A method for physically purifying artificial diamond

Abstract

A method for physically purifying artificial diamonds includes the following steps: 1) subjecting the synthesized graphite column to electrolysis, ball milling and shaking to obtain diamond material with a particle size of less than 1 mm; 2) placing the diamond material in step 1) in a mixture of water and a surfactant for ultrasonic cleaning, so that the diamond and graphite are separated in layers in a cleaning basin; the surfactant is ethanol or acetone; 3) collecting the upper graphite and lower diamond respectively, collecting the diamond and graphite mixture in the middle boundary layer and repeating the operation in step 2); 4) electrostatically separating the collected lower diamond. The present invention first uses ultrasonic treatment to separate the diamond and graphite, separates the mixture in the middle transition zone and performs secondary ultrasonic treatment; then the obtained diamond part is treated by an electric separator to further purify the diamond without discarding the magnetic diamond.

Description

Technical Field

[0001] The invention belongs to the technical field of post-processing of artificial synthetic diamonds, and in particular relates to a method for physically purifying artificial diamonds. Background Art

[0002] Artificial diamonds are generally produced by the HTHP method, which is to place a synthetic block wrapped with graphite columns in a press, and grow diamonds in the graphite columns under high temperature and high pressure. At this time, the graphite columns are a mixture of diamonds, graphite and a small amount of metal catalysts. In the post-processing process of purifying diamonds, it is necessary to separate the diamonds in the graphite columns to obtain pure diamonds.

[0003] There are two main methods for purifying diamonds. One is to purify diamonds by chemical methods using strong acids and alkalis, but this method is very harmful to the environment. The other is to separate diamonds from graphite by physical methods.

[0004] The Chinese patent with publication number CN 103303914A discloses a diamond purification process, which is to add a fluffing agent to the mixture of diamond and graphite, mix them evenly, treat them at high temperature, and separate diamond and graphite by a physical method of separation using a mineral separation shaker after cooling. The method of using a mineral separation shaker cannot completely separate diamond and graphite, and there will be a mixing zone in the intermediate transition zone of the shaking table separation. The diamond in the mixed material in the mixing zone does not enter the final separation result, resulting in a waste of diamond. Summary of the invention

[0005] The object of the present invention is to provide a method for physically purifying artificial diamond.

[0006] Based on the above purpose, the present invention adopts the following technical solutions:

[0007] A method for physically purifying artificial diamonds comprises the following steps:

[0008] 1) The synthesized graphite column is electrolyzed, ball-milled and shaken to obtain diamond material with a particle size of less than 1 mm; at this time, most of the graphite in the diamond material has been removed, and it will contain a small amount of pyrophyllite and dolomite;

[0009] 2) The diamond material in step 1) is placed in a mixture of water and a surfactant for ultrasonic cleaning, so that the diamond and graphite are separated in a cleaning basin; the surfactant is ethanol or acetone; this step utilizes the characteristics of ultrasonic vibration and the density difference between diamond and graphite to separate the diamond and graphite in the cleaning basin; diamond will settle to the lower part of the cleaning basin due to its high density and fast sedimentation speed, while graphite will remain on the upper part of the diamond layer due to its low density; as the ultrasonic vibration proceeds, the separation of diamond and graphite will become more and more thorough, and the separation boundary will become clearer and clearer; at the same time, the ultrasonic vibration can also crush the agglomerated particles of diamond and graphite, so that the agglomerates are peeled off, and then separated and precipitated;

[0010] 3) Collect the upper graphite layer and the lower diamond layer respectively, collect the diamond and graphite mixture in the middle boundary layer and repeat the operation in step 2);

[0011] 4) Electrostatic separation can be performed on the collected diamonds in the lower layer. The diamonds taken out from the lower layer are relatively clean, and at this time, the diamonds contain both magnetic diamonds and non-magnetic diamonds. These diamond materials are electrostatically separated by an electric separator, and the graphite inside can be further removed by utilizing the non-conductivity of diamonds and the conductivity of graphite.

[0012] The mixing ratio of the surfactant to water is 1:5-1:10.

[0013] The surfactant selected in the present invention does not react chemically with diamond after being mixed with water, and is safe, cheap and easy to obtain. When ethanol is selected as the surfactant as the ultrasonic solvent, it will generate heat if the ultrasonic wave is too long, which is unsafe; when acetone is selected as the solvent, it has strong dissolving ability, low viscosity, easy flow, low boiling point, and is easy to dry after cleaning.

