Purification process of artificial diamond micro-powder

Abstract

The invention relates to the technical field of diamond micro-powder, and discloses a purification process of artificial diamond micro-powder, which comprises the following steps: sequentially adding concentrated sulfuric acid, artificial diamond micro-powder and mixed acid into a reactor, and then heating for reaction; dropwise adding perchloric acid when the temperature is raised to 200 DEG C in the heating process; after the perchloric acid is dropwise added, continuously heating for reaction; leading out reaction materials after the reaction is finished; and diluting and washing the reaction material, filtering, and drying to obtain the purified artificial diamond micro-powder. According to the purification process disclosed by the invention, impurities on the diamond micro-powder can be effectively removed; the purification effect is further improved through the acid adding sequence and the acid adding type, and the whole treatment process is stable, environmentally friendly and high in economic benefit.

Description

Technical Field

[0001] The invention relates to the technical field of diamond micropowder, in particular to a purification process of artificial diamond micropowder. Background Art

[0002] Diamond is a mineral composed of carbon, with a chemical formula of C. It is an allotrope of carbon like graphite. Diamond is the hardest substance known in nature, with a hardness of 10. Due to its excellent physical and chemical properties, diamond is widely used in various fields. In industry, graphite is usually used to synthesize artificial diamonds under high temperature and high pressure conditions. Diamond powder can be obtained after purification of diamond crushed materials. As a superhard abrasive, diamond powder has been widely used in industrial production, such as diamond grinding wheels, diamond wires, diamond composite sheets, etc. The application value of diamond powder is closely related to its quality. Therefore, the market has a great demand for diamond powder with uniform particle size, suitable shape and high surface purity. Among them, the purity of diamond powder, that is, the surface impurity content, has a crucial influence.

[0003] The impurities in diamond micropowder include metal impurities and non-metallic impurities. Metallic impurities are Fe produced by mechanical crushing of raw diamond particles and exposed metal catalyst inclusions (Fe, Ni). Non-metallic impurities mainly come from the raw graphite and pyrophyllite residues of HPHT synthetic diamond and silicate dispersants used in the production process. At present, the surface purification of diamond micropowder mainly adopts chemical purification methods, using perchloric acid, concentrated sulfuric acid, concentrated nitric acid, hydrofluoric acid, concentrated hydrochloric acid and other reagents to react under high temperature conditions for impurity removal. Such methods have high energy consumption and large pollution. The reaction is sometimes unstable and produces harmful gases such as chlorine. In addition, the cost of perchloric acid is high, which will reduce corporate profits. Therefore, it is necessary to find a more stable, environmentally friendly and economically efficient purification method to solve the above technical problems. Summary of the invention

[0004] The present invention aims to provide a purification process for artificial diamond micropowder in view of the deficiencies in the prior art.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] A purification process for artificial diamond micropowder comprises the following steps:

[0007] S1, pickling

[0008] Concentrated sulfuric acid, artificial diamond powder and mixed acid are sequentially added into the reactor, followed by heating for reaction; when the temperature rises to 200°C during the heating process, perchloric acid is added dropwise; after the addition of perchloric acid is completed, heating is continued for reaction; after the reaction is completed, the reaction material is discharged;

[0009] S2, washing

[0010] The reaction materials are diluted, washed, filtered and dried to obtain purified artificial diamond micropowder.

[0011] Preferably, in step S1, after concentrated sulfuric acid, artificial diamond powder and mixed acid are added into the reactor in sequence, the temperature of the material in the reactor is raised to 110-130°C; after perchloric acid is added dropwise when the temperature rises to 200°C, the temperature of the material in the reactor is raised to 220-230°C.

[0012] Preferably, in step S1, the composition of the mixed acid is as follows: 98% sulfuric acid, 63% nitric acid, and water in a mass ratio of 25:20:30.

[0013] Preferably, the mixed acid is obtained by condensing acid mist or is prepared by mixing sulfuric acid, nitric acid and water in proportion.

