CN112551521B - Environment-friendly diamond purification method based on high-temperature air - Google Patents
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Abstract
The invention provides an environment-friendly diamond purification method based on high-temperature air, which comprises the following steps: s1, weighing a proper amount of diamond synthesis blocks, crushing the diamond synthesis blocks, putting the crushed particles into a crucible, S2, putting the crucible containing the crushed particles of the diamond synthesis blocks into a muffle furnace, heating to 450-550 ℃ within 50-60 min, and preserving heat at 550 ℃ for 290-310 min; s3, taking out the crucible after heat preservation is finished, naturally cooling to room temperature, and transferring to a round bottom flask; s4, adding a proper amount of dilute hydrochloric acid into the round-bottom flask, heating to 120-150 ℃, and reacting for 40-60 min under the condition of heat preservation; s5, cooling to room temperature after the reaction is finished, and cleaning by using tap water; s6, drying the water in a baking oven at 100 ℃ after cleaning, and obtaining the diamond particles.
Description
Technical Field
The invention belongs to the technical field of synthetic diamond purification methods, and particularly relates to an environment-friendly diamond purification method based on high-temperature air.
Background
In the diamond system synthesized by the high-temperature high-pressure method with the participation of the metal catalyst, the yield of the diamond is between 20 percent and 30 percent, a large amount of graphite and the metal catalyst are also present in the obtained diamond synthesis block, the catalyst is mainly iron-nickel alloy, the metal catalyst is the catalyst of the reaction process, and the synthesis process is carried out at high temperature and high pressure, so the obtained diamond system has hard texture, and the unreacted graphite, the metal catalyst and the diamond are mixed together and are extremely difficult to separate the three parts to obtain the diamond, thereby bringing great inconvenience for the purification of the diamond.
At present, the diamond purification method is carried out by using mixed acid, namely, concentrated sulfuric acid and concentrated nitric acid are mixed according to a certain proportion, and the diamond in the diamond synthesis block is purified through oxidation-reduction reaction, but a large amount of reddish brown gas with pungent smell is generated in the purification process, the mixed gas is mainly a mixture of nitrogen oxide, sulfur dioxide, and mixed sulfur trioxide, and the like, so that the environment is greatly polluted, the tail gas treatment cost is increased to a great extent, meanwhile, the diamond obtained by the method also contains a small amount of impurities, and the application of the diamond in more fields is seriously limited due to the existence of the impurities, and the value of the purified synthetic diamond is influenced.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide an environment-friendly diamond purification method based on high-temperature air, aiming at the defects of the prior art, so as to solve the problems proposed in the background art.
In order to solve the technical problems, the invention adopts the technical scheme that: an environment-friendly diamond purification method based on high-temperature air comprises the following steps.
S1, weighing a proper amount of diamond synthesis blocks, crushing the diamond synthesis blocks, and putting crushed particles into a crucible, wherein the crushed particles of the diamond synthesis blocks contain 39.90-40.81% of metal catalyst alloy, 42.79-44.23% of graphite and 15.86-16.82% of diamond by mass fraction.
S2, placing the crucible containing the crushed particles of the diamond synthesis block into a muffle furnace, heating to 450-550 ℃ within 50-60 min, and preserving heat for 290-310 min at the temperature of 550 ℃.
S3, taking out the crucible after heat preservation, naturally cooling to room temperature, and pouring the crushed particles of the diamond synthesis blocks subjected to high-temperature treatment into a round bottom flask from the crucible.
S4, adding a proper amount of dilute hydrochloric acid into the round-bottom flask, heating to 120-150 ℃, and reacting for 40-60 min under the condition of heat preservation.
And S5, cooling to room temperature after the reaction is finished, and washing for 3-5 times by using tap water.
And S6, drying the water in an oven at 100 ℃ after the cleaning is finished, and obtaining the diamond particles.
Preferably, in S1, the particle size of the crushed synthetic diamond compact is 10 to 20 mm.
Preferably, the quantity of milliliters of the diluted hydrochloric acid added in the S4 is 1.7-1.9 times of the gram quantity of the diamond synthesis block weighed in the S1.
Preferably, the concentration of the dilute hydrochloric acid in S4 is controlled to be 28-32%.
Compared with the prior art, the invention has the following advantages.
