; the precipitate in the precipitation method is colloidal, and is difficult to wash and filter, the precipitant is easy to be mixed into the precipitate as impurities or form a complex, and the suitable coprecipitator is difficult to find; pyrolysis methods require that the raw materials must be dissolved in a solvent; the raw materials used in the sol-gel method are expensive, and the whole sol-gel process requires a long time, often several days or weeks. In addition, most of these chemical syntheses require surfactants or organic additives, which are harmful to health and the environment. Therefore, thermal oxidation in various oxidizing atmospheres is the simplest, cheapest, and most straightforward method for preparing nano-iron oxide.
Coal gangue is a mixture of rocks discharged during coal mining and processing in all coal producing countries, and is generally considered as a solid waste and harmful to the environment. The data of the national development and reform committee show that the accumulated stockpiling quantity of the bulk solid wastes in China is about 600 million tons at present, wherein the accumulated stockpiling quantity of the coal gangue reaches 70 million tons, and the discharge quantity of the coal gangue is increased by 3 million tons every year. The coal gangue is also a natural resource, can be used as a raw material for high value-added products such as power generation, sintered brick making, ceramics, glass ceramics, molecular sieves and the like,but the heat treatment process involved in its comprehensive utilization releases a large amount of harmful gases (CO) 2 、SO 2 ) The environmental pollution, the occurrence of pyrite in the coal gangue and the thermal conversion behavior of the pyrite almost affect and determine the utilization mode, the treatment process, the environment and the economic performance of the coal gangue. Pyrite (FeS) 2 ) The coal gangue is formed in a reducing environment and is often present in a coal-series stratum or a coal bed, so that the coal gangue often contains more pyrite, and particularly the coal gangue in the secondary coal bed in south China, such as Sichuan, guizhou, yunnan, guangxi and the like, and the coal-series stratum and the coal bed contain more pyrite and pyrite nodules due to the fact that the influence of seawater on the coal formation process in the geological history period is greater. Some of the coal seams at the lower part of the Taiyuan of North China, e.g. 9 of the Taiyuan of Shanxi province # -15 # The coal is greatly influenced by seawater in the formation process of the coal seams, and the content of pyrite in the coal and coal gangue is also high. Pyrite in the coal gangue is oxidized in the long-term stacking process, the gangue pile is naturally generated, and a large amount of CO is released 2 And SO 2 Not only pollutes the environment, but also generates serious greenhouse effect. For a long time, the comprehensive utilization of the coal gangue is mainly limited to brick making, concrete raw material preparation, landfill, reclamation, underground filling and the like, and the comprehensive utilization technology level is lower and the economic benefit is poorer.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide a method for preparing nano hematite by using pyrite in coal-based solid waste, which improves the technical level of resource utilization of the coal-based solid waste, is a comprehensive utilization technology of coal solid waste with high added value, and has important social benefit, environmental benefit and economic value.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
1) Grinding: grinding the coal-based solid waste powder to obtain coal-based solid waste powder;
2) And (3) calcining: and calcining the coal-based solid waste powder to obtain the nano hematite.
In the invention, the source of the coal-based solid waste comprises coal gangue and/or pyrite nodule in coal.
Coal gangue is a mixture of rocks discharged during coal mining and processing in all coal producing countries, and is generally considered as a solid waste and harmful to the environment. The coal gangue often contains more pyrite, and the pyrite in the coal gangue is oxidized in the long-term stacking process and can promote the natural generation of gangue piles to release a large amount of CO 2 And SO 2 Not only pollutes the environment, but also generates serious greenhouse effect. For a long time, the comprehensive utilization of the coal gangue is mainly limited to brick making, concrete raw material preparation, landfill, reclamation, underground filling and the like, and the comprehensive utilization technology level is lower and the economic benefit is poorer. Especially, some coal-series solid wastes contain blocky pyrite nodules, and the content of pyrite is high. The invention can directly use the coal solid waste as a raw material, and can obtain the nano hematite only by grinding and calcining, and the obtained nano hematite is microspherical, has small particle size, large specific surface area and a nano-micron hierarchical pore structure, is an adsorbing material with good performance, thereby fully utilizing the coal solid waste. The method is a comprehensive utilization technology of the coal solid waste with high added value, and has important social benefit, environmental benefit and economic value.
Further, in the step 2), the calcination is: heating the coal-series solid waste powder to 500-1000 ℃ in heating equipment in air atmosphere, and then preserving heat for a period of time to obtain the nano hematite.
