Equilibria:
Fe(III), Cd (II) and Zn (II) are known to be extracted by high molecular weight amines from hydrochloric acid medium. The relevant equilibria steps for extraction by a tertiary amine or a quarternary ammonium salt are given below:
Fea3+ + 4 Cl-a ↔ FeCl-4
R3No +HCla ↔ R3NH+Cl-o
R3NH+Cl-o + FeCl-4a ↔ R3NH+FeCl-4o + Cl-a
Likewise, in quaternary ammonium salt, the extraction will follow the step:
R3R´N+Cl-o + FeCl-4 ↔ R R´N+. FeCl-4o + Cl -a
The extraction equilibria steps for Zn(II) and Cd(II) chlorocomplexes will be as follows:
Zn2+a+4Cl-a↔ ZnCl2-4a
2 R3NH+Clo- + ZnCl 2-4a ↔ (R3NH+)2.ZnCl2-4o +2Cl-a
2 R3R'N+Clo- + ZnCl 2-4a ↔ (R3R'N+)2.ZnCl2-4o +2Cl-a
Cd 2+a +4Cl-a↔ CdCl2-4a
2 R3NH+Clo- + CdCl 2-4a ↔ (R3NH+)2.CdCl2-4o +2Cl-a
2 R3R'N+Clo- + CdCl 2-4a ↔ (RRN+)2.CdCl2-4o +2Cl-a
Likewise, the nitrate and sulphate complexes of different metals are extracted from the corresponding mineral acids.