Dear Bala

I hope this method can applied for your problem, but i don't make sure, where in order to eliminate unwanted phases that form in my compound during the crystallization process KCN chemical treatment was applied to the samples, this procedure can be concluded the following steps:

1- Solution of KCN at 10% w/w prepared.

2- The samples were sequentially submitted to the KCN bath.

3- The samples were submitted to solution of alcohol/deionized water at 50% vol/vol.

4- finally,The samples were submitted to solution of deionized water. 

Each step had a duration of 2 min.

Finally, all samples were dried with a N2 gas flux.

This procedure from paper but i don't remembered

With my best regards  

The copper(II) oxide layer formed over metallic copper can be dissolved with hot dilute acetic acid. However, some attack to aluminium, not strong and seemingly acceptable for the intended application, is to be expected. Such attack would be partially due to galvanic corrosion, since both metals would be in contact.   

Hi~

Concentrated hydrochloric acid can remove CuO easily. Diluted HCl is OK, too. The cooper won't react with acid.

You may also try boiling the specimen in H2C2O4 and K2C2O4(1:2) solution in a water bath, cause Cu(II) could react with C2O42- forming coordiation compounds.

Hope this could help you.

Thank you all, for your solutions. i will try it

If the diluted HCl or diluted acetic acid is used to remove oxides of copper. Will that react with the Cu(0)?

If you don't want to use chemicals, you can also put some salt on a sliced Lemon and use it as a "brush" or you could use a mixture of water, vinegar essence (5 parts water, one part vinegar) and salt.

Dear Bala Narasimha Guniputi,

I can propose two ways by which the black layer(copper oxide ) has formed on the surface can be removed.

(1) Simple way is by scrubbing the metal surface with the lemon covered in salt to remove the copper oxide. The acids in the lemon loosen the copper oxide and the abrasiveness of the salt crystals scrapes away the loosened particles.

(2) Another way, anhydrous vapor containing a carboxylic acid compound and one or more solvents selected from hydrocarbon and ether solvents could be best solution to clean copper oxide.

Ashish