In the invention, the coal-based solid waste powder Bao Puzai is put in a container, so that when the container is isothermally heated to more than 500 ℃ in an air atmosphere, the coal-based solid waste powder can be fully contacted with oxygen, thereby changing the phase of pyrite in the coal-based solid waste powder into hematite; and preserving the heat for a period of time to further nanocrystallize the hematite so as to obtain the nano hematite.
Further, the heat preservation time is 30 min-120 min.
Within 1000 ℃, the higher the heating temperature is, the better the crystallinity of the nano hematite is; the longer the holding time, the better the crystallinity of the nano hematite.
Further, the isothermal heating rate is 5-20 ℃/min, preferably 10 ℃/min.
As a preferable scheme, enrichment is further included between the step 1) and the step 2), and the enrichment is as follows: and (3) enriching the pyrite in the coal-series solid waste powder by using a physical sedimentation method or a gravity separation method, and drying to obtain the coal-series solid waste powder containing the pyrite.
When the coal-based solid waste is a large amount of aluminosilicate solid waste, the content of pyrite in the coal-based solid waste is not very high. Aiming at the coal series solid waste, the method of the invention further comprises enrichment in the step 1) and the step 2). The method can enrich the pyrite in the coal-series solid waste.
Specifically, the physical sedimentation method comprises the following steps: taking coal-series solid waste powder, adding water and a dispersing agent, stirring to uniformly disperse, standing, removing supernatant, and keeping precipitate at the lower part.
In the invention, the gravity separation method is a mineral separation method commonly used in the field, and is a method for separating in a medium with certain density according to the difference of mineral specific gravity. As a preferred scheme, in the present invention, the reselection method is: adding the solid waste powder into heavy liquid with the density of 2.8-3.0, and separating the pyrite from other minerals by using the difference of the densities.
The drying comprises the following steps: and drying the remained lower precipitate at the temperature of 80-110 ℃ until the weight is not changed any more, thereby obtaining the coal-series solid waste powder containing the pyrite.
Furthermore, pyrite enriched from raw ores such as coal gangue is not a pure mineral, is a mixture of raw rocks after a large amount of clay minerals are removed, and contains a small amount of organic matters.
Further, the mass ratio of the coal-based solid waste powder to water is 1: (10-20), wherein the standing time is 1-25 min.
Further, a proper amount of dispersing agent is added in the stirring and dispersing process or ultrasonic treatment is adopted in the stirring and dispersing process.
In the invention, when the physical sedimentation method is used for enriching the pyrite in the coal-series solid waste, if the coal-series solid waste powder is not well dispersed, a proper amount of dispersing agent can be added in the stirring and dispersing process, namely, the coal-series solid waste powder is taken, water and the dispersing agent are added, the stirring is carried out to uniformly disperse the coal-series solid waste powder, and then the standing process and the like are carried out.
In the invention, the dispersant is sodium hexametaphosphate, and the addition amount of the dispersant sodium hexametaphosphate is preferably 0.5 to 1.5wt percent of the mass of the coal-series solid waste powder.
In the invention, when a dispersant of sodium hexametaphosphate is added in the stirring and dispersing process, the method also comprises the following steps before drying the precipitate: the lower precipitate was washed with water and centrifuged to remove water.
In the invention, when the coal-series solid waste powder is not well dispersed, ultrasonic treatment can be adopted in the stirring and dispersing process, so that the coal-series solid waste powder achieves a better dispersing effect.
Preferably, the time of the ultrasonic treatment is about 1 min.
The invention also provides the nano hematite, wherein the nano hematite is prepared by the method.
Preferably, the particle size of the nano hematite is between 20 and 100 nm.
More preferably, the nano hematite has a particle size of 50nm.
Furthermore, the specific surface area of the nano hematite is measured by a BET method to be 70-150 m 2 Between/g, preferably 77 to 90m 2 /g。
Compared with the prior art, the invention has the following advantages:
(1) The method provided by the invention improves the technical level of coal-based solid waste resource utilization, is a comprehensive utilization technology of coal solid waste with high added value, can promote the coal-based solid waste resource utilization, and has important social benefit, environmental benefit and economic value;
(2) The method provided by the application is simple and easy to implement, safe and environment-friendly, and the formed nano hematite is microspherical, small in particle size, large in specific surface area, has a nano-micron hierarchical pore structure, and is an adsorbing material with good performance.
