Interaction between 2(4)-Aminopyridines and Ions of Platinum and Transition Metals in Aqueous Solutions under Conditions Approximating Their Extraction Isolation and Separation

A study is performed of the interaction between 2(4)-aminopyridines (2(4)-AP) and Pd(II), Pt(II), Pt(IV) and accompanying ions Ni(II), Co(II), Fe(II, III), Cu(II) in aqueous solutions close to the conditions of their extraction isolation and separation. It is shown that platinum metal ions form stable neutral and cationic complexes with both 2-AP and 4-AP that can be isolated from aqueous solutions. The tendency to form cationic complexes diminishes in the order Pd(II) > Pt(II) > Pt(IV) and 4-AP > 2-AP. With the exception of Cu(II), ions of 3 d -elements do not form stable complexes under these conditions. Cu(II) forms complexes with 2(4)-AP that are subject to hydrolysis when isolated from aqueous solutions. Features of 2(4)-AP when interacting with metal ions are discussed. It is proposed that analogs of 2(4)-AP with long hydrocarbon radicals be used for the extraction concentration of platinum metals from hydrometallurgical solutions of complex composition.