Seeking help with copper electrolysis issues
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In an electrolytic copper production facility with an annual output of 5 wt, extensive passivation of the anode plates is occurring at present; moreover, the dissolution of the anodes accelerates at the liquid surface, causing the plates to break off easily from those areas. Anode plate composition: 99.4%–99.5% copper ； Lead: 0.10～0.17% ； Nickel: around 0.10% Electrolyte composition: copper around 50–54 g/l, acid around 190 g/l, nickel around 14 g/l ； The temperature is around 65 degrees. The purification process has not yet been started; 6 lead plate tanks have been used for copper removal. It is likely that the anode plates contain a high level of copper, and the electrolyte contains a slightly high level of nickel. We are about to start the liquid purification process. Please use your experience to help determine what the causes might be and how to eliminate them Thank you all
This post was last edited by FILTRATION-MAN on 2009-11-30 12:35 -- Well done! Emuonline, it seems like you are taking your tasks very seriously. Praise given. I hope that everyone, whether posting requests for help, discussing issues, or looking for information and electronic documents or books, will try to explain the background and relevant details clearly, as after all, everyone’s time is very valuable. A proper, detailed description can bring more convenience to oneself as well as to others (including those who can offer help). Every member who posts a thread should, after writing it, take some time to consider whether it can be improved further --
Thank you for the moderator’s reply. This is my first time visiting your forum, and I’m glad to have found peers who have practical experience in copper electrolysis. I’m also pleased to see many alumni from Central South University; I graduated in 2000, majoring in metallurgical chemistry. I hope to exchange ideas with everyone and learn from one another. The issue of anodic passivation in the workshop has been present for some time now, and it’s quite troubling. Hehe; I hope everyone will actively participate in the discussion and share their opinions. If there is any additional data needed, please mention it in your replies.
Anodic passivation has the following points. (1) Perhaps the temperature is too high or the sulfuric acid is too concentrated; add some water, with the temperature generally around 45–50 degrees. (2) Perform a silver analysis; too high levels of silver can also accelerate anode passivation. (3) Some reagents need to be added to the electrolyte, such as bone glue and thiourea; have you added them?
Just my personal opinion: The original poster is into electrolytic refining. I haven’t worked in this field; I’ve only done electrodeposition of copper (an extraction~~electrodeposition process). 1. Passivation may be caused by the following two factors: too high a copper content in the electrolyte, which increases the voltage required to transfer copper from the anode to the cathode. The high content of impurity ions in the electrolyte causes electrochemical reactions that would not occur at low concentrations to take place, thereby competing with the main reaction. 2. The reason for the accelerated anode dissolution at the liquid surface may be, as mentioned upstairs, a lack of additives. Role of the additive: It exhibits strong adsorption in areas where dissolution occurs rapidly, resulting in an increase in the overpotential there; a higher electrolytic voltage is required to facilitate dissolution in such areas. Thereby achieving uniform dissolution of the anode. . Feel free to discuss when you have time.
4# xhq1635858 Thank you for your reply! The silver content in the composition of the anode plates used is very low, generally below 400 g/t ； The additives are bone glue and thiourea, at approximately 35 g/t of copper production ； Regarding the electrolyte temperature, I believe that if it is below 50 degrees, it will reduce the activity of the electrolyte and make passivation more likely to occur; articles in some journals also mention that increasing the temperature can mitigate the effects of passivation. Welcome to continue the discussion
Is this student involved in copper electrowinning in the Yunnan area? I also think the electrolyte has relatively high levels of copper and acid; I’m planning to carry out a purification treatment now ； Regarding the effect of additives, I believe a higher amount of bone glue can cause an increase in the cell voltage, as well as exacerbate passivation ； However, thiourea should not have much of an effect.
Your problem is most likely due to an excessively high sulfate concentration and a high current density. During electrolysis at such high current densities and with high sulfate levels, the concentration of copper sulfate on the anode surface can locally exceed its solubility limit; this leads to saturation adsorption on the anode surface, resulting in passivation. The cell voltage rises and the plates heat up, which can cause the plates to burn out. The solution is to reduce the concentration of copper sulfate in the electrolyte by adding some pure water. However, the most advanced technology at present is high current density, reverse-current-cycle electrolysis technology, which is specifically designed to address this passivation issue under high current densities :)
I am very interested in understanding the impact of electrolyte concentration on the electrolyzer and the electrolysis process, as this would facilitate the concentration and reuse of waste electrolytes. I hope my seniors can share their knowledge with me at zhjnavy015@163.com
Concentration? What concentration? Copper concentration? Acid concentration? Additive concentration. . . .
Your anode condition isn’t likely to cause anodic passivation; what’s the short-circuit rate? I guess it’s quite high, right?