Drawings
FIG. 1 is an SEM image of pyrite in the coal refuse of example 1;
FIG. 2 is a SEM image of pentahedral dodecahedral crystal artefact nanochemite prepared in example 1;
FIG. 3 shows the low temperature N of the nano-hematite produced in examples 1 and 2 after processing 2 Adsorption-desorption isotherms;
FIG. 4 is an SEM picture of a pyrite nodule in coal-based solid waste of example 2;
fig. 5 is a SEM image of nano-hematite prepared in example 2;
FIG. 6 is an SEM image of pyrite in the coal-based solid waste of example 3;
fig. 7 is an SEM image of octahedral crystal artefact nano-hematite prepared in example 3;
fig. 8 is a SEM image of nano-hematite prepared in example 4;
fig. 9 is a SEM image of nano-hematite prepared in example 5;
FIG. 10 XRD patterns of pyrite-containing powder samples at different temperatures;
FIG. 11 is a SEM image of hematite incubated for 20 min;
FIG. 12 is a SEM image of hematite incubated for 30 min.
Detailed Description
The following are specific embodiments of the present invention, which are intended to further illustrate the invention and not to limit it.
Specific surface area test and Low temperature N in the following examples 2 Adsorption was tested using ASAP 2020HD88 fully automated specific surface analyzer (Micromeritics, usa); the X-ray diffraction test is completed by adopting a Dmax-2500PC full-automatic powder X-ray diffractometer in Japan science; and observing the morphology of the mineral by using a Japanese Hitachi SU8020 field emission scanning electron microscope.
Example 1
A method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
(1) Grinding: taking a proper amount of gangue sample, crushing in a ball mill crusher, and sieving to 200 meshes to obtain the gangue powder.
(2) Enrichment: taking 30g of coal gangue powder, adding 500ml of water and 0.5wt% of dispersant sodium hexametaphosphate based on the mass of the coal gangue powder, stirring by a glass rod to uniformly disperse the coal gangue powder, standing and precipitating for about 20min, and separating the precipitate from the supernatant by a siphon or an injector; the lower precipitate was washed twice with water. And (3) centrifuging the washed mixture to remove water, and then putting the mixture into an oven at 80 ℃ for hot air drying for 12 hours until the weight is not changed any more, so as to obtain the coal gangue powder containing pyrite.
(3) And (3) calcining: putting the coal gangue powder containing the pyrite into a crucible, respectively heating the coal gangue powder to 1000 ℃ in a muffle furnace at a heating rate of 10 ℃/min, spreading the sample as thin as possible to fully contact with oxygen to ensure that the pyrite in the coal gangue powder is changed into hematite, and preserving the heat for 60min to obtain the nano hematite.
As shown in figures 1 and 2, SEM of the pyrite in the coal gangue and the prepared nano hematite is that the diameter of a nano hematite aggregate formed by oxidizing the pyrite is 0.5-4 mu m and the diameter of a single hematite nano microsphere is about 50nm as can be seen from scanning electron micrographs of samples. The hematite aggregate retains the pentahedral crystal artifacts of pyrite in coal gangue. The isothermal adsorption and desorption curve of nitrogen is shown in fig. 3, which shows the adsorption characteristic of gas on the solid surface, and the sample surface is at ultralow temperature for gas molecules (N) under a certain pressure 2 ) Has reversible physical adsorption effect. The deviation of the low-pressure end from the Y axis (nitrogen adsorption capacity) shows that the material has stronger acting force with nitrogen. The hysteresis loop effect is strong, which further proves that the adsorption capacity of the sample is strong. The BET test results are shown in table 1, and the specific surface area and pore volume of the prepared nano hematite sample are obviously increased and the pore size is slightly reduced compared with those of the raw ore.
Example 2
The method and the process for preparing the nano hematite from the pyrite in the coal-based solid waste are basically the same as those in the example 1, except that the sample adopts massive pyrite nodules in the coal-based solid waste, and the sample does not contain pyrite enrichment steps such as physical sedimentation, washing, centrifugation, drying and the like because of high content of the pyrite, and the nano hematite obtained by directly carrying out equal-temperature gradient heating after grinding is similar to that obtained by the process in the example 1. SEM of pyrite nodules in coal-based solid wastes and produced nano hematite are shown in figures 4 and 5, a nitrogen isothermal adsorption and desorption curve is shown in figure 3, results are shown in example 1, and BET test results are shown in Table 1.
Example 3
The method and process for preparing nano hematite from pyrite in coal-based solid waste are basically the same as in example 1, except that an ultrasonic instrument is adopted to treat for 1min in the dispersing process, then washing, physical settling and drying are carried out, the enriched pyrite-containing powder sample is directly heated, the obtained nano hematite is similar to the sample obtained in the process of example 1, and the hematite aggregate retains the octahedral crystal artifact of pyrite in the raw ore. SEM of pyrite and produced nano hematite in coal-based solid waste are shown in fig. 6 and 7, and BET test results are shown in table 1.
