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"Electrode for Electrowinning Nickel"
Q. I have nickel solution waste from electroplating industry. Our company try to find an effective electrode to recover nickel from that solution by electrowinning process. We've tried to use Cu as electrode but not reach satisfaction result. Therefore, we ask you to help us to find right electrode.
- Tangerang, Banten
A. You don't say what type of nickel bath is being processed, so an exact selection of the correct electrode is hard to determine. For the sake of the answer here, lets assume that it is a decorative or bright nickel (Watts or similar). You also do not identify whether you are trying to find an anode material or a cathode material. I'll try to explain both here.
These baths contain a fairly high amount of chloride and will therefore require an electrode that is resistant to chlorine attack, as chlorine will be evolved at the anode electrochemically. Other base metals are not suitable for use as anodes, and the use of graphite blocks, lead, etc. all have issues withstanding what is a fairly aggressive environment. The complicating factor here is also the production of oxygen at the anode too. Most materials are resistant to either chlorine or oxygen, but not both, or at least not well.
You should look at inert or insoluble catalyst coated anodes applied on an inert substrate. Usually, the best bet is to use a layered inert anode material. The chlorine attack usually occurs on the substrate itself, so it should either have a high chlorine overpotential (such as tantalum), or it can be titanium with a small layer of platinum electroplated to it. Then, the electrode substrate can be coated with an oxygen evolving catalyst, such as iridium dioxide or similar coatings. This will give you an excellent lifetime in most of application, however care must be exercised not to allow the electrode to be cathodic, or the coating will be quickly lost.
We have found that a copper cathode sheet will work very well in nickel recovery applications, if the material is flashed with a nickel layer prior to use. Also, care must be exercised to not allow the cathode to be exposed to air after the electrowinning process is started, or the nickel will quickly passivate, making it all but impossible to restart the electrowinning process. In straight nickel plating, you can remove the passivation layer from nickel anodes by immersion in nitric acid or some other activator process - here, you are not dealing with an annealed material, but a substantially grainy deposit, and the material will continue to oxidize or still be partially passivated.
You might also look at using thin nickel sheet that has been slit and expanded as a cathode. It increases the surface area significantly, and the nickel to nickel grain structure allows you to electrowin a very refined deposit.
wastewater treatment specialist - Warminster, Pennsylvania
January 2, 2009
Q. We are a recycling company dealing with heavy metal containing scheduled wastes namely from water treatment plants. Usually the sludges have high content of Aluminium. But those from industry generally have high Nickel content;Around 500-500 thousand ppm of Nickel. I would like to know how electrowinning can effectively and selectively remove Nickel.shri prasanthi
- Pahang, Malaysia
September 13, 2011
Q. We have NiCad battery scrap 200 mesh in powder.
Our two questions are as below:
We are interested in obtaining nickel and also interested in obtaining cadmium
Please inform us we can use electrowinning or electrolytic
amp / volts/ mol chemical/ ratio, etc., and also inform us anode and cathode material metals to use.
- Lahore, Pakistan