The preparation process of high-purity materials is mainly divided into two categories: wet purification and pyrometallurgical purification. Specific methods include regional melting, solvent extraction, electrolytic refining, etc. The following is a brief explanation of common processes:

1、 Wet purification

Separating impurities through chemical reactions, suitable for metals such as gold, silver, zinc, cobalt, etc. Typical methods include:

1. Solvent extraction method: using organic solvents to selectively extract target metal ions, such as using P507 extraction process to separate nickel and impurities in the preparation of high-purity cobalt.

2. Electrolysis method: Metal can be purified by electrolysis. For example, Toho Yazo in Japan can purify iron to 5N level, but domestic technology currently only reaches 3N level.

3. Ion exchange method: using resin to adsorb specific ions, commonly used for the preparation of high-purity cobalt.

2、 Pyrometallurgical purification

Separating impurities based on differences in physical properties mainly includes:

1. Regional melting: Selective solidification and purification through the movement of the melting zone, divided into horizontal zone melting and suspension zone melting, suitable for semiconductor materials, high-purity zinc, etc.

2. Chemical vapor deposition: The preparation of high-purity materials, such as gamma alumina, by vapor phase reaction deposition.

3、 Joint process

A single method is difficult to achieve ultra-high purity, and multiple process combinations are often used. For example, high-purity zinc is prepared by combining electrolytic refining, vacuum distillation, and regional melting, while high-purity cobalt is prepared by combining chelation extraction and regional melting.