Method of cleaning diamond

FIELD: production of diamonds of jewelry property; high-quality cleaning of diamonds.

SUBSTANCE: proposed method includes stage-by-stage treatment of diamond by mixture of acids under action of microwave radiation; at first stage, use is made of nitric acid and hydrogen peroxide at volume ratio of components of 10:1, respectively; at second stage, volume ratio of mixture of concentrated nitric acid, hydrochloric acid and hydrofluoric acid is 6:2:1, respectively; diamond is treated at temperature not higher than 210°C, pressure of 35 atm as set by loading ratio of autoclave equal to 1:10 at power of oven of microwave radiation of 1200 W; duration of each phase does not exceed 40 min. Proposed method ensures perfect cleaning of diamonds from contamination of mineral and organic nature including bitumen compounds on surface and in cracks of diamond.

EFFECT: enhanced efficiency; reduction of time required for process.

 

The invention relates to improved clarity and color characteristics of gem-quality diamonds and can be used for high-quality diamond cleaning simultaneously from surface contaminants and deposits of mineral and organic origin inside the cracks of diamonds.

On the surface and in the cracks of natural diamonds often have contamination resulting from deposition on the surface and in the cracks of diamonds from fluid and melt phases of different minerals, bitumen, and pollution are often interbedded nature.

The presence of contaminants on the surface and in the cracks of the crystals jewelry diamond complicates the sorting of raw materials in color and defects, resulting in significant economic losses.

There are different ways of cleaning the surface of a diamond, for example processing flow of electrons or ionizing radiation and ultrasonic processing (JP 6183893 A, Sumitomo Electric Ind. Ltd., 05.07.94), supersonic treatment in solutions of alkalis, hydrogen peroxide, organic or inorganic acids (US 4339281 A, RCA Corp., 13.07.82), the autoclave with concentrated nitric acid at elevated temperature (EN 2163222 C2, AOOT "Abrasive plant "Lenin", 20.02.2001). However, these methods provide only clean the surface of the diamond or from metallic impurities and ostad is in graphite, or organic contamination during the extraction of diamonds, or clean the surface to improve fastener diamond jewelry.

The known method is universal cleaning diamonds, consisting in the sequential processing of diamonds in autoclaves organic solvents and hydrogen peroxide, an alkaline reagent, a mixture of concentrated sulfuric, hydrochloric and nitric acids at a temperature of 250-500°and high vapor pressure, followed by washing with distilled water and a final treatment with a mixture of nitric and hydrofluoric acids. (US 5133792 A, Anshal Inc., 28.07.92, US 5346090 A, Anshal Inc., 13.09.94.) This method is characterized by low productivity due to mnogostadiinost the process, connected with the need of special hardware equipment carrying out reactions at high temperatures and vapor pressure (US 5 346090 And 13.09.94).

The disadvantages of the known methods is that each of these methods has a narrow application, and is used for specific types of pollution. Clear regardless of the type of impurities is achieved only in the method described in patent US 5133792, but the process involves many stages.

Closest to the invention is a method of chemical cleaning diamonds, including the processing of natural diamonds when heated to 220-250°and when the appreciation is nom the pressure in the autoclave, the reaction capacity of PTFE within 1.5 to 3 hours with a mixture of concentrated nitric, hydrochloric and hydrofluoric acids when they are volumetric ratio of 3:1:(1-2), respectively (SU 1104791 A, the state Treasury and GUI rare-metal industry "GIREDMET", 20.12.2000).

This method allows you to clean diamond jewelry only from contaminants contained on the surface of the crystals and the resultant enrichment of diamondiferous rocks, which are presented in the form of traces of metals, inorganic compounds and oils. The method does not provide high-quality cleaning of mixed origin, which appeared during the growth of diamond or later as a result of various secondary reactions as redox potential of the reaction mixture used is insufficient for the oxidation of the bitumen. Bitumen screen access the reaction mixture to mineral impurities, and therefore this method does not allow to dissolve mixed types of pollution, where the mineral phases formed during the growth of crystals, such as grenades, stones, spinel replaced with bitumen contamination.

Object of the invention is the production of diamonds of gem quality, and the technical result that can be obtained by carrying out the claimed invention is to provide a full treatment of natural diamonds of mixed contamination of mineral and organic origin is s, including bitumen on the surface, in cracks of diamonds, and the reduction in the duration of the cleaning process.

The effect is achieved that the way to clean diamonds, including diamond processing in an autoclave with a mixture of concentrated nitric, hydrochloric and hydrofluoric acids at elevated temperature and at elevated pressure, the processing of the mixture of acids are Paladino under the influence of microwave radiation at the first stage, a mixture of nitric acid and hydrogen peroxide at a volume mixing ratio 10:1, respectively, and the second volumetric ratio mixture of concentrated nitric, hydrochloric, and hydrofluoric acids is 6:2:1 respectively.

