Diamond Micropowder Rough Purification Process

Usually, the raw material of diamond powder is mostly low-grade RVD diamond or diamond powder synthesized by explosive method, and the raw material itself contains a small amount of impurities such as graphite, catalyst metal and pyrophyllite. At the same time, a large amount of metal impurities will be introduced in the later crushing and shaping process. High impurity content will reduce the overall hardness of diamond and affect the performance of deep processing tools. In order to meet the requirements for product purity in the subsequent grading process, these impurities must be removed before being transferred to the grading process.

 

At present, chemical impurity removal and electrolytic purification techniques are commonly used to purify artificial diamond micropowder. The latter is mainly used when there are many alloy catalysts in the diamond material, so as to achieve the purpose of recycling catalyst metals. However, in actual work, due to the slow dissolution of the alloy catalyst and low production efficiency, it is difficult to meet the requirements of production development. Relatively speaking, the chemical method uses different chemical reagents to treat the impurities separately according to the different chemical characteristics of the impurities in the diamond, and can obtain a better purification effect, that is, the "three removal" process commonly used in the industry: acid removal of alloy catalyst, strong The oxidant removes graphite, alkali-melted pyrophyllite and other three-stage work. According to the good chemical stability of diamond and the characteristics of not reacting with acid and strong oxidant at high temperature, chemical methods are generally used to purify diamond.

The main impurity of the diamond that has completed the crushing and shaping process is metal, which can undergo redox reaction with acid to form soluble salts. Using this feature, it can be treated with suitable acid to remove most of the metal impurities, and at the same time It can also remove impurities such as graphite.

 

The general operation method for acid treatment is: weigh a certain amount of diamond powder, put it into a 5000ml glass beaker or other acid-resistant and high-temperature-resistant container, add an appropriate amount of acid, and place the beaker on the electric heating plate or industrial heating plate in the fume hood. Heating on an electric furnace, as the temperature rises, the reaction gradually becomes more intense. After the reaction is completely stopped, stop heating and remove the container from the heat source. into the grading process.

 

In industrial production, since the final classification is completed, the fine purification treatment must be carried out again. The rough purification process should reduce the cost as much as possible under the premise of meeting the requirements of the classification process. The chemical reagents generally used are mostly industrial pure. The following table shows the rough purification process. Specific process parameters used in various treatment processes:

Due to the low content of pyrophyllite and graphite in diamond raw materials. In order to simplify the treatment process, the general rough purification process does not carry out special treatment on it. If there are special requirements for the product, after the classification is completed, the finished product will be specially treated in the later stage.

 

In the production process of diamond micropowder, various chemical reagents are used in the purification process, and a large amount of harmful gas and waste water will be discharged during the treatment process, which will endanger the occupational health of the operator and pollute the environment. In order to improve the operator's working environment and reduce waste gas and waste water discharge. Some diamond micropowder production enterprises have begun to try to change the original purification method, replacing the original open beaker heating process with a large closed reactor.

 

The reaction kettle adopts electric heating or indirect heating of heat conduction oil, and the material is quartz glass or steel lining with enamel. Reactors of various specifications such as 20 liters, 50 liters, and 100 liters can be selected according to the production scale. The equipment is equipped with automatic stirring, automatic temperature control, waste gas neutralization and absorption, and acid vapor condensation and reflux devices. The use of reactors for purification treatment can not only increase the single treatment capacity and reduce the labor intensity of personnel, but also have remarkable effects in saving energy, improving working conditions and protecting the environment.