[0014] Secondly, the wavelength of the surfactant solution used in the present invention is several millimeters or even several centimeters, and the ultrasonic effect can penetrate coarser particles to work. The reason why the mixing ratio of surfactant to water is selected in the range of 1:5-1:10 is that when the mixing ratio is greater than 1:10, the surfactant is more volatile and is easily volatilized by ultrasound. If the mixing ratio is less than 1:5, the effect of ultrasonic purification cannot be achieved.

[0015] Compared with the prior art, the present invention has the following beneficial effects: not only can the diamond be thoroughly purified, but also the magnetic diamond can be retained without causing waste. The method first uses ultrasonic treatment to separate the diamond from the graphite, separates the mixed material in the intermediate transition zone and performs secondary ultrasonic treatment; then the obtained diamond part is treated by an electric separator to further purify the diamond without discarding the magnetic diamond. DETAILED DESCRIPTION

[0016] The present invention will be further described below by way of examples.

[0017] Example 1

[0018] A method for physically purifying diamonds comprises the following steps:

[0019] 1) The synthesized graphite column is subjected to electrolysis, ball milling and shaking to obtain diamond material with a particle size of less than 1 mm;

[0020] 2) placing the diamond material from step 1) in a mixture of water and a surfactant for ultrasonic cleaning, so that the diamond and graphite are separated into layers in a cleaning basin; the surfactant is ethanol; and the ratio of water to ethanol is 1:8;

[0021] 3) Collect the upper graphite layer and the lower diamond layer respectively, collect the diamond and graphite mixture in the middle boundary layer and repeat the operation in step 2);

[0022] 4) The collected lower layer diamonds can be subjected to electrostatic separation. The electrostatic separator used for electrostatic separation is a DXJφ320×900 high voltage electrostatic separator.

[0023] The electrostatic separator includes a drum and a high-voltage electrode. The positive pole of the drum is grounded, and the high-voltage electrode is the negative pole. The diameter of the drum is relatively large, and there is a certain distance between the drum and the high-voltage electrode to form an electrostatic field between the drum and the high-voltage electrode, so that the conductive substances and non-conductive substances in the diamond material that comes into this electrostatic field with the drum are separated.

[0024] Diamonds are poured from the feed hopper, and are evenly discharged from the feed roller to the vibrating feed plate through the gate. Then the diamonds are fed into the drum and brought into the high-voltage electric field by the drum. The electric field has a larger action area and more electrons. Both conductive particles and non-conductive particles have more opportunities to absorb electrons here. The conductive graphite particles absorb the charge and transfer it quickly. Under the combined effects of centrifugal force, gravity and electricity, they fall from the front of the drum and gather together. After the non-conductive diamond particles acquire the charge, they cannot quickly transfer the acquired charge due to their poor conductivity. There is a lot of residual charge, which generates a large mirror attraction on the barrel surface and is sucked on the barrel surface. As the drum rotates to the rear, there is no electric field behind the drum, and the diamond particles can fall down into the collection hopper. In addition, there is a brush at the rear of the drum, which contacts the surface of the drum and can brush the diamonds that do not fall from the drum surface into the collection hopper.

[0025] After being processed by the electrostatic separator, the impurity graphite in the diamond material is further removed to obtain pure diamonds, and the obtained diamonds are not lost, thus avoiding the waste of magnetic diamonds.

[0026] Example 2

[0027] A method for physically purifying diamond, which is different from Example 1 in that the surfactant is acetone; and the usage ratio of water to acetone is 1:5.

[0028] Example 3

[0029] A method for physically purifying diamond, which is different from Example 1 in that the surfactant is acetone; and the usage ratio of water to acetone is 1:10.

Claims

1. A method for physically purifying artificial diamonds, characterized in that: The following steps are involved: 1) The synthesized graphite column is subjected to electrolysis, ball milling and shaking to obtain diamond material with a particle size of less than 1 mm; 2) placing the diamond material from step 1) in a mixture of water and a surfactant for ultrasonic cleaning, so that the diamond and graphite are separated into layers in a cleaning basin; the surfactant is ethanol or acetone, and the mixing ratio of the surfactant to water is 1:5 to 1:10; 3) Collect the upper graphite layer and the lower diamond layer respectively, collect the diamond and graphite mixture in the middle boundary layer and repeat the operation in step 2); 4) The collected lower layer diamonds can be subjected to electrostatic separation.