When the synthetic diamond is purified, the synthetic diamond is calcined in the air at the temperature of 450-550 ℃, and the thermal expansion coefficient of graphite is 2 x 10 -6 The coefficient of thermal expansion of the alloy of/DEG C and the metal catalyst is 13 to 15 x 10 -6 The difference of/° C, make metal catalyst alloy, graphite and diamond in the synthetic diamond produce the gap each other, make the synthetic diamond lump become fluffy, can increase hydrochloric acid and contact surface area of metal oxide while post-treatment, remove graphite through the high-temperature oxidation method, metal catalyst alloy will produce metal oxide under the influence of oxygen in the air at the same time, can remove metal oxide among them with a certain amount of hydrochloric acid, thus get the purified product of the synthetic diamond lump, this method will not produce any gas polluting to the environment, and convenient and easy to operate, can also obviously improve the quality of the diamond sample that is purified and processed at the same time, will not obviously lose the diamond phase, have improved the use value of the synthetic diamond.
Drawings
FIG. 1 is a microscopic image of a diamond obtained by oxidation in an atmospheric atmosphere at a high temperature in the example of the present application.
FIG. 2 is a microscope photograph of diamond purified by a conventional process in the example of the present application.
FIG. 3 is an SEM image of diamond oxidized in an atmosphere at a high temperature in the examples of the present application.
Fig. 4 is an SEM image of diamond purified by the prior art in the example of the present application.
FIG. 5 shows the process A of the oxidation of the metal-catalyst alloy in the embodiment of the present application.
FIG. 6 shows the process B of the oxidation of the metal-catalyst alloy in the embodiment of the present application.
FIG. 7 is a C-process for oxidation of a metal-catalyst alloy in an embodiment of the present application.
FIG. 8 shows the process D of the oxidation of the metal-catalyst alloy in the embodiment of the present application.
FIG. 9 shows the process E of the oxidation of the metal-catalyst alloy in the embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In an embodiment, the present invention provides a technical solution: an environment-friendly diamond purification method based on high-temperature air comprises the following steps.
S1, weighing 208g of diamond synthesis block, crushing the diamond synthesis block, and putting the crushed particles into a crucible, wherein the particle size of the crushed particles of the diamond synthesis block is 10-20 mm, and the crushed particles of the diamond synthesis block contain 83-85g of metal catalyst alloy, 33-35g of graphite and 89-92g of diamond.
S2, placing the crucible with the crushed particles of the diamond synthesis block into a muffle furnace, heating to 550 ℃ within 50-60 min, and preserving heat at 550 ℃ for 300 min.
During the heating and heat preservation process, the thermal expansion coefficient of the graphite is 2 x 10 -6 The coefficient of thermal expansion of the alloy of/DEG C and the metal catalyst is 13 to 15 x 10 -6 The temperature is different, so that the metal catalyst alloy and the stone are madeThe ink and the diamond generate gaps between each other, so that the diamond synthesized block becomes fluffy, and the contact surface area of hydrochloric acid and metal oxide is increased when hydrochloric acid is used for treatment in the later period.
While oxidizing part of the graphite to carbon monoxide or carbon dioxide, C + O 2 →CO， C+O 2 →CO 2 ，CO+O 2 →CO 2 In CO/CO 2 Always involves a carbonyl group, the incoming oxygen atom, in particular oxygen from air, hits the oxygen atom in the carbonyl group to form an epoxy group, then the two epoxy groups near the carbonyl group move to the carbon atom near the carbonyl group, and the successive cleavage of the two carbon-carbon bonds releases CO/CO 2 (ii) a This process shows that not only can the high temperature O atoms form cavities in the graphite which originally had no cavities, but the process also results in the formation of functional groups which aid in the removal of carbon from the surface upon subsequent collision of the O atoms, and when cavities are formed in the graphite, the edges of the cavities form a pair of carbonyl groups, it has been demonstrated in the prior art that the migration of the epoxy groups brings the epoxide to a position near the carbonyl groups, and the epoxy compounds adjacent to the carbonyl groups are believed to reduce the barrier to dissociation of the carbonyl groups, thereby forming CO/CO 2 。
In this temperature raising process and the subsequent heat retaining process, the diamond is not oxidized for the following reasons.
(1) Experiments show that the oxidation temperature of graphite in air is 50 ℃ lower than that of diamond.
(2) Carbon atoms in diamond via three-dimensional strong covalent sp 3 The hybridized orbitals are bonded and form a regular tetrahedral structure, the valence electrons of the hybridized orbitals are highly localized in the covalent bond region, the acting force between carbon atoms is covalent bonds, the structural model of the diamond is that each carbon atom is tightly combined with 4 surrounding carbon atoms through strong interaction, the distance between the two tightly combined carbon atoms is about 0.155nm, so that a compact three-dimensional structure is formed, and the carbon atoms in the graphite are in sp (sp) connection 2 Hybrid orbital bonded graphites are layered structures in which every 1 carbon atom interacts strongly with the 3 surrounding carbon atoms in the sense of a sheetIn close contact, the distance between two "close contact" carbon atoms is about 0.142nm, and the distance between layers in graphite is 0.335nm, and the carbon atoms are easy to slide and crack in the direction parallel to the layer surface because of the relatively large distance and the weak interaction of the carbon atoms.