TABLE 1 BET test results
Example 4
A method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
(1) Grinding: taking a proper amount of coal gangue sample, crushing in a ball mill crusher, and sieving to 300 meshes to obtain coal gangue powder;
(2) Enrichment: taking 30g of coal gangue powder, adding 300ml of water, stirring by a glass rod to uniformly disperse the coal gangue powder, standing and precipitating for about 1min, separating the precipitate from the supernatant by a siphon tube, and keeping the precipitate for later use; drying the precipitate at 80 ℃ until the weight of the precipitate is not changed any more, so as to obtain coal gangue powder containing pyrite;
(3) And (3) calcining: in the air atmosphere, the coal gangue powder Bao Puzai crucible containing pyrite is heated to 500 ℃ at the heating rate of 5 ℃/min, and the temperature is preserved for 120min to obtain the nano hematite. The SEM of the prepared nano hematite is shown in figure 8.
Example 5
A method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
(1) Grinding: taking a proper amount of coal gangue sample, crushing in a ball mill crusher, and sieving to 300 meshes to obtain coal gangue powder;
(2) Enrichment: taking 30g of coal gangue powder, adding 600ml of water, stirring by a glass rod to uniformly disperse the coal gangue powder, standing and precipitating for about 25min, separating the precipitate from the supernatant by a siphon tube, and reserving the precipitate for later use; drying the precipitate at 110 ℃ until the weight is not changed any more, and obtaining coal gangue powder containing pyrite;
(4) And (3) calcining: in the air atmosphere, the coal gangue powder Bao Puzai crucible containing pyrite is heated to 900 ℃ at the heating rate of 20 ℃/min, and the temperature is preserved for 30min, so that the nano hematite is obtained. The SEM of the produced nano hematite is shown in fig. 9.
Example 6
A method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
(1) Grinding: taking a proper amount of coal gangue sample, crushing in a ball mill crusher, and sieving to 200 meshes to obtain coal gangue powder.
(2) Enrichment: taking 30g of coal gangue powder, adding 480ml of water and sodium hexametaphosphate as a dispersant accounting for 1.5wt% of the coal gangue powder, stirring by a glass rod to uniformly disperse the coal gangue powder, standing and precipitating for about 1min, and separating the precipitate from the supernatant by a siphon or an injector; the lower precipitate was washed twice with water. And (3) centrifuging the washed mixture to remove water, and then putting the mixture into an oven at 80 ℃ for hot air drying for 12 hours until the weight is not changed any more, thereby obtaining the coal gangue powder containing the pyrite.
(4) And (3) calcining: putting the coal gangue powder containing the pyrite into a crucible, respectively heating the coal gangue powder to 1000 ℃ in a muffle furnace at the heating rate of 12 ℃/min, spreading the sample as thin as possible to fully contact with oxygen, enabling the pyrite in the coal gangue powder to be transformed into hematite, and preserving the heat for 60min to obtain the nano hematite.
The SEM image of the produced nano hematite was similar to example 1.
Example 7
A method for preparing nano hematite by utilizing pyrite in coal-series solid waste comprises the following steps:
(1) Grinding: taking a proper amount of coal gangue sample, crushing in a ball mill crusher, and sieving to 200 meshes to obtain coal gangue powder.
(2) Enrichment: 30g of coal gangue powder is put into heavy liquid with the relative density of 2.89g/ml, evenly stirred and kept stand for a period of time, so that kaolinite, quartz and other clay minerals with light density float on the top, and particles rich in pyrite with high density sink on the bottom. The lower precipitate was washed twice with water. And (3) centrifuging the washed mixture to remove water, and then putting the mixture into an oven at 80 ℃ for hot air drying for 12 hours until the weight is not changed any more, so as to obtain the coal gangue powder containing pyrite.
(3) And (3) calcining: putting the coal gangue powder containing the pyrite into a crucible, respectively heating the coal gangue powder to 1000 ℃ in a muffle furnace at the heating rate of 12 ℃/min, spreading the sample as thin as possible to fully contact with oxygen, enabling the pyrite in the coal gangue powder to be transformed into hematite, and preserving the heat for 60min to obtain the nano hematite.
The SEM image of the produced nano hematite was similar to example 1.
Test example 1
The test example investigates the influence of the technological parameters of the calcination process on the crystallinity of the prepared nano hematite.
1. Influence of calcination temperature
The process was as in example 1, except that heating to 25 deg.C, 300 deg.C, 400 deg.C, 500 deg.C, 600 deg.C, 800 deg.C, 1000 deg.C and 1100 deg.C respectively at a heating rate of 10 deg.C/min in a muffle furnace and holding at the temperatures for 1h, respectively, and the effects of heating to different temperatures on the crystallinity of the resulting nano-hematite were examined.
