Spent Acid Peroxide questions

[Palladium]

I think it was based on 37.5 %

 

[freechemist]

The most important reaction in AP-solutions to dissolve copper is the oxidation of metallic copper with Cu(2+)-ions already present in solution through the preliminary combined action of acid (HCl) and peroxide (H2O2) on metallic copper. Once formed, Cu(2+), dissolved in an excess of aqueous HCl reacts with metallic copper to form Cu(+), itself being reduced to Cu(+). So the actual driving reaction in the AP-process can be formulated as: Cu(metal) + Cu(2+) => 2 Cu(+). Cu(+) in HCl-solution will be reoxidized quite rapidly by atmospheric oxygen (from the air) to Cu(2+). Solutions of only Cu(+) in aqueous HCl are colourless, whereas solutions containing only Cu(2+) range from blueish to yellowish green in colour, depending on Cu- and HCl-concentration. Solutions, containing both species, Cu(+) and Cu(2+) are often very dark coloured.
Aeration thus is most important in the AP-process, because it will reform Cu(2+), which will dissolve more metallic copper, according to the following reaction stoichiometry: 4 CuCl + O2 + 4 HCl => 4 CuCl2 + 2 H2O. From this it is evident, that reoxidation of Cu(+) by aeration consumes acid through formation of water out of the reduced oxygen. And at last, most important for the AP-process: Cu(2+) in HCl is not able to oxidize metallic gold.

freechemist

 

[lazersteve]

Ross,

The copper chloride etchant pdf on my website wil give you a complete understanding of the AP reaction if you take the time to study it throughly.

Key factors are pH of the solution and copper concentration.

Steve

 

[Palladium]

Well look what the cat dragged in.

Starting to worry about you there Steve. How's life treating you?