(3) Because the synthesized diamond contains 83-85g of metal catalyst alloy, particularly iron-nickel alloy, the existence of the elements of the VIII group reduces the initial temperature of the diamond gasification reaction and promotes the oxidation reaction of graphite, and the diamond is not oxidized, particularly as shown in a diamond microscopic picture obtained by oxidizing under the atmosphere at high temperature in fig. 1, a diamond microscopic picture obtained by purifying in the prior art in fig. 2, and a diamond SEM picture obtained by oxidizing under the atmosphere at high temperature in fig. 3 and a diamond SEM picture obtained by purifying in the prior art in fig. 4 can be confirmed.
While graphite is oxidized, because the obtained diamond synthesis block contains 83-85g of metal catalyst alloy, the metal catalyst alloy also interacts with oxygen in air to generate corresponding metal oxide, the oxidation of metal is usually a process of reducing free energy and can be carried out spontaneously, almost all metals can be oxidized, the oxidation of metal at room temperature is only slow, and the oxidation reaction becomes severe and destructive at high temperature, namely 550 ℃, the oxidation of metal is a very complex process, and the oxidation equation can be expressed as: m (metallic solid phase, iron-nickel alloy) + 1/2O 2 The whole oxidation process can be divided into the following stages.
(1) The gas-solid reaction stage is the initial stage of the reaction and is the process of the interaction between gas-phase oxygen molecules and the metal surface of the iron-nickel alloy. In this process, gas-phase oxygen molecules collide with the surface of the metal material, the oxygen molecules are physically adsorbed on the metal surface with van der waals force, and then the oxygen molecules are decomposed into atomic oxygen, and interact with free electrons of the base metal to form chemisorption, as shown in detail in the a process in fig. 5.
(2) The chemisorption of oxygen results in the nucleation and growth of oxide on the surface of the metal, while the oxygen continues to diffuse into the metal, as shown in the process B in fig. 6.
(3) The formation of continuous oxide film and the mass transfer of atoms lead to the continuous growth of surface oxides until the continuous oxide film is formed to cover the metal surface of the iron-nickel alloy, so that the oxidation reaction becomes a process of the interaction of metal-oxide-oxygen, as shown in the process C in fig. 7.
(4) In the oxidation reaction under the continuous oxidation film, the iron-nickel alloy metal and gas-phase oxygen are separated by the oxidation film formed on the metal surface, and in order to continue the reaction, the transmission of substances through the oxidation film layer is required, and the material characteristics and the tissue structure are different, so that the substance transmission modes in the oxidation film are different, the actual oxidation reaction positions and the formed oxide structures are different, for example, holes, grain boundaries, cracks and the like are formed in the oxidation layer, and in turn, the holes, the grain boundaries, the cracks and the like can provide more convenient channels for substance transmission. The reaction at high temperature may also cause the volatilization and melting of the surface oxide, the formation of cracks in the oxide, etc., which directly affect the expression form of the oxidation reaction, as shown in the D process in fig. 8 and the E process in fig. 9, and further generate the metal oxide through the above four stages.
S3, taking out the crucible after heat preservation, naturally cooling to room temperature, and pouring the crushed particles of the diamond synthesis blocks subjected to high-temperature treatment into a round bottom flask from the crucible.
S4, adding 400ml of 350-400ml of diluted hydrochloric acid with the concentration of 30% into the round-bottom flask, heating to 120-150 ℃, and carrying out heat preservation reaction for 40-60 min.
The reason for using 30% hydrochloric acid is that because the mixture of 98% concentrated sulfuric acid and 99% concentrated nitric acid used for the purification of synthetic diamond does not react with metal catalyst alloy oxide, because concentrated sulfuric acid and concentrated sulfuric acid have strong oxidizing property when the concentration is high, and the iron-nickel alloy at this time becomes metal oxide with high valence state, so that no oxidation reaction occurs between each other, however, the concentration of hydrochloric acid is lower compared with concentrated sulfuric acid and concentrated nitric acid, the hydrochloric acid aqueous solution ionizes under the action of water molecules to form free moving hydrogen ions and chloride ions, and the hydrogen ions react with metal oxide in the aqueous solution, which is as follows.