XRD results at part temperature are shown in fig. 10: XRD patterns at different temperatures are shown in fig. 10, where the hematite peak becomes sharper and sharper with increasing temperature (hematite peak height gradually becomes larger and full width at half maximum gradually becomes smaller, as shown in table 2), indicating that crystallinity gradually becomes larger with increasing temperature.
TABLE 2 values of peak height and full width at half maximum in XRD test
| Temperature/. Degree.C | Peak height | Full width at half maximum |
| 500 | 214 | 0.316 |
| 600 | 917 | 0.295 |
| 800 | 1395 | 0.221 |
| 1000 | 3413 | 0.178 |
As can be seen from the above test results, when the heating temperature is below 500 ℃, no significant hematite peak appears in the XRD test; when the nano hematite is heated to 500 ℃, an obvious hematite peak appears in an XRD test, and the crystallinity of the nano hematite is better along with the increase of the heating temperature; when the temperature is further increased to above 1000 ℃, the XRD pattern is not obviously changed. Therefore, the heating temperature in the present invention is selected to be 500 to 1000 ℃.
2. Influence of incubation time
The process was as in example 1, except that heating was carried out in a muffle furnace at a heating rate of 10 ℃/min to 800 ℃ and the temperature was maintained for 20min and 30min, respectively, and the effect of the holding time on the crystallinity of the resulting nano-hematite was examined.
The results are shown in fig. 11 and 12:
from the test results, when the heat preservation time is less than 20min, no obvious nano micro-spherical hematite appears in the scanning electron microscope, and the SEM image of the heat preservation time for 20min is shown in FIG. 11; when the heat preservation time reaches 30min, obvious nano microspherical hematite appears in a scanning electron microscope (figure 12), and the crystallinity of the nano hematite is better along with the extension of the heat preservation time; when the heat preservation time reaches more than 120min, the crystallinity is not obviously changed any more. Therefore, in the present invention, the heating temperature is selected to be 30 to 120min.
Claims (10)
1. A method for preparing nano hematite by utilizing pyrite in coal-series solid waste is characterized by comprising the following steps:
1) Grinding: grinding the coal-based solid waste powder to obtain coal-based solid waste powder;
2) And (3) calcining: and calcining the coal-based solid waste powder to obtain the nano hematite.
2. The method according to claim 1, wherein in step 2), the calcination is: heating the coal-series solid waste powder to 500-1000 ℃ in heating equipment in air atmosphere, and then preserving heat for a period of time to obtain the nano hematite.
3. The method of claim 2, wherein the holding time is 30min to 120min.
4. A method according to claim 3, wherein the heating is at a rate of 5 to 20 ℃/min, preferably 10 ℃/min.
5. The method according to any one of claims 1 to 4, further comprising an enrichment between step 1) and step 2), wherein the enrichment is: enriching the pyrite in the coal-series solid waste powder by using a physical sedimentation method or a gravity separation method, and drying to obtain the coal-series solid waste powder containing the pyrite;
preferably, the physical sedimentation method is as follows: taking coal-series solid waste powder, adding water, stirring to uniformly disperse the coal-series solid waste powder, standing, removing supernatant, and keeping precipitate at the lower part;
the drying comprises the following steps: and drying the remained lower precipitate at the temperature of 80-110 ℃ until the weight is not changed any more, and obtaining the coal-series solid waste powder containing the pyrite.
6. The method of claim 5, wherein the mass ratio of the coal-based solid waste powder to the water is 1: (10-20), wherein the standing time is 1-25 min.
7. The method according to claim 5 or 6, characterized in that a proper amount of dispersant is also added during the stirring and dispersing process or ultrasonic treatment is adopted during the stirring and dispersing process.
8. A nano hematite, wherein the nano hematite is produced by the method of any one of claims 1 to 7.
9. The nano hematite as set forth in claim 8, wherein the nano hematite has a particle size of 20 to 100nm, preferably 50nm.
10. The nano hematite as set forth in claim 9, wherein the nano hematite has a specific surface area of 70 to 150m as measured by BET method 2 A ratio of 77 to 90 m/g 2 Between/g.
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| CN103657838A (en) * | 2013-12-09 | 2014-03-26 | 广州有色金属研究院 | Method for recovering pyrite from coal gangue |
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| Title |
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| 刘玉林等: "我国朔州地区煤矸石的矿物学特征及煅烧组分变化研究", 《 矿产保护与利用》, no. 3, 30 June 2020 (2020-06-30), pages 100 - 105 * |
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