M. Grote, Ursula Hüppe, A. Kettrup
Oct 1, 1987
Citations
0
Influential Citations
12
Citations
Journal
Hydrometallurgy
Abstract
Abstract Eight systematically substituted 1,5-diphenyl formazans, dissolved separately in toluene, chloroform and dichloromethane, were investigated as liquid-liquid extractants. The size of the phenyl ring substituents in the ortho position (halogen and alkyl groups) as well as the nature of the substituent on the central carbon atom affect the stability and acidity of the formazans. Their tendency to form different isomers influences the coordination chemistry of the ligands and thus their extraction behaviour. Distribution ratios determined for platinum group metals, gold and numerous base metals reveal the selective extractability of Pd (II) from dilute hydrochloric acid. The ortho -iodo formazan is the most effective ligand due to its enhanced formazion of a 1:1 Pd (II) complex, whereas all other formazans co-ordinate as 1:2-chelates. Consequently, in the stripping step with an acidified solution of thiourea, the rate of ligand substitution is also comparatively faster in the case of the 1:1-chelate. An effective separation of Pd (II) from an excess of Pt (IV) can be achieved by the iodo formazan.