Fe 2 O 3 +6HCl=2FeCl 3 +3H 2 O。
NiO+2HCl=NiCl 2 +H 2 O。
In the reaction process, the solution is not green all the time, namely no ferrous ions are generated, and the oxide of the metal catalyst alloy can be removed by hydrochloric acid.
And S5, cooling to room temperature after the reaction is finished, washing for 3-5 times by using tap water, and washing iron salt, nickel salt and residual hydrochloric acid in the solution.
And S6, drying the water in an oven at 100 ℃ after the cleaning is finished, and obtaining the diamond particles.
No environmentally unfriendly product is generated in the treatment process, the graphite can be selectively removed, no loss and additional pollution are caused to the synthetic diamond, and compared with the existing mixed acid treatment by using concentrated sulfuric acid and concentrated nitric acid, the diamond phase is not obviously lost, as shown in fig. 1-4.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. An environment-friendly diamond purification method based on high-temperature air is characterized in that: the method comprises the following steps:
s1, weighing a proper amount of diamond synthesis blocks, crushing the diamond synthesis blocks, and putting crushed particles into a crucible, wherein the crushed particles of the diamond synthesis blocks contain 39.90-40.81% of metal catalyst alloy, 42.79-44.23% of graphite and 15.86-16.82% of diamond by mass fraction;
s1, the particle size of the crushed diamond synthetic block is 10-20 mm; the metal catalyst alloy is iron-nickel alloy;
s2, placing the crucible containing the crushed particles of the diamond synthesis block into a muffle furnace, heating to 450-550 ℃ within 50-60 min, and preserving heat for 290-310 min at the temperature of 550 ℃; in the heating and heat preservation processes, because the thermal expansion coefficient of the graphite is different from that of the metal catalyst alloy, gaps are generated among the metal catalyst alloy, the graphite and the diamond, and the diamond synthesis block becomes fluffy;
s3, taking out the crucible after heat preservation, naturally cooling to room temperature, and pouring the crushed particles of the diamond synthesis block subjected to high-temperature treatment into a round bottom flask from the crucible;
s4, adding a proper amount of dilute hydrochloric acid into the round-bottom flask, heating to 120-150 ℃, and reacting for 40-60 min under the condition of heat preservation; the concentration of the dilute hydrochloric acid is controlled to be 28-32%;
s5, cooling to room temperature after the reaction is finished, and washing for 3-5 times by using tap water;
and S6, drying the water in an oven at 100 ℃ after the cleaning is finished, and obtaining the diamond particles.
2. The method for purifying environment-friendly diamond based on high-temperature air as claimed in claim 1, wherein the amount of the diluted hydrochloric acid added in S4 is 1.7-1.9 times of the gram of the diamond synthetic block weighed in S1.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1115649A (en) * | 1964-06-05 | 1968-05-29 | Du Pont | Selective oxidation of graphite from mixture thereof with diamond |
| CN1404913A (en) * | 2002-11-07 | 2003-03-26 | 华北工学院 | Pollution-free gas-phase oxidation separation purification method for artificial diamond |
| CN105110327A (en) * | 2015-07-01 | 2015-12-02 | 中南钻石有限公司 | Superhard abrasive material surface high-cleaning treatment method |
| CN106276886A (en) * | 2015-05-22 | 2017-01-04 | 江苏益林金刚石工具有限公司 | A kind of method of purification of diamond |
| CN110980725A (en) * | 2019-11-04 | 2020-04-10 | 三门峡天钻晶体材料有限公司 | Method for removing metal impurities and residual graphite in diamond material |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102381702A (en) * | 2011-08-19 | 2012-03-21 | 长沙隆泰微波热工有限公司 | Method for purifying diamond concentrates through microwave oxidizing roasting |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1115649A (en) * | 1964-06-05 | 1968-05-29 | Du Pont | Selective oxidation of graphite from mixture thereof with diamond |
| CN1404913A (en) * | 2002-11-07 | 2003-03-26 | 华北工学院 | Pollution-free gas-phase oxidation separation purification method for artificial diamond |
| CN106276886A (en) * | 2015-05-22 | 2017-01-04 | 江苏益林金刚石工具有限公司 | A kind of method of purification of diamond |
| CN105110327A (en) * | 2015-07-01 | 2015-12-02 | 中南钻石有限公司 | Superhard abrasive material surface high-cleaning treatment method |
| CN110980725A (en) * | 2019-11-04 | 2020-04-10 | 三门峡天钻晶体材料有限公司 | Method for removing metal impurities and residual graphite in diamond material |
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