[0014] Specifically, if the condensed acid obtained after condensation and recovery of the condensed acid mist is a mixture of different acids and its composition is consistent with the composition of the mixed acid, the condensed acid can be directly used as the mixed acid; if the condensed acid recovered is a single acid, the different condensed acids can be recovered and prepared into a mixed acid according to the composition of the mixed acid; if the concentration of the recovered condensed acid is not appropriate, new sulfuric acid or new nitric acid can be added to prepare a mixed acid; or new sulfuric acid, new nitric acid and water can be directly used to prepare a mixed acid in proportion. The "new sulfuric acid" and "new nitric acid" here refer to the finished sulfuric acid and finished nitric acid purchased.

[0015] Preferably, in step S1, the volume ratio of concentrated sulfuric acid, mixed acid and perchloric acid is (25-30):(10-20):(2-2.5); the concentrated sulfuric acid is 98% sulfuric acid (mass percentage).

[0016] Preferably, in step S1, the mass volume ratio of artificial diamond powder to concentrated sulfuric acid is (200000-300000):(25-30), and the comparison unit is carat:L.

[0017] Preferably, in step S1, the heating time during the pickling process is 6 hours; and the reaction temperature during the pickling process does not exceed 250°C.

[0018] More preferably, the maximum reaction temperature during the pickling process is 240-250°C.

[0019] Preferably, in step S1, stirring is performed during the pickling process; and during the dropwise addition of perchloric acid, heating and stirring are also continued to carry out the reaction.

[0020] Preferably, in step S1, the dropping speed of perchloric acid is 100 mL / min.

[0021] Preferably, in step S2, water is used to dilute and wash the reaction materials; and microwave drying is used in the drying process at a drying temperature of 110°C.

[0022] Specifically, step S2 comprises the following steps: the reaction material is diluted and washed with water for multiple times until the pH value of the washed liquid reaches 6 to 7; then, solid material is obtained by filtration, and the solid material is dried to obtain purified artificial diamond micropowder, wherein the water is purified water, deionized water, etc.

[0023] Preferably, in steps S1 and S2, the acidic liquid produced is neutralized using sodium hydroxide.

[0024] Preferably, in step S1, the particle size of the artificial diamond powder does not exceed 60 microns.

[0025] Working principle:

[0026] The main goal of pickling is to remove iron, carbon, and especially iron residues from artificial diamond powder.

[0027] Dilute sulfuric acid (the dividing line between concentrated sulfuric acid and dilute sulfuric acid: 70%) can react with iron at room temperature, and the reaction is more intense under heating conditions. However, since hydrogen will be produced when dilute sulfuric acid and iron react, the risk is too great. At the same time, concentrated sulfuric acid can also react well with iron under heating conditions, and the risk is relatively low. Therefore, concentrated sulfuric acid is used as the base acid in impurity removal production.

[0028] The purification process in the prior art uses nitric acid with a content of 65-68% (mass percentage) to replace the mixed acid of the present invention for reaction. The dilute nitric acid can react with iron at room temperature. In addition, the concentrated sulfuric acid contacts the water in the nitric acid to generate heat, which will intensify the reaction between the dilute nitric acid and iron. However, because nitric acid produces NO when removing iron, which is not easy to remove, the amount of nitric acid added should not be too much.

[0029] The process of the present invention adds a mixed acid, which contains dilute sulfuric acid (much less than 70%) and dilute nitric acid (much less than 68%). These dilute acids react simultaneously when in contact with the material, and the reaction is intensified under the heat release generated by the concentrated sulfuric acid in contact with water. That is to say, before the heating is officially started, adding the mixed acid will produce a more thorough and effective reaction than adding nitric acid, thereby making the overall treatment effect better.

[0030] As the heating starts and the reaction continues, the overall reaction in the liquid material changes to a reaction between concentrated sulfuric acid, concentrated nitric acid, iron and carbon. The addition of perchloric acid will further remove carbon. Because the reaction before the heating starts is good, the amount of perchloric acid added later can be appropriately reduced. Similarly, because the early reaction is relatively sufficient and the impurities in the material are reduced, the temperature rise after the later addition of perchloric acid is not that high, and the operating risk is reduced (when adding perchloric acid, the reaction is too intense and the material will splash out).

