Electrophoresis sedimentation purification and separation method for submicron diamond

Abstract

The invention discloses an electrophoretic sedimentation purification and separation method for submicron diamonds, relates to the field of diamond grading and purification, and aims to solve the problems of high separation difficulty, low purity, low efficiency and easiness in agglomeration in the prior art. According to the technical scheme, the method comprises the following steps: firstly, carrying out vibratory screening on diamond powder, and then treating the surface of the powder by using a strong oxidizing solution; and preparing the treated diamond powder into slurry, filling the slurry into an insulating vessel with an electric field, and carrying out electrophoretic separation and classification. After treatment with the strong oxidizing solution, the problem of powder agglomeration can be effectively solved, the purity of the diamond powder can be effectively improved, the diamond powder can have excellent dispersing performance, and a high-precision separation effect can be achieved through electrophoretic separation and grading. Furthermore, the high-oxidability solution for treating the diamond powder and the purified water for preparing the slurry can be recycled, so that the material consumption is greatly reduced, the whole separation process is carried out at normal temperature or lower temperature, and the energy consumption is lower.

Description

Technical Field

[0001] The present invention relates to the technical field of diamond classification and purification, and specifically to an electrophoretic sedimentation purification and separation method for submicron-sized diamonds. Background Art

[0002] In the application process of diamond classification in the actual production stage, diamond micropowders mainly composed of submicron-sized diamonds (2 nm - 5 μm) are mainly used in aspects such as grinding debris, abrasive grinding pastes, and grinding fluids. In the actual production process of the above products, there are practical problems such as high mesh separation, low purification efficiency, and unsatisfactory dispersion and reuse that need to be urgently overcome. For example: in the process of preparing diamond powders with smaller particle sizes of high mesh numbers by the "air flow crushing method", about 20% of submicron-sized diamond micropowders are generated. When these micropowders are further refined and classified, there are often problems such as difficult separation, low purification, and poor dispersion. The nanodiamonds prepared by the "detonation method" also often exist in the form of agglomerates, causing problems for their further purification, dispersion, and utilization. The traditional method of separating layer by layer with an aqueous solution is time-consuming, has a high labor cost, and causes serious waste of water resources. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the existing defects and provide an electrophoretic sedimentation purification and separation method for submicron-sized diamonds, which can effectively solve the problems in the background art.

[0004] In order to achieve the above purpose, the present invention discloses an electrophoretic sedimentation purification and separation method for submicron-sized diamonds. The technical solution adopted is as follows: Step 1: Perform vibrating sieving on the diamonds to obtain loose submicron diamond powders; vibrating sieving can not only screen out large-particle diamonds but also disperse the diamond powders. Step 2: Use a strong oxidant to oxidize the loose submicron diamond powders obtained in Step 1 and then perform solid-liquid separation to obtain pure submicron diamond powders; the strongly oxidizing solution can remove amorphous carbon and metal impurities on the surface of the diamonds and introduce or generate a sufficient number of functional groups. Step 3: Add a solvent to the obtained pure submicron diamond powders in an insulating container to form a slurry, and apply an electric field outside the insulating container. Under the action of electrophoresis, separate, adsorb, and sediment the diamond powders to achieve the separation and classification of the diamond powders. Step 4: Collect the diamond powders at different positions.

[0005] As a preferred technical solution of the present invention, in Step 1, vibrating sieving is performed using a 500 - 1000 mesh sieve.

[0006] As a preferred technical solution of the present invention, in step 2, the oxidation treatment is carried out at a temperature of 40-80° C., and the strong oxidant used is one or more of concentrated nitric acid, concentrated sulfuric acid, hydrogen peroxide, and perchloric acid. When the oxidation treatment is carried out, the loose submicron diamond powder is mixed with the strong oxidizing solution and stirred sufficiently, and then reacted for 30 minutes. Stirring can make the diamond powder fully contact with the strong oxidizing solution.

[0007] As a preferred technical solution of the present invention, in step 3, at room temperature, the obtained pure submicron diamond powder is added to one of pure water, acidic solution and alkaline solution to prepare slurry, and the slurry is gradually added to the insulating container in batches. The acidic solution can be hydrochloric acid solution, nitric acid solution, etc., and the alkaline solution can be sodium carbonate solution, sodium hydroxide solution, etc.

[0008] As a preferred technical solution of the present invention, in step 3, during the electrophoresis process, the intensity of the electric field is gradient-controlled to achieve separation and classification of diamond powder, and the effect of fine separation can be achieved by controlling the pH value. In the pH range of 4 to 10, the more it deviates from neutrality (pH=7), the better the separation effect.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can efficiently and quickly separate and classify diamond powder by first vibrating and screening the diamond powder, then treating it with a strong oxidizing solution, and then performing electrophoretic separation and classification. Among them, the problem of powder agglomeration can be effectively solved after treatment with a strong oxidizing solution, and the purity of the diamond powder can be effectively improved after removing the amorphous carbon and metal impurities on the surface, and the diamond powder can have excellent dispersion properties, while the electrophoretic separation and classification can achieve a high-precision separation effect. Furthermore, the highly oxidizing solution used to treat the diamond powder and the pure water used to prepare the slurry can be recycled and reused, thereby greatly reducing material consumption. The entire separation process is carried out at room temperature or a relatively low temperature, and the energy consumption is relatively low. DETAILED DESCRIPTION

[0010] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0011] Combined with the actual physical properties of sub-micron diamond, the reasons for the problems described in the background art of sub-micron diamond are comprehensively analyzed as follows: (1) Sub-micron diamond has the characteristics of small size, light mass, high specific surface energy, and relatively high surface activity. This characteristic of small size, high specific surface energy, and high surface activity causes it to be easily adsorbed to each other under the action of van der Waals force, forming aggregates and carrying some tiny impurity particles; (2) Under the action of the high specific surface energy of sub-micron diamond, the sp3 diamond-type carbon structure on its surface can first be transformed into sp2 graphite-type carbon structure flakes under natural conditions. Subsequently, the sp2 graphite-type carbon structure flakes warp, and the underlying part continues to be transformed into sp2 structure. Eventually, these warped and newly transformed graphite structures are connected and wrapped with each other, and finally a graphite spherical shell is formed on the surface of sub-micron diamond.

