Silver extraction and refining methods

The extraction and refining of silver is mostly carried out in cyanide medium and sodium thiosulfate medium. There are not many studies on the extraction of silver in hydrochloric acid and nitric acid medium.

1. In hydrochloric acid medium, silver mainly exists in the form of silver chloride. Only when the concentration of chloride ions is quite high, complexes such as AgCl and AgCl are partially formed, and the stability is poor. Therefore, precipitation methods are commonly used to recover silver, but there are few studies on silver extraction.

2. In nitric acid medium, silver mainly exists in the form of silver nitrate, which has a high solubility, and nitric acid is a strong oxidant. Generally, the extraction agent is easily damaged or aged under the action of strong oxidants, so the extraction agent is required to have good oxidation resistance. Therefore, there are not many effective extraction agents for extracting silver. The more effective ones are dialkyl sulfide, such as diisooctyl sulfide, petroleum sulfide, etc.

3. In cyanide medium, silver is similar to gold and can generate cyanide complex Ag(CN)z, which can be extracted by the extraction agent used to extract Au(CN)².

4. In sodium thiosulfate medium, silver can generate Ag(S₂O₃), which can be extracted by certain extraction agents.