[0031] The reaction equation involved in the present invention is as follows:

[0032] Iron removal:

[0033] Fe+4H2SO4(dilute)=FeSO4+H2↑;

[0034] Fe+4HNO3(dilute)=Fe(NO3)3+NO↑+2H2O;

[0035] 2Fe+6H2SO(concentrated)=Fe2(SO4)3+3SO2↑+6H2O(heated);

[0036] Fe+6HNO3(concentrated)=Fe(NO3)3+3NO2↑+3H2O(heating).

[0037] Carbon removal:

[0038] C+2H2SO4(concentrated)=CO2↑+2SO2↑+2H2O(heating);

[0039] C+4HNO3(concentrated)=CO2↑+4NO2↑+2H2O(heated);

[0040] C+HClO4=CO2↑+HCl↑(heating).

[0041] Sulfuric acid, nitric acid and perchloric acid need to be concentrated and heated to remove carbon. Adding condensed acid makes the starting temperature of the material above 110°C, thereby extending the period of high temperature for the entire material and being more conducive to carbon removal.

[0042] In addition, the mixed acid of the present invention comes from the acid mist generated during the reaction and then recovered by condensation. The reuse of the condensed acid effectively reduces the processing pressure of the rear-end acid mist absorption tower, saves the alkali used for spray tower treatment and sewage treatment, and reduces the cost of acid use while also reducing the cost of processing acid mist and acid water.

[0043] Beneficial effects:

[0044] The purification process of the present invention can effectively remove impurities on diamond micropowder; the purification effect is further improved by the order and type of acid addition, and the entire treatment process is stable, environmentally friendly and highly economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The scanning electron microscope images of the diamond powder before and after purification of Example 1 of the present invention;

[0046] Figure 2 This is a Raman spectrum of the diamond powder before and after purification in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0048] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0049] There is no particular restriction on the purity of all raw materials in the present invention, and the present invention preferably adopts the conventional purity used in the art. The sourness used in the present invention is analytically pure.

[0050] The devices used in the present invention are not particularly limited and can be any of the commonly used devices in the art.

[0051] Embodiment 1:

[0052] A purification process for artificial diamond micropowder comprises the following steps:

[0053] S1, pickling

[0054] 25L of concentrated sulfuric acid, 300,000 carats of 30-60 micron artificial diamond powder and 20L of mixed acid are added into the reactor in sequence. At this time, the reaction is intense, and the liquid temperature rises to 110-130°C in a short time; then, heating and stirring are carried out for reaction. When the temperature reaches 200°C, 2L of perchloric acid is added dropwise (the dropping speed is 100mL / min), and the temperature rises to 220-230°C. Then, heating and reaction are continued. When the heating time reaches 6 hours (the temperature is 240-250°C at this time), the heating is turned off. When the material is cooled to below 80°C, the reaction material is discharged from the reactor, and then washed with pure water until the liquid pH value is 6-7, and clean diamond powder can be obtained.

[0055] The composition of the mixed acid is as follows: the mass ratio of 98% sulfuric acid, 63% nitric acid and water is 25:20:30; the concentrated sulfuric acid is 98% sulfuric acid; and the mixed acid is condensed acid obtained after acid mist is condensed and recovered.

[0056] S2, washing

[0057] The solid material is washed with deionized water and then dried with microwave at a drying temperature of 110° C. to obtain purified artificial diamond micropowder.

[0058] The ash content of the purified artificial diamond powder obtained in this example was tested to be 0.03%.