[0012] Through the above analysis, the present invention discloses an electrophoretic sedimentation purification and separation method for sub-micron diamond. The technical solution adopted includes the following steps: Step 1, vibrating and sieving more than 500 g of sub-micron diamond within the range of 500 meshes. On the one hand, removing diamond particles with larger particles, and on the other hand, preliminarily dispersing the diamond powder to obtain a loose sub-micron diamond powder, laying a foundation for further dispersion in the follow-up; Step 2, under the condition of 80 °C, using concentrated nitric acid to oxidize the sub-micron diamond powder. The dosage is 50 ml of concentrated nitric acid per 2 g of diamond. Stir well and react for about 30 min to remove the amorphous carbon on its surface and introduce or generate enough functional groups (carboxyl, carbonyl, hydroxyl, etc.); The main purpose of this step is to achieve the effects of removing the amorphous carbon layer and metal impurities on the surface of the sub-micron diamond powder, thereby realizing the purification of the diamond powder; After the reaction, let it stand for precipitation, separate and recover the upper liquid for repeated use; Step 3, at room temperature, mixing the obtained sub-micron diamond powder with pure water in a ratio of 1:1 to form a slurry, and gradually adding it in three equal amounts of one-third of the total amount each time to an insulating container with an external electric field added. By adjusting the voltage, the current value is made to be in the range of 0.5 - 1 A, and in this embodiment, it is 0.75 A. By controlling the intensity of the electric field, under the action of electrophoresis, the diamond powder is separated, adsorbed, and sedimented. And finally, the separation and classification of the diamond powder are realized; Step 4, subsequently, collecting the diamond powder at different positions to achieve the purpose of fine division. Example 2

[0013] The difference between this embodiment and Example 1 is that in Step 1, a 1000-mesh sieve is used for vibrating sieving; Step 2, at 40 °C, use hydrogen peroxide to oxidize the submicron diamond powder, with a dosage of 50 ml of hydrogen peroxide per 2 g of diamond; Step 3, at room temperature, mix the obtained submicron diamond powder with 1.0 mol / L sodium hydroxide solution to form a slurry. During the preparation of the slurry, detect the pH value of the slurry and adjust it to 10. Gradually add the prepared slurry in four equal portions, each portion being one-fourth of the total amount, into an insulating vessel with an externally applied electric field. The current value of the electric field is 0.5 A. Example 3

[0014] The difference between this example and Example 1 is that in Step 1, a 750-mesh sieve is used for vibrating screening; Step 2, at 60 °C, use concentrated sulfuric acid to oxidize the submicron diamond powder, with a dosage of 50 ml of concentrated sulfuric acid per 2 g of diamond; Step 3, at room temperature, mix the obtained submicron diamond powder with 0.5 mol / L hydrochloric acid solution to form a slurry. During the preparation of the slurry, detect the pH value of the slurry and adjust it to 4. Gradually add the prepared slurry in five equal portions, each portion being one-fifth of the total amount, into an insulating vessel with an externally applied electric field; the current value of the electric field is 1 A.

[0015] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for electrophoretic sedimentation purification and separation of submicron diamonds, characterized in that: The following steps are involved: Step 1, vibrating and sieving diamond to obtain loose submicron diamond powder; Step 2, using a strong oxidant to oxidize the loose submicron diamond powder obtained in step 1, and then perform solid-liquid separation to obtain pure submicron diamond powder; Step 3, adding a solvent to the obtained pure submicron diamond powder in a container to prepare a slurry, and adding an electric field outside the insulating container to separate and classify the diamond powder under the action of electrophoresis; Step 4: Collect diamond powder at different positions.

2. The electrophoretic sedimentation purification and separation method of submicron diamond according to claim 1, characterized in that: In the step 1, a 500-1000 mesh sieve is used for vibration sieving.

3. The electrophoretic sedimentation purification and separation method of submicron diamond according to claim 1, characterized in that: In step 2, oxidation treatment is carried out at a temperature of 40-80° C., and the strong oxidant used is one or more of concentrated nitric acid, concentrated sulfuric acid, hydrogen peroxide, and perchloric acid. When the oxidation treatment is carried out, loose submicron diamond powder is mixed with the strong oxidizing solution and stirred sufficiently, and then reacted for 30 minutes.

4. The electrophoretic sedimentation purification and separation method of submicron diamond according to claim 1, characterized in that: In step 3, at room temperature, the obtained pure submicron diamond powder is added to one of pure water, acidic solution and alkaline solution to prepare slurry, and the slurry is added to an insulating container.

5. The electrophoretic sedimentation purification and separation method of submicron diamond according to claim 4, characterized in that: In step 3, during the electrophoresis process, the intensity of the electric field is adjusted to achieve separation and classification of diamond powder.