The process is carried out at a temperature of not more than 210°C, the pressure is set by the fill factor of the autoclave of 1:10, and 25 ATM when the capacity of the furnace microwave-1200 watts. The processing time at each stage is not more than 40 minutes

It is widely known that a strong high-frequency electromagnetic radiation with centimeter and sub-centimeter wavelength capable of accelerating the course of many chemical reactions. A modern interpretation of this phenomenon relates the increase in the rate of reaction not only with increase in thermal exponential factor in the equation Arren the USA, describing the kinetic constant of the reaction, but also with the influence of harmonic oscillations of a certain frequency on preexponential multiplier. This results in energy molecular excitation and increases the atomic bond energy due to the transition of electrons in extrinsic in normal conditions of high-energy orbitals.

The selected modes of reactions dissolving dirt under microwave radiation in a mixture of nitric acid and hydrogen peroxide allow to oxidize bitumen in deep cracks to carbon dioxide and water not more than 40 minutes, freeing the surface of the mineral contaminants for further reaction with a mixture of nitric, hydrochloric and hydrofluoric acids.

Found experimentally volume ratio mixture of nitric acid: hydrogen peroxide equal to 10:1, and a three-component mixture of concentrated acids - nitrogen : salt : hydrofluoric equal to 6:2:1, when exposed to microwave radiation at a power of microwave oven radiation, 1200 watts, provide an opportunity for the two stages of the process to dissolve the connection of different mineralogical composition not only on the surface, but in the cracks of diamonds, not pre-sorting the crystals on the type of contamination. When the heating temperature is not more than 210&#HWS and the pressure range from 15 to 40 atmospheres proposed method allows to remove contaminants with efficiency, close to 100%.

Examples of embodiment of the invention.

For treatment were selected natural diamond crystals containing impurities with varying degrees of iron-containing contaminants and bituminization in open deep cracks. The total weight of the selected diamond was 77,92 carats, a total of 119 samples of size classes of groups: +1,8 CT., 4-6 gr, gr 3, 2gr, +11. Each diamond has been studied for contamination visually using an optical microscope MBS-10. The diamonds were placed in Teflon-glass autoclave with a capacity of 100 ml and was filled in the reaction mixture prepared as follows: 100 ml of concentrated nitric acid is poured into a plastic measuring Cup, then add 10 ml of 30%hydrogen peroxide, maintaining the volumetric ratio of 10:1. The reaction mixture was added 10 ml for every 50 carats (10 grams) of diamonds that match the fill factor of the autoclave 1:10, then the reaction container was closed with a lid. After that, the autoclave was placed in a microwave to dissolve the samples. For the processing of used laboratory equipment microwave sample preparation type MARS 5 with a set of high pressure autoclaves. Asked furnace power microwave radiation, 1200 watts and a temperature of 210°C. Control the temperature variation was carried out using the standard control unit, with which the op. The pressure measured by the pressure sensor and reflected on the display. The processing time was set also on display and was 40 minutes.

After heating the autoclave was cooled to 35±5°, diamonds were washed with bidistillate and filled the second reaction mixture consisting of 60 ml of concentrated nitric acid, 20 ml of concentrated hydrochloric acid and 10 ml of concentrated hydrofluoric acid, the corresponding volume ratio of 6:2:1. The second cleaning cycle was performed by the same parameters, after which the crystals were washed again with bidistillate, when this was added 10 ml of water and was carried out replacement of the acidic residues in the cracks of the crystals with water for 15 minutes at a temperature of 150°C. After which the crystals were removed from the autoclave and dried in air. The quality and degree of purification of the diamond surface was determined visually using an optical microscope MBS-10.

The proposed method has provided the following results:

1. Improved visual color perception of the total mass of rough diamonds (77,92 CT., 119 pieces).

2. Ugrasena in the size class +1,8 CT. were excluded completely.

3. In the size class 4-6 gr 10 crystals with the presence of oil products (bitumen contamination) completely cleared 6 pieces, in the rest of the degree of purification achieved 94-96%.

Three iron-enriched diamond size groups gr 3, 2 gr +11 absolute purification has reached 90% of the crystals seen in other small remnants of dirt.

5. The proposed method allows cleaning with efficiency close to 100%, clear tar and iron-enriched fill in the cracks.

6. Because a standard set of work autoclaves for the microwave oven of the apparatus used MARS 5 is 11 units and one control, then downloading one autoclave 50 carats of diamonds can be cleaned about 500 carats (100 grams) natural diamonds for a period of not more than 1.5 hours.

The way to clean diamond, including its treatment in an autoclave at elevated temperature and pressure with a mixture of nitric acid, hydrochloric, hydrofluoric, wherein processing the mixture of acids are Paladino under the influence of microwave radiation, and in the first stage, a mixture of nitric acid and hydrogen peroxide at a volume mixing ratio 10:1, respectively, and in the second phase volume ratio mixture of concentrated nitric, hydrochloric, and hydrofluoric acids is 6:2:1 respectively, while the diamond is treated at a temperature of not more than 210°C, a pressure of 25 ATM, set the fill factor autoclave equal to 1:10, the capacity of the furnace microwave radiation 1200 watts and the duration of each stage is not bol is e 40 minutes



 

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