[0059] Embodiment 2:

[0060] A purification process for artificial diamond micropowder comprises the following steps:

[0061] S1, pickling

[0062] Add 30L of concentrated sulfuric acid, 200,000 carats of 1-5 micron artificial diamond powder, and 10L of mixed acid to the reactor in sequence. At this time, the reaction is strong, and the liquid temperature rises to 110-130°C in a short time; then heat and stir to react. When the material temperature rises to 200°C, add 2.5L of perchloric acid (the drop rate is 100mL / min), and the temperature will rise to 220-230°C. Then continue to heat the material until the total time is 6 hours (the temperature is 240-250°C at this time). Turn off the heating, and when the material cools to below 80°C, release the material from the reactor, and then wash it with pure water until the liquid pH value is 6-7, and you can get clean diamond powder.

[0063] The composition of the mixed acid is as follows: the mass ratio of 98% sulfuric acid, 63% nitric acid and water is 25:20:30; the concentrated sulfuric acid is 98% sulfuric acid; and the mixed acid is condensed acid obtained after condensation and recovery of condensed acid mist.

[0064] S2, washing

[0065] The solid material is washed with deionized water and then dried with microwave at a drying temperature of 100° C. to obtain purified artificial diamond micropowder.

[0066] The ash content of the purified artificial diamond powder obtained in this example was tested to be 0.04%.

[0067] Comparative Example 1

[0068] Add 30L of concentrated sulfuric acid, 220,000 carats of 30-60 micron artificial diamond powder, and 10L of nitric acid to the reactor in sequence. At this time, there is a reaction, and the liquid temperature rises to 70-80°C in a short time; then heat and stir to react. When the material temperature rises to 200°C, add 4L of perchloric acid, and the temperature will rise to 250-270°C. Then continue to heat the material until the total time is 6 hours. Turn off the heating, and when the material cools to below 80°C, release the material from the reactor, and then wash it with pure water until the liquid pH value is 6-7, and you can get clean diamond powder.

[0069] The concentrated sulfuric acid is 98% sulfuric acid; the concentration of nitric acid is 65%-68%; the solid material is washed with deionized water and then dried with microwaves at a drying temperature of 110° C. to obtain purified artificial diamond micropowder.

[0070] The ash content of the purified artificial diamond powder obtained in this comparative example was 0.04% after testing.

[0071] Comparative Example 2

[0072] Add 37.5L of concentrated sulfuric acid, 160,000 carats of 1-5 micron artificial diamond powder, and 12.5L of nitric acid to the reactor in sequence. At this time, there is a reaction, and the liquid temperature rises to 80-90°C in a short time; then heat and stir to react. When the material temperature rises to 200°C, add 4L of perchloric acid, and the temperature will rise to 250-270°C; then continue to heat the material until the total time is 6 hours and the end. Turn off the heating, and when the material cools to below 80°C, release the material from the reactor, and then wash it with pure water until the liquid pH value is 6-7, and you can get clean diamond powder.

[0073] The concentrated sulfuric acid is 98% sulfuric acid; the concentration of nitric acid is 65% to 68%; the solid material is washed with deionized water and then dried with microwaves at a drying temperature of 100° C. to obtain purified artificial diamond micropowder.

[0074] The ash content of the purified artificial diamond powder obtained in this comparative example was 0.06% after testing.

[0075] like Figure 1 The figure shows the scanning electron microscope images of the diamond powder before and after purification in Example 1 of the present invention. Figure 1 Figure (a) shows the diamond powder before purification. Figure 1 Figure (b) shows the diamond powder after purification.

[0076] Depend on Figure 1It can be seen that the raw material of diamond micropowder is a mixture, the particle distribution is relatively disordered, there is a certain agglomeration phenomenon, and there are irregular impurities adhering to the surface of the micropowder, mainly graphite and amorphous carbon. After purification, the graphite and amorphous carbon adhering to the surface of diamond micropowder have been oxidized and removed, and the particle shape is clearer.

[0077] like Figure 2 The figure shows the Raman spectra of the diamond powder before and after purification in Example 1 of the present invention. Figure 2 The broken line a is before the diamond powder is purified. Figure 2 The broken line b is after the diamond powder is purified.

