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What are the factors that affect the quality of silver powder in silver electrolysis?


Silver electrolysis is to be able to produce high purity electrolytic silver, but in this process, there will be some factors that affect the quality of silver powder, and then Xiaobian will bring you a detailed understanding of what is silver electrolysis.
In the process of silver electrolysis, according to the different properties and behaviors of various elements contained in the silver anode, it can be divided into the following categories:
1. Metal ions with negative electrical properties than silver, such as zinc, iron, tin, lead, arsenic, etc. The contents of Zn, Fe and as are very small, which have little influence on the electrolysis process; Tin enters into anode slime as stannate; One part of lead enters into the solution, the other part is oxidized to form PbO2 and enters into the anode slime. A small amount of PbO2 adheres to the surface of the anode plate, which will affect the dissolution of anode silver to a certain extent.
2. Gold and platinum group metals with higher electrical properties than silver. These metals generally do not dissolve and enter the anode slime. When its content is very high, it will stay on the anode surface, hinder the dissolution of silver, even cause the anode passivation, increase the anode potential and affect the normal process of electrolysis. But in the actual production, some platinum and palladium enter into the electrolyte, and when the electrolysis conditions are not controlled properly (too high electrolysis temperature and large current density), the amount of palladium and platinum entering into the electrolyte will increase. Because the potential of palladium (0.82v) is close to that of silver (0.8V), palladium and silver may precipitate together at the cathode, thus affecting the quality of silver powder.
3. Compounds that do not undergo electrochemical reaction, such as ag2se, ag2te, cu2se, etc., will enter the anode slime because their electrochemical properties are very small and do not change during electrolysis. However, when selenium exists in the anode slime, it can dissolve together with silver in weak acid electrolyte and precipitate on the cathode. However, in high acidity (about 1.5%) solution, selenium in anode does not enter the solution.
Silver Electrolysis
4. Copper, bismuth and antimony with potential close to silver. These metals are most harmful to electrolysis. In the process of electrolysis, one part of bismuth forms basic salt and enters anode slime, the other part enters solution as bismuth nitrate. The behavior of antimony and bismuth is similar. After antimony and bismuth accumulate in solution, they will precipitate on cathode and affect the quality of silver powder. Bismuth nitrate will hydrolyze to produce basic salt precipitation when it is electrolyzed under low acid condition, which will affect the quality of silver powder. The content of copper in the anode is high, but in the normal production process, copper generally does not precipitate in the cathode, but when the electrolyte stirring cycle is poor, the concentration of silver ions in the electrolyte drops sharply, and the content ratio of silver to copper is less than 2:1, copper will partially precipitate on the cathode. In addition, Cu2 + may be reduced to Cu + in the process of Cu2 + moving to cathode in solution, and Cu + is oxidized to Cu2 + at anode, which consumes electricity. Especially when the anode with high copper content is electrolyzed, only silver can be precipitated from the cathode, and 3.4g silver will be precipitated from the cathode for every 1g copper dissolved in the anode, which is easy to cause the sharp drop of silver ion concentration in the electrolyte. This is the cathode, there is a risk of copper precipitation. Therefore, when electrolyzing the anode with high copper content, we should often extract part of the electrolyte with high copper content and add part of the silver nitrate solution with high concentration. However, it is also advantageous to maintain a certain concentration of copper in the electrolysis process, because copper can increase the electrolyte density and reduce the sedimentation rate of silver ions.
  The factors that affect the quality of silver powder in the process of silver electrolysis are as follows:
1. The impurity content of silver anode plate is unstable, such as bismuth, copper, antimony, selenium and other elements which exceed the standard will precipitate together with silver in the cathode under certain reaction conditions, affecting the quality of silver powder and consuming power at the same time; When the content of lead, platinum, palladium and other metals exceeds the standard, it may also consume electric energy and affect the precipitation of silver;
2. Limited by the conditions of production equipment, some links in the actual production process will affect the quality of products;
3. In the production process, manual operation is used in many places, if the operation is not at the right time, the product quality will also be affected.
    Improvement measures:
1. Control the quality of anode plate;
2. Strengthen the management of groove surface and put an end to illegal operation;
3. Improve operating procedures and equipment.


Post time: Apr-29-2021