Stripping:

Stripping is the removal of the extracted solute from the organic phase for further processing or analysis. It is the reverse of extraction. The usual procedure is to shake the organic layer with a volume of water alone or water containing an appropriate concentration of acid, an oxidizing or reducing agent or a masking agent. The metal ion is then back extracted in the stripping aqueous phase. The conditions employed depend upon the metal ion and the particular extraction system and are such that they promote the reversal of extraction. Pure water or water adjusted to an appropriate pH/ molarity of acid are the more popular and convenient stripping agents. Washing the organic layer with an oxidizing or reducing agent changes the metal ion to be stripped in an oxidation state in which it is not extracted under the specific conditions. Similarly, by washing with aqueous solution containing a masking agent like cyanide, tartarate, citrate, EDTA etc. the metal ion may be brought back to the aqueous layer because these complexing agents form a stronger complex which is not itself extractable.

 The different approaches being deliberated upon are as follows:

i) pH of the aqueous phases

ii) Acid molarity of the aqueous phase

iii) Presence of masking agents in the aqueous phase

iv) Selective stripping from the organic phase