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Controlling Electric Current in Electrowinning (3 replies)

9 months ago
Hauptsturm 9 months ago

What do you think about controlling the electric current through the dosage of sodium hydroxide?We have problems with control the electric current in the electrowinning. The actual concentration is 1,5% (NaOH), the pH is 11,0 to 11,8 in the solution. But, I know that pH must be 12,5. However, the increase the concentration of soda can cause the other problems. I would like you comment and talk about the maximum concentration of soda (sodium hydroxide) that you can practice.

It isn't always possible to control the current through the rectifier. Conditions of liquor greatly influence the electrical conduction.

Tony Verdeschi
9 months ago
Tony Verdeschi 9 months ago

I saw your comments to another query raised recently and I assume you are still trying to work with the elevated copper issue, with this query. It has been suggested that your current efficiency decreases as gold concentration in the solution decreases. It is the reduction of other metals in solution such as copper and silver that also occur with the deposition at the cathode which also reduces your current.

Basically as gold concentration in the eluate decreases more and more of the cathode will become inactive. Also keep the packed cathodes no thicker than 4-6 cm for max efficiency. Make sure the flow is not to high- about 0.5m/min, but if too slow you'll burn your cathodes. Most of those other metals will deposit before gold, thus reducing the efficiency of the electrowinning. It may not be your caustic, but test you caustic strength.

Marshal Dienes
9 months ago
Marshal Dienes 9 months ago

pH 12 works best for me during electrowinning. The biggest improvement I can suggest is to use lower concentrations of cyanide during your lixiviation to avoid dissolving copper and base metals in the first place. Prevention is worth a pound of cure!

9 months ago
Obergruppenfuhrer 9 months ago

Caustic levels below 0.75% will cost you electrowinning efficiency. Many operations run as high as 2% caustic. It is important to determine the caustic level by titration and not just control by pH. It is also important to control pH in the adsorption tanks.

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