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How do I separate ferrous sulphate immersion coppering solution?

While coating steel wire with copper with a bath containing CuSO4 and H2SO4, slowly the concentration of ferrous sulfate ⇦this on eBay or Amazon [affil links] starts increasing and at one stage the FeSO4 conc. goes up to a level so as to reduce the reaction speed thereby affecting copper coating. So. we have to replace the bath. If we could find out a way of reducing the FeSO4 concentration then we can continue to use the solution. Can somebody suggest a method for doing so?

Regards.

Rakesh Bansal
Manufacturer - Parwanoo, HP, India
2007

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If you are doing immersion plating of steel with copper, you are bound to get a build-up of iron in the bath - that is how the immersion process works. Basically, the copper is more electropositive than the iron, so the iron is dissolved out and replaced by metallic copper. This results in a build-up of iron in solution. Quite simply, you are using up your copper solution and need to replace the copper ions; you can't get something for nothing in science, so you have to spend some money somewhere. If you want to remove the iron from solution, one way will be to increase the pH to form hydroxides; this will throw out both copper and iron hydroxides. You can then add ammonia ⇦this on eBay or Amazon [affil links] solution to the gelatinous hydroxides to form a deep blue solution of cuprammonium ions and filter off the iron hydroxides. You can then recover the copper ions by reducing the pH to about Ph = 1-2 with sulfuric acid and drive off the ammonia with heat, which if you have any sense, you will recover with a scrubber and reuse it. This process will be expensive, so it is better to accept that you are using chemicals that must be replaced.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007