Redox resin process

Process for extracting a reducible metal ion from an aqueous solution containing it, wherein the pH of the aqueous solution is from 1.5 to 6, which comprises contacting said solution with an extracting amount of a water-insoluble granulated redox resin obtained by a process which comprises the following steps, in sequence:

• i. polycondensating in suspension in a water-immiscible inert diluent containing an alcohol of 3 to 20 carbon atoms, a mixture of formaldehyde, pyrocatechol and an aromatic diamine, in which mixture the diamine constitutes 5 to 35 mol % of the mixture of pyrocatechol and diamine, the formaldehyde constitutes 1.1 to 1.5 moles per mol of pyrocatechol and 2.2 to 3 mols per mol of diamine,
• ii. heat treating the polycondensate or reaction mixture containing the polycondensate at about 70.degree. to about 110.degree.C., and
• iii. removing the alcohol present in the resulting resin.