[0078] Figure 2 The broken line a is 1324cm -1 A sharp diamond characteristic peak was observed at 1332 cm -1 The diamond powder used contains 1.89wt% impurities, which is not pure diamond powder. These impurities are mainly distributed on the surface of diamond powder, causing the vibration shift of Raman spectrum. -1 There is a weak graphite characteristic peak near the diamond powder, which indicates that there is a small amount of graphite impurities in the diamond powder raw material before purification. Figure 2 The half-width of the diamond characteristic peak in the spectrum of line b is obviously narrowed, and the crystallinity of the micropowder is greatly improved. -1 The characteristic peak of graphite has disappeared. It can be seen that through the method of the present invention, graphite impurities have been basically removed, and diamond micropowder with high purity is obtained.

[0079] In air, the melting point of diamond is 850-1000℃. According to the traditional detection method, the unpurified diamond powder is placed in a muffle furnace and burned at 1100℃. The remaining substance after burning is the ash, which is the impurities contained in the diamond powder. According to calculations, the impurity content of the raw material of diamond powder is 1.89%. After purification, the impurity content drops to 0.04%, which meets the industry standard of less than 1%.

[0080] The purified diamond powder was quantitatively tested by ICP-MS. The contents of impurity elements Fe, Ni, Al, Si, and Mn were 40.35×10 -6 , 8.47×10 -6 , 40.09×10 -6 , 10.22×10 -6 and 13.48×10 -6The test results show that after the purification process in this paper, the impurities of the diamond micropowder have been basically removed, and pure diamond micropowder has been obtained. The purity of the micropowder can meet the industrial production requirements.

[0081] In the embodiment and the comparative example, the cost of the 98% sulfuric acid used is 7 yuan / L, the cost of nitric acid with a concentration of 65% to 68% is 7 yuan / L, and the cost of perchloric acid is 280 yuan / L. It can be understood that the cost of the embodiment of the present invention is lower than that of the comparative example.

[0082] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A process for purifying artificial diamond micropowder, characterized in that: The following steps are involved: S1, pickling Concentrated sulfuric acid, artificial diamond powder and mixed acid are sequentially added into the reactor, followed by heating for reaction; when the temperature rises to 200°C during the heating process, perchloric acid is added dropwise; after the addition of perchloric acid is completed, heating is continued for reaction; after the reaction is completed, the reaction material is discharged; S2, washing The reaction materials are diluted, washed, filtered and dried to obtain purified artificial diamond micropowder.

2. The process for purifying artificial diamond micropowder according to claim 1, characterized in that: In step S1, the composition of the mixed acid is as follows: 98% sulfuric acid, 63% nitric acid, and water in a mass ratio of 25:20:

30.

3. The process for purifying artificial diamond powder according to claim 2, characterized in that: The mixed acid is obtained by condensing acid mist or prepared by mixing sulfuric acid, nitric acid and water in proportion.

4. The process for purifying artificial diamond powder according to claim 1, characterized in that: In step S1, the volume ratio of concentrated sulfuric acid, mixed acid and perchloric acid is (25-30):(10-20):(2-2.5); the concentrated sulfuric acid is 98% sulfuric acid.

5. The process for purifying artificial diamond powder according to claim 1, characterized in that: In step S1, the mass volume ratio of artificial diamond powder to concentrated sulfuric acid is (200000-300000):(25-30), and the comparison unit is carat:L.

6. The process for purifying artificial diamond powder according to claim 1, characterized in that: In the step S1, the heating time during the pickling process is 6 hours; and the reaction temperature during the pickling process does not exceed 250°C.

7. The process for purifying artificial diamond powder according to claim 1, characterized in that: In the step S1, the dropping speed of perchloric acid is 100 mL / min.

8. The process for purifying artificial diamond powder according to claim 1, characterized in that: In the step S2, water is used to dilute and wash the reaction materials; microwave drying is used in the drying process, and the drying temperature is 110°C.

9. The process for purifying artificial diamond powder according to claim 1, characterized in that: In the steps S1 and S2, the generated acidic liquid is neutralized using sodium hydroxide.

10. The process for purifying artificial diamond powder according to claim 1, characterized in that: In the step S1, the particle size of the artificial diamond powder does not exceed 60 microns.

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