Cobalt extraction from sulfate media with bis(2,4,4-trimethylpentyl)dithiophosphinic acid in the presence of electron donor additives

The paper presents data on cobalt extraction from sulfate solutions with bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HR) diluted with nonane and kerosene in the presence of electron donor additives (L). Trioctyl amine (TOA), trialkyl amine (TAA), trioctyl phosphine oxide (TOPO), trialkyl phosphine oxide (TAPO), tributyl phosphate (TBP), and n-octanol were used as additives. Using an electronic spectroscopy method, the interaction between cobalt loaded extracts (CoR2) and the additives was first studied. It was shown that, in the presence of the additives, cobalt oxidation decreased in the series TOA approximate to TOPO > TBP > n-octanol. This is due to a decrease in the HR activity in the presence of L as well as to the interaction between L and the initial cobalt complex resulting in the formation of mixed ligand complexes such as CoR2 center dot nL, where n = 1,2. Suggestions for prevention of cobalt oxidation in the organic phase containing bis(2,4,4-trimethylpentyl) dithiophosphinic acid are given. The degree of cobalt extraction decreases in the series HR + TOPO > HR approximate to HR + n-octanol >> HR + TAA. Both synergistic and antagonistic effects take place in the HR and phosphine oxides mixture, whereas only an antagonistic effect takes place in the systems containing TAA which is due to the interaction between HR and TAA. The possibility of using the HR and L mixtures for cobalt recovery from sulfate solutions (here the HR + TOPO mixture was examined for the kinetic separation of Co and Ni) and from leach liquors of oxidized nickel ores (using the extraction system based on HR and TAA) has been demonstrated. (C) 2013 Elsevier B.V. All rights reserved.